Analysis of Latency in Finite Duty Cycling Wireless Networks

Sleep-wake scheduling (or duty cycling) of radio transceivers is a well known technique for achieving energy conservation in wireless ad hoc and sensor networks. While putting nodes to sleep for certain durations of time saves energy since they cannot transmit, receive or listen, it also results in lower throughput capacity in the network and increased packet latency. At low rates of duty cycling, packets may have to wait at intermediate nodes in a multi-hop path before reaching the destination and thus may incur significant end-to-end latency. In this paper, we investigate how latency between source and destination nodes varies with parameters such as wakeup probability in a slot, p and size of the multi-hop network, n. We study regular networks such as 1D line and 2D grid and derive exact expressions for average latency of a wait-and-forward routing scheme as a function of p and n. This is useful for the adaptation of slot wakeup probabilities in order to meet a certain latency bound. We also study the latency performance of a greedy random walk approach and show by simulation that it is significantly worse than that of the the wait-and-forward approach in 2D grid topologies.