Closed loop MIMO systems and methods
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.
1. A multiple input multiple output (MIMO) system comprising:
a receiver having at least one receive antenna, wherein the receiver is configured to:
analyze one ore more channel conditions of a communication with a transmitter having a plurality of transmit antennas;
based on the one or more channel conditions, select a spatial-multiplexing (SM) format for transmission in the communication and two or more of the plurality of transmit antennas for use in the transmission, wherein the two or more antennas are selected by using determinants of sub-MIMO channel matrices; and
transmit, to the transmitter, feedback information specifying the selected SM format and two or more transit antennas.
2. The system of claim 1 wherein the receiver is configured to:
based on one or more channel conditions, select a space time transmit diversity (STTD) format for the transmission and a grouping of the plurality of antennas for use in the transmission; and
transmit, to the transmitter, feedback information specifying the selected STTD format and the grouping of the plurality of antennas.
3. The system of claim 1 , wherein the feedback information specifies beam-forming information usable by the transmitter.
4. The system of claim 3 wherein the beam-forming information includes elements of a V matrix of a SVD decomposed channel matrix or parameters of a Givens decomposition.
5. The system of claim 1 , wherein the receiver is configured to analyze channel conditions based on received pilots transmitted from the plurality of transmit antennas.
6. The system of claim 1 , wherein the receiver has a plurality of receive antennas.
7. A base station, comprising:
a plurality of reception antennas; and
a receiver coupled to the plurality of reception antennas, wherein the receiver is configured to:
receive a transmission over a multiple-input multiple-output (MIMO) channel from a transmitter having a plurality of transmission antennas;
based on one or more conditions of the MIMO channel, select a spatial multiplexing (SM) mode and two or more of the plurality of transmission antennas to be used by the transmitter while operating in the SM mode, wherein the two or more antennas are selected by using determinants of sub-MIMO channel matrices; and
specifying the selected SM mode and two or more transmission antennas to the transmitter.
8. The base station of claim 7 , wherein the receiver is configured to select the two or more transmission antennas based on one or more pilot signals broadcasted by the transmitter.
9. The base station of claim 7 , wherein the receiver is configured to specify information usable to facilitate performance of beam forming by the transmitter.