Research And Design Of FFT Algorithm In OFDM System

With people's ever-increasing demand of the datamation, broadband, personalization and mobilization in communication, as well as the defects of communication technology, the future communication skills will be mainly dominanted by orthogonal frequency division multiplexing (OFDM) technology. This technique has its own advantages like high efficiency, low cost etc.OFDM is a kind of high-speed transmission technology under wireless environment. It is suitable for the transmission of high-speed data in the wireless mobile channel of multipath dissemination and the Doppler frequency. High-speed data is firstly treated by serial-to-parallel convert, and then assigned to some by-pass channels for transmission via this technology. In doing so, it reduces the effect to the system produced by the time dispersion along with the multipath delay spread of wireless channel. It also can oppose against the influence of dispersion effective, eliminate the intersymbol interference (ISI), and cope with the selective decline of frequency. Meanwhile, the utilization ratio of the channel is relatively high. Digital signal processing technology is widely used in areas like speech sounds, multimedia and communication. Fast Fourier transform (FFT) is one important theory of modern signal processing which serves as the core of digital signal processing technology.In view of the multipath effect in high speed data transmission technology and defects of interference between the symbols, this dissertation puts forwad the OFDM systems design scheme. The scheme adopts the IFFT/FFT to achieve modulation and demodulation. Based on the platform of Quartus II 7.2, this dissertation designs the FFT processor to realize each module with VHDL language programming and checks its feasibility through the Comprehensi-ve simulation, time-series analysis and MATLAB simulation results. This system can solve the transmission problem of high-speed information flaw in the channel, oppose against the influence of dispersion effective, and eliminate the intersymbol interference (ISI), achieving the data transmission with high speed. Adopting field programmable gates array (FPGA) device to build the hardware system, the complexity of OFDM systems will be reduced.