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Many existing medium access control (MAC) protocols utilize past information (e.g., the results of transmission attempts) to adjust the transmission parameters of users. This paper provides a general framework to express and evaluate distributed MAC protocols utilizing a finite length of memory for a given form of feedback information. We define protocols with memory in the context of a slotted random access network with saturated arrivals. We introduce two performance metrics, throughput and average delay, and formulate the problem of finding an optimal protocol. We first show that a time-division multiple access (TDMA) outcome, which is the best outcome in the considered scenario, can be obtained after a transient period by using a protocol with -slot memory, where is the total number of users. Next, we analyze the performance of protocols with one-slot memory using a Markov chain and numerical methods. Protocols with one-slot memory can achieve throughput arbitrarily close to 1 (i.e., 100% channel utilization) at the expense of large average delay by correlating successful users in two consecutive slots. Finally, we apply our framework to wireless local area networks (WLANs).
Date of Publication: Dec. 2010