D-LSMA: distributed link scheduling multiple access protocol for QoS in ad-hoc networks

The paper presents a novel medium access control (MAC) protocol for QoS support in multi-hop ad-hoc wireless networks. The proposed D-LSMA (distributed link scheduling multiple access) protocol uses an extension of the 802.11 CSMA/CA procedure as the basis for a distributed link scheduling algorithm which results in dynamic TDMA-like bandwidth allocation among neighboring wireless nodes without the need for global synchronization. In addition to supporting QoS, the proposed scheduling technique also solves the "exposed node" problem in ad-hoc 802.11, thus resulting in improved throughput in many scenarios. Simulation results from an ns-2 model are presented for a 15-node random ad-hoc network. The results demonstrate significant performance improvements relative to ad-hoc 802.11, with capacity increases typically ∼20% for the example considered. Also, the D-LSMA network is shown to offer far better real-time packet delay and fairness properties than 802.11, particularly under overload and heavy contention conditions.