Tiered contention multiple access (TCMA): a method for priority-based shared channel access

• US 7,983,271 B2
• Filed: 08/21/2006
• Issued: 07/19/2011
• Est. Priority Date: 11/03/2000
• Status: Expired due to Term

• Current Assignee: AT&T Intellectual Property II LP (AT&T, Inc.), AT&T Properties, LLC (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Inventors: Benveniste, Mathilde
• Primary Examiner(s): Hoang, Thai D
• Application Number:
  US11/507,226
• Publication Number:
  US 20070019665A1
• Time in Patent Office: 1,793 Days
• Field of Search: 370/445, 370/447, 370/448, 3703952-39543
• US Class Current: 370/395.4
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2416 Real-time traffic
• CPC Class Codes: H04L 47/2433 Allocation of priorities to traffic types
• CPC Class Codes: H04L 47/245 using preemption
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames
• CPC Class Codes: H04L 47/6275 based on priority
• CPC Class Codes: H04W 28/02 Traffic management, e.g. flow control or congestion control
• CPC Class Codes: H04W 28/0252 per individual bearer or channel dynamic wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 72/569 of the traffic information
• CPC Class Codes: H04W 74/02 Hybrid access
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Quality of Service (QoS) support is provided by a Tiered Contention Multiple Access (TCMA) distributed medium access protocol that schedules transmission of different types of traffic based on their service quality specifications. In one embodiment, a wireless station is supplied with data from a source having a lower QoS priority QoS(A), such as file transfer data. Another wireless station is supplied with data from a source having a higher QoS priority QoS(B). Each wireless station can determine the urgency class of its pending packets according to a scheduling algorithm. There are several urgency classes which indicate the desired ordering. Pending packets in a given urgency class are transmitted before transmitting packets of a lower urgency class by relying on class-differentiated urgency arbitration times (UATs), which are the idle time intervals required before the random backoff counter is decreased.

Claims

1. A method for a distributed medium access protocol that schedules transmission of different types of packets on a channel based on a service quality specification for each type of packet, comprising:

determining in a first wireless station a first urgency class of data having a lower quality of service priority;

assigning a first class-differentiated urgency arbitration time to the data having the lower quality of service priority;

determining in a second wireless station a second urgency class of data having a higher quality of service priority;

assigning a second class-differentiated urgency arbitration time shorter than the first class-differentiated urgency arbitration time, to the data having the higher quality of service priority; and

transmitting from the second wireless station pending packets in the second urgency class before transmitting from the first wireless station pending packets in the first urgency class, wherein each of the first urgency class and the second urgency class comprises an urgency arbitration time, an initial backoff counter, a persistence factor and an age limit.

2. The method of claim 1, wherein:

the urgency classes each having a corresponding urgency arbitration time that must expire before starting a random backoff interval for packets assigned to that urgency class.

3. The method of claim 1, which further comprises:

assigning a longer urgency arbitration time to file transfer data with the lower quality of service priority; and

assigning a shorter urgency arbitration time to voice and video data with the higher quality of service priority.

4. The method of claim 2, wherein:

the random backoff interval is calculated based on a contention window range which has an initial lower value and an initial upper value, which are functions of the urgency classes.

5. The method of claim 2, wherein:

the random backoff interval is selected randomly from a statistical distribution, whose mean and variance are set adaptively in response to an observed traffic intensity.

6. The method of claim 2, which further comprises:

differentiating between different urgency class transmissions with class-specific parameters of a probability distribution used to generate random backoff times and class-specific backoff retry adjustment functions.

7. The method of claim 2, which further comprises:

differentiating between different urgency class transmissions with the persistence factor, pf_i, that is different for each class i, which is used to multiply a backoff window from which backoff counters are drawn randomly upon transmission retrial.

8. The method of claim 2, which further comprises:

differentiating between different urgency class transmissions with a new backoff range determined by traffic congestion estimates.

9. The method of claim 8, wherein:

the congestion estimates are derived from data that include feedback on success or failure of a transmission attempt.

10. The method of claim 8, wherein:

the congestion estimates are derived from data that include feedback on a number of re-transmissions attempted by a node.

11. The method of claim 8, wherein:

the congestion estimates are derived from data that include feedback on a number of re-transmissions attempted by neighbor nodes.

12. The method of claim 8, wherein:

the congestion estimates are derived from data that include feedback on age of retrials of transmissions attempted.

13. The method of claim 8, wherein:

the congestion estimates are derived from data that include feedback on attempted transmissions provided in reservation messages.

14. The method of claim 8, wherein:

the congestion estimates are derived from data that include feedback on attempted transmissions provided in request to send and clear to send messages.

15. The method of claim 8, wherein:

the congestion estimates are derived from data that include feedback on attempted transmissions provided in headers of transmitted packets.

16. A method for a medium access protocol that schedules transmission of packets from a plurality of nodes on a channel, comprising:

employing a backoff countdown procedure for channel access;

monitoring traffic intensity changes continuously and providing feedback to a medium access control sublayer of a plurality contending nodes;

adjusting a backoff counter of each of the plurality of contending nodes to current congestion levels in time intervals shorter than required for completion of a transmission attempt, wherein the backoff counter is a function of an urgency class comprising an urgency arbitration time, an initial backoff counter, a persistence factor and an age limit; and

adjusting the backoff counter of each of the plurality of contending nodes in a way that enables older packets to be transmitted before newer ones with high probability.

17. The method for a medium access protocol of claim 16, which further comprises:

adjusting the backoff counter of each of the plurality of contending nodes in a way that their relative ordering is preserved.

18. A method for a medium access protocol that schedules transmission of packets from a plurality of nodes on a channel, comprising:

employing, at a wireless station, a backoff countdown procedure for random channel access;

monitoring traffic continuously and providing feedback to a medium access control sublayer of a plurality of contending nodes;

adjusting parameters of a random distribution from which a backoff counter is drawn upon initiation of a transmission attempt for each of the plurality of contending nodes to reflect current congestion levels, wherein the parameters comprise an urgency arbitration time, an initial backoff counter, a persistence factor and an age limit;

adjusting, at a wireless station, a backoff counter of each of a plurality of backlogged nodes to reflect current contention levels in time intervals shorter than required for completion of a transmission attempt; and

adjusting the backoff counter of each of the plurality of contending nodes in a way that enables older packets to be transmitted before newer ones with high probability.

19. The method for a medium access protocol of claim 18, which further comprises:

obtaining traffic intensity measurements continuously and providing feedback to the medium access control sublayer of the plurality of contending nodes.

20. The method for a medium access protocol of claim 18, which further comprises:

obtaining feedback on a success status of transmissions and channel idle time continuously and providing the feedback to the medium access control sublayer of the plurality of contending nodes.

21. The method for a medium access protocol of claim 18, which further comprises:

employing feedback information to provide an estimate of an expected number of backlogged nodes; and

using the estimate for backoff-related adjustments.

22. The method for a medium access protocol of claim 18, which further comprises:

employing a wireless channel; and

monitoring the wireless channel at an access port.

23. The method for a medium access protocol of claim 18, which further comprises:

employing a wireless channel; and

monitoring the wireless channel at each of the plurality of contending nodes.

24. The method for a medium access protocol of claim 18, which further comprises:

determining system-wide adjustments at an access port; and

supplying the system-wide adjustments to all nodes.

25. The method for a medium access protocol of claim 18, which further comprises:

adjusting the backoff counter of each of the plurality of contending nodes so that their relative ordering is preserved.