Energy savings by intelligent interface idling in 802.11 based wireless networks

In this paper we propose and analyze a new interface idling mechanism for improving carrier-sense energy expenditure of IEEE 802.11 based wireless network interfaces. A novel protocol state analysis technique is developed for detecting time windows during which a node consumes energy due to erroneous carrier sensing. During this window, energy savings at the MAC layer is accomplished by forcing a wireless interface to a relatively low-energy idling state. At the end of this window, an interface is transitioned back to its regular receiving mode. Energy savings are realized by exploiting the difference in power consumption between the erroneous carrier sensing state and the idling state. We evaluate the proposed protocols using ns-2 simulator. Simulation experiments demonstrate that the proposed mechanisms are capable of significantly reducing erroneous carrier sensing expenditure for newer generation of 802.11 cards that support low-energy idling modes as described above. Our experimentation with Socket Communication Inc.´s low power 802.11 card demonstrate that the reduction in combined overhearing and erroneous carrier sensing expenditure can be up to 62% and can extend network life by up to 154%. Results also show that the proposed MAC layer idling is fairly insensitive to mobility