Study And Implementation Of OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) is a Multi-Carrier Modulation technique with high performance. It has attract extensive attention in resent years due to its good performance in wireless mobile communication system, such as its robustness to multi-path delay spread, its high data rate transmission capability with high bandwidth efficiency. In the OFDM system, the system bandwidth is divided into many sub-channels, a high rate data stream is separated into a number of lower rate streams that are transmitted simultaneously through these sub-channels.The basic theory, advantages and disadvantages of OFDM technology are described in this thesis at the beginning. The importance of synchronization in OFDM system is discussed, and the effect, which is caused by synchronization error, to performance of OFDM systems is analyzed, then the classic data-aided synchronous algorithm, based on training symbol, Schmidl & Cox (SC) algorithm is studied in details, Park and Minn methods, which improve the SC method, are also discussed. On this basis, a new scheme of training symbol is proposed for time and frequency offset estimation. Simulation and mathematical analysis to the new scheme,SC scheme and park scheme are presented in this thesis, and the results show that the new method has good performance for time offset estimation, and can expand the range of frequency offset estimation. At last of this paper, the specific realization of the OFDM system based on standard C language is explained.