System and method for interference protection in downlink multi-user multiple-input, multiple-output communication

1. An access point comprising:

a packet generation module configured to generate a multi-user request-to-send packet for transmission to each of N remote nodes,

wherein

the multi-user request-to-send packet includes a plurality of addresses,

each of the plurality of addresses is for a respective one of M of the N remote nodes,

N is an integer greater than one, and

M is an integer (i) less than or equal to N, and (ii) greater than or equal to 1;

a packet detection module configured to detect clear-to-send packets received from ones of the N remote nodes; and

a downlink control module configured to, based on the plurality of addresses, control a downlink to the M of the N remote nodes after M clear-to-send packets are detected respectively from the M of the N remote nodes,

wherein

a transmission of a first one of the clear-to-send packets begins a short interframe space period after receiving the multi-user request-to-send packet,

transmissions of a remainder of the clear-to-send packets are sequential, and

start times of each of the transmissions of the remainder of the clear-to-send packets is based on

a transmission end time of the multi-user request-to-send packet,

the short interframe space period, and

a product of (i) a number of previously transmitted clear-to-send packets, and (ii) a sum of an amount of time to transmit one of the clear-to-send packets and the short interframe space period.

2. The access point of claim 1 , wherein the multi-user request-to-send packet has a variable length.

3. The access point of claim 2 , wherein the variable length is based on M.

4. The access point of claim 1 , wherein the multi-user request-to-send packet has a predetermined length.

5. The access point of claim 4 , wherein the predetermined length is based on N.

6. The access point of claim 1 , wherein N equals four.

7. The access point of claim 1 , wherein each of the transmissions of the remainder of the clear-to-send packets are separated by a sum of the short interframe space period and a transmission time for a clear-to-send packet.

8. The access point of claim 1 , wherein:

the multi-user request-to-send packet includes a duration field; and

the duration field is used to set a network allocation vector for N-M of the N remote nodes.

9. An access point comprising:

a packet generation module configured to generate a multi-user request-to-send packet for transmission to each of N remote nodes,

wherein

the multi-user request-to-send packet includes a plurality of addresses,

each of the plurality of addresses is for a respective one of M of the N remote nodes,

N is an integer greater than one, and

M is an integer (i) less than or equal to N, and (ii) greater than or equal to 1;

a packet detection module configured to detect clear-to-send packets received from ones of the N remote nodes; and

a downlink control module configured to, based on the plurality of addresses, control a downlink to the M of the N remote nodes after M clear-to-send packets are detected respectively from the M of the N remote nodes,

wherein

the multi-user request-to-send packet includes a duration field,

the duration field is used to set a network allocation vector for N-M of the N remote nodes,

the N remote nodes ignore network allocation vector information in the clear-to-send packets transmitted from the M of the N remote nodes for a predetermined period,

the clear-to-send packets are sent by the M of the N nodes during the predetermined period

a transmission of a first one of the clear-to-send packets begins a short interframe space period after receiving the multi-user request-to-send packet,

transmissions of a remainder of the clear-to-send packets are sequential, and

start times of each of the transmissions of the remainder of the clear-to-send packets is based on

a transmission end time of the multi-user request-to-send packet,

the short interframe space period, and

a product of (i) a number of previously transmitted clear-to-send packets, and (ii) a sum of an amount of time to transmit one of the clear-to-send packets and the short interframe space period.

10. The access point of claim 1 , wherein the downlink control module is configured to initiate transmission of data packets to the M of the N remote nodes, respectively, the short interframe space after the M clear-to-send packets are detected.

11. The access point of claim 1 , wherein:

in response to receiving X clear-to-send packets instead of M clear-to-send packets, the downlink control module is configured to initiate transmission of data packets to X of the N remote nodes instead of initiating transmission of data packets to the M of the N remote nodes;

the downlink control module is configured to transmit the data packets to the X of the N remote nodes a predetermined period after the multi-user request-to-send packet was received;

X is a number of clear-to-send packets received during the predetermined period; and

X is an integer greater than zero and less than M.

12. The access point of claim 10 , wherein each of the M of the N remote nodes transmits an acknowledgement packet after receiving a data packet.

13. The access point of claim 12 , wherein:

the downlink control module is configured to initiate transmission of a contention free end packet to each of the N remote nodes after the M acknowledgement packets are received; and

the contention free end packet resets a network allocation vector for each of the N remote nodes.

14. The access point of claim 13 , wherein the downlink control module is configured to initiate transmission of the contention free end packet when zero clear-to-send packets have been received within a predetermined period after the multi-user request-to-send packet was received.

15. The access point of claim 13 , wherein the downlink control module is configured to initiate transmission of the contention free end packet when greater than zero clear-to-send packets and less than M clear-to-send packets have been received within a predetermined period.

16. A method comprising:

generating a multi-user request-to-send packet for transmission to each of N remote nodes,

wherein

the multi-user request-to-send packet includes a plurality of addresses,

each of the plurality of addresses is for a respective one of M of the N remote nodes,

N is an integer greater than one, and

M is an integer (i) less than or equal to N, and (ii) greater than or equal to 1 ;

detecting clear-to-send packets received from ones of the N remote nodes; and

based on the plurality of addresses, controlling a downlink to the M of the N remote nodes after M clear-to-send packets are detected respectively from the M of the N remote nodes,

wherein

a transmission of a first one of the clear-to-send packets begins a short interframe space period after receiving the multi-user request-to-send packet,

transmissions of a remainder of the clear-to-send packets are sequential, and

start times of each of the transmissions of the remainder of the clear-to-send packets is based on

a transmission end time of the multi-user request-to-send packet,

the short interframe space period, and

a product of (i) a number of previously transmitted clear-to-send packets, and (ii) a sum of an amount of time to transmit one of the clear-to-send packets and the short interframe space period.

17. The method of claim 16 , wherein the multi-user request-to-send packet has a variable length.

18. The method of claim 17 , wherein the variable length is based on M.

19. The method of claim 16 , wherein the multi-user request-to-send packet has a predetermined length.

20. The method of claim 19 , wherein the predetermined length is based on N.

21. The method of claim 19 , wherein N equals four.

22. The method of claim 16 , wherein each of the transmissions of the remainder of the clear-to-send packets are separated by a sum of the short interframe space period and a transmission time for a clear-to-send packet.

23. The method of claim 16 , wherein:

the multi-user request-to-send packet includes a duration field; and

the duration field is used to set a network allocation vector for N-M of the N remote nodes.

24. The access point of claim 1 , wherein:

the clear-to-send packets are received at respective time periods and in an order in which the corresponding plurality of addresses were included in the multi-user request-to-send packet; and

consecutive ones of the time periods are separated by respective short interframe space periods.

25. The access point of claim 9 , wherein a length of the predetermined period is based on an amount of time for each of the N remote nodes to send a respective clear-to-send packet.