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GENERAL CODE OF MQAM TO GENERATE BER VS SNR PLOT

version 1.0.0.0 (2.26 KB) by raghav khandelwal
GENERAL CODE OF MQAM TO GENERATE BER VS SNR PLOT

341 Downloads

Updated 14 May 2015

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clc;
clear all;
close all;
N = 4*10^3; % number of symbols
M = 16; % 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+4)/2+1))-1;
oIm = ind(floor((n+4)/2+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(str2num(pRe).',k/2,N).' ;

pIm = pIm.';
pIm = pIm(1:end).';
pIm = reshape(str2num(pIm).',k/2,N).' ;

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

end
sBer = Err/(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')

Cite As

raghav khandelwal (2021). GENERAL CODE OF MQAM TO GENERATE BER VS SNR PLOT (https://www.mathworks.com/matlabcentral/fileexchange/50850-general-code-of-mqam-to-generate-ber-vs-snr-plot), MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R2009b
Compatible with any release
Platform Compatibility
Windows macOS Linux

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