Mobile Wireless Localization through Cooperation

This paper considers N mobile nodes that move together in the vicinity of each other, whose initial poses as well as subsequent movements must be accurately tracked in real time with the assist of M(≥ 3) reference nodes. By engaging the neighboring mobile nodes in a simple but effective cooperation, and by exploiting both the timeof-arrival (TOA) information (between mobile nodes and reference nodes) and the received-signal-strength (RSS) information (between mobile nodes), an effective new localization strategy, termed “cooperative TOA and RSS” (COTAR), is developed. An optimal maximum likelihood detector is first formulated, followed by the derivation of a low-complexity iterative approach that can practically achieve the Cramer-Rao lower bound. Instead of using simplified channel models as in many previous studies, a sophisticated and realistic channel model is used, which can effectively account for the critical fact that the direct path is not necessarily the strongest path. Extensive simulations are conducted in static and mobile settings, and various practical issues and system parameters are evaluated. It is shown that COTAR significantly outperforms the existing strategies, achieving a localization accuracy of only a few tenths of a meter in clear environments and a couple of meters in heavily obstructed environments. Index Terms mobile localization, wireless localization, user cooperation, maximum likelihood estimation, iterative detection, time-of-arrival, received-signal-strength