Modified backoff mechanism for wireless networks

• US 20060034208A1
• Filed: 08/10/2004
• Published: 02/16/2006
• Est. Priority Date: 08/10/2004
• Status: Abandoned Application

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Blouin, Francois
• Application Number:
  US10/914,365
• Publication Number:
  US 20060034208A1
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04L 1/1887 Scheduling and prioritising arrangements
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 74/085 collision avoidance

Abstract

In a scheme for accessing a wireless network, a backoff delay time period representing a duration of time that is to elapse before a station is permitted to attempt a retransmission is selected from a group of delay periods. The group of delay periods grows at a rate that is less than exponentially (e.g. linearly) based on the number of attempted retransmissions. Selection of the backoff delay time period may entail random selection of an integer N from a contention window and multiplication of N by a slot time duration. The contention window may be a range of integers [0, W-1]. The contention window size W may be initialized to a predetermined minimum value upon a first attempted transmission and may be capped at a predetermined maximum value. Average backoff delay may be reduced in comparison to a binary exponential backoff approach.

Claims

1. A method of accessing a wireless network, comprising:

for each of a plurality of attempted retransmissions;

increasing the size of a group of delay periods such that said group grows at a rate that is less than exponentially with the number of attempted retransmissions; and

selecting a delay period from said group of delay periods for use in scheduling a retransmission over said wireless network.

2. The method of claim 1 wherein said increasing comprises increasing said group of delay periods by a fixed number of delay periods upon each attempted retransmission.

3. The method of claim 2 wherein said fixed number is four.

4. The method of claim 1 wherein each of said delay periods is an integer value, wherein said selecting a delay period results in a selected integer value, and wherein said scheduling a retransmission comprises delaying said retransmission for a time period equal to said selected integer value multiplied by a time slot duration.

5. The method of claim 4 wherein said group of integer values comprises a range of integers.

6. The method of claim 5 wherein said range of integers is from zero to W minus one inclusive, where W is a contention window size.

7. The method of claim 1 wherein said selecting a delay period comprises randomly and uniformly selecting said delay period from said group of delay periods.

8. The method of claim 1 further comprising setting said delay period to a predetermined minimum value upon a first attempt to transmit.

9. The method of claim 1 further comprising setting said delay period to a predetermined maximum value when the number of attempted retransmissions reaches or exceeds a threshold.

10. The method of claim 1 wherein said wireless network is a local area network.

11. The method of claim 1 wherein said wireless network conforms to an Institute of Electrical and Electronics Engineers (IEEE) standard selected from the group consisting of the IEEE 802.11, 802.11a, 802.11b, 802.11e, and 802.11g standards.

12. A computer-readable medium storing instructions which, when executed by a station in a wireless network, cause said station to:

for each of a plurality of attempted retransmissions;

increase the size of a group of delay periods such that said group grows at a rate that is less than exponentially with the number of attempted retransmissions; and

select a delay period from said group of delay periods for use in scheduling a retransmission over said wireless network.

13. The computer-readable medium of claim 12 wherein said increasing the size of said group of delay periods comprises increasing the size of said group of delay periods by a fixed number of delay periods upon each attempted retransmission.

14. The computer-readable medium of claim 13 wherein said fixed number is four.

15. The computer-readable medium of claim 12 wherein each of said delay periods is an integer value, wherein selecting a delay period results in a selected integer value, and wherein said scheduling a retransmission comprises delaying said retransmission for a time period equal to said selected integer value multiplied by a time slot duration.

16. The computer-readable medium of claim 15 wherein said group of integer values comprises a range of integers.

17. The computer-readable medium of claim 16 wherein said range of integers is from zero to W minus one inclusive, where W is a contention window size

18. The computer-readable medium of claim 12 wherein selecting a delay period comprises randomly and uniformly selecting said delay period from said group of delay periods.

19. The computer-readable medium of claim 12 wherein said instructions further cause said station to set said delay period to a predetermined minimum value upon a first attempt to transmit.

20. The computer-readable medium of claim 12 wherein said instructions further cause said station to set said delay period to a predetermined maximum value when the number of attempted retransmissions reaches or exceeds a threshold.

21. The computer-readable medium of claim 12 wherein said wireless network is a local area network.

22. The computer-readable medium of claim 12 wherein said wireless network conforms to an Institute of Electrical and Electronics Engineers (IEEE) standard selected from the group consisting of the IEEE 802.11, 802.11a, 802.11b, 802.11e, and 802.11g standards.

23. A station in a wireless network operable to access said network by:

for each of a plurality of attempted retransmissions;

increasing the size of a group of delay periods such that said group grows at a rate that is less than exponentially with the number of attempted retransmissions; and

selecting a delay period from said group of delay periods for use in scheduling a retransmission over said wireless network.

24. The station of claim 23 wherein said increasing comprises increasing said group of delay periods by a fixed number of delay periods upon each attempted retransmission.

25. The station of claim 24 wherein said fixed number is four.

26. The station of claim 23 wherein each of said delay periods is an integer value, wherein said selecting a delay period results in a selected integer value, and wherein said scheduling a retransmission comprises delaying said retransmission for a time period equal to said selected integer value multiplied by a time slot duration.

27. The station of claim 26 wherein said group of integer values comprises a range of integers.

28. The station of claim 27 wherein said range of integers is from zero to W minus one inclusive, where W is a contention window size.

29. The station of claim 23 wherein said selecting a delay period comprises randomly and uniformly selecting said delay period from said group of delay periods.

30. The station of claim 23 further operable to set said delay period to a predetermined minimum value upon a first attempt to transmit.

31. The station of claim 23 further operable to set said delay period to a predetermined maximum value when the number of attempted retransmissions reaches or exceeds a threshold.

32. The station of claim 23 wherein said wireless network is a local area network.

33. The station of claim 23 wherein said wireless network conforms to an Institute of Electrical and Electronics Engineers (IEEE) standard selected from the group consisting of the IEEE 802.11, 802.11a, 802.11b, 802.11e, and 802.11g standards.