Overview

We focus on the tradeoff between energy consumption and localization performance in a mobile sensor network application. Our approach is to combine GPS location with more energy-efficient location sensors to bound position estimate uncertainty in order to prolong node lifetime. The target application is outdoor location monitoring for tracking cattle using smart collars that contain wireless sensor nodes and GPS modules, as shown in the Figure below [1]. We use empirically-derived models to explore duty cycling strategies for maintaining position uncertainty within specified bounds. Specifically we explore the benefits of using short-range radio contact logging alongside GPS as an energy-inexpensive means of lowering uncertainty while the GPS is off. Results show that GPS combined with radio-contact logging is effective in extending node lifetime while meeting application-specific positioning criteria. Node Energy Profile The total time during which the GPS can be powered off while guaranteeing an error threshold is: AAU: absolute acceptable uncertainty S: speed Tlock: GPS lock time Ugps: GPS module erro