The Design And Implementation Of OFDM Modem Based On FPGA

Orthogonal Frequency Division Multiplexing (OFDM) is a kind of digital modulation technology of multi-carriers which has many characteristics such as higher spectrum efficiency, stronger ability of anti-multi-path interference and lower cost. It is suitable for the demand of the wireless communications in high speed, broad band and mobility, and will become the pivotal modulation and transmission technology of the next generation wireless communications (4G).This paper describes the OFDM fundamental principle firstly. For OFDM modulation, demodulation, characteristic and key technologies, it analyses them on theory and shows the more advantage than other modulating technology. Aim at channel estimation, deeply analyzes FFT-based cascade one-dimensional channel estimation algorithms and united iterative maximum likelihood semi-blind estimation algorithms, based on it, iterative maximum likelihood estimation algorithms is also described and compared by Matlab, both of them are validated.And then, OFDM system simulation platform is builded using Matlab and Simulink. On this platform, the data curve is gaven for OFDM system based on various module parameter, just like multi-path fade , Gauss white noise and so on. Through analyzing the simulation result, some system performances can be appraised exactly.After combining the front several chapters and illuminating the OFDM system configuration and simulation analysis aimed to system characteristics, emphasis is design and implementation of OFDM baseband processing based on FPGA. According to 802.16 protocol and OFDM characteristic, reasonable parameters are established. From modulator and demodulator to series-to-parallel conversion, QPSK mapping, over sampling, pilot insertion, guard interval addition, IFFT/FFT and frame synchronization detection, paper mskes design and implementation for every module of system, meanwhile present simulation waves and parameter explaination. Thereinto, due to limitation of fixed point, 24 float point format is design for system, and participated in IFFT/FFT with making full use of system resourse and improving operation efficiency in parameter allowed. And IFFT/FFT based on FPGA is emphasized, for the problem that Algorithm operation time is excessively long and occupied resource is excessively more, new Algorithm with pipelining and less resource occupied is brought out and carrid out. Put it into OFDM baseband processing system, parameter is satisfied well. Afterward, based on OFDM theory, the system debugging and performance analysis is necessary to do and the feasibility of this design is proved.All in all, the design, simulation and implementation of OFDM baseband processing based on FPGA is completed. This design provides many available data for farther improvement.