A Real-Time, Distributed, Directional TDMA MAC Protocol for QoS-Aware Communication in Multi-Hop Wireless Networks

Time division multiple access (TDMA) based medium access control (MAC) schemes are widely used for communication among directional nodes since they can provide a conflict-free transmission schedule. However, the existing directional TDMA schemes introduce significant overhead and delay, and cannot adapt in real-time to topology changes in a directional multi-hop network. These schemes also incur considerable overhead and delay in order to support the QoS (quality of service) traffic. In this paper, a novel, real-time, distributed, directional TDMA scheme is presented for directional multi-hop wireless networks. This scheme adapts to the topology changes and/or flow requirements in real-time , and facilitates QoS-aware communication with no notification overhead . In the proposed scheme, the 1-hop neighborhood of every node is divided into fully connected 1-hop neighborhoods , which allows the node to intelligently serve multiple routes without requiring a globally converged scheduling solution. This feature allows the use of a low-complexity rank-based mechanism to obtain a distributed, real-time transmission schedule for a directional multi-hop network. The following new features are also added in the proposed scheme: ( ${i}$ ) REQ period which reduces slot wastage, ( ii ) throughput scaling which ensures fairness and helps in congestion management, and ( iii ) piggyback reservation period which increases the spatial reuse and adapts to the dynamic requirements of multiple flows in real-time. The control-period overhead in our scheme is low and linearly changes with the number of nodes in a fully connected 1-hop neighborhood, instead of the total number of nodes in the entire network. Simulation results and comparisons with other recent, distributed TDMA-based schemes show that our scheme provides a higher throughput with very low control overhead for both static and mobile network topologies.