Adaptive Backoff Algorithm Based on Network Congestion in Multi-hop Wireless Ad hoc Networks

In IEEE802.11-based wireless multi-hop Ad hoc networks nodes need to contend for the shared wireless channel, which could result in congestions and waste the limited wireless bandwidth resource. A novel adaptive backoff algorithm based on network congestion-NCBAB (Network-Congestion Based Adaptive Backoff) in media access control (MAC) layer is proposed. In this algorithm, the node adjusts its backoff mechanism according to the feedback of its next-hop´s congestion level during the frame transmission sequence. It increases its minimum contention window of the backoff algorithm when its next-hop gets more severe congestion, and its own contention window decreases with the increasing of backoff stage when it encounters high-level congestion and its next-hop encounters no congestion. The simulation results show that the proposed algorithm can adjust the congested node´s packet receiving and transmitting rate, and can remarkably increase the network end-to-end saturation throughput.