A Self-Organizational Back-Off Algorithm Based on Local Topology Analysis

The back-off algorithm is the key point that directly affects the message transmission delay, during the design of the MAC layer of the vehicular ad hoc network communication protocol. However, thanks to the back-off time is inversely proportional to the seizing channel ability of the nodes, the unreasonable choice of the contention window usually leads to the nodes “starvation”. This paper investigates a back-off algorithm to deal with the unfairness problem by changing the size of the contention window by analyzing the connectivity of local topology and the polymerization degrees of the nodes. The algorithm can effectively reduce the node’s unfairness problem. The simulation results show that: comparing to the Binary Exponential back-off algorithm and the Multiplicative Increase, Linear Decrease back-off algorithm, the proposed algorithm can significantly enhance the nodes’ fairness, which also reduces the transmission delay.