trellis_encoder.m

通信中常用的卷积码信道译码源码程序

function [outputs,alpha_channel,varargout] = ...
    trellis_encoder(Data,Trellis,Lut,TerminateF,varargin);

%------------------------------------------------------------------------------
% Encode binary 1-D data vector with convolution / turbo codes.
%
% Format:
% -------
%
% Convolution codes:
% [outputs,alpha_channel]= trellis_encoder(Data, Trellis, Lut, TerminateF, ...
%                           ['convolution'], [enc_type])
%
% Trellis coded modulation (QPSK only):
% [Data_coded,alpha_channel,ModMap] = ...
%   trellis_encoder(Data,Trellis,Lut,TerminateF, 'tcm', enc_type)
%
% Turbo codes (binary output):
% [outputs,alpha_channel,alpha_rsc,NEncoders] = ...
%  trellis_encoder(Data, Trellis, Lut, TerminateF, ...
%                  'turbo', [PunctureF], [number of RSC's])
% 
% Turbo coded modulation (QPSK output):
% [outputs,alpha_channel,alpha_rsc,NEncoders,alpha_bit,ModMap] = ...
%  trellis_encoder(Data, Trellis, Lut, TerminateF, ...
%                  'turbocm', [PunctureF], [number of RSC's])
% 
% Author: MVe
% Date:   05.07.2002
%------------------------------------------------------------------------------

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% -- Initial parameter checking etc.. -- %% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Check if the function call format is correct and extract
% additional parameter(s) if necessary.
tmp1 = length(varargin);

% If additional arguments are given
if tmp1>0

  switch tmp1
   % Convolution or turbo with no number of RSC's given
   case 1
    encoder_name = varargin{1};
    if or(strcmp(encoder_name, 'turbo'), strcmp(encoder_name, 'turbo'))
      NEncoders = 2;
      PunctureF = 0;
    else
      enc_type = Trellis.EncType;
      %if TerminateF
      %  enc_type = 'recursive';
      %else
      %  enc_type = 'non-recursive';
      %end % if TerminateF
    end % if strcmp(encoder_name,'turbo')
   % Turbo or convolution   
   case 2 
    encoder_name = varargin{1};
    if or(strcmp(encoder_name,'turbo'),strcmp(encoder_name,'turbocm'))
      PunctureF = varargin{2};
    else
      enc_type = varargin{2};
    end % if strcmp(encoder_name,'turbo')
   % Turbo, fully defined
   case 3
    encoder_name = varargin{1};
    PunctureF = varargin{2};
    NEncoders = varargin{3};
   otherwise
    error('Too many parameters');
  end % switch tmp1

else

  % Assume convolution encoder, if additional parameters not given
  encoder_name = 'convolution';
    enc_type = Trellis.EncType;
  
end % if tmp1~=0

% Works currently only for 1-D vectors
tmp = size(Data);
if or(length(tmp) > 2,sum(tmp(:)>1)>1)
  error('Encoder works only with vector inputs');
else
  if tmp(1)>tmp(2)
    reshape_flag = 1;
    Data = Data.';
  else
    reshape_flag = 0;
  end % if tmp(1)>tmp(2)    
end % if or(length(tmp) > 2,sum(tmp(:)>1)>1)


%%%%%%%%%%%%%%%%%%%%
%% -- Encoding -- %%
%%%%%%%%%%%%%%%%%%%%

DLength = size(Data,2);
outputs = zeros(1,DLength*(1/Trellis.Rate));

switch encoder_name
 
 %% -- Convolution codes, one linear or recursive component encoder -- %%
 
 case 'convolution'
  outputs = convolution_enc(Data,Trellis,TerminateF,enc_type);

 case 'tcm'
  [outputs,ModMap] = convolution_enc(Data,Trellis,TerminateF,enc_type,'tcm');

 %% -- Turbo codes, multiple recursive component encoders -- %%
 
 case 'turbo'  
  % -- Create pseudo-random odd-even interleaver(s) between RSC's -- %  
  alpha_rsc = odd_even_interleaver(DLength, TerminateF, NEncoders, Trellis.m);
  
  % --  Encode bits with RSC's (only for rates 1/k, k = 2,3,4) -- %
  %
  % outputs = [inf#1, par#11, ..., par#1NEncoders, inf#2, par#21, ...]
  %
  outputs = turbo_enc(Data,Trellis,alpha_rsc,TerminateF,PunctureF,NEncoders);

 case 'turbocm'  
  % -- Create pseudo-random odd-even interleaver(s) between RSC's -- %  
  alpha_rsc = odd_even_interleaver(DLength, TerminateF, NEncoders, Trellis.m);
  
  % --  Encode bits with RSC's (only for rates 1/k, k = 2,3,4) -- %
  %
  [outputs,alpha_bit,ModMap] = turbo_enc(Data,Trellis,alpha_rsc,TerminateF,...
                                         PunctureF, NEncoders, 'QPSK');

 otherwise
  error(sprintf('Unknown encoder ''%s''',encoder_name));

end % switch encoder_name



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% -- Output variables  -- %%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% If rsc-interleaver has been created, output it
if exist('alpha_rsc','var')
  varargout{1} = alpha_rsc;
end % if exist('alpha_rsc','var')

% Number of encoders
if exist('NEncoders','var')
  varargout{2} = NEncoders;
end % if exist('NEncoders','var')

% If bit-interleaver has been created, output it
if exist('alpha_bit','var')
  varargout{3} = alpha_bit;
end % if exist('alpha_bit','var')

if exist('ModMap','var')
  switch encoder_name
   case 'tcm'
    varargout{1} = ModMap;    
   case 'turbocm'  
    varargout{4} = ModMap;    
  end % switch encoder_name
end % if exist('ModMap','var')

% Interleave for channel
[dummy,alpha_channel] = sort(rand(1,length(outputs)));
%[alpha_channel] = [1:length(outputs)];
outputs = outputs(alpha_channel);

% Reshape the output vector if necessary
if reshape_flag
  outputs = outputs.';
end % if reshape_flag