mappingrx.m

802.16 physical layer simulation through diferent SUI Channel.

function data_mapping = mappingRX( data_interleaving, n_mod_type)



% Now depending on the modulation, a constellation is defined.
% These constellations are defined in the standard.
    
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
switch n_mod_type
    case 1                          % for BPSK
        type_map = 'MPSK';          
        M = 2;
        M1 = 0;
        M2 = 0;
        c = 1;
    case 2                          % for QPSK(or 4-QAM)
        type_map = 'QAM';
        c = 1/sqrt(2);
    case 4                          % for 16-QAM
        type_map = 'QAM';
        c = 1/sqrt(10);
    case 6                          % for 64-QAM
        type_map = 'QAM';
        c = 1/sqrt(42);
end

if n_mod_type~=1
    M = 0;
    M1 = sqrt(2^n_mod_type);
    M2 = sqrt(2^n_mod_type);
end
type_mapping=type_map;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Block of initialization
%
if strcmp(type_mapping,'QAM')
    k1 = ceil(log2(M1));
    k2 = ceil(log2(M2));
    M1 = 2^k1;
    M2 = 2^k2;
    M = M1*M2;
    
    % Everything is initialized
     % Aicd will be the values different from the coefficients in phase and
     % Aisd the values different from the coefficients in quadrature
    Aicd = zeros(1,k1);            
    Aisd = zeros(1,k2);             
    table1 = zeros(M1,2);
    table2 = zeros(M2,2);
    alphabet = zeros(M,3);

    % In 'table1' and 'table2', every row contains the decimal value of
    % the bits [b1 b2... Bk1] and the indices of the table Aicd and Aisd that encode them
    
    d1 = 0:1:M1-1;
    d1 = d1';
    d2 = 0:1:M2-1;
    d2 = d2';
	ind1 = bi2de(fliplr(gray2bin(fliplr(de2bi(d1)),'QAM',4)));
	table1 = [d1,ind1+1];                  
	ind2 = bi2de(fliplr(gray2bin(fliplr(de2bi(d2)),'QAM',4)));
	table2 = [d2,ind2+1];                  
    
else
    
	k = ceil(log2(M));
	M = 2^k;

    % We initialize
	Aicd = zeros(1,k);           % The values different from the coefficients in phase
	Aisd = zeros(1,k);           % The values different from the coefficients in quadrature
	table = zeros(M,2);          % A table with indices
	alphabet = zeros(M,3);       % Alphabet
	
    % In this case, every row of the table 'table' contains the decimal
    % value of the bits [b1 b2 ... bk] and the index of the table Aicd and Aisd that encodes it
	d = 0:1:M-1;
	d = d';
    ind=bi2de(fliplr(gray2bin(fliplr(de2bi(d)),'QAM',4)));
	table = [d,ind+1];
    
end

% Block of computation
%
if strcmp(type_mapping,'PAM')
    Aicd = -(M-1):2:M-1;                   
    Aisd = [];
    
    % We create alphabet
    for i=1:M
        index = find_index(i-1,table);
        alphabet(i,:) = [i-1,Aicd(index),0];
    end
    
elseif strcmp(type_mapping,'MPSK')
    angle = 0:2*pi/M:2*pi*(M-1)/M;
    Aicd = cos(angle);
    Aisd = sin(angle);
    
    % We create alphabet
    for i=1:M
        index = find_index(i-1,table);
        alphabet(i,:) = [i-1,Aicd(index),Aisd(index)];
    end

    
elseif strcmp(type_mapping,'QAM')
    Aicd = -(M1-1):2:M1-1;       
    Aisd = (M2-1):-2:-(M2-1);
    
    % We create alphabet
    for i=1:M1
        for j=1:M2
            index1 = find_index(i-1,table1);           
            index2 = find_index(j-1,table2);
            l = i+M1*(j-1);
            alphabet(l,:) = [l-1,Aicd(index1),Aisd(index2)];
        end
    end
    
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if n_mod_type~=1
    constellation_gray = alphabet(:,3) + j*alphabet(:,2);
else
    constellation_gray = [0 1]';
end

l = length(data_interleaving);
% So that all the values are coherent, I must begin to divide the
% initial vector by the factor 'c' defined in the norm.
data_normalized = data_interleaving ./ c;
% Now the inverse of the mapping must be realized.
for i=1:l
    v_data_mapping = data_normalized (i);
    % I decode them and it transforms them of dn=an j*bn to binary
    % numbers, according to my Gray constellation.
    v_decode = genqamdemod(v_data_mapping,constellation_gray);
    % I place them in the matrix where I am going to have all the symbols by columns
    data_decimal(:,i) = v_decode;
    data_mapping = de2bi(data_decimal,n_mod_type,'left-msb')';
    data_mapping = data_mapping(:)';
end