GENERATING MPSK BER VS SNR

clc;
clear all;
close all;
k=input('enter the no of bits');
M = 2^k; %size
N = k*10^3; % number of symbols
% k = log2(M); % b/symbol

a = [0:M-1]*2*pi/M; % phase values

SNRdB = [3:1:13]; % SNR range

sdB = SNRdB + 10*log10(k);

% Mbinary to Gray code conversion

b = [0:M-1];

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

[tt ind] = sort(map);

c = zeros(1,N);

for i = 1:length(SNRdB)


bits = rand(1,N*k,1)>0.5; % random 1's and 0's

% binary to decikal
bin2DecMatrix = ones(N,1)*(2.^((k-1):-1:0)) ;
shape= reshape(bits,k,N).';

% decimal to binary
G= (sum(shape.*bin2DecMatrix,2)).';

% Gray code mapping
dec = ind(G+1)-1; %
ph= dec*2*pi/M;

% modulation
d= exp(1i*ph);
s = d;

% AWGN

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

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

% demodulation

e = angle(r);

% phase

e(e<0) = e(e<0) + 2*pi;

c = 2*pi/M*round(e/(2*pi/M)) ;

c(c==2*pi) = 0;
cd = round(c*M/(2*pi));

% Decimal to Gray conversion

f = map(cd+1);
cb = dec2bin(f,k) ;

cb = cb.';
cb = cb(1:end).';
cb = str2num(cb).' ;


% errors
Err(i) = size(find(bits- cb),2);


end
sBer=Err/(N*k);
tBer =(1/k)*erfc(sqrt(k*10.^(SNRdB/10))*sin(pi/8));
% plot
figure
semilogy(SNRdB,tBer,'rs-','LineWidth',2);
hold on
semilogy(SNRdB,sBer,'kx-','LineWidth',2);

legend('theory', 'simulation');
xlabel('SNR dB')
ylabel('Bit Error Rate')
title('BER VS SNR M-PSK')