From fb6bc5009f4ca3b56c9dad5081747ad54eb43934 Mon Sep 17 00:00:00 2001 From: Roman Khassraf Date: Tue, 14 Apr 2015 15:44:40 +0200 Subject: Implementation of TCH/F demapper block. See issue #38 --- lib/demapping/tch_f_chans_demapper_impl.cc | 188 +++++++++++++++++++++++++++++ lib/demapping/tch_f_chans_demapper_impl.h | 52 ++++++++ 2 files changed, 240 insertions(+) create mode 100644 lib/demapping/tch_f_chans_demapper_impl.cc create mode 100644 lib/demapping/tch_f_chans_demapper_impl.h (limited to 'lib/demapping') diff --git a/lib/demapping/tch_f_chans_demapper_impl.cc b/lib/demapping/tch_f_chans_demapper_impl.cc new file mode 100644 index 0000000..a2458f1 --- /dev/null +++ b/lib/demapping/tch_f_chans_demapper_impl.cc @@ -0,0 +1,188 @@ +/* -*- c++ -*- */ +/* + * @file + * @author Piotr Krysik + * @section LICENSE + * + * Gr-gsm 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. + * + * Gr-gsm 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 gr-gsm; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include +#include "tch_f_chans_demapper_impl.h" +#include +#include + +namespace gr { + namespace gsm { + + tch_f_chans_demapper::sptr + tch_f_chans_demapper::make(unsigned int timeslot_nr) + { + return gnuradio::get_initial_sptr + (new tch_f_chans_demapper_impl(timeslot_nr)); + } + + /* + * The private constructor + * + */ + tch_f_chans_demapper_impl::tch_f_chans_demapper_impl(unsigned int timeslot_nr) + : gr::block("tch_f_chans_demapper", + gr::io_signature::make(0, 0, 0), + gr::io_signature::make(0, 0, 0)), + d_timeslot(timeslot_nr) + + { + for(int ii=0; ii<13; ii++) + { + int startpos = ((int)(ii / 4) * 4); + d_starts_fn_mod26[ii] = startpos; + d_starts_fn_mod26[ii + 13] = startpos + 13; + } + + d_bursts_stolen = false; + + message_port_register_in(pmt::mp("bursts")); + set_msg_handler(pmt::mp("bursts"), boost::bind(&tch_f_chans_demapper_impl::filter_tch_chans, this, _1)); + message_port_register_out(pmt::mp("tch_bursts")); + message_port_register_out(pmt::mp("acch_bursts")); + } + + /* + * Our virtual destructor. + */ + tch_f_chans_demapper_impl::~tch_f_chans_demapper_impl() + { + } + + void tch_f_chans_demapper_impl::filter_tch_chans(pmt::pmt_t msg) + { + pmt::pmt_t header_plus_burst = pmt::cdr(msg); + gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(header_plus_burst); + + uint32_t frame_nr = be32toh(header->frame_number); + uint32_t fn_mod26 = frame_nr % 26; + uint32_t fn26_start = d_starts_fn_mod26[fn_mod26]; + uint32_t fn26_stop = fn26_start + 3; + int8_t * burst_bits = (int8_t *)(pmt::blob_data(header_plus_burst))+sizeof(gsmtap_hdr); + + if(header->timeslot == d_timeslot){ + header->sub_type = GSMTAP_CHANNEL_TCH_F; + + if (fn_mod26 == 12 || fn_mod26 == 25) + { + header->sub_type = GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_F; + + // position of SACCH burst based on timeslot + // see specification gsm 05.02 + uint32_t index; + bool is_sacch = false; + + if (d_timeslot % 2 == 0 && fn_mod26 == 12) + { + index = (((frame_nr - 12) / 26) - (d_timeslot / 2)) % 4; + is_sacch = true; + } + else if (d_timeslot % 2 == 1 && fn_mod26 == 25) + { + index = (((frame_nr - 25) / 26) - ((d_timeslot - 1) / 2)) % 4; + is_sacch = true; + } + + if (is_sacch) + { + d_bursts_sacch[index] = msg; + d_frame_numbers_sacch[index] = frame_nr; + + if (index == 3) + { + //check for a situation where some bursts were lost + //in this situation frame numbers won't be consecutive + bool frames_are_consecutive = true; + for(int jj=1; jj<4; jj++) + { + if((d_frame_numbers_sacch[jj]-d_frame_numbers_sacch[jj-1]) != 26) + { + frames_are_consecutive = false; + } + } + if(frames_are_consecutive) + { + //send bursts to the output + for(int jj=0; jj<4; jj++) + { + message_port_pub(pmt::mp("acch_bursts"), d_bursts_sacch[jj]); + } + } + } + } + } + else + { + if(fn_mod26>=fn26_start && fn_mod26<=fn26_stop) + { + uint32_t ii = fn_mod26 - fn26_start; + d_frame_numbers[ii] = frame_nr; + d_bursts[ii] = msg; + + // check if stealing bits are set + // see gsm 05.03 + if (static_cast(burst_bits[60]) == 1 && static_cast(burst_bits[87]) == 1) + { + d_bursts_stolen = true; + } + } + + if(fn_mod26==fn26_stop) + { + //check for a situation where some bursts were lost + //in this situation frame numbers won't be consecutive + bool frames_are_consecutive = true; + + for(int jj=1; jj<4; jj++) + { + if((d_frame_numbers[jj]-d_frame_numbers[jj-1])!=1) + { + frames_are_consecutive = false; + } + } + if(frames_are_consecutive) + { + //send bursts to the output + for(int jj=0; jj<4; jj++) + { + if (d_bursts_stolen) + { + message_port_pub(pmt::mp("acch_bursts"), d_bursts[jj]); + } + else + { + message_port_pub(pmt::mp("tch_bursts"), d_bursts[jj]); + } + } + d_bursts_stolen = false; + } + } + } + } + } + } /* namespace gsm */ +} /* namespace gr */ + diff --git a/lib/demapping/tch_f_chans_demapper_impl.h b/lib/demapping/tch_f_chans_demapper_impl.h new file mode 100644 index 0000000..8abbc91 --- /dev/null +++ b/lib/demapping/tch_f_chans_demapper_impl.h @@ -0,0 +1,52 @@ +/* -*- c++ -*- */ +/* + * @file + * @author Piotr Krysik + * @section LICENSE + * + * Gr-gsm 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. + * + * Gr-gsm 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 gr-gsm; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +#ifndef INCLUDED_GSM_UNIVERSAL_TCH_CHANS_DEMAPPER_IMPL_H +#define INCLUDED_GSM_UNIVERSAL_TCH_CHANS_DEMAPPER_IMPL_H + +#include + +namespace gr { + namespace gsm { + + class tch_f_chans_demapper_impl : public tch_f_chans_demapper + { + private: + unsigned int d_starts_fn_mod26[26]; + unsigned int d_timeslot; + uint32_t d_frame_numbers[4]; + uint32_t d_frame_numbers_sacch[4]; + pmt::pmt_t d_bursts[4]; + bool d_bursts_stolen; + pmt::pmt_t d_bursts_sacch[4]; + public: + tch_f_chans_demapper_impl(unsigned int timeslot_nr); + ~tch_f_chans_demapper_impl(); + + void filter_tch_chans(pmt::pmt_t msg); + }; + + } // namespace gsm +} // namespace gr + +#endif /* INCLUDED_GSM_UNIVERSAL_TCH_CHANS_DEMAPPER_IMPL_H */ + -- cgit v1.2.3