transmit.m

OFDM系统

function [BitData TransData] = Transmit(  )

global FLAG_AWGN;
global FLAG_MULTIPATH;
global Channel_Est;
global Num_Bit;
global Num_Train;

% generate bits 
 BitData = [floor(2 * rand(1 , Num_Bit-8)), zeros(1,8)];    % for viterbi decoding

% channel coding
t = poly2trellis(7, [131, 171]);
Out = zeros(1, 2*Num_Bit);
Out = convenc(BitData, t);

% interleaving
InterOut = zeros(1, 2*Num_Bit);
for i=1: (2*Num_Bit/256)    
    InterIn = Out(1+(i-1)*256 : i*256);
    
    for k=1:256       
        j = 16*mod((k-1), 16) + floor((k-1)/16);            %分组交织
        Inter1Out(k) = InterIn(j+1);      
    end
    
    for k=1:256       
        j = 2*floor((k-1)/2) + mod((k+1+floor((k-1)/16)), 2);         % 高低位交织
        InterOut(k+(i-1)*256) = Inter1Out(j+1);   
    end
end

% map
MappedData = BitMap(InterOut , 4);

% generate the OFDM signal
Num_Sym_OFDM = 2*Num_Bit/4/64;
TransData = zeros(1, 2*Num_Bit*5/16 );        

for i=1:Num_Sym_OFDM
    
    Sym_OFDM_temp = MappedData( 1+(i-1)*64 : i*64 );
    Sym_OFDM_ifft = 8 * ifft( Sym_OFDM_temp , 64 );         % power normalization
    
    % add CP    
    Sym_OFDM_CP   = Sym_OFDM_ifft( 49 : end );
    Sym_OFDM_ifft = [ Sym_OFDM_CP, Sym_OFDM_ifft ];     
    TransData(1+(i-1)*80 : i*80) = Sym_OFDM_ifft;

end

Train = [zeros(1,16), 1 , zeros(1, 63)];
TransData = [zeros(1, 16), Train, TransData];                % add zeros before the trainning sequences, for synchronization.