Abstract-In WLANs, the medium access control (MAC) protocol is the main element that determines the efficiency of sharing the limited communication bandwidth of the wireless channel. The fraction of channel bandwidth used by successfully transmitted messages gives a good indication of the protocol efficiency, and its maximum value is referred to as protocol capacity. In a previous paper we have derived the theoretical limit of the IEEE 802.11 MAC protocol capacity. In addition, we showed that if a station has an exact knowledge of the network status, it is possible to tune its backoff algorithm to achieve a protocol capacity very close to its theoretical bound. Unfortunately, in a real case, a station does not have an exact knowledge of the network and load configurations (i.e., number of active stations and length of the 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 configurations (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 conditions (i.e., when the number of active stations sharply changes). Index Terms-Markov chain, multiple access protocol (MAC), performance analysis, protocol capacity, wireless LAN (WLAN).
Cali et al. REF propose a method that estimates the number of active stations via the number of empty slots, and exploit the estimated value to tune the contention window value based on their analytic model.
IEEE 802.11 protocol: design and performance evaluation of an adaptive backoff mechanism
IEEE Journal on Selected Areas in Communications
IEEE Journal on Selected Areas in Communications
Computer Science