Cooperative wireless communications, such as cooperative medium access control for example

• US 20060077942A1
• Filed: 10/07/2005
• Published: 04/13/2006
• Est. Priority Date: 10/07/2004
• Status: Active Grant

• Current Assignee: Polytechnic University (New York University)
• Original Assignee: Polytechnic University (New York University)
• Inventors: Tao, Zhifeng, Liu, Pei, Panwar, Shivendra S.
• Granted Patent: US 7,330,457 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04L 45/121 by minimising delays
• CPC Class Codes: H04W 40/00 Communication routing or communication path finding
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

When it is advantageous to do so, a wireless LAN station sends data packets to a destination station via an intermediate station, instead of to the destination station directly. That is, the intermediate station, which serves as a helper to the source, forwards packets received from the source station to the intended destination station. This cooperative data transmission approach can result in system performance improvement, as long as the total time consumed by two-hop transmission (i.e., transmission via the helper station) is less than direct transmission. Such a determination may be made using rate information stored at each station. Specifically, using the rate information, signaling needed to set up a transmission, the amount of data to be transmitted, etc., transmitting the data directly and via a help station may be compared.

Claims

1. A method for transmitting data from a source wireless LAN device to a destination wireless LAN device, the method comprising:

a) determining a first time needed to transmit the data from the source wireless LAN device directly to the destination wireless LAN device;

b) determining a second time needed to transmit the data from the source wireless LAN device to the destination wireless LAN device via an intermediate wireless LAN device;

c) determining whether or not the second time is less than the first time; and

d) if the second time is determined to be less than the first time, then transmitting the data from the source wireless LAN device to the destination wireless LAN device via the intermediate wireless LAN device.

2. The method of claim 1 further comprising:

e) if the second time is not less than the first time, then transmitting the data from the source wireless LAN device to the destination wireless LAN device directly.

3. The method of claim 1 wherein each of the wireless LAN devices belong to a wireless LAN that employs carrier sense multiple access with collision avoidance.

4. The method of claim 1 wherein each of the wireless LAN devices belong to a wireless LAN that complies with an IEEE 802.11 standard.

5. The method of claim 1 wherein the first time includes a signaling component and a data transmission component, and wherein the second time includes a signaling component and a data transmission component.

6. The method of claim 5 wherein the signaling component of the second time includes

(i) a time to send at least one message of a first type carrying a request to help send, from the source wireless LAN device to the intermediate wireless LAN device,

(ii) a time to send at least one message of a second type carrying an agreement to help send, from the intermediate wireless LAN device to the source wireless LAN device message, and

(iii) a time to send at least one message of a third type carrying a clear to send indicator from the destination wireless LAN device to the source wireless LAN device.

7. The method of claim 6 wherein the message of the first type is a cooperative-request-to-send message, the message of the second type is a helper-to-send message, and the message of the third type is a clear-to-send message.

8. The method of claim 5 wherein both the signaling component of the first time and the signaling component of a second time are determined to be sent at the same rate, and wherein the data transmission component of the first time and the data transmission component of the second time are determined to be sent at different rates.

9. The method of claim 8 wherein the data transmission component of the second time is determined to be sent at a rate that is faster than the signaling component of the second time.

10. The method of claim 1 wherein the second time is determined to be less than the first time, and

wherein the act of transmitting the data from the source wireless LAN device to the destination wireless LAN device via the intermediate wireless LAN device includes:

i) sending, from the source wireless LAN device to the intermediate wireless LAN device, a message of a first type carrying a request to help send,

ii) sending, from the intermediate wireless LAN device to the source wireless LAN device, a message of a second type carrying an agreement to help send,

iii) sending, from the destination wireless LAN device to the source wireless LAN device, a message of a third type carrying a clear to send indicator,

iv) sending the data from the source wireless LAN device to the intermediate wireless LAN device, and

v) sending the data from the intermediate wireless LAN device to the destination wireless LAN device.

11. The method of claim 10 wherein the message of the first type is a cooperative-request-to-send message, the message of the second type is a helper-to-send message, and the message of the third type is a clear-to-send message.

12. The method of claim 10 further comprising:

sending, from the destination wireless LAN device to the source wireless LAN device, an acknowledgement that the data was received.

13. The method of claim 11 wherein the destination wireless LAN device receives and can interpret the request-to-send message sent from the source wireless LAN device to the intermediate wireless LAN device.

14. The method of claim 11 wherein the destination wireless LAN device receives and can interpret the helper-to-send message sent from the intermediate wireless LAN device to the source wireless LAN device.

15. A method for use by a listening wireless LAN device that hears a transmission from a sending wireless LAN device, for discovering wireless LAN conditions, the method comprising:

a) estimating a channel condition between the sending wireless LAN device and the listening wireless LAN device, wherein the channel condition includes a data rate; and

b) storing the data rate, in association with an identifier of the sending wireless LAN device, as a data rate between the sending wireless LAN device and the listening wireless LAN device.

16. The method of claim 15 wherein the channel condition is estimated based on a power strength of the transmission received by the listening wireless LAN device.

17. The method of claim 15 further comprising:

c) storing a time that the transmission was heard, in association with the identifier of the sending wireless LAN device.

18. The method of claim 15 further comprising:

c) storing a second data rate, in association with an identifier of the sending wireless LAN device, as a data rate between the listening wireless LAN device and the sending wireless LAN device, wherein the second data rate is the same as the data rate.

19. The method of claim 15 wherein the identifier of the sending wireless LAN device is a MAC address of the sending wireless LAN device.

20. A wireless LAN device comprising:

a) means for determining a first time needed to transmit data from the wireless LAN device directly to a destination wireless LAN device;

b) means for determining a second time needed to transmit the data from the wireless LAN device to the destination wireless LAN device via an intermediate wireless LAN device;

c) means for determining whether or not the second time is less than the first time; and

d) means for transmitting the data from the wireless LAN device to the destination wireless LAN device via the intermediate wireless LAN device if the second time is determined to be less than the first time.

21. The wireless LAN device of claim 20 wherein the wireless LAN device is adapted for use in a wireless LAN that employs carrier sense multiple access with collision avoidance.

22. The wireless LAN device of claim 20 wherein the means for transmitting the information from the wireless LAN device to the destination wireless LAN device via the intermediate wireless LAN device include:

i) means for sending, from the source wireless LAN device to the intermediate wireless LAN device, a message of a first type carrying a request to help send,

ii) means for sending, from the intermediate wireless LAN device to the source wireless LAN device, a message of a second type carrying a helper-ready-to-send,

iii) means for sending, from the destination wireless LAN device to the source wireless LAN device, a message of a third type carrying a clear to send indicator, and

iv) means for sending the data from the source wireless LAN device to the intermediate wireless LAN device.

23. The wireless LAN device of claim 22 further comprising:

means for sending the data from the intermediate wireless LAN device to the destination wireless LAN device; and

means for the destination wireless LAN device to notify the sending wireless LAN device whether the transmitted data packet is correctly received or not.

24. The wireless LAN device of claim 22 wherein the message of the first type is a cooperative-request-to-send message, the message of the second type is a helper-to-send message, and the message of the third type is a clear-to-send message.

25. The wireless LAN device of claim 20 further comprising:

e) means for estimating a channel condition between the sending wireless LAN device and the wireless LAN device, wherein the channel condition includes a data rate; and

f) a storage means for storing the data rate, in association with an identifier of the wireless LAN device, as a data rate between the sending wireless LAN device and the wireless LAN device.

26. The wireless LAN device of claim 25 further comprising:

g) means for estimating a channel condition between the corresponding wireless LAN device and the destination wireless LAN device, wherein the channel condition includes a data rate; and

h) a storage device storing the data rate, in association with an identifier of the destination wireless LAN device, as a data rate between the corresponding wireless LAN device and the destination wireless LAN device.