function yrx=qdemodulator(x,M)
%Carlos 26/03/06; AAU; DK
datadec=0;
K=log2(M);                  %number of bits per symbol
switch M                    %cases for each modulation
    case 2
        load qam2;
    case 4
        load qam4;
    case 8
        load qam8;
    case 16
        load qam16;
    case 32
        load qam32;
    case 64
        load qam64;
    case 128
        load qam128;
    case 256
        load qam256;
end
ly=length(yqmod);                                                 %variable yqmod has the constellation selected using case
lx=length(x);                                                     %x contains the bits after the channel(information + noise)
for g=1:lx
    [tmp,index]=min(abs(yqmod-x(g)));                             %evaluating the complex modulus
    symdec=index-1;                                               %decimal value of data
    datadec=[datadec,symdec];
end
nydatadec=datadec(2:length(datadec));                             %the first element doesn't count
yrx=0;
yrx=de2bi(nydatadec,'left-msb',K);                                  %from decimal to binary
yrx=reshape(yrx.',prod(size(yrx)),1)';                            %data recovered