CA2502801A1 - Correction for differences between downlink and uplink channel responses - Google Patents
Correction for differences between downlink and uplink channel responses Download PDFInfo
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- CA2502801A1 CA2502801A1 CA002502801A CA2502801A CA2502801A1 CA 2502801 A1 CA2502801 A1 CA 2502801A1 CA 002502801 A CA002502801 A CA 002502801A CA 2502801 A CA2502801 A CA 2502801A CA 2502801 A1 CA2502801 A1 CA 2502801A1
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Abstract
In one embodiment, pilots are transmitted on the downlink and uplink channel s and used to derive estimates of the downlink and uplink channel responses, respectively. Two sets of correction factors are then determined based on th e estimates of the downlink and uplink channel responses. A calibrated downlin k channel is formed by using a first set of correction factors for the downlin k channel, and a calibrated uplink channel is formed by using a second set of correction factors for the uplink channel. The first and second sets of correction factors may be determined using a matrix-ratio computation or a minimum mean square error (MMSE) computation. The calibration may be perform ed in real-time based on over-the-air transmission.
Description
CHANNEL CALIBRATION FOR A TIME DIVISION DUPLEXED
COMMUNICATION SYSTEM
Claim of Priority under 35 U.S.C. ~119 (0001] This application claims the benefit of U.S. Provisional Application Serial No.
60/421,462, entitled, "Channel Calibration for a Time Division Duplexed Communication System," and U.S. Provisional Application Serial No. 60/421,309, entitled, "MIMO WLAN System," both of which are filed on October 25, 2002, assigned to the assignee of the present application, and incorporated herein by reference.
BACKGROUND
Field [0002] The present invention relates generally to communication, and more specifically to techniques for calibrating downlink and uplink channel responses in a time division duplexed (TDD) communication system.
Background [0003] In a wireless communication system, data transmission between an access point and a user terminal occurs over a wireless channel. Depending on the system design, the same or different frequency bands may be used for the downlink and uplink.
The downlink (or forward link) refers to transmission from the access point to the user terminal, and the uplink (or reverse link) refers to transmission from the user terminal to the access point. If two frequency bands are available, then the downlink and uplink may be transmitted on separate frequency bands using frequency division duplexing (FDD). If only one frequency band is available, then the downlink and uplink may share the same frequency band using time division duplexing (TDD).
COMMUNICATION SYSTEM
Claim of Priority under 35 U.S.C. ~119 (0001] This application claims the benefit of U.S. Provisional Application Serial No.
60/421,462, entitled, "Channel Calibration for a Time Division Duplexed Communication System," and U.S. Provisional Application Serial No. 60/421,309, entitled, "MIMO WLAN System," both of which are filed on October 25, 2002, assigned to the assignee of the present application, and incorporated herein by reference.
BACKGROUND
Field [0002] The present invention relates generally to communication, and more specifically to techniques for calibrating downlink and uplink channel responses in a time division duplexed (TDD) communication system.
Background [0003] In a wireless communication system, data transmission between an access point and a user terminal occurs over a wireless channel. Depending on the system design, the same or different frequency bands may be used for the downlink and uplink.
The downlink (or forward link) refers to transmission from the access point to the user terminal, and the uplink (or reverse link) refers to transmission from the user terminal to the access point. If two frequency bands are available, then the downlink and uplink may be transmitted on separate frequency bands using frequency division duplexing (FDD). If only one frequency band is available, then the downlink and uplink may share the same frequency band using time division duplexing (TDD).
[0004] To achieve high performance, it is often necessary to know the frequency response of the wireless channel. For example, the response of the downlink channel may be needed by the access point to perform spatial processing (described below) for downlink data transmission to the user terminal. The downlink channel response may be estimated by the user terminal based on a pilot transmitted by the access point. The user terminal may then send the channel estimate back to the access point for its use.
For this channel estimation scheme, a pilot needs to be transmitted on the downlink and additional delays and resources are incurred to send the channel estimate back to the access point.
For this channel estimation scheme, a pilot needs to be transmitted on the downlink and additional delays and resources are incurred to send the channel estimate back to the access point.
[0005] For a TDD system with a shared frequency band, the downlink and uplink channel responses may be assumed to be reciprocal of one another. That is, if H
represents a channel response matrix from antenna array A to antenna array B, then a reciprocal channel implies that the coupling from array B to array A is given by HT, where MT denotes the transpose of matrix M . Thus, for a TDD system, the channel response for one link may be estimated based on a pilot sent on the other link. For example, the uplink channel response may be estimated based on an uplink pilot, and the transpose of the uplink channel response estimate may be used as an estimate of the downlink channel response.
represents a channel response matrix from antenna array A to antenna array B, then a reciprocal channel implies that the coupling from array B to array A is given by HT, where MT denotes the transpose of matrix M . Thus, for a TDD system, the channel response for one link may be estimated based on a pilot sent on the other link. For example, the uplink channel response may be estimated based on an uplink pilot, and the transpose of the uplink channel response estimate may be used as an estimate of the downlink channel response.
[0006] However, the frequency responses of the transmit and receive chains at the access point are typically different from the frequency responses of the transmit and receive chains at the user terminal. In particular, the frequency responses of the transmit/receive chains used for uplink transmission may be different from the frequency responses of the transmit/receive chains used for downlink transmission. The "effective" downlink channel response (i.e., including the transmit/receive chains) would then be different from the reciprocal of the effective uplink channel response due to differences in the transmit/receive chains (i.e., the effective channel responses are not reciprocal). If the reciprocal of the channel response estimate obtained for one link is used for spatial processing on the other link, then any difference in the frequency responses of the transmit/receive chains would represent error that, if not determined and accounted for, may degrade performance.
[0007] There is, therefore, a need in the art for techniques to calibrate the downlink and uplink channels in a TDD communication system.
SUMMARY
SUMMARY
[0008] Techniques are provided herein to calibrate the downlink and uplink channels to account for differences in the frequency responses of the transmit and receive chains at the access point and user terminal. After calibration, an estimate of the channel response obtained for one link may be used to obtain an estimate of the channel response for the other link. This can then simplify the channel estimation and spatial processing.
[0009] In one embodiment, a method is provided for calibrating the downlink and uplink channels in a wireless TDD multiple-input multiple-output (MIMO) communication system. In accordance with the method, a pilot is transmitted on the uplink channel and used to derive an estimate of the uplink channel response.
A pilot is also transmitted on the downlink channel and used to derive an estimate of the downlink channel response. Two sets of correction factors are then determined based on the estimates of the downlink and uplink channel responses. A calibrated downlink channel is formed by using a first set of correction factors for the downlink channel, and a calibrated uplink channel is formed by using a second set of correction factors for the uplink channel. The appropriate correction factors will be used at the respective transmitter for the downlink and uplink channels. The responses of the calibrated downlink and uplink channels are approximately reciprocal due to the two sets of correction factors. The first and second sets of correction factors may be determined using a matrix-ratio computation or a minimum mean square error (MMSE) computation, as described below.
A pilot is also transmitted on the downlink channel and used to derive an estimate of the downlink channel response. Two sets of correction factors are then determined based on the estimates of the downlink and uplink channel responses. A calibrated downlink channel is formed by using a first set of correction factors for the downlink channel, and a calibrated uplink channel is formed by using a second set of correction factors for the uplink channel. The appropriate correction factors will be used at the respective transmitter for the downlink and uplink channels. The responses of the calibrated downlink and uplink channels are approximately reciprocal due to the two sets of correction factors. The first and second sets of correction factors may be determined using a matrix-ratio computation or a minimum mean square error (MMSE) computation, as described below.
[0010] The calibration may be performed in real-time based on over-the-air transmission. Each user terminal in the system may derive the second set of correction factors for its own use. The first set of correction factors for the access point may be derived by multiple user terminals. For an orthogonal frequency division multiplexing (OFDM) system, the calibration may be performed for a first set of subbands to obtain two sets of correction factors for each subband in the set. Correction factors for other "uncalibrated" subbands may be interpolated based on the correction factors obtained for the "calibrated" subbands.
[0011] Various aspects and embodiments of the invention are described in further detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:
[0013] FIG. 1 shows the transmit and receive chains at an access point and a user terminal in a MIMO system;
[0014] FIG. 2 illustrates the application of correction factors to account for differences in the transmitlreceive chains at the access point and user terminal;
[0015] FIG. 3 shows a process for calibrating the downlink and uplink channel responses in a TDD MIMO-OFDM system;
[0016] FIG. 4 shows a process for deriving estimates of the correction vectors from the downlink and uplink channel response estimates;
[0017] FIG. 5 is a block diagram of the access point and user terminal; and [0018] FIG. 6 is a block diagram of a TX spatial processor.
DETAILED DESCRIPTION
DETAILED DESCRIPTION
[0019] The calibration techniques described herein may be used for various wireless communication systems. Moreover, these techniques may be used for single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, single-input multiple-output (SIMO) systems, and multiple-input multiple-output (MIMO) systems.
[0020] A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT
transmit and NR receive antennas may be decomposed into NS independent channels, with NS <_ min{NT, NR } . Each of the NS independent channels is also referred to as a spatial subchannel or an eigenmode of the MIMO channel and corresponds to a dimension.
The M1M0 system can provide improved performance (e.g., increased transmission capacity) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. This typically requires an accurate estimate of the channel response between the transmitter and receiver.
transmit and NR receive antennas may be decomposed into NS independent channels, with NS <_ min{NT, NR } . Each of the NS independent channels is also referred to as a spatial subchannel or an eigenmode of the MIMO channel and corresponds to a dimension.
The M1M0 system can provide improved performance (e.g., increased transmission capacity) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. This typically requires an accurate estimate of the channel response between the transmitter and receiver.
[0021] FIG. 1 shows a block diagram of the transmit and receive chains at an access point 102 and a user terminal 104 in a MIMO system. For this system, the downlink and uplink share the same frequency band in a time division duplexed manner.
[0022] For the downlink, at access point 102, symbols (denoted by a "transmit"
vector x~, ) are processed by a transmit chain (TMTR) 114 and transmitted from Nn~
antennas 116 over a wireless channel. At user terminal 104, the downlink signals are received by Nun antennas 152 and processed by a receive chain (RCVR) 154 to provide received symbols (denoted by a "receive" vector r~, ). The processing by transmit chain typically includes digital-to-analog conversion, amplification, filtering, frequency upconversion, and so on. The processing by receive chain 154 typically includes frequency downconversion, amplification, filtering, analog-to-digital conversion, and so on.
vector x~, ) are processed by a transmit chain (TMTR) 114 and transmitted from Nn~
antennas 116 over a wireless channel. At user terminal 104, the downlink signals are received by Nun antennas 152 and processed by a receive chain (RCVR) 154 to provide received symbols (denoted by a "receive" vector r~, ). The processing by transmit chain typically includes digital-to-analog conversion, amplification, filtering, frequency upconversion, and so on. The processing by receive chain 154 typically includes frequency downconversion, amplification, filtering, analog-to-digital conversion, and so on.
[0023] For the uplink, at user terminal 104, symbols (denoted by transmit vector x"p ) are processed by a transmit chain 164 and transmitted from Nun antennas 152 over the wireless channel. At access point 102, the uplink signals are received by N~~, antennas 116 and processed by a receive chain 124 to provide received symbols (denoted by receive vector r"P ).
[0024] For the downlink, the receive vector at the user terminal may be expressed as:
Eq (1) where xd" is the transmit vector with N~p entries for the symbols transmitted from the N~~, antennas at the access point;
rdn is the receive vector with Nun entries for the symbols received on the Nun antennas at the user terminal;
TaP is an Nay x NaP diagonal matrix with entries for the complex gains associated with the transmit chain for the N~p antennas at the access point;
R"~ is an Nun x Nut diagonal matrix with entries for the complex gains associated with the receive chain for the Nun antennas at the user terminal; and H is an Nun x N~,p channel response matrix for the downlink.
The responses of the transmit/receive chains and the wireless channel are typically a function of frequency. For simplicity, a flat-fading channel (i.e., with a flat frequency response) is assumed.
Eq (1) where xd" is the transmit vector with N~p entries for the symbols transmitted from the N~~, antennas at the access point;
rdn is the receive vector with Nun entries for the symbols received on the Nun antennas at the user terminal;
TaP is an Nay x NaP diagonal matrix with entries for the complex gains associated with the transmit chain for the N~p antennas at the access point;
R"~ is an Nun x Nut diagonal matrix with entries for the complex gains associated with the receive chain for the Nun antennas at the user terminal; and H is an Nun x N~,p channel response matrix for the downlink.
The responses of the transmit/receive chains and the wireless channel are typically a function of frequency. For simplicity, a flat-fading channel (i.e., with a flat frequency response) is assumed.
[0025] For the uplink, the receive vector at the access point may be expressed as:
T
ruP = R~PH _Tu~?~~P ~ Eq (2) where xUp is the transmit vector for the symbols transmitted from the Nut antennas at the user terminal;
r"p is the receive vector for the symbols received on the NaP antennas at the access point;
Tnt is an Nut ~e N~,t diagonal matrix with entries for the complex gains associated with the transmit chain for the Nut antennas at the user terminal;
Rap is an Nat, x N~~, diagonal matrix with entries for the complex gains associated with the receive chain for the Nnp antennas at the access point;
and HT is an Nap x Nut channel response matrix for the uplink.
T
ruP = R~PH _Tu~?~~P ~ Eq (2) where xUp is the transmit vector for the symbols transmitted from the Nut antennas at the user terminal;
r"p is the receive vector for the symbols received on the NaP antennas at the access point;
Tnt is an Nut ~e N~,t diagonal matrix with entries for the complex gains associated with the transmit chain for the Nut antennas at the user terminal;
Rap is an Nat, x N~~, diagonal matrix with entries for the complex gains associated with the receive chain for the Nnp antennas at the access point;
and HT is an Nap x Nut channel response matrix for the uplink.
[0026] For a TDD system, since the downlink and uplink share the same frequency band, a high degree of correlation normally exists between the downlink and uplink channel responses. Thus, the downlink and uplink channel response matrices may be assumed to be reciprocal (i.e., transposes) of each other and denoted H and HT
, respectively, as shown in equations (1) and (2). However, the responses of the transmit/receive chains at the access point are typically not equal to the responses of the transmit/receive chains at the user terminal. The differences then result in the following inequality Rap HT T~t ~ (Rnt HTap )T .
, respectively, as shown in equations (1) and (2). However, the responses of the transmit/receive chains at the access point are typically not equal to the responses of the transmit/receive chains at the user terminal. The differences then result in the following inequality Rap HT T~t ~ (Rnt HTap )T .
[0027] From equations (1) and (2), the "effective" downlink and uplink channel responses, Hue, and Hup , which include the responses of the applicable transmit and receive chains, may be expressed as:
Hdn = Rut HTap and Hnp = Rap HT TUt . Eq (3) Combining the two equations in equation set (3), the following relationship may be obtained:
Rn~ Hdn Tap = (Rap Hup Tur )T = Tub Hup Rap . Eq (4) Rearranging equation (4), the following is obtained:
T _ 1 1 _ 1 Hup - Tut Rut Hdn Tap Rap - Kut Hdn ~ap or Hnp = (Knt ~dn~ap)T ~ Eq ($) where K"~ = T;,~ R~~ and Kap = TaPRap . Equation (5) may also be expressed as:
Hnp~nt = (HdnKap)T ~ Eq (6) [0028] The left-hand side of equation (6) represents the calibrated channel response on the uplink, and the right-hand side represents the transpose of the calibrated channel response on the downlink. The application of the diagonal matrices, K"~ and Kap , to the effective downlink and uplink channel responses, as shown in equation (6), allows the calibrated channel responses for the downlink and uplink to be expressed as transposes of each other. The (N~p xN~,~,) diagonal matrix I~ap for the access point is the ratio of the receive chain response Rap to the transmit chain response Tap (i.e., Kap = T ap ), where the ratio is taken element-by-element. Similarly, the (Nun x Nu~ ) -ap diagonal matrix K"t for the user terminal is the ratio of the receive chain response R"
to the transmit chain response T"~ .
Hdn = Rut HTap and Hnp = Rap HT TUt . Eq (3) Combining the two equations in equation set (3), the following relationship may be obtained:
Rn~ Hdn Tap = (Rap Hup Tur )T = Tub Hup Rap . Eq (4) Rearranging equation (4), the following is obtained:
T _ 1 1 _ 1 Hup - Tut Rut Hdn Tap Rap - Kut Hdn ~ap or Hnp = (Knt ~dn~ap)T ~ Eq ($) where K"~ = T;,~ R~~ and Kap = TaPRap . Equation (5) may also be expressed as:
Hnp~nt = (HdnKap)T ~ Eq (6) [0028] The left-hand side of equation (6) represents the calibrated channel response on the uplink, and the right-hand side represents the transpose of the calibrated channel response on the downlink. The application of the diagonal matrices, K"~ and Kap , to the effective downlink and uplink channel responses, as shown in equation (6), allows the calibrated channel responses for the downlink and uplink to be expressed as transposes of each other. The (N~p xN~,~,) diagonal matrix I~ap for the access point is the ratio of the receive chain response Rap to the transmit chain response Tap (i.e., Kap = T ap ), where the ratio is taken element-by-element. Similarly, the (Nun x Nu~ ) -ap diagonal matrix K"t for the user terminal is the ratio of the receive chain response R"
to the transmit chain response T"~ .
[0029] The matrices Kap and I~ut include values that can account for differences in the transmitlreceive chains at the access point and user terminal. This would then allow the channel response for one link to be expressed by the channel response for the other link, as shown in equation (6).
[0030] Calibration may be performed to determine the matrices Kap and I~"~ .
Typically, the true channel response H and the transmit/receive chain responses are not known nor can they be exactly or easily ascertained. Instead, the effective downlink and uplink channel responses, Hda and Hup , may be estimated based on pilots sent on the downlink and uplink, respectively, as described below. Estimates of the matrices Kap and KU~ , which are referred to as correction matrices Kap and K~~ , may then be derived based on the downlink and uplink channel response estimates, Hdn and I3"p , as described below. The matrices I~ap and Ku~ include correction factors that can account for differences in the transmit/receive chains at the access point and user terminal.
Typically, the true channel response H and the transmit/receive chain responses are not known nor can they be exactly or easily ascertained. Instead, the effective downlink and uplink channel responses, Hda and Hup , may be estimated based on pilots sent on the downlink and uplink, respectively, as described below. Estimates of the matrices Kap and KU~ , which are referred to as correction matrices Kap and K~~ , may then be derived based on the downlink and uplink channel response estimates, Hdn and I3"p , as described below. The matrices I~ap and Ku~ include correction factors that can account for differences in the transmit/receive chains at the access point and user terminal.
[0031] FIG. 2 illustrates the application of the correction matrices I~aP and Ku~ to account for differences in the transmit/receive chains at the access point and user terminal. On the downlink, the transmit vector x~, is first multiplied with the matrix I~ap by a unit 112. The subsequent processing by transmit chain 114 and receive chain 154 for the downlink is the same as shown in FIG. 1. Similarly, on the uplink, the transmit vector x"P is first multiplied with the matrix K"t by a unit 162.
Again, the subsequent processing by transmit chain 164 and receive chain 124 for the uplink is the same as shown in FIG. 1.
Again, the subsequent processing by transmit chain 164 and receive chain 124 for the uplink is the same as shown in FIG. 1.
[0032] The "calibrated" downlink and uplink channel responses observed by the user terminal and access point, respectively, may then be expressed as:
H~~, = H~ KaP and H~~p = H"P I~"t , Eq (7) where H ~ and H~up are estimates of the "true" calibrated channel response expressions in equation (6). Combining the two equations in equation set (7) using the expression in equation (6), it can be shown that H~"p = H ~ . The accuracy of the relationship H~"P = H a" is dependent on the accuracy of the matrices Kap and I~"~ , which in turn is typically dependent. on the quality of the downlink and uplink channel response estimates, H~ and H"p .
H~~, = H~ KaP and H~~p = H"P I~"t , Eq (7) where H ~ and H~up are estimates of the "true" calibrated channel response expressions in equation (6). Combining the two equations in equation set (7) using the expression in equation (6), it can be shown that H~"p = H ~ . The accuracy of the relationship H~"P = H a" is dependent on the accuracy of the matrices Kap and I~"~ , which in turn is typically dependent. on the quality of the downlink and uplink channel response estimates, H~ and H"p .
[0033] As shown above, calibration may be performed in a TDD system to determine the differences in the responses of the transmitlreceive chains at the access point and user terminal, and to account for the differences. Once the transmit/receive chains have been calibrated, a calibrated channel response estimate obtained for one link (e.g., H~an ) may be used to determine an estimate of the calibrated channel response for the other link (e.g., H~"P ).
[0034] The calibration techniques described herein may also be used for wireless communication systems that employ OFDM. OFDM effectively partitions the overall system bandwidth into a number of (NF) orthogonal subbands, which are also referred to as frequency bins or subchannels. With OFDM, each subband is associated with a respective subcarrier upon which data may be modulated. For a MIMO system that utilizes OFDM (i.e., a MIMO-OFDM system), each subband of each eigenmode may be viewed as an independent transmission channel.
[0035] The calibration may be performed in various manners. For clarity, a specific calibration scheme is described below for a TDD MIMO-OFDM system. For this system, each subband of the wireless link may be assumed to be reciprocal.
[0036] FIG. 3 is a flow diagram of an embodiment of a process 300 for calibrating the downlink and uplink channel responses in the TDD MIMO-OFDM system. Initially, the user terminal acquires the timing and frequency of the access point using acquisition procedures defined for the system (step 310). The user terminal may then send a message to initiate calibration with the access point, or the calibration may be initiated by the access point. The calibration may be performed in parallel with registration/authentication of the user terminal by the access point (e.g., during call setup) and may also be performed whenever warranted.
[0037] The calibration may be performed for all subbands that may be used for data transmission (which are referred to as the "data" subbands). Subbands not used for data transmission (e.g., guard subbands) typically do not need to be calibrated.
However, since the frequency responses of the transmit/receive chains at the access point and user terminal are typically flat over most of the band of interest, and since adjacent subbands are likely to be correlated, the calibration may be performed for only a subset of the data subbands. If fewer than all data subbands are calibrated, then the subbands to be calibrated (which are referred to as the "designated" subbands) may be signaled to the access point (e.g., in the message sent to initiate the calibration).
However, since the frequency responses of the transmit/receive chains at the access point and user terminal are typically flat over most of the band of interest, and since adjacent subbands are likely to be correlated, the calibration may be performed for only a subset of the data subbands. If fewer than all data subbands are calibrated, then the subbands to be calibrated (which are referred to as the "designated" subbands) may be signaled to the access point (e.g., in the message sent to initiate the calibration).
[0038] For the calibration, the user terminal transmits a MIMO pilot on the designated subbands to the access point (step 312). The generation of the MIMO pilot is described in detail below. The duration of the uplink MIMO pilot transmission may be dependent on the number of designated subbands. For example, 8 OFDM symbols may be sufficient if calibration is performed for four subbands, and more (e.g., 20) OFDM
symbols may be needed for more subbands. The total transmit power is typically fixed, so if the MIMO pilot is transmitted on a small number of subbands, then higher amounts of transmit power may be used for each of these subbands and the SNR for each subband is high. Conversely, if the MIMO pilot is transmitted on a large number of subbands then smaller amounts of transmit power may be used for each subband and the SNR for each subband is worse. If the SNR of each subband is not sufficiently high, then more OFDM symbols may be sent for the MIMO pilot and integrated at the receiver to obtain a higher overall SNR for the subband.
symbols may be needed for more subbands. The total transmit power is typically fixed, so if the MIMO pilot is transmitted on a small number of subbands, then higher amounts of transmit power may be used for each of these subbands and the SNR for each subband is high. Conversely, if the MIMO pilot is transmitted on a large number of subbands then smaller amounts of transmit power may be used for each subband and the SNR for each subband is worse. If the SNR of each subband is not sufficiently high, then more OFDM symbols may be sent for the MIMO pilot and integrated at the receiver to obtain a higher overall SNR for the subband.
[0039] The access point receives the uplink MIMO pilot and derives an estimate of the uplink channel response, Hup (k) , for each of the designated subbands, where k represents the subband index. Channel estimation based on the MIMO pilot is described below. The uplink channel response estimates are quantized and sent to the user terminal (step 314). The entries in each matrix HuP (k) are complex channel gains between the Nun transmit and Nap receive antennas for the uplink for the k-th subband.
The channel gains for all matrices may be scaled by a particular scaling factor, which is common across all designated subbands, to obtain the desired dynamic range.
For example, the channel gains in each matrix HuP (k) may be inversely scaled by the largest channel gain for all matrices H"P (k) for the designated subbands so that the largest channel gain is one in magnitude. Since the goal of the calibration is to normalize the gain/phase difference between the downlink and uplink, the absolute channel gains are not important. If 12-bit complex values (i.e., with 12-bit inphase (I) and 12-bit quadrature (Q) components) are used for the channel gains, then the downlink channel response estimates may be sent to the user terminal in 3 - Nun ~ Nap ~ NSF bytes, where "3" is for the 24 total bits used to represent the I and Q
components and NSb is the number of designated subbands.
The channel gains for all matrices may be scaled by a particular scaling factor, which is common across all designated subbands, to obtain the desired dynamic range.
For example, the channel gains in each matrix HuP (k) may be inversely scaled by the largest channel gain for all matrices H"P (k) for the designated subbands so that the largest channel gain is one in magnitude. Since the goal of the calibration is to normalize the gain/phase difference between the downlink and uplink, the absolute channel gains are not important. If 12-bit complex values (i.e., with 12-bit inphase (I) and 12-bit quadrature (Q) components) are used for the channel gains, then the downlink channel response estimates may be sent to the user terminal in 3 - Nun ~ Nap ~ NSF bytes, where "3" is for the 24 total bits used to represent the I and Q
components and NSb is the number of designated subbands.
[0040] The user terminal also receives a downlink MIMO pilot transmitted by the access point (step 316) and derives an estimate of the downlink channel response, Iian (k) , for each of the designated subbands based on the received pilot (step 318). The user terminal then determines correction factors, KaP (k) and K~~ (k) , for each of the designated subbands based on the uplink and downlink channel response estimates, H~P (k) and I3dn (k) (step 320).
[0041] For the derivation of the correction factors, the downlink and uplink channel responses for each subband are assumed to be reciprocal, with gain/phase corrections to account for the differences in the transmit/receive chains at the access point and user terminal, as follows:
HUP (k)I~u, (k) _ (H~, (k)KaP (k))T , for k E K , Eq (8) where K represents a set with all data subbands. Since only estimates of the effective downlink and uplink channel responses are available for the designated subbands during calibration, equation (8) may be rewritten as:
HuP (k)~u~ (k) _ (Han (k)Kap (k))T ~ for k E K' ~ Eq (9) where K' represents a set with all designated subbands. A correction vector k"t (k) may be defined to include only the Nut diagonal elements of Ku~ (k) .
Similarly, a correction vector k~P(k) may be defined to include only the Nay diagonal elements of I~ap (k) .
HUP (k)I~u, (k) _ (H~, (k)KaP (k))T , for k E K , Eq (8) where K represents a set with all data subbands. Since only estimates of the effective downlink and uplink channel responses are available for the designated subbands during calibration, equation (8) may be rewritten as:
HuP (k)~u~ (k) _ (Han (k)Kap (k))T ~ for k E K' ~ Eq (9) where K' represents a set with all designated subbands. A correction vector k"t (k) may be defined to include only the Nut diagonal elements of Ku~ (k) .
Similarly, a correction vector k~P(k) may be defined to include only the Nay diagonal elements of I~ap (k) .
[0042] The correction factors KaP(k) and K"~(k) may be derived from the channel estimates Hen (k) and H"p (k) in various manners, including by a matrix-ratio computation and a minimum mean square error (MMSE) computation. Both of these computation methods are described in further detail below. Qther computation methods may also be used, and this is within the scope of the invention.
A. Matrix-Ratio Computation [0043] FIG. 4 is a flow diagram of an embodiment of a process 320a for deriving the correction vectors kut (k) and kaP (k) from the downlink and uplink channel response estimates I3~p (k) and I3~ (k) using matrix-ratio computation. Process 320a may be used for step 320 in FIG. 3.
A. Matrix-Ratio Computation [0043] FIG. 4 is a flow diagram of an embodiment of a process 320a for deriving the correction vectors kut (k) and kaP (k) from the downlink and uplink channel response estimates I3~p (k) and I3~ (k) using matrix-ratio computation. Process 320a may be used for step 320 in FIG. 3.
[0044] Initially, an (Nun x N~~, ) matrix C(k) is computed for each designated subband (step 412), as follows:
.. T
C(k) = H°P (k) , for k E K° , Eq (10) Hdn (k) where the ratio is taken element-by-element. Each element of C(k) may thus be computed as:
e. .(k)=~~°P'''(k) for i={1 ... N and _., ~ u, } j = {1 ... N~~, } , Eq (11) lzd~ r, i (k) where hUP;, J (k) and hd~ ~,~ (k) are the ( i, j )-th (row, column) element of H P (k) and Ha" (k) , respectively, and c;,~ (k) is the ( i, j )-th element of C(k) .
.. T
C(k) = H°P (k) , for k E K° , Eq (10) Hdn (k) where the ratio is taken element-by-element. Each element of C(k) may thus be computed as:
e. .(k)=~~°P'''(k) for i={1 ... N and _., ~ u, } j = {1 ... N~~, } , Eq (11) lzd~ r, i (k) where hUP;, J (k) and hd~ ~,~ (k) are the ( i, j )-th (row, column) element of H P (k) and Ha" (k) , respectively, and c;,~ (k) is the ( i, j )-th element of C(k) .
[0045] In an embodiment, the correction vector for the access point, k aP (k) , is defined to be equal to the mean of the normalized rows of C(k) and is derived by the steps in block 420. Each row of C(k) is first normalized by scaling each of the NaP
elements in the row with the first element in the row (step 422). Thus, if c; (k) _ [c~,l (k) ... Ci N"n (k)] is the i-th row of C(k) , then the normalized row c; (k) may be expressed as:
c; (k) _ [c;,l (k) l c;,l (k) ... c;,~ (k) l c;,l (k) ... ct,N"P (k) l c;,l (k)] . Eq (12) The mean of the normalized rows is then determined as the sum of the Nur normalized rows divided by N"r (step 424). The correction vector kap (k) is set equal to this mean (step 426), which rnay be expressed as:
1 Nnr kaP(k)= N ~cl(k) , for kE K'. Eq (13) ur a=i Because of the normalization, the first element of kap (k) is unity.
elements in the row with the first element in the row (step 422). Thus, if c; (k) _ [c~,l (k) ... Ci N"n (k)] is the i-th row of C(k) , then the normalized row c; (k) may be expressed as:
c; (k) _ [c;,l (k) l c;,l (k) ... c;,~ (k) l c;,l (k) ... ct,N"P (k) l c;,l (k)] . Eq (12) The mean of the normalized rows is then determined as the sum of the Nur normalized rows divided by N"r (step 424). The correction vector kap (k) is set equal to this mean (step 426), which rnay be expressed as:
1 Nnr kaP(k)= N ~cl(k) , for kE K'. Eq (13) ur a=i Because of the normalization, the first element of kap (k) is unity.
[0046] In an embodiment, the correction vector for the user terminal, k"r (k) , is defined to be equal to the mean of the inverses of the normalized columns of C(k) and is derived by the steps in block 430. The j-th column of C(k) is first normalized by scaling each element in the column with the j-th element of the vector k aP
(k) , which is denoted as K~P,~,~ (k) (step 432). Thus, if c~ (k) _ [c,,~ (k) ... cN"r,i (k)]T is the j-th column of C(k) , then the normalized column c~ (k) may be expressed as:
c~ (k) _ [cl,~ (k) l K~P, i,i (k) ... c;,i (k) l KaP.i. i (k) ... cN"r,i (k) l Kap, i,i (k)~T . Eq (14) The mean of the inverses of the normalized columns is then determined as the sum of the inverses of the N~,P normalized columns divided by N~,p (step 434). The correction vector kur (k) is set equal to this mean (step 436), which may be expressed as:
1 N"° 1 k ur (k) _ ~ , for k E K , Eq (15) Nw ;_, ~~ (k) where the inversion of the normalized columns, c~ (k) , is performed element-wise.
B. MMSE Computation [0047] For the MMSE computation, the correction factors KaP (k) and KU~ (k) are derived from the downlink and uplink channel response estimates H~, (k) and H~P (k) such that the mean square error (MSE) between the calibrated downlink channel response and the calibrated uplink channel response is minimized. This condition may be expressed as:
min I(Ha" (k)Kap (k))T - IiuP (k)K"~ (k)I z , for k ~ K , Eq (16) which may also be written as:
z min ~K~P (k)Ha (k) - IiuP (k)I~U~ (k)I , for k E K , ~T
where I~ap (k) = Kap (k) since Kap (k) is a diagonal matrix.
(k) , which is denoted as K~P,~,~ (k) (step 432). Thus, if c~ (k) _ [c,,~ (k) ... cN"r,i (k)]T is the j-th column of C(k) , then the normalized column c~ (k) may be expressed as:
c~ (k) _ [cl,~ (k) l K~P, i,i (k) ... c;,i (k) l KaP.i. i (k) ... cN"r,i (k) l Kap, i,i (k)~T . Eq (14) The mean of the inverses of the normalized columns is then determined as the sum of the inverses of the N~,P normalized columns divided by N~,p (step 434). The correction vector kur (k) is set equal to this mean (step 436), which may be expressed as:
1 N"° 1 k ur (k) _ ~ , for k E K , Eq (15) Nw ;_, ~~ (k) where the inversion of the normalized columns, c~ (k) , is performed element-wise.
B. MMSE Computation [0047] For the MMSE computation, the correction factors KaP (k) and KU~ (k) are derived from the downlink and uplink channel response estimates H~, (k) and H~P (k) such that the mean square error (MSE) between the calibrated downlink channel response and the calibrated uplink channel response is minimized. This condition may be expressed as:
min I(Ha" (k)Kap (k))T - IiuP (k)K"~ (k)I z , for k ~ K , Eq (16) which may also be written as:
z min ~K~P (k)Ha (k) - IiuP (k)I~U~ (k)I , for k E K , ~T
where I~ap (k) = Kap (k) since Kap (k) is a diagonal matrix.
[0048] Equation (16) is subject to the constraint that the lead element of K~p(k) is set equal to unity (i.e., KaP,o,o (k) =1 ). Without this constraint, the trivial solution would be obtained with all elements of the matrices I~ap (k) and K"t (k) set equal to zero. In equation (16), a matrix Y(k) is first obtained as Y(k) = K~p (k)H n (k) - HuP
(k)K", (k) .
The square of the absolute value is next obtained for each of the N~,P ~ N~,~
entries of the matrix Y(k) . The mean square error (or the square error, since a divide by Nnp ~ N"~ is omitted) is then equal to the sum of all N~,P ~ Nun squared values.
(k)K", (k) .
The square of the absolute value is next obtained for each of the N~,P ~ N~,~
entries of the matrix Y(k) . The mean square error (or the square error, since a divide by Nnp ~ N"~ is omitted) is then equal to the sum of all N~,P ~ Nun squared values.
[0049] The MMSE computation is performed for each designated subband to obtain the correction factors K~P(k) and Kut(k) for that subband. The MMSE computation for one subband is described below. For simplicity, the subband index, k, is omitted in the following description. Also for simplicity, the elements of the downlink channel .. T
response estimate Hd" are denoted as {a;~ } , the elements of the uplink channel response estimate HuP are denoted as {b;~ } , the diagonal elements of the matrix K~P
are denoted as {u; }, and the diagonal elements of the matrix K"t are denoted as {v~ }, where i={1 ... N~~,} and j={1 ... N"~}.
response estimate Hd" are denoted as {a;~ } , the elements of the uplink channel response estimate HuP are denoted as {b;~ } , the diagonal elements of the matrix K~P
are denoted as {u; }, and the diagonal elements of the matrix K"t are denoted as {v~ }, where i={1 ... N~~,} and j={1 ... N"~}.
[0050] The mean square error may be rewritten from equation (16), as follows:
Nur NnP
MSE=~~~ a~iui -brv; ~Z Eq (1~) f=I f=I
again subject to the constraint ul =1. The minimum mean square error may be obtained by taking the partial derivatives of equation (17) with respect to a and v and setting the partial derivatives to zero. The results of these operations are the following equation sets:
N", ~(a~~u~-btw~)~a~=0 ,foriE{2 ... Nap},and Eq(18a) Non ~(a;~u;-b~w~)-b,~=0 ,for jE{1 ... Nu~}. Eq(18b) In equation (18a), ul =1 so there is no partial derivative for this case, and the index i runs from 2 through Nap .
Nur NnP
MSE=~~~ a~iui -brv; ~Z Eq (1~) f=I f=I
again subject to the constraint ul =1. The minimum mean square error may be obtained by taking the partial derivatives of equation (17) with respect to a and v and setting the partial derivatives to zero. The results of these operations are the following equation sets:
N", ~(a~~u~-btw~)~a~=0 ,foriE{2 ... Nap},and Eq(18a) Non ~(a;~u;-b~w~)-b,~=0 ,for jE{1 ... Nu~}. Eq(18b) In equation (18a), ul =1 so there is no partial derivative for this case, and the index i runs from 2 through Nap .
[0051] The set of (N~p +Nut -1) equations in equation sets (18a) and (18b) may be more conveniently expressed in matrix form, as follows:
Ay = z , Eq (19) where r z a2~ 0 ... 0 -b21a21 ... -b2N~ra2Nr,r .
=1 0 ~ 1a3~ I2 ... ... ... ...
j=1 ... 0 ... 0 A 0 ... 0 aNn .% -bN" laNa 1 bN"rNrrraN"rNrn .%
N~r -a21bz1 ... -aNrtrlbnrsrl bil 0 ... 0 i=1 Nrrr ... ... ~ ~Ibi2I2 ~ ...
i=1 ... 0 ... 0 N
a2Nrrrb2Nrrr ... aNnrNrrrbNarNrrr ... ~IbiNrrt~2 t=1 u2 0 u3 0 a 0 y = Nnr and z =
Vl allbll V2 a12b12 n~ b*
vNnr VYlNur lNur [0052] The matrix A includes (Nap + Nt,~ -1) rows, with the first N~p -1 rows corresponding to the N~P -1 equations from equation set (18a) and the last Nun rows corresponding to the Nun equations from equation set (18b). In particular, the first row of the matrix A is generated from equation set (18a) with i = 2, the second row is generated with i = 3 , and so on. The Nap -th row of the matrix A is generated from equation set (18b) with j =1, and so on, and the last row is generated with j = N"~ . As shown above, the entries of the matrix A and the entries of the vector z may be obtained based on the entries in the matrices H~, and I3uP .
Ay = z , Eq (19) where r z a2~ 0 ... 0 -b21a21 ... -b2N~ra2Nr,r .
=1 0 ~ 1a3~ I2 ... ... ... ...
j=1 ... 0 ... 0 A 0 ... 0 aNn .% -bN" laNa 1 bN"rNrrraN"rNrn .%
N~r -a21bz1 ... -aNrtrlbnrsrl bil 0 ... 0 i=1 Nrrr ... ... ~ ~Ibi2I2 ~ ...
i=1 ... 0 ... 0 N
a2Nrrrb2Nrrr ... aNnrNrrrbNarNrrr ... ~IbiNrrt~2 t=1 u2 0 u3 0 a 0 y = Nnr and z =
Vl allbll V2 a12b12 n~ b*
vNnr VYlNur lNur [0052] The matrix A includes (Nap + Nt,~ -1) rows, with the first N~p -1 rows corresponding to the N~P -1 equations from equation set (18a) and the last Nun rows corresponding to the Nun equations from equation set (18b). In particular, the first row of the matrix A is generated from equation set (18a) with i = 2, the second row is generated with i = 3 , and so on. The Nap -th row of the matrix A is generated from equation set (18b) with j =1, and so on, and the last row is generated with j = N"~ . As shown above, the entries of the matrix A and the entries of the vector z may be obtained based on the entries in the matrices H~, and I3uP .
[0053] The correction factors are included in the vector y , which may be obtained as:
Y = A_lz . ~ Eq (20) [0054] The results of the MMSE computation are correction matrices KaP and Kut that minimize the mean square error in the calibrated downlink and uplink channel responses, as shown in equation (16). Since the matrices Kap and Ku~ are obtained based on the downlink and uplink channel response estimates, Ha" and H"p , the quality of the correction matrices Kap and K"~ are thus dependent on the quality of the channel estimates H~ and H"p . The MIMMO pilot may be averaged at the receiver to obtain more accurate estimates for H~ and Hup .
Y = A_lz . ~ Eq (20) [0054] The results of the MMSE computation are correction matrices KaP and Kut that minimize the mean square error in the calibrated downlink and uplink channel responses, as shown in equation (16). Since the matrices Kap and Ku~ are obtained based on the downlink and uplink channel response estimates, Ha" and H"p , the quality of the correction matrices Kap and K"~ are thus dependent on the quality of the channel estimates H~ and H"p . The MIMMO pilot may be averaged at the receiver to obtain more accurate estimates for H~ and Hup .
[0055] The correction matrices, KaP and K"~ , obtained based on the MMSE
computation are generally better than the correction matrices obtained based on the matrix-ratio computation, especially when some of the channel gains are small and measurement noise can greatly degrade the channel gains.
C. Post Comuutation [0056] Regardless of the particular computation method selected for use, after completion of the computation of the correction matrices, the user terminal sends to the access point the correction vectors for the access point, k ap (k) , for all designated subbands. If 12-bit complex values are used for each correction factor in kap (k) , then the correction vectors kaP (k) for all designated subbands may be sent to the access point in 3 ~ (N~p -1) ~ NS~ bytes, where "3" is for the 24 total bits used for the I and Q
components and (NaP -1) results from the first element in each vector kap (k) being equal to unity and thus not needing to be sent. If the first element is set to 29 -1= +511, then 12 dB of headroom is available (since the maximum positive 12-bit signed value is 2" -1=+2047 ), which would then allow gain mismatch of up to 12 dB
between the downlink and uplink to be accommodated by 12-bit values. If the downlink and uplink match to within 12 dB and the first element is normalized to a value of 511, then the other elements should be no greater than 511 ~ 4 = 2044 in absolute value and can be represented with 12 bits.
computation are generally better than the correction matrices obtained based on the matrix-ratio computation, especially when some of the channel gains are small and measurement noise can greatly degrade the channel gains.
C. Post Comuutation [0056] Regardless of the particular computation method selected for use, after completion of the computation of the correction matrices, the user terminal sends to the access point the correction vectors for the access point, k ap (k) , for all designated subbands. If 12-bit complex values are used for each correction factor in kap (k) , then the correction vectors kaP (k) for all designated subbands may be sent to the access point in 3 ~ (N~p -1) ~ NS~ bytes, where "3" is for the 24 total bits used for the I and Q
components and (NaP -1) results from the first element in each vector kap (k) being equal to unity and thus not needing to be sent. If the first element is set to 29 -1= +511, then 12 dB of headroom is available (since the maximum positive 12-bit signed value is 2" -1=+2047 ), which would then allow gain mismatch of up to 12 dB
between the downlink and uplink to be accommodated by 12-bit values. If the downlink and uplink match to within 12 dB and the first element is normalized to a value of 511, then the other elements should be no greater than 511 ~ 4 = 2044 in absolute value and can be represented with 12 bits.
[0057] A pair of correction vectors kap (k) and ku~ (k) is obtained for each designated subband. If the calibration is performed for fewer than all of the data subbands, then the correction factors for the "uncalibrated" subbands may be obtained by interpolating the correction factors obtained for the designated subbands. The interpolation may be performed by the access point to obtain the correction vectors kaP (k) , for k E K .
Similarly, the interpolation may be performed by the user terminal to obtain the correction vectors k ut (k) , for k E K .
Similarly, the interpolation may be performed by the user terminal to obtain the correction vectors k ut (k) , for k E K .
[0058] The access point and user terminal thereafter use their respective correction vectors kaP (k) and ku~ (k) , or the corresponding correction matrices K~p (k) and K"t (k) , for k ~ K , to scale modulation symbols prior to transmission over the wireless channel, as described below. The effective downlink channel that the user terminal sees would then be H~~, (k) = Hdo (k)I~aP (k) .
[0059] The calibration scheme described above, whereby a vector of correction factors is obtained for each of the access point and user terminal, allows "compatible"
correction vectors to be derived for the access point when the calibration is performed by different user terminals. If the access point has already been calibrated (e.g., by one or more other user terminals), then the current correction vectors may be updated with the newly derived correction vectors.
correction vectors to be derived for the access point when the calibration is performed by different user terminals. If the access point has already been calibrated (e.g., by one or more other user terminals), then the current correction vectors may be updated with the newly derived correction vectors.
[0060] For example, if two user terminals simultaneously perform the calibration procedure, then the calibration results from these user terminals may be averaged to improve performance. However, calibration is typically performed for one user terminal at a time. So the second user terminal observes the downlink with the correction vector for the first user terminal already applied. In this case, the product of the second correction vector with the old correction vector may be used as the new correction vector, or a "weighted averaging" (described below) may also be used. The access point typically uses a single correction vector for all user terminals, and not different ones for different user terminals (although this may also be implemented).
Updates from multiple user terminals or sequential updates from one user terminal may be treated in the same manner. The updated vectors may be directly applied (by a product operation). Alternatively, if some averaging is desired to reduce measurement noise, then weighted averaging may be used as described below.
Updates from multiple user terminals or sequential updates from one user terminal may be treated in the same manner. The updated vectors may be directly applied (by a product operation). Alternatively, if some averaging is desired to reduce measurement noise, then weighted averaging may be used as described below.
[0061] Thus, if the access point uses correction vectors k~Pl(k) to transmit the MIMO
pilot from which the user terminal determines new correction vectors k ~PZ (k) , then the updated correction vectors k~P3(k) are the product of the current and new correction vectors. The correction vectors kaPl(k) and kap2(k) may be derived by the same or different user terminals.
pilot from which the user terminal determines new correction vectors k ~PZ (k) , then the updated correction vectors k~P3(k) are the product of the current and new correction vectors. The correction vectors kaPl(k) and kap2(k) may be derived by the same or different user terminals.
[0062] In one embodiment, the updated correction vectors are defined as k~p3 (k) = kaP, (k) ~ kaP2 (k) , where the multiplication is element-by-element. In another embodiment, the updated correction vectors may be redefined as ., a ~ap3 (k) = kapl(k) ~ ~ap2(k) ~ where a is a factor used to provide weighted averaging (e.g., 0 < e~ < 1 ). If the calibration updates are infrequent, then ~ close to one might perform best. If the calibration updates are frequent but noisy, then a smaller value for ~ is better. The updated correction vectors k ~p3 (k) may then be used by the access point until they are updated again.
[0063] As noted above, the calibration may be performed for fewer than all data subbands. For example, the calibration may be performed for every fi-th subband, where n may be determined by the expected response of the transmitlreceive chains (e.g., h may be 2, 4, 8, 16, and so on). The calibration may also be performed for non-uniformly distributed subbands. For example, since there may be more filter roll-off at the edges of the passband, which may create more mismatch in the transmitlreceive chains, more subbands near the band edges may be calibrated. In general, any number and any distribution of subbands may be calibrated, and this is within the scope of the invention.
[0064] In the above description, the correction vectors kap (k) and ku~ (k) , for k E K', are derived by the user terminal, and the vectors kaP(k) are sent back to the access point. This scheme advantageously distributes the calibration processing among the user terminals for a multiple-access system. However, the correction vectors k ap (k) and k~~ (k) may also be derived by the access point, which would then send the vectors k ~~ (k) back to the user terminal, and this is within the scope of the invention.
[0065] The calibration scheme described above allows each user terminal to calibrate its transmit/receive chains in real-time via over-the-air transmission. This allows user terminals with different frequency responses to achieve high performance without the need for tight frequency response specifications or to perform calibration at the factory.
The access point may be calibrated by multiple user terminals to provide improved accuracy.
D. Gain Considerations [0066] The calibration may be performed based on "normalized" gains for the downlink and uplink channels, which are gains given relative to the noise floor at the receiver.
The use of the normalized gains allows the characteristics of one link (including the channel gains and SNR per eigenmode) to be obtained based on gain measurements for the other link, after the downlink and uplink have been calibrated.
The access point may be calibrated by multiple user terminals to provide improved accuracy.
D. Gain Considerations [0066] The calibration may be performed based on "normalized" gains for the downlink and uplink channels, which are gains given relative to the noise floor at the receiver.
The use of the normalized gains allows the characteristics of one link (including the channel gains and SNR per eigenmode) to be obtained based on gain measurements for the other link, after the downlink and uplink have been calibrated.
[0067] The access point and user terminal may initially balance their receiver input levels such that the noise levels on the receive paths for the access point and user terminal are approximately the same. The balancing may be done by estimating the noise floor, that is, finding a section of a received TDD frame (i.e., a unit of downlink/uplink transmission) that has a minimum average power over a particular time duration (e.g., one or two symbol periods). Generally, the time just before the start of each TDD frame is clear of transmissions, since any uplink data needs to be received by the access point and then a receive/transmit turnaround time is necessary before the access point transmits on the downlink. Depending on the interference environment, the noise floor may be determined based on a number of TDD frames. The downlink and uplink channel responses are then measured relative to this noise floor. More specifically, the channel gain for a given subband of a given transmit/receive antenna pair may first be obtained, for example, as the ratio of the received pilot symbol over the transmitted pilot symbol for that subband of that transmit/receive antenna pair. The normalized gain is then the measured gain divided by the noise floor.
[0068] A large difference in the normalized gains for the access point and the normalized gains for the user terminal can result in the correction factors for the user terminal being greatly different from unity. The correction factors for the access point are close to unity because the first element of the matrix Kap is set to 1.
[0069] If the correction factors for the user terminal differ greatly from unity, then the user terminal may not be able to apply the computed correction factors. This is because the user terminal has a constraint on its maximum transmit power and may not be capable of increasing its transmit power for large correction factors.
Moreover, a reduction in transmit power for small correction factors is generally not desirable, since this may reduce the achievable data rate.
Moreover, a reduction in transmit power for small correction factors is generally not desirable, since this may reduce the achievable data rate.
[0070] Thus, the user terminal can transmit using a scaled version of the computed correction factors. The scaled calibration factors may be obtained by scaling the computed correction factors by a particular scaling value, which may be set equal to a gain delta (difference or ratio) between the downlink and uplink channel responses.
This gain delta can be computed as an average of the differences (or deltas) between the normalized gains for the downlink and uplink. The scaling value (or gain delta) used for the correction factors for the user terminal can be sent to the access point along with the computed correction factors for the access point.
This gain delta can be computed as an average of the differences (or deltas) between the normalized gains for the downlink and uplink. The scaling value (or gain delta) used for the correction factors for the user terminal can be sent to the access point along with the computed correction factors for the access point.
[0071] With the correction factors and the scaling value or gain delta, the downlink channel characteristics may be determined from the measured uplink channel response, and vice versa. If the noise floor at either the access point or the user terminal changes, then the gain delta can be updated, and the updated gain delta may be sent in a message to the other entity.
[0072] In the above description, the calibration results in two sets (or vectors or matrices) of correction factors for each subband, with one set being used by the access point for downlink data transmission and the other set being used by the user terminal for uplink data transmission. The calibration may also be performed such that two sets of correction factors are provided for each subband, with one set being used by the access point for uplink data reception and the other set being used by the user terminal for downlink data reception. The calibration may also be performed such that one set of correction factors is obtained for each subband, and this set may be used at either the access point or the user terminal. In general, the calibration is performed such that the calibrated downlink and uplink channel responses are reciprocal, regardless of where correction factors are applied.
2. MIMO Pilot [0073] For the calibration, a MIMO pilot is transmitted on the uplink by the user terminal to allow the access point to estimate the uplink channel response, and a MIMO
pilot is transmitted on the downlink by the access point to allow the user terminal to estimate the downlink channel response. The same or different MIMO pilots may be used for the downlink and uplink, and the MIMO pilots used are known at both the access point and user terminal.
2. MIMO Pilot [0073] For the calibration, a MIMO pilot is transmitted on the uplink by the user terminal to allow the access point to estimate the uplink channel response, and a MIMO
pilot is transmitted on the downlink by the access point to allow the user terminal to estimate the downlink channel response. The same or different MIMO pilots may be used for the downlink and uplink, and the MIMO pilots used are known at both the access point and user terminal.
[0074] In an embodiment, the MIMO pilot comprises a specific OFDM symbol (denoted as "P") that is transmitted from each of the N~ transmit antennas, where NT = NaP for the downlink and NT = Nun for the uplink. For each transmit antenna, the same P OFDM symbol is transmitted in each symbol period designated for MIMO
pilot transmission. However, the P OFDM symbols for each antenna are covered with a different N chip Walsh sequence assigned to that antenna, where N >_ NpP for the downlink and N >_ Nun for the uplink. The Walsh covering maintains orthogonality between the NT transmit antennas and allows the receiver to distinguish the individual transmit antennas.
pilot transmission. However, the P OFDM symbols for each antenna are covered with a different N chip Walsh sequence assigned to that antenna, where N >_ NpP for the downlink and N >_ Nun for the uplink. The Walsh covering maintains orthogonality between the NT transmit antennas and allows the receiver to distinguish the individual transmit antennas.
[0075] The P OFDM symbol includes one modulation symbol for each of the NSG
designated subbands. The P OFDM symbol thus comprises a specific "word" of N56 modulation symbols that may be selected to facilitate channel estimation by the receiver. This word may also be defined to minimize the peak-to-average variation in the transmitted MIMO pilot. This may then reduce the amount of distortion and non-linearity generated by the transmit/receive chains, which may then result in improved accuracy for the channel estimation.
designated subbands. The P OFDM symbol thus comprises a specific "word" of N56 modulation symbols that may be selected to facilitate channel estimation by the receiver. This word may also be defined to minimize the peak-to-average variation in the transmitted MIMO pilot. This may then reduce the amount of distortion and non-linearity generated by the transmit/receive chains, which may then result in improved accuracy for the channel estimation.
[0076] For clarity, a specific MIMO pilot is described below for a specific MIMO-OFDM system. For this system, the access point and user terminal each has four transmit/receive antennas. The system bandwidth is partitioned into 64 orthogonal subbands (i.e., NF = 64 ), which are assigned indices of +31 to -32. Of these subbands, 48 subbands (e.g., with indices of ~{ 1, ..., 6, 8, ..., 20, 22, ...
, 26}) are used for data, 4 subbands (e.g., with indices of ~{7, 21 }) are used for pilot and possibly signaling, the DC subband (with index of 0) is not used, and the remaining subbands are also not used and serve as guard subbands. This OFDM subband structure is described in further detail in a document for IEEE Standard 802.11a and entitled "Part 11:
Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHz Band," September 1999, which is publicly available and incorporated herein by reference.
, 26}) are used for data, 4 subbands (e.g., with indices of ~{7, 21 }) are used for pilot and possibly signaling, the DC subband (with index of 0) is not used, and the remaining subbands are also not used and serve as guard subbands. This OFDM subband structure is described in further detail in a document for IEEE Standard 802.11a and entitled "Part 11:
Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHz Band," September 1999, which is publicly available and incorporated herein by reference.
[0077] The P OFDM symbol includes a set of 52 QPSK modulation symbols for the data subbands and 4 pilot subbands. This P OFDM symbol may be given as follows:
P(real) = g ~ {0,0,0,0,0,0,-1,-l,-l,-l,l,l,l,-1,-1,1,-l,l,l,l,l,-l,-1,1,-1,1,-1,-1,-l,-1,1,-1, 0,1,-1,-1,-l,-1,1,-1,-l,-1,-1,1,1,-1,-1,1,-1,-1,1,1,-1,1,-1,1,-1,1,-,0,0,0,0,0}, P(imag) = g ~ {0,0,0,0,0,0,-l,l,l,l,-1,-1,1,-l,l,l,l,-1,1,-1,-1,-1,-1,-1,-1,1,1,-1,1,1,-1,1, 0,-1,-1,-1,-1,1,1,-1,1,-1,-l,l,-l,l,-1,1,1,1,-1,1,1,1,1,1,1,-1,-1,0,0,0,0,0}, where g is a gain for the pilot. The values within the { } bracleet are given for subband indices -32 through -1 (for the first line) and 0 through +31 (for the second line). Thus, the first line for P(real) and P(imag) indicates that symbol (-1- j) is transmitted in subband -26, symbol (-1 + j) is transmitted in subband -25, and so on. The second line for P(real) and P(imag) indicates that symbol (1- j) is transmitted in subband 1, symbol (-1- j) is transmitted in subband 2, and so on. Other OFDM symbols may also be used for the MIMO pilot.
P(real) = g ~ {0,0,0,0,0,0,-1,-l,-l,-l,l,l,l,-1,-1,1,-l,l,l,l,l,-l,-1,1,-1,1,-1,-1,-l,-1,1,-1, 0,1,-1,-1,-l,-1,1,-1,-l,-1,-1,1,1,-1,-1,1,-1,-1,1,1,-1,1,-1,1,-1,1,-,0,0,0,0,0}, P(imag) = g ~ {0,0,0,0,0,0,-l,l,l,l,-1,-1,1,-l,l,l,l,-1,1,-1,-1,-1,-1,-1,-1,1,1,-1,1,1,-1,1, 0,-1,-1,-1,-1,1,1,-1,1,-1,-l,l,-l,l,-1,1,1,1,-1,1,1,1,1,1,1,-1,-1,0,0,0,0,0}, where g is a gain for the pilot. The values within the { } bracleet are given for subband indices -32 through -1 (for the first line) and 0 through +31 (for the second line). Thus, the first line for P(real) and P(imag) indicates that symbol (-1- j) is transmitted in subband -26, symbol (-1 + j) is transmitted in subband -25, and so on. The second line for P(real) and P(imag) indicates that symbol (1- j) is transmitted in subband 1, symbol (-1- j) is transmitted in subband 2, and so on. Other OFDM symbols may also be used for the MIMO pilot.
[0078] In an embodiment, the four transmit antennas are assigned Walsh sequences of Wl =1111, WZ =1010 , W3 =1100 , and W4 =1001 for the MIMO pilot. For a given Walsh sequence, a value of "1" indicates that a P OFDM symbol is transmitted and a value of "0" indicates that a -P OFDM symbol is transmitted (i.e., each of the modulation symbols in P is inverted).
[0079] Table 1 lists the OFDM symbols transmitted from each of the four transmit antennas for a MIMO pilot transmission that spans four symbol periods.
Table 1 OFDM
Antenna Antenna Antenna Antenna symbol 1 2 3 4 1 +P +P +P +P
2 +P -P +P -P
3 +P +P -P -P
4 +P -p -P +P
For longer MIMO pilot transmission, the Walsh sequence for each transmit antenna is simply repeated. For this set of Walsh sequences, the MIMO pilot transmission occurs in integer multiples of four symbol periods to ensure orthogonality among the four transmit antennas.
Table 1 OFDM
Antenna Antenna Antenna Antenna symbol 1 2 3 4 1 +P +P +P +P
2 +P -P +P -P
3 +P +P -P -P
4 +P -p -P +P
For longer MIMO pilot transmission, the Walsh sequence for each transmit antenna is simply repeated. For this set of Walsh sequences, the MIMO pilot transmission occurs in integer multiples of four symbol periods to ensure orthogonality among the four transmit antennas.
[0080] The receiver may derive an estimate of the channel response based on the received MIMO pilot by performing the complementary processing. In particular, to recover the pilot sent from transmit antenna i and received by receive antenna j, the pilot received by receive antenna j is first processed with the Walsh sequence assigned to transmit antenna i in a complementary manner to the Walsh covering performed at the transmitter. The decovered OFDM symbols for all N~,S symbol periods for the MIMO
pilot are then accumulated, where the accumulation is performed individually for each of the 52 subbands used to carry the MIMO pilot. The results of the accumulation is h;, J (k) , for k = ~ {1, ..., 26} , which is an estimate of the effective channel response from transmit antenna i to receive antenna j (i.e., including the responses for the transmit/receive chains) for the 52 data and pilot subbands.
pilot are then accumulated, where the accumulation is performed individually for each of the 52 subbands used to carry the MIMO pilot. The results of the accumulation is h;, J (k) , for k = ~ {1, ..., 26} , which is an estimate of the effective channel response from transmit antenna i to receive antenna j (i.e., including the responses for the transmit/receive chains) for the 52 data and pilot subbands.
[0081] The same processing may be performed to recover the pilot from each transmit antenna at each receive antenna. The pilot processing provides Nap ~ Nun values that are the elements of the effective channel response estimate, HUP (k) or I3dn (k) , for each of the 52 subbands.
[0082] The channel estimation described above may be performed by both the access point and the user terminal during calibration to obtain the effective uplink channel response estimate Ii"P (k) and the effective downlink channel response estimate Han (k) , respectively, which are then used to derive the correction factors as described above.
3. Spatial Processing [0083] The correlation between the downlink and uplink channel responses may be exploited to simplify the channel estimation and spatial processing at the access point and user terminal for TDD MIMO and MIMO-OFDM systems. This simplification is possible after calibration has been performed to account for differences in the transmitlreceive chains. As noted above, the calibrated channel responses are:
H~a" (k) = Ha" (k)KaP (k) , for the downlink, and Eq (21a) H~"P (k) _ (Ha" (k)I~aP (k))T = H"P (k)K"t (k) , for the uplink. Eq (21b) The last equality in equation (21b) comes from using the relationship between the effective downlink and uplink channel responses, H"P (k) _ (K ~ (k)Ha" (k)KaP
(k))T
3. Spatial Processing [0083] The correlation between the downlink and uplink channel responses may be exploited to simplify the channel estimation and spatial processing at the access point and user terminal for TDD MIMO and MIMO-OFDM systems. This simplification is possible after calibration has been performed to account for differences in the transmitlreceive chains. As noted above, the calibrated channel responses are:
H~a" (k) = Ha" (k)KaP (k) , for the downlink, and Eq (21a) H~"P (k) _ (Ha" (k)I~aP (k))T = H"P (k)K"t (k) , for the uplink. Eq (21b) The last equality in equation (21b) comes from using the relationship between the effective downlink and uplink channel responses, H"P (k) _ (K ~ (k)Ha" (k)KaP
(k))T
[0084] The channel response matrix H(k) for each subband may be "diagonalized"
to obtain the NS eigenmodes for that subband. This may be achieved by performing either singular value decomposition on the channel response matrix H(k) or eigenvalue decomposition on the correlation matrix of H(k) , which is R(k) = HH (k)H(k) .
to obtain the NS eigenmodes for that subband. This may be achieved by performing either singular value decomposition on the channel response matrix H(k) or eigenvalue decomposition on the correlation matrix of H(k) , which is R(k) = HH (k)H(k) .
[0085] The singular value decomposition of the calibrated uplink channel response matrix, H~uP (k) , may be expressed as:
H~"p (k) = UaP (k)E(k)Vu (k) , for k ~ K , Eq (22) where IJap (k) is an (N"~ x Nur ) unitary matrix of left eigenvectors of H~up (k) ;
E(k) is an (Nun x N~p ) diagonal matrix of singular values of H~"p (k) ; and V "~ (k) is an (N"p x Nap ) unitary matrix of right eigenvectors of H~up (k) .
H~"p (k) = UaP (k)E(k)Vu (k) , for k ~ K , Eq (22) where IJap (k) is an (N"~ x Nur ) unitary matrix of left eigenvectors of H~up (k) ;
E(k) is an (Nun x N~p ) diagonal matrix of singular values of H~"p (k) ; and V "~ (k) is an (N"p x Nap ) unitary matrix of right eigenvectors of H~up (k) .
[0086] A unitary matrix M is characterized by the property MH M = I , where I
is the identity matrix. Correspondingly, the singular value decomposition of the calibrated downlink channel response matrix, H~a" (k) , may be expressed as:
H~an (k) = V U~ (k)E(k)U P (k) , for k E K . Eq (23) The matrices V u~ (k) and U p (k) are thus also matrices of left and right eigenvectors, respectively, of H~~, (k) . The matrices V "~ (k) , V u~ (k) , V U~ (k) , and V a (k) are different forms of the matrix V "~ (k) , and the matrices U~P (k) , LTaP (k) , U P (k) , and U P (k) are also different forms of the matrix UaP (k) . For simplicity, reference to the matrices U~P (k) and V~~ (k) in the following description may also refer to their various other forms. The matrices UaP (k) and V"~ (k) are used by the access point and user terminal, respectively, for spatial processing and are denoted as such by their subscripts.
is the identity matrix. Correspondingly, the singular value decomposition of the calibrated downlink channel response matrix, H~a" (k) , may be expressed as:
H~an (k) = V U~ (k)E(k)U P (k) , for k E K . Eq (23) The matrices V u~ (k) and U p (k) are thus also matrices of left and right eigenvectors, respectively, of H~~, (k) . The matrices V "~ (k) , V u~ (k) , V U~ (k) , and V a (k) are different forms of the matrix V "~ (k) , and the matrices U~P (k) , LTaP (k) , U P (k) , and U P (k) are also different forms of the matrix UaP (k) . For simplicity, reference to the matrices U~P (k) and V~~ (k) in the following description may also refer to their various other forms. The matrices UaP (k) and V"~ (k) are used by the access point and user terminal, respectively, for spatial processing and are denoted as such by their subscripts.
[0087] The singular value decomposition is described in further detail by Gilbert Strang entitled "Linear Algebra and Its Applications," Second Edition, Academic Press, 1980.
[0088] The user terminal can estimate the calibrated downlink channel response based on a MIMO pilot sent by the access point. The user terminal may then perform the singular value decomposition of the calibrated downlink channel response estimate Ii~~, (k) , for k E K , to obtain the diagonal matrices E(k) and the matrices V u~ (k) of left eigenvectors of I3~a" (k) . This singular value decomposition may be given as H~a" (k) = V"~ (k)~(k)U P (k) , where the hat (" ~ ") above each matrix indicates that it is an estimate of the actual matrix.
[0089] Similarly, the access point can estimate the calibrated uplink channel response based on a MIMO pilot sent by the user terminal. The access point may then perform the singular value decomposition of the calibrated uplink channel response estimate Ii~~P (k) , for k E K , to obtain the diagonal matrices E(k) and the matrices LT~P (k) of left eigenvectors of I3~Up (k) , for k ~ K . This singular value decomposition may be given as Ii~"p (k) = ITaP (k)E(k)V a (k) .
[0090] Because of the reciprocal channel and the calibration, the singular value decomposition only need to be performed by either the user terminal or the access point to obtain both matrices V"~ (k) and LTaP (k) . If performed by the user terminal, then the matrices V"t (k) are used for spatial processing at the user terminal and the matrices LTaP (k) may be sent back to the access point.
[0091] The access point may also be able to obtain the matrices U~p (k) and ~(k) based on a steered reference sent by the user terminal. Similarly, the user terminal may also be able to obtain the matrices VU~(k) and ~(k) based on a steered reference sent by the access point. The steered reference is described in detail in the aforementioned provisional U.S. Patent Application Serial No. 60/421,309.
[0092] The matrices U~P(k) and ~(k) may be used to transmit independent data streams on the NS eigenmodes of the MIMO channel, where NS <_ min{Na~,Nut } .
The spatial processing to transmit multiple data streams on the downlink and uplink is described below.
A. Uplink Spatial Processing [0093] The spatial processing by the user terminal for an uplink transmission may be expressed as:
x"P (k) = K"~ (k)V"t (k)suP (k) , for k E K , Eq (24) where x"p (k) the transmit vector for the uplink for the k-th subband; and s"P (k) is a "data" vector with up to NS non-zero entries for the modulation symbols to be transmitted on the NS eigenmodes of the k-th subband.
The spatial processing to transmit multiple data streams on the downlink and uplink is described below.
A. Uplink Spatial Processing [0093] The spatial processing by the user terminal for an uplink transmission may be expressed as:
x"P (k) = K"~ (k)V"t (k)suP (k) , for k E K , Eq (24) where x"p (k) the transmit vector for the uplink for the k-th subband; and s"P (k) is a "data" vector with up to NS non-zero entries for the modulation symbols to be transmitted on the NS eigenmodes of the k-th subband.
[0094] Additional processing may also be performed on the modulation symbols prior to transmission. For example, channel inversion may be applied across the data subbands (e.g., for each eigenmode) such that the received SNR is approximately equal for all data subbands. The spatial processing may then be expressed as:
x"P (k) = I~"t (k)V"t (k)W"p (k)sup (k) , for k E K , Eq (25) where W"P (k) is a matrix with weights for the (optional) uplink channel inversion.
x"P (k) = I~"t (k)V"t (k)W"p (k)sup (k) , for k E K , Eq (25) where W"P (k) is a matrix with weights for the (optional) uplink channel inversion.
[0095] The channel inversion may also be performed by assigning transmit power to each subband before the modulation takes place, in which case the vector s"P
(k) includes the channel inversion coefficients and the matrix W"P (k) can be omitted from equation (25). In the following description, the use of the matrix WUP (k) in an equation indicates that the channel inversion coefficients are not incorporated into the vector sUP(k) . The lack of the matrix WuP (k) in an equation can indicate either (1) channel inversion is not performed or (2) channel inversion is performed and incorporated into the vector s"P(k) .
(k) includes the channel inversion coefficients and the matrix W"P (k) can be omitted from equation (25). In the following description, the use of the matrix WUP (k) in an equation indicates that the channel inversion coefficients are not incorporated into the vector sUP(k) . The lack of the matrix WuP (k) in an equation can indicate either (1) channel inversion is not performed or (2) channel inversion is performed and incorporated into the vector s"P(k) .
[0096] Channel inversion may be performed as described in the aforementioned provisional U.S. Patent Application Serial No. 60/421,309 and in U.S. Patent Application Serial No. 10/229,209, entitled "Coded MIMO Systems with Selective Channel Inversion Applied Per Eigenmode," filed August 27, 2002, assigned to the assignee of the present application and incorporated herein by reference.
[0097] The received uplink transmission at the access point may be expressed as:
r"P (k) = HUP (k)x"P (k) + n(k) , for k E K , Eq (26) = LTap (k)~(k)sUP (k) + n(k) where r"p (k) is the received vector for the uplink for the k-th subband;
n(k) is additive white Gaussian noise (AWGN) for the k-th subband; and x"P (k) is as shown in equation (24).
r"P (k) = HUP (k)x"P (k) + n(k) , for k E K , Eq (26) = LTap (k)~(k)sUP (k) + n(k) where r"p (k) is the received vector for the uplink for the k-th subband;
n(k) is additive white Gaussian noise (AWGN) for the k-th subband; and x"P (k) is as shown in equation (24).
[0098] The spatial processing (or matched filtering) at the access point for the received uplink transmission may be expressed as:
SuP (k) _ ~_~ (k)U p (k)rup (k) .. -1 ~ H
_ ~ (k)UaP (k)(LTap (k)~(k)s"p (k) + n(k)) , for k E K , Eq (27) =s"p(k)+n(k) where s"p (k) is an estimate of the vector s"P (k) transmitted by the user terminal on the uplink, and n(k) is the post-processed noise. Equation (27) assumes that channel inversion was not performed at the transmitter and that the received vector r"p (k) is as shown in equation (26).
B. Downlink Spatial Processing [0099] The spatial processing by the access point for a downlink transmission may be expressed as:
"*
xa" (k) = Kap (k)U~P (k)san (k) , for k E K , Eq (28) where xd" (k) is the transmit vector and sap (k) is the data vector for the downlink.
SuP (k) _ ~_~ (k)U p (k)rup (k) .. -1 ~ H
_ ~ (k)UaP (k)(LTap (k)~(k)s"p (k) + n(k)) , for k E K , Eq (27) =s"p(k)+n(k) where s"p (k) is an estimate of the vector s"P (k) transmitted by the user terminal on the uplink, and n(k) is the post-processed noise. Equation (27) assumes that channel inversion was not performed at the transmitter and that the received vector r"p (k) is as shown in equation (26).
B. Downlink Spatial Processing [0099] The spatial processing by the access point for a downlink transmission may be expressed as:
"*
xa" (k) = Kap (k)U~P (k)san (k) , for k E K , Eq (28) where xd" (k) is the transmit vector and sap (k) is the data vector for the downlink.
[00100] Again, additional processing (e.g., channel inversion) may also be performed on the modulation symbols prior to transmission. The spatial processing may then be expressed as:
"*
xdn (k) = Kap (k)U~p (k) Wan (k)sdn (k) , for k E K , Eq (29) where Wdn (k) is a matrix with weights for the (optional) downlink channel inversion.
"*
xdn (k) = Kap (k)U~p (k) Wan (k)sdn (k) , for k E K , Eq (29) where Wdn (k) is a matrix with weights for the (optional) downlink channel inversion.
[00101] The received downlink transmission at the user terminal may be expressed as:
ran (k) = H~, (k)x~, (k) + n(k) , for k E K , Eq (30) "*
= V"t (k)~(k)s~, (k) + n(k) where xa" (k) is the transmit vector as shown in equation (28).
ran (k) = H~, (k)x~, (k) + n(k) , for k E K , Eq (30) "*
= V"t (k)~(k)s~, (k) + n(k) where xa" (k) is the transmit vector as shown in equation (28).
[00102] The spatial processing (or matched filtering) at the user terminal for the received downlink transmission may be expressed as:
Sdn (k) _ ~' I (k)V t (k)raa (k) .. -I .. T ..
_ ~ (k)V"~ (k)(V"I (k)E(k)sa" (k) +n(k)) , for k E K . Eq (31) = s~ (k) + n(k) Equation (31) assumes that channel inversion was not performed at the transmitter and that the received vector r~ (k) is as shown in equation (30).
Sdn (k) _ ~' I (k)V t (k)raa (k) .. -I .. T ..
_ ~ (k)V"~ (k)(V"I (k)E(k)sa" (k) +n(k)) , for k E K . Eq (31) = s~ (k) + n(k) Equation (31) assumes that channel inversion was not performed at the transmitter and that the received vector r~ (k) is as shown in equation (30).
[00103] Table 2 summarizes the spatial processing at the access point and user terminal for data transmission and reception. Table 2 assumes that the additional processing by W(k) is performed at the transmitter. However, if this additional processing is not performed, then W(k) can be regarded as the identify matrix.
Table 2 Uplink Downlink User Transmit : Receive Terminalxup (k) = I~"t (k)V"t (k)wupsan - _(k) _ ~ I (k)Vu (k)sUp (k) (k)ran (k).
Access Receive : Transmit Point s"P (k) _ ~ I (k)iJ p (k)rUpxan (k) = KaP (k)IJaP (k) (k) Wa" (k)S~, (k) [00104] In the above description and as shown in Table 2, the correction matrices K~P (k) and I~u~ (k) are used for the transmit spatial processing at the access point and user terminal, respectively. This can simplify the overall spatial processing since the modulation symbols may need to be scaled anyway (e.g., for channel inversion) and the correction matrices K~P (k) and K~t (k) may be combined with the weight matrices Wa" (k) and W~P (k) to obtain gain matrices Gan (k) and G~p (k) , where Ga" (k) = Wan (k)K~P (k) and Gup (k) = W~P (k)I~u~ (k) . The processing may also be performed such that the correction matrices are used for the receive spatial processing (instead of the transmit spatial processing).
4. MIMO-OFDM System [00105] FIG. 5 is a block diagram of an embodiment of an access point 502 and a user terminal 504 within a TDD MIMO-OFDM system. For simplicity, the following description assumes that the access point and user terminal are each equipped with four transmitlreceive antennas.
Table 2 Uplink Downlink User Transmit : Receive Terminalxup (k) = I~"t (k)V"t (k)wupsan - _(k) _ ~ I (k)Vu (k)sUp (k) (k)ran (k).
Access Receive : Transmit Point s"P (k) _ ~ I (k)iJ p (k)rUpxan (k) = KaP (k)IJaP (k) (k) Wa" (k)S~, (k) [00104] In the above description and as shown in Table 2, the correction matrices K~P (k) and I~u~ (k) are used for the transmit spatial processing at the access point and user terminal, respectively. This can simplify the overall spatial processing since the modulation symbols may need to be scaled anyway (e.g., for channel inversion) and the correction matrices K~P (k) and K~t (k) may be combined with the weight matrices Wa" (k) and W~P (k) to obtain gain matrices Gan (k) and G~p (k) , where Ga" (k) = Wan (k)K~P (k) and Gup (k) = W~P (k)I~u~ (k) . The processing may also be performed such that the correction matrices are used for the receive spatial processing (instead of the transmit spatial processing).
4. MIMO-OFDM System [00105] FIG. 5 is a block diagram of an embodiment of an access point 502 and a user terminal 504 within a TDD MIMO-OFDM system. For simplicity, the following description assumes that the access point and user terminal are each equipped with four transmitlreceive antennas.
[00106] On the downlink, at access point 502, a transmit (TX) data processor receives traffic data (i.e., information bits) from a data source 508 and signaling and other information from a controller 530. TX data processor 510 formats, codes, interleaves, and modulates (i.e., symbol maps) the data to provide a stream of modulation symbols for each eigenmode used for data transmission. A TX spatial processor 520 receives the modulation symbol streams from TX data processor 510 and performs spatial processing to provide four streams of transmit symbols, one stream for each antenna. TX spatial processor 520 also multiplexes in pilot symbols as appropriate (e.g., for calibration).
[00107] Each modulator (MOD) 522 receives and processes a respective transmit symbol stream to provide a corresponding stream of OFDM symbols. Each OFDM symbol stream is further processed by a transmit chain within modulator 522 to provide a corresponding downlink modulated signal. The four downlink modulated signals from modulator 522a through 522d are then transmitted from four antennas 524a through 524d, respectively.
[00108] At user terminal 504, antennas 552 receive the transmitted downlink modulated signals, and each antenna provides a received signal to a respective demodulator (DEMOD) 554. Each demodulator 554 (which includes a receive chain) performs processing complementary to that performed at modulator 522 and provides received symbols. A receive (RX) spatial processor 560 then performs spatial processing on the received symbols from all demodulators 554 to provide recovered symbols, which are estimates of the modulation symbols sent by the access point. During calibration, RX
spatial processor 560 provides a calibrated downlink channel estimate, H~~ (k) , based on the MIMO pilot transmitted by the access point.
spatial processor 560 provides a calibrated downlink channel estimate, H~~ (k) , based on the MIMO pilot transmitted by the access point.
[00109] An RX data processor 570 processes (e.g., symbol demaps, deinterleaves, and decodes) the recovered symbols to provide decoded data. The decoded data may include recovered traffic data, signaling, and so on, which are provided to a data sink 572 for storage and/or a controller 580 for further processing. During calibration, RX
data processor 570 provides the calibrated uplink channel estimate, H~uP (k) , which is derived by the access point and sent on the downlink.
data processor 570 provides the calibrated uplink channel estimate, H~uP (k) , which is derived by the access point and sent on the downlink.
[00110] Controllers 530 and 580 control the operation of various processing units at the access point and user terminal, respectively. During calibration, controller 580 may receive the channel response estimates H~an (k) and H~"P (k) , derive the correction matrices I~aP (k) and K"~ (k) , provide the matrices K"~ (k) to a TX spatial processor 592 for uplink transmission, and provide the matrices KaP (k) to a TX data processor 590 for transmission back to the access point. Memory units 532 and 582 store data and program codes used by controllers 530 and 580, respectively.
[00111] The processing for the uplink may be the same or different from the processing for the downlink. Data and signaling are processed (e.g., coded, interleaved, and modulated) by a TX data processor 590 and further spatially processed by TX
spatial processor 592, which multiplexes in pilot symbols during calibration. The pilot and modulation symbols are further processed by modulators 554 to generate uplink modulated signals, which are then transmitted via antennas 552 to the access point.
spatial processor 592, which multiplexes in pilot symbols during calibration. The pilot and modulation symbols are further processed by modulators 554 to generate uplink modulated signals, which are then transmitted via antennas 552 to the access point.
[00112] At access point 110, the uplink modulated signals are received by antennas 524, demodulated by demodulators 522, and processed by an RX spatial processor 540 and an RX data processor 542 in a complementary to that performed at the user terminal.
During calibration, RX spatial processor 560 also provides a calibrated uplink channel estimate, H~uP (k) , based on the MIMO pilot transmitted by the user terminal.
The matrices H~uP (k) are received by controller 530 and then provided to TX data processor 510 for transmission back to the user terminal.
During calibration, RX spatial processor 560 also provides a calibrated uplink channel estimate, H~uP (k) , based on the MIMO pilot transmitted by the user terminal.
The matrices H~uP (k) are received by controller 530 and then provided to TX data processor 510 for transmission back to the user terminal.
[00113] FIG. 6 is a block diagram of a TX spatial processor 520a, which may be used for TX spatial processors 520 and 592 in FIG. 5. For simplicity, the following description assumes that all four eigenmodes are selected for use.
[00114] Within processor 520a, a demultiplexer 632 receives four modulation symbol steams (denoted as sl(n) through s4(n) ) to be transmitted on four eigenmodes, demultiplexes each stream into ND substreams for the ND data subbands, and provides four modulation symbol substreams for each data subband to a respective TX
subband spatial processor 640. Each processor 640 performs the processing shown in equation (24), (25), (28), or (29) for one subband.
subband spatial processor 640. Each processor 640 performs the processing shown in equation (24), (25), (28), or (29) for one subband.
[00115] Within each TX subband spatial processor 640, the four modulation ' symbol substreams (denoted as sl(k) through s4(k)) are provided to four multipliers 642a through 642d, which also receive the gains g, (k), g2 (k), g3 (k), and g4 (k) for the four eigenmodes of the associated subband. For the downlink, the four gains for each data subband are the diagonal elements of the corresponding matrix Ga" (k) , where Gdn (k) = Kap (k) or Ga" (k) = Wan (k)K~p (k) . For the uplink, the gains are the diagonal elements of the matrix G uP (k) , where GuP (k) = Kut (k) or GuP (k) = WUp (k)Kut (k) .
Each multiplier 642 scales its modulation symbols with its gain gm (k) to provide scaled modulation symbols. Multipliers 642a through 642d provides four scaled modulation symbol substreams to four beam-formers 650a through 650d, respectively.
Each multiplier 642 scales its modulation symbols with its gain gm (k) to provide scaled modulation symbols. Multipliers 642a through 642d provides four scaled modulation symbol substreams to four beam-formers 650a through 650d, respectively.
[00116] Each beam-former 650 perfoi~rns beam-forming to transmit one symbol substream on one eigenmode of one subband. Each beam-former 650 receives one scaled symbol substream s", (k) and performs beam-forming using the eigenvector v_", (k) for the associated eigenmode. Within each beam-former 650, the scaled modulation symbols are provided to four multipliers 652a through 652d, which also receive four elements, vm,l (k), v,n,2 (k), v"~,3 (k), and v"~,4 (k) , of the eigenvector v", (k) for the associated eigenmode. The eigenvector _v", (k) is the rn-th column of the matrix UaP (k) for the downlink and is the m-th column of the matrix V u~ (k) for the uplink.
Each multiplier 652 then multiplies the scaled modulation symbols with its eigenvector value vm,l(k) to provide "beam-formed" symbols. Multipliers 652a through 652d provide four beam-formed symbol substreams (which are to be transmitted from four antennas) to summers 660a through 660d, respectively.
Each multiplier 652 then multiplies the scaled modulation symbols with its eigenvector value vm,l(k) to provide "beam-formed" symbols. Multipliers 652a through 652d provide four beam-formed symbol substreams (which are to be transmitted from four antennas) to summers 660a through 660d, respectively.
[00117] Each summer 660 receives and sums four beam-formed symbols for the four eigenmodes for each symbol period to provide a preconditioned symbol for an associated transmit antenna. Summers 660a through 660d provides four substreams of preconditioned symbols for four transmit antennas to bufferslmultiplexers 670a through 670d, respectively.
[00118] Each buffer/multiplexer 670 receives pilot symbols and the preconditioned symbols from TX subband spatial processors 640 for the ND data subbands. Each buffer/multiplexer 670 then multiplexes pilot symbols, preconditioned symbols, and zeros for the pilot subbands, data subbands, and unused subbands, respectively, to form a sequence of NF transmit symbols for that symbol period. During calibration, pilot symbols are transmitted on the designated subbands. Multipliers 668a through 668d cover the pilot symbols for the four antennas with Walsh sequences Wl through W4 , respectively, assigned to the four antennas, as described above and shown in Table 1.
Each buffer/multiplexer 670 provides a stream of transmit symbols xl (n) for one transmit antenna, where the transmit symbol stream comprises concatenated sequences of NF transmit symbols.
Each buffer/multiplexer 670 provides a stream of transmit symbols xl (n) for one transmit antenna, where the transmit symbol stream comprises concatenated sequences of NF transmit symbols.
[00119] The spatial processing and OFDM modulation is described in further detail in the aforementioned provisional U.S. Patent Application Serial No. 60/421,309.
[00120] In various embodiments of the invention as described herein, peer-peer communication between the various user terminals (UTs or STAB) in the same basic service set (BSS) or different BSSs can be implemented as described below. The UTs or STAs that calibrate with a single access point (AP) are members of a basic service set (BSS). The single access point is a common node to all UTs in the BSS. The calibration methods as described above facilitate the following types of communication:
(i) A UT in the BSS can use TX steering to communicate directly with the AP
on the uplink (UL) and the AP can use TX steering to communicate with the UTs on the downlink (DL).
(ii) A UT in the BSS can communicate directly with another UT in the same BSS using steering. In this case, this peer-peer communication has to be bootstrapped because neither UT knows the channel between them. In various embodiments, the bootstrap procedure works as follows:
- The initiator of the peer-peer link is the designate AP (DAP), and the other UT
is the designated UT (DUT).
- The DAP sends M1M0 pilot to the DUT along with a request to establish link, which contains the BSS ID plus the DAP ll~. The request needs to be sent in a common mode (i.e. Tx diversity).
- The DUT responds by sending back steered MIMO pilot plus an acknowledgement which contains the DUT ID, its BSS ID, and some rate indicator for the DAP to use.
- The DAP can then use steering on the DL and the DUT can use steering on the UL. Rate control and tracking can be accommodated by breaking the transmissions into DL and UL segments with sufficient time between them to allow for processing.
(iii) UTs that belong to one BSS (e.g., BSSl) can steer to UTs that belong to another BSS (e.g., BSSZ), even though each has calibrated with a different AP.
However, there will be a phase rotation ambiguity (per subband) in this case.
This is because the calibration procedure as described above establishes a reference which is unique to the AP it has calibrated with. The reference is a complex constant, a°(k~ .1 ) = gAPTX (0) gAPRX (~) where k is the subband index and j is the AP index and 0 is the index of the reference antenna (e.g., antenna 0) used on the AP. In one embodiment, this constant is common to all UTs in a given BSS, but is independent for different BSSs.
(i) A UT in the BSS can use TX steering to communicate directly with the AP
on the uplink (UL) and the AP can use TX steering to communicate with the UTs on the downlink (DL).
(ii) A UT in the BSS can communicate directly with another UT in the same BSS using steering. In this case, this peer-peer communication has to be bootstrapped because neither UT knows the channel between them. In various embodiments, the bootstrap procedure works as follows:
- The initiator of the peer-peer link is the designate AP (DAP), and the other UT
is the designated UT (DUT).
- The DAP sends M1M0 pilot to the DUT along with a request to establish link, which contains the BSS ID plus the DAP ll~. The request needs to be sent in a common mode (i.e. Tx diversity).
- The DUT responds by sending back steered MIMO pilot plus an acknowledgement which contains the DUT ID, its BSS ID, and some rate indicator for the DAP to use.
- The DAP can then use steering on the DL and the DUT can use steering on the UL. Rate control and tracking can be accommodated by breaking the transmissions into DL and UL segments with sufficient time between them to allow for processing.
(iii) UTs that belong to one BSS (e.g., BSSl) can steer to UTs that belong to another BSS (e.g., BSSZ), even though each has calibrated with a different AP.
However, there will be a phase rotation ambiguity (per subband) in this case.
This is because the calibration procedure as described above establishes a reference which is unique to the AP it has calibrated with. The reference is a complex constant, a°(k~ .1 ) = gAPTX (0) gAPRX (~) where k is the subband index and j is the AP index and 0 is the index of the reference antenna (e.g., antenna 0) used on the AP. In one embodiment, this constant is common to all UTs in a given BSS, but is independent for different BSSs.
[00121] As a result, when a UT from BSSl communicates with a UT in BSS2, steering without correction or compensation for this constant may result in a phase rotation and amplitude scaling of the entire eigensystem. The phase rotation can be determined through the use of pilot (steered and unsteered) and removed in the receivers of each respective UT. In one embodiment, the amplitude correction or compensation can simply be an SNR scaling and can be removed by estimation of the noise floor at each receiver, which may impact rate selection.
[00122] In various embodiments, the peer-peer exchange between UTs that belong to different BSSs may work as follows:
- The initiator of the peer-peer link (e.g., UT in BSS1) is the designate AP
(DAP), and the other UT (e.g., UT in BSS2) is the designated UT (DUT).
- The DAP sends MIMO pilot to the DUT along with a request to establish link, which contains the respective BSS )D plus the DAP )D. The request needs to be sent in a common mode (i.e. Tx diversity).
The DUT responds by sending back steered MIMO pilot plus an acknowledgement which contains DUT )D, its BSS ID, and some rate indicator for the DAP to use.
- The DAP receiver (Rx) can estimate the phase rotation on the uplink (UL) and apply the correction constant to each subband. The DAP can then use steering on the downlink (DL) but needs to include a preamble of steered reference on at least the first steered packet to allow the DUT receiver (Rx) to correct or compensate for the phase rotation on the DL for each subband. Subsequent DL transmissions may not require a steered reference preamble. Rate control and tracking can be accommodated by breaking the transmissions into DL and UL segments with sufficient time between them to allow for processing.
- The initiator of the peer-peer link (e.g., UT in BSS1) is the designate AP
(DAP), and the other UT (e.g., UT in BSS2) is the designated UT (DUT).
- The DAP sends MIMO pilot to the DUT along with a request to establish link, which contains the respective BSS )D plus the DAP )D. The request needs to be sent in a common mode (i.e. Tx diversity).
The DUT responds by sending back steered MIMO pilot plus an acknowledgement which contains DUT )D, its BSS ID, and some rate indicator for the DAP to use.
- The DAP receiver (Rx) can estimate the phase rotation on the uplink (UL) and apply the correction constant to each subband. The DAP can then use steering on the downlink (DL) but needs to include a preamble of steered reference on at least the first steered packet to allow the DUT receiver (Rx) to correct or compensate for the phase rotation on the DL for each subband. Subsequent DL transmissions may not require a steered reference preamble. Rate control and tracking can be accommodated by breaking the transmissions into DL and UL segments with sufficient time between them to allow for processing.
[00123] The calibration techniques described herein may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the techniques may be implemented at the access point and user terminal within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.
[00124] For a software implementation, the calibration techniques may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit (e.g., memory units 532 and 582 in FIG. 5) and executed by a processor (e.g., controllers 530 and 580, as appropriate). The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.
[00125] Headings are included herein for reference and to aid in locating certain sections. These headings are not intended to limit the scope of the concepts described therein under, and these concepts may have applicability in other sections throughout the entire specification.
[00126] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
WHAT IS CLAIMED IS:
WHAT IS CLAIMED IS:
Claims (39)
1. A method for calibrating downlink and uplink channels in a wireless communication system, comprising:
obtaining an estimate of a downlink channel response;
obtaining an estimate of an uplink channel response;
determining first and second sets of correction factors based on the estimates of the downlink and uplink channel responses; and calibrating the downlink channel and uplink channel based on the first and second sets of correction factors, respectively, to form a calibrated downlink channel and a calibrated uplink channel.
obtaining an estimate of a downlink channel response;
obtaining an estimate of an uplink channel response;
determining first and second sets of correction factors based on the estimates of the downlink and uplink channel responses; and calibrating the downlink channel and uplink channel based on the first and second sets of correction factors, respectively, to form a calibrated downlink channel and a calibrated uplink channel.
2. The method of claim 1, wherein the first set of correction factors is used to scale symbols prior to transmission on the downlink channel and the second set of correction factors is used to scale symbols prior to transmission on the uplink channel.
3. The method of claim 1, wherein the first set of correction factors is used to scale symbols received on the downlink channel and the second set of correction factors is used to scale symbols received on the uplink channel.
4. The method of claim 1, wherein the first and second sets of correction factors are determined based on the following equation:
where ~dn is a matrix for the estimate of the downlink channel response, ~up is a matrix for the estimate of the uplink channel response, ~ap is a matrix for the first set of correction factors, ~ut is a matrix for the second set of correction factors, and "T" denotes a transpose.
where ~dn is a matrix for the estimate of the downlink channel response, ~up is a matrix for the estimate of the uplink channel response, ~ap is a matrix for the first set of correction factors, ~ut is a matrix for the second set of correction factors, and "T" denotes a transpose.
5. The method of claim 4, wherein determining the first and second sets of correction factors includes:
computing a matrix C as an element-wise ratio of the matrix ~up over the matrix ~dn, and deriving the matrices ~ap and ~ut based on the matrix C.
computing a matrix C as an element-wise ratio of the matrix ~up over the matrix ~dn, and deriving the matrices ~ap and ~ut based on the matrix C.
6. The method of claim 5, wherein the deriving the matrix ~ut includes normalizing each of a plurality of rows of the matrix C, and determining a mean of the plurality of normalized rows of the matrix C, and wherein the matrix ~ut is formed based on the mean of the plurality of normalized rows.
7. The method of claim 5, wherein the deriving the matrix ~ap includes normalizing each of a plurality of columns of the matrix C, and determining a mean of inverses of the plurality of normalized columns of the matrix C, and wherein the matrix ~ap is formed based on the mean of the inverses of the plurality of normalized columns.
8. The method of claim 4, wherein the matrices ~ut and ~ap are derived based on a minimum mean square error (MMSE) computation.
9. The method of claim 8, wherein the MMSE computation minimizes a mean square error (MSE) given as
10. The method of claim 1, further comprising:
determining a scaling value indicative of an average difference between the estimate of the downlink channel response and the estimate of the uplink channel response.
determining a scaling value indicative of an average difference between the estimate of the downlink channel response and the estimate of the uplink channel response.
11. The method of claim 1, wherein the estimates for the downlink and uplink channel responses are normalized to account for receiver noise floor.
12. The method of claim 1, wherein the determining is performed at a user terminal.
13. The method of claim 4, wherein a first set of matrices of correction factors for the downlink channel is determined for a first set of subbands, the method further comprising:
interpolating the first set of matrices to obtain a second set of matrices of correction factors for the downlink channel for a second set of subbands.
interpolating the first set of matrices to obtain a second set of matrices of correction factors for the downlink channel for a second set of subbands.
14. The method of claim 1, wherein the estimates of the downlink and uplink channel responses are each obtained based on a pilot transmitted from a plurality of antennas and orthogonalized with a plurality of orthogonal sequences.
15. The method of claim 1 wherein the estimate of the uplink channel response is obtained based on a pilot transmitted on the uplink channel and wherein the estimate of the downlink channel response is obtained based on a pilot transmitted on the downlink channel.
16. The method of claim 1, wherein the TDD system is a multiple-input multiple-output (MIMO) system.
17. The method of claim 1, wherein the TDD system utilizes orthogonal frequency division multiplexing (OFDM).
18. A method for calibrating downlink and uplink channels in a wireless time division duplexed (TDD) multiple-input multiple-output (MIMO) communication system, comprising:
transmitting a pilot on the uplink channel;
obtaining an estimate of an uplink channel response derived based on the pilot transmitted on the uplink channel;
receiving a pilot on the downlink channel;
obtaining an estimate of a downlink channel response derived based on the pilot received on the downlink channel; and determining first and second sets of correction factors based on the estimates of the downlink and uplink channel responses, wherein a calibrated downlink channel is formed by using the first set of correction factors for the downlink channel and a calibrated uplink channel is formed by using the second set of correction factors for the uplink channel.
transmitting a pilot on the uplink channel;
obtaining an estimate of an uplink channel response derived based on the pilot transmitted on the uplink channel;
receiving a pilot on the downlink channel;
obtaining an estimate of a downlink channel response derived based on the pilot received on the downlink channel; and determining first and second sets of correction factors based on the estimates of the downlink and uplink channel responses, wherein a calibrated downlink channel is formed by using the first set of correction factors for the downlink channel and a calibrated uplink channel is formed by using the second set of correction factors for the uplink channel.
19. The method of claim 18, wherein the first and second sets of correction factors are determined based on a minimum mean square error (MMSE) computation.
20. The method of claim 18, wherein the first and second sets of correction factors are determined based on a matrix-ratio computation.
21. The method of claim 18, wherein the first set of correction factors is updated based on calibration with a plurality of user terminals.
22. The method of claim 18, further comprising:
scaling symbols with the first set of correction factors prior to transmission on the downlink.
scaling symbols with the first set of correction factors prior to transmission on the downlink.
23. The method of claim 18, further comprising:
scaling symbols with the second set of correction factors prior to transmission on the uplink channel.
scaling symbols with the second set of correction factors prior to transmission on the uplink channel.
24. An apparatus in a wireless time division duplexed (TDD) multiple-input multiple-output (MIMO) communication system, comprising:
means for obtaining an estimate of a response of a downlink channel;
means for obtaining an estimate of a response of an uplink channel; and means for determining first and second sets of correction factors based on the estimates of the downlink and uplink channel responses, wherein a calibrated downlink channel is formed by using the first set of correction factors for the downlink channel and a calibrated uplink channel is formed by using the second set of correction factors for the uplink channel.
means for obtaining an estimate of a response of a downlink channel;
means for obtaining an estimate of a response of an uplink channel; and means for determining first and second sets of correction factors based on the estimates of the downlink and uplink channel responses, wherein a calibrated downlink channel is formed by using the first set of correction factors for the downlink channel and a calibrated uplink channel is formed by using the second set of correction factors for the uplink channel.
25. A user terminal in a wireless time division duplexed (TDD) communication system, comprising:
an TX spatial processor operative to transmit a first pilot on an uplink channel;
an RX spatial processor operative to receive a second pilot on a downlink channel and derive an estimate of a downlink channel response based on the received second pilot, and to receive an estimate of an uplink channel response derived based on the transmitted first pilot; and a controller operative to determine first and second sets of correction factors based on the estimates of the downlink and uplink channel responses, wherein a calibrated downlink channel is formed by using the first set of correction factors for the downlink channel and a calibrated uplink channel is formed by using the second set of correction factors for the uplink channel
an TX spatial processor operative to transmit a first pilot on an uplink channel;
an RX spatial processor operative to receive a second pilot on a downlink channel and derive an estimate of a downlink channel response based on the received second pilot, and to receive an estimate of an uplink channel response derived based on the transmitted first pilot; and a controller operative to determine first and second sets of correction factors based on the estimates of the downlink and uplink channel responses, wherein a calibrated downlink channel is formed by using the first set of correction factors for the downlink channel and a calibrated uplink channel is formed by using the second set of correction factors for the uplink channel
26. The user terminal of claim 25, wherein the controller is further operative to determine the first and second sets of correction factor based on a minimum mean square error (MMSE) computation.
27. The user terminal of claim 25, wherein the controller is further operative to determine the first and second sets of correction factor based on a matrix-ratio computation.
28. A method for communication in a wireless system, comprising:
calibrating one or more communication links between a plurality of user stations and one or more access points, based on one or more sets of correction factors derived from estimates of channel responses associated with the one or more communication links, the plurality of user stations including a first user station and a second user station; and establishing communication between the first and second user stations using steering without performing calibration between the first and second user stations.
calibrating one or more communication links between a plurality of user stations and one or more access points, based on one or more sets of correction factors derived from estimates of channel responses associated with the one or more communication links, the plurality of user stations including a first user station and a second user station; and establishing communication between the first and second user stations using steering without performing calibration between the first and second user stations.
29. The method of claim 28 wherein establishing the communication between the first and second user stations comprises:
sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station;
transmitting information between the first and second user stations using steering based on the steered pilot.
sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station;
transmitting information between the first and second user stations using steering based on the steered pilot.
30. The method of claim 29 wherein the request to establish the communication comprises an identifier of a basic service set to which the first user station belongs and an identifier of the first user station.
31. The method of claim 29 wherein the acknowledgment comprises an identifier of the second user station, an identifier of a basic service set to which the second user station belongs, and a data rate indicator.
32. The method of claim 28 wherein the one or more access points includes a first access point associated with a first basic service set (BSS) and a second access point associated with a second BSS, wherein the first user station is calibrated with respect to the first access point and the second user station is calibrated with respect to the second access point, and wherein establishing the communication between the first and second user stations comprises:
sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station; and transmitting information between the first and second user stations using steering that is adjusted to compensate for a phase rotation caused by calibration of the first and second user stations with respect to different access points.
sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station; and transmitting information between the first and second user stations using steering that is adjusted to compensate for a phase rotation caused by calibration of the first and second user stations with respect to different access points.
33. The method of claim 32 wherein the phase rotation is determined based on the steered pilot received from the second user station.
34. An apparatus for communication in a wireless system, comprising:
means for alibrating one or more communication links between a plurality of user stations and one or more access points, based on one or more sets of correction factors derived from estimates of channel responses associated with the one or more communication links, the plurality of user stations including a first user station and a second user station; and means for establishing communication between the first and second user stations using steering without performing calibration between the first and second user stations.
means for alibrating one or more communication links between a plurality of user stations and one or more access points, based on one or more sets of correction factors derived from estimates of channel responses associated with the one or more communication links, the plurality of user stations including a first user station and a second user station; and means for establishing communication between the first and second user stations using steering without performing calibration between the first and second user stations.
35. The apparatus of claim 34 wherein establishing the communication between the first and second user stations comprises:
means for sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
means for sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station;
means for transmitting information between the first and second user stations using steering based on the steered pilot.
means for sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
means for sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station;
means for transmitting information between the first and second user stations using steering based on the steered pilot.
36. The apparatus of claim 35 wherein the request to establish the communication comprises an identifier of a basic service set to which the first user station belongs and an identifier of the first user station.
37. The apparatus of claim 35 wherein the acknowledgment comprises an identifier of the second user station, an identifier of a basic service set to which the second user station belongs, and a data rate indicator.
38. The apparatus of claim 34 wherein the one or more access points includes a first access point associated with a first basic service set (BSS) and a second access point associated with a second BSS, wherein the first user station is calibrated with respect to the first access point and the second user station is calibrated with respect to the second access point, and wherein establishing the communication between the first and second user stations comprises:
sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station; and transmitting information between the first and second user stations using steering that is adjusted to compensate for a phase rotation caused by calibration of the first and second user stations with respect to different access points.
sending, from the first user station, a pilot and a request to establish a communication link with the second user station;
sending, from the second user station, a steered pilot and an acknowledgment in response to receiving the pilot and the request from first user station; and transmitting information between the first and second user stations using steering that is adjusted to compensate for a phase rotation caused by calibration of the first and second user stations with respect to different access points.
39. The apparatus of claim 38 wherein the phase rotation is determined based on the steered pilot received from the second user station.
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Families Citing this family (125)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6360100B1 (en) | 1998-09-22 | 2002-03-19 | Qualcomm Incorporated | Method for robust handoff in wireless communication system |
US8194770B2 (en) * | 2002-08-27 | 2012-06-05 | Qualcomm Incorporated | Coded MIMO systems with selective channel inversion applied per eigenmode |
US7986742B2 (en) | 2002-10-25 | 2011-07-26 | Qualcomm Incorporated | Pilots for MIMO communication system |
US8320301B2 (en) | 2002-10-25 | 2012-11-27 | Qualcomm Incorporated | MIMO WLAN system |
US20040081131A1 (en) | 2002-10-25 | 2004-04-29 | Walton Jay Rod | OFDM communication system with multiple OFDM symbol sizes |
US7324429B2 (en) | 2002-10-25 | 2008-01-29 | Qualcomm, Incorporated | Multi-mode terminal in a wireless MIMO system |
US8570988B2 (en) * | 2002-10-25 | 2013-10-29 | Qualcomm Incorporated | Channel calibration for a time division duplexed communication system |
US8208364B2 (en) | 2002-10-25 | 2012-06-26 | Qualcomm Incorporated | MIMO system with multiple spatial multiplexing modes |
US8169944B2 (en) * | 2002-10-25 | 2012-05-01 | Qualcomm Incorporated | Random access for wireless multiple-access communication systems |
US8218609B2 (en) | 2002-10-25 | 2012-07-10 | Qualcomm Incorporated | Closed-loop rate control for a multi-channel communication system |
US8134976B2 (en) * | 2002-10-25 | 2012-03-13 | Qualcomm Incorporated | Channel calibration for a time division duplexed communication system |
US7002900B2 (en) | 2002-10-25 | 2006-02-21 | Qualcomm Incorporated | Transmit diversity processing for a multi-antenna communication system |
US8170513B2 (en) | 2002-10-25 | 2012-05-01 | Qualcomm Incorporated | Data detection and demodulation for wireless communication systems |
US7333788B2 (en) * | 2002-12-20 | 2008-02-19 | Texas Instruments Incorporated | Method for calibrating automatic gain control in wireless devices |
US7668541B2 (en) | 2003-01-31 | 2010-02-23 | Qualcomm Incorporated | Enhanced techniques for using core based nodes for state transfer |
US7058367B1 (en) * | 2003-01-31 | 2006-06-06 | At&T Corp. | Rate-adaptive methods for communicating over multiple input/multiple output wireless systems |
US7200405B2 (en) | 2003-11-18 | 2007-04-03 | Interdigital Technology Corporation | Method and system for providing channel assignment information used to support uplink and downlink channels |
US9473269B2 (en) | 2003-12-01 | 2016-10-18 | Qualcomm Incorporated | Method and apparatus for providing an efficient control channel structure in a wireless communication system |
US7145940B2 (en) * | 2003-12-05 | 2006-12-05 | Qualcomm Incorporated | Pilot transmission schemes for a multi-antenna system |
US8204149B2 (en) | 2003-12-17 | 2012-06-19 | Qualcomm Incorporated | Spatial spreading in a multi-antenna communication system |
US7336746B2 (en) * | 2004-12-09 | 2008-02-26 | Qualcomm Incorporated | Data transmission with spatial spreading in a MIMO communication system |
US11152971B2 (en) * | 2004-02-02 | 2021-10-19 | Charles Abraham | Frequency modulated OFDM over various communication media |
US8169889B2 (en) | 2004-02-18 | 2012-05-01 | Qualcomm Incorporated | Transmit diversity and spatial spreading for an OFDM-based multi-antenna communication system |
US7206354B2 (en) * | 2004-02-19 | 2007-04-17 | Qualcomm Incorporated | Calibration of downlink and uplink channel responses in a wireless MIMO communication system |
US8077691B2 (en) | 2004-03-05 | 2011-12-13 | Qualcomm Incorporated | Pilot transmission and channel estimation for MISO and MIMO receivers in a multi-antenna system |
US7394793B2 (en) * | 2004-03-12 | 2008-07-01 | Samsung Electronics Co., Ltd. | Method and apparatus for generating preambles in a broadband wireless communication system using multiple antennas |
US7742533B2 (en) | 2004-03-12 | 2010-06-22 | Kabushiki Kaisha Toshiba | OFDM signal transmission method and apparatus |
US20050238111A1 (en) * | 2004-04-09 | 2005-10-27 | Wallace Mark S | Spatial processing with steering matrices for pseudo-random transmit steering in a multi-antenna communication system |
US8923785B2 (en) * | 2004-05-07 | 2014-12-30 | Qualcomm Incorporated | Continuous beamforming for a MIMO-OFDM system |
US8285226B2 (en) * | 2004-05-07 | 2012-10-09 | Qualcomm Incorporated | Steering diversity for an OFDM-based multi-antenna communication system |
JP4447372B2 (en) * | 2004-05-13 | 2010-04-07 | 株式会社エヌ・ティ・ティ・ドコモ | RADIO COMMUNICATION SYSTEM, RADIO COMMUNICATION DEVICE, RADIO RECEPTION DEVICE, RADIO COMMUNICATION METHOD, AND CHANNEL ESTIMATION METHOD |
US7110463B2 (en) * | 2004-06-30 | 2006-09-19 | Qualcomm, Incorporated | Efficient computation of spatial filter matrices for steering transmit diversity in a MIMO communication system |
US7978649B2 (en) | 2004-07-15 | 2011-07-12 | Qualcomm, Incorporated | Unified MIMO transmission and reception |
US7706324B2 (en) | 2004-07-19 | 2010-04-27 | Qualcomm Incorporated | On-demand reverse-link pilot transmission |
JP4744965B2 (en) * | 2004-08-09 | 2011-08-10 | パナソニック株式会社 | Wireless communication device |
KR100725773B1 (en) * | 2004-08-20 | 2007-06-08 | 삼성전자주식회사 | Apparatus and method for adaptively changing the uplink power control scheme depending on the status of mobile station in a wireless mobile communication system using time division duplexing scheme |
US7978778B2 (en) | 2004-09-03 | 2011-07-12 | Qualcomm, Incorporated | Receiver structures for spatial spreading with space-time or space-frequency transmit diversity |
US7265714B2 (en) * | 2004-09-23 | 2007-09-04 | Interdigital Technology Corporation | Pattern diversity to support a MIMO communications system and associated methods |
US7564914B2 (en) * | 2004-12-14 | 2009-07-21 | Broadcom Corporation | Method and system for frame formats for MIMO channel measurement exchange |
US7596355B2 (en) * | 2004-11-29 | 2009-09-29 | Intel Corporation | System and method capable of closed loop MIMO calibration |
US7719993B2 (en) | 2004-12-30 | 2010-05-18 | Intel Corporation | Downlink transmit beamforming |
JP4646680B2 (en) * | 2005-03-04 | 2011-03-09 | 三洋電機株式会社 | Calibration method and radio apparatus and communication system using the same |
FR2883681A1 (en) * | 2005-03-23 | 2006-09-29 | France Telecom | METHOD FOR ALLOCATING SUBWAYS TO MULTI-CHANNEL LINK STREAMS IN A MULTI-CHANNEL MODULATION COMMUNICATION SYSTEM |
US20060221904A1 (en) * | 2005-03-31 | 2006-10-05 | Jacob Sharony | Access point and method for wireless multiple access |
US8483200B2 (en) | 2005-04-07 | 2013-07-09 | Interdigital Technology Corporation | Method and apparatus for antenna mapping selection in MIMO-OFDM wireless networks |
TWI506977B (en) * | 2005-04-07 | 2015-11-01 | Interdigital Tech Corp | Method and apparatus for antenna mapping selection in mimo-ofdm wireless networks |
JP4646682B2 (en) * | 2005-04-13 | 2011-03-09 | 三洋電機株式会社 | Calibration method and radio apparatus and communication system using the same |
US7466749B2 (en) | 2005-05-12 | 2008-12-16 | Qualcomm Incorporated | Rate selection with margin sharing |
WO2006124042A1 (en) * | 2005-05-13 | 2006-11-23 | Qualcomm Incorporated | On-demand reverse-link pilot transmission |
US8358714B2 (en) | 2005-06-16 | 2013-01-22 | Qualcomm Incorporated | Coding and modulation for multiple data streams in a communication system |
US8498669B2 (en) | 2005-06-16 | 2013-07-30 | Qualcomm Incorporated | Antenna array calibration for wireless communication systems |
KR100880991B1 (en) | 2005-06-16 | 2009-02-03 | 삼성전자주식회사 | Apparatus and method for transmitting and receiving pilot by using multiple antenna in mobile communication system |
US8559295B2 (en) * | 2005-08-15 | 2013-10-15 | Motorola Mobility Llc | Method and apparatus for pilot signal transmission |
KR20070032548A (en) * | 2005-09-16 | 2007-03-22 | 삼성전자주식회사 | Apparatus and method for calibrating channel in wireless communication system using multiple antennas |
US8982778B2 (en) | 2005-09-19 | 2015-03-17 | Qualcomm Incorporated | Packet routing in a wireless communications environment |
US8983468B2 (en) | 2005-12-22 | 2015-03-17 | Qualcomm Incorporated | Communications methods and apparatus using physical attachment point identifiers |
US9066344B2 (en) | 2005-09-19 | 2015-06-23 | Qualcomm Incorporated | State synchronization of access routers |
US8982835B2 (en) * | 2005-09-19 | 2015-03-17 | Qualcomm Incorporated | Provision of a move indication to a resource requester |
US9078084B2 (en) * | 2005-12-22 | 2015-07-07 | Qualcomm Incorporated | Method and apparatus for end node assisted neighbor discovery |
US9736752B2 (en) | 2005-12-22 | 2017-08-15 | Qualcomm Incorporated | Communications methods and apparatus using physical attachment point identifiers which support dual communications links |
RU2395163C2 (en) * | 2005-11-02 | 2010-07-20 | Квэлкомм Инкорпорейтед | Calibration of antenna matrix for multi-input-multi-output systems of wireless communication |
US9118111B2 (en) | 2005-11-02 | 2015-08-25 | Qualcomm Incorporated | Antenna array calibration for wireless communication systems |
KR101019394B1 (en) * | 2005-11-02 | 2011-03-07 | 퀄컴 인코포레이티드 | Antenna array calibration for multi-input multi-output wireless communication systems |
US8280430B2 (en) | 2005-11-02 | 2012-10-02 | Qualcomm Incorporated | Antenna array calibration for multi-input multi-output wireless communication systems |
EP1791278A1 (en) | 2005-11-29 | 2007-05-30 | Interuniversitair Microelektronica Centrum (IMEC) | Device and method for calibrating MIMO systems |
KR100918747B1 (en) * | 2006-02-07 | 2009-09-24 | 삼성전자주식회사 | Apparatus and method for transmitting uplink signal in mobile communication system using an orthogonal frequency division multiple access scheme |
US9083355B2 (en) | 2006-02-24 | 2015-07-14 | Qualcomm Incorporated | Method and apparatus for end node assisted neighbor discovery |
JP4776565B2 (en) * | 2006-02-28 | 2011-09-21 | パナソニック株式会社 | Wireless communication system, wireless communication apparatus, and channel correlation matrix determination method |
US8543070B2 (en) | 2006-04-24 | 2013-09-24 | Qualcomm Incorporated | Reduced complexity beam-steered MIMO OFDM system |
US8290089B2 (en) * | 2006-05-22 | 2012-10-16 | Qualcomm Incorporated | Derivation and feedback of transmit steering matrix |
JP5133346B2 (en) * | 2006-09-18 | 2013-01-30 | マーベル ワールド トレード リミテッド | Calibration correction method for implicit beamforming in wireless MIMO communication system |
US9155008B2 (en) | 2007-03-26 | 2015-10-06 | Qualcomm Incorporated | Apparatus and method of performing a handoff in a communication network |
EP2154802A4 (en) * | 2007-05-29 | 2014-03-26 | Mitsubishi Electric Corp | Calibration method, communication system, frequency control method, and communication device |
US8830818B2 (en) | 2007-06-07 | 2014-09-09 | Qualcomm Incorporated | Forward handover under radio link failure |
US9094173B2 (en) | 2007-06-25 | 2015-07-28 | Qualcomm Incorporated | Recovery from handoff error due to false detection of handoff completion signal at access terminal |
EP2677776B1 (en) * | 2007-08-10 | 2022-08-03 | Fujitsu Limited | Radio base station and mobile station |
US7929918B2 (en) | 2007-08-13 | 2011-04-19 | Samsung Electronics Co., Ltd. | System and method for training the same type of directional antennas that adapts the training sequence length to the number of antennas |
US8014265B2 (en) * | 2007-08-15 | 2011-09-06 | Qualcomm Incorporated | Eigen-beamforming for wireless communication systems |
US8009617B2 (en) * | 2007-08-15 | 2011-08-30 | Qualcomm Incorporated | Beamforming of control information in a wireless communication system |
CN101400117B (en) * | 2007-09-27 | 2011-12-28 | 联想(上海)有限公司 | Downlink channel status information determining method and apparatus, pre-coding method and apparatus |
CN101420704B (en) * | 2007-10-22 | 2010-04-14 | 大唐移动通信设备有限公司 | Method, device and system for covering tunnel in time division duplexing system |
US20090121935A1 (en) * | 2007-11-12 | 2009-05-14 | Samsung Electronics Co., Ltd. | System and method of weighted averaging in the estimation of antenna beamforming coefficients |
US9749022B2 (en) | 2008-02-01 | 2017-08-29 | Marvell World Trade Ltd. | Channel sounding and estimation strategies in MIMO systems |
WO2009099949A2 (en) * | 2008-02-01 | 2009-08-13 | Marvell World Trade Ltd. | Channel sounding and estimation strategies for antenna selection in mimo systems |
CN101604991B (en) * | 2008-06-13 | 2013-01-02 | 展讯通信(上海)有限公司 | Method and device for estimating radio-frequency channel parameters in multiple input multiple output (MIMO) system |
US8478204B2 (en) | 2008-07-14 | 2013-07-02 | Samsung Electronics Co., Ltd. | System and method for antenna training of beamforming vectors having reuse of directional information |
US8351872B2 (en) * | 2008-08-11 | 2013-01-08 | Research In Motion Limited | System and method for communicating using an in-vehicle system |
US8437361B2 (en) * | 2009-03-17 | 2013-05-07 | Cisco Technology, Inc. | Adaptive subchannel disabling in beamformed wireless communication systems |
CN101990230A (en) * | 2009-07-30 | 2011-03-23 | 大唐移动通信设备有限公司 | Method and equipment for measuring wireless network communication system |
US8331488B2 (en) | 2009-10-13 | 2012-12-11 | Qualcomm Incorporated | Methods and apparatus for communicating information using non-coherent and coherent modulation |
US8325697B2 (en) * | 2009-10-13 | 2012-12-04 | Qualcomm Incorporated | Methods and apparatus for selecting and transmitting pilots |
US8817687B2 (en) * | 2009-11-06 | 2014-08-26 | Futurewei Technologies, Inc. | System and method for channel estimation in wireless communications systems |
EP2536036A4 (en) * | 2010-02-12 | 2015-07-08 | Alcatel Lucent | Device and method for calibrating reciprocity errors |
US8625631B2 (en) | 2010-04-08 | 2014-01-07 | Ntt Docomo, Inc. | Method and apparatus for pilot-reuse in reciprocity-based training schemes for downlink multi-user MIMO |
US8971210B1 (en) * | 2011-05-23 | 2015-03-03 | Redpine Signals, Inc. | Reconfigurable multi-stream processor for multiple-input multiple-output (MIMO) wireless networks |
US20120300864A1 (en) * | 2011-05-26 | 2012-11-29 | Qualcomm Incorporated | Channel estimation based on combined calibration coefficients |
US8792372B2 (en) * | 2011-06-20 | 2014-07-29 | Xiao-an Wang | Carrier-phase difference detection with mismatched transmitter and receiver delays |
KR102031031B1 (en) * | 2011-06-20 | 2019-10-15 | 삼성전자 주식회사 | Method and apparatus for transmitting and receiving time division duplex frame configuration information in wireless communication system |
US8478203B2 (en) * | 2011-07-31 | 2013-07-02 | Xiao-an Wang | Phase synchronization of base stations via mobile feedback in multipoint broadcasting |
US8891464B2 (en) | 2011-09-19 | 2014-11-18 | Redline Innovations Group, Inc. | Architecture, devices and methods for supporting multiple channels in a wireless system |
US9596676B2 (en) | 2013-02-13 | 2017-03-14 | Qualcomm Incorporated | Calibration of a downlink transmit path of a base station |
CN110035442B (en) | 2013-05-24 | 2022-03-15 | 日本电信电话株式会社 | Wireless communication device and wireless communication method |
US8879659B1 (en) * | 2013-09-03 | 2014-11-04 | Litepoint Corporation | System and method for testing multiple data packet signal transceivers |
WO2015102228A1 (en) * | 2014-01-02 | 2015-07-09 | 엘지전자 주식회사 | Method and apparatus for transmitting uplink frame in wireless lan |
EP3155779B1 (en) * | 2014-06-11 | 2019-10-16 | Marvell World Trade Ltd. | Compressed preamble for a wireless communication system |
US20160050569A1 (en) * | 2014-08-18 | 2016-02-18 | Litepoint Corporation | Method for testing implicit beamforming performance of a multiple-input multiple-output radio frequency data packet signal transceiver |
CN105634696B (en) * | 2014-10-31 | 2019-02-22 | 富士通株式会社 | The Bit distribution method of multicarrier modulated signal, device and system |
EP3238447B1 (en) * | 2014-12-22 | 2021-10-27 | Cyberoptics Corporation | Updating calibration of a three-dimensional measurement system |
CN106160803A (en) * | 2015-03-30 | 2016-11-23 | 北京信威通信技术股份有限公司 | The methods, devices and systems of descending channel information are obtained based on channel reciprocity |
JP2016195331A (en) * | 2015-03-31 | 2016-11-17 | 三星電子株式会社Samsung Electronics Co.,Ltd. | Array antenna transmitter receiver and calibration value calculation method |
GB2539130B (en) * | 2015-06-04 | 2017-10-25 | Imagination Tech Ltd | Channel centering at an OFDM receiver |
WO2017008121A1 (en) * | 2015-07-14 | 2017-01-19 | Commonwealth Scientific And Industrial Research Organisation | Improvements to a multi-user mimo-ofdm system |
US10516449B2 (en) | 2015-07-14 | 2019-12-24 | Commonwealth Scientific And Industrial Research Organisation | Multi-user MIMO-OFDM system |
US9590708B1 (en) * | 2015-08-25 | 2017-03-07 | Motorola Mobility Llc | Method and apparatus for equal energy codebooks for antenna arrays with mutual coupling |
EP3154232B1 (en) * | 2015-10-08 | 2018-04-18 | Alcatel Lucent | Method for channel estimation in a wireless communication system, communication unit, terminal and communication system |
US10439867B2 (en) | 2015-12-31 | 2019-10-08 | At&T Intellectual Property I, L.P. | Method and apparatus for optimizing a software defined network configuration |
EP3479495B1 (en) * | 2016-07-22 | 2023-05-31 | Huawei Technologies Duesseldorf GmbH | Method for obtaining uplink calibration values, calibration method, and corresponding terminal and base station |
CN107104742B (en) * | 2017-04-02 | 2020-11-10 | 上海无线通信研究中心 | Calibration method and system for parallel multi-channel wireless channel measurement |
CN107483090B (en) * | 2017-09-07 | 2020-05-01 | 深圳清华大学研究院 | Large-scale MIMO system precoding realization method based on LDLT decomposition |
RU2700688C1 (en) * | 2018-09-24 | 2019-09-19 | Самсунг Электроникс Ко., Лтд. | Methods for calibrating channels of phased antenna array |
CN111224696B (en) * | 2018-11-26 | 2021-04-20 | 深圳市通用测试系统有限公司 | Wireless performance test method and system for wireless terminal |
US11303425B2 (en) * | 2019-04-23 | 2022-04-12 | Commscope Technologies Llc | Methods and apparatuses for automatic filter identification |
CN113315551B (en) * | 2020-02-27 | 2022-05-10 | 广州海格通信集团股份有限公司 | Signal detection method and device of layered space-time code system and computer equipment |
CN111289135A (en) * | 2020-04-03 | 2020-06-16 | 国家电网有限公司 | Anti-interference RTD measurement circuit |
KR102621660B1 (en) | 2021-11-02 | 2024-01-04 | 강릉원주대학교산학협력단 | Low dielectric loss dielectric ceramic composition for 5G mobile communication component and manufacturing method thereof |
Family Cites Families (476)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA1261080A (en) * | 1985-12-30 | 1989-09-26 | Shunichiro Tejima | Satellite communications system with random multiple access and time slot reservation |
US4750198A (en) | 1986-12-12 | 1988-06-07 | Astronet Corporation/Plessey U.K. | Cellular radiotelephone system providing diverse separately-accessible groups of channels |
US4797879A (en) * | 1987-06-05 | 1989-01-10 | American Telephone And Telegraph Company At&T Bell Laboratories | Packet switched interconnection protocols for a star configured optical lan |
IL100213A (en) | 1990-12-07 | 1995-03-30 | Qualcomm Inc | CDMA microcellular telephone system and distributed antenna system therefor |
US5239677A (en) | 1991-07-01 | 1993-08-24 | Motorola, Inc. | Method and apparatus for initiating communication on an assigned frequency |
IT1250515B (en) | 1991-10-07 | 1995-04-08 | Sixtel Spa | NETWORK FOR LOCAL AREA WITHOUT WIRES. |
US5241544A (en) | 1991-11-01 | 1993-08-31 | Motorola, Inc. | Multi-channel tdm communication system slot phase correction |
US6850252B1 (en) * | 1999-10-05 | 2005-02-01 | Steven M. Hoffberg | Intelligent electronic appliance system and method |
US5295159A (en) * | 1992-04-17 | 1994-03-15 | Bell Communications Research, Inc. | Coordinated coding for digital transmission |
RU2015281C1 (en) | 1992-09-22 | 1994-06-30 | Борис Михайлович Кондрашов | Locking device |
US5404355A (en) * | 1992-10-05 | 1995-04-04 | Ericsson Ge Mobile Communications, Inc. | Method for transmitting broadcast information in a digital control channel |
GB2300337B (en) | 1992-10-05 | 1997-03-26 | Ericsson Ge Mobile Communicat | Digital control channel |
DE69327837T2 (en) * | 1992-12-01 | 2000-10-12 | Koninkl Philips Electronics Nv | Subband diversity transmission system |
US5471647A (en) | 1993-04-14 | 1995-11-28 | The Leland Stanford Junior University | Method for minimizing cross-talk in adaptive transmission antennas |
US5479447A (en) | 1993-05-03 | 1995-12-26 | The Board Of Trustees Of The Leland Stanford, Junior University | Method and apparatus for adaptive, variable bandwidth, high-speed data transmission of a multicarrier signal over digital subscriber lines |
US5483667A (en) | 1993-07-08 | 1996-01-09 | Northern Telecom Limited | Frequency plan for a cellular network |
DE69423546T2 (en) * | 1993-07-09 | 2000-09-21 | Koninkl Philips Electronics Nv | Telecommunication network, master station and slave station for use in such a network |
US5506861A (en) * | 1993-11-22 | 1996-04-09 | Ericsson Ge Mobile Comminications Inc. | System and method for joint demodulation of CDMA signals |
US5490087A (en) | 1993-12-06 | 1996-02-06 | Motorola, Inc. | Radio channel access control |
US5422733A (en) | 1994-02-04 | 1995-06-06 | Motorola, Inc. | Method and apparatus for facsimile communication of first and second type information with selective call communication systems |
US5491837A (en) | 1994-03-07 | 1996-02-13 | Ericsson Inc. | Method and system for channel allocation using power control and mobile-assisted handover measurements |
US5493712A (en) * | 1994-03-23 | 1996-02-20 | At&T Corp. | Fast AGC for TDMA radio systems |
BR9507859A (en) | 1994-05-02 | 1997-09-16 | Motorola Inc | Apparatus and method of flexible registration of multiple subchannels |
US5677909A (en) | 1994-05-11 | 1997-10-14 | Spectrix Corporation | Apparatus for exchanging data between a central station and a plurality of wireless remote stations on a time divided commnication channel |
US6157343A (en) * | 1996-09-09 | 2000-12-05 | Telefonaktiebolaget Lm Ericsson | Antenna array calibration |
DE4425713C1 (en) | 1994-07-20 | 1995-04-20 | Inst Rundfunktechnik Gmbh | Method for multi-carrier modulation and demodulation of digitally coded data |
FR2724084B1 (en) | 1994-08-31 | 1997-01-03 | Alcatel Mobile Comm France | INFORMATION TRANSMISSION SYSTEM VIA A TIME-VARIED TRANSMISSION CHANNEL, AND RELATED TRANSMISSION AND RECEPTION EQUIPMENT |
US5710768A (en) | 1994-09-30 | 1998-01-20 | Qualcomm Incorporated | Method of searching for a bursty signal |
MY120873A (en) | 1994-09-30 | 2005-12-30 | Qualcomm Inc | Multipath search processor for a spread spectrum multiple access communication system |
ES2103190B1 (en) * | 1994-11-30 | 1998-04-01 | Alcatel Standard Electrica | GAS ALIGNMENT PROCEDURE. |
JP3231575B2 (en) | 1995-04-18 | 2001-11-26 | 三菱電機株式会社 | Wireless data transmission equipment |
KR0155818B1 (en) | 1995-04-29 | 1998-11-16 | 김광호 | Power distribution method and apparatus in multi-carrier transmitting system |
US5606729A (en) * | 1995-06-21 | 1997-02-25 | Motorola, Inc. | Method and apparatus for implementing a received signal quality measurement in a radio communication system |
US5729542A (en) * | 1995-06-28 | 1998-03-17 | Motorola, Inc. | Method and apparatus for communication system access |
US7929498B2 (en) | 1995-06-30 | 2011-04-19 | Interdigital Technology Corporation | Adaptive forward power control and adaptive reverse power control for spread-spectrum communications |
US5638369A (en) | 1995-07-05 | 1997-06-10 | Motorola, Inc. | Method and apparatus for inbound channel selection in a communication system |
DE69535033T2 (en) | 1995-07-11 | 2007-03-08 | Alcatel | Allocation of capacity in OFDM |
GB9514659D0 (en) | 1995-07-18 | 1995-09-13 | Northern Telecom Ltd | An antenna downlink beamsteering arrangement |
US5867539A (en) * | 1995-07-21 | 1999-02-02 | Hitachi America, Ltd. | Methods and apparatus for reducing the effect of impulse noise on receivers |
JP2802255B2 (en) | 1995-09-06 | 1998-09-24 | 株式会社次世代デジタルテレビジョン放送システム研究所 | Orthogonal frequency division multiplexing transmission system and transmission device and reception device using the same |
GB9521739D0 (en) | 1995-10-24 | 1996-01-03 | Nat Transcommunications Ltd | Decoding carriers encoded using orthogonal frequency division multiplexing |
US6005876A (en) | 1996-03-08 | 1999-12-21 | At&T Corp | Method and apparatus for mobile data communication |
US5699365A (en) | 1996-03-27 | 1997-12-16 | Motorola, Inc. | Apparatus and method for adaptive forward error correction in data communications |
US5924015A (en) | 1996-04-30 | 1999-07-13 | Trw Inc | Power control method and apparatus for satellite based telecommunications system |
JPH09307526A (en) | 1996-05-17 | 1997-11-28 | Mitsubishi Electric Corp | Digital broadcast receiver |
EP0807989B1 (en) | 1996-05-17 | 2001-06-27 | Motorola Ltd | Devices for transmitter path weights and methods therefor |
US5822374A (en) | 1996-06-07 | 1998-10-13 | Motorola, Inc. | Method for fine gains adjustment in an ADSL communications system |
FI101920B1 (en) | 1996-06-07 | 1998-09-15 | Nokia Telecommunications Oy | Channel reservation method for packet network |
US6798735B1 (en) | 1996-06-12 | 2004-09-28 | Aware, Inc. | Adaptive allocation for variable bandwidth multicarrier communication |
US6072779A (en) | 1997-06-12 | 2000-06-06 | Aware, Inc. | Adaptive allocation for variable bandwidth multicarrier communication |
US6097771A (en) | 1996-07-01 | 2000-08-01 | Lucent Technologies Inc. | Wireless communications system having a layered space-time architecture employing multi-element antennas |
JPH1051402A (en) | 1996-08-01 | 1998-02-20 | Nec Corp | Reception electric field detection circuit |
EP0931388B1 (en) | 1996-08-29 | 2003-11-05 | Cisco Technology, Inc. | Spatio-temporal processing for communication |
JP2001359152A (en) | 2000-06-14 | 2001-12-26 | Sony Corp | Radio communication system and radio base station device and radio mobile station device and radio zone assigning method and radio communication method |
JP2846860B2 (en) | 1996-10-01 | 1999-01-13 | ユニデン株式会社 | Transmitter, receiver, communication system and communication method using spread spectrum communication system |
US6275543B1 (en) | 1996-10-11 | 2001-08-14 | Arraycomm, Inc. | Method for reference signal generation in the presence of frequency offsets in a communications station with spatial processing |
US5886988A (en) | 1996-10-23 | 1999-03-23 | Arraycomm, Inc. | Channel assignment and call admission control for spatial division multiple access communication systems |
US6049548A (en) * | 1996-11-22 | 2000-04-11 | Stanford Telecommunications, Inc. | Multi-access CS-P/CD-E system and protocols on satellite channels applicable to a group of mobile users in close proximity |
IL130034A (en) | 1996-11-26 | 2003-04-10 | Trw Inc | Cochannel signal processing system |
US6232918B1 (en) | 1997-01-08 | 2001-05-15 | Us Wireless Corporation | Antenna array calibration in wireless communication systems |
US6128276A (en) | 1997-02-24 | 2000-10-03 | Radix Wireless, Inc. | Stacked-carrier discrete multiple tone communication technology and combinations with code nulling, interference cancellation, retrodirective communication and adaptive antenna arrays |
US6084915A (en) | 1997-03-03 | 2000-07-04 | 3Com Corporation | Signaling method having mixed-base shell map indices |
US6175550B1 (en) | 1997-04-01 | 2001-01-16 | Lucent Technologies, Inc. | Orthogonal frequency division multiplexing system with dynamically scalable operating parameters and method thereof |
KR100267856B1 (en) | 1997-04-16 | 2000-10-16 | 윤종용 | Over head channel management method an apparatus in mobile communication system |
US6308080B1 (en) | 1997-05-16 | 2001-10-23 | Texas Instruments Incorporated | Power control in point-to-multipoint systems |
US6008760A (en) | 1997-05-23 | 1999-12-28 | Genghis Comm | Cancellation system for frequency reuse in microwave communications |
FR2764143A1 (en) | 1997-05-27 | 1998-12-04 | Philips Electronics Nv | METHOD FOR DETERMINING A SYMBOL TRANSMISSION FORMAT IN A TRANSMISSION SYSTEM AND SYSTEM |
US5867478A (en) * | 1997-06-20 | 1999-02-02 | Motorola, Inc. | Synchronous coherent orthogonal frequency division multiplexing system, method, software and device |
US6067458A (en) | 1997-07-01 | 2000-05-23 | Qualcomm Incorporated | Method and apparatus for pre-transmission power control using lower rate for high rate communication |
US6333953B1 (en) | 1997-07-21 | 2001-12-25 | Ericsson Inc. | System and methods for selecting an appropriate detection technique in a radiocommunication system |
EP0895387A1 (en) | 1997-07-28 | 1999-02-03 | Deutsche Thomson-Brandt Gmbh | Detection of the transmission mode of a DVB signal |
US6141542A (en) | 1997-07-31 | 2000-10-31 | Motorola, Inc. | Method and apparatus for controlling transmit diversity in a communication system |
CN1086061C (en) | 1997-08-12 | 2002-06-05 | 鸿海精密工业股份有限公司 | Fixture for electric connector |
JP2991167B2 (en) | 1997-08-27 | 1999-12-20 | 三菱電機株式会社 | TDMA variable slot allocation method |
EP0899896A1 (en) | 1997-08-27 | 1999-03-03 | Siemens Aktiengesellschaft | Method and system to estimate spatial parameters of transmission channels |
US6131016A (en) | 1997-08-27 | 2000-10-10 | At&T Corp | Method and apparatus for enhancing communication reception at a wireless communication terminal |
US6167031A (en) | 1997-08-29 | 2000-12-26 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for selecting a combination of modulation and channel coding schemes in a digital communication system |
BR9812816A (en) | 1997-09-15 | 2000-08-08 | Adaptive Telecom Inc | Processes for wireless communication, and to efficiently determine a space channel of the mobile unit in a wireless communication system at the base station, and cdma base station |
US6590928B1 (en) | 1997-09-17 | 2003-07-08 | Telefonaktiebolaget Lm Ericsson (Publ) | Frequency hopping piconets in an uncoordinated wireless multi-user system |
AUPO932297A0 (en) | 1997-09-19 | 1997-10-09 | Commonwealth Scientific And Industrial Research Organisation | Medium access control protocol for data communications |
KR100234329B1 (en) | 1997-09-30 | 1999-12-15 | 윤종용 | FFT window position recovery apparatus for OFDM system receiver and method thereof |
US6178196B1 (en) * | 1997-10-06 | 2001-01-23 | At&T Corp. | Combined interference cancellation and maximum likelihood decoding of space-time block codes |
US6574211B2 (en) | 1997-11-03 | 2003-06-03 | Qualcomm Incorporated | Method and apparatus for high rate packet data transmission |
US6377812B1 (en) * | 1997-11-20 | 2002-04-23 | University Of Maryland | Combined power control and space-time diversity in mobile cellular communications |
US6122247A (en) | 1997-11-24 | 2000-09-19 | Motorola Inc. | Method for reallocating data in a discrete multi-tone communication system |
US5936569A (en) | 1997-12-02 | 1999-08-10 | Nokia Telecommunications Oy | Method and arrangement for adjusting antenna pattern |
US6154661A (en) | 1997-12-10 | 2000-11-28 | Arraycomm, Inc. | Transmitting on the downlink using one or more weight vectors determined to achieve a desired radiation pattern |
US6084917A (en) * | 1997-12-16 | 2000-07-04 | Integrated Telecom Express | Circuit for configuring and dynamically adapting data and energy parameters in a multi-channel communications system |
US6175588B1 (en) | 1997-12-30 | 2001-01-16 | Motorola, Inc. | Communication device and method for interference suppression using adaptive equalization in a spread spectrum communication system |
US6088387A (en) | 1997-12-31 | 2000-07-11 | At&T Corp. | Multi-channel parallel/serial concatenated convolutional codes and trellis coded modulation encoder/decoder |
EP0929172B1 (en) | 1998-01-06 | 2010-06-02 | MOSAID Technologies Inc. | Multicarrier modulation system, with variable symbol rates |
US5982327A (en) | 1998-01-12 | 1999-11-09 | Motorola, Inc. | Adaptive array method, device, base station and subscriber unit |
US6608874B1 (en) | 1998-01-12 | 2003-08-19 | Hughes Electronics Corporation | Method and apparatus for quadrature multi-pulse modulation of data for spectrally efficient communication |
US5973638A (en) * | 1998-01-30 | 1999-10-26 | Micronetics Wireless, Inc. | Smart antenna channel simulator and test system |
EP0938208A1 (en) * | 1998-02-22 | 1999-08-25 | Sony International (Europe) GmbH | Multicarrier transmission, compatible with the existing GSM system |
WO1999044379A1 (en) | 1998-02-27 | 1999-09-02 | Telefonaktiebolaget Lm Ericsson (Publ) | Multiple access categorization for mobile station |
JP3082756B2 (en) | 1998-02-27 | 2000-08-28 | 日本電気株式会社 | Multi-carrier transmission system and method |
US6141388A (en) | 1998-03-11 | 2000-10-31 | Ericsson Inc. | Received signal quality determination method and systems for convolutionally encoded communication channels |
US6058107A (en) | 1998-04-08 | 2000-05-02 | Motorola, Inc. | Method for updating forward power control in a communication system |
US6317466B1 (en) | 1998-04-15 | 2001-11-13 | Lucent Technologies Inc. | Wireless communications system having a space-time architecture employing multi-element antennas at both the transmitter and receiver |
US6615024B1 (en) * | 1998-05-01 | 2003-09-02 | Arraycomm, Inc. | Method and apparatus for determining signatures for calibrating a communication station having an antenna array |
US7123628B1 (en) | 1998-05-06 | 2006-10-17 | Lg Electronics Inc. | Communication system with improved medium access control sub-layer |
US6205410B1 (en) * | 1998-06-01 | 2001-03-20 | Globespan Semiconductor, Inc. | System and method for bit loading with optimal margin assignment |
DE69937828D1 (en) | 1998-06-19 | 2008-02-07 | Ericsson Telefon Ab L M | FRAME SYNCHRONIZATION METHOD AND DEVICES |
US6795424B1 (en) * | 1998-06-30 | 2004-09-21 | Tellabs Operations, Inc. | Method and apparatus for interference suppression in orthogonal frequency division multiplexed (OFDM) wireless communication systems |
JP2000092009A (en) | 1998-07-13 | 2000-03-31 | Sony Corp | Communication method, transmitter and receiver |
AU4934399A (en) * | 1998-07-16 | 2000-02-07 | Samsung Electronics Co., Ltd. | Processing packet data in mobile communication system |
US6154443A (en) | 1998-08-11 | 2000-11-28 | Industrial Technology Research Institute | FFT-based CDMA RAKE receiver system and method |
CN1237746C (en) | 1998-08-18 | 2006-01-18 | 束达网络公司 | Stacked-carrier discrete multiple tone communication technology |
KR100429540B1 (en) | 1998-08-26 | 2004-08-09 | 삼성전자주식회사 | Packet data communication apparatus and method of mobile communication system |
US6515617B1 (en) * | 1998-09-01 | 2003-02-04 | Hughes Electronics Corporation | Method and system for position determination using geostationary earth orbit satellite |
DE19842712C1 (en) * | 1998-09-17 | 2000-05-04 | Siemens Ag | Correlation error correction procedure for signal demodulator, involves computing difference between primary and secondary phase values of spreading signals, to compute phase value of local signal |
US6292917B1 (en) | 1998-09-30 | 2001-09-18 | Agere Systems Guardian Corp. | Unequal error protection for digital broadcasting using channel classification |
EP0993211B1 (en) | 1998-10-05 | 2005-01-12 | Sony International (Europe) GmbH | Random access channel partitioning scheme for CDMA system |
EP0993212B1 (en) * | 1998-10-05 | 2006-05-24 | Sony Deutschland GmbH | Random access channel partitioning scheme for CDMA system |
US6711121B1 (en) | 1998-10-09 | 2004-03-23 | At&T Corp. | Orthogonal code division multiplexing for twisted pair channels |
DE59902484D1 (en) * | 1998-10-27 | 2002-10-02 | Siemens Ag | CHANNEL ASSIGNMENT METHOD AND DEVICE FOR CODED AND COMBINED INFORMATION SETS |
JP4287536B2 (en) * | 1998-11-06 | 2009-07-01 | パナソニック株式会社 | OFDM transmitter / receiver and OFDM transmitter / receiver method |
ES2185244T3 (en) | 1998-12-03 | 2003-04-16 | Fraunhofer Ges Forschung | APPARATUS AND PROCEDURE TO TRANSMIT INFORMATION AND APPLIANCE AND PROCEDURE TO RECEIVE INFORMATION. |
GB9827182D0 (en) * | 1998-12-10 | 1999-02-03 | Philips Electronics Nv | Radio communication system |
FI108588B (en) | 1998-12-15 | 2002-02-15 | Nokia Corp | Method and radio system for transmitting a digital signal |
JP2000244441A (en) | 1998-12-22 | 2000-09-08 | Matsushita Electric Ind Co Ltd | Ofdm transmitter-receiver |
US6310909B1 (en) * | 1998-12-23 | 2001-10-30 | Broadcom Corporation | DSL rate adaptation |
US6266528B1 (en) * | 1998-12-23 | 2001-07-24 | Arraycomm, Inc. | Performance monitor for antenna arrays |
US6463290B1 (en) | 1999-01-08 | 2002-10-08 | Trueposition, Inc. | Mobile-assisted network based techniques for improving accuracy of wireless location system |
US6348036B1 (en) | 1999-01-24 | 2002-02-19 | Genzyme Corporation | Surgical retractor and tissue stabilization device |
RU2152132C1 (en) | 1999-01-26 | 2000-06-27 | Государственное унитарное предприятие Воронежский научно-исследовательский институт связи | Radio communication line with three- dimensional modulation |
JP3619729B2 (en) | 2000-01-19 | 2005-02-16 | 松下電器産業株式会社 | Radio receiving apparatus and radio receiving method |
KR100651457B1 (en) | 1999-02-13 | 2006-11-28 | 삼성전자주식회사 | Method of contiguous outer loop power control in dtx mode of cdma mobile communication system |
US6574267B1 (en) | 1999-03-22 | 2003-06-03 | Golden Bridge Technology, Inc. | Rach ramp-up acknowledgement |
US6346910B1 (en) * | 1999-04-07 | 2002-02-12 | Tei Ito | Automatic array calibration scheme for wireless point-to-multipoint communication networks |
US6363267B1 (en) | 1999-04-07 | 2002-03-26 | Telefonaktiebolaget Lm Ericsson (Publ) | Mobile terminal decode failure procedure in a wireless local area network |
IL145548A0 (en) | 1999-04-12 | 2002-06-30 | Samsung Electronics Co Ltd | Apparatus and method for gated transmission in a cdma communication system |
EP1075093A1 (en) | 1999-08-02 | 2001-02-07 | Interuniversitair Micro-Elektronica Centrum Vzw | A method and apparatus for multi-user transmission |
US6594798B1 (en) | 1999-05-21 | 2003-07-15 | Microsoft Corporation | Receiver-driven layered error correction multicast over heterogeneous packet networks |
US6532562B1 (en) * | 1999-05-21 | 2003-03-11 | Microsoft Corp | Receiver-driven layered error correction multicast over heterogeneous packet networks |
US6594473B1 (en) | 1999-05-28 | 2003-07-15 | Texas Instruments Incorporated | Wireless system with transmitter having multiple transmit antennas and combining open loop and closed loop transmit diversities |
KR100605978B1 (en) | 1999-05-29 | 2006-07-28 | 삼성전자주식회사 | Transceiver apparatus and method for continuous outer loop power control in dtx mode of cdma mobile communication system |
US7072410B1 (en) * | 1999-06-01 | 2006-07-04 | Peter Monsen | Multiple access system and method for multibeam digital radio systems |
US6141567A (en) | 1999-06-07 | 2000-10-31 | Arraycomm, Inc. | Apparatus and method for beamforming in a changing-interference environment |
US6385264B1 (en) | 1999-06-08 | 2002-05-07 | Qualcomm Incorporated | Method and apparatus for mitigating interference between base stations in a wideband CDMA system |
US6976262B1 (en) | 1999-06-14 | 2005-12-13 | Sun Microsystems, Inc. | Web-based enterprise management with multiple repository capability |
WO2001005067A1 (en) | 1999-07-08 | 2001-01-18 | Samsung Electronics Co., Ltd | Data rate detection device and method for a mobile communication system |
US6163296A (en) | 1999-07-12 | 2000-12-19 | Lockheed Martin Corp. | Calibration and integrated beam control/conditioning system for phased-array antennas |
RU2168278C2 (en) | 1999-07-16 | 2001-05-27 | Корпорация "Самсунг Электроникс" | Process of unrestricted access of subscribers of mobile station |
US6532225B1 (en) * | 1999-07-27 | 2003-03-11 | At&T Corp | Medium access control layer for packetized wireless systems |
US6067290A (en) | 1999-07-30 | 2000-05-23 | Gigabit Wireless, Inc. | Spatial multiplexing in a cellular network |
JP2001044930A (en) | 1999-07-30 | 2001-02-16 | Matsushita Electric Ind Co Ltd | Device and method for radio communication |
US6735188B1 (en) | 1999-08-27 | 2004-05-11 | Tachyon, Inc. | Channel encoding and decoding method and apparatus |
US6278726B1 (en) * | 1999-09-10 | 2001-08-21 | Interdigital Technology Corporation | Interference cancellation in a spread spectrum communication system |
US6115406A (en) | 1999-09-10 | 2000-09-05 | Interdigital Technology Corporation | Transmission using an antenna array in a CDMA communication system |
US6426971B1 (en) | 1999-09-13 | 2002-07-30 | Qualcomm Incorporated | System and method for accurately predicting signal to interference and noise ratio to improve communications system performance |
SG80071A1 (en) * | 1999-09-24 | 2001-04-17 | Univ Singapore | Downlink beamforming method |
JP3421671B2 (en) | 1999-09-30 | 2003-06-30 | 独立行政法人通信総合研究所 | Communication system, selection device, transmission device, reception device, selection method, transmission method, reception method, and information recording medium |
KR100429529B1 (en) | 1999-10-02 | 2004-05-03 | 삼성전자주식회사 | Apparatus and method for gating data on a control channel in a cdma communication system |
DE19950005A1 (en) | 1999-10-18 | 2001-04-19 | Bernhard Walke | Range enhancement operating method for mobile radio communications base station uses mobile stations within normal range as relay stations for reaching mobile stations outside normal operating range |
DE19951525C2 (en) | 1999-10-26 | 2002-01-24 | Siemens Ag | Method for calibrating an electronically phased array antenna in radio communication systems |
US6492942B1 (en) | 1999-11-09 | 2002-12-10 | Com Dev International, Inc. | Content-based adaptive parasitic array antenna system |
JP3416597B2 (en) | 1999-11-19 | 2003-06-16 | 三洋電機株式会社 | Wireless base station |
US7088671B1 (en) * | 1999-11-24 | 2006-08-08 | Peter Monsen | Multiple access technique for downlink multibeam digital radio systems |
US7110785B1 (en) | 1999-12-03 | 2006-09-19 | Nortel Networks Limited | Performing power control in a mobile communications system |
US6298092B1 (en) | 1999-12-15 | 2001-10-02 | Iospan Wireless, Inc. | Methods of controlling communication parameters of wireless systems |
US6351499B1 (en) * | 1999-12-15 | 2002-02-26 | Iospan Wireless, Inc. | Method and wireless systems using multiple antennas and adaptive control for maximizing a communication parameter |
EP1109326A1 (en) | 1999-12-15 | 2001-06-20 | Lucent Technologies Inc. | Peamble detector for a CDMA receiver |
JP3975629B2 (en) * | 1999-12-16 | 2007-09-12 | ソニー株式会社 | Image decoding apparatus and image decoding method |
US6298035B1 (en) | 1999-12-21 | 2001-10-02 | Nokia Networks Oy | Estimation of two propagation channels in OFDM |
JP2001186051A (en) | 1999-12-24 | 2001-07-06 | Toshiba Corp | Data signal discrimination circuit and method |
AU755728B2 (en) | 1999-12-28 | 2002-12-19 | Ntt Docomo, Inc. | Path search method, channel estimating method and communications device |
US6718160B2 (en) | 1999-12-29 | 2004-04-06 | Airnet Communications Corp. | Automatic configuration of backhaul and groundlink frequencies in a wireless repeater |
US6888809B1 (en) | 2000-01-13 | 2005-05-03 | Lucent Technologies Inc. | Space-time processing for multiple-input, multiple-output, wireless systems |
US7254171B2 (en) * | 2000-01-20 | 2007-08-07 | Nortel Networks Limited | Equaliser for digital communications systems and method of equalisation |
JP3581072B2 (en) * | 2000-01-24 | 2004-10-27 | 株式会社エヌ・ティ・ティ・ドコモ | Channel configuration method and base station using the method |
KR100325367B1 (en) | 2000-01-28 | 2002-03-04 | 박태진 | Apparatus for estimating bit error rate in orthogonal frequency division multiplexing communication system and mothod thereof |
JP2001217896A (en) | 2000-01-31 | 2001-08-10 | Matsushita Electric Works Ltd | Wireless data communication system |
US7003044B2 (en) * | 2000-02-01 | 2006-02-21 | Sasken Communication Technologies Ltd. | Method for allocating bits and power in multi-carrier communication system |
FI117465B (en) | 2000-02-03 | 2006-10-31 | Danisco Sweeteners Oy | Procedure for hard coating of chewable cores |
US6868120B2 (en) * | 2000-02-08 | 2005-03-15 | Clearwire Corporation | Real-time system for measuring the Ricean K-factor |
US6704374B1 (en) | 2000-02-16 | 2004-03-09 | Thomson Licensing S.A. | Local oscillator frequency correction in an orthogonal frequency division multiplexing system |
DE10008653A1 (en) * | 2000-02-24 | 2001-09-06 | Siemens Ag | Improvements in a radio communication system |
US6956814B1 (en) | 2000-02-29 | 2005-10-18 | Worldspace Corporation | Method and apparatus for mobile platform reception and synchronization in direct digital satellite broadcast system |
JP2001244879A (en) | 2000-03-02 | 2001-09-07 | Matsushita Electric Ind Co Ltd | Transmission power control unit and its method |
EP1137217A1 (en) | 2000-03-20 | 2001-09-26 | Telefonaktiebolaget Lm Ericsson | ARQ parameter negociation in a data packet transmission system using link adaptation |
US20020154705A1 (en) | 2000-03-22 | 2002-10-24 | Walton Jay R. | High efficiency high performance communications system employing multi-carrier modulation |
US6952454B1 (en) | 2000-03-22 | 2005-10-04 | Qualcomm, Incorporated | Multiplexing of real time services and non-real time services for OFDM systems |
US6473467B1 (en) | 2000-03-22 | 2002-10-29 | Qualcomm Incorporated | Method and apparatus for measuring reporting channel state information in a high efficiency, high performance communications system |
DE10014676C2 (en) | 2000-03-24 | 2002-02-07 | Polytrax Inf Technology Ag | Data transmission over a power supply network |
US7113499B2 (en) | 2000-03-29 | 2006-09-26 | Texas Instruments Incorporated | Wireless communication |
DE60035335T2 (en) | 2000-04-04 | 2008-03-13 | Sony Deutschland Gmbh | Event-driven change of the access service class in a random access channel |
DE60021772T2 (en) * | 2000-04-07 | 2006-04-20 | Nokia Corp. | METHOD AND DEVICE FOR TRANSMITTING WITH SEVERAL ANTENNAS |
US7289570B2 (en) | 2000-04-10 | 2007-10-30 | Texas Instruments Incorporated | Wireless communications |
US6757263B1 (en) | 2000-04-13 | 2004-06-29 | Motorola, Inc. | Wireless repeating subscriber units |
ATE513401T1 (en) * | 2000-04-18 | 2011-07-15 | Aware Inc | MULTI CARRIER SYSTEM WITH A MULTIPLE SNR SPACING |
US6751199B1 (en) | 2000-04-24 | 2004-06-15 | Qualcomm Incorporated | Method and apparatus for a rate control in a high data rate communication system |
JP3414357B2 (en) | 2000-04-25 | 2003-06-09 | 日本電気株式会社 | Transmission power control method in CDMA mobile communication system |
EP1455493B1 (en) | 2000-04-25 | 2005-11-30 | Nortel Networks Limited | Radio telecommunications system with reduced delays for data transmission |
US7068628B2 (en) | 2000-05-22 | 2006-06-27 | At&T Corp. | MIMO OFDM system |
US7139324B1 (en) | 2000-06-02 | 2006-11-21 | Nokia Networks Oy | Closed loop feedback system for improved down link performance |
US6744811B1 (en) | 2000-06-12 | 2004-06-01 | Actelis Networks Inc. | Bandwidth management for DSL modem pool |
WO2001097411A1 (en) | 2000-06-12 | 2001-12-20 | Samsung Electronics Co., Ltd | Method of assigning an uplink random access channel in a cdma mobile communication system |
US7248841B2 (en) * | 2000-06-13 | 2007-07-24 | Agee Brian G | Method and apparatus for optimization of wireless multipoint electromagnetic communication networks |
US6628702B1 (en) | 2000-06-14 | 2003-09-30 | Qualcomm, Incorporated | Method and apparatus for demodulating signals processed in a transmit diversity mode |
US6760313B1 (en) | 2000-06-19 | 2004-07-06 | Qualcomm Incorporated | Method and apparatus for adaptive rate selection in a communication system |
SE519303C2 (en) | 2000-06-20 | 2003-02-11 | Ericsson Telefon Ab L M | Device for narrowband communication in a multicarrier system |
US6891858B1 (en) * | 2000-06-30 | 2005-05-10 | Cisco Technology Inc. | Dynamic modulation of modulation profiles for communication channels in an access network |
WO2002003557A1 (en) | 2000-06-30 | 2002-01-10 | Iospan Wireless, Inc. | Method and system for mode adaptation in wireless communication |
CN1140147C (en) * | 2000-07-01 | 2004-02-25 | 信息产业部电信传输研究所 | Method and system of outer loop power control |
WO2002003573A1 (en) * | 2000-07-03 | 2002-01-10 | Matsushita Electric Industrial Co., Ltd. | Base station unit and method for radio communication |
EP2262151B1 (en) | 2000-07-05 | 2017-10-04 | Sony Deutschland Gmbh | Pilot pattern design for multiple antennas in an OFDM system |
FI109393B (en) | 2000-07-14 | 2002-07-15 | Nokia Corp | Method for encoding media stream, a scalable and a terminal |
WO2002007327A1 (en) | 2000-07-17 | 2002-01-24 | Koninklijke Philips Electronics N.V. | Coding of data stream |
KR100493152B1 (en) | 2000-07-21 | 2005-06-02 | 삼성전자주식회사 | Transmission antenna diversity method, base station apparatus and mobile station apparatus therefor in mobile communication system |
EP1176750A1 (en) * | 2000-07-25 | 2002-01-30 | Telefonaktiebolaget L M Ericsson (Publ) | Link quality determination of a transmission link in an OFDM transmission system |
EP1178641B1 (en) | 2000-08-01 | 2007-07-25 | Sony Deutschland GmbH | Frequency reuse scheme for OFDM systems |
ATE446663T1 (en) | 2000-08-03 | 2009-11-15 | Infineon Technologies Ag | DYNAMIC, RECONFIGURABLE, UNIVERSAL TRANSMITTER SYSTEM |
US6920192B1 (en) | 2000-08-03 | 2005-07-19 | Lucent Technologies Inc. | Adaptive antenna array methods and apparatus for use in a multi-access wireless communication system |
DE60037465T2 (en) | 2000-08-10 | 2008-12-04 | Fujitsu Ltd., Kawasaki | Device for communicating with diversity |
US6582088B2 (en) * | 2000-08-10 | 2003-06-24 | Benq Corporation | Optical path folding apparatus |
KR100526499B1 (en) * | 2000-08-22 | 2005-11-08 | 삼성전자주식회사 | Apparatus for transmit diversity for more than two antennas and method thereof |
EP1182799A3 (en) | 2000-08-22 | 2002-06-26 | Lucent Technologies Inc. | Method for enhancing mobile cdma communications using space-time transmit diversity |
IT1318790B1 (en) | 2000-08-29 | 2003-09-10 | Cit Alcatel | METHOD TO MANAGE THE TIME-SLOT ALLOCATION CHANGE IN ADANELLO MS-SPRING NETWORKS OF TRANSOCEANIC TYPE. |
US6985434B2 (en) | 2000-09-01 | 2006-01-10 | Nortel Networks Limited | Adaptive time diversity and spatial diversity for OFDM |
US6850481B2 (en) | 2000-09-01 | 2005-02-01 | Nortel Networks Limited | Channels estimation for multiple input—multiple output, orthogonal frequency division multiplexing (OFDM) system |
US7009931B2 (en) * | 2000-09-01 | 2006-03-07 | Nortel Networks Limited | Synchronization in a multiple-input/multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system for wireless applications |
US6937592B1 (en) | 2000-09-01 | 2005-08-30 | Intel Corporation | Wireless communications system that supports multiple modes of operation |
US7233625B2 (en) | 2000-09-01 | 2007-06-19 | Nortel Networks Limited | Preamble design for multiple input—multiple output (MIMO), orthogonal frequency division multiplexing (OFDM) system |
FR2814014B1 (en) | 2000-09-14 | 2002-10-11 | Mitsubishi Electric Inf Tech | MULTI-USER DETECTION METHOD |
US6802035B2 (en) * | 2000-09-19 | 2004-10-05 | Intel Corporation | System and method of dynamically optimizing a transmission mode of wirelessly transmitted information |
US6760882B1 (en) | 2000-09-19 | 2004-07-06 | Intel Corporation | Mode selection for data transmission in wireless communication channels based on statistical parameters |
US6650714B2 (en) | 2000-11-30 | 2003-11-18 | Arraycomm, Inc. | Spatial processing and timing estimation using a training sequence in a radio communications system |
US7062294B1 (en) | 2000-09-29 | 2006-06-13 | Arraycomm, Llc. | Downlink transmission in a wireless data communication system having a base station with a smart antenna system |
US7110378B2 (en) | 2000-10-03 | 2006-09-19 | Wisconsin Alumni Research Foundation | Channel aware optimal space-time signaling for wireless communication over wideband multipath channels |
US7016296B2 (en) | 2000-10-16 | 2006-03-21 | Broadcom Corporation | Adaptive modulation for fixed wireless link in cable transmission system |
US6907270B1 (en) | 2000-10-23 | 2005-06-14 | Qualcomm Inc. | Method and apparatus for reduced rank channel estimation in a communications system |
US6369758B1 (en) | 2000-11-01 | 2002-04-09 | Unique Broadband Systems, Inc. | Adaptive antenna array for mobile communication |
JP3553038B2 (en) | 2000-11-06 | 2004-08-11 | 株式会社エヌ・ティ・ティ・ドコモ | Signal transmission method, signal reception method, transmission device, reception device, and recording medium |
US6768727B1 (en) * | 2000-11-09 | 2004-07-27 | Ericsson Inc. | Fast forward link power control for CDMA system |
US8634481B1 (en) | 2000-11-16 | 2014-01-21 | Alcatel Lucent | Feedback technique for wireless systems with multiple transmit and receive antennas |
US6980601B2 (en) | 2000-11-17 | 2005-12-27 | Broadcom Corporation | Rate adaptation and parameter optimization for multi-band single carrier transmission |
US7006464B1 (en) | 2000-11-17 | 2006-02-28 | Lucent Technologies Inc. | Downlink and uplink channel structures for downlink shared channel system |
JP3695316B2 (en) | 2000-11-24 | 2005-09-14 | 株式会社日本自動車部品総合研究所 | Spread spectrum receiver correlation detector |
US6751480B2 (en) | 2000-12-01 | 2004-06-15 | Lucent Technologies Inc. | Method for simultaneously conveying information to multiple mobiles with multiple antennas |
JP4505677B2 (en) | 2000-12-06 | 2010-07-21 | ソフトバンクテレコム株式会社 | Transmission diversity apparatus and transmission power adjustment method |
US6952426B2 (en) | 2000-12-07 | 2005-10-04 | Nortel Networks Limited | Method and apparatus for the transmission of short data bursts in CDMA/HDR networks |
KR100353641B1 (en) | 2000-12-21 | 2002-09-28 | 삼성전자 주식회사 | Base station transmit antenna diversity apparatus and method in cdma communication system |
US6850498B2 (en) * | 2000-12-22 | 2005-02-01 | Intel Corporation | Method and system for evaluating a wireless link |
US20020085641A1 (en) | 2000-12-29 | 2002-07-04 | Motorola, Inc | Method and system for interference averaging in a wireless communication system |
US7050510B2 (en) | 2000-12-29 | 2006-05-23 | Lucent Technologies Inc. | Open-loop diversity technique for systems employing four transmitter antennas |
US6987819B2 (en) * | 2000-12-29 | 2006-01-17 | Motorola, Inc. | Method and device for multiple input/multiple output transmit and receive weights for equal-rate data streams |
US6731668B2 (en) | 2001-01-05 | 2004-05-04 | Qualcomm Incorporated | Method and system for increased bandwidth efficiency in multiple input—multiple output channels |
EP1223776A1 (en) * | 2001-01-12 | 2002-07-17 | Siemens Information and Communication Networks S.p.A. | A collision free access scheduling in cellular TDMA-CDMA networks |
US6693992B2 (en) * | 2001-01-16 | 2004-02-17 | Mindspeed Technologies | Line probe signal and method of use |
US6801790B2 (en) | 2001-01-17 | 2004-10-05 | Lucent Technologies Inc. | Structure for multiple antenna configurations |
US7164669B2 (en) * | 2001-01-19 | 2007-01-16 | Adaptix, Inc. | Multi-carrier communication with time division multiplexing and carrier-selective loading |
US7054662B2 (en) | 2001-01-24 | 2006-05-30 | Qualcomm, Inc. | Method and system for forward link beam forming in wireless communications |
JP2002232943A (en) | 2001-01-29 | 2002-08-16 | Sony Corp | Data transmission processing method, data reception processing method, transmitter, receiver, and cellular wireless communication system |
GB0102316D0 (en) * | 2001-01-30 | 2001-03-14 | Koninkl Philips Electronics Nv | Radio communication system |
US6961388B2 (en) | 2001-02-01 | 2005-11-01 | Qualcomm, Incorporated | Coding scheme for a wireless communication system |
US6885654B2 (en) * | 2001-02-06 | 2005-04-26 | Interdigital Technology Corporation | Low complexity data detection using fast fourier transform of channel correlation matrix |
US7120134B2 (en) | 2001-02-15 | 2006-10-10 | Qualcomm, Incorporated | Reverse link channel architecture for a wireless communication system |
US6975868B2 (en) | 2001-02-21 | 2005-12-13 | Qualcomm Incorporated | Method and apparatus for IS-95B reverse link supplemental code channel frame validation and fundamental code channel rate decision improvement |
US7006483B2 (en) * | 2001-02-23 | 2006-02-28 | Ipr Licensing, Inc. | Qualifying available reverse link coding rates from access channel power setting |
WO2002069523A1 (en) | 2001-02-26 | 2002-09-06 | Magnolia Broadband, Inc | Smart antenna based spectrum multiplexing using a pilot signal |
GB0105019D0 (en) | 2001-03-01 | 2001-04-18 | Koninkl Philips Electronics Nv | Antenna diversity in a wireless local area network |
US7039125B2 (en) | 2001-03-12 | 2006-05-02 | Analog Devices, Inc. | Equalized SNR power back-off |
EP1241824A1 (en) | 2001-03-14 | 2002-09-18 | TELEFONAKTIEBOLAGET LM ERICSSON (publ) | Multiplexing method in a multicarrier transmit diversity system |
US6763244B2 (en) | 2001-03-15 | 2004-07-13 | Qualcomm Incorporated | Method and apparatus for adjusting power control setpoint in a wireless communication system |
US6478422B1 (en) | 2001-03-19 | 2002-11-12 | Richard A. Hansen | Single bifocal custom shooters glasses |
US7046746B1 (en) | 2001-03-19 | 2006-05-16 | Cisco Systems Wireless Networking (Australia) Pty Limited | Adaptive Viterbi decoder for a wireless data network receiver |
US7248638B1 (en) | 2001-03-23 | 2007-07-24 | Lsi Logic | Transmit antenna multi-mode tracking |
US6771706B2 (en) * | 2001-03-23 | 2004-08-03 | Qualcomm Incorporated | Method and apparatus for utilizing channel state information in a wireless communication system |
US7386076B2 (en) * | 2001-03-29 | 2008-06-10 | Texas Instruments Incorporated | Space time encoded wireless communication system with multipath resolution receivers |
GB2373973B (en) | 2001-03-30 | 2003-06-11 | Toshiba Res Europ Ltd | Adaptive antenna |
US8290098B2 (en) | 2001-03-30 | 2012-10-16 | Texas Instruments Incorporated | Closed loop multiple transmit, multiple receive antenna wireless communication system |
US20020176485A1 (en) | 2001-04-03 | 2002-11-28 | Hudson John E. | Multi-cast communication system and method of estimating channel impulse responses therein |
US6785513B1 (en) * | 2001-04-05 | 2004-08-31 | Cowave Networks, Inc. | Method and system for clustered wireless networks |
US6859503B2 (en) | 2001-04-07 | 2005-02-22 | Motorola, Inc. | Method and system in a transceiver for controlling a multiple-input, multiple-output communications channel |
KR100510434B1 (en) | 2001-04-09 | 2005-08-26 | 니폰덴신뎅와 가부시키가이샤 | OFDM signal transmission system, OFDM signal transmission apparatus and OFDM signal receiver |
FR2823620B1 (en) | 2001-04-12 | 2003-08-15 | France Telecom | METHOD OF ENCODING / DECODING A DIGITAL DATA STREAM ENCODED WITH INTERLOCATION ON BITS IN TRANSMISSION AND IN MULTIPLE RECEPTION IN THE PRESENCE OF INTERSYMBOL INTERFERENCE AND CORRESPONDING SYSTEM |
US7310304B2 (en) | 2001-04-24 | 2007-12-18 | Bae Systems Information And Electronic Systems Integration Inc. | Estimating channel parameters in multi-input, multi-output (MIMO) systems |
US6611231B2 (en) | 2001-04-27 | 2003-08-26 | Vivato, Inc. | Wireless packet switched communication systems and networks using adaptively steered antenna arrays |
US7133459B2 (en) | 2001-05-01 | 2006-11-07 | Texas Instruments Incorporated | Space-time transmit diversity |
EP1255369A1 (en) | 2001-05-04 | 2002-11-06 | TELEFONAKTIEBOLAGET LM ERICSSON (publ) | Link adaptation for wireless MIMO transmission schemes |
CN100446612C (en) | 2001-05-04 | 2008-12-24 | 诺基亚公司 | Admission control with directional antenna |
DE10122788A1 (en) | 2001-05-10 | 2002-06-06 | Basf Ag | Preparation of purified melt of monomer(s) involves forming suspension, crystallizing, mechanically separating suspended monomer crystals and further crystallizing and separating |
US6785341B2 (en) | 2001-05-11 | 2004-08-31 | Qualcomm Incorporated | Method and apparatus for processing data in a multiple-input multiple-output (MIMO) communication system utilizing channel state information |
US6751187B2 (en) * | 2001-05-17 | 2004-06-15 | Qualcomm Incorporated | Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel transmission |
US7072413B2 (en) * | 2001-05-17 | 2006-07-04 | Qualcomm, Incorporated | Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion |
US6718493B1 (en) | 2001-05-17 | 2004-04-06 | 3Com Corporation | Method and apparatus for selection of ARQ parameters and estimation of improved communications |
US7688899B2 (en) * | 2001-05-17 | 2010-03-30 | Qualcomm Incorporated | Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion |
US7492737B1 (en) | 2001-05-23 | 2009-02-17 | Nortel Networks Limited | Service-driven air interface protocol architecture for wireless systems |
ES2188373B1 (en) | 2001-05-25 | 2004-10-16 | Diseño De Sistemas En Silencio, S.A. | COMMUNICATION OPTIMIZATION PROCEDURE FOR MULTI-USER DIGITAL TRANSMISSION SYSTEM ON ELECTRICAL NETWORK. |
US6920194B2 (en) | 2001-05-29 | 2005-07-19 | Tioga Technologies, Ltd. | Method and system for detecting, timing, and correcting impulse noise |
US7158563B2 (en) * | 2001-06-01 | 2007-01-02 | The Board Of Trustees Of The Leland Stanford Junior University | Dynamic digital communication system control |
GB2376315B (en) | 2001-06-05 | 2003-08-06 | 3Com Corp | Data bus system including posted reads and writes |
US20020183010A1 (en) | 2001-06-05 | 2002-12-05 | Catreux Severine E. | Wireless communication systems with adaptive channelization and link adaptation |
US7190749B2 (en) * | 2001-06-06 | 2007-03-13 | Qualcomm Incorporated | Method and apparatus for canceling pilot interference in a wireless communication system |
US20020193146A1 (en) | 2001-06-06 | 2002-12-19 | Mark Wallace | Method and apparatus for antenna diversity in a wireless communication system |
EP1265411B1 (en) | 2001-06-08 | 2007-04-18 | Sony Deutschland GmbH | Multicarrier system with adaptive bit-wise interleaving |
US20030012308A1 (en) * | 2001-06-13 | 2003-01-16 | Sampath Hemanth T. | Adaptive channel estimation for wireless systems |
US7027523B2 (en) * | 2001-06-22 | 2006-04-11 | Qualcomm Incorporated | Method and apparatus for transmitting data in a time division duplexed (TDD) communication system |
US6842460B1 (en) | 2001-06-27 | 2005-01-11 | Nokia Corporation | Ad hoc network discovery menu |
WO2003010984A1 (en) | 2001-06-27 | 2003-02-06 | Nortel Networks Limited | Communication of control information in wireless communication systems |
US6751444B1 (en) | 2001-07-02 | 2004-06-15 | Broadstorm Telecommunications, Inc. | Method and apparatus for adaptive carrier allocation and power control in multi-carrier communication systems |
FR2827731B1 (en) | 2001-07-23 | 2004-01-23 | Nexo | LOUDSPEAKER WITH DIRECT RADIATION AND OPTIMIZED RADIATION |
US6996380B2 (en) * | 2001-07-26 | 2006-02-07 | Ericsson Inc. | Communication system employing transmit macro-diversity |
US6738020B1 (en) | 2001-07-31 | 2004-05-18 | Arraycomm, Inc. | Estimation of downlink transmission parameters in a radio communications system with an adaptive antenna array |
EP1284545B1 (en) | 2001-08-13 | 2008-07-02 | Motorola, Inc. | Transmit diversity wireless communication |
KR100703295B1 (en) | 2001-08-18 | 2007-04-03 | 삼성전자주식회사 | Method and apparatus for transporting and receiving data using antenna array in mobile system |
US20030039317A1 (en) * | 2001-08-21 | 2003-02-27 | Taylor Douglas Hamilton | Method and apparatus for constructing a sub-carrier map |
FR2828981B1 (en) | 2001-08-23 | 2004-05-21 | Commissariat Energie Atomique | INDUCTION HEATING CRUCIBLE AND COOLING |
EP1289328A1 (en) * | 2001-08-28 | 2003-03-05 | Lucent Technologies Inc. | A method of sending control information in a wireless telecommunications network, and corresponding apparatus |
US6990059B1 (en) * | 2001-09-05 | 2006-01-24 | Cisco Technology, Inc. | Interference mitigation in a wireless communication system |
US7149254B2 (en) | 2001-09-06 | 2006-12-12 | Intel Corporation | Transmit signal preprocessing based on transmit antennae correlations for multiple antennae systems |
FR2829326A1 (en) | 2001-09-06 | 2003-03-07 | France Telecom | SUB-OPTIMAL ITERATIVE RECEPTION PROCESS AND SYSTEM FOR CDMA HIGH SPEED TRANSMISSION SYSTEM |
US7133070B2 (en) | 2001-09-20 | 2006-11-07 | Eastman Kodak Company | System and method for deciding when to correct image-specific defects based on camera, scene, display and demographic data |
US7277679B1 (en) | 2001-09-28 | 2007-10-02 | Arraycomm, Llc | Method and apparatus to provide multiple-mode spatial processing to a terminal unit |
US6788948B2 (en) | 2001-09-28 | 2004-09-07 | Arraycomm, Inc. | Frequency dependent calibration of a wideband radio system using narrowband channels |
US7024163B1 (en) | 2001-09-28 | 2006-04-04 | Arraycomm Llc | Method and apparatus for adjusting feedback of a remote unit |
US7035359B2 (en) | 2001-10-11 | 2006-04-25 | Telefonaktiebolaget L.M. Ericsson | Methods and apparatus for demodulation of a signal in a signal slot subject to a discontinuous interference signal |
US7773699B2 (en) * | 2001-10-17 | 2010-08-10 | Nortel Networks Limited | Method and apparatus for channel quality measurements |
US7548506B2 (en) | 2001-10-17 | 2009-06-16 | Nortel Networks Limited | System access and synchronization methods for MIMO OFDM communications systems and physical layer packet and preamble design |
US7248559B2 (en) | 2001-10-17 | 2007-07-24 | Nortel Networks Limited | Scattered pilot pattern and channel estimation method for MIMO-OFDM systems |
US7116652B2 (en) | 2001-10-18 | 2006-10-03 | Lucent Technologies Inc. | Rate control technique for layered architectures with multiple transmit and receive antennas |
KR20030032875A (en) | 2001-10-19 | 2003-04-26 | 삼성전자주식회사 | Apparatus for controlling transmit power of downlink data channel in mobile communication system serving multimedia broadcast/multicast service and method thereof |
US7349667B2 (en) * | 2001-10-19 | 2008-03-25 | Texas Instruments Incorporated | Simplified noise estimation and/or beamforming for wireless communications |
CN1306722C (en) | 2001-10-31 | 2007-03-21 | 松下电器产业株式会社 | Radio transmission apparatus and radio communication method |
US7164649B2 (en) | 2001-11-02 | 2007-01-16 | Qualcomm, Incorporated | Adaptive rate control for OFDM communication system |
US7218684B2 (en) | 2001-11-02 | 2007-05-15 | Interdigital Technology Corporation | Method and system for code reuse and capacity enhancement using null steering |
US20030125040A1 (en) | 2001-11-06 | 2003-07-03 | Walton Jay R. | Multiple-access multiple-input multiple-output (MIMO) communication system |
US8018903B2 (en) | 2001-11-21 | 2011-09-13 | Texas Instruments Incorporated | Closed-loop transmit diversity scheme in frequency selective multipath channels |
CN101150556B (en) | 2001-11-28 | 2015-11-25 | 富士通株式会社 | OFDM transfer method, transmitter and emission system |
US7346126B2 (en) | 2001-11-28 | 2008-03-18 | Telefonaktiebolaget L M Ericsson (Publ) | Method and apparatus for channel estimation using plural channels |
US7263119B1 (en) | 2001-11-29 | 2007-08-28 | Marvell International Ltd. | Decoding method and apparatus |
US7154936B2 (en) | 2001-12-03 | 2006-12-26 | Qualcomm, Incorporated | Iterative detection and decoding for a MIMO-OFDM system |
US6760388B2 (en) * | 2001-12-07 | 2004-07-06 | Qualcomm Incorporated | Time-domain transmit and receive processing with channel eigen-mode decomposition for MIMO systems |
US7155171B2 (en) * | 2001-12-12 | 2006-12-26 | Saraband Wireless | Vector network analyzer applique for adaptive communications in wireless networks |
US20030112745A1 (en) | 2001-12-17 | 2003-06-19 | Xiangyang Zhuang | Method and system of operating a coded OFDM communication system |
US7099398B1 (en) | 2001-12-18 | 2006-08-29 | Vixs, Inc. | Method and apparatus for establishing non-standard data rates in a wireless communication system |
US7076514B2 (en) | 2001-12-18 | 2006-07-11 | Conexant, Inc. | Method and system for computing pre-equalizer coefficients |
JP4052835B2 (en) | 2001-12-28 | 2008-02-27 | 株式会社日立製作所 | Wireless transmission system for multipoint relay and wireless device used therefor |
US7573805B2 (en) | 2001-12-28 | 2009-08-11 | Motorola, Inc. | Data transmission and reception method and apparatus |
CA2366397A1 (en) | 2001-12-31 | 2003-06-30 | Tropic Networks Inc. | An interface for data transfer between integrated circuits |
US7209433B2 (en) | 2002-01-07 | 2007-04-24 | Hitachi, Ltd. | Channel estimation and compensation techniques for use in frequency division multiplexed systems |
US7020110B2 (en) * | 2002-01-08 | 2006-03-28 | Qualcomm Incorporated | Resource allocation for MIMO-OFDM communication systems |
US7020482B2 (en) * | 2002-01-23 | 2006-03-28 | Qualcomm Incorporated | Reallocation of excess power for full channel-state information (CSI) multiple-input, multiple-output (MIMO) systems |
US7058116B2 (en) | 2002-01-25 | 2006-06-06 | Intel Corporation | Receiver architecture for CDMA receiver downlink |
KR100547845B1 (en) | 2002-02-07 | 2006-01-31 | 삼성전자주식회사 | Apparatus and method for transmitting and receiving serving high speed common control channel set information in communication system using high speed forward packet access method |
US7046978B2 (en) | 2002-02-08 | 2006-05-16 | Qualcomm, Inc. | Method and apparatus for transmit pre-correction in wireless communications |
US6980800B2 (en) | 2002-02-12 | 2005-12-27 | Hughes Network Systems | System and method for providing contention channel organization for broadband satellite access in a communications network |
US7292854B2 (en) | 2002-02-15 | 2007-11-06 | Lucent Technologies Inc. | Express signaling in a wireless communication system |
US7076263B2 (en) | 2002-02-19 | 2006-07-11 | Qualcomm, Incorporated | Power control for partial channel-state information (CSI) multiple-input, multiple-output (MIMO) systems |
US20030162519A1 (en) | 2002-02-26 | 2003-08-28 | Martin Smith | Radio communications device |
US6862271B2 (en) * | 2002-02-26 | 2005-03-01 | Qualcomm Incorporated | Multiple-input, multiple-output (MIMO) systems with multiple transmission modes |
US6959171B2 (en) | 2002-02-28 | 2005-10-25 | Intel Corporation | Data transmission rate control |
US6873651B2 (en) * | 2002-03-01 | 2005-03-29 | Cognio, Inc. | System and method for joint maximal ratio combining using time-domain signal processing |
US6636568B2 (en) | 2002-03-01 | 2003-10-21 | Qualcomm | Data transmission with non-uniform distribution of data rates for a multiple-input multiple-output (MIMO) system |
US6687492B1 (en) | 2002-03-01 | 2004-02-03 | Cognio, Inc. | System and method for antenna diversity using joint maximal ratio combining |
US7042858B1 (en) | 2002-03-22 | 2006-05-09 | Jianglei Ma | Soft handoff for OFDM |
JP3561510B2 (en) | 2002-03-22 | 2004-09-02 | 松下電器産業株式会社 | Base station apparatus and packet transmission method |
US20040198276A1 (en) * | 2002-03-26 | 2004-10-07 | Jose Tellado | Multiple channel wireless receiver |
US7012978B2 (en) * | 2002-03-26 | 2006-03-14 | Intel Corporation | Robust multiple chain receiver |
US7197084B2 (en) * | 2002-03-27 | 2007-03-27 | Qualcomm Incorporated | Precoding for a multipath channel in a MIMO system |
KR100456693B1 (en) | 2002-03-28 | 2004-11-10 | 삼성전자주식회사 | Method for minimizing setupt time by the optimization of bit allocation on multi-canannel communication system |
US20030186650A1 (en) | 2002-03-29 | 2003-10-02 | Jung-Tao Liu | Closed loop multiple antenna system |
US7224704B2 (en) | 2002-04-01 | 2007-05-29 | Texas Instruments Incorporated | Wireless network scheduling data frames including physical layer configuration |
US7099377B2 (en) * | 2002-04-03 | 2006-08-29 | Stmicroelectronics N.V. | Method and device for interference cancellation in a CDMA wireless communication system |
US6850741B2 (en) | 2002-04-04 | 2005-02-01 | Agency For Science, Technology And Research | Method for selecting switched orthogonal beams for downlink diversity transmission |
US7103325B1 (en) * | 2002-04-05 | 2006-09-05 | Nortel Networks Limited | Adaptive modulation and coding |
AU2003218506A1 (en) | 2002-04-05 | 2003-10-27 | Flarion Technologies, Inc. | Phase sequences for timing and access signals |
US7623871B2 (en) * | 2002-04-24 | 2009-11-24 | Qualcomm Incorporated | Position determination for a wireless terminal in a hybrid position determination system |
US7876726B2 (en) | 2002-04-29 | 2011-01-25 | Texas Instruments Incorporated | Adaptive allocation of communications link channels to I- or Q-subchannel |
US6690660B2 (en) * | 2002-05-22 | 2004-02-10 | Interdigital Technology Corporation | Adaptive algorithm for a Cholesky approximation |
US7327800B2 (en) * | 2002-05-24 | 2008-02-05 | Vecima Networks Inc. | System and method for data detection in wireless communication systems |
US6862440B2 (en) * | 2002-05-29 | 2005-03-01 | Intel Corporation | Method and system for multiple channel wireless transmitter and receiver phase and amplitude calibration |
US7421039B2 (en) * | 2002-06-04 | 2008-09-02 | Lucent Technologies Inc. | Method and system employing antenna arrays |
KR100498326B1 (en) | 2002-06-18 | 2005-07-01 | 엘지전자 주식회사 | Adaptive modulation coding apparatus and method for mobile communication device |
US7184713B2 (en) * | 2002-06-20 | 2007-02-27 | Qualcomm, Incorporated | Rate control for multi-channel communication systems |
US7613248B2 (en) * | 2002-06-24 | 2009-11-03 | Qualcomm Incorporated | Signal processing with channel eigenmode decomposition and channel inversion for MIMO systems |
US7359313B2 (en) | 2002-06-24 | 2008-04-15 | Agere Systems Inc. | Space-time bit-interleaved coded modulation for wideband transmission |
US7095709B2 (en) | 2002-06-24 | 2006-08-22 | Qualcomm, Incorporated | Diversity transmission modes for MIMO OFDM communication systems |
US7551546B2 (en) | 2002-06-27 | 2009-06-23 | Nortel Networks Limited | Dual-mode shared OFDM methods/transmitters, receivers and systems |
JP4579680B2 (en) | 2002-06-27 | 2010-11-10 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Measurement of channel characteristics in communication systems |
US7342912B1 (en) * | 2002-06-28 | 2008-03-11 | Arraycomm, Llc. | Selection of user-specific transmission parameters for optimization of transmit performance in wireless communications using a common pilot channel |
EP1379020A1 (en) | 2002-07-03 | 2004-01-07 | National University Of Singapore | A wireless communication apparatus and method |
US7596134B2 (en) | 2002-07-03 | 2009-09-29 | Freescale Semiconductor, Inc. | Flexible method and apparatus for performing digital modulation and demodulation |
US20040017785A1 (en) | 2002-07-16 | 2004-01-29 | Zelst Allert Van | System for transporting multiple radio frequency signals of a multiple input, multiple output wireless communication system to/from a central processing base station |
US6683916B1 (en) * | 2002-07-17 | 2004-01-27 | Philippe Jean-Marc Sartori | Adaptive modulation/coding and power allocation system |
US6885708B2 (en) | 2002-07-18 | 2005-04-26 | Motorola, Inc. | Training prefix modulation method and receiver |
KR20040011653A (en) | 2002-07-29 | 2004-02-11 | 삼성전자주식회사 | Orthogonal frequency division multiplexing communication method and apparatus adapted to channel characteristics |
EP1540830B9 (en) * | 2002-07-30 | 2009-09-16 | IPR Licensing Inc. | System and method for multiple-input multiple-output (mimo) radio communication |
US6961595B2 (en) | 2002-08-08 | 2005-11-01 | Flarion Technologies, Inc. | Methods and apparatus for operating mobile nodes in multiple states |
US7653415B2 (en) * | 2002-08-21 | 2010-01-26 | Broadcom Corporation | Method and system for increasing data rate in a mobile terminal using spatial multiplexing for DVB-H communication |
DE60325921D1 (en) | 2002-08-22 | 2009-03-12 | Imec Inter Uni Micro Electr | Method for MIMO transmission for multiple users and corresponding devices |
US6970722B1 (en) * | 2002-08-22 | 2005-11-29 | Cisco Technology, Inc. | Array beamforming with wide nulls |
US20040037257A1 (en) * | 2002-08-23 | 2004-02-26 | Koninklijke Philips Electronics N.V. | Method and apparatus for assuring quality of service in wireless local area networks |
US8194770B2 (en) * | 2002-08-27 | 2012-06-05 | Qualcomm Incorporated | Coded MIMO systems with selective channel inversion applied per eigenmode |
US6940917B2 (en) | 2002-08-27 | 2005-09-06 | Qualcomm, Incorporated | Beam-steering and beam-forming for wideband MIMO/MISO systems |
WO2004023674A1 (en) | 2002-09-06 | 2004-03-18 | Nokia Corporation | Antenna selection method |
US7260153B2 (en) | 2002-09-09 | 2007-08-21 | Mimopro Ltd. | Multi input multi output wireless communication method and apparatus providing extended range and extended rate across imperfectly estimated channels |
US20040052228A1 (en) * | 2002-09-16 | 2004-03-18 | Jose Tellado | Method and system of frequency and time synchronization of a transceiver to signals received by the transceiver |
US7426176B2 (en) | 2002-09-30 | 2008-09-16 | Lucent Technologies Inc. | Method of power allocation and rate control in OFDMA systems |
US6850511B2 (en) * | 2002-10-15 | 2005-02-01 | Intech 21, Inc. | Timely organized ad hoc network and protocol for timely organized ad hoc network |
US7961774B2 (en) | 2002-10-15 | 2011-06-14 | Texas Instruments Incorporated | Multipath interference-resistant receivers for closed-loop transmit diversity (CLTD) in code-division multiple access (CDMA) systems |
US20040121730A1 (en) | 2002-10-16 | 2004-06-24 | Tamer Kadous | Transmission scheme for multi-carrier MIMO systems |
US7453844B1 (en) | 2002-10-22 | 2008-11-18 | Hong Kong Applied Science and Technology Research Institute, Co., Ltd. | Dynamic allocation of channels in a wireless network |
US7457625B2 (en) * | 2002-10-22 | 2008-11-25 | Texas Instruments Incorporated | Wirelessly-linked, distributed resource control to support wireless communication in non-exclusive spectrum |
US8134976B2 (en) * | 2002-10-25 | 2012-03-13 | Qualcomm Incorporated | Channel calibration for a time division duplexed communication system |
US8570988B2 (en) * | 2002-10-25 | 2013-10-29 | Qualcomm Incorporated | Channel calibration for a time division duplexed communication system |
MXPA05004311A (en) | 2002-10-25 | 2005-08-03 | Qualcomm Inc | Data detection and demodulation for wireless communication systems. |
US20040081131A1 (en) | 2002-10-25 | 2004-04-29 | Walton Jay Rod | OFDM communication system with multiple OFDM symbol sizes |
US8208364B2 (en) | 2002-10-25 | 2012-06-26 | Qualcomm Incorporated | MIMO system with multiple spatial multiplexing modes |
US8320301B2 (en) * | 2002-10-25 | 2012-11-27 | Qualcomm Incorporated | MIMO WLAN system |
US7324429B2 (en) | 2002-10-25 | 2008-01-29 | Qualcomm, Incorporated | Multi-mode terminal in a wireless MIMO system |
US7986742B2 (en) | 2002-10-25 | 2011-07-26 | Qualcomm Incorporated | Pilots for MIMO communication system |
US8169944B2 (en) | 2002-10-25 | 2012-05-01 | Qualcomm Incorporated | Random access for wireless multiple-access communication systems |
US8170513B2 (en) | 2002-10-25 | 2012-05-01 | Qualcomm Incorporated | Data detection and demodulation for wireless communication systems |
US7002900B2 (en) | 2002-10-25 | 2006-02-21 | Qualcomm Incorporated | Transmit diversity processing for a multi-antenna communication system |
US8218609B2 (en) | 2002-10-25 | 2012-07-10 | Qualcomm Incorporated | Closed-loop rate control for a multi-channel communication system |
US7151809B2 (en) * | 2002-10-25 | 2006-12-19 | Qualcomm, Incorporated | Channel estimation and spatial processing for TDD MIMO systems |
WO2004038972A1 (en) | 2002-10-26 | 2004-05-06 | Electronics And Telecommunications Research Institute | Frequency hopping ofdma method using symbols of comb pattern |
US7317750B2 (en) * | 2002-10-31 | 2008-01-08 | Lot 41 Acquisition Foundation, Llc | Orthogonal superposition coding for direct-sequence communications |
EP1416688A1 (en) | 2002-10-31 | 2004-05-06 | Motorola Inc. | Iterative channel estimation in multicarrier receivers |
US7280625B2 (en) | 2002-12-11 | 2007-10-09 | Qualcomm Incorporated | Derivation of eigenvectors for spatial processing in MIMO communication systems |
US7280467B2 (en) | 2003-01-07 | 2007-10-09 | Qualcomm Incorporated | Pilot transmission schemes for wireless multi-carrier communication systems |
US7583637B2 (en) | 2003-01-31 | 2009-09-01 | Alcatel-Lucent Usa Inc. | Methods of controlling data rate in wireless communications systems |
US7058367B1 (en) | 2003-01-31 | 2006-06-06 | At&T Corp. | Rate-adaptive methods for communicating over multiple input/multiple output wireless systems |
US20040176097A1 (en) | 2003-02-06 | 2004-09-09 | Fiona Wilson | Allocation of sub channels of MIMO channels of a wireless network |
EP1447934A1 (en) | 2003-02-12 | 2004-08-18 | Institut Eurecom G.I.E. | Transmission and reception diversity process for wireless communications |
JP2004266586A (en) | 2003-03-03 | 2004-09-24 | Hitachi Ltd | Data transmitting and receiving method of mobile communication system |
JP4250002B2 (en) | 2003-03-05 | 2009-04-08 | 富士通株式会社 | Adaptive modulation transmission system and adaptive modulation control method |
US6927728B2 (en) | 2003-03-13 | 2005-08-09 | Motorola, Inc. | Method and apparatus for multi-antenna transmission |
US7822140B2 (en) | 2003-03-17 | 2010-10-26 | Broadcom Corporation | Multi-antenna communication systems utilizing RF-based and baseband signal weighting and combining |
US7885228B2 (en) | 2003-03-20 | 2011-02-08 | Qualcomm Incorporated | Transmission mode selection for data transmission in a multi-channel communication system |
JP4259897B2 (en) | 2003-03-25 | 2009-04-30 | シャープ株式会社 | Wireless data transmission system and wireless data transmission / reception device |
US7242727B2 (en) | 2003-03-31 | 2007-07-10 | Lucent Technologies Inc. | Method of determining transmit power for transmit eigenbeams in a multiple-input multiple-output communications system |
US7403503B2 (en) | 2003-07-09 | 2008-07-22 | Interdigital Technology Corporation | Resource allocation in wireless communication systems |
RU2006104121A (en) | 2003-07-11 | 2006-07-10 | Квэлкомм Инкорпорейтед (US) | DYNAMIC JOINT USE OF A DIRECT LINK FOR A WIRELESS COMMUNICATION SYSTEM |
WO2005014820A1 (en) | 2003-08-08 | 2005-02-17 | Si Chuan Heben Biotic Engineering Co. Ltd. | 5-enolpyruvyl-3-phosphoshikimate synthase of high glyphosate-bioresistance and coding sequence |
US7065144B2 (en) * | 2003-08-27 | 2006-06-20 | Qualcomm Incorporated | Frequency-independent spatial processing for wideband MISO and MIMO systems |
WO2005022833A2 (en) * | 2003-08-27 | 2005-03-10 | Wavion Ltd. | Wlan capacity enhancement using sdm |
US7356089B2 (en) | 2003-09-05 | 2008-04-08 | Nortel Networks Limited | Phase offset spatial multiplexing |
KR100995031B1 (en) | 2003-10-01 | 2010-11-19 | 엘지전자 주식회사 | Method for controlling signal transmitting applying for MIMO |
US8233462B2 (en) * | 2003-10-15 | 2012-07-31 | Qualcomm Incorporated | High speed media access control and direct link protocol |
US8842657B2 (en) * | 2003-10-15 | 2014-09-23 | Qualcomm Incorporated | High speed media access control with legacy system interoperability |
US8483105B2 (en) * | 2003-10-15 | 2013-07-09 | Qualcomm Incorporated | High speed media access control |
US8526412B2 (en) | 2003-10-24 | 2013-09-03 | Qualcomm Incorporated | Frequency division multiplexing of multiple data streams in a wireless multi-carrier communication system |
US7508748B2 (en) | 2003-10-24 | 2009-03-24 | Qualcomm Incorporated | Rate selection for a multi-carrier MIMO system |
US7616698B2 (en) | 2003-11-04 | 2009-11-10 | Atheros Communications, Inc. | Multiple-input multiple output system and method |
US7298805B2 (en) | 2003-11-21 | 2007-11-20 | Qualcomm Incorporated | Multi-antenna transmission for spatial division multiple access |
US9473269B2 (en) | 2003-12-01 | 2016-10-18 | Qualcomm Incorporated | Method and apparatus for providing an efficient control channel structure in a wireless communication system |
US7231184B2 (en) | 2003-12-05 | 2007-06-12 | Texas Instruments Incorporated | Low overhead transmit channel estimation |
EP1698086A2 (en) | 2003-12-27 | 2006-09-06 | Electronics and Telecommunications Research Institute | A mimo-ofdm system using eigenbeamforming method |
US7333556B2 (en) * | 2004-01-12 | 2008-02-19 | Intel Corporation | System and method for selecting data rates to provide uniform bit loading of subcarriers of a multicarrier communication channel |
JP2005223829A (en) | 2004-02-09 | 2005-08-18 | Nec Electronics Corp | Fractional frequency divider circuit and data transmission apparatus using the same |
US7206354B2 (en) * | 2004-02-19 | 2007-04-17 | Qualcomm Incorporated | Calibration of downlink and uplink channel responses in a wireless MIMO communication system |
US7746886B2 (en) | 2004-02-19 | 2010-06-29 | Broadcom Corporation | Asymmetrical MIMO wireless communications |
US7274734B2 (en) | 2004-02-20 | 2007-09-25 | Aktino, Inc. | Iterative waterfiling with explicit bandwidth constraints |
US7486740B2 (en) * | 2004-04-02 | 2009-02-03 | Qualcomm Incorporated | Calibration of transmit and receive chains in a MIMO communication system |
US7848442B2 (en) | 2004-04-02 | 2010-12-07 | Lg Electronics Inc. | Signal processing apparatus and method in multi-input/multi-output communications systems |
US7110463B2 (en) | 2004-06-30 | 2006-09-19 | Qualcomm, Incorporated | Efficient computation of spatial filter matrices for steering transmit diversity in a MIMO communication system |
US7606319B2 (en) | 2004-07-15 | 2009-10-20 | Nokia Corporation | Method and detector for a novel channel quality indicator for space-time encoded MIMO spread spectrum systems in frequency selective channels |
US20060018247A1 (en) | 2004-07-22 | 2006-01-26 | Bas Driesen | Method and apparatus for space interleaved communication in a multiple antenna communication system |
US7599443B2 (en) | 2004-09-13 | 2009-10-06 | Nokia Corporation | Method and apparatus to balance maximum information rate with quality of service in a MIMO system |
KR100905605B1 (en) * | 2004-09-24 | 2009-07-02 | 삼성전자주식회사 | Data transmission method for ofdm-mimo system |
TWI296753B (en) | 2004-10-26 | 2008-05-11 | Via Tech Inc | Usb control circuit for saving power and the method thereof |
US8498215B2 (en) | 2004-11-16 | 2013-07-30 | Qualcomm Incorporated | Open-loop rate control for a TDD communication system |
EP1829262B1 (en) | 2004-11-16 | 2018-03-14 | QUALCOMM Incorporated | Closed-loop rate control for a mimo communication system |
US7525988B2 (en) | 2005-01-17 | 2009-04-28 | Broadcom Corporation | Method and system for rate selection algorithm to maximize throughput in closed loop multiple input multiple output (MIMO) wireless local area network (WLAN) system |
US7466749B2 (en) | 2005-05-12 | 2008-12-16 | Qualcomm Incorporated | Rate selection with margin sharing |
US7603141B2 (en) | 2005-06-02 | 2009-10-13 | Qualcomm, Inc. | Multi-antenna station with distributed antennas |
US8358714B2 (en) | 2005-06-16 | 2013-01-22 | Qualcomm Incorporated | Coding and modulation for multiple data streams in a communication system |
US20090161613A1 (en) | 2007-11-30 | 2009-06-25 | Mark Kent | Method and system for constructing channel quality indicator tables for feedback in a communication system |
US20090291642A1 (en) * | 2008-05-23 | 2009-11-26 | Telefonaktiebolaget Lm Ericsson (Publ) | Systems and Methods for SIR Estimation for Power Control |
US8619620B2 (en) * | 2008-09-16 | 2013-12-31 | Qualcomm Incorporated | Methods and systems for transmission mode selection in a multi channel communication system |
ES2355347B1 (en) * | 2009-01-30 | 2012-02-10 | Vodafone España, S.A.U. | METHOD FOR DETECTING INTERFERENCES IN A WIRELESS COMMUNICATION SYSTEM. |
US20100260060A1 (en) * | 2009-04-08 | 2010-10-14 | Qualcomm Incorporated | Integrated calibration protocol for wireless lans |
-
2003
- 2003-10-23 US US10/693,169 patent/US8134976B2/en active Active
- 2003-10-24 CA CA002502801A patent/CA2502801A1/en not_active Abandoned
- 2003-10-24 EP EP10150226.8A patent/EP2166688B1/en not_active Expired - Lifetime
- 2003-10-24 MX MXPA05004391A patent/MXPA05004391A/en active IP Right Grant
- 2003-10-24 BR BR0315538-2A patent/BR0315538A/en not_active IP Right Cessation
- 2003-10-24 KR KR1020057007139A patent/KR101014502B1/en active IP Right Grant
- 2003-10-24 CN CN2003801067973A patent/CN1751484B/en not_active Expired - Lifetime
- 2003-10-24 WO PCT/US2003/034515 patent/WO2004039022A2/en active Search and Examination
- 2003-10-24 AU AU2003287293A patent/AU2003287293C1/en not_active Ceased
- 2003-10-24 EP EP03781525.5A patent/EP1557017B1/en not_active Expired - Lifetime
- 2003-10-24 TW TW092129800A patent/TWI363515B/en not_active IP Right Cessation
- 2003-10-24 EP EP11155678.3A patent/EP2357769B1/en not_active Expired - Lifetime
- 2003-10-24 JP JP2004547245A patent/JP2006504336A/en not_active Withdrawn
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2010
- 2010-03-19 JP JP2010064349A patent/JP5528867B2/en not_active Expired - Lifetime
- 2010-09-21 JP JP2010210828A patent/JP2011050063A/en not_active Withdrawn
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EP1557017A2 (en) | 2005-07-27 |
AU2003287293A1 (en) | 2004-05-13 |
US8134976B2 (en) | 2012-03-13 |
US8750151B2 (en) | 2014-06-10 |
TW200417176A (en) | 2004-09-01 |
US20120176928A1 (en) | 2012-07-12 |
TWI363515B (en) | 2012-05-01 |
EP2166688B1 (en) | 2020-03-18 |
EP2357769A2 (en) | 2011-08-17 |
JP2006504336A (en) | 2006-02-02 |
WO2004039022A3 (en) | 2004-09-16 |
KR101014502B1 (en) | 2011-02-14 |
EP1557017B1 (en) | 2016-06-08 |
EP2166688A3 (en) | 2010-03-31 |
AU2003287293B2 (en) | 2009-04-23 |
JP2010193477A (en) | 2010-09-02 |
EP2357769B1 (en) | 2017-12-06 |
BR0315538A (en) | 2006-01-17 |
EP2166688A2 (en) | 2010-03-24 |
MXPA05004391A (en) | 2005-07-26 |
US20040085939A1 (en) | 2004-05-06 |
JP2011050063A (en) | 2011-03-10 |
CN1751484B (en) | 2010-08-11 |
EP2357769A3 (en) | 2013-05-08 |
CN1751484A (en) | 2006-03-22 |
WO2004039022A2 (en) | 2004-05-06 |
JP5528867B2 (en) | 2014-06-25 |
AU2003287293C1 (en) | 2009-09-24 |
KR20050065628A (en) | 2005-06-29 |
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