Research On Synchronization Algorithms In OFDM System

Orthogonal Frequency Division Multiplexing(OFDM)has become the key technique in broadband wireless access and the next generation mobile communication system. Extensive attentions have been paid to OFDM due to its high spectral efficiency, high data rate and well anti-multipath ability. It is important for OFDM system to obtain accurate symbol timing and carrier frequency synchronization, and now synchronization in OFDM has become a hotspot in the research of modern communication.The primary content of this thesis is the synchronization algorithms of the OFDM system. At first, the mathematic principle and the properties of OFDM are described. Then the key technologies and the necessary elements of the system are introduced. This thesis analyzes some influences on the performances of OFDM digital communications, which include carrier frequency offset, symbol timing offset and sampling clock offset. Many kinds of synchronization algorithms are discussed in detail, such as the cyclic prefix based and training symbol based joint symbol timing and carrier frequency synchronization algorithms. The complexities and the performances of multiple estimators using cyclic prefix are discussed, simulation results are given and several conclusions are made. Lastly, based on the classical training symbol aided Schmidl synchronization algorithm, some improved symbol timing and carrier frequency synchronization algorithms are proposed. The system simulations and performance analyses are made to each algorithm.