Research On Synchronization Technology Of OFDM Based On QAM In Time-Varying Channel

With the progress of high-efficiency and high-speed of information transmission, Orthogonal Frequency Division Multiplexing(OFDM) modulation technology has become one of the next generation communication systems and standards. For the OFDM transmissions based on the time-varying channel, there are still many technical bottlenecks. In this thesis, synchronization of OFDM systems based on the time-varying channel is discussed in the following four aspects.Firstly, the paper analyzes the attenuation of the radio channel and effect of synchronization error on the system. In this thesis, the radio channel characteristics in OFDM applications were analyzed, especially the specific effects of various parameters of the multipath channel, and a detailed analysis of two typical fading channel. Then effect of sync errors on OFDM system performance is analyzed. About OFDM systems symbol timing error, carrier frequency error and phase error, sampling synchronization error and sampling clock skew, thesis make a detailed and comprehensive analysis by derivation.Secondly, the paper researchs the typical synchronization algorithm of the OFDM system. Thesis makes a carefully analysis of a variety of typical existing synchronization algorithms, including the S&C algorithm, based on CP algorithm and joint ML symbol timing synchronization algorithm, training sequence methods and typical Moose algorithm for small multiple of the carrier frequency offset estimation. At the same time, research the carrier partial phase synchronization and improved algorithm, the finally make an algorithm analysis about sampling clock synchronization. This chapter compares the performance of various synchronization estimation algorithms, analyze time-varying channel based on the simulation performance of the algorithm under AWGN channel.Thirdly, the paper makes a research on synchronize of the OFDM system under time-varying channel. This chapter first analyze the changes of synchronization algorithm under varying channel, then make improvement strategies for symbol timing synchronization, carrier frequency synchronization algorithm based on the analysis of typical algorithms in the previous chapter. Analysis and simulation results show that these algorithms have better performance to deal with multipath fading and Doppler frequency shift, improved estimation accuracy.Finally, the synchronization algorithms are realized. According to the principle of numerical, this thesis analyze synchronous implementation scheme, and improve the algorithm structure, implement all parts in the optimization of resource consumption; Secondly, in combination with simulation tools such as Matlab, ModelSim, verify the validity of the algorithm.