ECOPS: Energy-Efficient Collaborative Opportunistic Positioning for Heterogeneous Mobile Devices

The fast growing popularity of smartphones and tablets enables us to use various intelligent mobile applications. As many of those applications require position information, smart mobile devices provide positioning methods such as Global Positioning System (GPS), WiFi-based positioning system (WPS), or Cell-ID-based positioning service. However, those positioning methods have different characteristics of energy-efficiency, accuracy, and service availability. In this work, we present an Energy-Efficient Collaborative and Opportunistic Positioning System (ECOPS) for heterogeneous mobile devices. An ECOPS facilitates a collaborative environment where many mobile devices can opportunistically receive position information over energyefficient and prevalent WiFi, broadcasted from a few other devices in the communication range. The position-broadcasting devices in an ECOPS have sufficient battery power and up-to-date location information obtained from an accurate but energy-inefficient GPS. A position receiver in an ECOPS estimates its location using a combination of methods including received signal strength indicators and 2D trilateration. Our field experiments show that an ECOPS significantly reduces the total energy consumption of devices while achieving an acceptable level of location accuracy. An ECOPS can be especially useful for unique resource scarce, infrastructure-less, and mission critical scenarios such as battlefields, border patrol, mountaineering expeditions, and disaster area assistance.