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  Closed loop mimo systems and methodsUSPTO Application #: 20080108310Title: Closed loop mimo systems and methods Abstract: Systems and methods for closed loop MIMO (multiple input and multiple output) wireless communication are provided. Various transmit formats including spatial multiplexing and STTD are defined in which vector or matrix weighting is employed using information fed back from receivers. The feedback information may include channel matrix or SVD-based feedback. (end of abstract)
Agent: Smart & Biggar P.o. Box 2999, Station D - Ottawa, ON, CA Inventors: Wen Tong, Ming Jia, Jianglei Ma, Peiying Zhu, Hua Xu, Dong-Sheng Yu, Hang Zhang, Mo-Han Fong USPTO Applicaton #: 20080108310 - Class: 455069000 (USPTO) Related Patent Categories: Telecommunications, Transmitter And Receiver At Separate Stations, With Control Signal, Transmitter Controlled By Signal Feedback From Receiver The Patent Description & Claims data below is from USPTO Patent Application 20080108310. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Patent Application No. 60/581,356 filed on Jun. 22, 2004, U.S. Provisional patent Application No. 60/582,298 filed on Jun. 24, 2004, U.S. Provisional Patent Application No. 60/601,178 filed on Aug. 13, 2004, Provisional Patent Application No. 60/514,621 filed on Sep. 30, 2004, Provisional Patent Application No. 60/619,461 filed on Oct. 15, 2004 and Provisional Patent Application No. 60/642,697 filed on Jan. 10, 2005, all of which are hereby incorporated by reference in their entirety. FIELD OF THE INVENTION [0002] The invention relates to MIMO (multiple input, multiple output) systems and methods. BACKGROUND OF THE INVENTION [0003] In MIMO (multiple input multiple output) OFDM (orthogonal frequency division multiplexing) systems, there are multiple transmit antennas and multiple receive antennas and a plurality of sub-carriers that are available for transmission between the transmit antennas and the receive antennas for either one or multiple users. New advances in MIMO OFDM systems are taught in Applicant's co-pending application <attorney docket 71493-1320> entitled "Pilot Design For OFDM Systems With Four transmit Antennas" filed Mar. 15, 2005, and in Applicant's co-pending application <attorney docket 71493-1330) entitled "Wireless Communication Methods, Systems, And Signal Structures" filed Apr. 4, 2005, both hereby incorporated by reference in their entirety. With open loop implementations, the transmitter transmits on the multiple transmitter antennas and sub-carriers without the benefit of channel information fed back from the receivers. [0004] Efforts have been made to facilitate wireless closed-loop MIMO communications including broadband closed-loop MIMO, which might for example be based on OFDM modulation schemes, and narrowband closed-loop MIMO. Broadband closed-loop MIMO includes many sub-bands. Each of these sub-bands requires MTMO channel feedback for a closed-loop implementation. As a result the feedback resources required for broadband closed-loop MIMO can become quite large. Narrowband closed-loop MIMO, by comparison, includes one or a few sub-bands and requires a relatively smaller amount of feedback resources. Broadband and narrowband MIMO, therefore, have different applications. SUMMARY OF THE INVENTION [0005] According to one broad aspect, the invention provides a MIMO system comprising: a transmitter having multiple transmit antennas; at least one receiver, each receiver having at least one receive antenna; each receiver being adapted to transmit at least one type of feedback information selected from a group consisting of: information for use in performing beam-forming; antenna selection/grouping information. [0006] In some embodiments, a transmission format to each receiver is selected from a group of transmission formats consisting of: spatial multiplexing; vector weighted spatial multiplexing; matrix weighted spatial multiplexing; K-stream spatial multiplexing employing more than K transmit antennas; single stream STTD; single stream STTD with proportional weighting and antenna selection; multi-stream STTD; multi-stream STUD with layer weighting; multi-stream STTD with a combination of layer weighting and proportional weighting; and hybrid beam-forming and spatial multiplexing. [0007] In some embodiments, a defined sub-set of available formats is made available for a given receiver, and wherein the given receiver feeds back a selection of one of the defined sub-set of available formats. [0008] In some embodiments, each receiver performs respective channel measurements and feeds back information for use in performing beam-forming based on the respective channel measurements. [0009] In some embodiments, the information for use in performing beam-forming is selected from a group consisting of: a) elements of a measured channel matrix; b) elements of a V matrix of a SVD decomposed channel matrix; c) parameters of a Givens decomposition of a V matrix of a SVD decomposed channel matrix; d) parameters of a truncated Givens decomposition of a V matrix of a SVD decomposed channel matrix, where one or more eigen-vectors are discarded; e) differentially encoded elements of a measured channel matrix; f) differentially encoded elements of a V matrix of a SVD decomposed channel matrix; g) differentially encoded parameters of a Givens decomposition or truncated Givens decomposition of a V matrix of a SVD decomposed channel matrix; h) Householder decomposition; i) full scalar quantization of any of the information types of a) through h); j) partial scalar quantization of any of the information types a) through g); k) scalar quantization of any one of the information types a) through h) where varying resolution is used to quantize parameters; l) vector quantization of any of the information types of a) through h); m) a combination of scalar quantization and differential quantization for any of the information types a) through h); n) using a Delta Sigma quantizer for any of the information types a) through h); o) binary beam-forming weights; p) a differential index into a set of vector quantizations; and q) pre-defined codebook. [0010] In some embodiments beam-forming feedback is performed by each receiver as a function of receiver specific criteria. [0011] In some embodiments, the receiver specific criteria is selected from a group consisting of: Max SNR; b) Max Shannon capacity; and c) True receiver operational process. [0012] In some embodiments, antenna selection/grouping information is at least one information type selected from a group consisting of: a) selection between SM (spatial multiplexing) and STTD (space time transmit diversity) transmission format; b) selection of particular antennas for SM transmission; c) selection and grouping of particular antennas for STTD transmission; and d) eigen-mode selection information. [0013] In some embodiments, the system further comprises the receiver determining the antenna selection/grouping information by performing a step selected from a group of steps consisting of: performing SVD decomposition and discarding weak eigen-modes; selecting antennas using determinants of sub-MIMO channel matrices. [0014] In some embodiments, feed back and beam-forming and/or antenna selection/grouping is performed for sub-carriers of a multi-carrier system to a resolution selected from a group consisting of: a) for every sub-carrier individually; b) for groups of consecutive sub-carriers; c) for an entire set of sub-carriers; d) for sets of groups of sub-carriers. [0015] In some embodiments, transmission matrices and feedback are in accordance with one of FIGS. 11 to 14. [0016] In some embodiments, the transmitter transmits pilots on each transmit antenna for use in performing channel estimation. [0017] In some embodiments, at least some of the pilots are punctured pilots. [0018] In some embodiments, at least some of the pilots comprise un-coded pilots for use by multiple receivers. [0019] In some embodiments, the pilots comprise user specific pre-coded pilots for use by particular receivers receivers. [0020] In some embodiments, the pilots comprise user specific pre-coded pilots for use by particular receivers receivers and un-coded pilots for use by multiple receivers. Continue reading... Full patent description for Closed loop mimo systems and methods Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Closed loop mimo systems and methods patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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