An adaptive "sleep" algorithm for efficient power management in WLANs

In an effort to conserve energy, standard protocols for WLANs (IEEE Computer Society, 1997) have the provision for wireless nodes to "sleep" periodically. In this paper we consider the problem of optimizing the timing and duration of sleep states of wireless nodes with the objective of minimizing power consumption with respect to a QoS constraint namely average packet delay. We study downlink traffic only. First, using a dynamic programming formulation coupled with a duality argument, we solve the optimization problem numerically for a two-node system served by a single wired transmitter (access point). Then, using the solutions from the numerical calculations as a guideline, we devise our own algorithm for scheduling the sleep time and duration of multiple wireless nodes operating in an infrastructure mode served by a single access point. Simulation results show that the power efficiency of our algorithm is comparable to the results obtained from the dynamic programming formulation.