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Diffstat (limited to 'gr-fec/include/gnuradio/fec/cc_decoder.h')
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diff --git a/gr-fec/include/gnuradio/fec/cc_decoder.h b/gr-fec/include/gnuradio/fec/cc_decoder.h new file mode 100644 index 0000000000..8f29af98ca --- /dev/null +++ b/gr-fec/include/gnuradio/fec/cc_decoder.h @@ -0,0 +1,144 @@ +/* -*- c++ -*- */ +/* + * Copyright 2013-2014 Free Software Foundation, Inc. + * + * This file is part of GNU Radio + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +#ifndef INCLUDED_FEC_CC_DECODER_H +#define INCLUDED_FEC_CC_DECODER_H + +#include <gnuradio/fec/api.h> +#include <gnuradio/fec/generic_decoder.h> +#include <gnuradio/fec/cc_common.h> +#include <map> +#include <string> + +namespace gr { + namespace fec { + namespace code { + + typedef void(*conv_kernel)(unsigned char *Y, unsigned char *X, + unsigned char *syms, unsigned char *dec, + unsigned int framebits, unsigned int excess, + unsigned char *Branchtab); + + /*! + * \brief Convolutional Code Decoding class. + * \ingroup error_coding_blk + * + * \details + * This class performs convolutional decoding via the Viterbi + * algorithm. While it is set up to take variable values for K, + * rate, and the polynomials, currently, the block is only + * capable of handling the following settings: + * + * \li K = 7 + * \li rate = 1/2 (given as 2 to the constructor) + * \li polynomials = [109, 79] + * + * This is the well-known convolutional part of the Voyager code + * implemented in the CCSDS encoder. + * + * The intent of having this FECAPI code classes fully + * parameterizable is to eventually allow it to take on generic + * settings, much like the cc_encoder class where the CCSDS + * settings would be a highly-optimized version of this. + * + * The decoder is set up with a number of bits per frame in the + * constructor. When not being used in a tagged stream mode, + * this encoder will only process frames of the length provided + * here. If used in a tagged stream block, this setting becomes + * the maximum allowable frame size that the block may process. + * + * The \p mode is a cc_mode_t that specifies how the convolutional + * encoder will behave and under what conditions. + * + * \li 'CC_STREAMING': mode expects an uninterrupted flow of + * samples into the encoder, and the output stream is + * continually encoded. This mode is the only mode for this + * decoder that has a history requirement because it requires + * rate*(K-1) bits more to finish the decoding properly. This + * mode does not work with any deployments that do not allow + * history. + * + * \li 'CC_TERMINATED': is a mode designed for packet-based + * systems. This mode adds rate*(k-1) bits to the output as a + * way to help flush the decoder. + * + * \li 'CC_TAILBITING': is another packet-based method. Instead of + * adding bits onto the end of the packet, this mode will + * continue the code between the payloads of packets by + * pre-initializing the state of the new packet based on the + * state of the last packet for (k-1) bits. + * + * \li 'CC_TRUNCATED': a truncated code always resets the registers + * to the \p start_state between frames. + * + * A common convolutional encoder uses K=7, Rate=1/2, + * Polynomials=[109, 79]. This is the Voyager code from NASA: + * \li 109: b(1101101) --> 1 + x + x^3 + x^4 + x^6 + * \li 79: b(1001111) --> 1 + x^3 + x^4 + x^5 + x^6 + */ + class FEC_API cc_decoder : virtual public generic_decoder + { + public: + + /*! + * Build a convolutional code decoding FEC API object. + * + * \param frame_size Number of bits per frame. If using in the + * tagged stream style, this is the maximum allowable + * number of bits per frame. + * \param k Constraint length (K) of the encoder. + * \param rate Inverse of the coder's rate + * (rate=2 means 2 output bits per 1 input). + * \param polys Vector of polynomials as integers. + * \param start_state Initialization state of the shift register. + * \param end_state Ending state of the shift register. + * \param mode cc_mode_t mode of the encoding. + * \param padded true if the encoded frame is padded + * to the nearest byte. + */ + static generic_decoder::sptr make + (int frame_size, int k, + int rate, std::vector<int> polys, + int start_state=0, int end_state=-1, + cc_mode_t mode=CC_STREAMING, + bool padded=false); + + /*! + * Sets the uncoded frame size to \p frame_size. If \p + * frame_size is greater than the value given to the + * constructor, the frame size will be capped by that initial + * value and this function will return false. Otherwise, it + * returns true. + */ + virtual bool set_frame_size(unsigned int frame_size) = 0; + + /*! + * Returns the coding rate of this encoder. + */ + virtual double rate() = 0; + }; + + } /* namespace code */ + } /* namespace fec */ +} /* namespace gr */ + +#endif /* INCLUDED_FEC_CC_DECODER_H */ |