www.pudn.com > space-timecodingBrankaVuceticJinhongYuan.rar > tx_modulate.m, change:2004-02-16,size:2661b

 
function [mod_symbols,table, P] = tx_modulate(bits_in, modulation) 
 
%************************************************************************** 
%This program modulates the input binary data.The inputs are: 
% bits_in -> the binary input bits 
%modulation -> we choose one of 'BPSK','QPSK',8PSK',16QAM' 
%The outputs are: 
%mod_symbols -> modulated output 
%table -> the complete set of symbols in a chosen constellation. This is 
%required by the demodulator. 
%P -> the number of points in a chosen constellation. This is required by 
%the demodulator 
%************************************************************************** 
 
full_len = length(bits_in); 
 
% BPSK modulation 
if ~isempty(findstr(modulation, 'BPSK')) 
   % Angle [pi/4 -3*pi/4] corresponds to  
   % Gray code vector [0 1], respectively. 
   table=exp(j*[0 -pi]);  % generates BPSK symbols 
   table=table([1 0]+1); % Gray code mapping pattern for BPSK symbols 
   inp=bits_in; 
   mod_symbols=table(inp+1);  % maps transmitted bits into BPSK symbols 
   P=2;% 2 constellation points 
   % QPSK modulation 
elseif ~isempty(findstr(modulation, 'QPSK')) 
   % Angle [pi/4 3*pi/4 -3*pi/4 -pi/4] corresponds to  
   % Gray code vector [00 10 11 01], respectively. 
   table=exp(j*[-3/4*pi 3/4*pi 1/4*pi -1/4*pi]);  % generates QPSK symbols 
   table=table([0 1 3 2]+1); % Gray code mapping pattern for QPSK symbols 
   inp=reshape(bits_in,2,full_len/2); 
   mod_symbols=table([2 1]*inp+1);  % maps transmitted bits into QPSK symbols 
   P=4;% 4 constellation points 
elseif  ~isempty(findstr(modulation, '8PSK')) 
    % generate constellations 
       % Angle [0 pi/4 pi/2 3*pi/4 pi 5*pi/4 3*pi/2 7*pi/4] corresponds to  
   % Gray code vector [000 001 011 010 110 111 101 100], respectively. 
   table=exp(j*[0 pi/4 pi/2 3*pi/4 pi 5*pi/4 3*pi/2 7*pi/4]);  % generates 8PSK symbols 
   table=table([0 1 3 2 6 7 5 4]+1); % Gray code mapping pattern for 8PSK symbols 
   inp=reshape(bits_in,3,full_len/3); 
   mod_symbols=table([4 2 1]*inp+1);  % maps transmitted bits into 8PSK symbols 
   P=8;%8 constellation points 
   % 16-QAM modulation 
elseif ~isempty(findstr(modulation, '16QAM')) 
   % generates 16QAM symbols 
      m=1; 
   for k=-3:2:3 
      for l=-3:2:3 
         table(m) = (k+j*l)/sqrt(10); % power normalization 
         m=m+1; 
      end; 
   end; 
   table=table([0 1 3 2 4 5 7 6 12 13 15 14 8 9 11 10]+1); % Gray code mapping pattern for 8-PSK symbols 
   inp=reshape(bits_in,4,full_len/4); 
   mod_symbols=table([8 4 2 1]*inp+1);  % maps transmitted bits into 16QAM symbols 
   P=16; %16 constellation points 
 
else 
   error('Unimplemented modulation'); 
end