Anthony J. Weiss, and Alon Amar

The most common methods for position determination of radio signal emitters, such as communications or radar transmitters, are based on the measurement of specified parameters, such as angle-of-arrival (AOA) or time-of-arrival (TOA) of the signal. The measured parameters are then used to estimate the transmitter s location. The measurements are done at each base station independently, without using the constraint that the AOA/TOA estimates at different base stations should correspond to the same transmitter s location. This is a suboptimal location determination technique. Further, if the number of array elements at each base station is M, and the signal waveforms are unknown, then the number of cochannel simultaneous transmitters that can be localized by AOA is limited to M ? 1. Most AOA algorithms fail when the sources are not angularly separated very well.

We propose a technique that uses exactly the same data as the common AOA methods, but the position determination is direct. The proposed method can handle more than M ? 1 cochannel simultaneous signals. Although there are many stray parameters, only a two-dimensional search is required for a planar geometry. The technique provides a natural solution to the measurements-sources association problem that is encountered in AOA-based location systems. In addition to new algorithms, we provide analytical performance analysis, Cram r-Rao bounds, and Monte Carlo simulations.