The Research And FPGA Implementation Of OFDM Receiver Synchronization

Orthogonal freqency division multiplexing with high spectrum efficiency, resistance to multipath interference ability, has been widely used in the field of wireless broadband access and next-generation (B3G or4G) mobile communication system.The OFDM system is sensitive to symbol timing error and carrier frequency deviation because of the orthogonal properties among its sub carriers. Therefore, it is important for OFDM system to obtain accurate symbol timing and carrier frequency synchronization.This paper mainly researchs synchronization in OFDM system based on IEEE802.11a system and FPGA realizing.The OFDM principle and its key technologies are analysised firstly in brief, then analysis the effects of symbol timing offset, carrier frequency offset, sampling frequency offset in OFDM system.The typical symbol timing and carrier frequency synchronization algorithm based on training sequence and sampling frequency synchronization algorithm based on pilot are detailed and compared, some improved algorithms are also presented. The system simulations and FPGA implement analyses are made to each algorithm.There are three synchronization module,including timing synchronization, carrier frequency synchronization, the sampling frequency synchronization. Timing synchronization module is divided into the frame synchronization and symbol timing synchronization, and improved algorithm have a better performance than the original algorithm. For carrier synchronization algorithm, using averaging method to obtain more precise carrier frequency offset and compensate. The sampling frequency synchronization algorithm, to take more easily implemented in hardware. The whole synchronization system is based on FPGA and the synthesis and simulation results in ISE and Modelsim have proved the correction of the system design.