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function [detected_data, errors] = CmlDecode( symbol_likelihood, data, sim_param, code_param )
% CmlDecode demaps and decodes a single received codeword
%
% The calling syntax is:
% [detected_data, errors] = CmlDecode( symbol_likelihood, data, max_iterations, sim_param, code_param )
%
% Outputs:
% detected_data = a row vector containing the detected data
% errors = a column vector containing the number of errors per iteration
%
% Required inputs:
% symbol_likelihood = a M-row matrix containing the symbol log-likelihoods
% data = the row vector of data bits (used to count errors and for early halting of iterative decoding)
% sim_param = A structure containing simulation parameters.
% code_param = A structure containing the code paramaters.
%
% Copyright (C) 2005-2008, Matthew C. Valenti
%
% Last updated on May 22, 2008
%
% Function CmlDecode is part of the Iterative Solutions Coded Modulation
% Library (ISCML).
%
% The Iterative Solutions Coded Modulation Library is free software;
% you can redistribute it and/or modify it under the terms of
% the GNU Lesser General Public License as published by the
% Free Software Foundation; either version 2.1 of the License,
% or (at your option) any later version.
%
% This library is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
% Lesser General Public License for more details.
%
% You should have received a copy of the GNU Lesser General Public
% License along with this library; if not, write to the Free Software
% Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
if (code_param.coded)
% default values
bicm_iterations = 1;
turbo_iterations = 1;
% initialize some parameters
[M,L] = size(symbol_likelihood);
switch sim_param.code_configuration
case {0} % convolutional
[N1,K1] = size( sim_param.g1 );
input_decoder_u = zeros(1, code_param.data_bits_per_frame ); % stays at zero
if ( length(code_param.max_iterations) )
bicm_iterations = code_param.max_iterations;
end
case {1,4} % PCCC
[N1,K1] = size( sim_param.g1 );
if ( sim_param.bicm == 2 ) % bicm-id
bicm_iterations = code_param.max_iterations;
else
turbo_iterations = code_param.max_iterations;
end
[N2,K2] = size( sim_param.g2 );
input_decoder_u = zeros(1, code_param.data_bits_per_frame );
case {3} % HSDPA
% BICM-ID not supported
bicm_iteration = 1;
turbo_iterations = code_param.max_iterations;
% Number of H-ARQ transmissions
M_arq = length(sim_param.X_set);
end
% initialize errors vector
errors = zeros(turbo_iterations*bicm_iterations,1);
% initialize the extrinsic decoder input
input_somap_c = zeros(1, code_param.code_bits_per_frame );
for bicm_iter=1:bicm_iterations
% demodulate
if (code_param.bpsk)
input_decoder_c = symbol_likelihood;
else
bit_likelihood = Somap( symbol_likelihood, sim_param.demod_type, input_somap_c );
input_decoder_c = bit_likelihood(1:code_param.code_bits_per_frame);
end
% deinterleave (BICM)
if sim_param.bicm
input_decoder_c = Deinterleave( input_decoder_c, code_param.bicm_interleaver);
end
% decode
switch sim_param.code_configuration
case {0} % convolutional
% depuncture if necessary
if ( length (sim_param.pun_pattern1 ) )
depunctured_output = Depuncture( input_decoder_c, sim_param.pun_pattern1, sim_param.tail_pattern1 );
input_c = reshape( depunctured_output, 1, prod( size( depunctured_output ) ) );
else
input_c = input_decoder_c;
end
% decode
if ( sim_param.decoder_type < 0 )
% fprintf( 'Viterbi decoding\n' );
detected_data = ViterbiDecode( input_c, sim_param.g1, sim_param.nsc_flag1, sim_param.depth );
else
[output_decoder_u, output_decoder_c] = SisoDecode( input_decoder_u, input_c, sim_param.g1, sim_param.nsc_flag1, sim_param.decoder_type );
detected_data = (sign(output_decoder_u)+1)/2;
end
% count errors
error_positions = xor( detected_data, data );
errors(bicm_iter) = sum( error_positions );
% exit if all the errors are corrected or if a Viterbi decoder
if (errors(bicm_iter)==0)||( sim_param.decoder_type < 0 )
return;
end
% repuncture if necessary
if ( length (sim_param.pun_pattern1 )&&(sim_param.bicm > 0) )
output_decoder_c = reshape( output_decoder_c, N1, length(output_decoder_c)/N1 );
output_decoder_c = Puncture( output_decoder_c, sim_param.pun_pattern1, sim_param.tail_pattern1 );
end
case {1,4} % PCCC
[detected_data, turbo_errors, output_decoder_c, output_decoder_u ] = TurboDecode( input_decoder_c, data, turbo_iterations, sim_param.decoder_type, code_param.code_interleaver, code_param.pun_pattern, code_param.tail_pattern, sim_param.g1, sim_param.nsc_flag1, sim_param.g2, sim_param.nsc_flag2, input_decoder_u );
errors( (bicm_iter-1)*turbo_iterations+1:bicm_iter*turbo_iterations ) = turbo_errors;
% exit if all the errors are corrected
if (turbo_errors(turbo_iterations)==0)
return;
else
% determine new input_decoder_u
input_decoder_u = output_decoder_u;
end
case {2} % LDPC
[x_hat errors] = MpDecode( -input_decoder_c, code_param.H_rows, code_param.H_cols, code_param.max_iterations, sim_param.decoder_type, 1, 1, data );
detected_data = x_hat(code_param.max_iterations,:);
return; % BICM-ID is not supported for LDPC codes.
case {3} % HSDPA
% Dematch each H-ARQ transmission
LLR_buffer = zeros(code_param.number_codewords,code_param.N_TTI);
harq_input = reshape( input_decoder_c, code_param.number_codewords*code_param.N_data, M_arq )';
for harq_transmission=1:M_arq
[LLR] = HarqDematch( reshape( harq_input(harq_transmission,:), code_param.U, code_param.number_codewords*sim_param.P)', sim_param.X_set(harq_transmission), sim_param.N_IR, code_param.N_TTI, code_param.number_codewords );
% update the virtual buffer
LLR_buffer = LLR_buffer + LLR;
end
% Decode
[detected_data, errors, output_decoder_c ] = TurboDecode( LLR_buffer, data, turbo_iterations, sim_param.decoder_type, code_param.code_interleaver, code_param.pun_pattern, code_param.tail_pattern, sim_param.g1, sim_param.nsc_flag1, sim_param.g2, sim_param.nsc_flag2 );
% BICM-ID not currently supported, so return
return;
case {5,6} % CTC code from WiMAX (5) or DVB-RCS (6)
[x_hat errors] = TurboDuobinaryCRSCDecode( input_decoder_c, code_param.code_interleaver, code_param.pun_pattern, data, code_param.max_iterations, sim_param.decoder_type);
detected_data = x_hat;
return; % BICM-ID is not supported for Wimax CTC code.
case {7} % BTC
[detected_data, errors] = BtcDecode( input_decoder_c, data, sim_param.g1, sim_param.g2, sim_param.k_per_row, sim_param.k_per_column, sim_param.B, sim_param.Q, code_param.max_iterations, sim_param.decoder_type );
return; % BICM-ID is not supported
end
% turn LLR into extrinsic info
input_somap_c = output_decoder_c - input_decoder_c;
% deinterleave
if sim_param.bicm
input_somap_c = Interleave( input_somap_c, code_param.bicm_interleaver );
end
end
else
% Convert to bit_likelihood
if (code_param.bpsk) % BPSK
bit_likelihood = symbol_likelihood; % This is the LLR
else
bit_likelihood = Somap( symbol_likelihood, sim_param.demod_type );
end
detected_data = (sign(bit_likelihood)+1)/2; % hard decision
% count errors
error_positions = xor( detected_data(1:code_param.data_bits_per_frame), data );
errors = sum( error_positions );
end
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