Wireless rate adaptation

1. A computer-implemented method of adapting wireless transmission rates of frames in a computer network, comprising the steps of:

determining, by a computer, at least a short-term loss ratio for wireless communication of frames in the computer network during a window of time; and

adapting a transmission rate responsive to at least the short-term loss ratio of frames, a maximum tolerable loss threshold for the communication during the window, and an opportunistic rate increase threshold for the communication during the window, the maximum tolerable loss threshold based on a critical loss threshold wherein losses at a current level result in throughput equal to substantially lossless transmission at a lower level;

wherein a size of the window, the maximum tolerable loss threshold, and the opportunistic rate increase threshold are responsive to the transmission rate used for the communication.

2. A method as in claim 1 , wherein the short-term loss ratio is a loss ratio determined over tens of milliseconds to a few seconds.

3. A method as in claim 1 , wherein the window is re-started if the transmission rate changes.

4. A method as in claim 1 , wherein the communication uses packets of different sizes, the sizes are divided into groups, and the determining and adapting steps are performed for each of the groups.

5. A method as in claim 1 , wherein a frame count is used to represent the short-term loss ratio, the maximum tolerable loss threshold, and the opportunistic rate increase threshold.

6. A method as in claim 1 , further comprising the step of:

initially turning off RTS/CTS (Request-to-Send/Clear-to-Send) messages;

detecting a frame loss while the RTS/CTS messages are turned off;

responsive to the detected frame loss, gradually increasing the use RTS/CTS messages during an RTS/CTS window; and

responsive to a reduction in detecting frame loss, gradually reducing the use of RTS/CTS messages or turning off the RTS/CTS messages.

7. A method as in claim 6 , wherein the size of the RTS/CTS window is measured in frames.

8. A method as in claim 7 , wherein the RTS/CTS window is increased in size if successful communication does not occur in a frame when the RTS/CTS messages are not being used.

9. A method as in claim 7 , wherein the RTS/CTS window is halved in size if successful communication does not occur in a frame when the RTS/CTS messages are being used, or if successful communication does occur when the RTS/CTS messages are not being used.

10. A method as in claim 7 , wherein the RTS/CTS window stays a same size if successful communication does occur when the RTS/CTS messages are being used.

11. A method as in claim 7 , wherein determination of the short-term loss ratio does not count frames that have the RTS/CTS messages and that fail to be communicated.

12. A system that adapts wireless transmission rates of frames in a computer network, comprising:

a processor;

a memory, comprising:

a loss estimation module that determines at least a short-term loss ratio for wireless communication of frames in the computer network during a window of time; and

a rate change module that adapts a transmission rate responsive to at least the short-term loss ratio of frames, a maximum tolerable loss threshold for the communication during the window, and an opportunistic rate increase threshold for the communication during the window, the maximum tolerable loss threshold based on a critical loss threshold wherein losses at a current level result in throughput equal to substantially lossless transmission at a lower level;

wherein a size of the window, the maximum tolerable loss threshold, and the opportunistic rate increase threshold are responsive to the transmission rate used for the communication.

13. A system as in claim 12 , wherein the short-term loss ratio is a loss ratio determined over tens of milliseconds to a few seconds.

14. A system as in claim 12 , wherein the window is re-started if the transmission rate changes.

15. A system as in claim 12 , wherein the communication uses packets of different sizes, the sizes are divided into groups, and the determining and adapting steps are performed for each of the groups.

16. A system as in claim 12 , wherein a frame count is used to represent the short-term loss ratio, the maximum tolerable loss threshold, and the opportunistic rate increase threshold.

17. A system as in claim 12 , further comprising an adaptive RTS/CTS filter that uses RTS/CTS messages during an RTS/CTS window.

18. A system as in claim 17 , wherein the size of the RTS/CTS window is measured in frames.

19. The method of claim 1 , further comprising:

dividing packets into a plurality of groups as determined by size, wherein the transmission rate of a first group is adapted independently of a transmission rate for a second group.

20. The method of claim 1 , further comprising:

detecting a an RTS/CTS signal from a chipset; and

overriding the RTS/CTS signal of the chipset when a threshold number of collisions are detected.

21. A computer-implemented method of selectively adapting wireless transmission rates of frames in a computer network, comprising the steps of:

determining whether frames are being lost due to channel characteristics or due to a failure of RTS/CTS (Request-to-Send/Clear-to-Send) messages to resolve collisions;

responsive to determining that frames are being lost due to channel characteristics, adapting the transmission rate, comprising the steps of:

determining, by a computer, at least a short-term loss ratio for wireless communication of frames in the computer network during a window of time; and

adapting a transmission rate responsive to at least the short-term loss ratio of frames, a maximum tolerable loss threshold for the communication during the window, and an opportunistic rate increase threshold for the communication during the window,

wherein a size of the window, the maximum tolerable loss threshold, and the opportunistic rate increase threshold are responsive to the transmission rate used for the communication; and

responsive to determining that frames are being lost due to the failure of RTS/CTS messages, performing a different action.

22. The method of claim 21 , wherein determining whether frames are being lost due to channel characteristics or due to a failure of RTS/CTS messages to resolve collisions comprises:

receiving timestamps from a PHY layer of transmission for frames;

comparing the timestamps to a transmission time predicted if no frames with RTS/CTS messages are present.