16QAM-星形和矩形星座图调制解调MATLAB代码

16QAM-星形和矩形星座图调制解调MATLAB代码

%%

------------------------------------------------------------ % 软件无线电课程设计

%

% 方形、星形16QAM调制解调仿真%

%%------------------------------------------------------------

%%主程序

clc

clear

%% 定义参数

fd=250*10^6; %码元速率250M

fs=2500*10^6; %滤波器采样率

fc=2500*10^6; %载波频率2.5G

f=10000*10^6; %对载波采样

data_len=200000; %数据长度

sym_len=data_len/4; %码元序列长度

M_QAM=16;%QAM数

k=log2(M_QAM);

SNR=1:12;%白噪声信噪比,

%%

------------------------------------------------------------ bit_tx=randint(1,data_len);%产生随机序列echo off;

rec_qam16=QamMod(bit_tx,16);

%方形16QAM调制

star_qam16=SrarQamMod(bit_tx);

%星形16QAM调制

base_rec=base_shape(fd,fs,f,rec_qam16);

%基带成型滤波

base_star=base_shape(fd,fs,f,star_qam16); %基带成型滤波

for

i=1:length(SNR) %信噪比从1dB到12dB计算误码率

SNR_=i

%方形映射16QAM

rf_rec_qam16=CarrierMod(fc,f,base_rec);

%载波调制

rf_rec_qam16_n=awgn(rf_rec_qam16,SNR(i),'m easured'); %加噪声

[rec_qam16_rx

base_rec_rx]=CarrierDemod(fd,fs,fc,f,rf_rec_qa m16_n); %载波解调

bit_rec_rx=QamDemod(rec_qam16_rx,16);

%MQAM解调

[num_qam16,perr_qam16_rec(i)]=biterr(bit_tx, bit_rec_rx);%误码率

qam16_data_rec(i,:)=rec_qam16_rx;

%scatterplot(rec_qam16_rx);

%星形映射16QAM

rf_star_qam16=CarrierMod(fc,f,base_star);

%载波调制

rf_star_qam16_n=awgn(rf_star_qam16,SNR(i),' measured'); %加噪声

[star_qam16_rx

base_star_rx]=CarrierDemod(fd,fs,fc,f,rf_star_ qam16_n); %载波解调

bit_star_rx=StarQamDemod(star_qam16_rx);

%MQAM解调

[num_qam16,perr_qam16_star(i)]=biterr(bit_tx ,bit_star_rx);%误码率

qam16_data_star(i,:)=star_qam16_rx;

%scatterplot(star_qam16_rx);

end

%% 理论误码率计算

SNRtheo=0:0.1:length(SNR);

for i=1:length(SNRtheo)

SNRdec=10.^(SNRtheo(i)/10);

theo_perr_qam16(i)=(3/8)*erfc(sqrt(SNRdec*2/ 5));

end

%% 基带波形

N=200;

n=1:N;

t=1:N*10;

%发送端波形

figure;

stem(n,bit_tx(n)); title('发送序列'); %发送序列

figure('Name','发送端基带信号');

subplot(411);

plot(t,real(base_rec(t))); title('方形映射-Q路');

subplot(412);

plot(t,imag(base_rec(t))); title('方形映射-I路');

subplot(413);

plot(t,real(base_star(t))); title('星形映射-Q路

subplot(414);

plot(t,imag(base_star(t))); title('星形映射-I路');

%接收端波形

figure;

subplot(211);

stem(n,bit_rec_rx(n)); title('方形接收序列');

subplot(212);

stem(n,bit_star_rx(n)); title('星形接收序列');

figure('Name','接收端基带信号');

subplot(411);

plot(t,real(base_rec_rx(t))); title('方形映射-Q 路');

subplot(412);

plot(t,imag(base_rec_rx(t))); title('方形映射-I 路');

subplot(413);

plot(t,real(base_star_rx(t))); title('星形映射-Q路');

subplot(414);

plot(t,imag(base_star_rx(t))); title('星形映射-I路');

%基带眼图

N1=20000;

Tn=f/fd;

eye_rex=base_rec(1:N1);

eyediagram(eye_rex,Tn*4,Tn); title('方形基带眼图');

eye_star=base_star(1:N1);

eyediagram(eye_star,Tn*4,Tn); title('星形基带眼图');

%% 接收端星座图

%scatterplot(qam16_data_rec(12,:));

figure('Name','方形16QAM接收端星座图'); for i=3:3:12

subplot(2,2,i/3);

plot(real(qam16_data_rec(i,:)),imag(qam16_dat

a_rec(i,:)),'.');

xmax=5;axis([-xmax xmax -xmax xmax])

title(['Snr=',num2str(SNR(i)),' dB']);

end

figure('Name','星形16QAM接收端星座图'); for i=3:3:12

subplot(2,2,i/3);

plot(real(qam16_data_star(i,:)),imag(qam16_dat a_star(i,:)),'.');

xmax=3;axis([-xmax xmax -xmax xmax])

grid on; title(['Snr=',num2str(SNR(i)),' dB']);

end

%% 功率谱密度

f_plot;

%% 误码率分析

%16QAM误码率曲线

figure('Name','16QAM误码性能对比');

% semilogy(SNRtheo,theo_perr_qam16);

% hold on;

semilogy(SNR,perr_qam16_rec,'*');

hold on;

semilogy(SNR,perr_qam16_star,'o');

xlabel('SNR in dB');

ylabel('Prb of Err');

legend('方形16QAM','星形16QAM');

title('16QAM误码性能对比');

%-------------------------------------------------------------------------------

%% 基带成型

function

base_info=base_shape(fd,fs,f,seq_16QAM)

%平方根升余弦滤波器,滚降系数0.5，延迟3个采样点

flt=rcosine(fd,fs,'sqrt',0.5);

%I路和Q路

seq_Q=real(seq_16QAM);

seq_I=imag(seq_16QAM);

%增采样

R=fs/fd;

up_seq_Q=upsample(seq_Q,R);

up_seq_I=upsample(seq_I,R);

%升余弦调制

rcos_Q=conv(up_seq_Q,flt);

rcos_I=conv(up_seq_I,flt);

%提升

rcos_Q_up=interp(rcos_Q,f/fs);

rcos_I_up=interp(rcos_I,f/fs);

base_info=rcos_Q_up+j*rcos_I_up;

%--------------------------------------------------------------------

%% 载波解调

function [data_rx

base_rx]=CarrierDemod(fd,fs,fc,f,receive)

%% 分两路乘正交高频载波

rc_length=length(receive);

flt=rcosine(fd,fs,'sqrt',0.5);

t=0:rc_length-1;

rc_Q=receive .* sin(2*pi*fc*t/f);

rc_I=receive .* cos(2*pi*fc*t/f);

%减采样后根升余弦匹配滤波，注意对齐采样点down_Q=downsample([0 rc_Q],f/fs);

down_I=downsample(rc_I,f/fs);

low_Q_rcos=conv(down_Q,flt);

low_I_rcos=conv(down_I,flt);

base_rx=low_Q_rcos(1:length(low_I_rcos))+j*lo w_I_rcos;

%两次根升余弦滤波延迟，定位初始信号位置%delay+1:end-delay-1

R=fs/fd;

delay=3*R*2;

rc_Q_seq=(downsample(low_Q_rcos(delay+1:en d-delay-1),R));

rc_I_seq=(downsample(low_I_rcos(delay+1:end -delay-1),R)); %类型转换

data_rx=rc_Q_seq+j*rc_I_seq;

%--------------------------------------------------------------------------

%% 载波调制

function transmit=CarrierMod(fc,f,base)

%载波调制

t=0:length(base)-1;

high_freq_Q=real(base) .* sin(2*pi*fc*t/f); high_freq_I=imag(base) .* cos(2*pi*fc*t/f);

transmit=high_freq_Q+high_freq_I;

%------------------------------------------------------------------------------

%

% QAM解调程序，将MQAM码元还原为二进制数据

% 入口参数：data_QAM：QAM码元数据

% M_QAM:MQAM中M的大小

% 出口参数：二进制数据比特流%------------------------------------------------------------------------

function

data_out=QamDemod(data_QAM,M_QAM)

k=log2(M_QAM);%每个M进制码元的bit数data_len=length(data_QAM);%码元长度

%-------------------------------------------------------------------

%QAM信号放缩至与发送端相同比例

data_temp=data_QAM(find(real(data_QAM>0) ));

aver=mean(real(data_temp));

data_Qam_temp=data_QAM/aver*(2^(k/2-1));

%------------------------------------------------------------------------

%平移到第一象限

data_Qam_temp2=(data_Qam_temp+(2^(k/2)-1 )*(1+j))/2;

%----------------------------------------------------------------------

%将实部虚部分别映射为二进制数据

%实部

data_real=round(real(data_Qam_temp2));%实部判决

data_real(find(data_real>(2^(k/2)-1)))=2^(k/2)-1 ;%大于2^(k/2)-1的数据判定为2^(k/2)-1

data_real(find(data_real<0))=0;%小于0的数据判为0

bit_real=abs(dec2bin(data_real))-'0';

%虚部

data_imag=round(imag(data_Qam_temp2));%虚部判决

data_imag(find(data_imag>(2^(k/2)-1)))=2^(k/2 )-1;%大于2^(k/2)-1的数据判定为2^(k/2)-1 data_imag(find(data_imag<0))=0;%小于0的数

据判为0

bit_imag=abs(dec2bin(data_imag))-'0';

%------------------------------------------------------------------------

%还原为二进制比特流

bit_rec=[bit_real,bit_imag]';

data_out=reshape(bit_rec,1,data_len*k);

%-------------------------------------------------------------------------------------------------------------

%

% QAM调制程序，实现二进制到MQam调制

% 入口参数：binary：二进制数据% M_QAM:MQAM中M的大小

% 返回参数：MQAM码元

%------------------------------------------------------------------------

function data_M = QamMod(binary,M_QAM)

k=log2(M_QAM);%每个M进制码元的bit数

data_len=length(binary);%比特长度

binary_rec=reshape(binary,k,data_len/k)';%转化为data_len/k行，k列，的矩阵，以便转化为16进制M进制

%计算实部

data_str1=num2str(binary_rec(:,1:k/2));

data_m_real=bin2dec(data_str1);

%计算虚部

data_str2=num2str(binary_rec(:,k/2+1:k)); data_m_imag=bin2dec(data_str2);

%实部虚部映射到MQam

data_M=((data_m_real*2-2^(k/2)+1)+j*(data_m _imag*2-2^(k/2)+1)).';

%---------------------------------------------------------------------------------

%% 星形16QAM映射

function data_m16 = SrarQamMod(binary)

%binary=randint(1,100);%产生随机序列

data_len=length(binary);%比特长度

binary_rec=reshape(binary,4,data_len/4)';%转化为data_len/4行，4列，的矩阵，以便转化为16进制

data_str=num2str(binary_rec);

data_dec=bin2dec(data_str);

data_mm16=(floor(data_dec/8)+1).*exp(j*45/18 0*pi*mod(data_dec,8));

data_m16=reshape(data_mm16,1,data_len/4);

%------------------------------------------------------------------------------

%% 星形16QAM解调

function data_bit = StarQamDemod(qam_rev) %qam_rev=xing_qam16_noise(1:10);

am=abs(qam_rev);%幅度判定

am(find(am>2))=2;%幅度大于2的判定为2 am(find(am<1.5))=1;%幅度大于2的判定为2

%相位判定

ang=angle(qam_rev)/pi*180;%将-180度到0度变为180度到360度

ang(find(ang<0))=ang(find(ang<0))+360;

ang_n=round(ang/45);

ang_n(find(ang_n>7))=0;

data_dec=8*(round(am)-1)+ang_n;

%data_dec(find(data_dec>15))=15;%大于15的判定为15

%data_dec(find(data_dec<0))=0;%小于0的判定为0

data_bit_rec=dec2bin(data_dec);

data_bit=reshape(data_bit_rec',1,length(qam_re v)*4)-'0';