Index exceed matrix dimension!!

In the temp variable is having a index exceed matrix dimension, is there any solution?

close all; clear; clc;

semi_fig = figure();
semi_ax = axes('Parent', semi_fig);
hold(semi_ax, 'on')

for M = 2:4      % bit resolutions
    Lavg=2^M;    % average symbol length
    nsym=500;    % number of PPM symbols
    Lsig=nsym*Lavg;    % length of PPM slots
    Rb=1e6;      % bit rate
    Ts=M/(Lavg*Rb);    % slot duration
    Tb=1/Rb;    % bit duration

      Dt =0.4;
      Drms=Dt*Tb;        % RMS delay spread
      a=12*sqrt(11/13)*Drms;
      nsamp=10;               % samples per symbols
      Tsamp=Tb/nsamp;    % sampling time
      K=30*nsamp;        % number of channel taps
      k=0:K;
      h=((6*a^6)./(((k*Tsamp)+a).^7));  % channel impulse response
      h=h./sum(h);
      Tx_filter = ones(1,nsamp);
      Rx_filter = fliplr(Tx_filter);
      c = conv(Tx_filter,h);
      c = conv(c,Rx_filter);
      delay = find (c==max(c));
      if delay > nsamp;
          hi(1) = c(delay-nsamp);
      else hi(1) = 0;
      end
      hi = [hi(1) c(delay:nsamp:end)];
      hi = hi/sum(hi);

      EbN0=0:12;    % energy per slot
      EsN0=EbN0+10*log10(M);  % energy per symbol
      SNR=10.^(EbN0./10);

      for ii=1:length(EbN0)
          PPM=generate_PPM(M,nsym);
          Rx_signal = conv(PPM,hi);
          Rx_signal = Rx_signal(2:nsym+1);
          MF_out=awgn(Rx_signal,EsN0(ii)+3,'measured');

          % hard decision decoding
          Rx_PPM_th=zeros(1,Lsig);
          Rx_PPM_th(find(MF_out>0.5))=1;
          [No_of_Error(ii) ser_hdd(ii)]=biterr(Rx_PPM_th, PPM);

          % soft decision decoding
          PPM_SDD=[];
          start=1;
          finish=2^M;
          for k=1:nsym
              temp=MF_out(start:finish);
              m=max(temp);
              temp1=zeros(1,2^M);
              temp1(find(temp==m))=1;
              PPM_SDD=[PPM_SDD temp1];
              start=finish+1;
              finish=finish+2^M;
          end
          [No_of_Error(ii) ser_sdd(ii)]=biterr(PPM_SDD,PPM);
      end

      Tx_signal=rectpulse(PPM,nsamp);    % Pulse shaping function (rectangular pulse)
      channel_output=conv(Tx_signal,h);  % channel output
      eyediagram(channel_output, 3*nsamp);
      axis([-0.5 0.5 0 1]);

      % theoretical calculation
      Pse_ppm_hard=qfunc(sqrt(M*2^M*0.5*SNR));
      Pse_ppm_soft=qfunc(sqrt(M*2^M*SNR));

      if(M==2)
          semilogy(semi_ax, EbN0,(1/log2(M))*Pse_ppm_hard,'k-','linewidth',2);
          semilogy(semi_ax, EbN0,(1/log2(M))*Pse_ppm_soft,'r-','linewidth',2);
      elseif (M==3)
          semilogy(semi_ax, EbN0,(1/log2(M))*Pse_ppm_hard,'k-X','linewidth',2);
          semilogy(semi_ax, EbN0,(1/log2(M))*Pse_ppm_soft,'r-X','linewidth',2);
      else
          semilogy(semi_ax, EbN0,(1/log2(M))*Pse_ppm_hard,'k--','linewidth',2);
          semilogy(semi_ax, EbN0,(1/log2(M))*Pse_ppm_soft,'r--','linewidth',2);
      end

      grid(semi_ax, 'on')

end
legend(semi_ax, 'M=2 (HDD)','M=2 (SDD)','M=3 (HDD)','M=3 (SDD)','M=4 (HDD)','M=4 (SDD)');
xlabel(semi_ax, 'Eb/N0, dB');
ylabel(semi_ax, 'Bit Error Rate');
title(semi_ax, 'Bit error probability curve for PPM modulation');

hold(semi_ax, 'off')

The generate_PPM code is

function PPM=generate_PPM(M,nsym)
% function to generate PPM
% 'M' bit resolution
% 'nsym': number of PPM symbol

PPM=[];
  for i= 1:nsym
    temp=randint(1,M);      % random binary number
    dec_value=bi2de(temp,'left-msb');  % converting to decimal value
    temp2=zeros(1,2^M);      % zero sequence of length 2^M
    temp2(dec_value+1)=1;      % placing a pulse according to decimal value
              % note that in matlab index does not start from zero, so need to add 1;
    PPM=[PPM temp2];      % PPM symbol
  end
end

Answer 1

[Geoff Hayes]

Alex - is the error occurring in this block of code?

for k=1:nsym
    temp=MF_out(start:finish);
    m=max(temp);
    temp1=zeros(1,2^M);
    temp1(find(temp==m))=1;
    PPM_SDD=[PPM_SDD temp1];
    start=finish+1;
    finish=finish+2^M;
end

If so, the problem could be because the indices in the interval start:finish exceed the dimensions of MF_out and so you will need a check before you access the elements in this array. Perhaps something like

for k=1:nsym
    temp=MF_out(start:finish);
    m=max(temp);
    temp1=zeros(1,2^M);
    temp1(find(temp==m))=1;
    PPM_SDD=[PPM_SDD temp1];
    start=finish+1;
    finish=finish+2^M;
    if finish > length(MF_out)
       break;
    end
end