Study On Cell Search Algorithm Of FDD-LTE System

3G technology has promoted the rapid development of mobile communication and it has changed people’s way of living and working to some extent. However, with the raising demand for mobile communication, 3G technology has been unable to meet the needs of the people. Then the international organization for standardization of 3GPP proposed a long term evolution(LTE) program. LTE features supporting two modes of FDD and TDD and introducing OFDM and MIMO to achieve some purpose of decreasing system delay, enlarging system coverage and capacity and increasing transmission rates.LTE cell search is the first physical layer process when mobile devices access to the cell. The cell search performance affects the subsequent communication process directly, thus the LTE cell search has become a research focus in recent years. Cell search is mainly divided into two stages of acquisition and tracking and this paper mainly focuses on the acquisition stage of cell search.LTE cell search aims to achieve the synchronization of downlink timing and frequency, which comprises the following steps: firstly the primary synchronization signal is detected to obtain the 5ms timing and the ID within cell group, and then frequency offset is estimated and compensated to eliminate the effect on system. Thirdly the 10 ms timing and cell group ID are obtained by the detection of secondary. In the end the ID within cell group and cell group ID are combined to get a complete physical cell ID.This paper analyses some important processes in cell search and related algorithms. With the respect of the detection of PSS, the paper studies several common synchronization algorithms and summaries their advantages and disadvantages based on the performance discussion. The results shows that M-part algorithm adopts the methods of segmentation on the base of traditional cross-correlation algorithms, which improves the performance of resisting frequency offset with the expense of decreasing the performance of resisting noise. Therefore traditional cross-correlation algorithms have a better performance of resisting noise and M-part algorithm can effectively frequency offset. This paper summaries the mentioned algorithms’ advantages and disadvantages and then improved them aiming to enhancing the performance of resisting noise and frequency offset. The paper also discusses the detection of SSS, analyzing two kinds of secondary synchronization signal detection algorithms and comparing their performances. The results indicate that current secondary synchronization signal detection algorithms all have a relative higher complexity. So this paper improves the traditional algorithms with the respect of decreasing complexity.In the last simulations for the improved algorithms and traditional algorithms are done in AWGN and multipath channel environments. The result shows the performance of improved primary synchronization signal detection algorithm has improved greatly in resisting noise and frequency offset. And The improved secondary synchronization signal detection algorithm and the traditional algorithm have the same performance under the condition of decreasing complexity.