Scheduled PSM for Minimizing Energy in Wireless LANs

Power conservation is a general concern for mobile computing and communication. In this paper, we investigate the performance of the current 802.11 power saving mechanism (unscheduled PSM) and demonstrate that background network traffic can have a significant impact on the power consumption of mobile stations. To improve power efficiency, a scheduled PSM protocol based on time slicing is proposed in this paper. The protocol adopts the mechanism of time division, schedules the access point to deliver pending data at designated time slices, and adaptively adjusts the power state of the mobile stations. The proposed scheme is near theoretical optimal for power saving in the sense that it greatly reduces the effect of background traffic, minimizes the station idle time, and maximizes its energy utilization. Comprehensive analysis and simulations are conducted to evaluate the new protocol. Our results show that it provides significant energy saving over the unscheduled PSM, particularly in circumstances where multiple traffic streams coexist in a network. Moreover, it achieves the saving at the cost of only a slight degradation of the one-way delay performance.