Research On The Key Techniques Of OFDM System

Due to its high band-width efficiency, its robustness to multipath and pulse, its high transmission speed and its ability of flexible modulation on subcarriers in accordance with the channel conditions, Orthogonal Frequency Division Multiplexing (OFDM) has found its wide applications in high speed data transmission wireless systems, such as digital video broadcast, digital television, wireless local area network and will play a key role in the forth generation mobile communication systems. The main defects of OFDM system are high Peak to Average power Ratio (PAR) characteristics and sensitive to synchronization errors. Therefore, it must be of good theoretical and practical value to conduct research on these two key problems.In this dissertation, the high PAR and synchronization systematically and thoroughly are researched based on the analysis of the theory of OFDM technology, and several solutions are proposed and verified through numerical simulation.Two kinds of methods are studied in this dissertation to deal with the high PAR problem. One is coding methods, the other is signal scrambling code techniques. Based on the theory of simple block coding and the technique of subblock partition, one modified simple block coding of PAR reduction for OFDM is proposed. The new scheme can effectively reduce the PAR of OFDM signal with larger subcarriers and achieve arbitrary coding rate at the same time. An extended complement block coding and modified complement block coding scheme are proposed based on the complement block coding method. Extended complement block coding can get better PAR reduction performance through finding the optimum location from all the possible locations of complement sequence. Compared with complement block coding, modified complement block coding can achieve about another 0.5dB reduction of PAR through...