POEM: Minimizing Energy Consumption for WiFi Tethering Service

Abstract

Despite the rapidly increasing number of public WiFi hotspots, their coverage is still limited to indoor and office/business environments. WiFi tethering is thus a useful and economic means of providing on-the-go mobile users' Internet connection. One of the main problems of WiFi tethering is the excessive power consumption of mobile access points (APs), or tethered smartphones. Since the power-saving mechanism, defined and deployed in the IEEE 802.11 standard, is intended for clients only, the WiFi interface of a mobile AP never enters the sleep mode. In this paper, we propose a simple but effective system, called power-efficient mobile (POEM), which reduces energy consumption of a mobile AP by allowing its WiFi interface to sleep even during data transfer. The POEM exploits the inherent bandwidth asymmetry between the WiFi and the WWAN interfaces of a mobile AP by buffering the data packets received via the WWAN interface at the mobile AP, thereby allowing the WiFi interface to enter the sleep mode. Compared with the other power-saving solutions for WiFi tethering, the POEM is able to handle various types of applications, such as video steaming and file download, designed to support legacy clients (i.e., clients without POEM), and is also efficient in reducing the clients' energy consumption. We have implemented and conducted an extensive evaluation of the POEM's effectiveness in an android/linux-based test bed. Our experimental results show that the POEM can allow the WiFi interface of a mobile AP to sleep for up to 90% of the total transfer time without significantly affecting system throughput or end-to-end delay.