Research On The Fast Acquisition Techniques Of MC-CDMA Mobile Communication Systems

Recently, techniques of mobile communication systems are developing very quickly. Now CDMA is very mature and becomes the key technique of the third-generation mobile communication systems. More and more attention is paid to the technique of multi-carrier. MC-CDMA is combination of OFDM and CDMA, thus advantages of both techniques are exploited. Synchronization acquisition technique is one of the most important techniques in any communication systems. In MC-CDMA system, we exploit multi-carriers to transmit high-speed data, which is sensitive to the errors of synchronization, so synchronization is important, especially fast acquisition. Due to the multi-carrier transmission technology used in MC-CDMA systems, almost all the previous synchronization algorithms in MC-CDMA systems are derives from that in OFDM systems. They are suitable for OFDM systems, but they are not optimal for MC-CDMA systems. The data symbols transmitted in MC-CDMA systems have form of CDMA signal, which is greatly different from normal binary signal. The correlation properties of PN sequence are widely used for synchronization in conventional CDMA systems, and corresponding synchronization algorithms are very mature by now, so a new synchronization technique based on the correlating properties of PN sequence is discussed in this paper, in which synchronization may be performed after OFDM deframe and before FFT conversion in order to make full use of transmitted CDMA signal structure. This paper discusses the acquisition techniques based on the correlating properties of PN sequence in MC-CDMA system. It carries out comprehensive analysis of the acquisition principle and methods.