Network congestion control in ad hoc IEEE 802.11 wireless LAN

An IEEE 802.11 based ad hoc wireless LAN (WLAN) is formed by a set of wireless stations communicating directly with each other without using centralized administration. Ad hoc WLANs are prone to network congestion due to the bursty nature of the data traffic, synchronization difficulties in self-coordination, and the dynamics of the wireless channel. Therefore, wireless stations may experience low throughput and long latency under the circumstance of network congestion, which is especially harmful for real-time traffic. In this paper, a set of preliminary simulations and analysis are conducted to obtain a thorough understanding on the origin of network congestion. We then discuss how to capture the syndrome of network congestion. Note that the occupation rate on buffer, which is employed in active queue management (AQM) algorithms such as random early drop (RED) to predict network congestion, is not appropriate in ad hoc WLANs. New mechanisms suitable for a distributed and contention-based wireless networks are needed. We provide some alternative new designs. We use the optimized network (OPNET) simulator to evaluate the performance of the proposed algorithms and assess their ability in terms of supporting the QoS level set by the applications.