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With the accelerated process of social information, the existing second-generation mobile communication system has been unable to meet the people on the diverse needs of the mobile communications business. TD-SCDMA as an independent research and development, with independent intellectual property rights of international mainstream 3G communication standards. It uses a smart antenna, multi-user joint detection, synchronous CDMA series of international advanced digital signal processing technology, with transmit power, spectrum efficiency, easy to support asymmetric data services, etc., plus the huge Chinese market attractive and strong support from the Chinese government, the market with great development potential, has become the focus of research and development in recent years. TD-SCDMA uses TDD (Time Division Duplex) mode, a clock synchronization system that requires strict downlink synchronization, a frequency shared between adjacent cells, on the downlink time slot user data transmission in different time slots, each the cell can be adjusted by adjusting the position of the switching point, the downlink slot number of the current data in order to meet business needs. Cell search refers to the terminal as soon as possible after boot must search for a suitable cell in order to use the network to provide services. Terminal SYNC-DL code by searching establish downlink synchronization with the base station, to obtain the current cell and the adjacent cell information. SYNC-DL code is a system intended 64 PN sequence, the main operations of traditional search algorithm is the received signal with the known preamble sequences do the relevant calculations, the algorithm takes a longer time, high power consumption, to achieve high complexity, therefore can not be applied. Therefore, this careful study of TD-SCDMA physical layer structure, proposed using the frame structure, a characteristic of the search algorithm to achieve coarse synchronization, the synchronization code is a very narrow range of chips, and in this do correlation calculation range, and the use of the downlink pilot time slot synchronization code in the self-correlation and cross-correlation characteristics sentence structure PAPR condition interference judgment, effectively reduces the complexity of the algorithm. Finally, the algorithm is implemented on FPGA and debugging success. Simulation and experimental results showed that: Compared with traditional algorithms, this algorithm is simple, fast, low complexity, high accuracy, and suitable for larger SNR range. Which for some low-cost TD-SCDMA equipment development has important reference value.
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