On equal-gain combining for acquisition of time-hopping ultra-wideband signals

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 low received signal power and the fine time resolution which forces the acquisition system to process the signal over long periods of time before getting a reliable estimate of the timing of the signal. Hence, there is a need to develop more efficient acquisition schemes by taking into account the signal and channel characteristics. In this paper, we investigate two approaches, the square-and-integrate and the integrate-and-square, which collect the energy in the multipaths by performing equal-gain combining (EGC) to improve the acquisition performance. We define the hit set as the set of hypothesized phases which can guarantee adequate system performance after acquisition, and also study the effect of the EGC window length on the acquisition performance.