Direct position determination of multiple radio signals

The most common methods for localization of radio signal emitters are based on measuring a specified parameter such as signal angle-of-arrival (AOA) or time-of-arrival (TOA). The measured parameters are then used to estimate the transmitter location. Since the measurements are done at each base station independently, without using the constraint that all AOA/TOA estimates must correspond to the same transmitter, they are sub-optimal. Moreover, if the number of array elements at each base station is M, the number of cochannel simultaneous transmitters that can be localized is M-1. We propose a technique that uses exactly the same data as the common AOA/TOA methods, but the position determination is direct. The proposed method can handle LM-1 cochannel simultaneous signals, using L base stations. Although there are many stray parameters, only a two-dimensional search is required for a planar geometry and a three-dimensional search for the general case. The technique exploits the principles of the MUSIC algorithm, and provides a natural solution to the measurements-sources association problem that is encountered in AOA/TOA based systems.