Reseach On Carrier Synchronization In OFDM Systems

With the development of modern communications technology, wirelessmobile communications have been widely applied in our lives. Experiencedfirst-generation and second-generation, wireless mobile communication havecompleted the transition from analog to digital technology. Currently, mobilecommunication technology is making the transition from the third generation tothe fourth generation. Because of the outstanding ability of against multipathfading and narrowband interference, OFDM technology receives more and moreattention. Now it has becoming the interesting topic of the communicationtechnology. Combined with multiple access technology, OFDM technology canprovide the flexible, high-quality and high-speed data transmission services; Butit also has many drawbacks, such as sensitive for time and frequencysynchronization error, easily generating a large peak to average power ratio andso on.In this paper, the emphasis is the carrier synchronization in OFDM systems.The basic feature of the radio channel is discussed, just as multipath effects, timevariability and fading effects, so are the basic theory of OFDM system and its keytechniques. And then we study the synchronization in OFDM technology and avariety of synchronization error on the system performance. The purpose ofsymbol synchronization is to determine the starting position of the OFDM symbol,so that the receiving end can perform digital demodulation from the correctposition. The purpose of carrier synchronization is to realize the coherentdemodulation at the receiver. The purpose of sampling clock synchronization is tokeep sampling frequency consistency between the receiver and the transmitter.Our final focus is on the carrier synchronization in the OFDM synchronizationtechnology.In particular, we introduce several typical carrier synchronization algorithmwith auxiliary data, and give a brief analysis of their performance. Compared toblind estimation algorithm, bandwidth efficiency of data-aided algorithm is lower.We carry out the simulation for the existing blind estimation algorithm, andanalyze their performance. Finally, in order to improve the performance of blindestimation algorithm, pre-whitening technology is introduced. Through thesimulation experiments, the performance of the estimation algorithm for carrierfrequency offset with the pre-whitening technology is improved significantly, solve the estimation of carrier frequency shift in the case of color noise.