基于matlab的QPSK仿真(4)

if sum(qdata2((n-1)/delta_T+1:n/delta_T))>=0 qdata3(n)=1; else qdata3(n)=0; end end

% 为了显示星座图,将信号进行处理 idata4=zeros(1,nb/2); qdata4=zeros(1,nb/2); for n=1:nb/2

Awgn_ichsum(n)=sum(idata2((n-1)/delta_T+1:n/delta_T))*delta_T; if Awgn_ichsum(n)>=0 idata4(n)=1; else idata4(n)=0; end

Awgn_qchsum(n)=sum(qdata2((n-1)/delta_T+1:n/delta_T))*delta_T; if Awgn_qchsum(n)>=0 qdata4(n)=1; else qdata4(n)=0; end end

% 将判决之后的数据存放进数组 demodata=zeros(1,nb);

demodata(1:ml:(nb-1))=idata3; demodata(2:ml:nb)=qdata3;

%为了显示，将它变成波形信号（即传输一个1代表单位宽度的高电平） demodata1=zeros(1,nb/delta_T); for q=1:nb

demodata1((q-1)/delta_T+1:q/delta_T)=demodata(q); end

% 累计误码数

% abs(demodata-data)求接收端和发射端 % 数据差的绝对值，累计之后就是误码个数 Awgn_num_BER=sum(abs(demodata-data))

% 解调部分（瑞利+高斯）

Ray_idata2=Ray_s.*a; Ray_qdata2=Ray_s.*b;

% 为了显示星座图,将信号进行处理 Ray_idata4=zeros(1,nb/2); Ray_qdata4=zeros(1,nb/2); for n=1:nb/2

Ray_ichsum(n)=sum(idata2((n-1)/delta_T+1:n/delta_T))*delta_T;

16

if Ray_ichsum(n)>=0 Ray_idata4(n)=1; else Ray_idata4(n)=0; end

Ray_qchsum(n)=sum(qdata2((n-1)/delta_T+1:n/delta_T))*delta_T; if Ray_qchsum(n)>=0 Ray_qdata4(n)=1; else Ray_qdata4(n)=0; end end

% 将判决之后的数据存放进数组 Ray_demodata=zeros(1,nb);

Ray_demodata(1:ml:(nb-1))=Ray_idata4; Ray_demodata(2:ml:nb)=Ray_qdata4;

%为了显示，将它变成波形信号（即传输一个1代表单位宽度的高电平） Ray_demodata1=zeros(1,nb/delta_T); for q=1:nb

Ray_demodata1((q-1)/delta_T+1:q/delta_T)=Ray_demodata(q); end

% 累计误码数

% abs(demodata-data)求接收端和发射端 % 数据差的绝对值，累计之后就是误码个数 Ray_num_BER=sum(abs(Ray_demodata-data))

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% 误码率计算

%% 调用了cm_sm32();和cm_sm33(）函数 %%声明： 函数声明在另外俩个M文件中

%%作用： cm_sm32()用于瑞利信道误码率的计算 %% cm_sm33()用于高斯信道误码率的计算 %% ecoh on/off 作用在于决定是否显示指令内容

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% SNRindB1=0:1:6; SNRindB2=0:0.1:6; % 瑞利衰落信道

for i=1:length(SNRindB1),

[pb,ps]=cm_sm32(SNRindB1(i)); % 比特误码率 smld_bit_ray_err_prb(i)=pb; smld_symbol_ray_err_prb(i)=ps; disp([ps,pb]); echo off; end;

% 高斯信道 echo on;

for i=1:length(SNRindB1),

17

[pb1,ps1]=cm_sm33(SNRindB1(i)); smld_bit_awgn_err_prb(i)=pb1; smld_symbol_awgn_err_prb(i)=ps1; disp([ps1,pb1]); echo off; end;

% 理论曲线 echo on;

for i=1:length(SNRindB2),

SNR=exp(SNRindB2(i)*log(10)/10); theo_err_awgn_prb(i)=0.5*erfc(sqrt(SNR)); theo_err_ray_prb(i)=0.5*(1-1/sqrt(1+1/SNR)); echo off; end;

h = spectrum.welch;

%---------------------------- 输出显示部分

% 第一部分（理想） figure(1)

subplot(3,2,1);

plot(data0),title('基带信号'); axis([0 20000 -2 2]); subplot(3,2,2);

psd(h,data1,'fs',fs),title('基带信号功率谱密度'); subplot(3,2,3);

plot(s),title('调制信号'); axis([0 500 -3 3]); subplot(3,2,4);

psd(h,s,'fs',fs),title('调制信号功率谱密度'); subplot(3,2,5);

plot(demodata1),title('解调输出'); axis([0 20000 -2 2]); subplot(3,2,6);

psd(h,demodata1,'fs',fs),title('解调输出功率谱密度');

% 通过高斯信道 figure(2)

subplot(2,2,1);

plot(s1),title('调制信号(Awgn)'); axis([0 500 -5 5]); subplot(2,2,2);

psd(h,s1,'fs',fs),title('调制信号功率谱密度(Awgn)'); subplot(2,2,3);

plot(s111),title('高斯噪声曲线');

18

axis([0 2000 -5 5]); figure(3) for i=1:nb/2

plot(idata(i),qdata(i),'r+'),title('QPSK信号星座图（Awgn）');hold on; axis([-2 2 -2 2]);

plot(Awgn_ichsum(i),Awgn_qchsum(i),'*');hold on; legend('理论值（发射端）','实际值（接收端）'); end

%通过高斯信道再通过瑞利衰落信道 figure(4) subplot(2,2,1)

plot(Ray_s),title('调制信号(Ray+Awgn)'); axis([0 500 -5 5]); subplot(2,2,2);

psd(h,Ray_s,'fs',fs),title('调制信号功率谱密度(Ray)'); figure(5) for i=1:nb/2

plot(idata(i),qdata(i),'r+'),title('QPSK信号星座图（Awgn+Ray）');hold on; axis([-2 2 -2 2]);

plot(Ray_ichsum(i),Ray_qchsum(i),'*');hold on; legend('理论值（发射端）','实际值（接收端）'); end

figure(6)

semilogy(SNRindB2,theo_err_awgn_prb,'r'),title('误码率曲线');hold on; semilogy(SNRindB1,smld_bit_awgn_err_prb,'r*');hold on; semilogy(SNRindB2,theo_err_ray_prb);hold on; semilogy(SNRindB1,smld_bit_ray_err_prb,'+'); xlabel('Eb/No');ylabel('BER');

legend('理论AWGN','仿真AWGN','理论Rayleigh','仿真Rayleigh');

cm_sm32()用于瑞利信道误码率的计算： function [pb,ps]=cm_sm32(snr_in_dB) % [pb,ps]=cm_sm32(snr_in_dB)

% CM_SM3 finds the probability of bit error and symbol error for % the given value of snr_in_dB, signal to noise ratio in dB.

N=100;

E=1; % energy per symbol numofsymbolerror=0; numofbiterror=0; counter=0;

snr=10^(snr_in_dB/10); % signal to noise ratio sgma=sqrt(E/snr)/2; % noise variance

19

s00=[1 0]; s01=[0 1]; s11=[-1 0]; s10=[0 -1]; % signal mapping % generation of the data source while(numofbiterror<100) for i=1:N,

temp=rand; % a uniform random variable between 0 and 1

if (temp<0.25), % with probability 1/4, source output is \ dsource1(i)=0; dsource2(i)=0;

elseif (temp<0.5), % with probability 1/4, source output is \ dsource1(i)=0; dsource2(i)=1;

elseif (temp<0.75), % with probability 1/4, source output is \ dsource1(i)=1; dsource2(i)=0;

else % with probability 1/4, source output is \

dsource1(i)=1; dsource2(i)=1; end; end;

% detection and the probability of error calculation

for i=1:N,

ray=raylrnd(0.8);

n=sgma*randn(1,2); % 2 normal distributed r.v with 0, variance sgma

if ((dsource1(i)==0) & (dsource2(i)==0)), r=ray*s00+n;

elseif ((dsource1(i)==0) & (dsource2(i)==1)), r=ray*s01+n;

elseif ((dsource1(i)==1) & (dsource2(i)==0)), r=s10*ray+n; else

r=s11*ray+n; end;

% The correlation metrics are computed below

c00=dot(r,s00); c01=dot(r,s01); c10=dot(r,s10); c11=dot(r,s11); % The decision on the ith symbol is made next c_max=max([c00,c01,c10,c11]);

if (c00==c_max), decis1=0; decis2=0; elseif (c01==c_max), decis1=0; decis2=1; elseif (c10==c_max), decis1=1; decis2=0; else decis1=1; decis2=1; end;

% Increment the error counter, if the decision is not correct symbolerror=0;

if (decis1~=dsource1(i)), numofbiterror=numofbiterror+1; symbolerror=1; end;

if (decis2~=dsource2(i)), numofbiterror=numofbiterror+1; symbolerror=1;

20

百度搜索“77cn”或“免费范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，免费范文网，提供经典小说综合文库基于matlab的QPSK仿真(4)在线全文阅读。