WO1998018242A1 - Method and apparatus for determining the rate of received data in a variable rate communication system - Google Patents
Method and apparatus for determining the rate of received data in a variable rate communication system Download PDFInfo
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- WO1998018242A1 WO1998018242A1 PCT/US1997/018625 US9718625W WO9818242A1 WO 1998018242 A1 WO1998018242 A1 WO 1998018242A1 US 9718625 W US9718625 W US 9718625W WO 9818242 A1 WO9818242 A1 WO 9818242A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0262—Arrangements for detecting the data rate of an incoming signal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0046—Code rate detection or code type detection
Definitions
- the present invention relates to communications. More particularly, the present invention relates to a method and apparatus for determining transmission rate in a variable rate transmission system.
- CDMA code division multiple access
- TDMA time division multiple access
- FDMA frequency division multiple access
- AM modulation schemes such as amplitude companded single sideband (ACSSB)
- TDMA time division multiple access
- FDMA frequency division multiple access
- AM modulation schemes such as amplitude companded single sideband (ACSSB)
- CDMA has significant advantages over these other techniques.
- the use of CDMA techniques in a multiple access communication system is disclosed in U.S. Patent No. 4,901,307, entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” and assigned to the assignee of the present invention and incorporated by reference herein.
- CDMA by its inherent nature of being a wideband signal offers a form of frequency diversity by spreading the signal energy over a wide bandwidth. Therefore, frequency selective fading affects only a small part of the CDMA signal bandwidth.
- Space or path diversity is obtained by providing multiple signal paths through simultaneous links from a mobile user through two or more cell-sites.
- path diversity may be obtained by exploiting the multipath environment through spread spectrum processing by allowing a signal arriving with different propagation delays to be received and processed separately. Examples of path diversity are illustrated in U.S. Patent No. 5,101,501 entitled “METHOD AND SYSTEM FOR PROVIDING A SOFT HANDOFF IN COMMUNICATIONS IN A CDMA CELLULAR TELEPHONE SYSTEM", and U.S. Patent No. 5,109,390 entitled “DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM", both assigned to the assignee of the present invention, and incorporated by reference herein.
- CDMA systems often employ a variable rate vocoder to encode data so that the data rate can be varied from one data frame to another.
- An exemplary embodiment of a variable rate vocoder is described in U.S. Pat. No. 5,414,796, entitled “VARIABLE RATE VOCODER,” assigned to the assignee of the present invention and incorporated by reference herein.
- the use of a variable rate communications channel reduces mutual interference by eliminating unnecessary transmissions when there is no useful speech to be transmitted.
- Algorithms are utilized within the vocoder for generating a varying number of information bits in each frame in accordance with variations in speech activity.
- a vocoder with a rate set of four may produce 20 millisecond data frames containing 20, 40, 80, or 160 bits, depending on the activity of the speaker. It is desired to transmit each data frame in a fixed amount of time by varying the transmission rate of communications. Additional details on the formatting of the vocoder data into data frames are described in U.S. Pat. No. 5,511,073, entitled "METHOD AND APPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION," assigned to the assignee of the present invention, and incorporated by reference herein. One technique for the receiver to determine the rate of a received data frame is described in copending U.S. patent application Serial No.
- Error metrics which describe the quality of the decoded symbols for each frame decoded at each rate, are provided to a processor.
- the error metrics may include Cyclic Redundancy Check (CRC) results, Yamamoto Quality Metrics, and Symbol Error Rates. These error metrics are well-known in communications systems.
- the processor analyzes the error metrics and determines the most probable rate at which the incoming symbols were transmitted.
- the present invention provides a novel and improved apparatus and method for decoding data.
- the apparatus and method are employed in a communications system having a transmitter and a receiver, where the receiver determines at which of several rates individual frames in a signal has been transmitted by the transmitter. For example, if the transmitter employs four transmission rates, the receiver decodes each frame of the received signal based on the four rates to produce four cyclic redundancy check (CRC) bits, four symbol error rate (SER) values and one or more Yamamoto check values. If the CRC checks for only two rates, then the receiver compares to each other the SER values for those two rates to determine at which of the two rates a current frame was transmitted.
- CRC cyclic redundancy check
- SER symbol error rate
- the present invention embodies a method for use in a communication system having a transmitter and a receiver.
- the transmitter transmits a signal at a current rate, wherein the current rate corresponds to one of a plurality of rates.
- the receiver generates a plurality of check error values and error rate codes, and at least one decoding code, each based on whether the signal has one of the plurality of rates.
- the method determines the current rate of the signal and includes the steps of: (a) determining if only a first check value of a selected rate favorably checks, wherein the selected rate is one of the plurality of rates; (b) determining if the selected rate corresponds to a predetermined rate; (c) if the selected rate corresponds to the predetermined rate, comparing a selected decoding code to a selected value; (d) if the selected rate does not correspond to the predetermined rate, comparing a selected error rate code to a first value based on a predetermined operational relationship, wherein the selected rate code corresponds to the selected rate; (e) if the selected decoding code corresponds to the selected value, comparing the selected error rate code to a second value based on the predetermined operational relationship; (f) if the selected decoding code does not correspond to the selected value,
- the present invention also embodies a method for determining the current rate of the signal having the steps of: (a) determining that only first and second error check values of first and second rates favorably check, wherein the first and second rates are from the plurality of rates; (b) comparing a first error rate code to a second error rate code plus a first value based on a predetermined operational relationship, wherein the first and second error rate codes correspond to the first and second rates; and (c) determining that the current rate of the signal is the second rate if the first error rate code has the predetermined operational relationship to the second error rate code plus a first value, and otherwise determining that the current rate is the first rate.
- FIG. 1 is a block diagram of the communication system of the present invention
- FIG. 2 is a flowchart illustrating a method for selecting the decoded frame when the CRC checks for two different rates
- FIG. 3 is a flowchart illustrating an alternative method for selecting the decoded frame when the CRC checks for two different rates
- FIG. 4 is a flowchart illustrating a method for selecting the decoded frame when the CRC checks for one rate
- FIG. 5 is a flowchart illustrating an alternative method for selecting the decoded frame when the CRC checks for one rate.
- FIG. 6 is a plot of rate decision regions for symbol error rates i and j where the CRC checks for both rates i and j.
- a remote transmission system 2 transmits data to a remote receiving system 4.
- the present invention is implemented in a wireless communication system which communicates using spread spectrum modulation signals. Communication using spread spectrum communication systems is described in detail in the aforementioned U.S. Patents 4,901,307 and 5,103,459.
- a variable rate data source 6 provides variable rate data frames for transmission to a Cyclic Redundancy Check (CRC) and Tail Bit Generator 8.
- CRC Cyclic Redundancy Check
- the data source 6 is a variable rate vocoder for encoding speech information at four variable rates as described in detail in the aforementioned U.S Patent No. 5,414,796.
- the signal When used, for example, in a cellular telephone environment, the signal is transmitted at the full rate to transmit speech (i.e., when a user is talking) and is transmitted at the eighth rate to transmit silence (i.e., when the user is not talking).
- the eighth rate saves on the number of bits transmitted, and thereby saves on power.
- 90% of the signals transmitted by the transmitter 2 to the receiver 4 are either at the full or one-eighth rate.
- the one-half and one-quarter rates represent transitional rates between the full and eighth rates.
- the generator 8 generates a set of CRC bits to provide for error detection at the receiver as is well known in the art. In addition, the generator 8 appends a sequence of tail bits to the frame. In the exemplary embodiment, the generator 8 generates the set of CRC and tail bits in accordance with the Telecommunications Industry Association's TIA/EIA/IS-95-A Mobile Stations-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System.
- the data frame is provided by the generator 8 to an encoder 10 which encodes the data as symbols for error correction and detection at the receiver.
- the encoder 10 is a rate 1/2 convolutional encoder.
- the encoded symbols are provided to an interleaver 12, which reorders the encoded symbols in accordance with a predetermined interleaving format.
- the interleaver 12 is a block interleaver, the design and implementation of which is well known in the art.
- the reordered frame is then provided to a modulator 14 which modulates the frame for transmission.
- the modulator 14 is a CDMA modulator, the implementation of which is described in detail in the aforementioned U.S. Patents 4,901,307 and 5,103,459.
- the modulated data frame is provided to a transmitter (TMTR) 16.
- the transmitter 16 upconverts and amplifies the signal for transmission through an antenna 18.
- the transmitted signal is received by an antenna 20 of a remote station 4, such as a cellular phone, and provided to a receiver (RCVR) 22 which down converts and amplifies the received signal.
- the received signal is then provided to a demodulator (DEMOD) 24 which demodulates the signal.
- the demodulator 24 is a CDMA demodulator 24, the implementation of which is described in detail in the aforementioned U.S. Patents 4,901,307 and 5,103,459.
- the demodulated signal is then provided to a diversity combiner 26.
- the diversity combiner 26 combines the demodulated signal from the demodulator 24 with demodulated signals from other demodulators (not shown) which demodulate the same signal except provided on a different propagation path.
- the design and implementation of the diversity combiner 26 is described in detail in the aforementioned U.S. Patent No. 5,109,390.
- the diversity combined signal is provided to a de-interleaver 28 which re-orders the symbols in the frame in accordance with a predetermined re-ordering format as is well known in the art.
- the re-ordered frame is then provided to a multi-rate decoder 30, which provides error correction on the frame of symbols.
- the decoder 30 decodes the data based on a predetermined set of rate hypotheses.
- the decoder 30 is a multi-rate Viterbi decoder as is described in detail in the aforementioned copending U.S. Patent Application Serial No. 08/126,477.
- the decoder 30 decodes the symbols for each of the four possible rates to provide four separately decoded frames of data, each of which is provided to a CRC check detector 32.
- the CRC check detector 32 determines under conventional techniques whether the cyclic redundancy check bits for each frame are correct for the decoded data.
- the CRC check detector 32 performs a CRC check for the CRC bits in the four decoded frames to help determine whether the currently received frame was transmitted at the full, half, quarter or eighth rates.
- the CRC check detector 32 provides four check bits, , C ⁇ C 4 and , where a binary value of "1" for a given CRC check bit can indicate that the CRC check matched or checked, while a binary value of "0" can indicate that the CRC bits did not check.
- the subscript or indication "1" corresponds to the full rate
- "2" corresponds to the half rate
- "4" corresponds to the quarter rate
- "8" corresponds to the eighth rate.
- the decoder 30 provides the decoded data to a symbol error rate (SER) check detector 34.
- the SER detector 34 receives the decoded bits and an estimate of the received symbol data from the decoder 30. As is known, the SER detector 34 re-encodes the decoded bits, and compares them to the estimate of the received symbol data from the decoder 30. The SER is a count of the number of discrepancies between the re-encoded symbol data and the received symbol data. Therefore, the SER detector 34 generates four SER values: SER ⁇ , SER 2 , SER 4 and SER 8 . For processing efficiency, the SER detector 34 provides SER values having a maximum value of 255.
- the SER values help provide a determination of the rate of the current frame transmitted by the transmitter 2, and whether the frame has errors.
- the decoder 30 provides information to a Yamamoto check detector 36 which provides a confidence metric based on the difference between the selected path through a trellis and the next closest path through the trellis. While the CRC check is dependent on the bits in each of the four decoded frames, the Yamamoto check is dependent on the decoding process of the receiver 4.
- the Yamamoto detector 36 as with the detectors 32 and 34, provides four Yamamoto values for each of the four possible rates: Y lr Y 2 , Y 4 and Y 8 . Although the detectors 32, 34 and 36 are shown as separate elements, the detectors can be incorporated within the hardware of the decoder 30.
- a control processor 38 receives the CRC check bits, SER values and Yamamoto values from the detectors 32, 34 and 36, respectively. The processor 38 then determines at which of the four rates the currently received frame was sent.
- the decoder 30 provides four decoded frames for storage in a decoded frame buffer 40, where each of the four frames is decoded under one of the four rates. Based on the rate determined by the processor 38, the control processor provides a signal to the decoded frame buffer 40, which in response thereto, outputs the stored frame decoded at the determined rate or outputs no frame if an erasure is declared. In an alternative embodiment, decoder frame buffer 40 outputs a signal indicative of a frame erasure if an erasure is declared. Under the communication system of FIG.
- the signal transmitted by the transmitter 2 to the receiver 4 can rapidly change between the four rates.
- the transmitter 2 does not include within the transmitted signal an actual indication as to the rate at which the signal is currently being transmitted. To do so would require unnecessary bandwidth. Therefore, the transmitter 2 transmits a frame at a current rate (selected from one of the four rates), and a control processor 38 and the decoder 30 of the receiver 4, under routines described below, determine at which of the four rates the currently received frame was sent or whether an erasure should be declared (i.e., whether the current frame was sent at the full, half, quarter or eighth rate). The decoder 30 then decodes the one of the four decoded frames which has the determined rate and outputs a decoded signal. The appropriately decoded signal can then be input to, for example, a vocoder, amplifier and speaker (not shown) to output a voice signal to be heard by a user of the receiver 4.
- the control processor 38 coupled to at least the decoder 30, operates in conjunction with the methods illustrated in the flow diagrams of FIGS. 2-5 to select the appropriate decoded frame to be output or provided to the user, or to declare the current frame an erasure condition. While the control processor 38 and decoder 30 are shown as separate elements, the control processor and decoder can be incorporated together to form a single decoder.
- step 104 the processor 38 determines whether the CRC for exactly one rate checks. If so, then in step 108, the processor 38 performs a one CRC check routine as described below. However, if the CRCs for none of the rates check, or if the CRCs for three or four rates check, then in step 106, the processor 38 declares the currently received frame an erasure. In general, if the CRCs for none of the rates check, then the current frame is erased.
- step 110 the processor 38 compares the SER values for the two rates that checked in step 102. For example, if the CRCs for the full and eighth rates check in step 102, then the processor 38 in step 110 determines whether the SER value for the full rate (SER ⁇ is greater than or equal to the SER value for the eighth rate (SER 8 ) plus a weighting value W determined based on the full and eighth rates (W 1 ⁇ 8 ). In general, the processor 38 under step 110 compares the SERs based on the following equation: where i and j refer to the two rates corresponding to the two rates that checked under step 102.
- the weighting or scaling value W can have one of six possible values, since i and j can have one of four possible values based on the four rates (i.e., W 1/2 , W ⁇ , , W 1 8 , W 24 , W 28 , and W 48 ). Additionally, the weighting value W can have a value ranging from -255 to +255 since the SER values have a maximum value of 255.
- the weighting value W is generally necessary because, fof the different probability densities of the SERs for the possible rates, and the differences in the chances of the CRC checking given the different actual frame rates from the transmitter.
- the weighting value W is preferably established based on empirical data provided through experimentation. By establishing a target acceptable error rate, and testing the response of the communication system of FIG. 1 under the four rates, empirical data resulting therefrom is used to determine a weighting value W for each of the six combination of rates.
- the weighting value W provides an increased level of confidence as to which of the two rates the currently received frame was transmitted. Simply determining that the current rate is equal to the rate having the lower SER can result in incorrectly determining the rate of the current frame. Therefore, the SERi value must be less than the SER j value plus a weighting factor for the processor 38 to determine that the rate of the currently received frame is equal to the rate I.
- the decoder 30 will output a noisy signal that can be amplified and broadcast to a user's ear. Such a noisy signal can be perceptually undesirable to a user.
- the present invention sacrifices a little higher frame erasure rate, in exchange for not decoding a current frame at the wrong rate.
- the receiver 4 preferably attempts to maintain a frame erasure rate of less than 1%.
- the probability of the wrong rate being determined under the routines described herein are less than or equal to 10 "5 .
- the processor 38 determines that the rate of the current frame received from the transmitter 2 is at the rate i. Alternatively, if the SER; value is less than the SER j value plus W ⁇ , then in step 114, the processor 38 determines that the rate of the current frame received from the transmitter 2 is equal to the rate j. In the above example, where i and j correspond to the full and eighth rates, respectively, if the SERj.
- the processor 38 After determining the rate of the current frame, the processor 38 provides an appropriate signal to the buffer 40, which in response thereto, outputs the frame decoded corresponding to the determined rate or no frame if an erasure is declared.
- An alternative embodiment according to the present invention for determining the received signal rate where two of the four rates check is shown in FIG. 3 as a routine 120. This and other alternative embodiments described below are similar to their corresponding previously described embodiment, and common steps are identified by the same reference numerals. Only the significant differences in operation are described in detail.
- the routine 120 performs the same steps 102, 104, 106 and 108 as described above with respect to the routine 100.
- step 124 if the CRCs for two of the rates check under step 102, then the processor 38 employs a more accurate comparison between the SER values for the two rates identified under step 102 to further ensure that the current frame is decoded under the appropriate rate.
- the processor 38 in step 124 employs a multiplicative factor k ⁇ in equation (1) above, to provide the following comparative function: SER; > k * SER j + W y . (2)
- the multiplicative factor kj j is preferably determined through experimentation based on empirical data for the four transmission rates. Therefore, six possible multiplicative factors are possible based on the four transmission rates (i.e., k 1 2 , k 1/ , k 1 8 , k 24 , k 2/8 , and k 48 ).
- the multiplicative factor k can simply be a normalization factor so that, for example, if i is equal to full and j is equal to half, then k 12 would be equal to two to normalize the half rate SER 2 value with respect to the SERi . value.
- the multiplicative factor k can include not only a normalization factor, but compensate for differences between the different transmission rates, as described below.
- FIG. 6 a simplified diagram is shown of rate decision regions for SER values SER; and SER j , where CRCs for rates i and j check.
- the multiplicative factor k ⁇ determines the slope of the line, while the weighting value Wy determines its offset from the origin (its Y-axis intercept).
- the multiplicative factor k and weighting value W vary the decision range for areas 140 and 142.
- the empirical data can be input to spreadsheets and known numerical analysis techniques can be employed under the spreadsheets to provide optimized values below the target acceptable error rate.
- routine 120 and the other routines described herein employ functions based on two rates and two SERs, SERj, SER j (i.e. f(i, j, SERj, SER j ).
- the present invention employs linear equations such as equation (2) above, and as represented in FIG. 6.
- the weighting value W, the multiplicative factor k, and the maximum and minimum SER thresholds are preferably stored in memory as a look-up table (not shown) to be accessed by the processor 38.
- step 124 the processor 38 essentially determines on which side of the line in FIG. 6 a point defined by the two SER values (SERj, SER j ) exists, to thereby determine the most likely rate for the currently received frame. If the SER; value is less than ky times the SER j value plus W ⁇ , then in step 126, the processor 38 determines whether the SER, is greater than a maximum acceptable SER threshold for rate i (i.e., MaxSERj). In general, there is a maximum SER threshold value for the given rate beyond which the probability of error (of decoding at the incorrect rate) is unacceptable. As noted above, the maximum SER thresholds, shown in FIG. 6, are determined based on empirical data derived through experimentation with the four rates.
- the processor 38 in step 128 determines that the rate of the currently received frame is equal to i. If, however, the SERj value is greater than or equal to the maximum SERj threshold, then in step 130 the processor 38 determines that the current frame is an erasure.
- step 124 the processor 38 determines that the SERj value is greater than or equal to k ⁇ times the SER j value plus W . If so, the processor 38 in step 132, the processor 38 determines whether the SER j value is greater than or equal to a maximum SER threshold for rate j (i.e., MaxSER j ). If so, the processor 38 in step 130 determines that the current frame is erased. However, if the SER j value is less than the maximum SER j threshold, then in step 134 the processor 38 determines that the current frame was transmitted at the rate j.
- a maximum SER threshold for rate j i.e., MaxSER j
- a routine 200 is performed by the processor 38 if the CRC for only one rate checks.
- step 206 the processor 38 determines whether the SER value for the determined rate is greater than or equal to a maximum SER threshold for that rate (i.e., SERj > MaxSERj). If it is less than the maximum, then in step 208, the processor 38 determines that the rate of the currently received frame is equal to i; otherwise, in step 210, the processor declares an erasure.
- step 212 the processor examines the Yamamoto value for the eighth rate (Y 8 ).
- Y 8 the Yamamoto value for the eighth rate
- the routine 200 employs additional checks to confirm that the current frame was transmitted at the eighth rate. Consequently, in step 212, if the Yamamoto value for the eighth rate checks (i.e., provides a binary "1" value to the decoder 30), then the processor 38 has an increased level of confidence that the rate of the current frame is the eighth rate. Therefore, in step 214, the processor 38 employs a larger or looser maximum SER value for the determined rate. Such a looser maximum SER threshold improves the probability that subsequent steps under the routine 200 will appropriately determine that the current frame was transmitted at the eighth rate.
- step 216 the processor 38 selects a smaller or tighter maximum SER value for the eighth rate. If the Yamamoto value does not check, the processor 38 expects the current frame to be an erasure, and therefore makes subsequent comparisons more stringent to ensure that the current frame is determined to have been transmitted at the eighth rate under only the most stringent of comparisons. Under step 206, the processor 38 employs the looser maximum SER value from step 214, or the tighter maximum SER value from step 216, and compares it to the eighth rate SER to determine whether the frame is erased (step 210) or confirms that the current frame was transmitted at the eighth rate (step 208). Referring to FIG. 5, a more detailed analysis is shown as a routine 220.
- the processor 38 under the routine 220 performs the steps 202, 204, and 206 as discussed above. Thereafter, however, under steps 228, 230, and 232, the processor 38 compares the SER values for the three rates which did not check under step 202 (i.e., rates j, k, and 1), to minimum SER thresholds. This reduces the chances that one of the rates decoded with a low SER is actually the correct rate though the CRC did not check for that rate. The steps 228, 230 and 232 determine if the SER values for the other rates are greater than minimum thresholds for that rate, and if so, declare an erasure because the probability that the current frame was transmitted at that rate outweighs the probability that the current frame was transmitted at rate i.
- step 228, the processor 38 determines whether the SER j value is less than or equal to the minimum SER threshold for the determined rate i and the rate j (i.e., SERj j ). If it is, then the processor 38 declares the current frame an erasure under step 227. The reason for doing so is that the low SER of another rate (j) indicates an increased probability that the frame was transmitted at that rate (j). If it isn't, then under steps 230 and 232, the processor 38 compares the last two SER values (for rates k and 1) to corresponding minimum SER thresholds for the rate i and rates k or 1 (SERj k and SERy), respectively.
- the processor 38 If the SER k or SERi values are less than the minimum thresholds under steps 230 or 232, then the processor 38 declares a current frame an erasure under step 227. However, if such SER values are greater than the minimum, then in step 234 the processor 38 determines that the current frame was transmitted at rate i. As under the routine 200, if the rate which checked under step 202 is determined to be the eighth rate in step 204, then the processor 38 checks the Yamamoto values for the eighth rate under step 212 as discussed above.
- the processor 38 not only employs a looser maximum SER threshold for the determined rate (the eighth rate), but also employs looser minimum SER thresholds for the determined and nondetermined rates (i.e., looser Min. SERj j , SER i/k and SERy).
- the processor 38 not only employs a tighter maximum SERj threshold, but tighter minimum SER thresholds for the other rates (i.e., tighter Min. SER ifj SER i k and SER ).
- the threshold lookup table employed by the processor 38 includes two maximum threshold values for the eighth rate, and two sets of three minimum threshold values to be employed under steps 238 and 240.
- the processor 38 can compare the particular SER value to a linear function by multiplying the minimum or maximum SER threshold by the multiplicative factor k, and adding an appropriate weighting value W.
- the processor 38 can compare the SER value SER; to the function kj*MaxSERj + Wj, while under step 228, the processor can compare the SER j value to the function kj j * MinSERj j + Wj j .
- a nonlinear function can be employed under steps 206-232. However, any improvement provided by a nonlinear function will likely, at best, provide only a small incremental benefit to the routine 220 and will lead to processing complexity and thus increased processing time.
- the routine 220 can be modified so that the Yamamoto values for the other rates are also checked. As a result, corresponding tighter or looser maximum and minimum SER thresholds would be employed for each of the other rates. A larger lookup table would therefore be required under such an alternative embodiment by the processor 38. Additionally, the routines 100, 120, 200 can employ such above alternatives, such as employing the Yamamoto check for each rate.
- routines of the present invention can compare the currently determined rate (rate i) to previous rates. As noted above, 90% of the time the rate of the current frame is either at the full or eighth rate in the exemplary embodiment. Similarly, under the exemplary embodiment, the probability is high that the rate of the current frame is equal to the rate of the previous frame.
- routines can compare the determined rate of the current frame to the rate of the previous frame, and apply looser maximum and minimum SER thresholds. Alternatively, if the current determined rate differs from the previous rate, tighter thresholds can be applied.
Abstract
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Priority Applications (9)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP51947298A JP3889448B2 (en) | 1996-10-18 | 1997-10-09 | Method and apparatus for determining the rate of received data in a variable rate communication system |
CA002268857A CA2268857C (en) | 1996-10-18 | 1997-10-09 | Method and apparatus for determining the rate of received data in a variable rate communication system |
BR9712354-4A BR9712354A (en) | 1996-10-18 | 1997-10-09 | Method and equipment for determining the rate of data received in a variable rate communication system |
IL12930597A IL129305A0 (en) | 1996-10-18 | 1997-10-09 | Method and apparatus for determining the rate of received data in a variable rate communication system |
RU99109991/09A RU99109991A (en) | 1996-10-18 | 1997-10-09 | METHOD AND DEVICE FOR DETERMINING THE RATE OF RECEIVED DATA IN THE COMMUNICATION SYSTEM WITH VARIABLE SPEED |
AU48220/97A AU4822097A (en) | 1996-10-18 | 1997-10-09 | Method and apparatus for determining the rate of received data in a variable rate communication system |
DE69735673T DE69735673T2 (en) | 1996-10-18 | 1997-10-09 | METHOD AND DEVICE FOR DETERMINING THE DATA RATE OF RECEIVED DATA IN A TRANSMISSION SYSTEM WITH A CHANGING DATA RATE |
EP97910971A EP0932963B1 (en) | 1996-10-18 | 1997-10-09 | Method and apparatus for determining the rate of received data in a variable rate communication system |
HK00100673A HK1024362A1 (en) | 1996-10-18 | 2000-02-03 | Method and apparatus for determining the rate of received data in a variable rate communication system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US08/730,863 US5751725A (en) | 1996-10-18 | 1996-10-18 | Method and apparatus for determining the rate of received data in a variable rate communication system |
US730,863 | 1996-10-18 |
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WO1998018242A1 true WO1998018242A1 (en) | 1998-04-30 |
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PCT/US1997/018625 WO1998018242A1 (en) | 1996-10-18 | 1997-10-09 | Method and apparatus for determining the rate of received data in a variable rate communication system |
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US (1) | US5751725A (en) |
EP (2) | EP0932963B1 (en) |
JP (1) | JP3889448B2 (en) |
KR (1) | KR100559099B1 (en) |
CN (1) | CN1124726C (en) |
AT (2) | ATE432577T1 (en) |
AU (1) | AU4822097A (en) |
BR (1) | BR9712354A (en) |
CA (1) | CA2268857C (en) |
DE (2) | DE69739430D1 (en) |
ES (1) | ES2260786T3 (en) |
HK (2) | HK1024362A1 (en) |
IL (1) | IL129305A0 (en) |
RU (1) | RU99109991A (en) |
TW (1) | TW363312B (en) |
WO (1) | WO1998018242A1 (en) |
Cited By (4)
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Also Published As
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ATE432577T1 (en) | 2009-06-15 |
CA2268857A1 (en) | 1998-04-30 |
AU4822097A (en) | 1998-05-15 |
RU99109991A (en) | 2003-03-10 |
EP1478144A1 (en) | 2004-11-17 |
HK1024362A1 (en) | 2000-10-05 |
CN1124726C (en) | 2003-10-15 |
DE69735673T2 (en) | 2007-03-29 |
DE69739430D1 (en) | 2009-07-09 |
TW363312B (en) | 1999-07-01 |
KR20000049248A (en) | 2000-07-25 |
JP2001505377A (en) | 2001-04-17 |
HK1072846A1 (en) | 2005-09-09 |
CN1234160A (en) | 1999-11-03 |
ES2260786T3 (en) | 2006-11-01 |
KR100559099B1 (en) | 2006-03-15 |
DE69735673D1 (en) | 2006-05-24 |
ATE323365T1 (en) | 2006-04-15 |
EP0932963B1 (en) | 2006-04-12 |
BR9712354A (en) | 1999-08-31 |
EP1478144B1 (en) | 2009-05-27 |
CA2268857C (en) | 2008-09-09 |
EP0932963A1 (en) | 1999-08-04 |
US5751725A (en) | 1998-05-12 |
JP3889448B2 (en) | 2007-03-07 |
IL129305A0 (en) | 2000-02-17 |
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