Research On Pilot-assisted OFDM Sampling Frequency Synchronization Algorithm

With higher requirement of future wireless communication system and development ofnew technology, more and more new technologies have come into our vision. As the maintechnology of the3G and4G, Orthogonal Frequency Division Multiplexing technology hasbeen applied widely. Moreover, it has been studied in the field of Underwater Acoustic(UWA) communication at home and abroad. Meantime, since synchronization error wouldseverely influence the system performance, synchronization is a key technology of OFDM.Only when the synchronization problem has been solved properly can the advantage ofOFDM technology be achieved. So we will study the sampling synchronization in this paper.This paper investigates the pilot-assisted estimation of sampling frequency in OFDMsystem. Firstly, we introduces the basic principle of OFDM, three kinds of synchronizationtechnologies, including timing synchronization, frequency synchronization, samplingfrequency synchronization, and their influence to the system. Secondly, four samplingfrequency algorithms have been described in detail, includes the joint pilot-assistedestimation of carrier frequency offset and sampling frequency offset and traditionalestimation method of the sampling frequency. Then the four algorithms have been simulatedby using the MATLAB software. The results show that, the joint one is more complex and theothers have bad performance as the less pilots used.Therefore we propose an improved sampling frequency algorithm. It takes advantage of allpilots and their cross-correlations to estimate the sampling frequency error. In this way,simulation result shows that it has lower complexity and a better performance.The joint algorithm and the improved one will be inserted in the system program which ourlab expore to test bit error ratio respectively in this paper. We estimate their samplingfrequency offset and compare their bit error ratio in the system. The results show that, in thecondition of approximate bit error ratio, the improved has lower complexity, thus it has morevalue in the practical system.