In dense multipath channels

rapid acquisition of Ultra Wideband (UWB) signals is a crucial problem due to very high pulse rate and extremely low per-path energy.This paper presents a two-stage acquisition scheme to improve acquisition performance in the Impulse Radio UWB systems.Specifically

two kinds of sub-optimal maximum-likehood criteria are proposed for a coarse search.Then

a maximum/threshold-crossing criterion is employed for a fine estimation within the obtained limited region.The probability of acquisition is redefined from the view of energy capture that may guarantee expected system performance after acquisition.The impact of captured energy on system performance

as well as

the selection of criterion parameters are evaluated and analyzed in terms of simulation.