BPSK相干解调和DBPSK非相干解调误码率仿真

BPSK相干解调和DBPSK非相干解调误码率仿真

本脚本完成了BPSK和DBPSK两种不同调制方式下的误码率（DBPSK差分相干）仿真， 并和理论曲线进行了对比。

  撰写人：***
  最后修改日期：2015-03-18
  软件版本：MATLAB(R) 2014a

程序添加和修改包括

1. BPSK未作修改
2. DPSK添加了成型部分，同时从《高等数字通信》中看到了DPSK最佳接收机的结构

待改进

1. 怎样选择仿真点数才能保证结果可信，可信程度是多少？如何衡量？

Contents

• 初始设置
• 误码率仿真
• 绘图和数据输出

初始设置

清空工作区，数据，关闭所有窗口

clc;clear all;close all;

仿真参数设置

EbN0_dB = 1:8;                            % EbN0_dB 误码率范围，向量;
FRAMES_NUM = 100;                         % FRAMES_NUM 最大仿真帧数目;
FRAMES_LENGTH = 1000;                     % FRAMES_LENGTH 每帧长度;
UPSAMPLE_RATE = 8;                        % UPSAMPLE_RATE 过采样率；
berBpsk = zeros(1,length(EbN0_dB));       % berBpsk BPSK误码率统计，向量;
berDbpsk = zeros(1,length(EbN0_dB));      % berDbpsk DBPSK误码率统计，向量;
sqrtRaisedfilter = rcosfir(0.3,[-3,3],UPSAMPLE_RATE,1,'sqrt');

误码率仿真

针对不同EbN0先仿真BPSK和DBPSK误码率曲线

在不同EbN0下，对误码率进行仿真

for nEbN0 = 1:length(EbN0_dB);

多帧取统计平均

    bpskErrorNum = 0;
    dbpskErrorNum = 0;
    for nFrame = 1:FRAMES_NUM

数据生成和基带映射

        data = randi([0 1],1,FRAMES_LENGTH);
        bpskBaseband = 1 - 2*data;          % 映射 0—+1;1—-1,已归一化
        data_extend = [1 data];             % 差分编码，假设第一个数据为1
        for num = 2:FRAMES_LENGTH+1
            data_extend(num) = xor(data_extend(num),data_extend(num-1));
        end
        % 注意此时DBPSK多传了一个1
        dbpskBaseband = 1 - 2*data_extend;  % 映射 0—+1;1—-1,已归一化
        % 方波成型
        %dbpskBaseband = reshape(repmat(dbpskBaseband,UPSAMPLE_RATE,1),1,[]);
        % 匹配滤波
        dbpskBaseband = upsample(dbpskBaseband,UPSAMPLE_RATE);
        dbpskBaseband = conv(dbpskBaseband,sqrtRaisedfilter,'same');
        bpskTransmitSignal = bpskBaseband;  % 不加载波
        dbpskTransmitSignal = dbpskBaseband/sqrt(var(dbpskBaseband));

AWGN 信道，SNR和EbN0换算关系

        SNR_dB = EbN0_dB(nEbN0) + 10*log10(2) - 10*log10(1);
        SNR = 10^(SNR_dB/10);

接收信号的矢量等效

        bpsknoise = 1/sqrt(SNR)*randn(1,length(bpskTransmitSignal));
        bpskReceiveSignal = bpskTransmitSignal + bpsknoise;
        SNR_dB = EbN0_dB(nEbN0) + 10*log10(2) - 10*log10(UPSAMPLE_RATE);
        SNR = 10^(SNR_dB/10);
        dbpsknoise =  1/sqrt(SNR)*randn(1,length(dbpskTransmitSignal)) + ...
            1i*1/sqrt(SNR)*randn(1,length(dbpskTransmitSignal));
        dbpskReceiveSignal = dbpskTransmitSignal + dbpsknoise;

BPSK误比特数统计

        bpskErrorNum = bpskErrorNum + sum(bpskBaseband.*bpskReceiveSignal<0);

DBPSK解调（通信原理P209） 误比特数统计，不是最佳接收 方波成型解调如果UPSAMPLE_RATE为1，此时能使用sum函数

        %dbpskReceiveSignal = sum(reshape(dbpskReceiveSignal,UPSAMPLE_RATE,[]));
        % 匹配滤波解调
        dbpskReceiveSignal = conv(dbpskReceiveSignal,sqrtRaisedfilter,'same');
        dbpskReceiveSignal = downsample(dbpskReceiveSignal,UPSAMPLE_RATE);
        dbpskDelay = dbpskReceiveSignal(2:end);
        dbpskJudgment = dbpskReceiveSignal(1:end-1).*dbpskDelay;
        dbpskDecodeData = zeros(1,length(data));
        dbpskDecodeData(dbpskJudgment<0) = 1;   %gt compares only the real part
        dbpskErrorNum = dbpskErrorNum + sum(abs(dbpskDecodeData-data));

    end

误码率统计

    berBpsk(nEbN0) = bpskErrorNum/FRAMES_NUM/FRAMES_LENGTH;
    berDbpsk(nEbN0) = dbpskErrorNum/FRAMES_NUM/FRAMES_LENGTH;

end

绘图和数据输出

绘制BPSK和DBPSK的仿真和理论误码率曲线

berBpskTheory = berawgn(EbN0_dB,'psk',2,'nondiff');
berDbpskTheory = berawgn(EbN0_dB,'dpsk',2,'nondiff');
fprintf('总帧数 = %d,帧长 = %d
',FRAMES_NUM,FRAMES_LENGTH);
table(EbN0_dB',berBpskTheory',berBpsk',berDbpskTheory',berDbpsk',...
    'VariableNames', {'EbN0_dB','BpskTheory','BpskSim','DbpskTheory','DbpskSim'})

figure;
semilogy(EbN0_dB,berDbpsk,'bd');hold on;
semilogy(EbN0_dB,berDbpskTheory,'b-');
semilogy(EbN0_dB,berBpsk,'rs');
semilogy(EbN0_dB,berBpskTheory,'r-');hold off;
legend('差分DPSK仿真','DPSK理论','相干BPSK仿真','相干BPSK理论');
xlabel('EbN0');
ylabel('BER');
grid on;

总帧数 = 100,帧长 = 1000

ans = 

    EbN0_dB    BpskTheory    BpskSim    DbpskTheory    DbpskSim
    _______    __________    _______    ___________    ________

    1            0.056282    0.05494      0.14198      0.14132 
    2            0.037506    0.03737      0.10248      0.10291 
    3            0.022878    0.02259     0.067989      0.06888 
    4            0.012501    0.01247     0.040558      0.03912 
    5           0.0059539     0.0061     0.021165      0.02151 
    6           0.0023883     0.0024    0.0093328      0.00937 
    7          0.00077267    0.00079    0.0033292      0.00334 
    8          0.00019091    0.00022    0.0009094      0.00076 

Published with MATLAB® R2014a