Design and performance of ultra-wideband acquisition systems

The acquisition of ultra-wideband(UWB)signals is a potential bottleneck for system throughput in a packet-based network employing UWB signaling format in the physical layer. The problem is mainly due to the fine time resolution and the low received signal power which forces the acquisition system to proces the signal over long periods of time before getting are liable estimate of the timing of the signal. In this dissertation, we focus on the development of more efficient acquisition schemes by taking into account the signal and channel characteristics. The presence of dense multipath in the UWB channel suggests the presence of multiple acquisition states which could be exploited to speed up the acquisition process. In this dissertation, we give a precise characterization of the set of phases in the uncertainty region where a receiver lock can be considered successful acquisition. We call this set of phases the hit set. We design and compare the performance of two schemes for the acquisition of time-hopping UWB signals which attempt to exploit the energy in the multipath to improve the acquisition performance. We prove a general result characterizing the asymptotic performance of threshold-based acquisition schemes in multipath fading channels. We use this result to characterize the performance limits of the aforementioned UWB acquisition schemes. We then consider the problem of finding efficient search strategies when there are multiple elements in the hit set. We use the insights gained in the design of UWB acquisition schemes in the development of efficient schemes for the closely related problem of time-of-arrival estimation.