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

• US 20020163933A1
• Filed: 11/02/2001
• Published: 11/07/2002
• Est. Priority Date: 11/03/2000
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Benveniste, Mathilde
• Granted Patent: US 7,095,754 B2
• Time in Patent Office: Days
• US Class Current: 370/465
• 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 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

transmitting pending packets in a given urgency class before transmitting packets of a lower urgency class.

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

ordering pending packet transmissions according to their urgency class; and

assigning shorter arbitration times to more urgent packets;

thus restricting contention for a channel to packets that are members of the same urgency class.

3. The method for a distributed medium access protocol of claim 2, which further comprises:

classifying packets with a scheduling algorithm that assigns top urgency classification to packets of real-time traffic, medium urgency classification to isochronous traffic, and least urgency classification to best-effort traffic.

4. The method for a distributed medium access protocol of claim 2, which further comprises:

classifying packets of selected traffic types with a scheduling algorithm that advances packets with short remaining life to a higher urgency class in order to meet QoS requirements.

5. The method for a distributed medium access protocol of claim 2, which further comprises:

reclassifying packets with a scheduling algorithm that adjusts the class assigned to packets in real time based on observed performance parameters and according to QoS requirements.

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

partitioning contention between different traffic classes through specification of arbitration time duration that the channel must be sensed idle by a node following a busy period on the shared medium before backoff countdown may start.

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

using different arbitration times for different packet urgency classes to accomplish quality of service management.

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

performing real-time classification of packets to enable the protocol to be combined with a plurality of QoS-driven scheduling algorithms.

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

remembering the number of transmission attempts by a node for the last transmission of same node;

estimating from said number of transmission attempts the current congestion experienced; and

adjusting a backoff counter to current congestion levels to provide a dispersion of packet traffic bursts.

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

broadcasting with each transmission the number of transmission attempts by a node;

estimating from said number of transmission attempts received from other nodes the current congestion experienced; and

adjusting a backoff counter to current congestion levels to provide a dispersion of packet traffic bursts.

11. The method for a distributed medium access protocol of claim 9, which further comprises:

broadcasting with each transmission the number of transmission attempts by a node;

estimating from said number of transmission attempts received from other nodes the current congestion experienced; and

adjusting a backoff counter to current congestion levels to provide a dispersion of packet traffic bursts.

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

remembering the number of transmission attempts for packets of every urgency class by a node for the last transmission in that class of same node;

estimating from said number of transmission attempts the current congestion experienced by the urgency class of a pending packet; and

adjusting a backoff counter for the pending packet to current congestion levels to provide a dispersion of packet traffic bursts.

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

broadcasting with each transmission the number of transmission attempts by a node and the assigned urgency class;

estimating from said number of transmission attempts received from other nodes the current congestion experienced by the urgency class of the pending packet; and

adjusting a backoff counter of the pending packet to current congestion levels to provide a dispersion of packet traffic bursts.

14. The method for a distributed medium access protocol of claim 12, which further comprises:

broadcasting with each transmission the number of transmission attempts by a node and the assigned urgency class;

estimating from said number of transmission attempts received from other nodes the current congestion experienced by the urgency class of the pending packet; and

adjusting a backoff counter of the pending packet to current congestion levels to provide a dispersion of packet traffic bursts.

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

initializing backoff counters with a relatively longer value, and then decreasing the value upon transmission failure and retrial.

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

remembering the number of transmission attempts by a node for the last transmission of same node;

estimating from said number of transmission attempts the current congestion experienced; and

adjusting a persistence probability to current congestion levels to provide a dispersion of packet traffic bursts.

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

broadcasting with each transmission the number of transmission attempts by a node;

estimating from said number of transmission attempts received from other nodes the current congestion experienced; and

adjusting a persistence probability to current congestion levels to provide a dispersion of packet traffic bursts.

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

broadcasting with each transmission the number of transmission attempts by a node;

estimating from said number of transmission attempts received from other nodes the current congestion experienced; and

adjusting a persistence probability to current congestion levels to provide a dispersion of packet traffic bursts.

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

remembering the number of transmission attempts for packets of every urgency class by a node for the last transmission in that class of same node;

estimating from said number of transmission attempts the current congestion experienced by the urgency class of a pending packet; and

adjusting a persistence probability for the pending packet to current congestion levels to provide a dispersion of packet traffic bursts.

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

broadcasting with each transmission the number of transmission attempts by a node and the assigned urgency class;

estimating from said number of transmission attempts received from other nodes the current congestion experienced by the urgency class of the pending packet; and

adjusting a persistence probability of the pending packet to current congestion levels to provide a dispersion of packet traffic bursts.

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

broadcasting with each transmission the number of transmission attempts by a node and the assigned urgency class;

estimating from said number of transmission attempts received from other nodes the current congestion experienced by the urgency class of the pending packet; and

adjusting a persistence probability of the pending packet to current congestion levels to provide a dispersion of packet traffic bursts.

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

initializing the persistence probability with a relatively lower value, and then increasing the value upon transmission failure and retrial.

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

establishing criteria for cancellation of transmission of a packet associated with packet delay.

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

applying backoff prior to attempting any transmission.

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

checking for permission to transmit by using a specified persistence probability prior to attempting any transmission.

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

applying the method to wireless networks.

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

applying the method to cellular packet networks.

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

applying the method to multi-channel air interface systems selected from the group consisting of FDMA, TDMA, OFDM, and CDMA.

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

applying the method to wireline transmission media.

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

applying the method to optical transmission media.

31. 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;

using class-differentiated arbitration times, as idle time intervals required before transmission is attempted following a busy period on the medium; and

assigning shorter arbitration times to higher urgency classes.

33. The method for a distributed medium access protocol of claim 31, which further comprises:

differentiating packets into additional urgency classes for packets assigned the same arbitration time; and

using different contention resolution mechanisms, thus yielding hybrid packet prioritization.

36. The method for a distributed medium access protocol of claim 31, which further comprises:

said arbitration times of two different urgency classes being at least equal to an arbitration-time increment necessary for a station to discern that another station has seized a channel.

38. The method for a distributed medium access protocol of claim 31, which further comprises:

adjusting backoff probability functions in real time based on congestion estimates derived from a number of re-transmissions attempted by a node.

40. The method for a distributed medium access protocol of claim 38, which further comprises:

adjusting backoff probability functions in real time based on congestion estimates derived from a number of re-transmissions attempted by each of its neighbor nodes.

41. The method for a distributed medium access protocol of claim 39, which further comprises:

adjusting backoff probability functions in real time, based on congestion estimates derived from a number of re-transmissions attempted by each of its neighbor nodes.

42. The method for a distributed medium access protocol of claim 31, which further comprises:

adjusting backoff probability functions in real time based on class-specific congestion estimates derived from a number of re-transmissions attempted by a node.

44. The method for a distributed medium access protocol of claim 38, which further comprises:

adjusting backoff probability functions in real time based on class-specific congestion estimates derived from a number of re-transmissions attempted by each of its neighbor nodes.

45. The method for a distributed medium access protocol of claim 39, which further comprises:

adjusting backoff probability functions in real time based on class-specific congestion estimates derived from a number of re-transmissions attempted by each of its neighbor nodes.

46. The method for a distributed medium access protocol of claim 31, which further comprises:

adjusting backoff probability functions in real time based on congestion estimates derived from a number of re-transmissions attempted by a node.

47. The method for a distributed medium access protocol of claim 31, which further comprises:

adjusting backoff probability functions in real time at a node based on congestion estimates derived from the time spent by packets waiting for transmission.

49. The method for a distributed medium access protocol of claim 47, which further comprises:

adjusting backoff probability functions in real time at a node based on congestion estimates derived from the time spent by packets waiting for transmission at each of its neighbor nodes.

50. The method for a distributed medium access protocol of claim 48, which further comprises:

adjusting backoff probability functions in real time at a node based on congestion estimates derived from the time spent by packets waiting for transmission at each of its neighbor nodes.

51. The method for a distributed medium access protocol of claim 31, which further comprises:

adjusting backoff probability functions in real time at a node based on class-specific congestion estimates derived from the time spent by packets of different classes waiting for transmission.

53. The method for a distributed medium access protocol of claim 51, which further comprises:

adjusting backoff probability functions in real time at a node based on class-specific congestion estimates derived from the time spent by packets of different classes waiting for transmission at each of its neighbor nodes.

59. The method for a distributed medium access protocol of claim 31, which further comprises:

further differentiating packets into urgency classes based on probability density functions of backoff counters whose superposition yields a uniform composite density function, thus achieving efficient dispersion of contending stations'"'"' backoff time.

61. The method for a distributed medium access protocol of claim 31, which further comprises:

further differentiating packets into urgency classes based on different persistence probabilities, by which permission is granted for transmission, for different packets that are assigned the same urgency arbitration time.

32. 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;

using class-differentiated arbitration times, as idle time intervals required before a backoff counter is decreased; and

assigning shorter arbitration times to higher urgency classes.

34. The method for a distributed medium access protocol of claim 32, which further comprises:

differentiating packets into additional urgency classes for packets assigned the same arbitration time; and

using different contention resolution mechanisms, thus yielding hybrid packets prioritization.

35. The method for a distributed medium access protocol of claim 32, which further comprises:

differentiating packets into additional urgency classes using random backoff distribution for packets assigned the same arbitration time.

37. The method for a distributed medium access protocol of claim 32, which further comprises:

said arbitration times of two different urgency classes being at least equal to an arbitration-time increment necessary for a station to discern that another station has seized a channel.

39. The method for a distributed medium access protocol of claim 32, which further comprises:

adjusting backoff probability functions in real time based on congestion estimates derived from a number of re-transmissions attempted by a node.

43. The method for a distributed medium access protocol of claim 32, which further comprises:

adjusting backoff probability functions in real time based on class-specific congestion estimates derived from a number of re-transmissions attempted by a node.

48. The method for a distributed medium access protocol of claim 32, which further comprises:

adjusting backoff probability functions in real time at a node based on congestion estimates derived from the time spent by packets waiting for transmission.

52. The method for a distributed medium access protocol of claim 32, which further comprises:

adjusting backoff probability functions in real time at a node based on class-specific congestion estimates derived from the time spent by packets of different classes waiting for transmission.

54. The method for a distributed medium access protocol of claim 52, which further comprises:

adjusting backoff probability functions in real time at a node based on class-specific congestion estimates derived from the time spent by packets of different classes waiting for transmission at each of its neighbor nodes.

60. The method for a distributed medium access protocol of claim 32, which further comprises:

further differentiating packets into urgency classes based on probability density functions of backoff counters whose superposition yields a uniform composite density function, thus achieving efficient dispersion of contending stations'"'"' backoff time.

62. The method for a distributed medium access protocol of claim 32, which further comprises:

further differentiating packets into urgency classes based on different persistence probabilities, by which permission is granted for transmission, for different packets that are assigned the same urgency arbitration time.

55. 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.

57. The method for a distributed medium access protocol of claim 55, 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.

58. The method for a distributed medium access protocol of claim 56, 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.

56. 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.

63. 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.

64. 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.

65. The method for a distributed medium access protocol of claim 64, which further comprises:

using class-differentiated retrial functions that take the form of lower- and upper-coefficients multiplying the upper and lower bound of a uniform backoff distribution used following transmission failure and subsequent transmission retrial.

66. A system 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:

a first wireless station supplied with data from a source having a low QoS priority; and

a second wireless station supplied with data from a source having a high QoS priority;

said wireless stations each determining an urgency class of its respective pending packets, the urgency classes indicating a desired ordering of transmission; and

said wireless stations transmitting pending packets in a given urgency class 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 a random backoff counter is decreased.

68. The method of claim 67, wherein:

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

69. The method of claim 67, which further comprises:

assigning a longer urgency arbitration time to file transfer data with a lower QoS priority; and

assigning a shorter urgency arbitration time to voice and video data with a higher QoS priority.

70. The method of claim 68, wherein:

said 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 class.

71. The method of claim 68, wherein:

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

72. The method of claim 68, which further comprises:

differentiating between different urgency class transmissions with class-specific urgency arbitration times.

73. The method of claim 68, which further comprises:

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

74. The method of claim 68, which further comprises:

differentiating between different urgency class transmissions with class-specific packet age limits.

75. The method of claim 68, which further comprises:

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

76. The method of claim 68, which further comprises:

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

77. The method of claim 76, wherein:

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

78. The method of claim 76, wherein:

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

79. The method of claim 76, wherein:

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

80. The method of claim 76, wherein:

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

81. The method of claim 76, wherein:

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

82. The method of claim 76, wherein:

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

83. The method of claim 76, wherein:

said congestion estimates are derived from data that include feedback on attempted transmissions provided in headers of transmitted packet s.

67. 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 low QoS priority;

assigning a first class-differentiated urgency arbitration time to said data having a lower QoS priority;

determining in a second wireless station a second urgency class of data having a high QoS priority;

assigning a second class-differentiated urgency arbitration time shorter than said first time, to said data having a higher QoS priority; and

transmitting from said second wireless station pending packets in said second urgency class before transmitting from said first wireless station pending packets in said first urgency class.

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

employing a backoff countdown procedure for channel access;

monitoring traffic intensity changes continuously and providing feedback to the MAC sublayer of contending nodes;

adjusting a backoff counter of each of a plurality of contending nodes to current congestion levels in time intervals shorter than required for the completion of a transmission attempt; and

adjusting such backoff counter in a way that enables older packets to be transmitted before newer ones with high probability, thus minimizing the latency jitter.

85. The method for a medium access protocol of claim 84, which further comprises:

adjusting such backoff counter in a way that their relative ordering is preserved.

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

employing a backoff countdown procedure for random channel access;

monitoring the traffic continuously and providing feedback to the MAC sublayer of contending nodes; and

adjusting the parameters of a random distribution from which the backoff counter is drawn upon initiation of a transmission attempt for each of a plurality of contending nodes to reflect current congestion levels.

87. The method for a medium access protocol of claim 86, which further comprises:

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

adjusting such backoff counters in a way that enables older packets to be transmitted before newer ones with high probability, thus minimizing the latency jitter.

88. The method for a medium access protocol of claim 86, which further comprises:

obtaining traffic intensity measurements continuously and providing feedback to the MAC sublayer of contending nodes.

89. The method for a medium access protocol of claim 86, which further comprises:

obtaining feedback on the success status of transmissions and channel idle time continuously and providing such feedback to the MAC sublayer of contending nodes.

90. The method for a medium access protocol of claim 86, which further comprises:

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

using such estimate for the purpose of backoff-related adjustments.

91. The method for a medium access protocol of claim 86, which further comprises:

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

using such estimate for the purpose of backoff-related adjustments.

92. The method for a medium access protocol of claim 86, which further comprises:

employing a wireless channel; and

performing the monitoring of the channel at the access port.

93. The method for a medium access protocol of claim 86, which further comprises:

employing a wireless channel; and

performing the monitoring of the channel at each of the contending nodes.

94. The method for a medium access protocol of claim 86, which further comprises:

determining system-wide adjustments at the access port; and

supplying such adjustments to all nodes.

95. The method for a medium access protocol of claim 87, which further comprises:

adjusting such backoff counter so that the relative ordering is preserved.

96. 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;

transmitting pending packets in a given urgency class before transmitting packets of a lower urgency class; and

partitioning contention between different traffic classes through specification of arbitration time duration that the channel must be sensed idle by a node before decreasing a backoff counter by one time slot.

97. 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;

using class-differentiated arbitration times, as idle time intervals required for the backoff counter to be decreased by one time slot; and

assigning shorter arbitration times to higher urgency classes.

98. The method for a distributed medium access protocol of claim 97, which further comprises:

differentiating packets into additional urgency classes using different age limits that lead to the cancellation of a transmission if the time since arrival at the MAC layer exceeds the threshold value; and

assigning shorter age limits to delay sensitive traffic classes.

99. 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;

using class-differentiated arbitration times, as idle time intervals required before transmission is attempted following a busy period on the medium;

assigning shorter arbitration times to higher urgency classes;

differentiating packets into additional urgency classes for packets assigned the same arbitration time; and

using different persistence probabilities as a contention resolution mechanism to distribute packet transmission times.

100. 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;

using class-differentiated arbitration times, as idle time intervals required before transmission is attempted following a busy period on the medium;

assigning shorter arbitration times to higher urgency classes;

differentiating packets into additional urgency classes for packets assigned the same arbitration time; and

using different backoff distributions as a contention resolution mechanism to distribute packet transmission times.

101. 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;

using class-differentiated arbitration times, as idle time intervals required before transmission is attempted following a busy period on the medium;

assigning shorter arbitration times to higher urgency classes;

differentiating packets into additional urgency classes for packets assigned the same arbitration time; and

using ALOHA protocol as a contention resolution mechanism to distribute packet transmission times.

102. 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;

using class-differentiated arbitration times, as idle time intervals required before transmission is attempted following a busy period on the medium;

assigning shorter arbitration times to higher urgency classes;

differentiating packets into additional urgency classes for packets assigned the same arbitration time; and

using CSMA/CD protocol as a contention resolution mechanism to distribute packet transmission times.

103. 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:

broadcasting a parameter set in a management packet sent from an AP to associated stations, the parameter set containing the values of class differentiating parameters, such as urgency arbitration times, contention windows, persistence factors, and packet age limits, necessary to support TCMA; and

adjusting such class-differentiating parameter values under the direction of an algorithm at the AP or at a central controller coordinating several APs.

104. The method for a medium access protocol of claim 103, which further comprises:

adjusting such class-differentiating parameters to implement algorithms for flow control.

105. The method for a medium access protocol of claim 103, which further comprises:

adjusting such class-differentiating parameter values for call admission purposes.

106. The method for a medium access protocol of claim 103, which further comprises:

adjusting such class-differentiating parameter values to deliver quality of service as specified by Service Level Agreements.