| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 89 === The purpose of this thesis is to design a fast PN code acquisition detector to rapidly achieve initial synchronization between locally generated PN code and the received PN code in a direct-sequence spread-spectrum (DS-SS) code division multiple access (CDMA) system.
There are two methods commonly employed in serial 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 DS-SS 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, this research proposes a mixed mode code synchronizer employing both single and double dwell search methods in which 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 analyze the acquisition performance of the proposed code acquisition scheme in terms of SNR, detection probability and false alarm rate.
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