Acquisition Scheme for DS-UWB with Combined Spreading Sequence

In direct-sequence ultra-wideband (DS-UWB) systems, long spreading sequences are used to span multiple symbol intervals in order to remove spectral lines and to mitigate multiple access interference. The usage of long spreading sequences and the fine timing resolution will result it? a large search space during acquisition stage. As a result, the DS-UWB system will need a lot of time to achieve acquisition state. In this paper we propose an improved signaling format in which the final long spreading sequence used is derived from the combination of two short sequences. According to the feature of the proposed signaling format, a two-stage acquisition scheme is proposed and studied in detail. Analytical and numerical results show that the acquisition time can be reduced greatly with the proposed scheme.