Research On Backoff Algorithm Of Access Control Based On Competition Mechanism In Wireless Ad Hoc Network

In recent years, Ad hoc network has been widely spread and applied with the fast development of wireless communication technology. However, with the increase of network size and network load, network performance such as throughput andlatency declined significantly, which had a negative impact on the further applications of Ad hoc network. As the main factors influencing network performance, access control protocol gradually became a research hotspot.The backoff algorithm based on IEEE802.11DCF (Distribution coordination Function) is studied in this paper. To overcome the non-uniformity of slot option in DCF, the improved algorithm used a parameter sequence for describing the network load changes, then obtained a control parameter to improve the slot option by mathematical prediction processing on the sequence. The control parameter would change dynamically according to network load, so the network node can adjust its slot option by network load adaptively.Further more, fuzzy theory was used to reduce the frequent collisions phenomenon in DCF by establishing a membership function reflecting the relationship between network load and packet collision probability. By processing the membership function, the control parameter of slot option was optimized and collision phenomenon in network decreased obviously. Through the above improvement, the network performance was improved.To demonstrate the performance of improved algorithm, simulation and verification ware carried out by OPNET14.5. The simulation result showed that the improved algorithm can adjust the slot option under different network scale and load, reduce the packet collision probability effectively, and obtain the performance improvement in throughput, packet loss andother network characteristics.