st_trellis_dec_c.m

通信中常用的卷积码信道译码源码程序

function outputs = ...
   st_trellis_dec_C(Data_received,ST_NextState,ST_Output,Lut_InfBits, ...
                    ModMap, alpha_channel,fading_gains_i,TerminateF,SF,NRx);

%------------------------------------------------------------------------------
% Decode received space-time trellis coded data matrix.
%
% Format:
% -------
%
% outputs = ...
%
%   st_trellis_dec_C(Data_received,ST_NextState,ST_Output,Lut_InfBits, ...
%                    ModMap, alpha_channel,fading_gains_i,TerminateF,SF,NRx);
% 
% Author: MVe
% Date:   27.08.2002
%------------------------------------------------------------------------------

%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% -- Initialisations -- %%
%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Length of the received symbol/data vector
LData = length(Data_received);

% Extract most used variables from struct 'Trellis'
% n = size(ST_Output{1,1},2);                % # of outputs/antenna
k_bits = log2(size(ST_NextState,2));       % # input bits to encoder
m_bits = log2(size(ST_NextState,1));       % encoder memory (in bits)
m = ceil(m_bits/k_bits);                   % encoder memory (in "symbols")
number_of_states = size(ST_NextState,1);
NTx = size(ST_Output{1,1},1);              % number of transmit antennas

% Separate trellis outputs for different tx-antennas
k_bits = log2(size(ST_NextState,2));       % # input bits to encoder
tmp = [ST_Output{:}];
Output_mod_1 = ModMap(reshape(tmp(1,:),number_of_states,2^k_bits));
Output_mod_2 = ModMap(reshape(tmp(2,:),number_of_states,2^k_bits));

%% -- fading_gains_i = ('tx_antenna','time','rx_antenna') -- %%
%
% De-interleave data and fading (same interleaving assumed for all channels)
if SF>1

  temp_SF = zeros(SF,LData/SF);
  temp_SF_i = zeros(SF,LData/SF);

  %% -- Fading gains -- %%
  for i1=1:NRx
    for i2 = 1:NTx
      temp_SF_i=reshape(fading_gains_i(i2,:,i1),SF,LData/SF);
      for i3=1:SF
        temp_SF(i3,alpha_channel)=temp_SF_i(i3,:);
      end % for i3=1:SF
      fading_gains_i(i2,:,i1)=reshape(temp_SF,1,LData);  
    end % for i2 = 1:NTx      
  end % for i1=1:NRx
  
  %% -- Data -- %%
  for i1=1:NRx
    temp_SF_i=reshape(Data_received(i1,:),SF,LData/SF);
    for i2=1:SF
      temp_SF(i2,alpha_channel)=temp_SF_i(i2,:);
    end % for i2=1:SF
    Data_received(i1,:)=reshape(temp_SF,1,LData);  
  end % for i1=1:2*NRx  
  
else
  
  Data_received(:,alpha_channel) = Data_received;
  fading_gains_i(:,alpha_channel,:) = fading_gains_i;
  
end % if SF>1

fading_gains = zeros(NTx*NRx,LData);
for i1 = 1:NRx
  fading_gains((i1-1)*NTx+1:i1*NTx,:) = fading_gains_i(:,:,i1);
end % for i1 = 1:NRx  

final_state_path = st_dec_CC(Data_received, ST_NextState, Output_mod_1,...
            			     Output_mod_2, fading_gains, k_bits*m, SF);


% Convert state path to info bit sequence
out_tmp = cell(1,length(final_state_path)-1);
for i1 = 1:length(out_tmp)
  out_tmp(i1) = ...
      Lut_InfBits(final_state_path(i1),final_state_path(i1+1));
end % for i1 = 1:2:length(Data_received)

outputs = [out_tmp{:}];


% Remove tail bits
if TerminateF
  outputs = outputs(1:end-k_bits*(ceil(log2(number_of_states)/k_bits)));
end % if TerminateF