Study of Polynomial Backoff for IEEE 802.11 DCF

Abstract

This paper proposes and studies performance of the IEEE 802.11 distributed coordination function (DCF) with new backoff functions, which are analyzed under saturation conditions. A unified Markov chain model is presented, which is used to obtain theoretical results of saturation throughput for all backoff functions which includes the newly proposed cubic backoff (CB) function. The theoretical results are also verified through simulation experiments. Based on the results, performance of all backoff functions can be improved significantly by setting the minimum window size to typically large values in Basic access mechanism, while a typically small windows size is optimal for RTS/CTS access mechanism. The results also show that CB has significantly higher saturation throughput compared to the standard binary exponential backoff in Basic access mechanism, while it performs better in RTS/CTS access mechanism in cases where number of stations is typically high. One key finding from this study is that performance of the IEEE 802.11 DCF can be improved by optimizing the minimum window size parameters and modifying the window backoff function.