When assistance becomes dependence: characterizing the costs and inefficiencies of A-GPS

Abstract

Location based services are a vital component of the mobile ecosystem. Among all the location technologies used behind the scenes, A-GPS (Assisted-GPS) is considered to be the most accurate. Unlike standalone GPS systems, A-GPS uses network support to speed nup position fix. However, it can be a dangerous strategy due to varying cell conditions which may impair performance, sometimes potentially neglecting the expected benefits of the original design. We present the characterization of the accuracy, location acquisition speed, energy cost, and network dependency of the state of the art A-GPS receivers shipped in popular mobile devices. Our analysis is based on active measurements, an exhaustive on-device analysis, and cellular traffic traces processing. The results reveals a number of inefficiencies as a result of the strong dependence on the cellular network to obtain assisting data, implementation, and integration problems.