Sequential Monte-Carlo approximation to the ML time-delay estimator in a multipath channel

In direct-sequence spread-spectrum (DS-SS) based navigation systems, multipath can seriously degrade synchronization performance causing time delay and code phase estimates to deviate from the actual value. These biases depend on the relative amplitudes and delays of multipath replicas with respect to the direct signal. The error in the estimated position due to multipath, when using a standard Delay Lock Loop, can be on the order of several tens of meters, which constitutes a critical aspect in high-precision applications. This paper presents a Sequential Monte Carlo based algorithm which tries to iteratively attain the ML estimate of synchronization parameters of the direct signal and multipath replicas.