A Modified EDCA with Dynamic Contention Control for Real-Time Traffic in Multi-hop Ad Hoc Networks

EDCA (Enhanced Distributed Channel Access), developed for providing service differentiation in wireless LANs, has become a MAC standard in IEEE 80.2.11e. However, unexpected packet delay due to collisions and retransmissions may occur when the wireless LAN becomes congested. To support the increasing demand of delay-sensitive multimedia applications, this paper presents a modified EDCA with dynamic contention control (DCC) for real-time traffic in multi-hop ad hoc networks. The proposed scheme not only reduces the average packet delay but also increases the percentage of packets meeting real-time constraints by two approaches: (1) dynamically adjusting the priority level of a traffic flow based on the estimated per-hop delay, and (2) generating a nonuniformly distributed backoff timer for retransmitted frames according to their individual end-to-end delay requirements. For the purpose of evaluation, we perform simulations on ns-2. We compare the performance of the proposed DCC scheme to EDCA and a previous work, AEDCF (adaptive EDCF). The simulation results demonstrate the effectiveness and superiority of our proposed DCC scheme.