Research And Implementation Of Jamming Cancellation Technology In NC-OFDM System

NC-OFDM communication system has the advantages of anti-multipath and high spectrum utilization ratio of traditional OFDM system,and can also select different subcarriers to transmit data by sensing changes in the surrounding environment,which further improves the reliability of system transmission.Therefore,it has been widely used in cognitive radio.This dissertation focuses on the jamming cancellation technology of the NC-OFDM system,and implements the NC-OFDM communication transceiver transmission link and its jamming cancellation technology on the NI-USRP platform based on LabVIEW FPGA technology.The second chapter of this paper analyzes the characteristics of wireless fading channel model,as well as the characteristics of common jamming signals such as single tone jamming,multitone jamming,and chirp jamming;and gives the design of NCOFDM system transceiver link structure,frame format and system parameters.Finally,the simulation performance of the NC-OFDM system under the AWGN channel and fading channel in the jamming-free environment is given.The third chapter elaborates the process of jamming cancellation technology in detail,and analyzes the simulation performance of jamming cancellation algorithms based on different jamming signals.The single-tone jamming cancellation algorithm based on improved point-DFT interpolation can accurately estimate the amplitude,frequency and phase of single-tone jamming,so that the system performance in the jamming environment is close to the system performance without jamming.And because multitone jamming is the accumulation of multiple single-tone jamming,the cancellation of multi-tone jamming can be achieved by iterating the single-tone jamming cancellation algorithm based on N-DFT,which can eventually achieve a good anti-jamming effect.The chirp jamming cancellation algorithm based on multiple discrete phase transformations can estimate the parameters of chirp jamming more accurately,and there is no error leveling.The fourth chapter gives the concrete realization scheme of implementing NCOFDM communication system and jamming cancellation technology based on LabVIEW FPGA technology on USRP platform.First,the method of FPGA development based on the USRP platform is introduced;then,the implementation scheme of the NC-OFDM system transceiver link is designed,and the specific implementation scheme design of the key modules is given.Finally,the implementation schemes of single-tone jamming cancellation technology,multi-tone jamming cancellation technology,linear frequency modulation jamming cancellation are elaborated in detail.The configuration methods and timing diagrams of related modules are given.Problems and solutions encountered during implementation are summarized.Finally,based on the USRP platform,the bit error rate transmission performance test of the NC-OFDM system was carried out.The actual measurement results show that,whether it is an AWGN channel or a fading channel,the performance of NC-OFDM system with jamming cancellation technology has a strong anti-jamming ability,close to the performance without jamming...