| In modern society, people's requirement of the wireless transmission rate and stability is gradually increasing. MC-CDMA combines the advantages of OFDM and CDMA technology. Then it has became a hot issue in the field of wireless communications at present. MC-CDMA is good at bandwidth efficiency, strong anti-interference ability of ICI and ISI, high speed data transmission, has been the key technology of 4G. But MC-CDMA also retains the defects of OFDM and CDMA technology. Especially it is sensitive to the frequency offset between transmitters and receivers caused by Doppler effect. The mismatch caused by local oscillator may affect the signal transmission seriously. How to keep the synchronized symbol from transmitting to receiving ends has became a primary problem to be solved. The paper discusses how to accurately estimate the starting point of the symbol synchronization.At first, the paper has a brief review of the development of mobile communication, introduces characteristics of wireless channels and concepts of spread spectrum communication, then compares three plans of combined technology, and has a introduced of MC-CDMA, introduces three kinds of synchronization in MC-CDMA, discusses the symbol synchronization emphatically. Then analyzes and simulats two classic kinds of synchronization algorithms widely used at present, arrives at advantages and disadvantages of the maximum likelihood estimation based on cyclic prefix and PN sequence synchronization algorithm. Then improves the correlation of PN sequence synchronization algorithm. By the way of inserting PN sequences in frame heads, changes the structure of the frames to achieve precise estimation of the starting point by PN sequence as a cyclic prefix. The new algorithm improves the accuracy of the synchronization estimation, cuts down the tracking time and greatly reduces the complexity of the algorithm. |
PDF Full Text Request