ofdm1.m

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%%%%% 该仿真程序是QPSK在AWGN信道下的调制解调性能验证实例 %%%%%%%%%%%%
%%%%% 该BPSK调制解调是忽略了载波调制与发送、接收基带成形的 %%%%%%%%%
%%%%%% 根据程序框架补充完程序并仿真 %%%%%%%%%%%%%%%%%%%%%%%
clc
clear all;
EbN0dB=1:10;%设定信噪比
errLimit=50;%设定每个信噪比下循环终止统计错误数
N=256;      %每次循环仿真矢量长度
for ii=1:length(EbN0dB)
    errCount=0;
    totalN=0;
    sigma2(ii)=2/(2*2*(10^(EbN0dB(ii)/10)));%AWGN信道噪声方差与信噪比的关系
    while errCount<errLimit
        source=rand(1,N)>0.5;                        %产生比特信源
        %QPSK调制映射
        source=source';
        sourc = vec2mat(source,2);
        for k=1:N/2
            if [sourc(k,1),sourc(k,2)]==[0 0]
                trans(k) = -1-i;
            elseif [sourc(k,1),sourc(k,2)]==[0 1]
                trans(k) = -1+i;
            elseif [sourc(k,1),sourc(k,2)]==[1 0]
                trans(k) = 1-i;
            elseif [sourc(k,1),sourc(k,2)]==[1 1]
                trans(k) = 1+i;
            end
        end
        %为得到正交载波频率在QPSK后进行IFFT变换，在接受端再进行反变换FFT
        iffttans=sqrt(N/2)*ifft(trans,N/2);
        soutans=[zeros(1,32),iffttans];
        Xc=sqrt(0.5)*randn(1,(32+N/2));
        Xs=sqrt(0.5)*randn(1,(32+N/2));
        R=sqrt(Xc.^2+Xs.^2);
        receiver= R.*soutans+sqrt(sigma2(ii))*randn(1,(32+N/2))+i*sqrt(sigma2(ii))*randn(1,(32+N/2));           %加信道噪声,如果是衰落信道，信号模型为y=k*x+n
        receiver=receiver(33:(32+N/2));
        fftreceiver=fft(receiver,N/2);
        %QPSK解调，根据调制映射得到判决条件
        for k=1:N/2
            demod(k,1)=(real(fftreceiver(k))>0);
            demod(k,2)=(imag(fftreceiver(k))>0);
            
        end
        demodata=vec2mat(demod,1);
        temp=sum(abs(source-demodata));
        errCount=errCount+temp;
        totalN=totalN+N;
    end
    ber(ii)=errCount/totalN;
end

ber
%仿真性能曲线
semilogy(EbN0dB,ber,'-o');
hold on;
grid on;
%理论性能曲线
divorder=1;
berthe = berfading(EbN0dB,'psk',4,divorder);
semilogy(EbN0dB,berthe,'-*');