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Method and apparatus for providing antenna diversity in a wireless communication systemRelated Patent Categories: Pulse Or Digital Communications, Systems Using Alternating Or Pulsating Current, Plural Channels For Transmission Of A Single Pulse TrainMethod and apparatus for providing antenna diversity in a wireless communication system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070041457, Method and apparatus for providing antenna diversity in a wireless communication system. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present application claims priority to provisional U.S. Application Ser. No. 60/710.408, entitled "Method and Apparatus for Antenna Diversity in Multi-input Multi-Output Communication Systems," filed Aug. 22, 2005, and provisional U.S. Application Ser. No. 60/711,144 entitled "Method and Apparatus for Antenna Diversity in Multi-input Multi-Output Communication Systems," filed Aug. 24, 2005, both assigned to the assignee hereof and incorporated herein by reference. The present application is further related to commonly assigned U.S. patent application Ser. No. to be determined, entitled "Adaptive Sectorization in Cellular Systems," filed on the same day herewith, and incorporated herein by reference. BACKGROUND [0002] I. Field [0003] The present disclosure relates generally to communication, and more specifically to transmission schemes for wireless communication. [0004] II. Background [0005] In a wireless communication system, a transmitter (e.g., a base station or a terminal) may utilize multiple (T) transmit antennas for data transmission to a receiver equipped with one or more (R) receive antennas. The multiple transmit antennas may be used to increase system throughput by transmitting different data from these antennas and/or to improve reliability by transmitting data redundantly. For example, the transmitter may transmit a given symbol from all T transmit antennas, and the receiver may receive multiple versions of this symbol via the R receive antennas. These multiple versions of the transmitted symbol generally improve the receiver's ability to recover the symbol. [0006] Transmission performance may be improved by exploiting the spatial dimension obtained with the multiple transmit antennas and, if present, the multiple receive antennas. A propagation path exists between each pair of transmit and receive antennas. TR different propagation paths are formed between the T transmit antennas and the R receive antennas. These propagation paths may experience different channel conditions (e.g., different fading, multipath, and interference effects) and may achieve different signal-to-noise-and-interference ratios (SNRs). The channel responses for the TR propagation paths may vary from path to path and may further vary across frequency for a dispersive wireless channel and/or over time for a time-variant wireless channel. [0007] A major drawback to using multiple transmit antennas for data transmission is that the channel response between each pair of transmit and receive antennas (or each propagation path) typically needs to be estimated in order to properly receive the data transmission. Estimation of the fall channel response for all TR transmit and receive antenna pairs may be undesirable for several reasons. First, a large amount of link resources may be consumed in order to transmit a pilot used for channel estimation, which in turn reduces the link resources available to transmit data. Second, channel estimation for all TR transmit and receive antenna pairs increases processing overhead at the receiver. [0008] There is therefore a need in the art for transmission schemes that can ameliorate the need to estimate the fall channel response for all transmit and receive antenna pairs. SUMMARY [0009] Transmission schemes that can flexibly achieve the desired spatial multiplexing order, spatial diversity order, and channel estimation overhead order are described herein. The spatial multiplexing order determines the number of symbols to send simultaneously on one subcarrier in one symbol period, the spatial diversity order determines the amount of spatial diversity observed by the transmitted symbols, and the channel estimation overhead order determines the amount of pilot overhead. [0010] In an embodiment, for a data transmission from a transmitter to a receiver, the subcarriers assigned to the receiver and the spatial multiplexing order (M) for the receiver are determined, where M.gtoreq.1. For each assigned subcarrier, M virtual antennas are selected from among V virtual antennas formed with V columns of an orthonormal matrix, where V.gtoreq.M. V may be selected to achieve the desired spatial diversity order and channel estimation overhead order. The M virtual antennas for each assigned subcarrier may be selected in various manners, as described below. Output symbols for the receiver are mapped to the M virtual antennas selected for each assigned subcarrier by applying the orthonormal matrix. Pilot symbols are also mapped to the V virtual antennas. The mapped output symbols and pilot symbols (or transmit symbols) are provided for transmission from T physical transmit antennas, where T.gtoreq.V. Transmission symbols (e.g., OFDM symbols or SC-FDMA symbols) are generated for each transmit antenna based on the transmit symbols for that transmit antenna. Different cyclic delays may be applied to the transmission symbols for the T transmit antennas. [0011] Various aspects and embodiments of the invention are described in further detail below. BRIEF DESCRIPTION OF THE DRAWINGS [0012] The features and nature 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. [0013] FIG. 1 shows a wireless communication system. [0014] FIGS. 2A and 2B show MISO and MIMO channels, respectively. [0015] FIG. 3 shows a transmission scheme with virtual antennas. [0016] FIG. 4 shows a transmission scheme with virtual antennas and cyclic delay diversity. [0017] FIG. 5 shows a MIMO transmission by cycling through the virtual antennas. [0018] FIGS. 6A, 6B and 6C show three exemplary subcarrier structures. [0019] FIG. 7 shows an exemplary frequency hopping scheme. [0020] FIG. 8 shows an exemplary pilot scheme for symbol rate hopping. [0021] FIG. 9A through 9D show four exemplary pilot schemes for block hopping. Continue reading about Method and apparatus for providing antenna diversity in a wireless communication system... Full patent description for Method and apparatus for providing antenna diversity in a wireless communication system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and apparatus for providing antenna diversity in a wireless communication system 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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