(12)
`
`United States Patent
`Walton et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,785,341 B2
`*Aug. 31, 2004
`
`US006785341B2
`
`(54) METHOD AND APPARATUS FOR
`PROCESSING DATA IN A MULTIPLE-INPUT
`MULTIPLE-OUTPUT (MIMO)
`COMMUNICATION SYSTEM UTILIZING
`CHANNEL STATE INFORMATION
`
`(75) Inventors: Jay R- Walton, Westford, MA (Us);
`Mark Wallace, Bedford, MA (US);
`John W- Ketchum> Harvard> MA (Us);
`Steven J- H0Ward> A5h1and> MA (Us)
`_
`_
`_
`(73) Asslgnee' (clgallcjosmm Incorporated’ San Dlego’
`(
`)
`.
`.
`.
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`% S C 154(k)) b 478 (12115
`'
`'
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`*
`
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`_
`) Nonce'
`
`(
`
`This patent is subject to a terminal dis-
`claimer.
`
`WO
`W0
`
`9809381
`98/30047
`
`3/1998
`7/1998
`
`OTHER PUBLICATIONS
`J ongren, et al. “Utilizing Quantized Feedback Information in
`Orthogonal Space—Time Block Coding” 2000 IEEE Global
`Telecommunications Conference 2: 995—999 (Nov. 27,
`2000)'
`John A.C. Bingham, “Multicarrier Modulation for Data
`Transmission: An Idea Whose Time Has Come,” IEEE
`Communications Magazine, May 1990 (pp. 5—13).
`B. Hassibi, et al. “High—Rate Codes that are Linear in Space
`and Time,” LUCENT Technologies, Murray Hill, NY
`(USA), Aug. 22, 2000, (pp. 1—54).
`P.W. Wolniansky, et al. “V—BLAST: An Architecture for
`Realizing Very High Data Rates Over the Rich—Scattering
`Wireless Channel,” LUCENT Technologies, Holmdel, NJ.
`
`* cited by examiner
`
`Primary Examiner—Temesghen Ghebretinsae
`(74) Attorney, Agent, or F irm—Philip Wadsworth; Thien T.
`Nguyen; Thomas R‘ Rouse
`(57)
`ABSTRACT
`
`_
`_
`_
`_
`Techniques to “successively” process received signals at a
`receiver unit in a MIMO system to recover transmitted data,
`and to “adaptively” process data at a transmitter unit based
`on channel state information available for the MIMO chan
`
`_
`(21) Appl. No.. 09/854,235
`(22) Filed:
`May 11, 2001
`
`(65)
`
`Prior Publication Data
`
`US 2003/0035491 A1 Feb- 20, 2003
`7
`
`(
`
`)
`
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`
`'
`
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`
`' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
`
`""
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`’
`
`nel. Asuccessive cancellation receiver processing technique
`
`Fleld Of Search ............................... ..
`375/144’ 148’ 346’ 347
`
`(56)
`
`,
`References Clted
`U_S_ PATENT DOCUMENTS
`
`55
`5,471,647 A 11/1995 Gerlach ‘T’t a1‘ 1
`2
`greenstfeni ettai """"" " 4 /69
`6’473’467 B1 * 10/2002 “zilsjceeneltrai a '
`375/267
`’
`’
`i
`iiiiiiiiiii "
`FOREIGN PATENT DOCUMENTS
`0951091
`10/1999
`0951091 A2 10/1999
`96/22662
`7/1996
`
`EP
`EP
`WO
`
`is used to process the received Signals and performs a
`number of iterations to provide decoded data streams. For
`each iteration, input (e.g., received) signals for the iteration
`are processed to provide one or more symbol streams. One
`of the symbol streams is selected and processed to provide
`a decoded data stream. The interference due to the decoded
`data stream is approximately removed (i.e., canceled) from
`the input signals provided to the next iteration. The channel
`characteristics are estimated and reported back to the trans
`mitter system and used to adjust (i.e., adapt) the processing
`(e.g., coding, modulation, and so on) of data prior to
`transmlsslon'
`
`57 Claims, 10 Drawing Sheets
`
`mi
`
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`DATA
`SOURCE
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`r114
`TXDATA
`PROCESSOR
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`124A
`152A
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`(156
`122A\ H (154A
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`TX MIMO —' MOD
`DEMOD —> RXMIMO _. DATA
`PROCESSOR
`DEMOD
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`PROCESSOR
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`RX DATA
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`\132
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`DEMOD
`MOD 1— PROCESSOR
`
`\154R
`
`\162
`
`SONY EX. 1008
`Page 1
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`

`
`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 1 of 10
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`US 6,785,341 B2
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`

`
`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 4 0f 10
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`US 6,785,341 B2
`
`PERFORM LINEAR OR NON-LINEAR
`EQUALIZATION ON THE NR
`RECEIVED SIGNALS
`
`l
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`DETERMINE SNR FOR
`TRANSMTITED SIGNALS
`INCLUDED IN RECEIVED SIGNALS
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`RECOVER (DEMODULATE AND
`DECODE) A SELECTED TRANSMI'ITED
`(E.G., ONE WITH BEST SNR)
`
`TRANSMI'ITED SIGNALS
`RECOVERED ?
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`(420
`FORM ESTIMATE OF INTERFERENCE
`PRESENTED BY RECOVERED
`TRANSMITTED SIGNAL ON EACH
`OF THE RECEIVED SIGNALS
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`l
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`CANCEL INTERFERENCE DUE
`TO RECOVERED TRANSMI'I'I'ED
`SIGNAL FROM EACH RECEIVED
`SIGNAL TO DERIVE INPUT
`SIGNAL FOR THE NEXT ITERATION
`
`FIG. 4
`
`(END)
`
`SONY EX. 1008
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`

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`U.S. Patent
`
`Aug. 31, 2004
`
`Sheet 5 0f 10
`
`US 6,785,341 B2
`
`150A
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`FIG. 5
`
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`

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`U.S. Patent
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`Aug. 31, 2004
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`Aug. 31, 2004
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`US 6,785,341 B2
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`Aug. 31, 2004
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`

`
`US 6,785,341 B2
`
`1
`METHOD AND APPARATUS FOR
`PROCESSING DATA IN A MULTIPLE-INPUT
`MULTIPLE-OUTPUT (MIMO)
`COMMUNICATION SYSTEM UTILIZING
`CHANNEL STATE INFORMATION
`
`BACKGROUND
`
`1. Field
`The present invention relates generally to data
`communication, and more speci?cally to a novel and
`improved method and apparatus for processing data in a
`multiple-input multiple-output (MIMO) communication
`system utilizing channel state information to provide
`improved system performance.
`2. Background
`Wireless communication systems are Widely deployed to
`provide various types of communication such as voice, data,
`and so on. These systems may be based on code division
`multiple access (CDMA), time division multiple access
`(TDMA), orthogonal frequency division multiplex
`(OFDM), or some other multiplexing techniques. OFDM
`systems may provide high performance for some channel
`environments.
`In a terrestrial communication system (e.g., a cellular
`system, a broadcast system, a multi-channel multi-point
`distribution system (MMDS), and others), an RF modulated
`signal from a transmitter unit may reach a receiver unit via
`a number of transmission paths. The characteristics of the
`transmission paths typically vary over time due to a number
`of factors such as fading and multipath.
`To provide diversity against deleterious path effects and
`improve performance, multiple transmit and receive anten
`nas may be used for data transmission. If the transmission
`paths betWeen the transmit and receive antennas are linearly
`independent (i.e., a transmission on one path is not formed
`as a linear combination of the transmissions on other paths),
`Which is generally true to at least an extent, then the
`likelihood of correctly receiving a data transmission
`increases as the number of antennas increases. Generally,
`diversity increases and performance improves as the number
`of transmit and receive antennas increases.
`A multiple-input multiple-output (MIMO) communica
`tion system employs multiple (NT) transmit antennas and
`multiple (NR) receive antennas for data transmission. A
`MIMO channel formed by the NT transmit and NR receive
`antennas may be decomposed into NC independent channels,
`With NC§min{NT, NR}. Each of the NC independent chan
`nels is also referred to as a spatial subchannel of the MIMO
`channel and corresponds to a dimension. The MIMO system
`can provide improved performance (e.g., increased trans
`mission capacity) if the additional dimensionalities created
`by the multiple transmit and receive antennas are utiliZed.
`There is therefore a need in the art for techniques to
`process a data transmission at both the transmitter and
`receiver units to take advantage of the additional dimen
`sionalities created by a MIMO system to provide improved
`system performance.
`
`10
`
`15
`
`25
`
`35
`
`40
`
`45
`
`55
`
`2
`for data transmission. In an aspect, a “successive cancella
`tion” receiver processing technique (described beloW) is
`used to process the received signals. In another aspect, the
`channel characteristics are estimated and reported back to
`the transmitter system and used to adjust (i.e., adapt) the
`processing (e.g., coding, modulation, and so on) of data prior
`to transmission. Using a combination of the successive
`cancellation receiver processing technique and adaptive
`transmitter processing technique, high performance may be
`achieved for the MIMO system.
`A speci?c embodiment of the invention provides a
`method for sending data from a transmitter unit to a receiver
`unit in a MIMO communication system. In accordance With
`the method, at the receiver unit, a number of signals are
`initially received via a number of receive antennas, With
`each received signal comprising a combination of one or
`more signals transmitted from the transmitter unit. The
`received signals are processed in accordance With a succes
`sive cancellation receiver processing technique to provide a
`number of decoded data streams, Which are estimates of the
`data streams transmitted from the transmitter unit. Channel
`state information (CSI) indicative of characteristics of a
`MIMO channel used to transmit the data steams are also
`determined and transmitted back to the transmitter unit. At
`the transmitter unit, each data stream is adaptively processed
`prior to transmission over the MIMO channel in accordance
`With the received CS1.
`The successive cancellation receiver processing scheme
`typically performs a number of iterations to provide the
`decoded data streams, one iteration for each decoded data
`stream. For each iteration, a number of input signals for the
`iteration are processed in accordance With a particular linear
`or non-linear processing scheme to provide one or more
`symbol streams. One of the symbol streams is then selected
`and processed to provide a decoded data stream. A number
`of modi?ed signals are also derived based on the input
`signals, With the modi?ed signals having components due to
`the decoded data stream approximately removed (i.e.,
`canceled). The input signals for a ?rst iteration are the
`received signals and the input signals for each subsequent
`iteration are the modi?ed signals from a preceding iteration.
`Various linear and non-linear processing schemes may be
`used to process the input signals. For a non-dispersive
`channel (i.e., With ?at fading), a channel correlation matrix
`inversion (CCMI) technique, a minimum mean square error
`(MMSE) technique, or some other techniques may be used.
`And for a time-dispersive channel (i.e., With frequency
`selective fading), an MMSE linear equaliZer (MMSE-LE), a
`decision feedback equaliZer (DFE), a maximum-likelihood
`sequence estimator (MLSE), or some other techniques may
`be used.
`The available CSI may include, for example, the signal
`to-noise-plus-interference (SNR) of each transmission chan
`nel to be used for data transmission. At the transmitter unit,
`the data for each transmission channel may be coded based
`on the CSI associated With that channel, and the coded data
`for each transmission channel may further be modulated in
`accordance With a modulation scheme selected based on the
`CS1.
`The invention further provides methods, systems, and
`apparatus that implement various aspects, embodiments, and
`features of the invention, as described in further detail
`beloW.
`
`SUMMARY
`Aspects of the invention provide techniques to process the
`received signals at a receiver unit in a multiple-input
`multiple-output (MIMO) system to recover the transmitted
`data, and to adjust the data processing at a transmitter unit
`based on estimated characteristics of a MIMO channel used
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The features, nature, and advantages of the present inven
`tion Will become more apparent from the detailed descrip
`
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`US 6,785,341 B2
`
`3
`tion set forth below When taken in conjunction With the
`drawings in Which like reference characters identify corre
`spondingly throughout and Wherein:
`FIG. 1 is a diagram of a multiple-input multiple-output
`(MIMO) communication system capable of implementing
`various aspects and embodiments of the invention;
`FIG. 2 is a block diagram of an embodiment of a MIMO
`transmitter system capable of processing data for transmis
`sion based on the available CSI;
`FIG. 3 is a block diagram of an embodiment of a MIMO
`transmitter system Which utiliZes orthogonal frequency divi
`sion modulation (OFDM);
`FIG. 4 is a How diagram illustrating a successive cancel
`lation receiver processing technique to process NR received
`signals to recover NT transmitted signals;
`FIG. 5 is a block diagram of a receiver system capable of
`implementing various aspects and embodiments of the
`invention;
`FIGS. 6A, 6B, and 6C are block diagrams of three channel
`MIMO/data processors, Which are capable of implementing
`a CCMI technique, a MMSE technique, and a DFE
`technique, respectively;
`FIG. 7 is a block diagram of an embodiment of a receive
`(RX) data processor;
`FIG. 8 is a block diagram of an interference canceller; and
`FIGS. 9A, 9B, and 9C are plots that illustrate the perfor
`mance for various receiver and transmitter processing
`schemes.
`
`DETAILED DESCRIPTION
`
`FIG. 1 is a diagram of a multiple-input multiple-output
`(MIMO) communication system 100 capable of implement
`ing various aspects and embodiments of the invention.
`System 100 includes a ?rst system 110 in communication
`With a second system 150. System 100 can be operated to
`employ a combination of antenna, frequency, and temporal
`diversity (described beloW) to increase spectral ef?ciency,
`improve performance, and enhance ?exibility. In an aspect,
`system 150 can be operated to determine the characteristics
`of a MIMO channel and to report channel state information
`(CSI) indicative of the channel characteristics that have been
`determined in this Way back to system 110, and system 110
`can be operated to adjust the processing (e.g., encoding and
`modulation) of data prior to transmission based on the
`available CSI. In another aspect, system 150 can be operated
`to process the data transmission from system 110 in a
`manner to provide high performance, as described in further
`detail beloW.
`At system 110, a data source 112 provides data (i.e.,
`information bits) to a transmit (TX) data processor 114,
`Which encodes the data in accordance With a particular
`encoding scheme, interleaves (i.e., reorders) the encoded
`data based on a particular interleaving scheme, and maps the
`interleaved bits into modulation symbols for one or more
`transmission channels used for transmitting the data. The
`encoding increases the reliability of the data transmission.
`The interleaving provides time diversity for the coded bits,
`permits the data to be transmitted based on an average
`signal-to-noise-plus-interference-ratio (SNR) for the trans
`mission channels used for the data transmission, combats
`fading, and further removes correlation betWeen coded bits
`used to form each modulation symbol. The interleaving may
`further provide frequency diversity if the coded bits are
`transmitted over multiple frequency subchannels. In an
`aspect, the encoding, interleaving, and symbol mapping (or
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`a combination thereof) are performed based on the CSI
`available to system 110, as indicated in FIG. 1.
`The encoding, interleaving, and symbol mapping at trans
`mitter system 110 can be performed based on numerous
`schemes. One speci?c scheme is described in US. patent
`application Ser. No. 09/776,073, entitled “CODING
`SCHEME FOR A WIRELESS COMMUNICATION
`SYSTEM,” ?led Feb. 1, 2001, assigned to the assignee of
`the present application and incorporated herein by reference.
`Another scheme is described in further detail beloW.
`MIMO system 100 employs multiple antennas at both the
`transmit and receive ends of the communication link. These
`transmit and receive antennas may be used to provide
`various forms of spatial diversity (i.e., antenna diversity),
`including transmit diversity and receive diversity. Spatial
`diversity is characteriZed by the use of multiple transmit
`antennas and one or more receive antennas. Transmit diver
`sity is characteriZed by the transmission of data over mul
`tiple transmit antennas. Typically, additional processing is
`performed on the data transmitted from the transmit anten
`nas to achieved the desired diversity. For example, the data
`transmitted from different transmit antennas may be delayed
`or reordered in time, coded and interleaved across the
`available transmit antennas, and so on. Receive diversity is
`characteriZed by the reception of the transmitted signals on
`multiple receive antennas, and diversity is achieved by
`simply receiving the signals via different signal paths.
`System 100 may be operated in a number of different
`communication modes, With each communication mode
`employing antenna, frequency, or temporal diversity, or a
`combination thereof. The communication modes may
`include, for example, a “diversity” communication mode
`and a “MIMO” communication mode. The diversity com
`munication mode employs diversity to improve the reliabil
`ity of the communication link. In a common application of
`the diversity communication mode, Which is also referred to
`as a “pure” diversity communication mode, data is trans
`mitted from all available transmit antennas to a recipient
`receiver system. The pure diversity communications mode
`may be used in instances Where the data rate requirements
`are loW or When the SNR is loW, or When both are true. The
`MIMO communication mode employs antenna diversity at
`both ends of the communication link (i.e., multiple transmit
`antennas and multiple receive antennas) and is generally
`used to both improve the reliability and increase the capacity
`of the communication link. The MIMO communication
`mode may further employ frequency and/or temporal diver
`sity in combination With the antenna diversity.
`System 100 may utiliZe orthogonal frequency division
`modulation (OFDM), Which effectively partitions the oper
`ating frequency band into a number of (NL) frequency
`subchannels (i.e., frequency bins). At each time slot (i.e., a
`particular time interval that may be dependent on the band
`Width of the frequency subchannel), a modulation symbol
`may be transmitted on each of the NL frequency subchan
`nels.
`System 100 may be operated to transmit data via a number
`of transmission channels. As noted above, a MIMO channel
`may be decomposed into NC independent channels, With
`Ncé min {Np NR}. Each of the NC independent channels is
`also referred to as a spatial subchannel of the MIMO
`channel. For a MIMO system not utiliZing OFDM, there is
`typically only one frequency subchannel and each spatial
`subchannel may be referred to as a “transmission channel”.
`For a MIMO system utiliZing OFDM, each spatial subchan
`nel of each frequency subchannel may be referred to as a
`transmission channel.
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`US 6,785,341 B2
`
`5
`A MIMO system can provide improved performance if
`the additional dimensionalities created by the multiple trans
`mit and receive antennas are utiliZed. While this does not
`necessarily require knowledge of CSI at the transmitter,
`increased system ef?ciency and performance are possible
`When the transmitter is equipped With CSI, Which is descrip
`tive of the transmission characteristics from the transmit
`antennas to the receive antennas. The processing of data at
`the transmitter prior to transmission is dependent on Whether
`or not CSI is available.
`The available CSI may comprise, for example, the signal
`to-noise-plus-interference-ratio (SNR) of each transmission
`channel (i.e., the SNR for each spatial subchannel for a
`MIMO system Without OFDM, or the SNR for each spatial
`subchannel of each frequency subchannel for a MIMO
`system With OFDM). In this case, data may be adaptively
`processed at the transmitter (e.g., by selecting the proper
`coding and modulation scheme) for each transmission chan
`nel based on the channel’s SNR.
`For a MIMO system not employing OFDM, TX MIMO
`processor 120 receives and demultiplexes the modulation
`symbols from TX data processor 114 and provides a stream
`of modulation symbols for each transmit antenna, one
`modulation symbol per time slot. And for a MIMO system
`employing OFDM, TX MIMO processor 120 provides a
`stream of modulation symbol vectors for each transmit
`antenna, With each vector including NL modulation symbols
`for the NL frequency subchannels for a given time slot. Each
`stream of modulation symbols or modulation symbol vec
`tors is received and modulated by a respective modulator
`(MOD) 122, and transmitted via an associated antenna 124.
`At receiver system 150, a number of receive antennas 152
`receive the transmitted signals and provide the received
`signals to respective demodulators (DEMOD) 154. Each
`demodulator 154 performs processing complementary to
`that performed at modulator 122. The modulation symbols
`from all demodulators 154 are provided to a receive (RX)
`MIMO/data processor 156 and processed to recover the
`transmitted data streams. RX MIMO/data processor 156
`performs processing complementary to that performed by
`TX data processor 114 and TX MIMO processor 120 and
`provides decoded data to a data sink 160. The processing by
`receiver system 150 is described in further detail beloW.
`The spatial subchannels of a MIMO system (or more
`generally, the transmission channels in a MIMO system With
`or Without OFDM) typically experience different link con
`ditions (e.g., different fading and multipath effects) and may
`achieve different SNR. Consequently, the capacity of the
`transmission channels may be different from channel to
`channel. This capacity may be quanti?ed by the information
`bit rate (i.e., the number of information bits per modulation
`symbol) that may be transmitted on each transmission
`channel for a particular level of performance (e.g., a par
`ticular bit error rate (BER) or packet error rate (PER)).
`Moreover, the link conditions typically vary With time. As a
`result, the supported information bit rates for the transmis
`sion channels also vary With time. To more fully utiliZe the
`capacity of the transmission channels, CSI descriptive of the
`link conditions may be determined (typically at the receiver
`unit) and provided to the transmitter unit so that the pro
`cessing can be adjusted (or adapted) accordingly. The CSI
`may comprise any type of information that is indicative of
`the characteristics of the communication link and may be
`reported via various mechanisms, as described in further
`detail beloW. For simplicity, various aspects and embodi
`ments of the invention are described beloW Wherein the CSI
`comprises SNR. Techniques to determine and utiliZe CSI to
`provide improved system performance are described below.
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`MIMO Transmitter System With CSI Processing
`FIG. 2 is a block diagram of an embodiment of a MIMO
`transmitter system 110a, Which does not utiliZe OFDM but
`is capable of adjusting its processing based on CSI available
`to the transmitter system (e.g., as reported by receiver
`system 150). Transmitter system 110a is one embodiment of
`the transmitter portion of system 110 in FIG. 1. System 110a
`includes (1) a TX data processor 114a that receives and
`processes information bits to provide modulation symbols
`and (2) a TX MIMO processor 120a that demultiplexes the
`modulation symbols for the NT transmit antennas.
`In the speci?c embodiment shoWn in FIG. 2, TX data
`processor 114a includes a demultiplexer 208 coupled to a
`number of channel data processors 210, one processor for
`each of the NC transmission channels. Demultiplexer 208
`receives and demultiplexes the aggregate information bits
`into a number of (up to NC) data streams, one data stream for
`each of the transmission channels to be used for data
`transmission. Each data stream is provided to a respective
`channel data processor 210.
`In the embodiment shoWn in FIG. 2, each channel data
`processor 210 includes an encoder 212, a channel interleaver
`214, and a symbol mapping element 216. Encoder 212
`receives and encodes the information bits in the received
`data stream in accordance With a particular encoding scheme
`to provide coded bits. Channel interleaver 214 interleaves
`the coded bits based on a particular interleaving scheme to
`provide diversity. And symbol mapping element 216 maps
`the interleaved bits into modulation symbols for the trans
`mission channel used for transmitting the data stream.
`Pilot data (e.g., data of knoWn pattern) may also be
`encoded and multiplexed With the processed information
`bits. The processed pilot data may be transmitted (e.g., in a
`time division multiplexed (TDM) manner) in all or a subset
`of the transmission channels used to transmit the informa
`tion bits. The pilot data may be used at the receiver to
`perform channel estimation, as described beloW.
`As shoWn in FIG. 2, the data encoding, interleaving, and
`modulation (or a combination thereof) may be adjusted
`based on the available CSI (e.g., as reported by receiver
`system 150). In one coding and modulation scheme, adap
`tive encoding is achieved by using a ?xed base code (e.g.,
`a rate 1/3 Turbo code) and adjusting the puncturing to
`achieve the desired code rate, as supported by the SNR of the
`transmission channel used to transmit the data. For this
`scheme, the puncturing may be performed after the channel
`interleaving. In another coding and modulation scheme,
`different coding schemes may be used based on the reported
`CSI. For example, each of the data streams may be coded
`With an independent code. With this scheme, a “successive
`cancellation” receiver processing scheme may be used to
`detect and decode the data streams to derive a more reliable
`estimate of the transmitted data streams, as described in
`further detail beloW.
`Symbol mapping element 216 can be designed to group
`sets of interleaved bits to form non-binary symbols, and to
`map each non-binary symbol into a point in a signal con
`stellation corresponding to a particular modulation scheme
`(e.g., QPSK, M-PSK, M-QAM, or some other scheme)
`selected for the transmission channel. Each mapped signal
`point corresponds to a modulation symbol.
`The number of information bits that may be transmitted
`for each modulation symbol for a particular level of perfor
`mance (e.g., one percent PER) is dependent on the SNR of
`the transmission channel. Thus, the coding and modulation
`scheme for each transmission channel may be selected based
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`US 6,785,341 B2
`
`7
`on the available CSI. The channel interleaving may also be
`adjusted based on the available CSI.
`Table 1 lists various combinations of coding rate and
`modulation scheme that may be used for a number of SNR
`ranges. The supported bit rate for each transmission channel
`may be achieved using any one of a number of possible
`combinations of coding rate and modulation scheme. For
`example, one information bit per modulation symbol may be
`achieved using (1) a coding rate of 1/2 and QPSK
`modulation, (2) a coding rate of 1/3 and 8-PSK modulation,
`10
`(3) a coding rate of 1/4 and 16-QAM, or some other
`combination of coding rate and modulation scheme. In Table
`1, QPSK, 16-QAM, and 64-QAM are used for the listed
`SNR ranges. Other modulation schemes such as S-PSK,
`32-QAM, 128-QAM, and so on, may also be used and are
`Within the scope of the invention.
`
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`
`TABLE 1
`
`SNR
`Range
`
`# of Information Modulation # of Coded
`Bits/Symbol
`Symbol
`Bits/Symbol
`
`Coding
`Rate
`
`1.5-4.4
`4.4-6.4
`6.4-8.35
`8.35-10.4
`10.4-12.3
`12.3-14.15
`14.15-15.55
`15.55-17.35
`>17.35
`
`1
`1.5
`2
`2.5
`3
`3.5
`4
`4.5
`5
`
`QPSK
`QPSK
`16-QAM
`16-QAM
`16-QAM
`64-QAM
`64-QAM
`64-QAM
`64-QAM
`
`2
`2
`4
`4
`4
`6
`6
`6
`6
`
`1/2
`3/4
`1/2
`5/8
`3/4
`7/12
`2/3
`3/4
`5/6
`
`The modulation symbols from TX data processor 114a are
`provided to a TX MIMO processor 120a, Which is one
`embodiment of TX MIMO processor 120 in FIG. 1. Within
`TX MIMO processor 120a, a demultipleXer 222 receives (up
`to) NC modulation symbol streams from NC channel data
`processors 210 and demultipleXes the received modulation
`symbols into a number of (NT) modulation symbol streams,
`one stream for each antenna used to transmit the modulation
`symbols. Each modulation symbol stream is provided to a
`respective modulator 122. Each modulator 122 converts the
`modulation symbols into an analog signal, and further
`ampli?es, ?lters, quadrature modulates, and upconverts the
`signal to generate a modulated signal suitable for transmis
`sion over the Wireless link.
`
`MIMO Transmitter System With OFDM
`FIG. 3 is a block diagram of an embodiment of a MIMO
`transmitter system 1106, Which utiliZes OFDM and is
`capable of adjusting its processing based on the available
`CSI. Within a TX data processor 114