MAC Enhancement for Performance Improvement of Routing Protocol

Mobile Ad hoc network allow wireless devices to dynamically self organize into arbitrary and temporary wireless topologies without fixed communication infrastructure. One of the most popular MAC layer protocol used in Ad hoc network is 802.11b. Since the IEEE 802.11 standard support multiple data rates at the physical layer, many rate adaptation mechanisms have been proposed to utilize this multi rate capability by dynamically switching rates in response to different channel conditions. Because of varying channel condition, 802.11b products degrade the bit rate from the nominal 11Mbps to 5.5,2 or 1Mbps. When a host detects repeated unsuccessful frame transmission, it decreases its bit rate. If there is at least one host with a lower rate, 802.11 cells presents a performance anomaly. The throughput of all the hosts transmitting at higher rate is degraded below the level of the lower rate. In IEEE 802.11b networks, the guarantee of equal transmission opportunity for all participating nodes results in performance anomaly. We propose a new cross layer MAC mechanism, which allows nodes acquire the whole path’s rate information by exchanging information between MAC and Routing layer at every node. The interactions between MAC and Routing Layer are fully exploited to achieve higher performance using AODV routing protocol. Nodes acquire the whole path’s rate information by following a cross layer design approach. We evaluate the performance measured on the network simulator OMNet++