Two-Step Data-Aided Acquisition for High Rate DS-UWB Systems

Many acquisition schemes have been proposed and investigated for Ultra-Wideband (UWB) systems, however, most of them setup for low duty-cycle Impulse Radio UWB (IR-UWB) signals, with the assumption that the pulse repetition time is greater than the maximum excess delay of channels, so that intra- and inter-frame interference can be bypassed. This assumption limits the transmission rate and cannot hold in high-rate Direct-Sequence UWB (DS-UWB) systems. In this paper, we propose a two-step data-aided acquisition scheme for high-rate DS-UWB systems. The first step is to quickly acquire an arbitrary train sequence; a two-stage correlation architecture is employed to combat Inter-Symbol Interference (ISI) and collect multipath energy, so as to speed up acquisition. Correspondingly, the second step is to search for the first arriving path with a maximum gap based search method (also new proposed), so as to improve Bit Error Rate (BER) performance. Closed-form expressions of Mean Acquisition Time (MAT), Overall Acquisition Probability (OAP) and False Alarm Rate (FAR) are derived. Based on them, parameter selections that minimize MAT and maximize OAP are discussed under certain FAR constrain. Simulations corroborate our theoretical results.