Energy-Efficient Sleep Scheduling for Delay-Constrained Applications Over WLANs

In wireless local area networks (WLANs), switching of the nodes to low-power sleep mode to save energy is common. However, if sleep time is not properly scheduled, significant delays can occur, which is undesirable in delay-constrained applications. In this paper, we propose a novel energy-efficient sleep-scheduling protocol for maximizing the sleep time lengths of each node while satisfying the delay constraints. We first consider the single-user case and present the basic steps that the node takes to decide when and how long it can sleep. For the multiuser scenario, to mitigate channel contention in packet downloading after sleeping, the sleep schedules requested by the nodes are coordinated by the access point (AP) to avoid overlapping active epochs. Simulation results demonstrate that the proposed sleep-scheduling algorithm achieves lower loss rate while achieving higher energy efficiency than that of the existing GreenCall method.