Systems and methods for network MIMO

1. A method of enabling network Multiple-Input Multiple-Output (MIMO) among a plurality of Base Stations (BSs) and a Mobile Station (MS), the method comprising:

determining at a first BS of the plurality of BSs that the MS is eligible for MIMO;

sending to the MS an indication of network MIMO, wherein the indication of network MIMO causes the MS to measure Carrier to Interference Ratios (C/Is) based on pilot signals received from the first BS and at least a second BS selected from the plurality of BSs; and

receiving feedback information from the MS, wherein the feedback information comprises at least: an indication that the second BS is eligible for MIMO, the C/Is based on the pilot signals, and a precoding matrix index preferred by the MS.

2. The method of claim 1 , further comprising sending, from the first BS, pilot signals to the MS.

3. The method of claim 1 , wherein the indication of network MIMO further causes the MS to determine whether the MS is ready to receive a network MIMO transmission.

4. The method of claim 3 , wherein the determination of whether the MS is ready to receive the network MIMO transmission is based upon at least one of: an absolute C/I threshold, a difference in the C/Is between the first of the plurality of BSs and the second of the plurality of BSs that is eligible for MIMO, instantaneous channel conditions, and the structure of the MS.

5. The method of claim 1 , wherein the feedback information comprises an identification of a network MIMO group comprising the first of the plurality of BSs and the second of the plurality of BSs that is eligible for MIMO.

6. The method of claim 5 , further comprising configuring a network MIMO zone based on the identification of the network MIMO group, the network MIMO zone being defined by resources allocated for one of master transmission under control of the first BS or slave transmission under control of the second BS eligible for MIMO.

7. A base station (BS) in a Multiple-Input Multiple-Output (MIMO) system for enabling network MIMO among a plurality of BSs and at least one mobile station (MS), the BS comprising:

at least one transmitting antenna; and

a control system configured to:

determine that the MS is eligible for MIMO;

send to the MS an indication of network MIMO, wherein the indication of network MIMO causes the MS to measure Carrier to Interference Ratios (C/Is) based on pilot signals received from the BS and at least a second BS selected from the plurality of BSs; and

receive feedback information from the MS, wherein the feedback information comprises at least: an indication that the second BS is eligible for MIMO, the C/Is based on the pilot signals, and a precoding matrix index preferred by the MS.

8. The BS of claim 7 , wherein the control system is further configured to send, from the BS, pilot signals to the MS.

9. The BS of claim 7 , wherein the indication of network MIMO further causes the MS to determine whether the MS is ready to receive a network MIMO transmission.

10. The BS of claim 9 , wherein the determination of whether the MS is ready to receive the network MIMO transmission is based upon at least one of an absolute C/I threshold, a difference in the C/Is between the BS and the second of the plurality of BSs that is eligible for MIMO, instantaneous channel conditions, and the structure of the MS.

11. The BS of claim 7 , wherein the feedback information comprises an identification of a network MIMO group comprising the BS and the second of the plurality of BSs that is eligible for MIMO.

12. The BS of claim 11 , wherein the control system is further configured to configure a network MIMO zone based on the identification of the network MIMO group, the network MIMO zone being defined by resources allocated for one of master transmission under control of the first BS or slave transmission under control of the second BS eligible for MIMO.

13. The BS of claim of claim 7 , wherein the control system sends to the second BS a second indication of network MIMO upon determining that the feedback information from the MS indicates that the second BS is eligible for MIMO.

14. The method of claim 1 , further comprising the first BS sending to the second BS a second indication of network MIMO upon determining that the feedback information from the MS indicates that the second BS is eligible for MIMO.

15. The method of claim 14 , further comprising the first BS receiving an acknowledgement (ACK) signal or a negative ACK (NACK) signal from the second BS responsive to sending the second indication, the ACK signal comprising an indication to participate in network MIMO and the NACK signal comprising an indication not to participate in network MIMO.

16. The method of claim 15 , further comprising the first BS sending scheduling information to the second BS responsive to receiving the ACK signal, wherein the scheduling information is used by the first and second BSs to coordinate MIMO transmissions with the MS.

17. The method of claim 16 , wherein the scheduling information comprises at least one of: a set of resources allocated for network MIMO transmission with the MS, a modulation and coding scheme (MCS), and a MIMO mode.

18. The method of claim 15 , further comprising the first BS changing a MIMO mode responsive to receiving the NACK signal from the second BS, the MIMO mode being changed to a space-time transmit diversity (STTD) type of MIMO transmission for communications with the MS.

19. The method of claim 2 , wherein the pilot signals sent to the MS are orthogonal for the first BS and the second BS.

20. The method of claim 1 , wherein the feedback information further comprises a rank indicating streams for receiving data by the MS.