189 lines
6.6 KiB
C++
189 lines
6.6 KiB
C++
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/* -*- c++ -*- */
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/*
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* @file
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* @author Piotr Krysik <ptrkrysik@gmail.com>
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* @section LICENSE
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*
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* Gr-gsm is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* Gr-gsm is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with gr-gsm; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gnuradio/io_signature.h>
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#include "tch_f_chans_demapper_impl.h"
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#include <grgsm/endian.h>
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#include <grgsm/gsmtap.h>
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namespace gr {
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namespace gsm {
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tch_f_chans_demapper::sptr
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tch_f_chans_demapper::make(unsigned int timeslot_nr)
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{
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return gnuradio::get_initial_sptr
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(new tch_f_chans_demapper_impl(timeslot_nr));
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}
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/*
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* The private constructor
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*
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*/
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tch_f_chans_demapper_impl::tch_f_chans_demapper_impl(unsigned int timeslot_nr)
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: gr::block("tch_f_chans_demapper",
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gr::io_signature::make(0, 0, 0),
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gr::io_signature::make(0, 0, 0)),
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d_timeslot(timeslot_nr)
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{
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for(int ii=0; ii<13; ii++)
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{
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int startpos = ((int)(ii / 4) * 4);
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d_starts_fn_mod26[ii] = startpos;
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d_starts_fn_mod26[ii + 13] = startpos + 13;
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}
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d_bursts_stolen = false;
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message_port_register_in(pmt::mp("bursts"));
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set_msg_handler(pmt::mp("bursts"), boost::bind(&tch_f_chans_demapper_impl::filter_tch_chans, this, _1));
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message_port_register_out(pmt::mp("tch_bursts"));
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message_port_register_out(pmt::mp("acch_bursts"));
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}
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/*
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* Our virtual destructor.
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*/
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tch_f_chans_demapper_impl::~tch_f_chans_demapper_impl()
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{
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}
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void tch_f_chans_demapper_impl::filter_tch_chans(pmt::pmt_t msg)
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{
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pmt::pmt_t header_plus_burst = pmt::cdr(msg);
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gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(header_plus_burst);
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uint32_t frame_nr = be32toh(header->frame_number);
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uint32_t fn_mod26 = frame_nr % 26;
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uint32_t fn26_start = d_starts_fn_mod26[fn_mod26];
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uint32_t fn26_stop = fn26_start + 3;
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int8_t * burst_bits = (int8_t *)(pmt::blob_data(header_plus_burst))+sizeof(gsmtap_hdr);
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if(header->timeslot == d_timeslot){
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header->sub_type = GSMTAP_CHANNEL_TCH_F;
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if (fn_mod26 == 12 || fn_mod26 == 25)
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{
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header->sub_type = GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_F;
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// position of SACCH burst based on timeslot
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// see specification gsm 05.02
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uint32_t index;
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bool is_sacch = false;
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if (d_timeslot % 2 == 0 && fn_mod26 == 12)
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{
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index = (((frame_nr - 12) / 26) - (d_timeslot / 2)) % 4;
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is_sacch = true;
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}
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else if (d_timeslot % 2 == 1 && fn_mod26 == 25)
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{
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index = (((frame_nr - 25) / 26) - ((d_timeslot - 1) / 2)) % 4;
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is_sacch = true;
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}
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if (is_sacch)
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{
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d_bursts_sacch[index] = msg;
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d_frame_numbers_sacch[index] = frame_nr;
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if (index == 3)
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{
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//check for a situation where some bursts were lost
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//in this situation frame numbers won't be consecutive
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bool frames_are_consecutive = true;
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for(int jj=1; jj<4; jj++)
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{
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if((d_frame_numbers_sacch[jj]-d_frame_numbers_sacch[jj-1]) != 26)
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{
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frames_are_consecutive = false;
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}
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}
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if(frames_are_consecutive)
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{
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//send bursts to the output
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for(int jj=0; jj<4; jj++)
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{
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message_port_pub(pmt::mp("acch_bursts"), d_bursts_sacch[jj]);
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}
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}
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}
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}
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}
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else
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{
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if(fn_mod26>=fn26_start && fn_mod26<=fn26_stop)
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{
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uint32_t ii = fn_mod26 - fn26_start;
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d_frame_numbers[ii] = frame_nr;
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d_bursts[ii] = msg;
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// check if stealing bits are set
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// see gsm 05.03
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if (static_cast<int>(burst_bits[60]) == 1 && static_cast<int>(burst_bits[87]) == 1)
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{
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d_bursts_stolen = true;
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}
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}
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if(fn_mod26==fn26_stop)
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{
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//check for a situation where some bursts were lost
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//in this situation frame numbers won't be consecutive
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bool frames_are_consecutive = true;
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for(int jj=1; jj<4; jj++)
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{
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if((d_frame_numbers[jj]-d_frame_numbers[jj-1])!=1)
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{
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frames_are_consecutive = false;
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}
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}
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if(frames_are_consecutive)
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{
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//send bursts to the output
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for(int jj=0; jj<4; jj++)
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{
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if (d_bursts_stolen)
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{
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message_port_pub(pmt::mp("acch_bursts"), d_bursts[jj]);
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}
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else
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{
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message_port_pub(pmt::mp("tch_bursts"), d_bursts[jj]);
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}
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}
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d_bursts_stolen = false;
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}
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}
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}
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}
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}
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} /* namespace gsm */
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} /* namespace gr */
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