Research And Simulation On Synchronization Algorithms For OFDM System

Orthogonal frequency division multiplexing (OFDM) is considered as one of the key technologies of the future of communications,3GPP LTE Organization has been adopted it as the key technology of the downlink.However,OFDM is very sensitive to synchronization error, the multi-antenna OFDM system is also very sensitive to the synchronization error,because the timing offset and frequency offset will cause serious inter-symbol interference and inter-Carrier Interference,so that the accutate synchronization for OFDM systems is essential.This thesis mainly researches the physical layer synchronization algorithms of OFDM. First i introduce the basic principle of OFDM system and channel characteristics,and analyze the impact of the time and frequency offset to the system performance,it shows the importance of synchronization.This thesis analyzes and simulates the synchronization algorithms of the single antenna OFDM system firstly.To analyze and simulate the classic ML algorithm based on cyclic prefix and blind estimation algorithm,then to analyze and simulate two classical joint time-frequency synchronization algorithms based on training symbols,Schmidl algorithm and GR algorithm.Finally,the algorithms based on training symbols were divided into two parts,the timing estimation algorithms and the frequency offset estimation algorithms,these were analyzed and compared the simulations.Among them, he timing estimation algorithms mainly analyzed and compared Schmidl,M&B algorithm,P&C algorithm and GR algorithm;Frequency Offset Estimation Algorithm mainly analyzed and compared the Schmidl algorithm and Morelli algorithm.Finally,this thesis then studies the centralized MIMO-OFDM system synchronization algorithms.First introduces several classical MIMO-OFDM synchronization scheme of centralized systems,this thesis gives a centralized system of time-frequency synchronization scheme,and analyzes the simulation,The basic idea is to combine the schmidl algorithm of single antenna and the conjugate symmetric idea,and extend it to the multiple antenna system,The simulation results show good synchronization performance. Finally, this thesis gives a simple synchronization scheme based on IEEE802.16d preamble structure,the simulation result shows that the synchronization performance is better.