ML time delay estimation in a multipath channel

In this paper a receiver based on the maximum likelihood (ML) method for estimating unknown parameters of a periodic signal in a multipath channel is presented. In an AWGN channel the ML-receiver reduces to the matched filter followed by a calculation of the ML-metric. A particular interest of this paper lies in time delay estimation which is crucial in spread spectrum radiolocation systems. Performance difference between the obtained ML-receiver and the conventional receiver (the matched filter followed by an envelope detector) in a multipath channel where temporal separation of multipath components is less than one chip interval is investigated by simulations. As excepted, the ML-receiver outperforms the conventional receiver if SNR is high enough, i.e., above the treshold SNR of the ML-receiver.