We propose a new Markov model for the distributed coordination function (DCF) of IEEE 802.11. The model incorporates

carrier sense, non-saturated traffic and SNR, for both basic andRTS/CTS access mechanisms. Analysis of the model shows that the throughput

first increases, and then decreases with the number of active stations, suggesting the need for an admission control mechanism.

We introduce such a mechanism, which tries to maximize the throughput while maintaining a fair allocation. The maximum achievable

throughput is tracked by the mechanism as the number of active stations increases. An extensive performance analysis shows that the

mechanism provides significant improvements.

The wireless token ring protocol (WTRP) is a novel medium access control (MAC) protocol for wireless local area networks (WLANs). In contrast with IEEE 802.11 networks, WTRP guarantees quality of service (QoS) in terms of bounded latency and reserved bandwidth, which are critical in many real-time applications. Compared to 802.11, WTRP improves efficiency by reducing the number of retransmissions due to collisions, and it is more fair as all stations use the channel for the same amount of time. Stations take turns transmitting and give up the right to transmit after a specified amount of time. WTRP is a distributed protocol that supports many topologies, as not all stations need to be connected to each other or to a central station. WTRP is robust against single node failures, and recovers gracefully from multiple simultaneous faults. WTRP is suitable for interaccess point coordination in ITS DSRC, safety-critical vehicle-to-vehicle communications, and home networking, and provides extensions to other networks and Mobile IP.