| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 90 === Direct sequence/Code-Division Multiple Access (DS-CDMA) has been shown to be a promising technology for future wireless communication systems. Code synchronization plays a very important role of CDMA system. Code synchronization is usually achieved in two steps, i.e., acquisition and tracking. There exist several search strategies for acquisition: serial search, parallel search and hybrid search.
There are two methods commonly employed in serial search and hybrid search technique: single dwell and multiple dwell (mostly double dwell). The double dwell search method is superior to single dwell search method in acquisition performance when input SNR is relatively good. While single dwell search method outperforms double dwell search method in acquisition when input SNR is poor. Since input SNR is closely related to the number of users accessing the CDMA system, and it is always pursued fast acquisition in a CDMA system, it is therefore desired to have a code synchronizer that can achieve rapid code acquisition in both peak and non-peak hours. To this end, A hybrid-dwell code search scheme employing both single and double dwell search methods was proposed specifically, single dwell search is adopted when input SNR is poor while double dwell search is applied when input SNR is relatively good. This thesis will simulate and analyze the acquisition performance of the proposed code acquisition scheme.
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