Frequency Controlling and Synchronization in OFDM Communication System

Research and development are taking place all over the world to define the next generation of wireless broadband multimedia communications systems that may create "the global information village". This system is expected to provide its users with customers' premises services that have information rates exceeding 2 Mbps. The most suitable modulation choice seems to be orthogonal frequency division multiplexing (OFDM) as a special case of multicarrier (N) transmission where a single data stream is transmitted over a number of lower rate subcarriers. One of the main reasons to use OFDM is to increase the robustness against frequency selective fading because in fact there is no intersymbol interference (ISI) at all if a long enough cyclic prefix (CP) is included. This effectively simulates a channel performing cyclic convolution, which implies orthogonality over dispersive channels. In this paper, the research and development on OFDM is reviewed. Then, the basic principles, performance and implementation of OFDM are examined. Analysis is given to enable the selection of key elements for meeting the constraints of the required application