Energy-efficient PCF operation of IEEE 802.11a WLANs via transmit power control
Transmit power control (TPC) has been recognized as one of the effective ways to save energy in wireless devices. In this paper, we demonstrate the energy-efficient point coordination function (PCF) operation of IEEE 802.11a wireless local-area networks (WLANs) via TPC and physical layer (PHY) rate adaptation. The basic idea is that the best transmit power level as well as the proper PHY rate are adaptively selected by a wireless station to transmit an uplink data frame, according to the up-to-date path loss condition between itself and the point coordinator, thus delivering data with minimum energy consumption. Evaluation results show that significant energy savings can be achieved by combining TPC with adaptive PHY rate selection. Note that a key requirement for a wireless station to realize the proposed energy-efficient PCF operation is the knowledge of the path loss, and we present a simple, novel, and effective path loss estimation scheme for this purpose. The results and conclusions presented in this paper should serve as a valuable guidance or reference for the design of future 5 GHz 802.11 WLAN systems.