On the Benefit of Observing Signals of Opportunity in Mobile Radio Positioning

Abstract:
In this paper we evaluate the achievable gains for mobile terminal positioning with 3GPP-LTE when observing signals of opportunity. For that we calculate the Cramér-Rao lower bound for pseudo range estimation based on 3GPP-LTE positioning reference signals and for multiple terminal positioning taking into account signals of opportunity with unknown transmitter position. We show that at least four mobile terminals are required in order to benefit from observing such signals of opportunity. When comparing the Cramér-Rao lower bounds for different environments and different numbers of mobile terminals and observed signals of opportunity with the respective reference configurations without signals of opportunity, we can significantly improve positioning performance, especially indoors, where we suffer from lower received power levels compared to an outdoor environment. By observing 4 signals of opportunity, such as WiFi access points, with 10 mobile terminals indoors, we observe an improvement in positioning performance of ˜ 70%.