Localization in wireless sensor networks under non line-of-sight propagation

This paper addresses ranging in indoor quasi-static sensor environments and presents a time-of-arrival (TOA) based ranging algorithm. A statistical model of the multipath channel in the form of the signal return and noise characterization is derived, and utilized to distinguish signal components from noise. The algorithm then uses multiple signal receptions at each base station, to differentiate between line-of-sight (LOS) and non-LOS components, and to accurately estimate the position of the LOS component in the received multipath signal. The location is estimated through a mathematical programming problem formulation. Using a synthesized bandwidth of 2 GHz, a 4-bit analog-to-digital converter (ADC) and with 5-10 dB signal-to-noise ratio (SNR), range estimation with sub-meter accuracy is achieved. Furthermore, the associated range estimation error does not increase with increase in the transmitter-receiver range