The Research Of The Synchronous Technique Of OFDM System

OFDM (orthogonal frequency division multiplexing) is an appealing modulation technique for high-speed wireless communication system owing to its spectral efficiency and robustness against multipath fading. In the OFDM system, the whole system bandwidth is divided into many sub-channel with narrow bandwidth and bandwidth efficiency is increased by allowing overlapping of the sub-channels. Moreover, serious ISI (Inter-Symbol Interference) and ICI (Inter-Carrier Interference) can be readily circumvented by introducing CP (Cyclic Prefix) .However, these advantages of the OFDM systems can be only guaranteed when the orthogonality between sub-carrier is maintained. If this orthogonality is destroyed, serious deterioration of system performance may occur due to ICI between sub-carrier. The most critical causes yielding the ISI as well as ICI are symbol timing and carrier frequency offset which are occurred in the OFDM receiver. Hence, synchronization has been a major research topic in OFDM systems for they are sensitive to symbol timing error and carrier frequency offset.Various existing synchronization algorithm to estimate symbol timing offset and carrier frequency offset can be classified into blind and pilot-aided methods and algorithm based on cyclic prefix. This paper mainly studies, analysis and compares some synchronization algorithms using these methods. At the same time, simulations of this algorithms are taken by Matlab. The performance of each synchronization algorithm are shown by simulation result. The main purpose of this paper is to analysis and compare some existing synchronization algorithms and find out their advantage and their best application fields.