simulation_for_channel.m

这个程序主要是实现空时编码的matlab编解码仿真。

function [sent_signal1,sent_signal2,training_sequence1,training_sequence2,data_block,fs,T,fc,pulsetype]=simulation_for_channel()

%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
%%% Function part of simulation for Space-Time
%%% coding project, group Grey-2001.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%   Author: Stef and Fred
%   Date: 2001-03-19
%   Version: 1.0
%   Revision (Name & Date):
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clf, clear

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% Initializations
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

N               = 500;                   % Number of total data
block_size      = N;                   % block_size must be multiple of N.
training_length1 = 200;                   % training_length + N must be an even number!
training_length2 = training_length1;

fc              = 2500;                  % Carrier-frequency
fs              = 8000;                 % Sampling-frequency
T               = 0.001;                  % Symboltime

pulsetype       = 4;							% 1: rect 2:root-rais-cos 3:hamming 4:raised-cos
model		    = 0;							% 0: no Alamouti (1*1) 1: Alamouti (2*1)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% Running Simulation
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

compared_error = [];
for(model=model:model)

EbN0error = [];
for(EbN0=10:10)
    error = []; 
    data = random_data(N);      % Generate random source-data
    for(i=0:(length(data)/block_size)-1)
    
    data_block = get_datablock(data,block_size,i);
    symbols = bpsk(data_block,model);
    
    [s_antenna1, s_antenna2] = alamouti(symbols,model);         % set = 1, alamouti coding is performed!
    
    if model == 1
        [s_antenna1,s_antenna2,training_sequence1,training_sequence2]=add_training2(s_antenna1,s_antenna2,...
            training_length1,training_length2,0);               % type = 0, random training-sequence.
        outdata_block = [training_sequence1 training_sequence2 data_block];
        
    elseif model == 0
        [s_antenna1,training_sequence1]=add_training(s_antenna1,training_length1,0)  % type = 0, random training-sequence.
        outdata_block = [training_sequence1 data_block];
    end % model == 1
       
    
    %%%
    %%% Antenna 1
    %%%
    
    [s1,t1]=pulseshape(s_antenna1,fs,pulsetype,T);          % Apply pulseshaping
    [spb1]=carrier(s1,fc,fs,T);
    [Spb1,f]=ftfast(spb1,t1);
    
    %%%
    %%% Antenna 2
    %%%
    
    [s2,t2]=pulseshape(s_antenna2,fs,pulsetype,T);          % Apply pulseshaping
    [spb2]=carrier(s2,fc,fs,T);
    
    %%%
    %%% Plotting results
    %%%
    
    rows=2;
    cols=3;
    
    figure(1), subplot(rows,cols,1), plot(s1)
    subplot(rows,cols,2), plot(s2)
    
    subplot(rows,cols,3) 
    %axis([0 2*fc 0.01 1]);
    plot(1:length(spb1),spb1);
    title('Signal on antenna 1')
    xlabel('sampel')
   
    subplot(rows,cols,4) 
    %axis([0 2*fc 0.01 1]);
    plot(1:length(spb2),spb2);
    title('Signal on antenna 2')
    xlabel('sampel')
    
    subplot(rows,cols,5)
    plot(f,abs(Spb1))
    title('Spectrum (Antenna 1)');
    xlabel('Frequency [Hz]');
    
    
    sent_signal1 = spb1;
    sent_signal2 = spb2;
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    break
    %%%%%%%%%%%%%%%%%
    % Simulation stops here..
    %%%%%%%%%%%%%%%%%
    
    
    %%%
    %%% Simulating with simple channel 1 & 2.
    %%%
    
    %[spb1_thru_channel]=channel(spb1,[1 -0.5 -0.6 0.3 -0.2],1);
    [spb1_thru_channel]=channel(spb1,1,1);
    [spb1_thru_channel]=awgn(spb1_thru_channel,EbN0); % Input argument is SNR in decibel.
    
    [spb2_thru_channel]=simple_test_channel(spb2,2);
    [spb2_thru_channel]=awgn(spb2_thru_channel,EbN0); % Input argument is SNR in decibel.

    
    %%%
    %%% Only recieving in recieve-antenna 1.
    %%%
    
    recieve1 = spb1_thru_channel + spb2_thru_channel;
    [quad,inphase]=down_converter(recieve1,fc,fs,T,2*(fc/(fs/2)),20);
    
    figure(2), subplot(2,2,1), plot(1:length(quad),quad);
    title('Quad after down-conv.');
    subplot(2,2,2), plot(1:length(inphase),inphase);
    title('Inphase after down-conv.');
    
    [mf_quad_block]=matched_filter(fs, T, pulsetype, quad);    % Quadrature-part
    [mf_inphase_block]=matched_filter(fs, T, pulsetype, inphase);    % Inphase-part
    
    subplot(2,2,3), plot(1:length(mf_quad_block),mf_quad_block);
    title('Quad after MF');
    subplot(2,2,4), plot(1:length(mf_inphase_block),mf_inphase_block);
    title('Inphase after MF');
    
    %%%
    %%% Performing synchronization
    %%%
    
    [sample_nr]=synchronization(mf_inphase_block, fs, T, training_sequence1, model)
    block_length=length(outdata_block);
    [inphase_symbols]=down_sampler(mf_inphase_block,sample_nr,fs,T,block_length);
    [quad_symbols]=down_sampler(mf_quad_block,sample_nr,fs,T,block_length);
    
    figure(3), subplot(1,2,2), plot(mf_inphase_block), hold on
    for(i=0:block_length-1)
        plot(i*(fs*T)+sample_nr,inphase_symbols(i+1),'o');
    end
    hold off
    title('Recieved data and samplepoints. (not yet combined!)');
    subplot(1,2,1), plot(outdata_block), axis([-5 35 -0.5 1.5]), title('Sent data.');
    
        
    %%%
    %%% Forcing phase-shift pi/4.
    %%%
    alfa = abs(inphase_symbols + j*quad_symbols);
    fi = angle(inphase_symbols + j*quad_symbols);
    fi = fi + 5*(pi/8);
    quad_symbols = alfa.*sin(fi);
    inphase_symbols = alfa.*cos(fi);
       
    figure(4), subplot(1,2,1), plot(inphase_symbols,quad_symbols,'x'), axis([-2 2 -2 2]), title('Signals after MF and sampled')
    
	%%%
    %%% Estimating Channel 1 and 2.
    %%%
    
    %[alpha1,theta1]=channel_estimator_lms(quad_symbols(1:training_length1),inphase_symbols(1:training_length1)...
    %    , bpsk(training_sequence1,1))
    [alpha1,theta1] = channel_estimator(quad_symbols(1:training_length1), ...
       inphase_symbols(1:training_length2), training_sequence1, model, 1)
    if model == 1
       %[alpha2,theta2]=channel_estimator_lms(quad_symbols(training_length1+1:training_length1+ ...
       %training_length2),inphase_symbols(training_length1+1:training_length1+ ...
       %training_length2), bpsk(training_sequence2,1))
        
       [alpha2,theta2] = channel_estimator(quad_symbols(training_length1+1:training_length1+ ...
       training_length2), inphase_symbols(training_length1+1:training_length1+ ...
       training_length2), training_sequence2, model, 2)
    elseif model == 0
        alpha2 = 1;
        theta2 = 0;
    end
    
    % set true values instead:
    %alpha1 = 1;
    %theta1 = 0;
    %alpha2 = 1;
    %theta2 = 0;
    
     %%%
     %%% No combiner used since only 1 antenna is used to send from so far.
     %%%
     
     [combined_signal]=combiner_var(alpha1, theta1, alpha2, theta2, ...
        inphase_symbols, quad_symbols, model);

     figure(5), plot(combined_signal,'x'), axis([-6 6 -6 6]), title('Signals after combiner')
    %%%
    %%% Detector
    %%%
     
    inphase_symbols = real(combined_signal);
    
    [indata_est,training1_est,training2_est]=detector(inphase_symbols,training_length1,training_length2,model);
    disp('Received data is:')
    indata_est
    disp('Sent data is:')
    data_block
    nr_of_errors = sum(abs(data_block-indata_est))
    nr_of_errors_in_rate = nr_of_errors/length(data_block)
    error = [error nr_of_errors_in_rate];
    end
    error = mean(error);
    EbN0error = [EbN0error error];
end
EbN0error
compared_error = [compared_error EbN0error'];
end
%compared_error
%figure(11)
%semilogy(1:length(compared_error(:,1)),compared_error(:,1),'blue',1:length(compared_error(:,2)),compared_error(:,2),'green')
sent_signal = spb1;