Methods and apparatus for random backoff based access priority in a communications system

• US 6,594,240 B1
• Filed: 10/14/1998
• Issued: 07/15/2003
• Est. Priority Date: 05/22/1998
• Status: Expired due to Term

• Current Assignee: Provenance Asset Group LLC
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Zhang, Qinqing, Chuah, Mooi Choo, Yue, On-Ching
• Primary Examiner(s): TON, DANG T
• Application Number:
  US09/172,494
• Time in Patent Office: 1,735 Days
• Field of Search: 370/328, 370/329, 370/331, 370/337, 370/338, 370/341, 370/342, 370/347, 370/348, 370/449, 370/445, 370/444, 370/443, 370/442, 370/447, 370/448, 370/461, 370/462, 370/468, 370/465, 370/351, 370/352, 370/441, 370/413, 370/312, 455/509, 455/38.2, 455/466, 455/515, 455/547, 455/512, 340/825.5, 340/825.01, 340/825.03, 340/825.51, 710/41, 710/108, 710/116, 710/120, 710/241, 710/244, 375/130, 375/134, 375/137, 375/140
• US Class Current: 370/328
• CPC Class Codes: H04W 74/085 collision avoidance
• CPC Class Codes: H04W 74/0875 with assigned priorities based access
• CPC Class Codes: H04W 84/04 Large scale networks; Deep hierarchical networks
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

The present invention provides methods and apparatus for providing access priority in a MAC protocol of a communications system such as, for example, with respect to UMTS RACH. Particularly, the invention introduces several access priority methodologies including: (i) random chip delay access priority (RCDAP); (ii) random backoff based access priority (RBBAP); (iii) variable logical channel based access priority (VLCAP); (iv) UMTS-specific variable logical channel based access priority (VLCAP′); (v) probability based access priority (PBAP); and (vi) retransmission based access priority (REBAP). Each methodology associates some parameter or parameters to access priority classes in order to influence the likelihood of a remote terminal completing a successful access request to a base station.

Claims

1. A method of access priority control in a remote terminal of a wireless communications system, the method comprising the steps of:

selecting a backoff delay from different backoff delays respectively associated with pre-established access priority classes after determining that a transmitted access request signal has not been received at a base station in the wireless communications system; and

transmitting a new access request signal on a selected logical access channel to the base station after the backoff delay.

2. The method of claim 1, wherein a higher access priority class is associated with a lower backoff delay.

3. The method of claim 1, wherein a lower access priority class is associated with a higher backoff delay.

4. The method of claim 1, wherein determining that the transmitted access request signal has not been received by the base station includes monitoring for receipt of an acknowledgment signal from the base station indicating receipt of the access request signal.

5. The method of claim 1, further including the step of incrementing a variable indicative of a number of access request transmission attempts made to the base station after the determination that a previously transmitted access request has not been received by the base station.

6. The method of claim 5, further including the step of comparing the access request transmission attempt variable to a value indicative of a maximum allowable number of transmission attempts, the maximum allowable transmission attempt value being a function of the pre-established access priority classes.

7. The method of claim 6, further including the step of dropping the access request when the access request transmission attempt variable is greater than the maximum allowable transmission attempt value.

8. The method of claim 7, wherein the backoff delay selection step is performed when the access request transmission attempt variable is not greater than the maximum allowable transmission attempt value.

9. The method of claim 1, wherein the pre-established access priority classes relate to one of service level, message content, and delay requirements.

10. The method of claim 1, further comprising the step of receiving the backoff delays from the base station.

11. The method of claim 1, wherein the backoff delays are associated with random distributions of backoff delays which are respectively associated with the pre-established access priority classes and the selected backoff delay is selected from one of the distributions.

12. The method of claim 1, further including the step of selecting the logical access channel for transmission from among a set of logical access channels, the set including a quantity of logical access channels, the quantity being a function of the pre-established access priority classes.

13. The method of claim 1, further including the step of selecting the logical access channel for transmission by selecting a preamble and a time offset from a set of preambles and a set of time offsets associated with a plurality of logical access channels.

14. The method of claim 13, wherein the set of time offsets are a function of the pre-established access priority classes.

15. The method of claim 1, wherein the pre-established access priority classes have probabilities assigned thereto such that an access request signal is transmitted according to the assigned probability of the class with which the access request is associated.

16. The method of claim 1, wherein the wireless communications system is a Universal Mobile Telecommunications System (UMTS).

17. The method of claim 1, wherein the selected logical access channel is a random access channel (RACH).

18. A method of access priority control in a base station of a wireless communications system, the method comprising the steps of:

broadcasting backoff delays respectively associated with pre-established access priority classes; and

transmitting an acknowledgement signal to a remote terminal in the wireless communications system from which an access request signal has been received.

19. Apparatus for access priority control in a wireless communications system, comprising:

a remote terminal configured for selecting a backoff delay from backoff delays respectively associated with pre-established access priority classes after determining that a transmitted access request signal has not been received at a base station in the wireless communications system, and for transmitting a new access request signal on a selected logical access channel to the base station after the backoff delay.

20. The apparatus of claim 19, wherein the remote terminal is a mobile terminal.

21. The apparatus of claim 19, wherein the remote terminal is a fixed terminal.

22. The apparatus of claim 19, wherein a higher access priority class is associated with a lower backoff delay.

23. The apparatus of claim 19, wherein a lower access priority class is associated with a higher backoff delay.

24. The apparatus of claim 19, wherein determining that the transmitted access request signal has not been received by the base station includes the remote terminal monitoring for receipt of an acknowledgment signal from the base station indicating receipt of the access request signal.

25. The apparatus of claim 19, further wherein the remote terminal increments a variable indicative of a number of access request transmission attempts made to the base station after the determination that a previously transmitted access request has not been received by the base station.

26. The apparatus of claim 25, further wherein the remote terminal compares the access request transmission attempt variable to a value indicative of a maximum allowable number of transmission attempts, the maximum allowable transmission attempt value being a function of the pre-established access priority classes.

27. The apparatus of claim 26, further wherein the remote terminal drops the access request when the access request transmission attempt variable is greater than the maximum allowable transmission attempt value.

28. The apparatus of claim 27, wherein the remote terminal performs the backoff delay selection step when the access request transmission attempt variable is not greater than the maximum allowable transmission attempt value.

29. The apparatus of claim 19, wherein the pre-established access priority classes relate to one of service level, message content, and delay requirements.

30. The apparatus of claim 19, further wherein the remote terminal receives the backoff delays from the base station.

31. The apparatus of claim 19, wherein the backoff delays are associated with random distributions of backoff delays which are respectively associated with the pre-established access priority classes and the selected backoff delay is selected from one of the distributions.

32. The apparatus of claim 19, further wherein the remote terminal selects the logical access channel for transmission from among a set of logical access channels, the set including a quantity of logical access channels, the quantity being a function of the pre-established access priority classes.

33. The apparatus of claim 19, further wherein the remote terminal selects the logical access channel for transmission by selecting a preamble and a time offset from a set of preambles and a set of time offsets associated with a plurality of logical access channels.

34. The apparatus of claim 33, wherein the set of time offsets are a function of the pre-established access priority classes.

35. The apparatus of claim 19, wherein the pre-established access priority classes have probabilities assigned thereto such that an access request signal is transmitted according to the assigned probability of the class with which the access request is associated.

36. The apparatus of claim 19, wherein the wireless communications system is a Universal Mobile Telecommunications System (UMTS).

37. The apparatus of claim 19, wherein the selected logical access channel is a random access channel (RACH).

38. Apparatus for access priority control in a wireless communications system, comprising:

a base station configured for broadcasting backoff delays respectively associated with pre-established access priority classes and for transmitting an acknowledgement signal to a remote terminal in the wireless communications system from which an access request signal has been received.