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Performance Analysis of 3-Stage Cell Search Process in wCDMA System
Abstract
In this paper, we study the performance benefits of cell search algorithm. The purpose of the cell search algorithm in UMTS is to estimate the spreading code of the serving base-station and its corresponding timing offset. The search procedure consists of 3 sequential and distinct stages: (1) slot-boundary synchronization, (2) frame-boundary synchronization with code-group identification, and (3) scrambling code identification. Also, we study the performance benefits of estimating multiple “code-time” hypotheses in each stage of the cell-search process. In addition, we also study the effect of oversampling and non-ideal sampling. Our results indicate that, in the presence of non-ideal sampling, performance improves significantly if the received signal is oversampled by a factor of 4 or more. We also show that an estimating 4 “codetime” hypothesis instead of 1 in the cell-search stages reduces the search-time (i.e. the code-acquisition time) considerably, in particular at low SNR. The Improved CSD proposed in this paper aims to achieve faster synchronization between the mobile station (MS) and the base station (BS) and thus improves system performance. Also has lower hardware utilization when compared with the 3GPP-comma free CSD scheme under the same design constraints.
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