| In order to occupy a favorable position in the future competition of the mobile communication, the 3GPP has designed the LTE standard. The multiple access technology of LTE is based on OFDM technology. The OFDM system has high spectral efficiency, high data rate, low implementation complexity, it is the downlink transmission technology of LTE. The uplink multiple access technology of LTE use the SC-FDMA technology, comparing with OFDMA technology, it has a lower peak-to-average power ratio. OFDM is very sensitive to carrier frequency offset and time-varying channel, Carrier frequency offset would destroy the orthogonality of the subcarriers and cause interference between subcarriers. Therefore, synchronization technology is crucial to the OFDM system.Before the LTE base station and the terminal can communicate, first of all, it need to be cell search. First find and get the synchronization of cell with LTE network, then receive and decode the cell system information in order to communicate in the cell.When the system information correctly decoded, the terminal can access cell with random access process. The cell search begins in the terminal accessing cell and cell switching, detect downlink synchronization signal. With the cell search, the terminal can determine the time and frequency parameters. Random access is used for the terminal to initial registration and resources bandwidth application, establishing the uplink synchronization. This paper also introduces the random access process in TD-LTE uplink. It has analyzed the detection principle and algorithm of the preamble sequence in random access, has set up a simulation link for preamble sequence detection,simulated and analyzed the relevant algorithms. At last it has completed the design and implementation of the preamble sequence detection with FPGA.Chapter one briefly introduces the current development of mobile communication and the research background, and the key technologies of LTE. It also introduces the method of cell search in downlink and random access in uplink, determine the structure of this paper.Chapter two describes the basic principle of OFDMA and SC-FDMA in TD-LTE.First it introduces the frame structure of TD-LTE, the time-frequency mapping and the physical layer channel. Then it analyzes the effect of timing and frequencysynchronization error on OFDM system and introduces the primary synchronization signal(PSS) and the secondary synchronization signal(SSS) in TD-LTE downlink,including its generation and time-frequency mapping. At last, it discussed two kinds of random access, the time-frequency structure, and four kinds of preamble sequence format.Chapter three studies on the process and algorithm of cell search. It studies the detection algorithm based on the primary synchronization signal and cyclic prefix type.Then this chapter builds the simulation link with MATLAB, and compares the performance of different algorithms.Chapter four studies the random access in uplink, introduces the method for generating preamble sequence, the detection principle of time domain and frequency domain, two kinds of detection algorithms, and the setting of threshold. Finally,according to the system, it builds the simulation link of preamble sequence detection,analyzes the performance of the algorithms.Chapter five completes the design and implementation of the preamble detection with FPGA. This chapter designs the overall module based on the preamble detection in frequency domain algorithm, analyzes the functions of several sub modules. Finally, it completes the simulation of preamble detection, and achieves the functional testing of FPGA in the system development platform.Chapter six is the summary of the whole thesis, and prospects the future research direction. |
