Research On MAC QoS Technologies In Mobile Ad Hoc Networks

As a multi-hop and peer-to-peer network, mobile ad hoc network has attracted more and more attentions for its convenience and flexibility in both military field and civilian fields. But the dynamic topology and limited network resources bring great challenges to implement QoS in ad hoc networks.MAC (Medium Access Control) protocol, which lies in the bottom of the protocol stack, is the key to implement QoS in ad hoc networks. In Ad Hoc network, hop count plays an important role in QoS implementation of ad hoc networks. For a single data flow, the end-to-end throughput decreases with the increasing of the hop count in the flow. For two neighboring data flows with different hop count, the shorter flow is entitled to much larger bandwidth than the longer flow. Unfairness exists in ad hoc networks among flows with different hop counts. Most of the BEB (Binary Exponential Backoff) related MAC backoff algorithms adjust the parameters in backoff process according to the current network parameters such as throughput, delay and so on, which ignore the hop count factors in Ad Hoc networks.This thesis gives a novel MAC backoff mechanism based on hop count of the data packet to transmit. Nodes in network adjust its backoff parameters dynamically based on the rest hop count of the packet, in order to balance the network resource. By simulation under OPNET, the new algorithm to some extent alleviates the unfairness among flows with different hop counts, and improves the performance of the network.