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

• US 20070041398A1
• Filed: 08/21/2006
• Published: 02/22/2007
• Est. Priority Date: 11/03/2000
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Benveniste, Mathilde
• Granted Patent: US 7,864,674 B2
• Time in Patent Office: Days
• US Class Current: 370/448
• 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 means of 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), such as voice and video data. Each wireless station can determine the urgency class of its pending packets according to a scheduling algorithm. For example file transfer data is assigned lower urgency class and voice and video data is assigned higher urgency class. 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. In another embodiment packets are reclassified in real time with a scheduling algorithm that adjusts the class assigned to packets based on observed performance parameters and according to negotiated QoS-based requirements. Further, for packets assigned the same arbitration time, additional differentiation into more urgency classes is achieved in terms of the contention resolution mechanism employed, thus yielding hybrid packet prioritization methods. An Enhanced DCF Parameter Set is contained in a control packet sent by the AP to the associated stations, which contains class differentiated parameter values necessary to support the TCMA. These parameters can be changed based on different algorithms to support call admission and flow control functions and to meet the requirements of service level agreements.

Claims

1. A method for a distributed medium access protocol, comprising:

scheduling transmission of different types of packets on a shared channel; and

including information in the transmitted packets concerning the number of transmission attempts.

3. The method for a distributed medium access protocol of claim 1, which further comprises:

differentiating packets into different urgency classes based on different backoff distributions for different packets that are assigned a same urgency arbitration time.

4. The method for a distributed medium access protocol of claim 3, which further comprises:

further differentiating packets into different urgency classes based on different backoff distributions for different packets that are assigned the same urgency arbitration time.

2. A method for a distributed medium access protocol, comprising:

scheduling transmission of different types of packets on a shared channel; and

including information in the transmitted packets concerning the time spent by the packet waiting transmission.

5. 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 the steps of:

determining at a plurality of nodes in the access network, an urgency class of pending packets according to a scheduling algorithm; and

using class-differentiated time limits that lead to a packet being dropped once the time spent by a packet waiting for transmission has exceeded that limit.

6. 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 the steps of:

determining at a plurality of nodes in the access network, an urgency class of pending packets according to a scheduling algorithm; and

using class-differentiated retrial functions that are used to update parameters of backoff distribution used following transmission failure and subsequent transmission retrial.