Adaptation of TDMA Parameters Based on Network Conditions

Soft clustering of the nodes combined with time division multiple access (TDMA) channel access within a cluster has been shown to provide an energy-efficient solution for mobile ad-hoc networks (MANET). Such channel access schemes use a parameter that is critical in determining network performance: the number of frames per superframe, which determines the amount of spatial reuse possible, similar to the frequency reuse factor in cellular networks. When a smaller number of frames per superframe is used, each frame will consist of a larger number of slots, enabling the frame (i.e., cluster) to support more nodes, but also limiting the choices of frames for clusterheads to select, causing higher co-channel interference and collisions. Conversely, when a larger number of frames per superframe is used, the clusterheads will only be able to grant channel access to a limited number of nodes, which in turn increases the number of dropped packets (i.e., blocked channel access). The optimum value of the number of frames is the one that minimizes the combined effect of both collisions and dropped packets. By analytically determining the effects of dropped packets and collisions, we can find the optimal value for any given scenario. This paper develops a model to determine the optimal TDMA structure under various settings, showing the advantages that can be obtained by adapting protocol parameters as network conditions change.