CA2148940A1 - Using two classes of channels with different capacity - Google Patents
Using two classes of channels with different capacityInfo
- Publication number
- CA2148940A1 CA2148940A1 CA2148940A CA2148940A CA2148940A1 CA 2148940 A1 CA2148940 A1 CA 2148940A1 CA 2148940 A CA2148940 A CA 2148940A CA 2148940 A CA2148940 A CA 2148940A CA 2148940 A1 CA2148940 A1 CA 2148940A1
- Authority
- CA
- Canada
- Prior art keywords
- channels
- class
- mobile station
- channel
- base station
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 claims abstract description 18
- 230000010267 cellular communication Effects 0.000 claims abstract description 16
- 238000004891 communication Methods 0.000 claims abstract description 8
- 230000006854 communication Effects 0.000 claims abstract description 8
- 238000005259 measurement Methods 0.000 claims description 5
- 238000003491 array Methods 0.000 claims description 3
- 206010019133 Hangover Diseases 0.000 claims 1
- 230000003044 adaptive effect Effects 0.000 description 10
- 230000001413 cellular effect Effects 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 3
- 230000003595 spectral effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000012549 training Methods 0.000 description 2
- 241001296096 Probles Species 0.000 description 1
- 241000030538 Thecla Species 0.000 description 1
- 210000000941 bile Anatomy 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
- H04W16/28—Cell structures using beam steering
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/0005—Control or signalling for completing the hand-off
- H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
- H04W36/0085—Hand-off measurements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/08—Reselecting an access point
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/56—Allocation or scheduling criteria for wireless resources based on priority criteria
- H04W72/563—Allocation or scheduling criteria for wireless resources based on priority criteria of the wireless resources
Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus for transmitting and receiving signals in a base station with an antenna array in a cellular communication system. The available communication channels are divided into a plurality of classes. The base station transmits signals to the mobile station in a first class of channels in a wide antenna lobe. The position of a mobile station can then be determined from signals received at the base station from the mobile station. After the position of the mobile station has been determined, the base station can transmit signals to and receive signals from the mobile station is a second class channel with a narrow antenna lobe.
A method and apparatus for transmitting and receiving signals in a base station with an antenna array in a cellular communication system. The available communication channels are divided into a plurality of classes. The base station transmits signals to the mobile station in a first class of channels in a wide antenna lobe. The position of a mobile station can then be determined from signals received at the base station from the mobile station. After the position of the mobile station has been determined, the base station can transmit signals to and receive signals from the mobile station is a second class channel with a narrow antenna lobe.
Description
WO 95/09490 21~ 8 91~ 0 PCI~/SE9.~/00880 ~J8ING TWO C~R8~8 OF C~NNE~ WIT~ I)IFF}:~ENT CAPACITY
}~IX~D O~ q`~: INVEN~ION
The present invention relates to a cellular communication system with adaptive antenna arrays, and ~ore specifically to a cellular communication system which uses both wide adaptive antenna lobes and narrow adaptive antenna lobes for com-munication between base stations and mobile stations.
~A~GRo~ND OF 1~ INVENTIO~
The cellular industry has made phenomenal strides in commer-cial operations in the Un~ted states as well as the rest of the world. Growth in major metropolitan areas has far exceeded ~xpectations and is outstripping system capacity.
If this trend continues, the effects of rapid growth will soon be achieved in the smallest markets. Innovative solutions are required to meet these increasing capacity needs as well as to maintain high quality service and avoid rising prices.
~urthexmore, as the number of cellular users increases, the problems associated with ~o-channel interference become of increased importance.
~0 Current digital cellular systems employ base stations which separate mobile signals using ti~e and frequency ort-hogonality. Signals from a mobile propagate to a base station and the signals are received in a single or sometimes double antenna. The receiver processes the signal using ti~e and frequency orthogonality to separate signals from different users. It is then possible to equalize and detect the signals. While technigues such as ~reguency hopping and advanced coding techniques provide ways f~r lowering co-channel interference, they are inherently limited by the available freguency spectrum. However, the use of the directional sensitivity of adaptive antennas offers a new way , . - .,:: , , . , . . - .
~- WO 95/09490 21~ ~3 9 4 0 PCI~/SE9~/00880 of reducing co-channel interference. An adaptive antenna consists of an array of spatially distributed an~ennas.
Impinging on the array are signals from several transmitters.
By properly combining the antenna outputs, it is possible to extract indlvidual signals from the received superposition, even i~ they occupy the same frequency band. It is then possible to distinguish between spatially separated users by using narrow adaptive antenna lobes. This can be viewed as a way to utilize orthogonality in the spatial dimension.
Current digital cellular systems also employ base stations which use base antennas with wide antenna lobes, i.e., approximately 60, 120 or 360~. The base station receives signals from all mobile stations within the lobe. It is hence not necessary to know the position of the mobile station.
However, it is not possible to suppress mobiles transmitting from oth~r angles. The use of narrow adaptive antenna lobes requires that the position or more exactly, the best spatial filters for receptio~/transmission to and from the mobile station be ~nown. ~his implies that the spatial filters of the mobile ~ust be ~easured for each new call and after each handover between ~ase stations.
T~is measurement problem can be easily solved in many ap-plications. However, the problem is much more important in cellular mobile applications where the mobile stations change position and where communication channels fade quickly.
Furthermore, existing standards such as theGSM standard often as ume ~hat a wide antenna lobe is used so that ~aluable information can be sent directly to mobile stations with unknown positions. This implies that special care ~ust be taken so that informatio~ is not lost during the training of the adaptive antennas. Another consideration is the li~king to a channel, i.e., the fact that a mobile can be assign~d to one of a number of time and/or frequency orthogonal channels.
A new mobile may not be appropriate for a specific channel ~-~ woss/os4so 214 8 9 ~ O PCT/SE9~/00880 since, for example, it is close to an old mobile on the same channel. There is hence a desire to first measure, without disturbing any traffic, and then to link the mobile to an appropriate channel. In other words, one should maximize the spatial orthogonality.
Another important consideration is handover measurements.
There is a desire to have some channels transmitted in a wide lobe so tha~ the ~obile station can measure the signal strength of the sisnal from the base stations.
~MMARY OF ~B pI~C~08~RE
It is an obje~t of the present invention to provide a system wherein mobile stations with known and unknown positions can be used in the same system while the knowledge about the mobile's position at the same time can be utilized to reduce lS interference and increase system capacity. This object of the present invention is accomplished by using antenna arrays and by dividing t~e available traffic channels into a plurality of classes.
one embodiment of the present invention discloses a method of transmitting and receiving signals in a base station with an antenna array in a cellular communication system. First, the a~ailable communication channels are divided into a plurality of classes. The base station then transmits signals to mobile stations in a first ~lass of channels with a wide antenna lobe. The position of a ~obile station can ~hen be determined from signals received at the base station from the mobile station. After the position of the mobile station has been determined, the base station can transmit signals to and receive signals from the mobile station in a second class of channels with a narrow antenna lobe.
: .,:, .: ;., :,, :: , :: ~-., .. -. -. . :: - . : :, : , .:: , - .: . . : , ,, : , . ,, , - , , , :
WO 9S/09490 _ 21 ~ 8 9 9~ 0 PCrlSE9~/00880 BRI~F DEBCRIPTION OF TIIE DRAWING8 The present invention will now be described in more detail with re~erence to preferred embodiments of the present in~ention, given only by way of example, and illustrated in the accompanying drawings in which;
Figure 1 illustrates a block diagram of the relationship ~etween the transmitter and the receiver;
Figures 2(a)~(b) illustrates one antenna arrangement accor-ding to one embodiment of the present invention;
Figure 3 is a flow chart of a call set up routine according to one embodi~ent of the present invention;
Figure 4 illustrates an example of beam-forming according to one embodLment o~ the present invention;
Figure S illustrates a flow chart for detecting and demodulat- : ing a signal according to one embodiment of the present invention; : ~:
Figure 6 illustrates a block diagram ~f one embodiment of a part of ~he present invention;
: . ~
Figure 7(a)-(b) illustrates another antenna arrangement ~:
according to one embodiment of the present invention; and Figure 8 is a flow chart of a handover routine between base stations according to one embodiment of the present invention.
:, D~T~I~ D p~8C~PTION
~hile the following description is in the ~ontext of cellular .
~ommunication systems involving portable or mobile radio telephones and/or personal communication networks and a :~
. , , . , .. . ~ : . , . , , i woss/09490 21 4 PCT/SE9~100880 plurality of base stations, it wil:L be understood by those skilled in ~he arts that the present invention may be applied to other communications applications.
Figure 1 illustrates an overview picture of the link between a transmitter lO and a receiver 14. The transmitter and receiver are located in both the mobile station and the base stations, however for this discussion the transmitter 10 is in ~he mobile station and the receiver 14 is located at the base station. The transmitter 10 sends 2 signal to the receiver 14 through a channel 12. ~he channel 12 is considered to be a linear transfer function with an impulse respons~ h(t) which creates all the variations and phase and signal strength between the transmitter and the receiYer. The transmitted signal s(t) is affected by the channel impulse response h(t) to form a received signal r(t). The signal r(t) is received by the receiver 14 through an adaptive antenna array 20 which feeds the received signal into a channel estimator 16 which calculate~ a discrete approximation to h(t) called h(n). The discrete approxi~ation h(n) is then fed into the fading frequency esti~a~or 18 which produces an estimate of the doppler freguency for the mobile station. The received signal is also feed into a demodulator/detector 22 which uses the rhannel estimate and a doppler freguency estimate to demodu-late and dete^~t~he signal s According to one embodi~ent of the present invention, the number of available traffic channels are divided into a plurality of groups or classes, for instance, two. According to one embodiment of the present invention, the first class of channels has a disturbance situation so that the base station can receive signals using wide antenna lobes and transmit signals to the mobile station using a wide antenna lobe. The second class of channels has a disturbance situation so that the base station must trans~it signals using narrow antenna lobes in order to obtain acceptable quality. The difference : .
,. - , : . :: , : , . .
WO 9S109490 21 ~ 8 9 4 0 PCTISE94100880 between the channel classes is that a narrow lobe channel where the base station transmits signals in a narrow antenna lobe has a significantly higher spectral efficiency. The higher spectral efficiency cantypically be used to reduce the frequency reuse or to enable multiple spatial separated users to communicate over the same channel. Typically, the control channel and some of the traffic channels should be class one channels while most of the traffic channels should be class two channels. Furthermore, the class one channels should use the sa~e reuse distance and receiver algorithms as are presently available today, while the class two channels can have a smaller reuse distance than the class one channels.
Figure 2(a) illustrates a wide lobe channel. As is illustrated, the channel fl is broadcast over a wide area so that a plurality of m~bile stations can receive broadcast messages from the base station independently sf their posi-tion. Figure 2(b) illustrates a narrow lobe channel according to one embodiment of the present invention. As is illustra~
ted, the channel f2 is broadcasted to a limited area using the spatial filters of the adaptive antenna array to limit the directio~ of channel f2. As a result, the channel f2 can ~e used by a plurality of mobile stations to transmit and receive ihdividual messages, so long the mobile stations are not located in the same ~icinity.
According to one embodiment of the present invention, a base station transmits broadcast infor~ation, control messages, and paging messages on a wide lobe downlink channel. The base station also listens to all of the mobile stations in its assigned geographical area on a wide lobe uplink channel where, for example, mobile stations can send access requests to the base station. The base station collects the signals from the surrounding area at the antenna array. The collected signals are then entered into a signal processor which evaluates all of the individual signals to detect the presence ,, , ::, :., : : - , :
-` WO 95/09490 PCI'/SE9~/00880 - 21q~9~0 of a mobile station and to measure the position of the mobile station. The base station can then use these ~osition measurementS to reduce the width of the antenna lobe used to send signals to particular mobile stations, i.e., assign the mobile station a class two channel, after the position of the mobile station is determined to be above a predetermined level of certainty.
Class one channels are also used for setting up a new call ~nd for handover between base stations. A typical call set up routine according to one embodiment of the present inYention is illustrated in Figure 3. First, a mobile station sends an access message on a random access control channel, which is a class one channel, to a base station in step 300. The message is detected and used as a training sequence for the antenna algorithm, in s~ep 302, by de~oting the vector signal from the antenna array at time K as X~K)=~X,(K~...X~(~)]TWhere L is the number of array eleme~ts. The message sequence ~d(K)31~ can for example be used as the desired signal i~ a least-squares proble~ as follows. First, the linear combination of X(K~
closest to d(K) is determined, in other words, the vector ~ is determined so that (~-W~X~)2 is minimized. The determined vector, W0, where WO = tW...W2]T, can then be used to filter out the signal from the mobile. The base station then assigns the mobile statio~ an available class one channel for the re-quested call in step 304. The position of the mobile stationcan then be meas~red while the ~obile station uses the cla~s one channel to transmit data.
The position of the mobile station can, for example, be characterized by the previously determined vector W0. It is also possible to determine a direction of arrival of the signal from the mobile station usiAg well known algorithms such as beam-forming, MUSIC, ESPRIT, and WSF. An example of beam-forming i5 illustrated i~ Figure 4. The signal from a mobile station is received in a number of lobes, for example, :
. :- . : - . , .
. - : , ~ , . i .::, .
.. . . - . : . . .
-~ WO 9S/09490 PCr/SE9.1100880 ~3 2l9~89~o fo~r lobes. The beam-forming could, ~or example, be done with four separate directional antennas ~l02, with a Butler beam-former 404 on the radio frequency signal or at base b~nd with digital filters. Figure 5 illust:rates one process for detecting and demodulating a signal from a mobile station. In step 500, a signal from a mobile station is recei~ed at the antenna array 402. Lobes are then formed in step 502 and the output power from each of the lobes is measured in step 504.
The lobe with the largest measured power is then selected as the best lobe in step 506. The lobe number, i.e., 1,2,3,4, is then a characterization of the position of the mobile station.
The desired signal is then filtered out in step 508 and the signal is detected and demodula~ed in step 510. The resulting signal is then checked to see if it is useable, for example, has sufficient signal strength, in step 512. If the signal is not useable, the selected lobe is marked as used in step 514 and the routine returns to step 502.
Figure 6 illustrates one method for meas~ring ~he power of signals received from mobile station N51. The array of antennas 602 receive a plurality of signals, some of which are from MSl. The plurality of signals are then filtered in a spatial filter 604. The spatial filtering can reduce inter-~erence from other direc~ions in the uplink direction. It can also reduce the downlink disturbance from the base station towards the mobile station. In the uplink direction, the weights of the spatial filter Wl, W2, W3, and W~ are chosen so that the filtered signal Y(X) consists solely of the signals received fro~ the mobile station MSl. In the downlink direction, the weight of the spatial filter are chosen so that all of the signals for MSl reach ~Sl without disturbing ~S2.
~he filtered signal Y(X) is then sguared in a squaring means 606 to produce the ~omentaneous power of the mobile station MSl. The momentaneous power is then averaged in time in an int~grator 408 to produce t~e time averaged power of the mobile station MSl. Returning to Figure 3, as soon as the --~ wosslos4so PCT/SE9~/00880 21~89~o position and power level of the new mobile are determined in step 306, the mobile station can then be assigned a class two channel in step 308.
Tra~fic to and from mobiles with Xnown positions can be directed in specific directions using narrow antenna lobes.
As a result, interference is reduced and multiple mobiles can use the same frequency channel. According to one embodiment of the present invention, a single freguency channel can have up ta 5 users at the same time but is not li~ited thereto. ~
mobile t~at wants to access an AMPS-type FD~A system would typically send its access request or call setup reguest to a base station using a widelobe ohannel as indicated in Figure 2(a). The signal is processed by the base station and the mobile's position can then be measured. The mobile is then instructed to transmit and recei~e on a narrow band channel as illustrated in Figure 2(b).
An active mobile in a ADC-type TDMA system would, as illustrated in Figure 7(a)-(b), typically use one time slot for transmission to the base station and another timeslot for reception from the base station. This transmission would typically use narrowlobe channels with high spectral ef-ficiency as illustrated in Figure 7a. The mobile is the~ free for t~e rest of the ti~e slots to listen for information broadcasted from base stations in the general vicinity on widelobe channels as illustrated in Figure 7b.
A typical call handover routine according to one embodiment of the present invention is illustrated in Figure 8. When a first base station determines that a handover is required using one of the methods that are well known to one of ordi~ary skill in the art in step 800, the first base station hands of~ the mobile station to a second base station in step 802. The second base station then assigns the mobile station an available class one channel in step 804 so that the mobile :
:~ :
_ WO 95/09490 PCI/SE9.1/00880 2:~8940 station can continue the call in progress. The position of the mobile station is then gradually determined by either the base station or the mobile station in step 806. The second base station the assigns the mobile station an available class S two traffic channel in step 808. Furthermore, according to one embodiment of the present invention, while the mobile station is transmittiny on a class two channel, the mobile station can make handovermeasurements by monitoringthe class one channels as long as the signals are separated in time.
Accordi~g to another ~mhodiment of the present invention, the class two channels have antenna lobes-with variable widths, wherein all of the widths of the antenna lobes of class two channels are less than the width of antenna lobes of class one channels. As a result, as the position of a mobile station is gradually determined, the base station can gradually reduce t~e antenna lobe width of the class two channel assigned to the mobile statio~. As a result, the signal quality of the mobile station can be gradually increased.
It would be appreciated by those of ordinary skill in the art that the present invention can be ~mhodied in other specific forms without departing from the spirit or essential character thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restric-tive. The scope of the invention is indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalence thereof are intended to be embraced therein.
.. . . . . .. . . . . . . . . . .. ..
}~IX~D O~ q`~: INVEN~ION
The present invention relates to a cellular communication system with adaptive antenna arrays, and ~ore specifically to a cellular communication system which uses both wide adaptive antenna lobes and narrow adaptive antenna lobes for com-munication between base stations and mobile stations.
~A~GRo~ND OF 1~ INVENTIO~
The cellular industry has made phenomenal strides in commer-cial operations in the Un~ted states as well as the rest of the world. Growth in major metropolitan areas has far exceeded ~xpectations and is outstripping system capacity.
If this trend continues, the effects of rapid growth will soon be achieved in the smallest markets. Innovative solutions are required to meet these increasing capacity needs as well as to maintain high quality service and avoid rising prices.
~urthexmore, as the number of cellular users increases, the problems associated with ~o-channel interference become of increased importance.
~0 Current digital cellular systems employ base stations which separate mobile signals using ti~e and frequency ort-hogonality. Signals from a mobile propagate to a base station and the signals are received in a single or sometimes double antenna. The receiver processes the signal using ti~e and frequency orthogonality to separate signals from different users. It is then possible to equalize and detect the signals. While technigues such as ~reguency hopping and advanced coding techniques provide ways f~r lowering co-channel interference, they are inherently limited by the available freguency spectrum. However, the use of the directional sensitivity of adaptive antennas offers a new way , . - .,:: , , . , . . - .
~- WO 95/09490 21~ ~3 9 4 0 PCI~/SE9~/00880 of reducing co-channel interference. An adaptive antenna consists of an array of spatially distributed an~ennas.
Impinging on the array are signals from several transmitters.
By properly combining the antenna outputs, it is possible to extract indlvidual signals from the received superposition, even i~ they occupy the same frequency band. It is then possible to distinguish between spatially separated users by using narrow adaptive antenna lobes. This can be viewed as a way to utilize orthogonality in the spatial dimension.
Current digital cellular systems also employ base stations which use base antennas with wide antenna lobes, i.e., approximately 60, 120 or 360~. The base station receives signals from all mobile stations within the lobe. It is hence not necessary to know the position of the mobile station.
However, it is not possible to suppress mobiles transmitting from oth~r angles. The use of narrow adaptive antenna lobes requires that the position or more exactly, the best spatial filters for receptio~/transmission to and from the mobile station be ~nown. ~his implies that the spatial filters of the mobile ~ust be ~easured for each new call and after each handover between ~ase stations.
T~is measurement problem can be easily solved in many ap-plications. However, the problem is much more important in cellular mobile applications where the mobile stations change position and where communication channels fade quickly.
Furthermore, existing standards such as theGSM standard often as ume ~hat a wide antenna lobe is used so that ~aluable information can be sent directly to mobile stations with unknown positions. This implies that special care ~ust be taken so that informatio~ is not lost during the training of the adaptive antennas. Another consideration is the li~king to a channel, i.e., the fact that a mobile can be assign~d to one of a number of time and/or frequency orthogonal channels.
A new mobile may not be appropriate for a specific channel ~-~ woss/os4so 214 8 9 ~ O PCT/SE9~/00880 since, for example, it is close to an old mobile on the same channel. There is hence a desire to first measure, without disturbing any traffic, and then to link the mobile to an appropriate channel. In other words, one should maximize the spatial orthogonality.
Another important consideration is handover measurements.
There is a desire to have some channels transmitted in a wide lobe so tha~ the ~obile station can measure the signal strength of the sisnal from the base stations.
~MMARY OF ~B pI~C~08~RE
It is an obje~t of the present invention to provide a system wherein mobile stations with known and unknown positions can be used in the same system while the knowledge about the mobile's position at the same time can be utilized to reduce lS interference and increase system capacity. This object of the present invention is accomplished by using antenna arrays and by dividing t~e available traffic channels into a plurality of classes.
one embodiment of the present invention discloses a method of transmitting and receiving signals in a base station with an antenna array in a cellular communication system. First, the a~ailable communication channels are divided into a plurality of classes. The base station then transmits signals to mobile stations in a first ~lass of channels with a wide antenna lobe. The position of a ~obile station can ~hen be determined from signals received at the base station from the mobile station. After the position of the mobile station has been determined, the base station can transmit signals to and receive signals from the mobile station in a second class of channels with a narrow antenna lobe.
: .,:, .: ;., :,, :: , :: ~-., .. -. -. . :: - . : :, : , .:: , - .: . . : , ,, : , . ,, , - , , , :
WO 9S/09490 _ 21 ~ 8 9 9~ 0 PCrlSE9~/00880 BRI~F DEBCRIPTION OF TIIE DRAWING8 The present invention will now be described in more detail with re~erence to preferred embodiments of the present in~ention, given only by way of example, and illustrated in the accompanying drawings in which;
Figure 1 illustrates a block diagram of the relationship ~etween the transmitter and the receiver;
Figures 2(a)~(b) illustrates one antenna arrangement accor-ding to one embodiment of the present invention;
Figure 3 is a flow chart of a call set up routine according to one embodi~ent of the present invention;
Figure 4 illustrates an example of beam-forming according to one embodLment o~ the present invention;
Figure S illustrates a flow chart for detecting and demodulat- : ing a signal according to one embodiment of the present invention; : ~:
Figure 6 illustrates a block diagram ~f one embodiment of a part of ~he present invention;
: . ~
Figure 7(a)-(b) illustrates another antenna arrangement ~:
according to one embodiment of the present invention; and Figure 8 is a flow chart of a handover routine between base stations according to one embodiment of the present invention.
:, D~T~I~ D p~8C~PTION
~hile the following description is in the ~ontext of cellular .
~ommunication systems involving portable or mobile radio telephones and/or personal communication networks and a :~
. , , . , .. . ~ : . , . , , i woss/09490 21 4 PCT/SE9~100880 plurality of base stations, it wil:L be understood by those skilled in ~he arts that the present invention may be applied to other communications applications.
Figure 1 illustrates an overview picture of the link between a transmitter lO and a receiver 14. The transmitter and receiver are located in both the mobile station and the base stations, however for this discussion the transmitter 10 is in ~he mobile station and the receiver 14 is located at the base station. The transmitter 10 sends 2 signal to the receiver 14 through a channel 12. ~he channel 12 is considered to be a linear transfer function with an impulse respons~ h(t) which creates all the variations and phase and signal strength between the transmitter and the receiYer. The transmitted signal s(t) is affected by the channel impulse response h(t) to form a received signal r(t). The signal r(t) is received by the receiver 14 through an adaptive antenna array 20 which feeds the received signal into a channel estimator 16 which calculate~ a discrete approximation to h(t) called h(n). The discrete approxi~ation h(n) is then fed into the fading frequency esti~a~or 18 which produces an estimate of the doppler freguency for the mobile station. The received signal is also feed into a demodulator/detector 22 which uses the rhannel estimate and a doppler freguency estimate to demodu-late and dete^~t~he signal s According to one embodi~ent of the present invention, the number of available traffic channels are divided into a plurality of groups or classes, for instance, two. According to one embodiment of the present invention, the first class of channels has a disturbance situation so that the base station can receive signals using wide antenna lobes and transmit signals to the mobile station using a wide antenna lobe. The second class of channels has a disturbance situation so that the base station must trans~it signals using narrow antenna lobes in order to obtain acceptable quality. The difference : .
,. - , : . :: , : , . .
WO 9S109490 21 ~ 8 9 4 0 PCTISE94100880 between the channel classes is that a narrow lobe channel where the base station transmits signals in a narrow antenna lobe has a significantly higher spectral efficiency. The higher spectral efficiency cantypically be used to reduce the frequency reuse or to enable multiple spatial separated users to communicate over the same channel. Typically, the control channel and some of the traffic channels should be class one channels while most of the traffic channels should be class two channels. Furthermore, the class one channels should use the sa~e reuse distance and receiver algorithms as are presently available today, while the class two channels can have a smaller reuse distance than the class one channels.
Figure 2(a) illustrates a wide lobe channel. As is illustrated, the channel fl is broadcast over a wide area so that a plurality of m~bile stations can receive broadcast messages from the base station independently sf their posi-tion. Figure 2(b) illustrates a narrow lobe channel according to one embodiment of the present invention. As is illustra~
ted, the channel f2 is broadcasted to a limited area using the spatial filters of the adaptive antenna array to limit the directio~ of channel f2. As a result, the channel f2 can ~e used by a plurality of mobile stations to transmit and receive ihdividual messages, so long the mobile stations are not located in the same ~icinity.
According to one embodiment of the present invention, a base station transmits broadcast infor~ation, control messages, and paging messages on a wide lobe downlink channel. The base station also listens to all of the mobile stations in its assigned geographical area on a wide lobe uplink channel where, for example, mobile stations can send access requests to the base station. The base station collects the signals from the surrounding area at the antenna array. The collected signals are then entered into a signal processor which evaluates all of the individual signals to detect the presence ,, , ::, :., : : - , :
-` WO 95/09490 PCI'/SE9~/00880 - 21q~9~0 of a mobile station and to measure the position of the mobile station. The base station can then use these ~osition measurementS to reduce the width of the antenna lobe used to send signals to particular mobile stations, i.e., assign the mobile station a class two channel, after the position of the mobile station is determined to be above a predetermined level of certainty.
Class one channels are also used for setting up a new call ~nd for handover between base stations. A typical call set up routine according to one embodiment of the present inYention is illustrated in Figure 3. First, a mobile station sends an access message on a random access control channel, which is a class one channel, to a base station in step 300. The message is detected and used as a training sequence for the antenna algorithm, in s~ep 302, by de~oting the vector signal from the antenna array at time K as X~K)=~X,(K~...X~(~)]TWhere L is the number of array eleme~ts. The message sequence ~d(K)31~ can for example be used as the desired signal i~ a least-squares proble~ as follows. First, the linear combination of X(K~
closest to d(K) is determined, in other words, the vector ~ is determined so that (~-W~X~)2 is minimized. The determined vector, W0, where WO = tW...W2]T, can then be used to filter out the signal from the mobile. The base station then assigns the mobile statio~ an available class one channel for the re-quested call in step 304. The position of the mobile stationcan then be meas~red while the ~obile station uses the cla~s one channel to transmit data.
The position of the mobile station can, for example, be characterized by the previously determined vector W0. It is also possible to determine a direction of arrival of the signal from the mobile station usiAg well known algorithms such as beam-forming, MUSIC, ESPRIT, and WSF. An example of beam-forming i5 illustrated i~ Figure 4. The signal from a mobile station is received in a number of lobes, for example, :
. :- . : - . , .
. - : , ~ , . i .::, .
.. . . - . : . . .
-~ WO 9S/09490 PCr/SE9.1100880 ~3 2l9~89~o fo~r lobes. The beam-forming could, ~or example, be done with four separate directional antennas ~l02, with a Butler beam-former 404 on the radio frequency signal or at base b~nd with digital filters. Figure 5 illust:rates one process for detecting and demodulating a signal from a mobile station. In step 500, a signal from a mobile station is recei~ed at the antenna array 402. Lobes are then formed in step 502 and the output power from each of the lobes is measured in step 504.
The lobe with the largest measured power is then selected as the best lobe in step 506. The lobe number, i.e., 1,2,3,4, is then a characterization of the position of the mobile station.
The desired signal is then filtered out in step 508 and the signal is detected and demodula~ed in step 510. The resulting signal is then checked to see if it is useable, for example, has sufficient signal strength, in step 512. If the signal is not useable, the selected lobe is marked as used in step 514 and the routine returns to step 502.
Figure 6 illustrates one method for meas~ring ~he power of signals received from mobile station N51. The array of antennas 602 receive a plurality of signals, some of which are from MSl. The plurality of signals are then filtered in a spatial filter 604. The spatial filtering can reduce inter-~erence from other direc~ions in the uplink direction. It can also reduce the downlink disturbance from the base station towards the mobile station. In the uplink direction, the weights of the spatial filter Wl, W2, W3, and W~ are chosen so that the filtered signal Y(X) consists solely of the signals received fro~ the mobile station MSl. In the downlink direction, the weight of the spatial filter are chosen so that all of the signals for MSl reach ~Sl without disturbing ~S2.
~he filtered signal Y(X) is then sguared in a squaring means 606 to produce the ~omentaneous power of the mobile station MSl. The momentaneous power is then averaged in time in an int~grator 408 to produce t~e time averaged power of the mobile station MSl. Returning to Figure 3, as soon as the --~ wosslos4so PCT/SE9~/00880 21~89~o position and power level of the new mobile are determined in step 306, the mobile station can then be assigned a class two channel in step 308.
Tra~fic to and from mobiles with Xnown positions can be directed in specific directions using narrow antenna lobes.
As a result, interference is reduced and multiple mobiles can use the same frequency channel. According to one embodiment of the present invention, a single freguency channel can have up ta 5 users at the same time but is not li~ited thereto. ~
mobile t~at wants to access an AMPS-type FD~A system would typically send its access request or call setup reguest to a base station using a widelobe ohannel as indicated in Figure 2(a). The signal is processed by the base station and the mobile's position can then be measured. The mobile is then instructed to transmit and recei~e on a narrow band channel as illustrated in Figure 2(b).
An active mobile in a ADC-type TDMA system would, as illustrated in Figure 7(a)-(b), typically use one time slot for transmission to the base station and another timeslot for reception from the base station. This transmission would typically use narrowlobe channels with high spectral ef-ficiency as illustrated in Figure 7a. The mobile is the~ free for t~e rest of the ti~e slots to listen for information broadcasted from base stations in the general vicinity on widelobe channels as illustrated in Figure 7b.
A typical call handover routine according to one embodiment of the present invention is illustrated in Figure 8. When a first base station determines that a handover is required using one of the methods that are well known to one of ordi~ary skill in the art in step 800, the first base station hands of~ the mobile station to a second base station in step 802. The second base station then assigns the mobile station an available class one channel in step 804 so that the mobile :
:~ :
_ WO 95/09490 PCI/SE9.1/00880 2:~8940 station can continue the call in progress. The position of the mobile station is then gradually determined by either the base station or the mobile station in step 806. The second base station the assigns the mobile station an available class S two traffic channel in step 808. Furthermore, according to one embodiment of the present invention, while the mobile station is transmittiny on a class two channel, the mobile station can make handovermeasurements by monitoringthe class one channels as long as the signals are separated in time.
Accordi~g to another ~mhodiment of the present invention, the class two channels have antenna lobes-with variable widths, wherein all of the widths of the antenna lobes of class two channels are less than the width of antenna lobes of class one channels. As a result, as the position of a mobile station is gradually determined, the base station can gradually reduce t~e antenna lobe width of the class two channel assigned to the mobile statio~. As a result, the signal quality of the mobile station can be gradually increased.
It would be appreciated by those of ordinary skill in the art that the present invention can be ~mhodied in other specific forms without departing from the spirit or essential character thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restric-tive. The scope of the invention is indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalence thereof are intended to be embraced therein.
.. . . . . .. . . . . . . . . . .. ..
Claims (23)
1. A method for transmitting and receiving signals at a base station with an antenna array in a cellular communication system, comprising the steps of:
dividing available communication channels into a plurality of classes;
transmitting signals to a plurality of mobile stations in a first class of channels with a wide antenna lobe;
determining position of a mobile station from signals received from said mobile station;
transmitting signals to said mobile station in a second class of channels with a narrow antenna lobe when the position of said mobile is determined; and receiving signals from said mobile station with an adjustable lobe widths on both channel classes.
dividing available communication channels into a plurality of classes;
transmitting signals to a plurality of mobile stations in a first class of channels with a wide antenna lobe;
determining position of a mobile station from signals received from said mobile station;
transmitting signals to said mobile station in a second class of channels with a narrow antenna lobe when the position of said mobile is determined; and receiving signals from said mobile station with an adjustable lobe widths on both channel classes.
2. A method according to claim 1, wherein said first class of channels is used for call set-up.
3. A method according to claim 2, wherein the position of said mobile station is determined by:
measuring the power level of signals received from said mobile station; and determining a proper antenna lobe for a newly connected mobile station.
measuring the power level of signals received from said mobile station; and determining a proper antenna lobe for a newly connected mobile station.
4. A method according to claim 1, wherein said base station assigns said mobile station to a channel in said second class of channels after the position of said mobile station is determined to be above a predetermined level of certainty.
5. A method according to claim 1, wherein said first class of channels is used for hangover between base stations.
6. A method according to claim 5, further comprising the steps of:
transmitting and receiving signals at a mobile station on a channel in said second class of channels; and performing handover measurements of signals received at said mobile station on said first class of channels.
transmitting and receiving signals at a mobile station on a channel in said second class of channels; and performing handover measurements of signals received at said mobile station on said first class of channels.
7. A method according to claim 1, wherein at least one control channel and a minority of traffic channels belong to the first class of channels.
8. A method according to claim 1, wherein said second class of channels has a smaller reuse distance than said first class of channels.
9. A method according to claim 1, wherein said second class of channels can have more than one user for each channel.
10. A method according to claim 1, wherein said second class of channels can have variable antenna lobe widths.
11. A method according to claim 10, wherein the base station gradually reduces the antenna lobe width of a second class channel assigned to a mobile station as the base station gradually determines the position of said mobile station.
12. A communication system with at least one base station having an antenna arrays, comprising;
means for transmitting signals from a base station to a plurality of mobile stations on a plurality of classes of channels;
means for receiving signals from a plurality of mobile stations at a base station on a plurality of classes of channels;
means for determining a position of a mobile station from said received signals, wherein said base station transmits signals in a first class of channels with a wide antenna lobe and said base station transmits signals in a second class of channels with a narrow antenna lobe when the position of said mobile station has been determined.
means for transmitting signals from a base station to a plurality of mobile stations on a plurality of classes of channels;
means for receiving signals from a plurality of mobile stations at a base station on a plurality of classes of channels;
means for determining a position of a mobile station from said received signals, wherein said base station transmits signals in a first class of channels with a wide antenna lobe and said base station transmits signals in a second class of channels with a narrow antenna lobe when the position of said mobile station has been determined.
13. A cellular communication system according to claim 12, wherein said first class of channels is used for call set-up.
14. A cellular communication system according to claim 12, wherein said first class of channels is used for handover between base stations.
15. A cellular communication system according to claim 13, wherein said position determining means comprises:
means for determining a power level of a signal from said mobile station; and means for determining a proper antenna lobe for a newly connected mobile station.
means for determining a power level of a signal from said mobile station; and means for determining a proper antenna lobe for a newly connected mobile station.
16. A cellular communication system according to claim 13, wherein said base station assigns said mobile station to a channel in said second class of channels after the position of said mobile is determined to be above a predetermined level of certainty.
17. A cellular communication system according to claim 14, wherein a mobile station contains means for transmitting and receiving signal on a channel in said second class of channels and means for measuring handover measurements on a channel in said first class of channels.
18. A cellular communication system according to claim 17, said mobile station further comprising means for transmitting and receiving signals on a channel in said first class of channels.
19. A cellular communication system according to claim 12, wherein at least one control channel and a minority of traffic channels belong to the first class of channels.
20. A cellular communication system according to claim 12, wherein said second class of channels have a smaller reuse distance than said first class of channels.
21. A cellular communication system according to claim 12, wherein said second class of channels can have more than one user for each channel.
22. A cellular communication system according to claim 12, wherein said second class of channels have variable antenna lobe widths.
23. A cellular communication system according to claim 22, wherein the base station gradually reduces the antenna lobe width of a class two channel assigned to a mobile station as the base station gradually determines the position of said mobile station.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12655893A | 1993-09-27 | 1993-09-27 | |
| US126,558 | 1993-09-27 | ||
| PCT/SE1994/000880 WO1995009490A1 (en) | 1993-09-27 | 1994-09-23 | Using two classes of channels with different capacity |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2148940A1 true CA2148940A1 (en) | 1995-04-06 |
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ID=22425496
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2148940A Abandoned CA2148940A1 (en) | 1993-09-27 | 1994-09-23 | Using two classes of channels with different capacity |
Country Status (14)
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| US (1) | US5615409A (en) |
| EP (1) | EP0671085B1 (en) |
| JP (2) | JPH08508865A (en) |
| KR (1) | KR100344503B1 (en) |
| CN (1) | CN1064797C (en) |
| AU (1) | AU677717B2 (en) |
| CA (1) | CA2148940A1 (en) |
| DE (1) | DE69433983T2 (en) |
| FI (1) | FI952582A0 (en) |
| NZ (1) | NZ274026A (en) |
| RU (1) | RU2154903C2 (en) |
| SG (1) | SG49352A1 (en) |
| TW (1) | TW351886B (en) |
| WO (1) | WO1995009490A1 (en) |
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- 1994-09-23 EP EP94928540A patent/EP0671085B1/en not_active Expired - Lifetime
- 1994-09-23 CN CN94190819A patent/CN1064797C/en not_active Expired - Lifetime
- 1994-09-23 JP JP7510248A patent/JPH08508865A/en active Pending
- 1994-09-23 WO PCT/SE1994/000880 patent/WO1995009490A1/en active IP Right Grant
- 1994-09-23 AU AU77935/94A patent/AU677717B2/en not_active Ceased
- 1994-09-23 NZ NZ274026A patent/NZ274026A/en unknown
- 1994-09-23 DE DE69433983T patent/DE69433983T2/en not_active Expired - Lifetime
- 1994-09-23 SG SG1996012124A patent/SG49352A1/en unknown
- 1994-09-23 CA CA2148940A patent/CA2148940A1/en not_active Abandoned
- 1994-09-23 RU RU95112471/09A patent/RU2154903C2/en active
- 1994-09-23 KR KR1019950702126A patent/KR100344503B1/en not_active IP Right Cessation
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1995
- 1995-05-26 FI FI952582A patent/FI952582A0/en unknown
- 1995-09-25 US US08/533,104 patent/US5615409A/en not_active Expired - Lifetime
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2004
- 2004-09-24 JP JP2004276997A patent/JP2005020790A/en active Pending
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| KR100344503B1 (en) | 2002-10-31 |
| CN1064797C (en) | 2001-04-18 |
| KR950704872A (en) | 1995-11-20 |
| TW351886B (en) | 1999-02-01 |
| DE69433983T2 (en) | 2005-09-29 |
| RU2154903C2 (en) | 2000-08-20 |
| JP2005020790A (en) | 2005-01-20 |
| WO1995009490A1 (en) | 1995-04-06 |
| AU7793594A (en) | 1995-04-18 |
| FI952582A (en) | 1995-05-26 |
| DE69433983D1 (en) | 2004-10-14 |
| US5615409A (en) | 1997-03-25 |
| EP0671085B1 (en) | 2004-09-08 |
| CN1116024A (en) | 1996-01-31 |
| EP0671085A1 (en) | 1995-09-13 |
| FI952582A0 (en) | 1995-05-26 |
| SG49352A1 (en) | 1998-05-18 |
| JPH08508865A (en) | 1996-09-17 |
| NZ274026A (en) | 1997-11-24 |
| AU677717B2 (en) | 1997-05-01 |
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