A microscopic study of power management in IEEE 802.11 wireless networks

IEEE 802.11 power saving mode (PSM) has been proposed in wireless LANs and multi-hop wireless networks to coordinate power states of wireless devices. In IEEE 802.11 PSM, power management decisions to wake up wireless devices or put them to sleep states are made periodically in every beacon interval. In this paper, we demonstrate via a rigorous, analytical model (the result of which is corroborated by simulation results) that such a periodic structure together with its signaling overhead leads to both energy and bandwidth under-utilization. We then devise SIMPA, a new power management protocol based on IEEE 802.11 PSM, to decouple the power management decision points and the beacon intervals, so as to allow fine grained control. In SIMPA, wireless devices can switch to the sleep state inside a beacon interval or extend their active states beyond one beacon interval. A comprehensive simulation study in both single hop wireless LANs without the AP support and multi-hop wireless networks demonstrates that as compared to IEEE 802.11 PSM, SIMPA can effectively reduce energy consumed under light to medium traffic loads and retain the network capacity for data transport at high traffic loads.