Research On OFDM Communications System Based On FH

Orthogonal Frequency Division Multiple (OFDM) is the core technology of the fourth generation (4G) of mobile communication. Its biggest merit is resists the frequency selectivity to decline, and raised the frequency spectrum use factor. It may increase the system capacity, and it can satisfy the multimedia communication requisition. But the traditional OFDM technology sub-channel carrier frequency is invariable, cannot satisfy some special communications requisition. So this paper combines the frequency-hopping with the OFDM system, and constructs the FH-OFDM system.This paper mainly introduced the main principle of the frequency-hopping OFDM system. In this system each user in the cell is assigned a number of cellular by the base-station, which changes every OFDM symbol according to deterministic hopping patterns.Then, based on OFDM and FH-OFDM system models which are simulated with MATLAB, the simulation charts of the BER performances comparing between OFDM and FH-OFDM system from combating the White Gaussian Noise and Multi-path Interference are given. From analyses of the charts, FH-OFDM system is conclude to be superior to OFDM in the wireless data transmission.Last, this paper chiefly studies symbol timing synchronization. Based upon Maximum Likelihood (ML) estimation, it proposes an improved algorithm, iterative ML estimation. Iterative ML algorithm analyzes ML from the point of iteration. It simplifies implementary process of ML algorithm. Accordingly quicken the implementary speed of procedure.