Modeling and Analyzing the Optimal Contention Window Size for Distributed Synchronization in Ad Hoc Networks

Contention-based distributed synchronization (CDS) protocols, which first standardized in the IEEE 802.11 power saving mode (PSM), have been widely used in wireless ad hoc networks. The time required to complete the synchronization progress, i. e., synchronization efficiency, is obviously an important performance metrics for CDS protocols. However, few attempts have been focusing on modeling and analyzing the synchronization efficiency of the CDS protocols. In this letter, we present a 2-D Markov chain model for the CDS scheme of the IEEE 802.11 PSM. The purpose of our model is to determine the relationship between the time required to complete the synchronization process and the value of the contention parameter, i. e., the contention window size. Through modeling, we derive the optimal values of the contention window size to achieve the minimum synchronization time at different network scales. We also validate the accuracy of our model by comparing the analytical results with that obtained by means of simulations.