Index exceeds matrix dimensions ??

h = scatterplot(sqrt(nsamp)*ynoisy(1:nsamp*5e3),nsamp,0,'g.');

Index exceeds matrix dimensions ?? Error in ==> grd at 99 h = scatterplot(sqrt(nsamp)*ynoisy(1:nsamp*5e3),nsamp,0,'g.');

what is my problem? Just copy of :http://www.mathworks.com/help/toolbox/comm/ug/a1067963807.html#top_of_page

Answer 1

[Friedrich]

Hi Ali,

please try to run the following code:

%%Setup
% Define parameters.
M = 16;                 % Size of signal constellation
k = log2(M);            % Number of bits per symbol
n = 3e4;                % Number of bits to process
nsamp = 1;              % Oversampling rate
hMod = modem.qammod(M); % Create a 16-QAM modulator

%%Signal Source
% Create a binary data stream as a column vector.
x = randint(n,1); % Random binary data stream

% Plot first 40 bits in a stem plot.
stem(x(1:40),'filled');
title('Random Bits');
xlabel('Bit Index'); ylabel('Binary Value');

%%Bit-to-Symbol Mapping
% Convert the bits in x into k-bit symbols.
xsym = bi2de(reshape(x,k,length(x)/k).','left-msb');

%%Stem Plot of Symbols
% Plot first 10 symbols in a stem plot.
figure; % Create new figure window.
stem(xsym(1:10));
title('Random Symbols');
xlabel('Symbol Index'); ylabel('Integer Value');

%%Modulation
y = modulate(modem.qammod(M),xsym); % Modulate using 16-QAM.

%%Transmitted Signal
ytx = y;

%%Channel
% Send signal over an AWGN channel.
EbNo = 10; % In dB
snr = EbNo + 10*log10(k) - 10*log10(nsamp);
ynoisy = awgn(ytx,snr,'measured');

%%Received Signal
yrx = ynoisy;

%%Scatter Plot
% Create scatter plot of noisy signal and transmitted
% signal on the same axes.
h = scatterplot(yrx(1:nsamp*5e3),nsamp,0,'g.');
hold on;
scatterplot(ytx(1:5e3),1,0,'k*',h);
title('Received Signal');
legend('Received Signal','Signal Constellation');
axis([-5 5 -5 5]); % Set axis ranges.
hold off;

After you have run the code you should have the following variables in your workspace:

whos
  Name            Size             Bytes  Class           Attributes

    EbNo            1x1                  8  double                    
    M               1x1                  8  double                    
    h               1x1                  8  double                    
    hMod            1x1                     modem.qammod              
    k               1x1                  8  double                    
    n               1x1                  8  double                    
    nsamp           1x1                  8  double                    
    snr             1x1                  8  double                    
    x           30000x1             240000  double                    
    xsym         7500x1              60000  double                    
    y            7500x1             120000  double          complex   
    ynoisy       7500x1             120000  double          complex   
    yrx          7500x1             120000  double          complex   
    ytx          7500x1             120000  double          complex

Please compare these values with yours in order to hunt down the issue.

I hope I could help,

Friedrich

[Ali]

Thanks I found my problem,

Is there anyway to calculate group delay?

Answer 2

[Andreas Goser]

The link does not work for me, but when a code from a documentation example does not work, then it is likely that either the data has been altered. You can find out the cause of the issue by looking at the dimensions. What is "nsamp*5e" and is there an element ynoisy(1:nsamp*5e3)? Is that maybe an issue with the index being a DOUBLE?

Answer 3

[Ali]

http://www.mathworks.com/help/toolbox/comm/ug/a1067963807.html Copy and paste above link! I want to show how group delay filter work!