# Please help me this code which 64 QAM MATLAB CODE.

1. ## Please help me this code which 64 QAM MATLAB CODE.

Dear all;

Please look at this MATLAB code and help me to find error.

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N = 20*10^3; % number of symbols
M = 64; % size
k = log2(M); % bits/symbol

% for 16-QAM
Re = [-(2*sqrt(M)/2-1):2:-1 1:2:2*sqrt(M)/2-1];

Im = [-(2*sqrt(M)/2-1):2:-1 1:2:2*sqrt(M)/2-1];

k_QAM = 1/sqrt(10);

bdB = 3:1:13; % SNR range

sdB = bdB + 10*log10(k);

% binary to gray code

a = (0:k-1);

map = bitxor(a,floor(a/2));

[tt, ind] = sort(map);

for i = 1:length(bdB)
c = rand(1,N*k,1)>0.5; % random 1's and 0's
d = reshape(c,k,N).';
bd = ones(N,1)*(2.^((k/2-1):-1:0)) ; % conversion from binary to decimal

% real

cRe = d(:,(1:k/2));
e = sum(cRe.*bd,2);
f = bitxor(e,floor(e/2));

% imaginary
cIm = d(:,(k/2+1:k));
g = sum(cIm.*bd,2);
h = bitxor(g,floor(g/2));

% mapping the Gray coded symbols into constellation
modRe = Re(f+1);
modIm = Im(h+1);

% constellation

mod = modRe + 1i*modIm;
s = k_QAM*mod;

% noise

n = 1/sqrt(2)*(randn(1,N) + 1i*randn(1,N));

% reciever
r = s + 10^(-sdB(i)/20)*n;

% demodulation

r_re = real(r)/k_QAM;
r_im = imag(r)/k_QAM;

% rounding off

m = 2*floor(r_re/2)+1;
m(m>max(Re)) = max(Re);
m(m<min(Re)) = min(Re);

n= 2*floor(r_im/2)+1;
n(n>max(Im)) = max(Im);
n(n<min(Im)) = min(Im);

% To Decimal conversion

oRe = ind(floor((m+8)/4+1))-1;
oIm = ind(floor((n+8)/4+1))-1;

% To binary string
pRe = dec2bin(oRe,k/2);
pIm = dec2bin(oIm,k/2);

% binary string to number
pRe = pRe.';
pRe = pRe(1:end).';
pRe = reshape(str8num(pRe).',k/4,N).' ;

pIm = pIm.';
pIm = pIm(1:end).';
pIm = reshape(str8num(pIm).',k/8,N).' ;

% counting errors for real and imaginary
Err(r) = size(find((cRe - pRe)),1) + size(find((cIm - pIm)),1) ;

end
sBer = Error/(N*k);
tBer = (1/k)*3/2*erfc(sqrt(k*0.05*(10.^(bdB/10))));

% plot
figure
semilogy(bdB,tBer,'rs-','LineWidth',2);
hold on
semilogy(bdB,sBer,'kx-','LineWidth',2);
grid on
legend('theory', 'simulation');
xlabel('SNR dB')
ylabel('Bit Error Rate')
title('BER VS SNR')```

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2. ## Re: Please help me this code which 64 QAM MATLAB CODE.

The error is that you posted an arcane block of code with no explanation of what it’s supposed to do, what your problem is, or ANYTHING useful, and then you expect us to “find the error”.

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