FPGA Design And Implementation Of 64QAM Modem Based On SDR

With the coming of the 4G era, the contradiction between exiguity of spectrum resources available for mobile communication and rapidly growing volume demand of communication multimedia business becomes deepening day after day. It is urgent to seek the breakthrough point by tightly connecting the mature theories with key technologies, so that with the guarantee of communication quality to be the premise, spectrum utilization rate of wireless communication system and mobile user capacity can get significantly improved. Based on this, with the combination of efficient digital modulation mode QAM with software radio technology, the design and implementation of the 64QAM modem on the large-scale field programmable logic device FPGA are fulfilled.This paper is based on foundational theories in software radio,such as bandpass sampling theory, multi rate digital signal processing theory etc,and the deductive analysis of corresponding theory is made. It also studies software radio's core technology----the digital down converter's principle as well as its FPGA implementing structure, and launches the derivation and specification of the principle and process of Reed-solomon coding and decoding. Besides,the methods of efficient digital filter's FPGA implementation are explained. Furthermore, the principle and FPGA implementation of the carrier synchronization technology based on phase-locked loop structure are discussed. During the design of 64QAM modem system, the top-down design idea is used and the hardware description language Verilog is utilized under the environment of the EDA tools ISE 14.3 and Modelsim 10.1 as programming means for the system's implementation. The method of cooperating software with hardware and combining algorithm simulation and system test debugging is used for system's debugging and verification.In this paper,the explanations of the theory of 64QAM modulation and demodulation algorithms are firstly made, and the feasibility of the design scheme is verified through the simulation of 64QAM communication system's transceiver modules. On this basis, simulink and ISE are used to design and implement the modules of transmitting end to realize the following functions, such as m sequence scrambling, RS encoding,serial to parallel converting, Gray differential encoding, 64QAM constellation mapping, pulse shaping interpolation filtering, quadrature up converting and simulating of Gauss white noise channel;the receiving end has respectively completed the design of corresponding modules to realize functions like bandpass sampling, quadrature digital down converting, coherent demodulating,matched filtering and 64QAM decoding. Finally, waveforms and spectra belonging to communication system's significant modules, as well as some simulation results characterizing system's reliability performance,are obtained from simulink and modelsim software. Analysis shows that the simulation results accord with design expectations,therefore, the realization of 64QAM modem based on SDR in the FPGA universal hardware platform has been fulfilled.