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
- BPSK未作修改
- 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
- 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
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\n',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
