Performance Analysis of a Backoff Algorithm using Finish Tags in IEEE 802.11 Networks

In IEEE 802.11 distributed coordination function (DCF), system throughput decreases as the number of active stations increases on the medium. For improvement of the system throughput, a backoff algorithm which uses finish tags has been proposed. In the backoff algorithm, the finish tag is used to control the backoff time counter. The backoff algorithm has been evaluated with simulations. The simulation results show that the saturation throughput with proper parameters is almost independent on the number of stations. In this paper, we propose an analytical model to study saturation throughput of the backoff algorithm. The analytical model is a Markov chain in which a system state has three variables: the backoff time counter, the backoff stage, and the number of the stations with an older finish tag. Results of the analytical model show that the saturation throughput with proper parameters is independent of the number of stations. It also provides significant improvements of the throughput of the backoff algorithm over IEEE 802.11 DCF