Study On Time And Frequency Synchronization In OFDM System

As a new generation of wireless communication modulating technology, the Orthogonal Frequency Division Multiplexing (OFDM) technology has a characteristic of anti-multi-diameter fading and the high use factor of the frequency spectrum, it is the most popular core technologies in 4G communication system right now.In the last few years, OFDM has already obtained widespread application in following fields, digital audio broadcast(DAB), digital video broadcast(DVB),asymmetrical digital subscriber line(ADSL) and IEEE802.11a wireless confined network standard and so on. OFDM technology is an multi-carrier transmission technology, dividing the high speed transmission data stream into many low speed transmission data streams, and using the individual carrier transmission to transfer these low-speed data streams. It has communication merits as follows, the high use factor of the band width, reducing the disturbance, the enhancement security, reducing multi-way attenuation and so on. However, OFDM system is very sensitive to synchronous errors, especially the frequency offset. This is one of the major defects in OFDM system. A very small frequency offset will lead to degeneration of the system performance dramatically. The prerequisites of normal work of OFDM system are the precise time synchronization and the accurate frequency synchronization.This paper which aiming at the problems of time and frequency synchronization in OFDM system has conducted comprehensive and thorough research. First, It is introduced from the system model and basic principles of the OFDM technology; and introducing the basic principles of OFDM system and analyzes the influence of the timing offset and frequency offset to the OFDM system performance; then it discusses the principle of OFDM synchronization technology, making an overview of OFDM system synchronization method; it focuses on the principle of the data assisted classical algorithm-SC algorithm and the non-data-assisted classical algorithm-ML algorithm, giving a block diagram on the algorithm, and using a large number of simulation experiment to study timing synchronization and frequency offset estimation performance of the ML and SC algorithms based on MATLAB simulation platform; aiming at the SC algorithm's platform effect. This paper presents an improved algorithm, transiting the contrast experiments with the SC algorithm, proving that this algorithm has an more obvious effect on improving the platform effect. Finally, the article concludes full text's work and points out the direction of the further work.