US008971461B2
`
`a2) United States Patent
`US 8,971,461 B2
`(10) Patent No.:
`
` Sampathetal. (45) Date of Patent: *Mar. 3, 2015
`
`
`(54) CQIAND RANK PREDICTION FOR LIST
`SPHERE DECODING AND ML MIMO
`RECEIVERS
`
`USPC... 375/219, 221, 260, 262, 265, 267, 316,
`375/347, 227, 346; 455/24, 69, 513
`See application file for complete search history.
`
`(75)
`
`Inventors: Hemanth Sampath, San Diego, CA
`(US); Tamer Kadous, San Diego, CA
`(US)
`(73) Assignee: QUALCOMMIncorporated, San
`
`1ego,
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`USS.C. 154(b) by 1715 days.
`This patent is subject to a terminal dis-
`claimer.
`(21) Appl. No.: 11/441,652
`.
`Filed:
`
`(22)
`(65)
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`805748 BI
`5/2005. Berterdetal
`
`.
`(Continued)
`
`EP
`JP
`
`FOREIGN PATENT DOCUMENTS
`1566917 A2
`8/2005
`2007506307
`3/2007
`(Continued)
`OTHER PUBLICATIONS
`Gore et al. “Near-Optimal Selection of Transmit Antennas for a
`MIMO Channel Based on Shannon Capacity”, IEEE, Oct./Nov.
`2000."
`
`(Continued)
`
`Primary Examiner — Sophia Vlahos
`(74) Attorney, Agent, or Firm — Howard Seo
`
`May 25, 2006
`Prior Publication Data
`US 2007/0010957 Al
`Jan. 11, 2007
`Related U.S. Application Data
`(60) Provisional application No. 60/686,646, filed on Jun.
`1, 2005, provisional application No. 60/691,722, filed
`on Jun. 16, 2005.
`Int.Cl
`HOAL V/00
`HOAB 7/12
`
`(51)
`
`(2006.01)
`(2006.01)
`.
`,
`(Continued)
`
`ABSTRACT
`(57)
`Systems and methodologies are describedthatfacilitate inte-
`grating a list-sphere decoding design in a multiple input-
`multiple output (MIMO wireless communication environ-
`ment. According to various aspects, optimal rank selection
`and CQ] computation for an optimal rank can be performedin
`conjunction with a non-linear receiver, such as a maximum
`life (ML) MMSEreceiver, a non-linear receiver with a list-
`(52) US.CL
`CPC vieeececee HO4B 7/12 (2013.01); HO4B 1/1027._sphere decoder, andthe like. Optimal rank selection can be
`(2013.01); HO4B 7/0417 (2013.01); HO4B
`performed using a maximum rank selection protocol, a chan-
`7/063 (2013.01);
`nel capacity-based protocol, or any other suitable protocol
`that facilitates rank selection, and CQI information can be
`generated based in part on effective SNRs determined with
`regard to a selected optimal rank.
`
`(Continued)
`(58) Field of Classification Search
`CPC .... H04B 7/0602; H04B 7/0608; H04B 7/061;
`HO04B 7/0691; HO4L 2025/03426
`
`28 Claims, 13 Drawing Sheets
`
`ou
`902,
`
`— 904
`
`— 906
`
`— 908
`
`— 0
`
`— 912
`
`
` ————___________
`
` ¥ A
` ¥ R
`
`DD CAPACITIES
`
`EPEAT FOR ALL RANKS
`
`SELECT HIGHEST CAPACITY
`
`START
`¥
`GENERATE SUBMATRICES AND |“
`EVALUATE
`¥
`DETERMINESIC CAPACITY AND
`IDENTIFY OPTIMAL RANK
`
`Ad
`CAPACITY-MAP EFFECTIVE SNRs
`FOR EACH LAYER
`
`1
`
`APPLE 1007
`
`1
`
`APPLE 1007
`
`

`

`US 8,971,461 B2
`
`Page 2
`
`(51)
`
`(2006.01)
`(2006.01)
`(006.01)
`(2006.01)
`(2006.01)
`
`Int. Cl.
`HOdB 1/10
`HO4B 7/04
`MOAB 706
`HOAL 1/06
`HOAL 25/03
`5) US.Cl
`“oe
`(52)
`CPC we H04B 7/0632 (2013.01); HO4L 1/0026
`(2013.01); HO4E 1/0675 (2013.01); HO4L
`25/03242 (2013.01); HO4E 1/0656 (2013.01);
`HO4L 2025/03426 (2013.01)
`USPC oo. 375/346; 375/227; 375/260, 375/267;
`455/24; 455/513
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`. 455/562.1
`.....
`7/2005 Gore etal.
`6,917,820 B2*
`bebeseeeeees 375/267
`7,120,199 B2* 10/2006 Thieleckeetal.
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`10/2006 Tongetal.
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`11/2006 Thomasetal.
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`1/2008 Brunel
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`2/2008 Mukkavilli et al.
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`4/2008 Lakshmipathietal.
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`9/2008 Sampath etal.
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`4/2009 Yu etal.
`. 375/316
`8/2010 Deanetal. ..
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`. 714/759
`2002/0056066 Al*
`5/2002 Gesbert et al.
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`2002/0110138 Al*
`8/2002 Schramm ......... ee 370/430
`2003/0003863 Al
`1/2003 Thieleckeet al.
`2003/0068994 Al
`4/2003 Sayeedet al.
`2003/0157954 Al*
`8/2003 Medvedevetal. ............ 455/522
`2003/0235147 Al
`12/2003 Walton etal.
`2003/0236080 Al* 12/2003 Kadousetal. .......... 455/226.1
`2004/0058687 Al
`3/2004 Kim etal.
`2004/0186985 Al
`9/2004 Tran etal.
`2005/0008091 Al
`1/2005 Boutroset al.
`3/2005 Kadous
`2005/0063378 Al
`.......... 714/748
`8/2005 Ashikhmin et al.
`2005/0182994 Al*
`. 455/450
`2005/0227697 Al* 10/2005 Borstetal. .....
`
`2005/0237971 Al* 10/2005 Skraparlis .........0.0 370/329
`2006/0002414 Al
`1/2006 Duetal.
`2006/0023745 Al*
`2/2006 Kooetal. vce 370/468
`2012/0044982 Al
`2/2012 Sampath etal.
`
`JP
`KR
`WO
`
`FOREIGN PATENT DOCUMENTS
`2007507913
`3/2007
`1020050034476
`4/2005
`WO2004088508
`10/2004
`OTHER PUBLICATIONS
`
`Sandhuet al. “Near-Optimal Selection of Transmit Antennas for a
`MIMOChannel Based on Shannon Capacity”, IEEE, Oct./Nov. 2000
`and.*
`Heathetal. “Antenna Selection for Spatial Multiplexing System with
`Linear Receivers”, Apr. 2001, IEEE, pp. 142-144.*
`Gorokhovet al. “Transmit/Receive MIMOantennasubset selection”,
`May 2004, IEEE.*
`Galli “Non-linear MMSEestimation and SbS-MAPreceivers”, Jun.
`2000, IEEE.*
`Molischet al. “MIMOsystems with Antenna Selection”, IEEE, Mar.
`2004.*
`Tetsushiet al., “A Hybrid MIMO System Using Spatial Correlation”
`Oct. 2002 IEEE (whole document).
`Boutrous et al., “Soft-input soft-output lattice sphere decoder for
`linear channels” IEEE Dec. 2003 (whole document).
`International
`International Search Report—PCT/US06/21583,
`Search Authority—European Patent Office—Oct. 25, 2007.
`Complexity-reduced Maximum Likelihood Detection Based on Rep-
`lica Candidate Selection with QR Decomposition Using Pilot-As-
`sisted Channel Estimation and Ranking for MIMO Multiplexing
`Using OFCDM,Technical Report of IEICE, RCS2003-312, Mar.
`2004.
`Electronics Information and Communication Engineers General
`Convention in 2004, B-5-42.
`Gore, D. A., et al.: “Selecting an optimal set of transmit antennas for
`a low rank matrix channel,” 2000 IEEE International Conference on
`Acoustics, Speech, and Signal Processing. Proceedings. (ICASSP).
`Istanbul, Turkey, Jun. 5-9, 2000, New York, NY; IEEE,US, vol. 5 of
`6, (Jun. 5, 2000), pp. 2785-2788, XP001035763, abstract.
`Taiwan Search Report—Appl. No. 095119456, Jan. 8, 2010.
`Written Opinion—PCT/US06/021583, International Search Author-
`ity, European Patent Office, Oct. 25, 2007.
`Kaveic A., et al., “Equal-Diagonal QR Decomposition andits Appli-
`cation to Precoder Design for Successive-Cancellation Detection”,
`IEEETransactions on Information Theory, IEEE Press, USA,vol. 51,
`No. 1, Jan. 1, 2005, pp. 154-172, XP011124784, ISSN: 0018-9448,
`DOI: 10.1109/TIT.2004.842677.
`Kim et al. “Space-time Technique for wireless multiuser MIMO
`Systems with SIC Receivers”, Sep. 2004, IEEE, pp. 2013-2017.
`Supplementary European Search Report—EP06772044—Search
`Authority—The Hague—Oct. 15, 2012.
`
`* cited by examiner
`
`2
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 1 of 13
`
`US 8,971,461 B2
`
`
`
`wr
`So=
`
`3
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 2 of 13
`
`US 8,971,461 B2
`
`
`
`FIG.2
`
`4
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 3 of 13
`
`US 8,971,461 B2
`
`308
`
`Turbo
`Encoder
`
`306
`Rate
`Prediction
`
`
`
`M (2- bit)
`
`310
`
`
`SpatialMapping
`Demultiplexer
` bits
`
` CQI (5-bit)
`
`Decoder Decoder
` List Sphere
`Multiplexer
`
`(per tone)
`
`3 18
`
`bits
`
`322
`
` and
`
`
`
`Computation
`
`Rank
`
`FIG.3
`
`5
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 4 of 13
`
`US 8,971,461 B2
`
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`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 5 of 13
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`US 8,971,461 B2
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`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 6 of 13
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`US 8,971,461 B2
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`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 7 of 13
`
`US 8,971,461 B2
`
`700c
`
`702
`
`704
`
`706
`
`708
`
`710
`
`712
`
`GENERATE CHANNEL
`
`SUBMATRICES AND EVALUATE
`DECOMPOSITION(S)
`
`PERFORM QR MATRIX
`
`CALCULATE EFFECTIVE SNR
`
`SELECT OPTIMUM RANK
`
`QUANTIZECQI
`
`FEED BACK CQI AND RANK
`INFORMATION VIA REVERSE LINK
`
`CONTROL CHANNEL
`
`END
`
`FIG. 7
`
`9
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 8 of 13
`
`US 8,971,461 B2
`
`START
`
`800f
`
`
`
`
`
`CALCULATE SPECTRAL
`EFFICIENCIES
`
`802
`
`804
`
`806
`
`808
`
`AVERAGESPECTRAL EFFICIENCIES
`OVER ALL TONES
`
`CALCULATE CQI AND QUANTIZE
`
`
`
`FEED BACK CQI AND RANK USING
`REVERSE LINK CONTROL CHANNEL
`
`
`
`
`
`
`10
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 9 of 13
`
`US 8,971,461 B2
`
`900c
`
`902
`
`904
`
`906
`
`908
`
`910
`
`912
`
`GENERATE SUBMATRICES AND
`
`EVALUATE
`
`DETERMINESIC CAPACITY AND
`IDENTIFY OPTIMAL RANK
`
`
`
`
`
`
`SELECT HIGHEST CAPACITY
`
`CAPACITY-MAP EFFECTIVE SNRs
`FOR EACH LAYER
`
`ADD CAPACITIES
`
`REPEAT FOR ALL RANKS
`
`END
`
`11
`
`FIG. 9
`
`11
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 10 of 13
`
`US 8,971,461 B2
`
`1000 ™,
`
`USER DEVICE
`
`
`
`CAPACITY
`MAPPER
`
`RANK
`EVALUATOR
`
`TRANSMITTER |<
`
`MODULATOR
`
`PROCESSOR
`
`1016
`
`MEMORY
`
`FIG. 10
`
`12
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 11 of 13
`
`US 8,971,461 B2
`
`1100 o™“
`
`BASE STATION
`
`1110
`
`Rx ANTENNAS [«
`
`>|
`
`RECEIVER
`
`MEMORY
`
`1102
`
` 1106
`
`
`
`1108
`
`
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`
`
`
`
`1104
`
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`DEVICE(S)
`
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`
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`
`RANK
`
`MODULATOR
`
`1120
`
`FIG. 11
`
`13
`
`13
`
`

`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 12 of 13
`
`US 8,971,461 B2
`
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`

`U.S. Patent
`
`Mar.3, 2015
`
`Sheet 13 of 13
`
`US 8,971,461 B2
`
`J 1300
`
`1302
`
`1304
`
`1306
`
`1308
`
`1310
`
`1312
`
`LOGICAL MODULE FOR
`GENERATING AND EVALUATING
`CHANNEL
`
`SUBMATRICES
`
`LOGICAL MODULE FOR
`PERFORMING QR MATRIX
`DECOMPOSITION(S)
`
`LOGICAL MODULE FOR
`
`CALCULATING EFFECTIVE SNR
`CQI
`
`LOGICAL MODULE FOR SELECTING
`OPTIMUM RANK
`
`LOGICAL MODULEFOR QUANTIZING
`
`
`
`LOGICAL MODULE FOR FEEDING
`
`BACK CQI AND RANK INFORMATION
`
`
`VIA REVERSE LINK CONTROL
`
`CHANNEL
`
`FIG. 13
`
`15
`
`15
`
`

`

`US 8,971,461 B2
`
`1
`CQI AND RANK PREDICTION FOR LIST
`SPHERE DECODING AND ML MIMO
`RECEIVERS
`
`CLAIM OF PRIORITY UNDER 35 U.S.C. §119
`
`This application claims the benefit of U.S. Provisional
`Application Ser. No. 60/686,646 entitled “CQI AND RANK
`PREDICTION IN LIST SPHERE DECODING,”filed on
`Jun. 1, 2005, and U.S. Provisional Application Ser. No.
`60/691,722 entitled “A METHOD OF LIST SPHERE
`DECODING FOR MIMO RECEIVERS,”filed on Jun. 16,
`2005, both assigned to the assignee hereof and hereby
`expressly incorporated by reference herein.
`
`BACKGROUND
`
`I. Field
`The following description relates generally to wireless
`communications, and more particularly to performing rank
`calculation in a non-linear receiver employed in a wireless
`communication environment.
`II. Background
`Wireless communication systems have becomea prevalent
`means by which a majority of people worldwide has cometo
`communicate. Wireless communication devices have become
`
`smaller and more powerful in order to meet consumer needs
`and to improve portability and convenience. The increase in
`processing power in mobile devices such as cellular tele-
`phones has lead to an increase in demands on wireless net-
`worktransmission systems. Such systemstypically are not as
`easily updatedas the cellular devices that communicate there
`over. As mobile device capabilities expand,it can be difficult
`to maintain an older wireless network system in a mannerthat
`facilitates fully exploiting new and improvedwireless device
`capabilities.
`More particularly, frequency division based techniques
`typically separate the spectrum into distinct channels by split-
`ting it into uniform chunks of bandwidth, for example, divi-
`sion of the frequency band allocated for wireless communi-
`cation can be split into 30 channels, each of which can carry
`a voice conversationor, with digital service,carry digital data.
`Each channelcan be assignedto only one userat a time. One
`knownvariant is an orthogonal frequency division technique
`that effectively partitions the overall system bandwidth into
`multiple orthogonal subbands. These subbands are also
`referred to as tones, carriers, subcarriers, bins, and/or fre-
`quency channels. Each subbandis associated with a subcar-
`rier that can be modulated with data. With time division based
`
`techniques, a band is split time-wise into sequential time
`slices or time slots. Each user of a channel is provided with a
`time slice for transmitting and receiving information in a
`round-robin manner. For example, at any given time t, a user
`is provided access to the channel for a short burst. Then,
`access switches to another user who is provided with a short
`burst of time for transmitting and receiving information. The
`cycle of “taking turns” continues, and eventually each useris
`provided with multiple transmission and reception bursts.
`Code division based techniques typically transmit data
`over a numberoffrequencies available at any time in a range.
`In general, data is digitized and spread over available band-
`width, wherein multiple users can be overlaid on the channel
`and respective users can be assigned a unique sequence code.
`Users can transmit in the same wide-band chunk of spectrum,
`wherein each user’s signal is spread overthe entire bandwidth
`by its respective unique spreading code. This technique can
`provide for sharing, wherein one or more users can concur-
`
`2
`rently transmit and receive. Such sharing can be achieved
`through spread spectrum digital modulation, wherein a user’s
`stream of bits is encoded and spread across a very wide
`channel in a pseudo-random fashion. Thereceiveris designed
`to recognize the associated unique sequence code and undo
`the randomization in order to collect the bits for a particular
`user in a coherent manner.
`
`A typical wireless communication network (e.g., employ-
`ing frequency, time, and code division techniques) includes
`one or morebasestations that provide a coverage area and one
`or more mobile (e.g., wireless) terminals that can transmit and
`receive data within the coverage area. A typical base station
`can simultaneously transmit multiple data streams for broad-
`cast, multicast, and/or unicast services, wherein a data stream
`is a stream of data that can be of independent reception
`interest to a mobile terminal. A mobile terminal within the
`
`coverage area of that base station can be interested in receiv-
`ing one, more than oneor all the data streams carried by the
`composite stream. Likewise, a mobile terminal can transmit
`data to the base station or another mobile terminal. Such
`communication between base station and mobile terminal or
`
`between mobile terminals can be degraded due to channel
`variations and/or interference powervariations.
`Conventional wireless systems do not provide support
`adaptive communication techniques in non-linear receivers
`due to computational complexity, processing overhead, and
`the like. Thus, there exists a need in the art for a system and/or
`methodology of improving throughput in such wireless net-
`work systems.
`
`SUMMARY
`
`The following presents a simplified summary of one or
`more embodimentsin order to provide a basic understanding
`of such embodiments. This summary is not an extensive over-
`view of all contemplated embodiments, and is intended to
`neither identify key or critical elements of all embodiments
`nor delineate the scope of any or all embodiments. Its sole
`purposeis to present some concepts of one or more embodi-
`ments in a simplified form as a prelude to the more detailed
`description that is presentedlater.
`In accordance with one or more embodiments and corre-
`
`sponding disclosure thereof, various aspects are described in
`connection with performing rank selection and CQI compu-
`tation for a non-linear receiver, such as an ML-MMSE
`receiver, in a MIMO wireless communication environment.
`According to one aspect, a method of calculating rank in a
`non-linear receiver in a user device in a wireless communi-
`
`cation environment can comprise receiving a transmission
`signal at a non-linear receiver, determining a rank for one or
`morelayers of the transmission signal, and selecting a layer
`with an optimum rank that maximizes channelefficiency for
`transmissions. The method can further comprise employing a
`list-sphere decoding algorithm in the non-linear receiver to
`decode the received signal
`transmission. Additionally, a
`capacity-based rank selection protocol can be employed to
`determine rank of the received transmission, andat least one
`submatrix can be generated for each ofthe one or morelayers.
`Transmission capacity for each ofthe at least one submatrices
`can be evaluated and averagedfor each layer. The method can
`still further comprise identifying a rank for a layer with a
`highest average capacity, calculating a CQI, and feeding back
`the CQI and rank information using a reverse link control
`channel. The non-linear receiver can bea maximum life (ML)
`minimum mean-squared error (MMSE) non-linear receiver,
`and the wireless communication environment can be a mul-
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`16
`
`16
`
`

`

`US 8,971,461 B2
`
`3
`tiple input-multiple output (MIMO)single code word (SWC)
`wireless communication environment.
`
`Anotheraspect relates to a wireless communication appa-
`ratus that facilitates calculating rank in a non-linear receiver
`ina user device ina wireless communication environment can
`
`4
`trices, and determining an effective signal-to-noise ratio
`(SNR) for each submatrix. The processor can additionally
`execute instructions for generating the CQI information
`basedat least in part on the effective SNR ofa layer having the
`optimalrank, and for transmitting CQ] and rank information
`over the reverse link control channel approximately every 5
`ms.
`
`comprise a non-linear receiver that receives a signal with
`multiple layers, a memory that stores information related to
`rank calculation algorithms, and a processor coupled to the
`To the accomplishmentof the foregoing and related ends,
`memory that employs a rank calculation algorithm to deter-
`the one or more embodiments comprise the features herein-
`mine an optimum rank for at least one transmission layer in
`after fully described and particularly pointed out
`in the
`the received signal. The non-linear receiver can utilizealist-
`claims. The following description and the annexed drawings
`sphere decoding protocol to decode the received signal. The
`set forth in detail certain illustrative aspects ofthe one or more
`apparatus can further comprise a capacity mapping compo-
`embodiments. These aspects are indicative, however, of but a
`nent that evaluates transmission capacity for at least one
`few of the various ways in which the principles of various
`submatrix of at least one received layer, and a rank evaluation
`embodiments may be employed and the described embodi-
`componentthat identifies an optimal rank associated with a
`ments are intended to include all such aspects and their
`received layer having a highest average transmission capac-
`equivalents.
`ity. Additionally, the processor can generate a CQIreport for
`transmission over a reverse link control channel and can
`
`append a 2-bit optimal rank identifier thereto.
`Yet another aspect relates to a wireless communication
`apparatus, comprising means for means for performing a
`non-linear decoding protocol on a received multiple-layer
`signal at a user device, means for determining an optimal rank
`associated with at least one of the layers of the received
`signal, and meansfor transmitting information related to the
`optimal rank with CQI information overa reverse link control
`channel. The apparatus can additionally comprise means for
`performing a list-sphere decoding protocol to decode the
`received signal, means for generating a plurality of submatri-
`ces for each layer ofthe received signal and capacity mapping
`the submatrices, and means for determining an effective sig-
`nal-to-noise ratio (SNR) for each submatrix. Moreover, the
`apparatus can comprise means for generating CQI informa-
`tion related to the received signal basedat least in part on the
`effective SNR of a layer having the optimal rank. The means
`for transmitting can transmit CQI and rank information over
`the reverse link control channel approximately every 5 ms.
`Still another aspect relates to a computer-readable medium
`having stored thereon computer-executable instructions for
`employing a non-linear decoding protocol in a user device to
`decode a received multiple-layer signal, identifying an opti-
`mal rank associated with at least one of the layers of the
`received signal, generating CQI information for the received
`signal based atleast in part on the identified rank, and trans-
`mitting CQ] and rank information overa reverse link control
`channel. The computer-readable medium can additionally
`comprise instructions for performing a list-sphere decoding
`protocol to decode the received signal, for generating a plu-
`rality of submatrices for each layer of the received signal and
`capacity mapping the submatrices, and for determining an
`effective signal-to-noise ratio (SNR) for each submatrix. Still
`furthermore, the computer-readable medium can comprise
`instructions for generating the CQI information basedat least
`in part on the effective SNR of a layer having the optimal
`rank.
`
`A further aspect provides for a processor that executes
`instructions for employing a non-linear decoding protocol in
`auser device to decode a received multiple-layer signal, iden-
`tifying an optimal rank associated with at least one of the
`layers of the received signal, generating CQI information for
`the received signal basedat least in part on the identified rank,
`and transmitting CQI and rank information over a reverse link
`control channel. The instructions can further comprise per-
`forming a list-sphere decoding protocol
`to decode the
`received signal, generating a plurality of submatrices for each
`layer of the received signal and capacity mapping the subma-
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
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`
`FIG.1 illustrates a wireless network communication sys-
`tem in accordance with various embodiments presented
`herein.
`FIG.2 is an illustration of a multiple access wireless com-
`munication system according to one or more embodiments.
`FIG.3 is an illustration of a system thatfacilitates perform-
`ing rank prediction with an SWCtransmitter in a wireless
`device, in accordance with one or more aspects.
`FIGS. 4-6 illustrate a trellis representation ofa list-sphere
`decoding protocol and optimization thereof, in accordance
`with one or more aspects described herein.
`FIG.7 illustrates a methodology for performing capacity-
`based rank selection in a non-linear receiver in an access
`
`terminal, in accordance with one or moreaspects.
`FIG.8 is an illustration of a methodology for performing
`maximum rank selection in conjunction with a single code
`word communication design in a non-linear receiver in an
`access terminal, in accordance with various aspects set forth
`herein.
`FIG.9 is an illustration of a methodology for determining
`rank in a minimum mean-squared error (MMSE)-based non-
`linear receiver in an access terminal, in accordance with one
`or more aspects set forth herein.
`FIG. 10 is an illustration of a user device that facilitates
`calculating rank of a received transmission layer in a non-
`linear receiver employed in a wireless communication envi-
`ronment, in accordance with one or more aspects set forth
`herein.
`
`FIG.11 is an illustration of a system thatfacilitates updat-
`ing arank for a user device that employs a non-linear receiver
`in a Wireless communication environment in accordance with
`various aspects.
`FIG.12 is an illustration ofa wireless network environment
`that can be employed in conjunction with the various systems
`and methods described herein.
`
`FIG. 13 is an illustration of an apparatus that facilitates
`performing rank prediction in a non-linear receiver of an
`access terminal, in accordance with one or moreaspects.
`
`DETAILED DESCRIPTION
`
`Various embodiments are now described with reference to
`the drawings, wherein like reference numerals are used to
`refer to like elements throughout. In the following descrip-
`tion, for purposes of explanation, numerousspecific details
`are set forth in order to provide a thorough understanding of
`one or more embodiments. It may be evident, however, that
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`one skilled in the art. Mobile devices 104 can be, for example,
`such embodiment(s) may be practiced without these specific
`details. In other instances, well-knownstructures and devices
`cellular phones, smart phones, laptops, handheld communi-
`cation devices, handheld computing devices, satellite radios,
`are shownin block diagram form inorderto facilitate describ-
`global positioning systems, PDAs, and/or any other suitable
`ing one or more embodiments.
`device for communicating over wireless network 100.
`As used in this application, the terms “component,” “sys-
`According to various aspects described herein, when
`tem,”andthelike are intendedto refer to a computer-related
`employing a MIMO-MMSEreceiver(e.g., in a base station
`entity, either hardware, software, software in execution, firm-
`102 and/or a user device 104), the rank prediction and CQI
`ware, middle ware, microcode, and/or any combination
`computation (e.g., for a given rank) can be performed with
`thereof. For example, a component may be,but is not limited
`relative ease. However, when utilizing a list-sphere decoder
`to being, a process running on a processor, a processor, an
`technique, rank prediction and CQI computation can be more
`object, an executable, a thread ofexecution, a program, and/or
`challenging dueto the non-linearity of the receiver. Conven-
`a computer. One or more components may reside within a
`tional systems and/or methodologies cannot support integra-
`process and/or thread of execution and a component may be
`tion ofa list-sphere decoder design in a MIMOsystem, and
`localized on one computer and/or distributed between two or
`thus cannot exploit the performance benefits ofa list-sphere
`more computers. Also, these components can execute from
`decoder design. Various aspects presented herein describe
`various computer readable media having various data struc-
`systems and/or methods that can facilitate implementing a
`tures stored thereon. The components may communicate by
`list-sphere decoder in a MIMOsystem to improve system
`wayof local and/or remote processes such as in accordance
`with a signal having one or more data packets (e.g., data from
`performance. For example, MIMO channel capacity can be
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`one componentinteracting with another componentinalocal utilized as a metric for CQ] and rank prediction, based at least
`system, distributed system, and/or across a network such as
`in part on an assumption of a sphere decodergap to capacity,
`the Internet with other systems by wayof the signal). Addi-
`as described in greater detail below.
`tionally, components of systems described herein may be
`Referring now to FIG. 2, a multiple access wireless com-
`rearranged and/or complimented by additional components
`munication system 200 according to one or more embodi-
`in order to facilitate achieving the various aspects, goals,
`ments is illustrated. System 200 is presented for illustrative
`advantages, etc., described with regard thereto, and are not
`purposes and can be utilized in conjunction with various
`limited to the precise configurationssetforth in a given figure,
`aspects set forth below. A 3-sector base station 202 includes
`as will be appreciated by one skilled in theart.
`multiple antenna groups: one including antennas 204 and
`Furthermore, various embodimentsare described herein in
`206, another including antennas 208 and 210, and a third
`connection with a subscriberstation. A subscriber station can
`including antennas 212 and 214. Accordingtothefigure, only
`two antennas are shown for each antenna group, however,
`more or fewer antennas may be utilized for each antenna
`group. Mobile device 216 is in communication with antennas
`212 and 214, where antennas 212 and 214 transmit informa-
`tion to mobile device 216 over forward link 220 and receive
`information from mobile device 216 over reverse link 218.
`Mobile device 222 is in communication with antennas 204
`and 206, where antennas 204 and 206 transmit information to
`mobile device 222 over forward link 226 and receive infor-
`mation from mobile device 222 over reverse link 224.
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`also be called a system, a subscriber unit, mobile station,
`mobile, remote station, access point, remote terminal, access
`terminal, user terminal, user agent, a user device, or user
`equipment. A subscriber station may be a cellular telephone,
`a cordless telephone, a Session Initiation Protocol (SIP)
`phone,a wireless local loop (WLL)station, a personaldigital
`assistant (PDA), a handheld device having wireless connec-
`tion capability, or other processing device connected to a
`wireless modem.
`Moreover, various aspects or features described herein
`may be implemented as a method, apparatus, or article of
`manufacture using standard programming and/or engineer-
`ing techniques. The term “article of manufacture” as used
`herein is intended to encompass a computer program acces-
`sible from any computer-readable device, carrier, or media.
`For example, computer-readable media can include but are
`not limited to magnetic storage devices (e.g., hard disk,
`floppy disk, magnetic strips ...), optical disks (e.g., compact
`disk (CD), digital versatile disk (DVD). ..), smart cards, and
`flash memory devices (e.g., card, stick, key drive... ).
`Additionally, various storage media described herein can rep-
`resent one or more devices and/or other machine-readable
`
`media for storing information. The term machine-readable
`medium” can include, without being limited to, wireless
`channels and various other media capableofstoring, contain-
`ing, and/or carrying instruction(s) and/or data.
`Referring now to FIG. 1, a wireless network communica-
`tion system 100 is illustrated in accordance with various
`embodiments presented herein. Network 100 can comprise
`one or more base stations 102 in one or more sectors that
`receive, transmit, repeat, etc., wireless communication sig-
`nals to each other and/or to one or more mobile devices 104.
`Eachbase station 102 can comprise a transmitter chain and a
`receiver chain, each of which can in turn comprise a plurality
`ofcomponentsassociated with signal transmission and recep-
`tion (e.g., processors, modulators, multiplexers, demodula-
`tors, demultiplexers, antennas,etc.), as will be appreciated by
`
`Each group of antennas and/or the area in which they are
`designated to communicate is often referred to as a sector of
`base station 202. In one embodiment, antenna groups each are
`designed to communicate to mobile devices in a sector of the
`areas covered by base station 202. In communication over
`forward links 220 and 226, the transmitting antennas of base
`station 202 can utilize beam-forming techniques in order to
`improve the signal-to-noise ratio of forward links for the
`different mobile devices 216 and 222. Additionally, a base
`station using beam-forming to transmit to mobile devices
`scattered randomly through its coverage area causes less
`interference to mobile devices in neighboring cells/sectors
`than a basestation transmitting through a single antennato all
`mobile devices in its coverage area. A base station may be a
`fixed station used for communicating with the terminals and
`mayalso bereferred to as an access point, a Node B, or some
`other terminology. A mobile device may also be called a
`mobile station, user equipment (UE), a wireless communica-
`tion device, terminal, access terminal, user device, or some
`other terminology.
`According to one or more aspects, user devices 216 and
`222, as well as base station 202, can utilize a single code word
`(SCW) design with rank prediction in conjunction with a
`MIMO-MMSEreceiver. The utilization of such receivers
`
`with a SCW design can facilitate closing a performance gap
`between an SCW design and a multiple code word (MCW)
`capacity-achieving design. For instance, a list sphere decod-
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`US 8,971,461 B2
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`7
`ing technique for an SCW design can achieve up to 1.5 dB
`gain for signal-to-noise ratios (SNRs) lower than 15 dB, and
`can provide up to 3.5 dB gain for SNRsgreater than 20 dB.
`AMIMOreceiver design can have two modesof operation:
`single code word (SCW) and multiple-code word (MCW).
`The MCW modecanbe capacity-achieving becausethe trans-
`mitter can encode data transmitted on each spatial layer inde-
`pendently, potentially with different rates. The receiver
`employs a successive interference cancellation (SIC) algo-
`rithm which worksas follows: decode a 1°’ layer; subtractits
`contribution from the received signal after re-encoding; mul-
`tiply the encoded 1° layer with the “estimated channel”;
`decode the 2”” layer and so on. This “onion-peeling