Estimating channel conditions in a MIMO OFDM communication system

1. A method of estimating channel conditions for use in optimizing transmission capacity between a transmitter and receiver in a multiple-input, multiple-output (MIMO) communication system, data being transmitted from the transmitter to the receiver over a bandwidth partitioned into multiple frequency channels, the data being divided into multiple data streams each of which is transmitted on a different frequency channel, each data stream being divided into multiple layers transmitted simultaneously within each frequency channel, the transmitter using pre-coding matrices for multiplexing the multiple layers within each frequency channel, the method including the steps of, at the receiver:

in a signal-to-interference-and-noise ratio (SINR) calculation block, computing a SINR metric for all pre-coding matrices;

in a rank estimation block, computing a first capacity metric for the bandwidth from the SINR metrics, and selecting a rank which maximizes the first capacity metric;

in a pre-coding matrix estimation block, computing a second capacity metric for each frequency channel from the SINR metrics and the selected rank, and selecting one or more pre-coding matrices which maximize the second capacity metric;

in a channel quality indicator estimation block, computing a third capacity metric from the second capacity metric, selected rank and selected one or more pre-coding matrices for each transmission layer within each frequency channel, and selecting one or more frequency channels which maximize the third capacity metric; and

transmitting the selected rank, selected one or more pre-coding matrices and selected one or more frequency channels to the transmitter for use in subsequent data transmissions.

2. A method according to claim 1 , wherein the step of computing the SINR metric includes:

computing the SINR for each sub-band from signal power estimates and noise power estimates.

3. A method according to claim 1 , wherein the SINR metric is computed from channel estimates of the frequency channels.

4. A method according to claim 3 further including the step of:

using a time-domain average of a plurality of channel estimates to compute the SINR metric.

5. A method according to claim 3 further including the step of:

using a frequency-domain sampling of a plurality of channel estimates to compute the SINR metric.

6. A method according to claim 2 wherein the SINR metric is computed from channel estimates of the frequency channels.

7. A method according to claim 4 further including the step of: using a frequency-domain sampling of a plurality of channel estimates to compute the SINR metric.

8. A receiver for use in a multiple-input, multiple-output (MIMO) communication system in which data is transmitted from a transmitter to the receiver over a bandwidth partitioned into multiple frequency channels, the data being divided into multiple data streams each of which is transmitted on a different frequency channel, each data stream being divided into multiple layers transmitted simultaneously within each frequency channel, the transmitter using pre-coding matrices for multiplexing the multiple layers within each frequency channel, the receiver including:

a signal-to-interference-and-noise ratio (SINR) calculation block for computing a SINR metric for all pre-coding matrices;

a rank estimation block for computing a first capacity metric for the bandwidth from the SINR metrics, and for selecting a rank which maximizes the first capacity metric;

a pre-coding matrix estimation block for computing a second capacity metric for each frequency channel from the SINR metrics and the selected rank, and for selecting one or more pre-coding matrices which maximize the second capacity metric;

a channel quality indicator estimation block for computing a third capacity metric from the second capacity metric, selected rank and selected one or more pre-coding matrices for each transmission layer within each frequency channel, and for selecting one or more frequency channels which maximize the third capacity metric; wherein

the receiver is configured to transmit the selected rank, selected one or more pre-coding matrices and selected one or more frequency channels to the transmitter to dynamically optimizing transmission capacity between the transmitter and the receiver.

9. A receiver according to claim 8 , wherein the SINR calculation block computes the SINR metric by computing the SINR for each sub-band from signal power estimates and noise power estimates.

10. A receiver according to claim 8 , wherein the SINR calculation block computes the SINR metric from channel estimates of the frequency channels.

11. A receiver according to claim 10 , wherein the SINR calculation block uses a time-domain average of a plurality of channel estimates to compute the SINR metric.

12. A receiver according to claim 10 wherein the SINR calculation block uses a frequency-domain sampling of a plurality of channel estimates to compute the SINR metric.

13. A receiver according to claim 9 , wherein the SINR calculation block computes the SINR metric from channel estimates of the frequency channels.

14. A receiver according to claim 11 wherein the SINR calculation block uses a frequency-domain sampling of a plurality of channel estimates to compute the SINR metric.