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 configured to:
analyze one or more channel conditions of a wireless communication channel between the receiver and a transmitter having a plurality of transmit antennas;
based on the analyzed one or more channel conditions, select one of a spatial-multiplexing (SM) format or a transmit diversity format and one or more transmission layers for use in transmission to the receiver, wherein the selected one of the SM format or the transmit diversity format are selected from a defined subset of available formats; and
generate, for transmission to the transmitter, feedback information indicating the selected one of the SM format or the transmit diversity format for transmission and the one or more transmission layers, wherein the one or more transmission layers are included in a rank indication in the feedback information.
2. The system of claim 1 , wherein the transmit diversity format includes a single data stream.
3. The system of claim 2 , wherein the single data stream comprises four transmission intervals during which four symbols are transmitted.
4. The system of claim 1 , wherein the transmit diversity format comprises a space time transmit diversity (STTD) format.
5. The system of claim 4 , wherein the STTD format is proportionally weighted.
6. The system of claim 1 , wherein the SM format includes two data streams.
7. The system of claim 6 , wherein a first stream of the two data streams is weighted.
8. The system of claim 1 , wherein the feedback information specifies beam-forming information usable by the transmitter.
9. The system of claim 1 , wherein power is increased for a first transmission layer of the one or more transmission layers based on the channel conditions.
10. A method, comprising:
at a receiver in a multiple input multiple output (MIMO) system:
analyzing one or more channel conditions of a wireless communication channel between the receiver and a transmitter having a plurality of transmit antennas;
based on the analyzed one or more channel conditions, selecting one of a spatial-multiplexing (SM) format or a transmit diversity format and one or more transmission layers for use in transmission to the receiver, wherein the selected one of the SM format or the transmit diversity format are selected from a defined subset of available formats; and
generating, for transmission to the transmitter, feedback information indicating the selected one of the SM format or the transmit diversity format for transmission and the one or more transmission layers, wherein the one or more transmission layers are included in a rank indication in the feedback information.
11. The method of claim 10 , wherein the transmit diversity format includes a single data stream.
12. The method of claim 11 , wherein the single data stream comprises four transmission intervals during which four symbols are transmitted.
13. The method of claim 10 , wherein the transmit diversity format comprises a space time transmit diversity (STTD) format.
14. The method of claim 13 , wherein the STTD format is proportionally weighted.
15. The method of claim 10 , wherein the SM format includes two data streams.
16. The method of claim 15 , wherein a first stream of the two data streams is weighted.
17. The method of claim 10 , wherein the feedback information specifies beam-forming information usable by the transmitter.
18. The method of claim 10 , wherein power is increased for a first transmission layer of the one or more transmission layers based on the channel conditions.