The Research In Synchronization Technology In OFDM Systems

Future mobile communication systems are expected to provide high-quality broadband services using the minimum possible resources (power, bandwidth, complexity). Toward this end, an appropriate transmission technique that matches the channel characteristics is required. Orthogonal frequency-division multiplexing (OFDM) is one of the promising techniques that meet such requirements with reasonable complexity. It has recently achieved much popularity due to its desirable properties, such as its robustness to multi-path delay spread, its high data rate transmission capability with high bandwidth efficiency, and so on.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 (I nter-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.This paper presents the theory of OFDM technology and a FFT-based OFDM system. Some most important synchronization algorithms for OFDM systems are summarized. Then studies, analysis and compares these synchronization algorithms. 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.