Systems and methods for channel correlation based user detection in an uplink multi-user transmission of a multiple-input multiple-output network

1. A method for detecting a client station based on channel correlation in an uplink multi-user transmission of a multiple-input multiple-output network, the method comprising:

transmitting, from a wireless access point to a number of client stations, a number of trigger frames to initiate uplink transmission;

receiving, at the wireless access point, a number of uplink data signals via a number of channels from the number of client stations;

determining a channel matrix indicative of channel coefficients corresponding to the number of channels based on the received uplink data signals;

for each client station:

generating a respective correlation indicator based on the channel coefficients,

detecting a respective client station by determining whether the respective client station has transmitted a respective uplink data signal based on respective correlation indicators corresponding to the number of client stations, and

updating the channel matrix by removing columns corresponding to the respective client station when the respective client station has not transmitted a respective uplink data signal; and

using the updated estimated channel matrix for decoding the received number of uplink data signals.

2. The method of claim 1 , wherein the determining the channel matrix indicative of channel coefficients corresponding to the number of channels based on the received uplink data signals comprises:

retrieving a pre-defined matrix based on a total number of spatial streams; and

using the pre-defined matrix to generate the channel matrix comprised of a number of sub-matrices based on the received number of uplink data signals, each of the number of sub-matrices corresponding to a respective channel from the number of channels.

3. The method of claim 1 , wherein the determining the channel matrix indicative of channel coefficients corresponding to the number of channels based on the received uplink data signals comprises:

for each client station from the number of client stations, estimating a respective channel vector based on a respective uplink data signal received from the respective channel; and

combining estimated respective channel vectors for the number of client stations to obtain a joint estimated channel matrix.

4. The method of claim 3 , wherein the generating the respective correlation indicator based on the channel coefficients comprises:

for each column in the joint estimated channel matrix, calculating a respective correlation value between channel coefficients of two neighboring tones.

5. The method of claim 4 , further comprising:

for each client station, generating a respective sum of correlation values corresponding to columns of the joint estimated channel matrix that correspond to the respective client station.

6. The method of claim 5 , further comprising:

retrieving a target receive power value corresponding to the respective client station;

computing a power difference between the retrieved target receive power value and a maximum target receive power value among the number of client stations; and

adding the power difference to the respective sum of correlation values.

7. The method of claim 4 , wherein the calculating of the respective correlation value between channel coefficients of two neighboring tones comprises:

computing a product of a power value corresponding to a respective spatial stream and a sum of correlations for phase-only quantized channel at the respective spatial stream.

8. The method of claim 5 , wherein the determining of whether the respective client station has transmitted the respective uplink data signal based on respective correlation indicators corresponding to the number of client stations comprises:

determining a difference between a maximum sum of correlation values among all client stations and a first sum of correlation values corresponding to a first client station from the number of client stations; and

comparing the difference with a pre-defined threshold.

9. The method of claim 6 , further comprising:

in response to determining that the difference is greater than the pre-defined threshold, updating the joint estimated channel matrix by removing a first channel vector corresponding to the first client station.

10. The method of claim 1 , further comprising:

receiving, at the wireless access point, a number of uplink data signals via a number of resource units from the number of client stations, wherein each client station occupies a respective resource unit;

generating the respective correlation indicator based on the channel coefficients subject to a respective resource unit; and

determining whether the resource unit is available based on respective correlation indicators corresponding to a number of resource units.

11. A system for detecting a client station based on channel correlation in an uplink multi-user transmission of a multiple-input multiple-output network, the system comprising:

a wireless transceiver configured to:

transmit, from a wireless access point to a number of client stations, a number of trigger frames to initiate uplink transmission, and

receive, at the wireless access point, a number of uplink data signals via a number of channels from the number of client stations; and

processing circuitry configured to:

determine a channel matrix indicative of channel coefficients corresponding to the number of channels based on the received uplink data signals;

for each client station:

generate a respective correlation indicator based on the channel coefficients,

detect a respective client station by determining whether the respective client station has transmitted a respective uplink data signal based on respective correlation indicators corresponding to the number of client stations, and

update the channel matrix by removing columns corresponding to the respective client station when the respective client station has not transmitted a respective uplink data signal; and

use the updated joint estimated channel matrix for decoding the received number of uplink data signals.

12. The system of claim 11 , wherein the processing circuitry, when determining the channel matrix indicative of channel coefficients corresponding to the number of channels based on the received uplink data signals, is configured further to:

retrieve a pre-defined matrix based on a number total number of spatial streams; and

use the pre-defined matrix to generate the channel matrix comprised of a number of sub-matrices based on the received number of uplink data signals, each of the number of sub-matrices corresponding to a respective channel from the number of channels.

13. The system of claim 11 , wherein the processing circuitry, when determining the channel matrix indicative of channel coefficients corresponding to the number of channels based on the received uplink data signals, is configured further to:

for each client station from the number of client stations, estimate a respective channel vector based on a respective uplink data signal received from the respective channel; and

combine estimated respective channel vectors for the number of client stations to obtain a joint estimated channel matrix.

14. The system of claim 13 , wherein the processing circuitry, when generating the respective correlation indicator based on the channel coefficients, is configured further to:

for each column in the joint estimated channel matrix, calculate a respective correlation value between channel coefficients of two neighboring tones.

15. The system of claim 14 , wherein the processing circuitry is further configured to:

for each client station, generate a respective sum of correlation values corresponding to columns of the joint estimated channel matrix that correspond to the respective client station.

16. The system of claim 15 , wherein the processing circuitry is further configured to:

retrieve a target receive power value corresponding to the respective client station;

compute a power difference between the retrieved target receive power value and a maximum target receive power value among the number of client stations; and

add the power difference to the respective sum of correlation values.

17. The system of claim 14 , wherein the processing circuitry, when calculating the respective correlation value between the channel coefficients of the two neighboring tones, is further configured to:

compute a product of a power value corresponding to a respective spatial stream and a sum of correlations for phase-only quantized channel at the respective spatial stream.

18. The system of claim 15 , wherein the processing circuitry, when determining whether the respective client station has transmitted the respective uplink data signal based on respective correlation indicators corresponding to the number of client stations, is configured further to:

determine a difference between a maximum sum of correlation values among all client stations and a first sum of correlation values corresponding to a first client station from the number of client stations; and

compare the difference with a pre-defined threshold.

19. The system of claim 16 , wherein the processing circuitry is further configured to:

in response to determining that the difference is greater than the pre-defined threshold, update the joint estimated channel matrix by removing a first channel vector corresponding to the first client station.

20. The system of claim 11 , wherein the processing circuitry is further configured to:

receive, at the wireless access point, a number of uplink data signals via a number of resource units from the number of client stations, wherein each client station occupies a respective resource unit;

generate the respective correlation indicator based on the channel coefficients subject to a respective resource unit; and

determine whether the resource unit is available based on respective correlation indicators corresponding to a number of resource units.