%%STBC-MIMO-OFDM.m clear all; i=sqrt(-1); IFFT_bin_length=512; %傅立叶变换抽样点数目 carrier_count=100; %子载波数目 symbols_per_carrier=66; %符号数/载波 cp_length=10; %循环前缀长度 addprefix_length=IFFT_bin_length+cp_length; M_psk=4; bits_per_symbol=log2(M_psk); %位数/符号 %O=[1 2;-2+j
1+j]; %Alamouti Scheme [x1 x2;-x2* x1*] 二天线发送矩阵 O=[1 -2 -3;2+j 1+j 0;3+j 0 1+j;0 -3+j 2+j]; %for [x1 -x2 -x3;x2* x1* 0;x3* 0 x1*;0 -x3* x2*] 三天线发送矩阵 co_time=size(O,1); Nt=size(O,2); %发射天线数目 Nr=2; %接收天线数目 num_X=1; for cc_ro=1:co_time for cc_co=1:Nt num_X=max(num_X,abs(real(O(cc_ro,cc_co)))); end end co_x=zeros(num_X,1); for con_ro=1:co_time %计算delta,epsilon,eta and conj matrices for con_co=1:Nt %用于确定矩阵“O”中元素的位置，符号以及共轭情况 if abs(real(O(con_ro,con_co)))~=0
delta(con_ro,abs(real(O(con_ro,con_co))))=sign(real(O(con_ro,con_co))); epsilon(con_ro,abs(real(O(con_ro,con_co))))=con_co;
co_x(abs(real(O(con_ro,con_co))),1)=co_x(abs(real(O(con_ro,con_co))),1)+1; eta(abs(real(O(con_ro,con_co))),co_x(abs(real(O(con_ro,con_co))),1))=con_ro; coj_mt(con_ro,abs(real(O(con_ro,con_co))))=imag(O(con_ro,con_co)); end end end eta=eta.'; eta=sort(eta); eta=eta.'; carriers = (1: carrier_count) +
(floor(IFFT_bin_length/4) - floor(carrier_count/2)); % 坐标： (1 to 100) + 14=(15:114) conjugate_carriers=IFFT_bin_length-carriers+2; % 坐标 ：256 - (15:114) + 1= 257 - (15:114) = (242:143) tx_training_symbols=training_symbol(Nt,carrier_count);
baseband_out_length = carrier_count * symbols_per_carrier; snr_min=3; %最小信噪比 snr_max=15; %最大信噪比 graph_inf_bit=zeros(snr_max-snr_min+1,2,Nr); %绘图信息存储矩阵 graph_inf_sym=zeros(snr_max-snr_min+1,2,Nr); for
SNR=snr_min:snr_max %开始仿真 clc disp('Wait until SNR=');disp(snr_max); SNR n_err_sym=zeros(1,Nr); n_err_bit=zeros(1,Nr); Perr_sym=zeros(1,Nr);
Perr_bit=zeros(1,Nr); re_met_sym_buf=zeros(carrier_count,symbols_per_carrier,Nr); re_met_bit=zeros(baseband_out_length,bits_per_symbol,Nr);
baseband_out=round(rand(baseband_out_length,bits_per_symbol)); %生成随机数用于仿真 de_data=bi2de(baseband_out); %二进制向十进制转换 data_buf=pskmod(de_data,M_psk,0); %PSK调制
carrier_matrix=reshape(data_buf,carrier_count,symbols_per_carrier); for
tt=1:Nt:symbols_per_carrier %取数为空时编码做准备，此处每次取每个子载波上连续的两个数 data=[]; for ii=1:Nt tx_buf_buf=carrier_matrix(:,tt+ii-1);
data=[data;tx_buf_buf]; end XX=zeros(co_time*carrier_count,Nt); for
con_r=1:co_time %进行空时编码 for con_c=1:Nt if abs(real(O(con_r,con_c)))~=0 if
imag(O(con_r,con_c))==0 XX((con_r-1)*carrier_count+1:con_r*carrier_count,con_c)=data((abs(real(O(con_r,con_c)))-1)*carrier_count+1:abs(real(O(con_r,con_c)))...
*carrier_count,1)*sign(real(O(con_r,con_c))); else XX((con_r-1)*carrier_count+1:con_r*carrier_count,con_c)=conj(data((abs(real(O(con_r,con_c)))-1)*carrier_count+1:abs(real(O(con_r,con_c)))...
*carrier_count,1))*sign(real(O(con_r,con_c))); end end end end %空时编码结束 XX=[tx_training_symbols;XX]; %添加训练序列
rx_buf=zeros(1,addprefix_length*(co_time+1),Nr); for rev=1:Nr for ii=1:Nt tx_buf=reshape(XX(:,ii),carrier_count,co_time+1);
IFFT_tx_buf=zeros(IFFT_bin_length,co_time+1); IFFT_tx_buf(carriers,:)=tx_buf(1:carrier_count,:);
IFFT_tx_buf(conjugate_carriers,:)=conj(tx_buf(1:carrier_count,:));
time_matrix=ifft(IFFT_tx_buf); time_matrix=[time_matrix((IFFT_bin_length-cp_length+1):IFFT_bin_length,:);time_matrix]; tx=time_matrix(:)'; %------------------------------------------------------------------------ %d=randint(1,4,[1,7]); %4多经信道模拟 %a=randint(1,4,[2,7])/10; tx_tmp=tx;
d=[4,5,6,2;4,5,6,2;4,5,6,2;4,5,6,2];
a=[0.2,0.3,0.4,0.5;0.2,0.3,0.4,0.5;0.2,0.3,0.4,0.5;0.2,0.3,0.4,0.5]; for jj=1:size(d,2) copy=zeros(size(tx)) ; for kk = 1 + d(ii,jj): length(tx) copy(kk) = a(ii,jj)*tx(kk - d(ii,jj)) ; end tx_tmp=tx_tmp+copy; end %------------------------------------------------------------------------ txch=awgn(tx_tmp,SNR,'measured'); %添加高斯白噪声
rx_buf(1,:,rev)=rx_buf(1,:,rev)+txch; end
rx_spectrum=reshape(rx_buf(1,:,rev),addprefix_length,co_time+1); rx_spectrum=rx_spectrum(cp_length+1:addprefix_length,:);
FFT_tx_buf=zeros(IFFT_bin_length,co_time+1); FFT_tx_buf=fft(rx_spectrum); spectrum_matrix=FFT_tx_buf(carriers,:); Y_buf=(spectrum_matrix(:,2:co_time+1)); Y_buf=conj(Y_buf'); spectrum_matrix1=spectrum_matrix(:,1); Wk=exp((-2*pi/carrier_count)*i); L=10; p=zeros(L*Nt,1); for jj=1:Nt for l=0:L-1 for kk=0:carrier_count-1 p(l+(jj-1)*L+1,1)=p(l+(jj-1)*L+1,1)+spectrum_matrix1(kk+1,1)*conj(tx_training_symbols(kk+1,jj))*Wk^(-(kk*l)); end end end %q=zeros(L*Nt,L*Nt); %for ii=1:Nt % for jj=1:Nt % for l1=0:L-1 % for l2=0:L-1 % for kk=0:carrier_count-1 % q(l2+(ii-1)*L+1,l1+(jj-1)*L+1)= q(l2+(ii-1)*L+1,l1+(jj-1)*L+1)+tx_training_symbols(kk+1,ii)*conj(tx_training_symbols(kk+1,jj))*Wk^(-(kk*(-l1+l2))); % end % end % end % end %end %h=inv(q)*p; h=p/carrier_count;
H_buf=zeros(carrier_count,Nt); for ii=1:Nt for kk=0:carrier_count-1 for l=0:L-1 H_buf(kk+1,ii)=H_buf(kk+1,ii)+h(l+(ii-1)*L+1,1)*Wk^(kk*l); end end end
H_buf=conj(H_buf'); RRR=[]; for kk=1:carrier_count Y=Y_buf(:,kk); H=H_buf(:,kk); for co_ii=1:num_X for co_tt=1:size(eta,2) if eta(co_ii,co_tt)~=0 if
coj_mt(eta(co_ii,co_tt),co_ii)==0 r_til(eta(co_ii,co_tt),:,co_ii)=Y(eta(co_ii,co_tt),:); a_til(eta(co_ii,co_tt),:,co_ii)=conj(H(epsilon(eta(co_ii,co_tt),co_ii),:)); else r_til(eta(co_ii,co_tt),:,co_ii)=conj(Y(eta(co_ii,co_tt),:));
a_til(eta(co_ii,co_tt),:,co_ii)=H(epsilon(eta(co_ii,co_tt),co_ii),:); end end end end
RR=zeros(num_X,1); for iii=1:num_X %Generate decision statistics for the transmitted signal \"xi\" for ttt=1:size(eta,2) if eta(iii,ttt)~=0
RR(iii,1)=RR(iii,1)+r_til(eta(iii,ttt),1,iii)*a_til(eta(iii,ttt),1,iii)*delta(eta(iii,ttt),iii); end end end RRR=[RRR;conj(RR')]; end r_sym=pskdemod(RRR,M_psk,0); re_met_sym_buf(:,tt:tt+Nt-1,rev)=r_sym; end end
re_met_sym=zeros(baseband_out_length,1,Nr); for rev=1:Nr
re_met_sym_buf_buf=re_met_sym_buf(:,:,rev); re_met_sym(:,1,rev)=
re_met_sym_buf_buf(:); re_met_bit(:,:,rev)=de2bi(re_met_sym(:,1,rev)); for con_dec_ro=1:baseband_out_length if
re_met_sym(con_dec_ro,1,rev)~=de_data(con_dec_ro,1)
n_err_sym(1,rev)=n_err_sym(1,rev)+1; for con_dec_co=1:bits_per_symbol if re_met_bit(con_dec_ro,con_dec_co,rev)~=baseband_out(con_dec_ro,con_dec_co) n_err_bit(1,rev)=n_err_bit(1,rev)+1; end end end end graph_inf_sym(SNR-snr_min+1,1,rev)=SNR; graph_inf_bit(SNR-snr_min+1,1,rev)=SNR;
Perr_sym(1,rev)=n_err_sym(1,rev)/(baseband_out_length); %Count number of error bits and symbols graph_inf_sym(SNR-snr_min+1,2,rev)=Perr_sym(1,rev); Perr_bit(1,rev)=n_err_bit(1,rev)/(baseband_out_length*bits_per_symbol); graph_inf_bit(SNR-snr_min+1,2,rev)=Perr_bit(1,rev); end end for rev=1:rev x_sym=graph_inf_sym(:,1,rev); %Generate plot y_sym=graph_inf_sym(:,2,rev); subplot(Nr,1,rev); semilogy(x_sym,y_sym,'k-v'); axis([2 16 0.0001 1]); xlabel('SNR, [dB]'); ylabel('Symbol Error Probability'); grid on %hold on end %hold off %for
rev=1:rev %x_bit=graph_inf_bit(:,1,rev); %y_bit=graph_inf_bit(:,2,rev); %subplot(2,1,2); %semilogy(x_bit,y_bit,'k-v'); %axis([2 16 0.0001 1]); %xlabel('SNR, [dB]'); %ylabel('Bit Error Probability'); %grid on %hold on %end %hold off %%training_symbol.M function
tx_training_symbols=training_symbol(Nt,carrier_count) j=sqrt(-1); Wk=exp((-2*pi/carrier_count)*i); training_symbols= [ 1 j j 1 -1 -j -j -1 1 j j 1 -1 -j -j -1 1 j j 1 -1 -j -j -1 1 j j 1 -1 -j -j -1 1 j j 1 -1 ... -j -j -1 1 j j 1 -1 -j -j -1 1 j j 1 -1 -j -j -1 1 j j 1 -1 -j -j -1
1 j j 1 -1 -j -j -1 1 ... j j 1 -1 -j -j -1 1 j j 1 -1 -j -j -1 1 j j 1 -1 -j -j -1 1 j j 1 ]';
tx_training_symbols=[]; for ii=1:carrier_count training_symbols_buf=[]; for jj=1:Nt training_symbols_buf=[training_symbols_buf,Wk^(-floor(carrier_count/Nt)*(jj-1)*ii) *training_symbols(ii,1)]; end
tx_training_symbols=[tx_training_symbols;training_symbols_buf]; end
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