Abstract

The performance of a Universal Mobile Telecommunication System (UMTS) base station RAKE receiver is largely dependent on the accuracy of the estimate of the time-delay of the different paths. A commonly employed technique in a RAKE receiver is to use a multi-path searcher (MPS) to find the number of different strong paths and the time-delay of these paths. The drawback of the existing MPS algorithms for UMTS base-station RAKE receiver is that their computational complexity is high or the probability of detection is low. The full search with full contribution MPS gives the best result in terms of the detection probability, but its complexity is high. To reduce the complexity, a full search with partial contribution MPS has been proposed, but the detection probability of this algorithm is low. In order to solve this problem, in this thesis, a two-stage MPS, based on a dual-dwell technique is proposed. In the proposed algorithm, all the delay offsets in the search window are first evaluated for possible true paths by using only part of the slots in the correlation period. This helps to quickly narrow down the number of search candidates with only a small amount of computation needed. Then, in the second stage, the M strongest candidates from the first stage are further evaluated by using all the slots in the correlation period. The simulation results show that the proposed algorithm has a detection performance very close to that of the conventional full search with full contribution MPS, while at the same time it has a substantially lower computational complexity