Client-Centered, Energy-Efficient Wireless Communication on IEEE 802.11b Networks

In mobile devices, the wireless network interface card (WNIC) consumes a significant portion of overall system energy. One way to reduce energy consumed by a device is to transition its WNIC to a lower-power sleep mode when data is not being received or transmitted. In this paper, we investigate client-centered techniques for energy efficient communication, using IEEE 802.11b, within the network layer. The basic idea is to conserve energy by keeping the WNIC in high-power mode only when necessary. We track each connection, which allows us to determine inactive intervals during which to transition the WNIC to sleep mode. Whenever necessary, we also shape the traffic from the client side to maximize sleep intervals—convincing the server to send data in bursts. This trades lower WNIC energy consumption for an increase in transmission time. Our techniques are compatible with standard TCP and do not rely on any assistance from the server or network infrastructure. Results show that during Web browsing, our client-centered technique saved 21 percent energy compared to PSM and incurred less than a 1 percent increase in transmission time compared to regular TCP. For a large file download, our scheme saved 27 percent energy on average with a transmission time increase of only 20 percent.