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Network-Assisted Power Management for WiFi Devices


WiFi radios in smart-phones consume a significant amount of power when active. The 802.11 standard allows these devices to save power through an energy-conserving Power Save Mode (PSM). However, depending on the PSM implementation strategies used by the clients/Access Points (APs), the presence of competing background traffic results in one or more of the following negative consequences: a significant increase, up to 300%, in a client’s energy consumption, a decrease in wireless network capacity due to unnecessary retransmissions, and unfairness.

NAPman is a novel WiFi power-save management (PSM) approach that addresses several serious drawbacks of existing PSM implementations. NAPman leverages AP virtualization and a new energy-aware fair scheduling algorithm to minimize client energy consumption and unnecessary retransmissions, while ensuring fairness among competing traffic. NAPman is incrementally deployable via software updates to the AP and does not require any changes to the 802.11 protocol or the mobile clients. Our prototype implementation improves the energy savings on a smart-phone by up to 70% under varied settings of background traffic.