eqber_graphics.m

Adaptive Filter. This script shows the BER performance of several types of equalizers in a static ch

function varargout = eqber_graphics(plotType, varargin)
% EQBER_GRAPHICS - Generate and update plots for the eqber demo.
%   [hBER, hLegend, legendString, hLinSpec, hDfeSpec, hErrs, ...
%       hText1, hText2, hFit, hEstPlot] = ...
%       eqber_graphics('init', chnl, EbNo, idealBER, nBits)
%   generates handles to be used later in the simulation run.
%   Inputs:
%      chnl         - channel impulse response
%      EbNo         - vector of Eb/No values
%      idealBER     - ideal BPSK BER values corresponding to the EbNo vector
%      nBits        - number of bits in a data block
%   Outputs:
%      hBER         - handle to a line in the BER plot
%      hLegend      - vector of handles corresponding to visible legend entries 
%                     in the BER plot
%      legendString - cell array of legend strings for the BER plot
%      hLinSpec     - line handle for the spectrum plot of the linearly 
%                     equalized signal
%      hDfeSpec     - line handle for the spectrum plot of the DFE equalized
%                     signal
%      hErrs        - line handle to a bar plot showing burst error performance
%      hText1       - first text handle for the burst error plot
%      hText2       - second text handle for the burst error plot
%      hFit         - line handle for fitted BER curves
%      hEstPlot     - line handle for the channel estimate plot
%
%
%   hSpecPlot = eqber_graphics('sigspec', eqType, hSpecPlot, nBits, PreD)
%   updates the spectrum plots for adaptively equalized signals.
%   Inputs:
%      eqType       - 'linear', 'dfe', or 'mlse'
%      hSpecPlot    - line handle for the spectrum plot
%      nBits        - number of bits in a data block
%      PreD         - equalized, predetected signal
%   Outputs:
%      hSpecPlot - line handle for the spectrum plot
%
%
%   [hErrs, hText1, hText2] = eqber_graphics('bursterrors', eqType, ...
%      mlseType, firstErrPlot, refMsg, testMsg, nBits, hErrs, hText1, hText2)
%      updates the burst error performance plots.
%   Inputs:
%      eqType       - 'linear', 'dfe', or 'mlse'
%      mlseType     - 'ideal' or 'imperfect'
%      firstErrPlot - flag indicating whether the current plot is the first 
%                     burst error performance plot for the current equalizer
%      refMsg       - transmitted signal, used to find bit errors
%      testMsg      - received signal, used to find bit errors
%      nBits        - number of bits in a data block
%      hErrs        - line handle to a bar plot showing burst error performance
%      hText1       - first text handle for the burst error plot
%      hText2       - second text handle for the burst error plot
%   Outputs:
%      hErrs        - line handle to a bar plot showing burst error performance
%      hText1       - first text handle for the burst error plot
%      hText2       - second text handle for the burst error plot
%
%
%   [hBER, hLegend, legendString] = eqber_graphics('simber', eqType, ...
%      mlseType, firstBlk, EbNoIdx, EbNo, BER, hBER, hLegend, legendString)
%      updates the BER plot.
%   Inputs:
%      eqType       - 'linear', 'dfe', or 'mlse'
%      mlseType     - 'ideal' or 'imperfect'
%      firstBlk     - flag indicating whether the current data block is the
%                     first one being processed for the current equalizer type
%      EbNoIdx      - index over the range of EbNo
%      EbNo         - vector of Eb/No values
%      hBER         - line handle to the current line in the BER plot
%      hLegend      - vector of handles corresponding to visible legend entries 
%                     in the BER plot
%      legendString - cell array of legend strings for the BER plot
%   Outputs:
%      hBER         - line handle to the current line in the BER plot
%      hLegend      - vector of handles corresponding to visible legend entries 
%                     in the BER plot
%      legendString - cell array of legend strings for the BER plot
%
%
%   hFit = eqber_graphics('fitber', eqType, mlseType, hFit, EbNoIdx, EbNo, BER)
%   updates the curve fit to the simulated BER data.
%   Inputs:
%      eqType       - 'linear', 'dfe', or 'mlse'
%      mlseType     - 'ideal' or 'imperfect'
%      hFit         - line handle to the current BER curve fit
%      EbNoIdx      - index over the range of EbNo
%      EbNo         - vector of Eb/No values
%      BER          - vector of BER values corresponding to the Eb/No values
%   Outputs:
%      hFit         - line handle to the current BER curve fit
%
%
%   hEstPlot = eqber_graphics('chnlest', chnlEst, chnlLen, excessEst, ...
%   nBits, firstEstPlot, hEstPlot) updates the channel estimate plot for the
%   MLSE algorithm.
%   Inputs:
%      chnlEst      - impulse response of estimated channel
%      chnlLen      - length of estimated channel impulse response
%      excessEst    - the difference between the length of the estimated channel
%                     impulse response and the actual channel impulse response
%      nBits        - number of bits in a data block
%      firstEstPlot - flag indicating whether the current channel estimate plot 
%                     is the first one
%      hEstPlot     - line handle to the channel estimate plot
%   Outputs:
%      hEstPlot     - line handle to the channel estimate plot

%   Copyright 1996-2004 The MathWorks, Inc.
%   $Revision: 1.1.4.1 $  $Date: 2004/06/30 23:03:09 $

% ------------------------------------------------------------------------------

switch plotType
    case 'init'
        [chnl, EbNo, idealBER, nBits] = deal(varargin{:});
        
        % Plot the unequalized channel
        plot_uneqchnl(chnl);
        
        % Plot the ideal BPSK BER curve
        [hBER, hLegend, legendString] = plot_idealber(EbNo, idealBER);
        
        % Initialize a figure to display the linearly equalized signal spectrum
        hLinSpec = plot_sigspec('init', 'linear', nBits);
        
        % Initialize a figure to display the DFE equalized signal spectrum
        hDfeSpec = plot_sigspec('init', 'dfe', nBits);
        
        % Initialize a figure to display the burst error performance of the
        % linear equalizer, DFE equalizer, MLSE equalizer with an ideal channel
        % estimate, and an MLSE equalizer with an imperfect channel estimate
        [hErrs, hText1, hText2] = plot_bursterrors('init', [], [], []);
        
        % Initialize a dummy line handle for BER curve fitting
        set(0, 'CurrentFigure', get(get(hBER, 'Parent'), 'Parent'));
        hFit = semilogy(0, 1);
        
        % Initialize a figure to display the frequency response of the imperfect
        % channel estimate
        hEstPlot = plot_chnlest('init', nBits);
        
        
        varargout{1}  = hBER;
        varargout{2}  = hLegend;
        varargout{3}  = legendString;
        varargout{4}  = hLinSpec;
        varargout{5}  = hDfeSpec;
        varargout{6}  = hErrs;
        varargout{7}  = hText1;
        varargout{8}  = hText2;
        varargout{9}  = hFit;
        varargout{10} = hEstPlot;
        
    case 'sigspec'
        hSpecPlot = plot_sigspec('update', varargin{:}); 
        varargout{1} = hSpecPlot;
        
    case 'bursterrors'
        [hErrs, hText1, hText2] = plot_bursterrors('update', varargin{:});
        varargout{1} = hErrs;
        varargout{2} = hText1;
        varargout{3} = hText2;
        
    case 'simber'
        [hBER, hLegend, legendString] = plot_simber(varargin{:});
        varargout{1} = hBER;
        varargout{2} = hLegend;
        varargout{3} = legendString;
        
    case 'fitber'
        hFit = plot_fitber(varargin{:});
        varargout{1} = hFit;
        
    case 'chnlest'
        hEstPlot = plot_chnlest('update', varargin{:});
        varargout{1} = hEstPlot;
end

% ------------------------------------------------------------------------------

function plot_uneqchnl(chnl);
% PLOT_UNEQCHNL - Plot the frequency response of the unequalized channel
%   Inputs:
%      chnl - channel impulse response

% Generate a normalized frequency vector from -pi to pi
FFTlen   = 2048;
freq = [-FFTlen/2 : (FFTlen/2)-1]' * (2*pi/FFTlen);

% Generate the normalized frequency response
chnlLen  = length(chnl);
FFTchnl = [chnl; zeros(FFTlen - chnlLen, 1)];
magFFT = abs(fft(FFTchnl));
plot(freq, 20*log10(fftshift(magFFT/max(magFFT))));

axis([-3.14 3.14 -40 10]);
pos = figposition([0 45 33 33]);  % for multiple screen resolutions
set(gcf, 'Position', pos);
title('Unequalized Channel Frequency Response');
xlabel('Normalized Frequency (rad/s)');
ylabel('Normalized Magnitude Squared (dB)');
drawnow;

% ------------------------------------------------------------------------------

function [hBER, hLegend, legendString] = plot_idealber(EbNo, idealBER)
% PLOT_IDEALBER - Plot the BER for ideal BPSK
%   Inputs:
%      EbNo         - vector of Eb/No values
%      idealBER     - ideal BER values corresponding to the EbNo values
%   Outputs:
%      hBER         - line handle to the current line in the BER plot
%      hLegend      - vector of handles corresponding to visible legend entries 
%                     in the BER plot
%      legendString - cell array of legend strings for the BER plot

figure; pos = figposition([33.3 45 36 36]); figBER = gcf;
set(figBER, 'Position', pos);  % for multiple screen resolutions
axBER = axes;
set(axBER, 'YScale'    , 'log', ...
           'XLim'      , [0 16], ...
           'YLim'      , [1e-6 1], ...
           'XTick'     , [0:2:16], ...
           'XGrid'     , 'on', ...
           'YGrid'     , 'on', ...
           'YMinorGrid', 'off', ...
           'Title'     , text('String','Equalizer BER Comparison'), ...
           'XLabel'    , text('String', 'Eb/No (dB)'), ...
           'YLabel'    , text('String', 'BER'));

hold on; hBER = semilogy(EbNo, idealBER);
legendString = 'Ideal BPSK      ';
hLegend = hBER;
legend(hLegend, legendString, 'Location', 'SouthWest');
drawnow;

% ------------------------------------------------------------------------------

function h = plot_sigspec(plotType, eqType, varargin)
% PLOT_SIGSPEC - Initialize or update a plot of an equalized signal spectrum
%   Inputs:
%      plotType - 'init' or 'update' 
%      eqType   - 'linear' or 'dfe'
%      h        - line handle to the signal spectrum plot
%      nBits    - number of bits in a data block
%      PreD     - equalized, predetected signal
%   Outputs:
%      h        - line handle to the signal spectrum plot
        
% On initialization, set up all the figure properties and make the figure
% invisible.  On update, simply make the figure visible and reset the values of
% the plotted data.
switch plotType
    case 'init'
        % Generate a frequency vector
        nBits = varargin{1};
        freq = [-nBits/2 : 4 : (nBits/2)-1]' * (2*pi/nBits);
        
        figure; h = plot(freq, freq);  % initialize with dummy data
        fig = get(get(h, 'Parent'), 'Parent');
        set(fig, 'Visible', 'off');
        axis([-3.14 3.14 -40 10]);
        xlabel('Normalized Frequency (rad/s)');
        ylabel('Normalized Power Spectrum (dB)');
        
        if (strcmpi(eqType, 'linear'))
            pos  = figposition([0 5 33 33]);
            figTitle = 'Linearly Equalized Signal Power Spectrum';
            color    = [0 0 0];
        elseif (strcmpi(eqType, 'dfe'))
            pos  = figposition([33.3 5 33 33]);
            figTitle = 'Decision Feedback Equalized Signal Power Spectrum';
            color    = [1 0 0];
        end
        title(figTitle);
        set(fig, 'Position', pos);  % for multiple screen resolutions
        set(h, 'Color', color);