Performance Optimization of Duty-Cycled MAC in Delay-Energy Constrained Sensor Network Under Uniform and Non-Uniform Traffic Generation

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Duty-Cycle at the MAC layer plays a key role in energy savings and network lifetime extension. It consists in putting a node’s radio in the sleep state as soon as it has no communication activity. Traditional WSN MAC protocols are designed with short duty cycles at the cost of long delays. Careful design is required for joint energy-delay constrained applications, where the optimal parameters should be thoroughly derived. The present paper deals with this issue and mathematically derives optimal values of key MAC parameters under low data rate applications for three well known duty-cycled MAC protocols, WiseMAC, SCP-MAC, and LMAC as representatives of three MAC protocol categories, respectively preamble-sampling, slotted contention-based and frame-based. The analysis provides also the optimum traffic sampling rate that guarantees the minimum energy consumption. It shows the role of these parameters in achieving the targeted e2e (end-to-end) delay constraints under network models with uniform traffic generation, for ring and grid topologies. As a second contribution, the model is extended to non-uniform traffic scenarios, where a certain percentage of deployed nodes are relays whose role is to balance traffic forwarding and save the overall network energy. The results reveal that different optimal internal MAC parameters and traffic generation rates can be found for different configurations of relay nodes deployment, which achieve minimal network energy consumption while satisfying the application required e2e delay threshold
Wireless Sensor Networks, Duty-Cycling, Energy-Efficiency, End-to-End Delay, Performance Optimization