Direct Position Determination Using TDOA and FDOA Based on Variable Baseline

The localization of a stationary transmitter using several moving receivers is considered in the observation time. It is assumed that the transmitted radio signal is random with known statistics. The conventional approach is based on two steps. In the first step the time difference of arrival (TDOA) and frequency of arrival (FDOA) are measured and in the second step these measurements are used for geolocation. The two step methods are not guaranteed to yield optimal location results since in the first step the differential delay and differential Doppler estimates are obtained by ignoring the constraint that all measurements must be consistent with a geolocation of a single point emitter. Considered this problem, Weiss advocate the direct position determination (DPD) method that proves to be more precise for weak signals than the conventional approach. However, the two algorithms satisfies this constraint, which the difference of receivers' position and TDOA/FDOAs can be ignored. So, these algorithms divided long-time accumulation into several short signal segments. Results demonstrated by Monte Carlo simulations that the proposed method is superior to two step methods and traditional DPD for low signal to noise ratio and long-term observation time interval.