Reducing overhearing energy in 802.11 networks by low-power interface idling

In this paper we propose and analyze a new interface idling mechanism for improving energy efficiency of IEEE 802.11 based MAC hardware. A novel protocol state analysis technique is developed for detecting time windows during which a wireless interface consumes energy due to 802.11 overhearing. During this window, energy savings at the MAC layer is accomplished by forcing the wireless interface to a relatively lower-energy idling state. At the end of this window, the interface is transitioned back to its regular receiving mode. Energy savings are realized by exploiting the difference in power consumption between the overhearing state and the idling state. We evaluate the proposed protocol using ns-2 simulator. Simulation experiments validate that the proposed mechanism is capable of significantly reducing overhearing expenditure for newer 802.11 cards that support low-energy idling mode as described above. Our experimentation with Socket Communications Inc. low power 802.11 card demonstrate that the reduction in overhearing expenditure can be up to 23% and the subsequent network life extension can be up to 86% Results also show that the proposed MAC layer idling is fairly insensitive to network loading.