qam_mod.m

3 MATLAB functions for simulation of OFDM signal in Rayleigh fading channel. Including models for OF

function [sig,sig_length] = QAM_MOD(size,input)

% sig - output symbols
% size - modulation size (4,16,256)
% input - vector of bytes to be modulated

AM2 = [-1 1];
AM4 = [-3 -1 1 3]; AM4 = 2*AM4/sqrt(AM4*AM4');
AM16 = [-15 -13 -11 -9 -7 -5 -3 -1 1 3 5 7 9 11 13 15]; AM16 = 4*AM16/sqrt(AM16*AM16');

sig = zeros(1,length(input)*8/log2(size));
sig_length = length(input)*8/log2(size);

for l=1:length(input)
     if (size == 256)
       sig(l) = (AM16(1+ floor((input(l)/16))) +sqrt(-1)*AM16(1+rem(input(l),16)))/sqrt(2);  

     elseif (size == 16)
       sig(1 + 2*(l-1)) = (AM4(1+floor((input(l)/64))) + sqrt(-1)*AM4(1+rem(floor(input(l)/16) , 4)))/sqrt(2);
       sig(2 + 2*(l-1)) = (AM4(1+rem(floor(input(l)/4) , 4)) + sqrt(-1)*AM4(1+rem(input(l) , 4)))/sqrt(2);
     
     elseif (size == 4)
       sig(1+ 4*(l-1)) = (AM2(1+(floor(input(l)/128))) + sqrt(-1)*AM2(1+rem(floor(input(l)/64) , 2)))/sqrt(2);
       sig(2+ 4*(l-1)) = (AM2(1+rem(floor(input(l)/32) ,2)) + sqrt(-1)*AM2(1+rem(floor(input(l)/16) , 2)))/sqrt(2);
       sig(3+ 4*(l-1)) = (AM2(1+rem(floor(input(l)/8) , 2)) + sqrt(-1)*AM2(1+rem(floor(input(l)/4)  , 2)))/sqrt(2);
       sig(4+ 4*(l-1)) = (AM2(1+rem(floor(input(l)/2) , 2)) + sqrt(-1)*AM2(1+rem(input(l)    , 2)))/sqrt(2);

     end
   end