modulate.m

code for signal Processing in OFDM calculation.

function y = modulate(x,b,e, s2,s4,s16,s64,s256)
% function y = modulate(x,b,e, s2,s4,s16,s64,s256)
%
%    y - modulated output, in the form of a row vector
%    x - a vector of input bits, for all the subcarriers (row vector)
%    b - subcarrier bit allocation (64 elements in this matrix, each one
%        corresponding to the number of bits to be allocated to the subcarrier
%        having the same index)
%    e - subcarrier energy allocation (64 elements in this matrix, each one
%        corresponding to the energy to be allocated to the subcarrier
%        having the same index)
%    s_ - the encoder for a given constellation size

y=[];

b2 = zeros(1,length(b));
b2(1) = 1;
for i = 1:length(b)
    b2(i+1) = b(i) + b2(i);
end

for i = 1:length(b)
    switch b(i)
    case {1}
        y = [y s2(x(b2(i))+1)*sqrt(e(i))];
    case {2}
        y = [y s4(x(b2(i):(b2(i+1)-1))*[2;1]+1)*sqrt(e(i))];
    case {4}
        y = [y s16(x(b2(i):(b2(i+1)-1))*[8;4;2;1]+1)*sqrt(e(i))];
    case {6}
        y = [y s64(x(b2(i):(b2(i+1)-1))*[32;16;8;4;2;1]+1)*sqrt(e(i))];
    case {8}
        y = [y s256(x(b2(i):(b2(i+1)-1))*[128;64;32;16;8;4;2;1]+1)*sqrt(e(i))];
    otherwise
        % must be zero bits allocated
        y = [y 0];
    end
end