Performance analysis of topology-unaware TDMA MAC schemes for ad hoc networks with topology control

Traditional omni-directional antennas result in increased mutliuser interference and are known to limit the performance of Medium Access Control (MAC) protocols for ad-hoc networks. Topology control is the capability of a node to control the set of neighbor nodes and in this paper, the impact of using smart antennas and/or power control for topology control is investigated. The performance of TDMA MAC schemes with common frame for which the assignment of time slots to a node is not aware of the time slots assigned to the neighbor nodes (topology-unaware schemes like the Deterministic Policy and the Probabilistic Policy), is studied as well. A comparison based on analytical models reveals the advantages of topology control, as well as its dependence on the mobility of the nodes and its resolution. It is shown that topology control with “high resolution” in highly mobile environments may not be effective and conditions are established under which topology control is beneficial. Simulation results for a variety of network topologies support the claims and the expectations of the aforementioned analysis and show that the system throughput achieved under topology control can be higher under both policies and especially under the Probabilistic Policy. Simulation results also show how mobility affects system throughput and that topology control may not be suitable for highly mobile environments.