Title of Invention	METHOD AND APPARATUS FOR COMBINED SPATIAL AND TEMPORAL SIGNAL EQUALIZATION IN A COMMUNICATION SYSTEM WITH MULTIPLE RECEIVER ANTENNAS
Abstract	ABSTRACT "Method and apparatus for combined spatial and temporal signal equalization in a communication system with multiple receiver antennas" The present invention relates to a communication receiver ( 400 ) minimizes a combined local and global mean square error for signal equalization. A base station ( 101 ) or a mobile station ( 102-104 ) may include a plurality of antennas ( 292 ) for receiving a plurality of signals transmitted from a common source. The plurality of signals carry a common stream of data symbols. A pre-processing block ( 299 ) processes the received signals to produce a plurality of processed received signals ( 298 ). A signal equalizer ( 401 ) minimizes a combined local and global MSE over the processed received signals ( 298 ) to produce a combined signal ( 499 ). A decoder decodes the combined signal ( 499 ) to retrieve the stream of data symbols. A processor is configured for combining a local MSE and a global MSE in accordance with an adjustable weighting factor a to produce the combined local and global MSE. Figure 3.

Title of Invention

METHOD AND APPARATUS FOR COMBINED SPATIAL AND TEMPORAL SIGNAL EQUALIZATION IN A COMMUNICATION SYSTEM WITH MULTIPLE RECEIVER ANTENNAS

Abstract

ABSTRACT "Method and apparatus for combined spatial and temporal signal equalization in a communication system with multiple receiver antennas" The present invention relates to a communication receiver ( 400 ) minimizes a combined local and global mean square error for signal equalization. A base station ( 101 ) or a mobile station ( 102-104 ) may include a plurality of antennas ( 292 ) for receiving a plurality of signals transmitted from a common source. The plurality of signals carry a common stream of data symbols. A pre-processing block ( 299 ) processes the received signals to produce a plurality of processed received signals ( 298 ). A signal equalizer ( 401 ) minimizes a combined local and global MSE over the processed received signals ( 298 ) to produce a combined signal ( 499 ). A decoder decodes the combined signal ( 499 ) to retrieve the stream of data symbols. A processor is configured for combining a local MSE and a global MSE in accordance with an adjustable weighting factor a to produce the combined local and global MSE. Figure 3.

Full Text	METHOD AND APPARATUS FOR COMBINED SPATIAL AND TEMPORAL SIGNAL EQUALIZATION IB A COMMUNICATION SYSTEM WITH MULTIPLE RECEIVER ANTENNAS Field [1001]The present invention relates generally to the field of communications, and more specifically, to communications over a dispersive channel with multiple receiver antennas. Background [10021The communication channel between a transmitter and a receiver may be time varying and dispersive. The dispersion of the channel may result in multipath and inter-symbol interference (ISI) and a receiver may need special processing to counteract these and possibly other time varying effects. Such a receiver may include an equalizer for reducing the effect of multipath interference and ISI. [1003]To this end as well as others, there is a need for an effective equalizer in a communication system. SUMMARY [1004]A communication receiver performs signal equalization by minimizing a combined local and global mean square error (MSE). A receiver may include a pluralily of antennas for receiving a plurality of signals transmitted from a common source. The plurality of signals carry a common stream of data symbols. A pre-processing block processes the received signals to produce a plurality of processed received signals. In local optimization, the temporal coefficients for the signals from different antenna are optimized based solely on minimfzing the MSE between the transmitted symbol and the local estimate of the transmitted symbol. In Global Optimization, the temporal coefficients and spatial combiner weights for signals from all antennas are optimized jointly to minimize the global MSE. A signal equalizer minimizes a combined local and global MSE over the processed received signals to produce a combined signal. A decoder decodes the combined signal to retrieve the stream of data symbols. A processor is configured for combining a local MSE and a global MSE in accordancs with a weighting factor a to produce the combined local and global MSE. The processor is configured for adjusting the weighting factor a' to achieve a corresponding effect of adaptation speed and error magnitude in minimizing the combined local and global the MSE. BRIEF DESCRIPTION OF THE DRAWINGS [1005]Th6 features, objects, 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: [lOOejFJG. 1 iJJustrates a communication system capab}e of operating in accordance with various embodiments of the invention; [1007]FIG. 2 illustrates a receiver block diagram in a communication system receiver for minimizing a combined local and global mean square error for a signal equalization; and [1008JFIG. 3 illustrates a flow chart for minimizing the combined local and global mean square error for a signal equalization. Detailed Description of the Preferred Embodiment{s) [IG09] Various aspects of the invention may be incorporated in a system for wireless communications in accordance with the code division multiple access (CDMA) technique. Various CDMA communication techniques have been disciosed and descritied in various standards published by the Telecommunication Industry Association (TIA). Such standards include the TIA/EIA-95 standard, TlA/ElA-l3-2000 standard, lMT-2000 standard, and WCDMA standard, all incorporated by reference herein. In addition, the specification defined as 'TIA/EiA/lS-856 cdma2000 High Rate Packet Data Air interface Specification," incorporated by reference herein, also provides for a system wherein one or more aspects of the invention may be incorporated. A copy of the standards may be obtained by accessing the world wide web at the address: http-.//www.cdq.orq. or by writing to TIA, Standards and Technology Department, 2500 Wilson Boulevard, Arlington, VA 22201, United States of America. The specification generally identified as WCDMA standard, may be obtained by contacting 3GPP Support Office, 650 Route des Lucioles-Sophia Antipolis, Valbonne-France. [lOlOJThis invention relates generally to a novel and improved method and apparatus for signal equalization in a communication system. One or more exemplary embodiments described herein are set forth in the context of a wireless data communication system. While use within this context is advantageous, different embodiments of the invention may be incorporated in different environments or configurations. In general, the various systems described herein may be formed using software-controlled processors, integrated circuits, or discrete logic. The data, instructions, commands, information, signals, symbols, and chips that may be referenced throughout the application are advantageously represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or a combination thereof. In addition, the blocks shown in each block diagram may represent hardware or method steps. [1011]F1G. 1 illustrates a general block diagram of a communication system 100 capable of operating in accordance with any of the code division multiple access (CDMA) communication system standards. Generally, communication system 100 includes a base station 101 that provides communication links between a number of mobile stations, such as mobile stations 102-104, and between the mobile stations 102-104 and a wireline network 105. Base station 101 may include a number of components, such as a mobile station controller, a base station controller, and a radio frequency transceiver. For simplicity, such components are not shown. Base station 101 may also be in communication with other base stations (not shown). Base station 101 communicates with each mobile station 102-104 via a fonward link. The fonward link may be maintained by a fonward link signal transmitted from base station 101. The fonward link signals targeted for several mobile stations 102-104 may be summed to form a fonward link signal 106. Each of the mobile stations 102-104 receiving fonward link signal 106 decodes the forward link signal 106 to extract the information ttial is targeted for its user. At the receiving end, the receiver may treat as interference the portion of the received fonward link signal 106 targeted for others. [1012]fi^obile stations 102-104 communicate with base station 101 via a corresponding reverse link. Each reverse link is maintained by a reverse link signal, such as reverse link signals 107-109 for respectively mobile stations 102-104. Base station 101 may also transmit a predefined series of data bits on a pilot channel via the forward link to all mobile stations to assist eacf) mobile sfatJon in decoding the fonvard link signal 106. Each of the mobile stations 102-104 may transmit a pilot channel to base station 101. The pilot channel transmitted from a mobile station may be used for decoding the information carried by the reverse link signal transmitted from the same mobile station. The use and operation of a pilot channel are well known. A transmitter and a receiver for communicating via the fon/vard and reverse links are included in each mobile station 102-104, and base station 101. [1013]A block diagram of a receiver 400 is shown in FIG. 2. Receiver 400 may have several antennas 292-1 to 292-K for receiving the transmitted signal waveform. The signals received at antennas 292-1 to 292-K may be processed in corresponding pre-processing blocks 299-1 to 299-K to produce corresponding signals 298-1 to 298-K. The pre-processing blocks 299-1 to 299-K may include several operations not shown, such as RF/IF downconvertors, AGC {automatic gain control) compensation, A/D (analog-to-digital) conversion. The signals 298-1 to 298-K pass through an equalizer 401 to present a signal 499 for the decoder. The signals received at antennas 292-1 to 292-K originate from a common source and carry the same stream of data symbols y[n}, where "n" represents the temporal index of the symbols in the received data stream. t1014]tn communications system 100, the stream of data symbols yfn} may be transmitted from any of the mobile stations 102-104 through a communication channel to receiver 400 in base station 101, or from a base station 101 to any of the mobile stations 102-104. Receiver 400 may be incorporated in base station 101 for receiving signals from a mobile station over a dispersive channsJ, or in a mobile station 102-104 for receiving signals from base station 101 over a dispersive channel. Equalizer 401 may include a number of finite impulse response (FIR) filters 470-1 to 470-K. Although several filters 470-1 to 470-K are shown in FIG. 2, the implementation of the filters may be different in various embodiments. In one case, one filter may be used repeatedly to process aii the signals 296-1 to 296-K. In another case, a filter may be dedicated to each signal 298-1 to 298-K from the antennas 292-1 to 292-K. The equalizer for the path from the mth antenna may be a tapped delay line FIR filter with temporal coefficients Cmfn}. Use and operation of FIR filters are well known in the art. [1015]The output of each of the filters 470-1 to 470-K represents an estimate of a transmitted data symbol in the data stream y[n]. The output of where the FIR filter 470-1 has 2M+1 taps given by [Cj^fn] : ^=-M, ..., M\, ' denotes complex conjugation, and {Xt[n,k] :k= -M, .... /W} denotes the tapped delay-line contents at time n. The outputs of filters 470-1 to 470-K are scaled by tt>e multipliers 480-1 to 4ao-K each of which has an associated spatial coefficient Sm/n/. After the scaling operation, the resulting signals are summed in a combiner 490 to fomi a combined signal 499 which represents a {Cj'ln]: k=-M. ..., M} and the spatial coefficients Smln], for each m, can be optimized in accordance with an embodiment. The signal 499 would then carry an estimate of the transmitted data symbols that could be decoded with improved reliability. The temporal coefficients Cmlnj and spatial combiner weights Sr^n], for m=:l,...,K, may be optimized using the Minimum Mean Square Error (MMSE) criterion in several possible ways. One method, called Local Optimization, optimizes the temporal coefficients Cmlr>] for the m-th antenna based solely on minimizing the MSE between the transmitted symbol y{n} and the local estimate of the transmitted symbol y„[n], i.e., the FIR output signal 470-m for the m-th antenna branch. The temporal coefficients Cn^n]are selected to minimize the Locay WSH defined as: After the temporal coefficients Cm[n} for each antenna branch are determined, the spatial combiner weights S^^n} are chosen to minimize the mean square error (MSE) in the combined output signal >[«]. [1017]Another method, called Global Optimization, optimizes the temporal coefficients Ca,[n} and spatial combiner weights Stn[n] for all antennas jointly, using the combined output signal y[n]. For Global Optimization, the temporal coefficients and combiner weights are selected [1019]These respective optimizations may be carried out using adaptive signal processing algorithms that are well known in the art, e.g., the Least Mean Square (LMS) algorithm and its variants. When such an adaptive algorithm is used for optimizing the temporal coefficients Cm/h/and spatial coefficients Sm[n], the number of samples (i.e. the amount of training time) required for the coefficients to converge to their steady-stale {i.e., MMSE-optimal) values is greater for Global Optimization than for Local Optimization. However, the steady-state MSE is generally lower for Global Optimization. The present embodiment, called Combined Global-Local Optimization, improves on both these approaches to achieve a balance between low steady stgte MSE and fast convergence time. When a is set equal to zero, minimizing the Combined MSB amounts to Global Optimization, whereas if a is set equal to zero, minimizing the combined MSE amounts to Local Optimization. In the embodiment, the value for a may be any number between zero and one (0 t1021]Jn accordance with an embodiment, once a particular value of a has been selected, one can choose step-size parameters Ac and a^ and update the temporal coefficients Cm[n] and spatial coefficients Sn^n} in an iterative fashion. For example, the temporal and spatial coefficients where k indexes the coefficients in the FIR filter of 470-1, Ac is the step-size parameter for the temporal coefficients and Ci[n+i] denotes the updated temporal coefficients at time n+1. Next, for a fixed set of temporal wfiers zls Is tfie step-size parameter for the spatial coefficients and St[n] denotes ttie updated spatial coefficients at time n+1. The temporai coefficients CmfnJ and spatial coefflcienis Sn^nJ for the other antenna branches are updated analogously. The step-size parameters Ac and As can be any values which guarantee convergence of the iterative updates. Methods for selecting step-size parameters meeting these requirements are well known in the art. Furthermore, it follows by methods well known in the art that these nested iterations converge to a solution which achieves the CombinedMSE. [1022]FiG. 3 shows a flow chart 600 depicting one or more steps necessary to perfomn a combined optimization of the temporal coefficients Cm[n] and spatial coefficients Sm[n]. Various steps of the flow chart 600 may be performed by a control system. At step 601, the temporal coefficients Cm[n] and spatial coefficients Sn4n] are initialized and the initial values of the parameters ct, Ac and As are selected. At step 602, an estimate yjn] of the transmitted symbol is generated for the m-th antenna branch using Xm[n}, the data stream received on antenna m, and the temporal coefficients Cm[n]. At step 603, the estimates on each of the antenna branches are combined, using the spatial combiner coefficients Sm[n], to generate a combined estimate y[n} of the data symbol. The combined estimatB may be passed at step 604 to a decoder and may be evaluated in step 605 to determine whether additional updates of the temporal and spatial coefficients is required. Additional updates may not be necessary when the MSE error is at an acceptably small level. At step 606, the counter is incremented for the next data symbol and the process proceeds to step 602. At step 607 and 608, the values of the temporal coefficients Cm[n] and spatial coefficients S^n] are updated in accordance with the parameters a, Ac and As- At step 609 the parameters a, Ac and As may be adjusted, if desired, from the initial values set at step 601. For example, by adjusting a, the compromise between Local Optimization and Giobal Optimization can be controlled. When the value for a approaches zero, the updates are effectively those of Global Optimization rather than Local Optimization. Similarly, when the value for a approaches one, the updates are effectively those of Local Optimization rather than Global Optimization. This allows the possibility of trading off faster convergence for increased magnitude of the tJISE error, and vice-versa. Reducing the values for the step-size parameters Ac and As yields lower steady-state MSE at the expense of slower convoTgence of the iterations. Increasing the values for the step-size parameters Ac and As speeds up the convergence of the iterations but results in increased steady-state MSE. At step 610, the counter is incremented for the next pilot symbol. At step 611, the process deterrnines whether the last data symbol in the training-interval has been processed. If additional processing over the same stream of data is desired, the proceeds to step 602. [1023]Those of skill in the art would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scc^e of the present invention. [1024]The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed witti a general putpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device. discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. t1025]The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write Information to, the storage medium. In the alternative, the storage medium may be Integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. [1026]The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. The 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 the use of the inventive faculty. 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: WE CLAIM 1. A method for combined spatial and temporal signal equalization in a communication system with multiple receiver antennas comprising: receiving a plurality of signals from a common source, wherein said plurality of signals carries a common stream of data symbols; combining a local MSE and a global MSE in accordance with a weighting factor to produce said combined local and global MSE; and minimizing said combined local and global mean square error (MSE) over said received signals. 2. The method as claimed in claim 1, wherein said weighting factor has a value between zero and one. 3. The method as claimed in claim 1, comprising: determining temporal and spatial coefficients for said combined global and local MSE based on said weighting factor. 4. The method as claimed in claim 3, comprising; adjusting said temporal coefficients in accordance with a temporal coefficient step size for said minimizing of combined local and global MSE. 5. The method as claimed in claim 4, comprising: adjusting said temporal coefficient step size for said minimizing of combined local and global MSE. 6. The method as claimed in claim 3, comprising; adjusting said spatial coefficients in accordance with a spatial coefficient step size for said minimizing of combined local and global MSE. 7. The method as claimed in claim 6, comprising: adjusting said spatial coefficient step size for said minimizing said combined local and global MSE. 8. The method as claimed m claim 1, comprising: adjusting said weighting factor to achieve a corresponding effect of at least one of processing speed and error magnitude in said minimizing said combined local and global MSE. 9. The method as claimed in claim 1, comprising: producing a combined signal after said minimizing said combined local and global MSE over said received signals. 10. The method as claimed 1, in claim further comprising: decoding said combined signal to retrieve said common stream of data symbols. U. The method as claimed in claim 1, comprising: combining local and global MSE in accordance with a CombinedMSE=a(E(y[n]-yi[n]f+ E\|y[n]-y2[n]\|'+...+ Eiy[n]-yK[n]p}+(I+ a) {E\|y[n]-y[n])^} wherein a is a weighting factor. 12. An apparatus for combined spatial and temporal signal equalization in a communication system with multiple receiver antennas comprising: a receiver for receiving a plurality of signals from a common source, wherein said plurality of signals carries a common stream of data symbols; a processor for combining a local MSE and a global MSE in accordance with a weighting factor to produce said combined local and global MSE minimization; and an equalizer for minimizing said combined local and global mean square error (MSE) over said received signals. 13. The apparatus as claimed in claim 12, wherein said weighting factor has a value between zero and one. 14. The apparatus as claimed in claim 12, comprising: a decoder for decoding said combined signal to retrieve said common stream of data symbols. 15. The apparatus as claimed in claim 12, comprising a plurality of antennas coupled to said receiver for correspondingly receiving said plurality of signals. 16. The apparatus as claimed in claim 12, configured to perform the method claimed in any one of the claims 1-11.

Full Text

METHOD AND APPARATUS FOR COMBINED SPATIAL AND TEMPORAL SIGNAL EQUALIZATION IB A COMMUNICATION SYSTEM WITH MULTIPLE RECEIVER ANTENNAS
Field
[1001]The present invention relates generally to the field of communications, and more specifically, to communications over a dispersive channel with multiple receiver antennas.
Background
[10021The communication channel between a transmitter and a receiver may be time varying and dispersive. The dispersion of the channel may result in multipath and inter-symbol interference (ISI) and a receiver may need special processing to counteract these and possibly other time varying effects. Such a receiver may include an equalizer for reducing the effect of multipath interference and ISI.
[1003]To this end as well as others, there is a need for an effective equalizer in a communication system.
SUMMARY
[1004]A communication receiver performs signal equalization by minimizing a combined local and global mean square error (MSE). A receiver may include a pluralily of antennas for receiving a plurality of signals transmitted from a common source. The plurality of signals carry a common stream of data symbols. A pre-processing block processes the received

signals to produce a plurality of processed received signals. In local optimization, the temporal coefficients for the signals from different antenna are optimized based solely on minimfzing the MSE between the transmitted symbol and the local estimate of the transmitted symbol. In Global Optimization, the temporal coefficients and spatial combiner weights for signals from all antennas are optimized jointly to minimize the global MSE. A signal equalizer minimizes a combined local and global MSE over the processed received signals to produce a combined signal. A decoder decodes the combined signal to retrieve the stream of data symbols. A processor is configured for combining a local MSE and a global MSE in accordancs with a weighting factor a to produce the combined local and global MSE. The processor is configured for adjusting the weighting factor a' to achieve a corresponding effect of adaptation speed and error magnitude in minimizing the combined local and global the MSE.
BRIEF DESCRIPTION OF THE DRAWINGS
[1005]Th6 features, objects, 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:
[lOOejFJG. 1 iJJustrates a communication system capab}e of operating in accordance with various embodiments of the invention;
[1007]FIG. 2 illustrates a receiver block diagram in a communication system receiver for minimizing a combined local and global mean square error for a signal equalization; and

[1008JFIG. 3 illustrates a flow chart for minimizing the combined local and global mean square error for a signal equalization.
Detailed Description of the Preferred Embodiment{s) [IG09] Various aspects of the invention may be incorporated in a system for wireless communications in accordance with the code division multiple access (CDMA) technique. Various CDMA communication techniques have been disciosed and descritied in various standards published by the Telecommunication Industry Association (TIA). Such standards include the TIA/EIA-95 standard, TlA/ElA-l3-2000 standard, lMT-2000 standard, and WCDMA standard, all incorporated by reference herein. In addition, the specification defined as 'TIA/EiA/lS-856 cdma2000 High Rate Packet Data Air interface Specification," incorporated by reference herein, also provides for a system wherein one or more aspects of the invention may be incorporated. A copy of the standards may be obtained by accessing the world wide web at the address: http-.//www.cdq.orq. or by writing to TIA, Standards and Technology Department, 2500 Wilson Boulevard, Arlington, VA 22201, United States of America. The specification generally identified as WCDMA standard, may be obtained by contacting 3GPP Support Office, 650 Route des Lucioles-Sophia Antipolis, Valbonne-France.
[lOlOJThis invention relates generally to a novel and improved method and apparatus for signal equalization in a communication system. One or more exemplary embodiments described herein are set forth in the context of a wireless data communication system. While use within this context is

advantageous, different embodiments of the invention may be incorporated in different environments or configurations. In general, the various systems described herein may be formed using software-controlled processors, integrated circuits, or discrete logic. The data, instructions, commands, information, signals, symbols, and chips that may be referenced throughout the application are advantageously represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or a combination thereof. In addition, the blocks shown in each block diagram may represent hardware or method steps.
[1011]F1G. 1 illustrates a general block diagram of a communication system 100 capable of operating in accordance with any of the code division multiple access (CDMA) communication system standards. Generally, communication system 100 includes a base station 101 that provides communication links between a number of mobile stations, such as mobile stations 102-104, and between the mobile stations 102-104 and a wireline network 105. Base station 101 may include a number of components, such as a mobile station controller, a base station controller, and a radio frequency transceiver. For simplicity, such components are not shown. Base station 101 may also be in communication with other base stations (not shown). Base station 101 communicates with each mobile station 102-104 via a fonward link. The fonward link may be maintained by a fonward link signal transmitted from base station 101. The fonward link signals targeted for several mobile stations 102-104 may be summed to form a fonward link signal 106. Each of the mobile stations 102-104 receiving fonward link signal 106 decodes the forward link signal 106 to extract the information ttial is targeted

for its user. At the receiving end, the receiver may treat as interference the portion of the received fonward link signal 106 targeted for others.
[1012]fi^obile stations 102-104 communicate with base station 101 via a corresponding reverse link. Each reverse link is maintained by a reverse link signal, such as reverse link signals 107-109 for respectively mobile stations 102-104. Base station 101 may also transmit a predefined series of data bits on a pilot channel via the forward link to all mobile stations to assist eacf) mobile sfatJon in decoding the fonvard link signal 106. Each of the mobile stations 102-104 may transmit a pilot channel to base station 101. The pilot channel transmitted from a mobile station may be used for decoding the information carried by the reverse link signal transmitted from the same mobile station. The use and operation of a pilot channel are well known. A transmitter and a receiver for communicating via the fon/vard and reverse links are included in each mobile station 102-104, and base station 101.
[1013]A block diagram of a receiver 400 is shown in FIG. 2. Receiver
400 may have several antennas 292-1 to 292-K for receiving the transmitted signal waveform. The signals received at antennas 292-1 to 292-K may be processed in corresponding pre-processing blocks 299-1 to 299-K to produce corresponding signals 298-1 to 298-K. The pre-processing blocks 299-1 to 299-K may include several operations not shown, such as RF/IF downconvertors, AGC {automatic gain control) compensation, A/D (analog-to-digital) conversion. The signals 298-1 to 298-K pass through an equalizer
401 to present a signal 499 for the decoder. The signals received at antennas 292-1 to 292-K originate from a common source and carry the same stream of

data symbols y[n}, where "n" represents the temporal index of the symbols in the received data stream.
t1014]tn communications system 100, the stream of data symbols yfn} may be transmitted from any of the mobile stations 102-104 through a communication channel to receiver 400 in base station 101, or from a base station 101 to any of the mobile stations 102-104. Receiver 400 may be incorporated in base station 101 for receiving signals from a mobile station over a dispersive channsJ, or in a mobile station 102-104 for receiving signals from base station 101 over a dispersive channel. Equalizer 401 may include a number of finite impulse response (FIR) filters 470-1 to 470-K. Although several filters 470-1 to 470-K are shown in FIG. 2, the implementation of the filters may be different in various embodiments. In one case, one filter may be used repeatedly to process aii the signals 296-1 to 296-K. In another case, a filter may be dedicated to each signal 298-1 to 298-K from the antennas 292-1 to 292-K. The equalizer for the path from the mth antenna may be a tapped delay line FIR filter with temporal coefficients Cmfn}. Use and operation of FIR filters are well known in the art.
[1015]The output of each of the filters 470-1 to 470-K represents an estimate of a transmitted data symbol in the data stream y[n]. The output of

where the FIR filter 470-1 has 2M+1 taps given by [Cj^fn] : ^=-M, ..., M\, ' denotes complex conjugation, and {Xt[n,k] :k= -M, .... /W} denotes the tapped delay-line contents at time n. The outputs of filters 470-1 to 470-K are scaled by tt>e multipliers 480-1 to 4ao-K each of which has an associated spatial coefficient Sm/n/. After the scaling operation, the resulting signals are summed in a combiner 490 to fomi a combined signal 499 which represents a

{Cj'ln]: k=-M. ..., M} and the spatial coefficients Smln], for each m, can be optimized in accordance with an embodiment. The signal 499 would then carry an estimate of the transmitted data symbols that could be decoded with improved reliability. The temporal coefficients Cmlnj and spatial combiner weights Sr^n], for m=:l,...,K, may be optimized using the Minimum Mean Square Error (MMSE) criterion in several possible ways. One method, called Local Optimization, optimizes the temporal coefficients Cmlr>] for the m-th antenna based solely on minimizing the MSE between the transmitted symbol y{n} and the local estimate of the transmitted symbol y„[n], i.e., the FIR
output signal 470-m for the m-th antenna branch. The temporal coefficients Cn^n]are selected to minimize the Locay WSH defined as:

After the temporal coefficients Cm[n} for each antenna branch are determined, the spatial combiner weights S^^n} are chosen to minimize the mean square error (MSE) in the combined output signal >[«].
[1017]Another method, called Global Optimization, optimizes the temporal coefficients Ca,[n} and spatial combiner weights Stn[n] for all antennas jointly, using the combined output signal y[n]. For Global Optimization, the temporal coefficients and combiner weights are selected

[1019]These respective optimizations may be carried out using adaptive signal processing algorithms that are well known in the art, e.g., the Least Mean Square (LMS) algorithm and its variants. When such an adaptive algorithm is used for optimizing the temporal coefficients Cm/h/and spatial coefficients Sm[n], the number of samples (i.e. the amount of training time) required for the coefficients to converge to their steady-stale {i.e., MMSE-optimal) values is greater for Global Optimization than for Local Optimization. However, the steady-state MSE is generally lower for Global Optimization. The present embodiment, called Combined Global-Local Optimization, improves on both these approaches to achieve a balance between low steady stgte MSE and fast convergence time.

When a is set equal to zero, minimizing the Combined MSB amounts to Global Optimization, whereas if a is set equal to zero, minimizing the combined MSE amounts to Local Optimization. In the embodiment, the value for a may be any number between zero and one (0 t1021]Jn accordance with an embodiment, once a particular value of a has been selected, one can choose step-size parameters Ac and a^ and update the temporal coefficients Cm[n] and spatial coefficients Sn^n} in an iterative fashion. For example, the temporal and spatial coefficients

where k indexes the coefficients in the FIR filter of 470-1, Ac is the step-size parameter for the temporal coefficients and Ci[n+i] denotes the updated

temporal coefficients at time n+1. Next, for a fixed set of temporal

wfiers zls Is tfie step-size parameter for the spatial coefficients and St[n] denotes ttie updated spatial coefficients at time n+1. The temporai coefficients CmfnJ and spatial coefflcienis Sn^nJ for the other antenna branches are updated analogously. The step-size parameters Ac and As can be any values which guarantee convergence of the iterative updates. Methods for selecting step-size parameters meeting these requirements are well known in the art. Furthermore, it follows by methods well known in the art that these nested iterations converge to a solution which achieves the CombinedMSE.
[1022]FiG. 3 shows a flow chart 600 depicting one or more steps necessary to perfomn a combined optimization of the temporal coefficients Cm[n] and spatial coefficients Sm[n]. Various steps of the flow chart 600 may be performed by a control system. At step 601, the temporal coefficients Cm[n] and spatial coefficients Sn4n] are initialized and the initial values of the parameters ct, Ac and As are selected. At step 602, an estimate yjn] of the
transmitted symbol is generated for the m-th antenna branch using Xm[n}, the data stream received on antenna m, and the temporal coefficients Cm[n]. At step 603, the estimates on each of the antenna branches are combined, using the spatial combiner coefficients Sm[n], to generate a combined estimate y[n} of the data symbol. The combined estimatB may be passed at step 604 to a decoder and may be evaluated in step 605 to determine whether

additional updates of the temporal and spatial coefficients is required. Additional updates may not be necessary when the MSE error is at an acceptably small level. At step 606, the counter is incremented for the next data symbol and the process proceeds to step 602. At step 607 and 608, the values of the temporal coefficients Cm[n] and spatial coefficients S^n] are updated in accordance with the parameters a, Ac and As- At step 609 the parameters a, Ac and As may be adjusted, if desired, from the initial values set at step 601. For example, by adjusting a, the compromise between Local Optimization and Giobal Optimization can be controlled. When the value for a approaches zero, the updates are effectively those of Global Optimization rather than Local Optimization. Similarly, when the value for a approaches one, the updates are effectively those of Local Optimization rather than Global Optimization. This allows the possibility of trading off faster convergence for increased magnitude of the tJISE error, and vice-versa. Reducing the values for the step-size parameters Ac and As yields lower steady-state MSE at the expense of slower convoTgence of the iterations. Increasing the values for the step-size parameters Ac and As speeds up the convergence of the iterations but results in increased steady-state MSE. At step 610, the counter is incremented for the next pilot symbol. At step 611, the process deterrnines whether the last data symbol in the training-interval has been processed. If additional processing over the same stream of data is desired, the proceeds to step 602.
[1023]Those of skill in the art would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in

connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scc^e of the present invention.
[1024]The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed witti a general putpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device. discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
t1025]The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a

software module executed by a processor, or in a combination. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write Information to, the storage medium. In the alternative, the storage medium may be Integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
[1026]The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. The 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 the use of the inventive faculty. 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:

WE CLAIM
1. A method for combined spatial and temporal signal equalization in a
communication system with multiple receiver antennas comprising:
receiving a plurality of signals from a common source,
wherein said plurality of signals carries a common
stream of data symbols;
combining a local MSE and a global MSE in accordance with a weighting
factor to produce said combined local and global MSE; and
minimizing said combined local and global mean square error (MSE) over said
received signals.
2. The method as claimed in claim 1, wherein said weighting factor has a value between zero and one.
3. The method as claimed in claim 1, comprising:
determining temporal and spatial coefficients for said combined global and local MSE based on said weighting factor.
4. The method as claimed in claim 3, comprising;
adjusting said temporal coefficients in accordance with a temporal coefficient step size for said minimizing of combined local and global MSE.
5. The method as claimed in claim 4, comprising:
adjusting said temporal coefficient step size for said minimizing of combined local and global MSE.
6. The method as claimed in claim 3, comprising;
adjusting said spatial coefficients in accordance with a spatial coefficient step size for said minimizing of combined local and global MSE.

7. The method as claimed in claim 6, comprising:
adjusting said spatial coefficient step size for said minimizing said combined local and global MSE.
8. The method as claimed m claim 1, comprising:
adjusting said weighting factor to achieve a corresponding effect of at least one of processing speed and error magnitude in said minimizing said combined local and global MSE.
9. The method as claimed in claim 1, comprising:
producing a combined signal after said minimizing said combined local and global MSE over said received signals.
10. The method as claimed 1, in claim further comprising:
decoding said combined signal to retrieve said common stream of data
symbols.
U. The method as claimed in claim 1, comprising:
combining local and global MSE in accordance with a
CombinedMSE=a(E(y[n]-yi[n]f+ E|y[n]-y2[n]|'+...+ Eiy[n]-yK[n]p}+(I+ a)
{E|y[n]-y[n])^}
wherein a is a weighting factor.
12. An apparatus for combined spatial and temporal signal equalization in a communication system with multiple receiver antennas comprising:
a receiver for receiving a plurality of signals from a common source, wherein said plurality of signals carries a common stream of data symbols;
a processor for combining a local MSE and a global MSE in accordance with a weighting factor to produce said combined local and global MSE minimization; and
an equalizer for minimizing said combined local and global mean square error (MSE) over said received signals.

13. The apparatus as claimed in claim 12, wherein said weighting factor has a
value between zero and one.
14. The apparatus as claimed in claim 12, comprising:
a decoder for decoding said combined signal to retrieve said common stream of data symbols.
15. The apparatus as claimed in claim 12, comprising a plurality of antennas
coupled to said receiver for correspondingly receiving said plurality of signals.
16. The apparatus as claimed in claim 12, configured to perform the method
claimed in any one of the claims 1-11.

Documents:

0153-chenp-2004 abstract.jpg

0153-chenp-2004 abstract.pdf

0153-chenp-2004 claims-duplicate.pdf

0153-chenp-2004 claims.pdf

0153-chenp-2004 correspondence-others.pdf

0153-chenp-2004 correspondence-po.pdf

0153-chenp-2004 description (complete)-duplicate.pdf

0153-chenp-2004 description (complete).pdf

0153-chenp-2004 drawings-duplicate.pdf

0153-chenp-2004 drawings.pdf

0153-chenp-2004 form-1.pdf

0153-chenp-2004 form-13.pdf

0153-chenp-2004 form-18.pdf

0153-chenp-2004 form-26.pdf

0153-chenp-2004 form-3.pdf

0153-chenp-2004 form-5.pdf

0153-chenp-2004 petition.pdf

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Patent Number

229667

Indian Patent Application Number

153/CHENP/2004

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

19-Feb-2009

Date of Filing

27-Jan-2004

Name of Patentee

QUALCOMM INCORPORATED

Applicant Address

5775 MOREHOUSE DRIVE, SAN DIEGO, CALIFORNIA 92121,

Inventors:

#	Inventor's Name	Inventor's Address
1	CORBATON, IVAN JESUS FERNANDEZ	1134 FELSPAR STREET, #2, SAN DIEGO, CALIFORNIA 92109,
2	SMEE, JOHN, E	5220 FIORE TERRACE #M212, SAN DIEGO, CALIFORNIA 92122,
3	JAYARAMAN, SRIKANT	1254 PACIFIC BEACH DRIVE, #1, SAN DIEGO, CALIFORNIA 92109,

PCT International Classification Number

HO4L25/03

PCT International Application Number

PCT/US02/23911

PCT International Filing date

2002-07-25

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	09/918,770	2001-07-27	U.S.A.