4PAM在高斯信道与瑞利信道下的基带仿真系统实验

1、系统框图

2、代码

clear all
close all
clc
N = 10000;   %比特数
SNR=0:10;   %SNR的范围
EbN0 = 10.^(SNR/10);
err_num=zeros(1,length(SNR)); % 错误bit个数
simu_ber = zeros(1,length(SNR));     % 仿真误误码率
theory_berAWGN = zeros(1,length(SNR));   % 理论误码率
theroy_berRaliy = zeros(1,length(SNR));   % 理论误码率
R=raylrnd(0.5,1,N);      %产生瑞利信号
M = 4;%进制数
graycode = [0,1,2,3];%格雷映射
send_bit = randsrc(1,N,[0:3]);
send_bit2 = graycode(send_bit+1); %格雷编码
send_bit3 = pammod(send_bit2,M);%PAM调制

msg_tx = real(send_bit3);
hR = send_bit3.*R; %瑞利分布
pow_msg=norm(msg_tx)^2/length(msg_tx); %信号码元功率Es
for k=1:length(SNR)   
    sigma=sqrt(pow_msg/(2*10^(SNR(k)/10))); %噪声方差
    msg_rx_awgn=msg_tx+sigma*randn(1,N);%通过AWGN信道
    msg_rx_raily=awgn(hR,SNR(k),'measured');
    %4PAM 解调 
    dePAM_awgn = pamdemod(msg_rx_awgn,M);%PAM解调
    decPAM_awgn = graycode(dePAM_awgn+1);%解映射
    dePAM_Raily = pamdemod(msg_rx_raily,M);
    decPAM_Raily = graycode(dePAM_Raily+1);

 
    [~,BER(k)] = biterr(send_bit, decPAM_awgn, log2(M));   %计算AWGN信道BER
    [ ~,BER1(k)] =biterr(send_bit,decPAM_Raily,log2(M));   %计算瑞利衰落+AWGN信道BER
    [ ~,SER(k)] = symerr(send_bit, decPAM_awgn);            %计算AWGN信道SER
    [~,SER1(k)] = symerr(send_bit, decPAM_Raily);          %计算瑞利衰落+AWGN信道SER

    theory_ser(k) = 1.5*qfunc(sqrt(0.4*EbN0(k))); % 理论误符号特率
    theory_ber(k) = (2*(M-1)/M)*qfunc(sqrt(6*EbN0(k)/(M^2-1)));% 理论误比特率
    
end
figure
semilogy(SNR,BER,'-ro',SNR,SER,'-r*',SNR,BER1,'-b.',SNR,SER1,'-b^',SNR,theory_ser,'o-',SNR,theory_ber,'-sg')  ;     %画出BER和SER随SNR变化的曲线
legend('AWGN信道BER','AWGN信道SER','Rayleigh衰落+AWGN信道BER','Rayleigh衰落+AWGN信道SER','理论误符号率','理论误比特率');
title('4PAM在AWGN和Rayleigh衰落信道下的性能');
xlabel('信噪比（dB）');
ylabel('误符号率和误比特率');

%%画星座图
scatterplot(send_bit3);
title('调制信号星座图');
scatterplot(msg_rx_awgn);
title('AWGN接收信号星座图');
scatterplot(msg_rx_raily);
title('Raily接收信号星座图');

3、实验结果