cmldecode.m

1、HSDPA； 2、LTE； 3、turbo code； 4、Mobile WiMAX； 5、LDPC

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