Energy efficient Wifi tethering on a smartphone

While numerous efforts have been made to save energy of “client” devices but it has not been addressed for access points (APs) as they are assumed to be supported by AC power. This paper proposes E-MAP, which is an energy saving algorithm for a tethering smartphone that plays a role of mobile AP (MAP) temporarily. It saves MAP's energy by introducing the sleep cycle as in power save mode (PSM) in 802.11 but successfully keeps clients from transmitting while it sleeps. One important design goal of E-MAP is backward compatibility, i.e., it requires no modification on the client side and supports PSM and adaptive PSM (A-PSM) as well as normal constant awake mode (CAM) clients. Experiments show that E-MAP reduces the energy consumption of a Wifi tethering smartphone by up to 54% with a little impact on packet delay under various traffic patterns derived from real-life traces.