MATLAB_OFDM_正交频分复用_技术仿真_信道衰落_干扰因素

close all; clear all; clc; %------------------变量设置------------------------------------------ FS=2048; % ifft/fft点数 para=800; % 并行子载波800 Tu=200e-3; % OFDM符号周期 Gtime=50e-3; % 1/4的OFDM符号周期为保护间隔持续时间Gtime=50e-3（单位s） bits_per_symbol=2; % 每符号含比特数 Ns=4; % 每子载波含符号数128 （为方便测试，改为4） ProtectionRatio=1/4; % 保护间隔与OFDM数据的比例1/4 LI=7 ; % 导频之间的间隔 Np=ceil(para/LI)+1; % 导频数 %加1的原因：使最后一列也是导频 N_number=para*Ns*bits_per_symbol; % 所输入的比特数目 carriers=1:para+Np; % 加入导频的载波序列 G=ProtectionRatio*FS; % 1/4的抽样频率为保护间隔长度G=512 N_snr=40; % 每比特信噪比 snr=8; % 信噪比间隔 show_flag=0; % 为通过星座图表现信号的发送与接收，设定标志，画出SNR=8时的信号星座图 %---------------初始化--------------------------------------------- X=zeros(1,N_number); X1=[]; X2=[]; X3=[]; X4=[]; X5=[]; X6=[]; X7=[]; Y1=[]; Y2=[]; Y3=[]; Y4=[]; Y5=[]; Y6=[]; Y7=[]; XX=zeros(1,N_number); diff_bits=zeros(1,N_number); X=randint(1,N_number); %产生二进制随即序列（非0即1） %------QPSK调制：(1 1)->pi/4;(0 1)->3*pi/4;(0,0)->-3*pi/4;(1,0)->-pi/4------------------------------- s=(X.*2-1)/sqrt(2); sreal=s(1:2:N_number); simage=s(2:2:N_number); X1=sreal+j.*simage; figure(1); plot(X1,'r*'); % QPSK调制后星座图 axis([-4, 4, -4, 4]); grid on title('QPSK调制后星座图'); %-------产生随机导频信号-------------------------------------------------- train_sym=randint(1,2*Ns); t=(train_sym.*2-1)/sqrt(2); treal=t(1:2:2*Ns); timage=t(2:2:2*Ns); training_symbols1=treal+j.*timage; training_symbols2=training_symbols1.'; training_symbols=repmat(training_symbols2,1,Np); pilot=1:LI+1:para+Np; if length(pilot)~=Np pilot=[pilot,para+Np]; end %------------------串并转换----------------------------------------------- X2=reshape(X1,para,Ns).'; %-------------插入导频-------------------------------------------- signal=1:para+Np; signal(pilot)=[]; X3(:,pilot)=training_symbols; X3(:,signal)=X2; IFFT_modulation=zeros(Ns,FS); IFFT_modulation(:,carriers)=X3; X4=ifft(IFFT_modulation,FS,2); % IFFT变换，得到OFDM信号 %------------加保护间隔（循环前缀）---------------------------------- for k=1:Ns; for i=1:FS; X6(k,i+G)=X4(k,i); end for i=1:G; X6(k,i)=X4(k,i+FS-G); end end %------------并串转换----------------------------------------------- X7=reshape(X6.',1,Ns*(FS+G)); %-----------信道模型:带多普勒频移的瑞利衰落信道--------------------------------- fd=100; %多普勒频移 r=6; %多径数 a=[0.123 0.3 0.4 0.5 0.7 0.8]; %多径的幅度 d=[2 3 4 5 9 13]; %各径的延迟 T=1; %系统采样周期 th=[90 0 72 144 216 288]*pi./180; %相移 h=zeros(1,para); hh=[]; for k=1:r h1=a(k)*exp(j*((2*pi*T*fd*d(k)/para))); hh=[hh,h1]; end h(d+1)=hh; channel1=zeros(size(X7)); channel1(1+d(1):length(X7))=hh(1)*X7(1:length(X7)-d(1)); channel2=zeros(size(X7)); channel2(1+d(2):length(X7))=hh(2)*X7(1:length(X7)-d(2)); channel3=zeros(size(X7)); channel3(1+d(3):length(X7))=hh(3)*X7(1:length(X7)-d(3)); channel4=zeros(size(X7)); channel4(1+d(4):length(X7))=hh(4)*X7(1:length(X7)-d(4)); channel5=zeros(size(X7)); channel5(1+d(5):length(X7))=hh(5)*X7(1:length(X7)-d(5)); channel6=zeros(size(X7)); channel6(1+d(6):length(X7))=hh(6)*X7(1:length(X7)-d(6)); %------------------OFDM信号发送--------------------------------------------- Tx_data=X7+channel1+channel2+channel3+channel4; %----------不同SNR条件下，加高斯白噪声后的OFDM接收---------------------------------------------- Error_ber=[]; %误比特数 for snr_db=0:snr:N_snr if snr_db==8 show_flag=1; end code_power=0; code_power=[norm(Tx_data)]^2/(length(Tx_data)); %信号的符号功率 bit_power=code_power/bits_per_symbol; %比特功率 noise_power=10*log10((bit_power/(10^(snr_db/10)))); %噪声功率 noise=wgn(1,length(Tx_data),noise_power,'complex'); %产生GAUSS白噪声信号 Y7=Tx_data+noise; %接受到的信号 %--------------串并变换--------------------------------------------- Y6=reshape(Y7,FS+G,Ns).'; %-------------------------去保护间隔------------------------ for k=1:Ns; for i=1:FS; Y5(k,i)=Y6(k,i+G); end end Y4=fft(Y5,FS,2); Y3=Y4(:,carriers); if show_flag==1 figure(2); plot(Y4,'*r'); % 接收信号的星座图 title('接收信号的星座图（未经信道估计）'); axis([-4, 4, -4, 4]); grid on end %--------LS信道估计----------------------------------------------------- H=[]; Y2=Y3(:,signal); Rx_training_symbols=Y3(:,pilot); Rx_training_symbols0=reshape(Rx_training_symbols,Ns*Np,1); training_symbol0=reshape(training_symbols,1,Ns*Np); training_symbol1=diag(training_symbol0); training_symbol2=inv(training_symbol1); Hls=training_symbol2*Rx_training_symbols0; Hls1=reshape(Hls,Ns,Np); HLs=[]; HLs1=[]; if ceil(para/LI)==para/LI for k=1:Np-1 HLs2=[]; for t=1:LI HLs1(:,1)=(Hls1(:,k+1)-Hls1(:,k))*(t-1)./LI+Hls1(:,k); HLs2=[HLs2,HLs1]; end HLs=[HLs,HLs2]; end else for k=1:Np-2 HLs2=[]; for t=1:LI HLs1(:,1)=(Hls1(:,k+1)-Hls1(:,k))*(t-1)./LI+Hls1(:,k); HLs2=[HLs2,HLs1]; end HLs=[HLs,HLs2]; end HLs3=[]; for t=1:mod(para,LI) HLs1(:,1)=(Hls1(:,Np)-Hls1(:,Np-1))*(t-1)./LI+Hls1(:,Np-1); HLs3=[HLs3,HLs1]; end; HLs=[HLs,HLs3]; end Y1=Y2./HLs; if show_flag==1 figure(3); plot(Y1,'*r'); % 接收信号的星座图 title('接收信号的星座图（经过信道估计）'); axis([-4, 4, -4, 4]); grid on end %-------并串变换------------------------------------------------------ YY1=reshape(Y1.',1,N_number/bits_per_symbol); %------------QPSK解调------------------------------------------------ y_real=sign(real(YY1)); y_image1=sign(imag(YY1)); y_re=y_real./sqrt(2); y_im=y_image1./sqrt(2); r00=[]; r01=[]; r10=[]; r11=[]; for k=1:length(y_real); r10=[r10,[y_real(k),y_image1(k)]]; end; for k=1:length(y_re); r11=[r11,[y_re(k),y_im(k)]]; end; XX(find(r01>0))=1; %--------------计算在不同信噪比下的误比特率并作图--------------------------------- diff_bits=s-r11; ber_snr=0; %纪录误比特数 for k=1:N_number