IEEE 802.11 protocol: Design and performance evaluation of an adaptive backoff mechanism

In WLANs, the medium access control (ILIAC) protocol is the main element th at determines the efficiency of sharing the limited communication bandwidth of the wireless channel. The fraction of channel bandwidth used by success fully transmitted messages gives a good indication of the protocol efficien cy, and its maximum value is referred to as protocol capacity. In a previou s paper we have derived the theoretical limit of the IEEE 802.11 MAC protoc ol capacity. In addition, we showed that if a station has an exact knowledg e of the network status, it is possible to tune its backoff algorithm to ac hieve a protocol capacity very close to its theoretical bound. Unfortunatel y, in a real case, a station does not have an exact knowledge of the networ k and load configurations (i.e., number of active stations and length of th e message transmitted on the channel) but it can only estimate it. In this work we analytically study the performance of the IEEE 802.11 protocol with a dynamically tuned backoff based on the estimation of the network status. Results obtained indicate that under stationary traffic and network config urations (i.e., constant average message length and fixed number of active stations), the capacity of the enhanced protocol approaches the theoretical limits in all the configurations analyzed. In addition, by exploiting the analytical model, we investigate the protocol performance in transient cond itions (i.e., when the number of active stations sharply changes).