soft_demap_siso_20_approx.m

A SISO 20M OFDM system based on IEEE802.11n standard, using Matlab.

function dout = soft_demap_siso_20_approx(din, Mode)

switch Mode
    case 1
        CBPS = 104;
    case 2
        CBPS = 104;
    case 3
        CBPS = 208;
    case 4
        CBPS = 208;
    case 6
        CBPS = 312;
    case 7
        CBPS = 312;
end
enzan=0;
%enzan=enzan+1;

re_din = real(din);
im_din = imag(din);

if Mode == 1 || Mode == 2
    % QPSK
    for I=1:52
        dout((I-1)*2+1) = re_din(I);
        dout((I-1)*2+2) = im_din(I);  
    end
elseif Mode == 3 || Mode == 4
    % 16QAM
    for I=1:52
        i_bit_1 = re_din(I);
        i_bit_2 = - abs(re_din(I)) + 0.6325;
        %i_bit_2 = - abs(re_din(I)) + 2/sqrt(10);
        q_bit_1 = im_din(I);
        q_bit_2 = - abs(im_din(I)) + 0.6325;
        %q_bit_2 = - abs(im_din(I)) + 2/sqrt(10);   
        dout((I-1)*4+1) = i_bit_1;
        dout((I-1)*4+2) = i_bit_2;
        dout((I-1)*4+3) = q_bit_1;
        dout((I-1)*4+4) = q_bit_2;  
    end
elseif Mode == 6 || Mode == 7
    % 64QAM
    for I=1:52
        i_bit_1 = re_din(I);
        %i_bit_2 = - abs(re_din(I)) + 4/sqrt(42);
        %i_bit_3 = - abs(abs(re_din(I)) - 4/sqrt(42)) + 2/sqrt(42);
        i_bit_2 = - abs(re_din(I)) + 0.6172;
        i_bit_3 = - abs(abs(re_din(I)) - 0.6172) + 0.3086;  
        
        q_bit_1 = im_din(I);
        %q_bit_2 = - abs(im_din(I)) + 4/sqrt(42);
        %q_bit_3 = - abs(abs(im_din(I)) - 4/sqrt(42)) + 2/sqrt(42);
        q_bit_2 = - abs(im_din(I)) + 0.6172;
        q_bit_3 = - abs(abs(im_din(I)) - 0.6172) + 0.3086;
        
        dout((I-1)*6+1) = i_bit_1;
        dout((I-1)*6+2) = i_bit_2;
        dout((I-1)*6+3) = i_bit_3;
        dout((I-1)*6+4) = q_bit_1;
        dout((I-1)*6+5) = q_bit_2;
        dout((I-1)*6+6) = q_bit_3;  
    end
 end