Providing CQI feedback to a transmitter station in a closed-loop MIMO system

1. A method comprising:

measuring, at a receiver station, channel qualities associated with receiving signals from a transmitter station for a first and a second spatial channel, the transmitter and receiver stations employing a closed-loop multiple-input multiple-output (MIMO) system;

selecting a first modulation coding scheme (MCS) entry among a plurality of ordered MCS entries, the first MCS entry identifying a first MCS for use by the transmitter station to transmit signals to the receiver station;

selecting, among the plurality of ordered MCS entries, a subset of lower ordered MCS entries relative to the first MCS entry;

selecting a second MCS entry from one of the selected subset of lower ordered MCS entries, the second MCS entry identifying a second MCS for use by the transmitter station to transmit signals to the receiver station;

determining a first channel Quality indicator (CQI) and a second CQI based at least in part on the measured channel qualities, wherein the first CQI directly indexes the first MCS entry in the ordered MCS entries, and the second CQI indirectly indexes the second MCS in the ordered MCS entries by indexing an MCS entry within the selected subset of lower ordered MCS entries relative to the indexed first MCS entry; and

transmitting from the receiver station to the transmitter station the first and the second CQI.

2. The method of claim 1 wherein the selected subset of lower ordered MCS entries are a selected subset of continuous lower ordered MCS entries.

3. The method of claim 1 ,

wherein the selected subset is a selected subset of non-continuous lower ordered MCS entries having at least two successively lower ordered MCS entries that are not immediately successive.

4. The method of claim 1 further comprising pre determining by the receiver station the selected subset of lower ordered MCS entries.

5. The method of claim 4 , further comprising the receiver station providing the pre-determined selected subset of lower ordered MCS entries to the transmitter station.

6. The method of claim 4 , wherein the pre-determining comprises:

generating an MCS probability density distribution for a second exemplary spatial channel given a MCS entry of a first exemplary spatial channel;

pre-determining the selected subset of lower ordered MCS entries based at least in part on the generated MCS probability density distribution.

7. The method of claim 1 , further comprising transmitting from the receiver station to the transmitter station a third CQI to indirectly identify a third MCS entry among the ordered MCS entries, the third MCS entry being a lower ordered MCS than the second MCS entry.

8. The method of claim 1 , wherein the first CQI and the second CQI are associated with the first and the second spatial channel, respectively, and the method further comprising transmitting from the receiver station to the transmitter station a first and a second beamforming vector for the first and the second spatial channels, respectively, the first and the second beamforming vectors transmitted in order to indicate to the transmitter station order of the first and the second CQI.

9. The method of claim 8 , wherein the first and the second beamforming vectors are transmitted to the transmitter station to indicate to the transmitter station that the first CQI is associated with the first spatial channel that is a higher quality channel than the second spatial channel associated with the second CQI.

10. An apparatus comprising:

one or more monitors to measure channel qualities associated with the apparatus receiving signals from a transmitter station for a first and a second spatial channel, the apparatus and the transmitter station employing a closed-loop multiple-input multiple-output (MIMO) system;

a controller coupled to the one or more monitors, and configured to:

select a first modulation coding scheme (MCS) entry among a plurality of ordered MCS entries, the first MCS entry identifying a first MCS for use by the transmitter station to transmit signals to the receiver station;

select, among the plurality of ordered MCS entries, a subset of lower ordered MCS entries relative to the first MCS entry;

select a second MCS entry from one of the selected subset of lower ordered MCS entries, the second MCS entry identifying a second MCS for use by the transmitter station to transmit signals to the receiver station; and

determine a first and a second channel quality indicator (CQI) based at least in part on the measured channel qualities, wherein the first CQI directly indexes the first MCS entry in the ordered MCS entries, and the second CQI indirectly indexes the second MCS in the ordered MCS entries by indexing an MCS entry within the selected subset of lower ordered MCS entries relative to the indexed first MCS entry; and

a transmitter configured to transmit to the transmitter station the first and the second CQI.

11. The apparatus of claim 10 , wherein the controller is further adapted to pre-determine the selected subset of lower ordered MCS entries.

12. The apparatus of claim 11 , wherein the controller is further adapted to prompt the apparatus to provide the pre-determined selected subset of lower ordered MCS entries to the transmitter station.

13. The apparatus of claim 11 , wherein the controller is further adapted to said pre-determine the selected subset of lower ordered MCS entries by generating an MCS probability density distribution for a second spatial channel given a first spatial channel.

14. The apparatus of claim 10 , wherein the controller is adapted to determine a third CQI to indirectly identify a third MCS entry among the ordered MCS entries, the third MCS entry being a lower ordered MCS than the second MCS entry.

15. A system comprising:

a plurality of omnidirectional antennas;

a processor; and

a communication chipset coupled to the antennas and the processor, and configured to:

receive data signals from a transmitter station;

measure channel qualities associated with the received data signals;

select a first modulation coding scheme (MCS) entry among a plurality of ordered MCS entries, the first MCS entry correspondingly identifying a first MCS for use by the transmitter station to transmit signals to the receiver station;

select, among the plurality of ordered MCS entries, a subset of lower ordered MCS entries relative to the first MCS entry;

select a second MCS entry from one of the selected subset of lower ordered MCS entries, the second MCS entry correspondingly identifying a second MCS for use by the transmitter station to transmit signals to the receiver station;

determine a first and a second channel quality indicator (CQI) based at least in part on the measured channel qualities, wherein the first CQI directly indexes the first MCS entry in the ordered MCS entries, and the second CQI indirectly indexes the second MCS in the ordered MCS entries by indexing an MCS entry within the selected subset of lower ordered MCS entries relative to the indexed first MCS entry; and

transmit to the transmitter station the first and the second CQI.

16. The system of claim 15 , wherein the plurality of antennas are designed to communicate in a wireless metropolitan area network (WMAN).

17. The system of claim 15 , wherein the system is one selected from the group consisting of a desktop computer, a laptop computer, a set-top box, a personal digital assistant (PDA), a web tablet, a pager, a text messenger, a game device, a smart appliance, or a wireless mobile phone.

18. The method of claim 1 , wherein the plurality of ordered MCS entries are ordered based at least in part on associated channel quality levels, such that a relatively higher ordered MCS entry is associated with a relatively higher channel quality level compared to a relatively lower ordered MCS entry that is associated with a relatively lower channel quality level.