Minimizing Energy for Wireless Web Access Using Bounded Slowdown

Ronny Krashinsky and Hari Balakrishnan
ACM MOBICOM Conference, Atlanta, GA, September 2002.

On many battery-powered mobile computing devices, the wireless network is a significant contributor to the total energy consumed during its operation. In this paper, we investigate the interaction between energy-saving protocols and TCP performance for Web-like transfers. We show that static protocols like the popular IEEE 802.11 power-saving mode (PSM) can harm performance by increasing fast round trip times (RTTs) to 100ms, and that under typical Web browsing workloads, current implementations will unnecessarily spend energy waking up during long idle periods.

To overcome these problems, we present a power-saving scheme that dynamically adapts to network activity called the Bounded-Slowdown (BSD) protocol . The BSD protocol is an optimal solution to the problem of minimizing energy consumption while guaranteeing that a connection's RTT does not increase by more than a factor p over its base RTT, where p is a protocol parameter that exposes the trade-off between minimizing energy and reducing latency. We present several trace-driven simulation results that show that, compared to 802.11 PSM, the Bounded-Slowdown protocol reduces average Web page retrieval times by 5-64%, while simultaneously reducing energy consumption by 1-14% (and by 13X compared to no power management).

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