Methods and apparatus to provide fairness for wireless local area networks that use extended physical layer protection mechanisms

Abstract

Methods and apparatus to provide fairness for wireless local area networks that use extended physical layer (a.k.a. PHY) protection mechanisms are disclosed. A disclosed example method comprises choosing a length field value for a frame header such that, when a transmit operation is ended, a legacy wireless station and a non-legacy wireless station of a wireless local area network are able to start contending for a wireless medium at substantially a same instant, and sending a frame across the wireless medium that includes the frame header.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example wireless local area network (WLAN) with an access point and a plurality of wireless stations constructed in accordance with the teachings of the invention.

FIG. 2 illustrates an example manner of implementing an example access point and/or an example wireless station of FIG. 1.

FIG. 3 illustrates an example manner of implementing the example medium access controller of FIG. 2.

FIGS. 4A and 4B illustrate an example frame data structure.

FIGS. 5, 6, 7 and 8 illustrate example extended physical layer (a.k.a. PHY) protection scenarios for the example WLAN of FIG. 1.

FIGS. 9, 10 and 11 are flowcharts representative of example machine accessible instructions that may be executed to implement an example access point and/or an example wireless stations of FIG. 1.

Claims

1. A method comprising: choosing a length field value for a frame header such that, when a transmit operation is ended, a legacy wireless station and a non-legacy wireless station of a wireless local area network are able to start contending for a wireless medium at substantially a same instant; andsending a frame across the wireless medium that includes the frame header.

2. A method as defined in claim 1, wherein the frame is a physical layer convergence protocol (PLCP) frame comprising a PLCP header, the PLCP header comprising a legacy signal field that includes the length field value.

3. (canceled)

4. A method as defined in claim 2, wherein at least a portion of the PLCP header is decodable by substantially all nodes of the wireless local area network.

5. A method as defined in claim 1, wherein the frame is a request-to-send frame, and the transmit operation is ended when a clear-to-send frame timeout occurs.

6. A method as defined in claim 5, choosing the length field value comprises: computing a sum of a clear-to-send timeout duration and a distributed inter-frame space;computing a difference of the sum and an extended inter-frame space; andadding the difference to a transmit duration for a body of the frame.

7. A method as defined in claim 1, wherein the frame is a first of one or more frames, and the transmit operation is ended when a last of the one or more frames is acknowledged.

8. A method as defined in claim 7, wherein choosing the length field value comprises setting the length field value to a medium access control duration.

9. (canceled)

10. A method as defined in claim 7, wherein choosing the length field value comprises: computing a difference of an extended inter-frame space and a distributed inter-frame space; andsubtracting the difference from a medium access control duration.

11. (canceled)

12. A method as defined in claim 7, further comprising setting a medium access control duration to a value that is different than a time required to transmit the one or more frames and receive response frame.

13. A method as defined in claim 7, further comprising: waiting to receive a block acknowledge frame;waiting a time duration that is at least as long as a short inter-frame spacing after receiving the block acknowledge frame; andsending a contention-free end frame.

14. A wireless network device comprising: a wireless modem to transmit a frame via a wireless medium of a wireless network; anda medium access controller to form the frame, the frame comprising a physical layer convergence protocol (PLCP) header, the PLCP header comprising a legacy signal field that includes a length field value chosen such that, when a transmit operation ends, a legacy wireless station and a non-legacy wireless station of the wireless local area network are permitted to contend for the wireless medium at substantially a same instant.

15. A wireless network device as defined in claim 14, wherein the medium access controller comprises: an extended physical protection controller to choose the length field value;a header generator to generate the PLCP header; anda frame generator to form the frame.

16. A wireless network device as defined in claim 14, wherein wireless modem transmits the frame in accordance with at least one of a past or legacy standard.

17. A wireless network device as defined in claim 14, wherein the frame is a request-to-send frame, and the transmit operation is ended when a clear-to-send frame timeout occurs.

18. (canceled)

19. A wireless network device as defined in claim 14, wherein the frame is a first of one or more frames, and the transmit operation is ended when a last of the one or more frames is acknowledged.

20. A wireless network device as defined in claim 19, wherein the medium access controller chooses the length field value by setting the length field value to a medium access control duration.

21. (canceled)

22. An article of manufacture storing machine accessible instructions which, when executed, cause a machine to: choose a length field value for a frame header such that, when a transmit operation is ended, a legacy wireless station and a non-legacy wireless station of a wireless local area network are able to start contending for a wireless medium at substantially a same instant; andsend a frame across the wireless medium that includes the frame header.

23. An article of manufacture as defined in claim 22, wherein the machine accessible instructions, when executed, cause the machine to form the frame as a physical layer convergence protocol (PLCP) frame comprising a PLCP header, the PLCP header comprising a legacy signal field that includes the length field value.

24. An article of manufacture as defined in claim 22, wherein the frame is a request-to-send frame, and the transmit operation is ended when a clear-to-send frame timeout occurs, and wherein the machine accessible instructions, when executed, cause the machine to choose the length field value by: computing a sum of a clear-to-send timeout duration and a distributed inter-frame space;computing a difference of the sum and an extended inter-frame space; andadding the difference to a transmit duration for a body of the frame.

25. An article of manufacture as defined in claim 22, wherein the frame is a first of one or more frames, and the transmit operation is ended when a last of the one or more frames is acknowledged.

26-34. (canceled)