Performance analysis of the IEEE 802.11 distributed coordination function
IEEE Journal on Selected Areas in Communications
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Under a distributed media access control (MAC) scheme, wireless stations select random time slots for transmission upon observing an idle channel. Performance of a distributed MAC scheme often depends on its ability to minimize collisions by reducing simultaneous data packet transmissions by two or more stations in any particular time slot. For this sake, each wireless station withholds its transmission until it observes a random number of idle slots when channel becomes idle. A station selects time slot for transmission based on a random number generated from a range of values in contention window (CW). As all stations independently generate their random value from their CW range, a large CW size is desirable for better channel arbitration. This is because, small CW sizes will lead to more number of collisions, and higher collisions will reduce throughput performance. This paper discusses and analyzes a scheme that can enhance throughput performance by reducing collisions under small CW sizes. The presented scheme is applicable to "Enhanced distributed channel access (EDCA)" protocol in which highest priority AC_VO queue uses very small CW sizes.