Two-stage acquisition for UWB in dense multipath

In UWB acquisition in dense multipath environments, there exist multiple delays (or cells) within the timing uncertainty region that can lead to an acquisition lock, due to UWB's fine time resolution. Most acquisition schemes tire designed to lock onto an arbitrary multipath, or onto the strongest multipath. This is especially undesirable for ranging applications, since it is critical to capture the LOS path. In this paper we propose a two-stage acquisition algorithm for UWB ranging applications. The first stage, called coarse acquisition, is a fast version of traditional serial search, which locks onto an arbitrary multipath component. The second acquisition stage performs a finer search over a reduced uncertainty region. The fine acquisition stage uses an estimate of the noise variance, obtained from the first stage. It also takes advantage of the clustered nature of the multipath to detect the LOS path, even when it is severely attenuated. The gains brought by the proposed model are verified by simulation.