Multipath resolution with PN chip interval

If the delay between two multipaths is about a chip interval and the path strength is almost equal, then the envelope tracking (ENV) scheme of A. Baier et al. (see IEEE JSAC, vol.12, no.4, p.733-43, 1994) performs poorly. This is because only a single peak is observed in the envelope of the correlation function (or multipath power delay profile) and the peak position is about half a chip interval away from the two true multipath delays. Also, the envelope tracking with subtraction (ENV-SUB) scheme of E. Sourour et al. (see Proc. IEEE 49th VTC, p.422-6, 1999) regards the channel in this situation as a three-path channel and generates incorrect delay estimates. K. Han et al. (see ICC, 2001) proposed a heuristic multipath searcher for this situation. We propose a multipath searcher with a chip time resolution for such a two-path channel with near-equal strength, based on the maximum likelihood (ML) principle. In addition, the paper presents the detection probability that a two-path channel decision is made when the channel has two paths truly, given that the multipath delay power profile shows a single peak. The analytical results are compared with those of Han et al.