SPIDER: enhanced distance based localization of mobile radio terminals

In current mobile radio systems the localization of mobile terminals is desirable both with respect to promptly alerting rescue services in cases of emergency, and to offering added value services as for instance piloting the subscribers to places of their personal interest. Mainly all conventional localization schemes which are already in the supply portfolio of the manufacturers apply multilateration based on estimates of the distances of the mobile terminal to be located to a number of surrounding base stations. In this paper a new multilateration based location scheme is proposed, which offers increased accuracy by taking into account not only estimates of the distances between mobile terminals and base stations. but also of the mutual distances between mobile terminals. The new localization scheme resorts to the ML (maximum likelihood) estimation rational. First, it is mathematically described, which leads to a nonlinear optimization problem not accessible to closed form solutions. Then, a low-cost approximate iterative solution to this problem is presented. Finally, the new localization scheme is verified by simulations. The simulation results show a significant accuracy enhancement as compared to the conventional scheme mentioned above.