stbc_ofdm_csi.m

是关于空时编码的nrs

%==========================================================================
% "Channel estimation via training in time domain and tracking in frequcy 
% domain for STBC-OFDM Systems"
% Sun Jie-ting, 08.11.2004, East China Uni. Science and Technology,Shanghai
% Results of SER
%==========================================================================
function data=STBC_OFDM_CSI(Number_Relz,NoOFDMSymbol,NFFT,G,t_a,f_dmax,snr_min,snr_max)
%clc;
Nt = 2;
Nr = 1;
%NFFT = 128;               % FFT length
%G = 10;                   % Guard interval length
%t_a = 0.8*10^(-6);       % Sampling duration of wireless communication
%NoOFDMSymbol = 1;        %Number of OFDM symbol
OFDMSymbolbits = NFFT;      %Number of bits per OFDM symbol conveys
length_data = NoOFDMSymbol * NFFT;  
                            % The total data length
%-------------------------------------------------
% Parameters for Monte Carlo channel
%-------------------------------------------------
symbol_duration = NFFT * t_a;   %OFDM symbol duration
number_of_summations = 40;      % Number of summations for Monte-Carlo method
%f_dmax = 50.0;                  % Maximum Doppler frequency
load h_decimation.am -ascii;
h1_initial = h_decimation;
h2_initial = h_decimation;

N_P  = length(h_decimation);
step = 1;
symbol_error_rate = zeros(1,(snr_max-snr_min)/step+1);

for number_of_realization= 1: Number_Relz;

disp('number_of_realization');
disp(number_of_realization);
u1 = rand(N_P,number_of_summations); % A random variable
u2 = rand(N_P,number_of_summations); % A random variable
%---------------------------
% Data for STBC demodulation
%---------------------------
data_for_destbc = zeros(2,1,16);
data_qpsk = [1+j;-1+j;-1-j;1-j]/sqrt(2);
for k=1:4
    for m=1:4
        data_for_destbc(:,:,4*(k-1)+m) = [data_qpsk(k);data_qpsk(m)];
    end 
end

%----------------------------
% QPSK modulator in base band
%----------------------------------------------
BitFrameC1=(2*round(rand(Nt,OFDMSymbolbits/2,NoOFDMSymbol))-1)/sqrt(Nt);
QpskDataC1=BitFrameC1(1,:,:)+j*BitFrameC1(2,:,:);

BitFrameC2=(2*round(rand(Nt,OFDMSymbolbits/2,NoOFDMSymbol))-1)/sqrt(Nt);
QpskDataC2=BitFrameC2(1,:,:)+j*BitFrameC2(2,:,:);
%--------------------
% Alamouti space-time modulator in base band
%--------------------
Stbc1=zeros(1,OFDMSymbolbits,NoOFDMSymbol);
Stbc2=zeros(1,OFDMSymbolbits,NoOFDMSymbol);
for k=1:1:OFDMSymbolbits/2
    Stbc1(1,2*k-1,:)=QpskDataC1(1,k,:);
    Stbc1(1,2*k,:)=-conj(QpskDataC2(1,k,:));
    Stbc2(1,2*k-1,:)=QpskDataC2(1,k,:);
    Stbc2(1,2*k,:)=conj(QpskDataC1(1,k,:));
end

%------------------------------------------------------------------------
% Transmitted signal of trasmitt antena 1 to receive antenna (channel:h1)
%------------------------------------------------------------------------

%snr_min =0;
%snr_max =12;
%step = 1;
for snr = snr_min:step:snr_max; 
    disp('snr = ');
    disp(snr);


h1_frame = [];
rs1MP_frame = [];
initial_time=0;                 % Initial time

for i=1:NoOFDMSymbol;
   OFDM_signal_tem = OFDM_Modulator(Stbc1(1,:,i),NFFT,G);
   % OFDM signal from the first transmitt antenna is created
   
  [h1, t] = MCM_channel_model(u1, initial_time, number_of_summations, symbol_duration, ...,
       f_dmax, h1_initial);
  h1_frame = [h1_frame;h1];
  initial_time = t;
   
   rs1MP = conv(OFDM_signal_tem, h1);

   rs1MP_frame = [rs1MP_frame; rs1MP];
   clear OFDM_signal_tem;
end;


%------------------------------------------------------------------------
% Transmitted signal of antenna 2 to receive antenna 1 (channel: h2)
%-----------------------------------------------------------------------

h2_frame = [];
rs2MP_frame = [];

initial_time=0;                 % Initial time
for i=1:NoOFDMSymbol;
   OFDM_signal_tem = OFDM_Modulator(Stbc2(1,:,i),NFFT,G);
   % OFDM signal from the second antenna is created
   [h2, t] = MCM_channel_model(u2, initial_time, number_of_summations, symbol_duration, ...,
       f_dmax, h2_initial);
   h2_frame = [h2_frame;h2];
   initial_time = t;

   rs2MP = conv(OFDM_signal_tem, h2);
   rs2MP_frame = [rs2MP_frame; rs2MP];
   clear OFDM_signal_tem;
end;


%-----------------
% Recever: OFDM demodulator, channel estimation
%-----------------


for i=1:NoOFDMSymbol;
   rsBeforeAwgn_i = rs1MP_frame(i,:) + rs2MP_frame(i,:);
%    rs_i =   rsBeforeAwgn_i;
   rs_i = awgn(rsBeforeAwgn_i,snr,'measured','dB');
   Demodulated_rs_i = OFDM_Demodulator(rs_i,NFFT,NFFT,G);

   H1_i = fft([h1_frame(i,:) zeros(1,NFFT-N_P)]);
   H2_i = fft([h2_frame(i,:) zeros(1,NFFT-N_P)]);
%   X1 = Stbc1(:,:,i).*H1_i
%   X2 = Stbc2(:,:,i).*H2_i
   %--------------------------
   % Demodulated signal 
   %--------------------------
    for l=1:OFDMSymbolbits/2;
       R1=Demodulated_rs_i(2*l-1);
       R2=Demodulated_rs_i(2*l);
%       Y1 = X1(1,2*l-1,i)+X2(1,2*l-1,i)
%       Y2 = X1(1,2*l,i)+X2(1,2*l,i)
       R2conj = conj(R2);
       R_n2l=[R1;R2conj];

%       H1111=[H1_i(2*l-1) H2_i(2*l-1);H1_i(2*l) H2_i(2*l)]

       H_n2l = [H1_i(2*l-1) H2_i(2*l-1);conj(H2_i(2*l)) -conj(H1_i(2*l))];
       minNorm = 10000;
       num_min = 0;
        for m=1:16
            dec_norm = norm(R_n2l-H_n2l*data_for_destbc(:,:,m))^2;
            if dec_norm < minNorm;
                    minNorm = dec_norm;
                    num_min = m;
            end
         end
         deStbc = data_for_destbc(:,:,num_min);
         TrSTBC = [Stbc1(1,2*l-1,i);Stbc2(1,2*l-1,i)];
         if deStbc==TrSTBC
         else
             symbol_error_rate(snr-snr_min+1) = symbol_error_rate(snr-snr_min+1) + 1;
         end
   end;
end;    %NoOFDMSymbol
end;    %snr
end;    %realization
ser = symbol_error_rate/(length_data*Number_Relz);
%semilogy(snr_min:step:snr_max, ser,'b*');
%ylabel('SER');
%xlabel('SNR');

data = [snr_min:step:snr_max; ser]
save STBC_OFDM_CSI_data.am data -ascii;
clear all;