Research On Carrier Synchronization In OFDM Systems

Orthogonal frequency division multiplexing(OFDM) is a multi-carrier modulation technology.The new 4G air interface has a common feature which is based on OFDM technology.OFDM wireless communication system has been the most popular modulation technique. Compared to conventional single-carrier modulation technique,OFDM has a higher spectral efficiency and stronger anti-jamming capability. More and more people pay attention to it.But OFDM has its own shortcomings.It is very sensitive to Carrier Frequency Offset(CFO)which can destroy the orthogonality between sub-carriers and then deteriorate the performance of OFDM system,which will result in great reduction in the performance of the received signals and can not reflect the advantages of OFDM technology.This paper studies the carrier frequency offset estimation algorithm for OFDM systems,and focus on seeking low complexity and relatively good performance of the carrier frequency offset estimation algorithm.This paper discusses several typical estimate algorithms of CFO,such as data-aided estimation algorithms and non-data-aided estimation algorithm.We compare their performance based on simulation results.First,introduction of fundamental principles,structure and system model,characteristics of OFDM system.Second,Analysis of symbol timing offset,sampling timing offset and carrier frequency offset of OFDM system,with the focal point of their influence on OFDM system. Third,analyze the data-aided algorithm(Sch-Cox estimation) and non-data-aided algorithm(MUSIC-Like estimation and ESPRIT-Like estimation),compare the performance of them detailedly,and propose a p improved algorithm which does not require the use of additional training symbols, and the sequence of training frames designed to be a real pseudo-random (PN) sequence, can greatly simplify the estimated complexity of the algorithm. Even in the multipath channel, it still has a good frequency offset estimation range and timing estimation performance, which can be applied to a real system.