Interference cancellation

1. A method implemented in an access point (AP) used in a wireless communications system including a first uplink (UL) client device, a second UL client device, a first downlink (DL) client device, and a second DL client device, the method comprising:

transmitting a first pilot signal to the first and second DL client devices;

receiving second pilot signals from the first and second UL client devices;

estimating, according to the second pilot signals, channels H 01 U between the AP and the first UL client device and H 02 U between the AP and the second UL client device;

receiving, from the first DL client device, feedback DL channel state information (CSI) H 10 D between the first DL client device and the AP and, from the second DL client device, feedback DL CSI H 20 D between the second DL client device and the AP;

receiving first UL-DL CSI from the first DL client device and second UL-DL CSI from the second DL client device; and

transmitting first precoder V 1 to the first UL client device;

wherein the first and second UL client devices and the first and second DL client devices receive first precoder V 1 , wherein the second UL client device determines second precoder V 2 for the second UL client device, and wherein the first and second DL client devices determine first receive filter U 1 for the first DL client device and second receive filter U 2 for the second DL client device, respectively, along with second precoder V 2 by using first precoder V 1 ;

determining precoder V o for the AP to maximize DL stream rate of N downlink streams, wherein the DL stream rate is expressed as

R DL comprising Rate ( U 1 H 10 D V 1 ) and Rate ( U 2 H 20 D V 2 ),

where V 1 and V 2 are two N×N/2 precoding matrices for the first and second DL client devices and form N×N precoder V 0 =[V 1 V 2 ].

2. The method as in claim 1 , wherein the first and second UL clients and the first and second DL clients work in a half duplex mode, and the AP works in a full duplex mode.

3. The method as in claim 1 , wherein the first UL-DL CSI comprises: H 11 between the first DL client device and the first UL client device and H 12 between the first DL client device and the second UL client device, and wherein the second UL-DL CSI comprises: H 21 between the second DL client device and the first UL client device and H 22 between the second DL client device and the second UL client device.

4. The method as in claim 1 , wherein the first UL-DL CSI comprises a first composite channel matrix, and the second UL-DL CSI comprises a second composite channel matrix.

5. The method as in claim 4 , wherein the first composite channel matrix comprises H 12 −1 H 11 , where H 11 is a channel matrix between the first DL client device and the first UL client device and H 12 is a channel matrix between the first DL client device and the second UL client device, and wherein the second composite channel matrix comprises H 21 −1 H 22 , where H 21 is a channel matrix between the second DL client device and the first UL client device and H 22 is a channel matrix between the second DL client device and the second UL client device.

6. The method as in claim 1 , further comprising: determining precoder V 0 for the AP, first precoder V 1 for the first UL client device, second precoder V 2 for the second UL client device, receive filter U 0 for the AP, first receive filter U 1 for the first DL client device, and second receive filter U 2 for the second DL client device.

7. The method as in claim 6 , wherein a decision is made according to channels H 01 U and H 02 U , feedback DL CSI H 10 D and feedback DL CSI H 20 D , and first UL-DL CSI and second UL-DL CSI.

8. The method as in claim 1 , further comprising: transmitting second precoder V 2 to the second UL client device.

9. The method as in claim 8 , wherein the first and second DL client devices receive first precoder V 1 and second precoder V 2 , and wherein the first and second DL client devices determine first receive filter U 1 for the first DL client device and second receive filter U 2 for the second DL client device, respectively, by using first precoder V 1 and second precoder V 2 .

10. In a wireless communications system including a first uplink (UL) client device, a second UL client device, a first downlink (DL) client device, a second DL client device, and an access point (AP), a method implemented in the second UL client device, the method comprising:

transmitting a second pilot signal to the AP, wherein the AP transmits a first pilot signal to the first and second DL client devices, receives another second pilot signal from the first UL client device, estimates, according to the second pilot signals, channels H 01 U between the AP and the first UL client device and H 02 U between the AP and the second UL client device, receives from the first DL client device, feedback DL channel state information (CSI) H 10 D between the first DL client device and the AP and, from the second DL client device, feedback DL CSI H 20 D between the second DL client device and the AP, receives first UL-DL CSI from the first DL client device and second UL-DL CSI from the second DL client device, and transmits first precoder V 1 to the first UL client device;

wherein the first and second UL client devices and the first and second DL client devices receive first precoder V 1 , wherein the second UL client device determines second precoder V 2 for the second UL client device, and wherein the first and second DL client devices determine first receive filter U 1 for the first DL client device and second receive filter U 2 for the second DL client device, respectively, along with second precoder V 2 by using first precoder V 1 ;

determining precoder V o for the AP to maximize DL stream rate of N downlink streams, wherein the DL stream rate is expressed as

R DL comprising Rate ( U 1 H 10 D V 1 ) and Rate ( U 2 H 20 D V 2 ),

where V 1 and V 2 are two N×N/2 precoding matrices for the first and second DL client devices and form N×N precoder V 0 =[V 1 V 2 ].

11. In a wireless communications system including a first uplink (UL) client device, a second UL client device, a first downlink (DL) client device, a second DL client device, and an access point (AP), a method implemented in the first DL client device, the method comprising:

receiving a first pilot signal from the AP; transmitting, to the AP, feedback DL channel state information (CSI) H 10 D between the first DL client device and the AP; and transmitting first UL-DL CSI to the AP,

wherein the AP transmits a first pilot signal to the second DL client device, receives second pilot signals from the first and second UL client devices, estimates, according to the second pilot signals, channels H 01 U between the AP and the first UL client device and H 02 U between the AP and the second UL client device, receives, from the second DL client device, feedback DL CSI H 20 D between the second DL client device and the AP, receives second UL-DL CSI from the second DL client device, and transmits first precoder V 1 to the first UL client device;

wherein the first and second UL client devices and the first and second DL client devices receive first precoder V 1 , wherein the second UL client device determines second precoder V 2 for the second UL client device, and wherein the first and second DL client devices determine first receive filter U 1 for the first DL client device and second receive filter U 2 for the second DL client device, respectively, along with second precoder V 2 by using first precoder V 1 ;

determining precoder V o for the AP to maximize DL stream rate of N downlink streams, wherein the DL stream rate is expressed as

R DL comprising Rate ( U 1 H 10 D V 1 ) and Rate ( U 2 H 20 D V 2 ),

where V 1 and V 2 are two N×N/2 precoding matrices for the first and second DL client devices and form N×N precoder V 0 =[V 1 V 2 ].