Error using .* .Matrix dimensions must agree

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psychecrew
psychecrew 2016-4-26
编辑： John BG 2016-4-26
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.

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采纳的回答

John BG
John BG 2016-4-26
编辑：John BG 2016-4-26
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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