Interaction between Ad Hoc Forwarding and The 802.11 MAC in Ad Hoc Mobile Networks using Directional Antenna

摘要

It has been shown that the use of directional antenna can largely reduce radio interference, thereby improving the utilization of wireless medium and consequently the network throughput. However, due to deafness, directional MAC performs poorly when ad hoc packets are forwarded especially in the string topology. Under the fading channel conditions, it's more difficult for each node to perceive the status of the downlink node. In this paper, a Direction and Communication-Aware MAC (DCA-MAC) scheme is proposed, able to improve the performance of the IEEE802.11 DCF (Distributed Coordination Function) from AWGN(no fading) to fading environments. Omnidirectional transmission from source node can inform its communication status to the up-link-next-hop, without disturbing the neighbors' on-going communication, by the utilization of DNAV(Directional Network Allocation Vector). In addition, the directional antenna gain is controlled adequately according to the number of hops, and keeps the stable performances under any condition. Using QualNet network simulator, we have evaluated the effectiveness of the proposed directional MAC protocol, DCA-MAC in single chain scenario, where the omnidirectional notifications to the up-1 ink-next-hop transmissions with directional antenna gain control can contribute to the throughput improvements for the various environments.