CQI definition for transmission mode 9 in LTE-advanced

1. A method, comprising:

receiving at a base station a Sounding Reference Signal (SRS) having Precoder Matrix Indicator (PMI) reporting disabled;

estimating at the base station a channel between the base station and a wireless station for link adaptation of a downlink signal in Transmission Mode 9 (TM9) based on the received SRS;

transmitting from the base station to the wireless station the downlink signal in the TM9 based on the estimated channel using a predetermined single antenna port if a value of a number of Channel State Information-Reference Signal (CSI-RS) antenna ports equals one; and

transmitting from the base station to the wireless station the downlink signals in the TM9 based on the estimated channel using spatial multiplexing based on a rank-1 precoder determined from a wideband channel covariance matrix R if the number of CSI-RS antenna ports does not equal one or two.

2. The method according to claim 1 , further comprising transmitting from the base station to the wireless station the downlink signals in the TM9 based on the estimated channel using transmit diversity if the number of CSI-RS antenna ports equals two.

3. The method according to claim 2 , wherein the predetermined single antenna port is defined to be port 15 .

4. The method according to claim 3 , wherein the wideband channel covariance matrix R comprises

R =Mean_over — i ( H i T ·H i )

in which H i is a downlink full channel matrix for an ith subcarrier, and H i T is the transpose of H i .

5. The method according to claim 4 , wherein a receiver at a physical layer of the base station receives the SRS from the wireless station, and

wherein a transmitter at the physical layer of the base station transmits the downlink signals from the base station to the wireless station.

6. The method according to claim 5 , wherein the base station comprises an evolved Node B (eNB) in a 3GPP LTE-based network, and

wherein the wireless station comprises a User Equipment (UE) device.

7. A node, comprising:

a physical-layer receiver capable of receiving a Sounding Reference Signal (SRS) in an uplink signal from a wireless station configured to have Precoder Matrix Indicator (PMI) reporting disabled; and

an estimator coupled to the physical-layer receiver and capable of estimating a channel between the node and a wireless station for link adaptation for a downlink signal in Transmission Mode 9 (TM9) based on the received SRS, in which:

if a value of a number of Channel State Information-Reference Signal (CSI-RS) antenna ports equals one, the node will transmit to the wireless station the downlink signal in the TM9 based on the estimated channel using a predetermined single antenna port, and

if the value of the number of CSI-RS antenna ports does not equal one or two, then the node will transmit to the wireless station the downlink signal in the TM9 based on the estimated channel using spatial multiplexing based on a rank-1 precoder that is determined from a wideband channel covariance matrix R.

8. The node according to claim 7 , further comprising a transmitter capable of transmitting to the wireless station the downlink signal in the TM9 based on the estimated channel using the predetermined single antenna port if the value of the number of CSI-RS antenna ports equals one.

9. The node according to claim 8 , wherein if the value the number of CSI-RS antenna ports equals two, then the node will transmit to the wireless station the downlink signal in the TM9 based on the estimated channel using transmit diversity, and

wherein the transmitter is further capable of transmitting to the wireless station the downlink signal TM9 based on the estimated channel using the transmit diversity if the number of CSI-RS antenna ports equals two.

10. The node according to claim 9 , wherein the transmitter is further capable of transmitting to the wireless station the downlink signal in TM9 based on the estimated channel using spatial multiplexing based on the rank-1 precoder that is determined from the wideband channel covariance matrix R if the number of CSI-RS antenna ports does not equal one or two.

11. The node according to claim 10 , wherein the predetermined single antenna port is defined to be port 15 .

12. The node according to claim 11 , wherein a wideband channel covariance matrix R comprises

R =mean_over — i ( H i T ·H i )

in which H i is the downlink full channel matrix for an ith subcarrier, and H i T is the transpose of H i .

13. The node according to claim 12 , wherein the node comprises an evolved Node B (eNB) in a 3GPP LTE-based network, and

wherein the wireless station comprises a User Equipment (UE) device.

14. The node according to claim 7 , wherein the node comprises an evolved Node B (eNB) in a 3GPP LTE-based network, and

wherein the wireless station comprises a User Equipment (UE) device.

15. A node, comprising:

a physical-layer receiver capable of receiving in an uplink signal from a wireless station a Sounding Reference Signal (SRS), the wireless station configured to have Precoder Matrix Indicator (PMI) reporting disabled;

an estimator coupled to the physical-layer receiver and capable of estimating a channel between the node and the wireless station for link adaptation of a downlink signal in Transmission Mode 9 (TM9) based on the received SRS, in which if a value if a number of Channel State Information-Reference Signal (CSI-RS) antenna ports equals one, the node will transmit to the wireless station the downlink signal in the TM9 based on the estimated channel using a predetermined single antenna port, and

if the number of CSI-RS antenna ports does not equal one or two, then the node will transmit to the wireless station the downlink signal in the TM9 based on the estimated channel using spatial multiplexing based on a rank-1 precoder that is determined from a wideband channel covariance matrix R; and

a transmitter capable of transmitting to the wireless station the downlink signal in the TM9 based on the estimated channel using the predetermined single antenna port if the value of the number of CSI-RS antenna ports equals one.

16. The node according to claim 15 , wherein if the number of CSI-RS antenna ports equals two, then the node will transmit to the wireless station the downlink signal in the TM9 based on the estimated channel using transmit diversity, and the transmitter is further capable of transmitting to the wireless station the downlink signal in TM9 based on the estimated channel using transmit diversity if the number of CSI-RS antenna ports equals two, and

Wherein the transmitter is further capable of transmitting to the wireless station the downlink signal in TM9 based on the estimated channel using spatial multiplexing based on a rank-1 precoder that is determined from the wideband channel covariance matrix R if the number of CSI-RS antenna ports does not equal one or two.

17. The node according to claim 16 , wherein the node comprises an evolved Node B (eNB) in a 3GPP LTE-based network, and

wherein the wireless station comprises a User Equipment (UE) device.