Feedback and scheduling for coordinated multi-point (CoMP) joint transmission (JT) in orthogonal frequency division multiple access (OFDMA)

1. A method implemented in a user equipment (UE) used in an orthogonal frequency division multiple access (OFDMA) wireless communications system supporting coordinated multi-point (CoMP) joint transmission (JT), the method comprising:

measuring reference signal received power (RSRP);

transmitting, to a network, first feedback on the RSRP;

receiving, from the network, a CoMP measurement set;

conducting pre-scheduling CoMP UE fallback according to the CoMP measurement set;

computing channel quality and direction information according to a UE category; and

transmitting, to the network, second feedback on the channel quality and direction information,

wherein the pre-scheduling CoMP UE fallback comprises:

measuring a CoMP aggregated signal-to-interference-plus-noise ratio (SINR) or channel quality index (CQI); and

falling back from a CoMP UE to a non-CoMP UE if a total rate based on the measured CoMP aggregated SINR or CQI has no gain over a total rate based on a single-cell per point SINR or CQI, and

wherein the second feedback includes

a rank-1 precoding matrix index (PMI) for each transmission point (TP) in the CoMP measurement set,

an aggregate channel quality index (CQI) computed assuming single user (SU) JT hypothesis and including interference only from TPs outside the CoMP measurement set,

a fallback CQI assuming SU transmission from a fallback serving TP and including interference from other TPs other, and

inter-point phase information for coherent joint transmission.

2. The method as in claim 1 , wherein the second feedback includes at least one of a channel quality index (CQI), a precoding matrix index (PMI), and a rank index (RI).

3. The method as in claim 1 , wherein the UE category includes a CoMP UE and a non-CoMP UE.

4. A method implemented in an network used in an orthogonal frequency division multiple access (OFDMA) wireless communications system supporting coordinated multi-point (CoMP) joint transmission (JT), the method comprising:

receiving, from a user equipment (UE), first feedback on reference signal received power (RSRP);

determining a CoMP measurement set according to the first feedback;

transmitting, to the UE, the CoMP measurement set;

receiving, from the UE, second feedback on channel quality and direction information; and

scheduling CoMP JT according to the second feedback,

wherein the UE conducts pre-scheduling CoMP UE fallback according to the CoMP measurement set, and

wherein the pre-scheduling CoMP UE fallback comprises:

measuring a CoMP aggregated signal-to-interference-plus-noise ratio (SINR) or channel quality index (CQI); and

falling back from a CoMP UE to a non-CoMP UE if a total rate based on the measured CoMP aggregated SINR or CQI has no gain over a total rate based on a single-cell per point SINR or CQI, and

wherein the second feedback includes

a rank-1 precoding matrix index (PMI) for each transmission point (TP) in the CoMP measurement set,

an aggregate channel quality index (CQI) computed assuming single user (SU) JT hypothesis and including interference only from TPs outside the CoMP measurement set,

a fallback CQI assuming SU transmission from a fallback serving TP and including interference from other TPs other, and

inter-point phase information for coherent joint transmission.

5. The method as in claim 4 , wherein the scheduling outputs at least one of CoMP UE allocation, a CoMP cooperating set, and a transmission format.

6. The method as in claim 4 , wherein the second feedback includes at least one of a channel quality index (CQI), a precoding matrix index (PMI), and a rank index (RI).

7. The method as in claim 4 , wherein the network comprises a base station.

8. A method implemented in an orthogonal frequency division multiple access (OFDMA) wireless communications system supporting coordinated multi-point (CoMP) joint transmission (JT), the method comprising:

measuring reference signal received power (RSRP);

transmitting, from a user equipment (UE) to a network, first feedback on the RSRP;

determining a CoMP measurement set according to the first feedback;

transmitting, from the network to the UE, the CoMP measurement set;

conducting pre-scheduling CoMP UE fallback according to the CoMP measurement set;

computing channel quality and direction information according to a UE category;

transmitting, from the UE to the network, second feedback on channel quality and direction information; and

scheduling CoMP JT according to the second feedback,

wherein the pre-scheduling CoMP UE fallback comprises:

measuring a CoMP aggregated signal-to-interference-plus-noise ratio (SINR) or channel quality index (CQI); and

falling back from a CoMP UE to a non-CoMP UE if a total rate based on the measured CoMP aggregated SINR or CQI has no gain over a total rate based on a single-cell per point SINR or CQI, and

wherein the second feedback includes

a rank-1 precoding matrix index (PMI) for each transmission point (TP) in the CoMP measurement set,

an aggregate channel quality index (CQI) computed assuming single user (SU) JT hypothesis and including interference only from TPs outside the CoMP measurement set,

a fallback CQI assuming SU transmission from a fallback serving TP and including interference from other TPs other, and

inter-point phase information for coherent joint transmission.

9. The method as in claim 8 , wherein the second feedback includes at least one of a channel quality index (CQI), a precoding matrix index (PMI), and a rank index (RI).

10. The method as in claim 8 , wherein the UE category includes a CoMP UE and a non-CoMP UE.

11. The method as in claim 8 , wherein the scheduling outputs at least one of CoMP UE allocation, a CoMP cooperating set, and a transmission format.

12. The method as in claim 8 , wherein the network comprises a base station.