Energy Saving Strategies for Mobile Devices using Wake-up Signals

Voice-over-IP (VoIP) has rapidly gained popularity in the last years, especially on smartphones platforms. In fact, WLAN chip-sets are becoming more common on smartphones, allowing users to use VoIP services from their mobile devices. On the other hand, the excessive energy consumption of the WLAN chip-set, limits the widespread use of VoIP on mobile phones. As most of the energy is spent when the WLAN is in idle mode waiting for a call, a possible solution is to use a secondary air interface, with lower energy consumption, as a signalling channel to wake up the WLAN radio. In this paper we describe two approaches to address this problem, namely the overlay and cooperative approaches. We present measurements of energy consumption done on a commercial device to show that the presented approaches can reduce the energy consumption for VoIP calls on smartphones over WLAN.