receive_for_channel.m

完整的空时码链路仿真多发射天线多接收天线空时分集系统的具体代码实现和误码性能评估

function [nr_of_errors_in_rate, theta1, sample_nr, combined_signal]=receive_for_channel(received_vector,training_sequence1,data_block,fs,T,fc,pulsetype)

%   [output1, output2]=functionname(input1, input2)
%
%	Variable:	Explanation:
%	nr_of_errors_in_rate    -   Percent of bits with error
%   theta1                  -   the angle estimated by used channel-estimator
%   
%	received_vector     -   received vector from channel (1x1 experiment)
%   training_sequence1  -   used training sequence
%   data_block          -   true data-block sent over channel
%   fs                  -   used sample-frequency
%   T                   -   symbol-time   
%   fc                  -   carrier-frequency
%   pulsetype           -   used pulsetype, 2 for root-raised-cosine
%
%   Short Theoretical Background for the Function:
%
%   Assuming received_vector is normalized and correct size.
%   Used when doing experiment over real acoustic channel the 27th.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
%%% Function part of simulation for Space-Time
%%% coding project, group Grey-2001.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%   Author: Stefan Uppg錼d
%   Date: 27/3-2001
%   Version: 1.0
%   Revision (Name & Date & Comment):
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    %%%
    %%% Only recieving in receive-antenna 1.
    %%%
    model = 0;
    training_length1 = length(training_sequence1);
    training_length2 = training_length1;

    
    receive1 = received_vector;
    
    %%%
    %%% Make the signal unbiased, removing the signals mean.
    %%%
    
    [receive1]=remove_mean(receive1);
    
    %%%
    %%% Down-conversion and lowpassfiltering.
    %%%
    
    [quad, inphase]=down_converter(receive1,fc,fs,T,(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.');
    
     
    %%%%%%%%
    %%%%%%%% Do the frequency-offset compensation if initial-state.
    %%%%%%%%
    
    run_offset = 1;
    if (run_offset == 0)
        [freq_diff, delta_theta, alfa]=freq_offset(inphase, quad, fs, fc)
    end
  
    %break;
    %freq_diff = 0.0237;
    %delta_theta = 2*pi*(((1/(1-freq_diff/fc))-1)*fc*(1/(fs*(1-(freq_diff/fc)))));
    %delta_theta = 9.3490*10^-6;       % estimated angle-shift/sampel for sinus sampled at 16 kHz.
    %delta_theta = -2.00*10^-5;
    
    %a = 0:(length(inphase)-1);
    %rotation_vector = exp(-j*a*delta_theta);                               % Rotation compensating vector.
     
    %compensated_received = complex(inphase,quad) .* rotation_vector;
    %inphase = real(compensated_received);
    %quad    = imag(compensated_received);
    
    
    
    %%%
    %%% Matchedfiltering and lowpassfiltering.
    %%%
    
    [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
    %%%
    
    [corr_maxi,sample_nri]=synchronization_long(mf_inphase_block, fs, T, training_sequence1, model)  %%% CALLING THE SYNC_LONG FUNCTION!
    [corr_maxq,sample_nrq]=synchronization_longb(mf_quad_block, fs, T, training_sequence1, model)
    
    if corr_maxq > corr_maxi       % choose the correlation with the biggest max value
        sample_nr = sample_nrq;
    else
        sample_nr = sample_nri;
    end
    
    
    %%%
    %%% Down-Sampling
    %%%
    
    block_length=length(data_block) + length(training_sequence1);
    [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('received data and samplepoints. (not yet combined!)');
    subplot(1,2,1), stem([training_sequence1 data_block]), title('Sent data.');
    
    figure(4), subplot(1,2,1), plot(inphase_symbols,quad_symbols,'x'), axis([-2 2 -2 2]), title('Signals after MF and sampled')
    
    %%
    %% Calculating influence of freq_offset. IS INSTEAD DONE AFTER DOWNCONVERTER.
    %%
    
    %[quad_symbols, inphase_symbols, theta]=freq_offset_compensate(quad_symbols,inphase_symbols);
    %theta
    %figure(7), plot(inphase_symbols,quad_symbols,'x'), axis([-6 6 -6 6]), title('Signals after freq-offset compensation.'), grid on
	
    %%%
    %%% Estimating Channel 1 and 2.
    %%%
    
   
    
    %[alpha1,theta1] = chan_estim3(quad_symbols(1:training_length1),inphase_symbols(1:training_length1),bpsk(training_sequence1,model));
    %figure(8), plot(theta1)
    
    [alpha1,theta1] = channel_estimator(quad_symbols(1:training_length1), ...
       inphase_symbols(1:training_length1), training_sequence1, model, 1)
    
    if model == 1
       %[alpha2,theta2]=chan_estim3(quad_symbols(training_length1+1:training_length1+ ...
       %training_length2),inphase_symbols(training_length1+1:training_length1+ ...
       %training_length2), bpsk(training_sequence2,model))
        
       [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(alpha1, theta1, alpha2, theta2, ...
        inphase_symbols, quad_symbols, model);

    figure(5), plot(combined_signal,'x'), axis([-6 6 -6 6]), title('Signals after combiner, just before detector.')
    grid on
    
    %%%
    %%% 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)