OFDM transmitter and method for multi-user MIMO transmissions

1. A wireless communication device comprising:

an orthogonal-frequency division multiplexed (OFDM) transceiver configured for transmitting a data unit in accordance with a multiple-input multiple-output (MIMO) technique over a wideband channel comprising a 20 MHz channel and another channel using a plurality of spatially diverse antennas; and

a controller to include in the data unit, a parameter indicating a modulation and coding scheme and a parameter indicating number of spatial streams,

wherein each of the spatial streams is encoded and beamformed for receipt by one or more different receiving stations.

2. The device of claim 1 wherein the 20 MHz channel is a primary channel and the other channel is a secondary channel having a channel bandwidth of at least one of 20 MHz, 40 MHz or 80 MHz.

3. The device of claim 2 wherein the transceiver is configured to utilize a request-to-send/clear-to-send (RTS/CTS) signaling structure to negotiate the parameters.

4. The device of claim 2 wherein the spatial streams are transmitted through a MIMO channel for receipt by the different receiving stations.

5. The device of claim 4 wherein the transceiver further includes subcarrier modulators to modulate groups of encoded bits onto OFDM subcarriers based on the modulation and coding scheme, and

wherein the modulation and coding scheme for each of the OFDM subcarriers is determined from channel characteristics of each of the OFDM subcarriers.

6. The device of claim 5 wherein the subcarrier modulators are configured to modulate groups having a greater number of encoded bits at higher-order modulation levels and modulate groups having a lesser number of encoded bits at lower-order modulation levels.

7. The device of claim 6 wherein the transceiver further includes circuitry to combine the modulated groups of encoded bits for transmission through spatial channels.

8. The device of claim 7 wherein the spatial channels are non-orthogonal and have different multipath characteristics.

9. The device of claim 8 wherein the transceiver further includes circuitry to perform beamforming on the modulated groups of encoded bits for transmission of the spatial streams through the spatial channels.

10. The device of claim 2 wherein the device is an access point, and

wherein the data unit is transmitted utilizing both the primary and the secondary channels.

11. An orthogonal-frequency division multiplexed (OFDM) transmitter configured to:

transmit a data unit in accordance with a multiple-input multiple-output (MIMO) technique over a wideband channel comprising a 20 MHz channel and another channel using a plurality of spatially diverse antennas; and

include in the data unit, a parameter indicating a modulation and coding scheme and a parameter indicating number of spatial streams,

wherein each of the spatial streams is encoded and beamformed for receipt by one or more different receiving stations.

12. The OFDM transmitter of claim 11 wherein the 20 MHz channel is a primary channel and the other channel is a secondary channel having a channel bandwidth of at least one of 20 MHz, 40 MHz or 80 MHz, and

wherein the data unit is transmitted utilizing both the primary and the secondary channels.

13. The OFDM transmitter of claim 12 wherein the spatial streams are transmitted through a MIMO channel for receipt by the different receiving stations.

14. The OFDM transmitter of claim 13 wherein the transceiver further includes subcarrier modulators to modulate groups of encoded bits onto OFDM subcarriers based on the modulation and coding scheme, and

wherein the modulation and coding scheme for each of the OFDM subcarriers is determined from channel characteristics of each of the OFDM subcarriers.

15. A method for transmitting orthogonal-frequency division multiplexed (OFDM) signals, the method comprising:

transmitting a data unit in accordance with a multiple-input multiple-output (MIMO) technique over a wideband channel comprising a 20 MHz channel and another channel using a plurality of spatially diverse antennas;

including in the data unit, a parameter indicating a modulation and coding scheme and a parameter indicating number of spatial streams; and

encoding and beamforming each of the spatial streams for receipt by one or more different receiving stations,

wherein the spatial streams are transmitted through a MIMO channel for receipt by the different receiving stations.

16. The method of claim 15 wherein the 20 MHz channel is a primary channel and the other channel is a secondary channel having a channel bandwidth of at least one of 20 MHz, 40 MHz or 80 MHz, and

wherein the method further comprises utilizing a request-to-send/clear-to-send (RTS/CTS) signaling structure to negotiate the parameters.