On The Modulation & Demodulation Technology And Synchronization Algorithm In OFDM

Following OFDM principle and transceiver model, firstly, The influences on the performance of the OFDM system from the frame synchronization, symbol timing, carrier synchronization and sampling synchronization are deduced in theory separately. at the same time, representative OFDM synchronization methods are analyzed based on either cyclic prefixes or training symbols. Secondly, Focus is on the performance of several synchronization methods in burst packed transmission with reference to 802.11a frame structure and parameters. Thirdly, several classical channel estimation are discussed, our system have selected a proper algorithm from them thought the compromise between their performance and complexity. Finally, an improved channel estimation algorithm based on LS algorithm is presented. Considering the infection of the noise, the new algorithm has better performance under low SNR. Simulation results indicate the improved method has a good performance when the SNR is low.According to the improved method above, a real OFDM synchronization module and channel estimation module are designed and realized based on burst packed transmission on the platform of FPGA&DSP. This dissertation puts forward a general type of OFDM synchronization structure based on FPGA. Using pipeline and reverse-Cordic algorithm, Synchronization module achieve frame capture, symbol timing and frequency offset estimation. Channel estimation module realizes channel estimation and channel equalization. IF system for transmitting and receiving is accomplished after debug. Test results in AWGN channel are shown at the end of this dissertation. The result shows that the good synchronization, channel estimation and channel equalization performance contributes to the success of IF receiving system.