MIMO system and mode table
A method for determining antenna usage in a multiple input multiple output (MIMO) wireless communication system. The method includes exchanging information between terminals concerning the number of transmit antennas and number of receive antennas. In some embodiments antenna usage is based on the number of transmit antennas, the number of receive antennas, and an indication of channel quality. In some embodiments less than all of the available antennas, particularly transmit antennas, are used at a given time, with unused transmit antennas varying over time.
1 . A method of determining communication modes between wireless terminals using multiple transmit and/or receive antennas, comprising:
determining a number of transmit antennas for a first terminal;
determining a number of receive antennas for a second terminal;
determining a channel quality measure for communications between the first terminal and the second terminal; and
selecting a communication mode based on the number of transmit antennas, the number of receive antennas, and the channel quality measure.
2 . The method of claim 1 wherein the communication mode indicates use of transmit antennas and receive antennas.
3 . The method of claim 1 wherein the communication mode is selected from a set of allowed modes.
4 . The method of claim 1 wherein the communication mode is a space time block code mode.
5 . The method of claim 1 wherein the communication mode is a spatial multiplex mode.
6 . The method of claim 1 wherein the communication mode is a space time block code when the channel quality measure indicates a low channel quality and a spatial multiplex mode when the channel quality measure indicates a high channel quality.
7 . The method of claim 1 wherein the first terminal determines the number of transmit antennas for the first terminal, the number of receive antennas for the second terminal, the channel quality measure for communications between the first terminal and the second terminal, and selects the communication mode.
8 . The method of claim 7 further comprising receiving an indication of the number of receive antennas for the second terminal by the first terminal.
9 . The method of claim 8 wherein the indication of the number of receive antennas for the second terminal is received as part of a field in a packet header.
10 . The method of claim 9 further comprising transmitting an indication of the number of transmit antennas for the first terminal to the second terminal.
11 . The method of claim 10 wherein the indication of the number of transmit antennas for the first terminal is transmitted as part of a field in a packet header.
12 . The method of claim 3 wherein the set of allowed modes includes modes wherein use of transmit antennas varies over time.
13 . The method of claim 3 wherein the set of allowed modes includes modes wherein use of transmit antennas varies over subcarriers.
14 . The method of claim 3 wherein the set of allowed modes includes modes wherein use of transmit antennas varies over time and varies over subcarriers.
15 . The method of claim 3 wherein the set of allowed modes includes at least some of an Alamouti space time block code mode, an Alamouti space time block code with maximum ratio combining, a circular Alamouti space time block code, a spatial multiplex mode, and a circular spatial multiplex mode.
16 . A method relating to communicating between wireless terminals using multiple transmit and/or receive antennas, comprising:
determining a number of transmit antennas for a first terminal;
determining a number of receive antennas for a second terminal; and
selecting a communication mode based on the number of transmit antennas and the number of receive antennas;
wherein the communication mode varies use of transmit antennas.
17 . The method of claim 16 wherein the number of transmit antennas used varies over time, with the number of transmit antennas being K, the number of transmit antennas used at a given time is K-x, and the antennas comprising transmit antennas K-x varies over time.
18 . The method of claim 16 wherein the number of transmit antennas K-x varies over subfrequencies.
19 . A transmitter in a wireless communication system, comprising:
circuitry for communicating in a wireless network;
multiple antennas for transmitting in the wireless network;
a mode processing block for determining a multiple input multiple output (MIMO) mode indicating usage of the multiple antennas.
20 . The transmitter of claim 19 wherein the mode processing block determines the MIMO mode based on a number of receive antennas of a receiver and the number of multiple antennas for transmitting.
21 . The transmitter of claim 20 wherein the mode processing block further determines the MIMO mode based on an indication of channel quality between the receiver and the transmitter.
22 . A method performed by an element in a wireless communication system, comprising:
transmitting an initial data packet;
receiving an acknowledgement data packet in response to the initial data packet, the acknowledgement data packet including an indication of a number of antennas for a first use;
determining a multiple input multiple output mode based on the number of antennas for the first use and a number of antennas for a second use, the first use being for one of receiving or transmitting and the second use being for the other of receiving or transmitting.