MATLAB: Error using .* .Matrix dimensions must agree

awgnbpskcrcerrorMATLABrayleigh

Hi, I been simulating the data transmission in Rayleigh and AWGN channel. I want to include CRC in the simulation. My code is as follows:
    clear
    NoBits =4; % number of bits
    noPacket=4;
    %-------------------------At the transmitter-------------------------------
    DataIn =randi([0,1],noPacket,NoBits); % generating 0,1 with equal probability
    %~~~~~~~~~~Cyclic Redundancy Check (CRC)~~~~~~~~~~
                div=[1 0 0 1];        % predetermined divisor
                for i=1:noPacket
                    [q,r]=deconv(DataIn(i,:),div); 
                   y(i,:)=[DataIn(i,:),zeros(1,3)];
                   for k=1:NoBits
                           r(k)=mod(r(k),2);
                   end
                   fcs=[zeros(1,3),r];        % frame check sequence  
                   DataOut(i,:)=bitxor(y(i,:),fcs);
                end
    %~~~~~~~~~~BPSK Modulation~~~~~~~~~~   
    BPSK1 = 2*DataOut-1; % BPSK modulation 0 -> -1; 1 -> 0 
    Eb_N0_dB = [-3:35]; % multiple Eb/N0 values
    %-------------------------Channel Modelling-------------------------------
    for ii = 1:length(Eb_N0_dB)
       awgn = 1/sqrt(2)*[randn(1,NoBits) + j*randn(1,NoBits)]; % white gaussian noise, 0dB variance 
       Ray = 1/sqrt(2)*[randn(1,NoBits) + j*randn(1,NoBits)]; % Rayleigh channel
     % Channel and noise Noise addition
     y = Ray.*BPSK1 + 10^(-Eb_N0_dB(ii)/20)*awgn; 
    %----------------------------At the Receiver-------------------------------
          % equalization
           yHat = y./Ray;
        % receiver - hard decision decoding
       recDat = real(yHat)>0;
       % counting the errors
       nErr(ii) = size(find([DataIn-recDat]),2);
    end
    simBer = nErr/NoBits; % simulated ber
    theoryBerAWGN = 0.5*erfc(sqrt(10.^(Eb_N0_dB/10))); % theoretical ber
    EbN0Lin = 10.^(Eb_N0_dB/10);
    theoryBer = 0.5.*(1-sqrt(EbN0Lin./(EbN0Lin+1)));
    % plot
    close all
    figure
    semilogy(Eb_N0_dB,theoryBerAWGN,'cd-','LineWidth',2);
    hold on
    semilogy(Eb_N0_dB,theoryBer,'bp-','LineWidth',2);
    semilogy(Eb_N0_dB,simBer,'mx-','LineWidth',2);
    axis([-3 35 10^-5 0.5])
    grid on
    legend('AWGN-Theory','Rayleigh-Theory', 'Rayleigh-Simulation');
    xlabel('Eb/No, dB');
    ylabel('Bit Error Rate');
    title('BER for BPSK modulation in Rayleigh channel');
However, i encounter "Error using .* .Matrix dimensions must agree" on line :
    y = Ray.*BPSK1 + 10^(-Eb_N0_dB(ii)/20)*awgn;
I know the error must have the problem regarding mismatching of matrix dimension. I have tried repmat and other but, i wonder if there is any other solution that can make the BER become more accurate and reliable? Any help would be appreciated. Thank You.

Best Answer

In line
% Channel and noise Noise addition

y = Ray.*BPSK1 + 10^(-Eb_N0_dB(ii)/20)*awgn;
The
Ray.*BPSK1
only works if instead you start the line with
y=BPSK1'*Ray'+ ..
 -0.478487048890906 + 3.821695518247046i
  1.171402651187593 - 0.797604495033111i
  1.249572268765731 - 1.118081175144724i
 -0.896870514142436 - 0.718652054769934i
  1.171402651187593 - 0.797604495033111i
  1.249572268765731 - 1.118081175144724i
 -1.524104405810888 + 2.634337724947769i
yet
BPSK1'*Ray' does not match the second attempt to add noise
10^(-Eb_N0_dB(ii)/20)*awgn;
what do you mean by
     % Channel and noise Noise addition
I keep hearing and reading about MATLAB communications applications being developed mainly in SIMULINK.
Can you build the SIMULINK equivalent of the script in the question, i dare say it will simplify it all, quite
Regards
John
jgb2012@sky.com
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