lib/demapping/tch_h_chans_demapper_impl.cc

/* -*- c++ -*- */
/*
 * @file
 * @author (C) 2018 by Andrew Artyushok <loony.developer@gmail.com>
 * @author (C) 2018 by Vasil Velichkov <vvvelichkov@gmail.com>
 * @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 <gnuradio/io_signature.h>
#include "tch_h_chans_demapper_impl.h"
#include <grgsm/endian.h>
#include <grgsm/gsmtap.h>

#define BURST_SIZE 148

namespace gr {
namespace gsm {

tch_h_chans_demapper::sptr
tch_h_chans_demapper::make(unsigned int timeslot_nr, unsigned int tch_h_channel)
{
        return gnuradio::get_initial_sptr
                       (new tch_h_chans_demapper_impl(timeslot_nr, tch_h_channel));
}

/*
 * The private constructor
 *
 */
tch_h_chans_demapper_impl::tch_h_chans_demapper_impl(unsigned int timeslot_nr, unsigned int tch_h_channel)
        : gr::block("tch_h_chans_demapper",
                    gr::io_signature::make(0, 0, 0),
                    gr::io_signature::make(0, 0, 0)),
        d_timeslot(timeslot_nr),
        d_tch_h_channel(tch_h_channel)

{
    //std::cout << "d_tch_type is " << d_tch_type << ", tch_h_channel is " << tch_h_channel << std::endl;

    message_port_register_in(pmt::mp("bursts"));
    set_msg_handler(pmt::mp("bursts"), boost::bind(&tch_h_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_h_chans_demapper_impl::~tch_h_chans_demapper_impl()
{
}

void tch_h_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);
    if(header->timeslot != d_timeslot) {
        return;
    }

    uint32_t frame_nr = be32toh(header->frame_number);
    uint32_t fn_mod26 = frame_nr % 26;
    uint32_t fn_mod13 = frame_nr % 13;
    int8_t* burst_bits = (int8_t *)(pmt::blob_data(header_plus_burst)) + sizeof(gsmtap_hdr);

    int8_t new_msg[sizeof(gsmtap_hdr)+BURST_SIZE];
    gsmtap_hdr * new_hdr = (gsmtap_hdr*)new_msg;
    memcpy(new_msg, header, sizeof(gsmtap_hdr)+BURST_SIZE);

    new_hdr->sub_type = (fn_mod13 == 12 ? GSMTAP_CHANNEL_ACCH : 0) | GSMTAP_CHANNEL_TCH_H;

    pmt::pmt_t msg_binary_blob = pmt::make_blob(new_msg,sizeof(gsmtap_hdr)+BURST_SIZE);
    pmt::pmt_t msg_out = pmt::cons(pmt::PMT_NIL, msg_binary_blob);

    //distinguishing uplink and downlink bursts
    bool uplink_burst = (be16toh(header->arfcn) & 0x4000) ? true : false;

    if(uplink_burst)
    {
        sacch_tch_demapper(fn_mod13, fn_mod26, frame_nr, d_bursts_sacch_ul,
                d_frame_numbers_sacch_ul, d_bursts_ul, d_frame_numbers_ul, msg_out);
    }
    else
    {
        sacch_tch_demapper(fn_mod13, fn_mod26, frame_nr, d_bursts_sacch_dl,
                d_frame_numbers_sacch_dl, d_bursts_dl, d_frame_numbers_dl, msg_out);
    }
}

void tch_h_chans_demapper_impl::sacch_tch_demapper(uint32_t fn_mod13, u_int32_t fn_mod26, uint32_t frame_nr,
                                                   pmt::pmt_t *d_bursts_sacch,
                                                   uint32_t *d_frame_numbers_sacch, pmt::pmt_t d_bursts[3][8],
                                                   uint32_t d_frame_numbers[3][8], pmt::pmt_t msg_out)
{
    bool frames_are_consecutive = true;
    if (fn_mod13 == 12)
    {
        // position of SACCH burst based on timeslot
        // see specification gsm 05.02
        uint32_t index;
        bool is_sacch = false;

        if (d_tch_h_channel == 0 && fn_mod26 == 12)
        {
            index = (((frame_nr - 12) / 26) - (d_timeslot / 2)) % 4;
            is_sacch = true;
        }
        else if (d_tch_h_channel == 1 && fn_mod26 == 25)
        {
            index = (((frame_nr - 25) / 26) - (d_timeslot / 2)) % 4;
            is_sacch = true;
        }

        if (is_sacch)
        {
            d_bursts_sacch[index] = msg_out;
            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
                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
    {
        bool our_sub=false;
        // So, here I change the fn_mod13, with this changes I can
        // process both subslot (d_tch_h_channel) with the same code.
        //
        // Theory about this on github
        //
        // Example:
        //
        // For subslot=0 our burst is 0,2,4,6 etc
        // For subslot=1 it 1,3,5 etc
        // But if we change it with this code,
        // both will be 0,1,2,3,4 etc
        // And we can proced two subslot like one.
        if(fn_mod13%2==d_tch_h_channel) {
            if(d_tch_h_channel==0) {
                fn_mod13=fn_mod13/2;
            }else{
                fn_mod13-=1;
                fn_mod13=fn_mod13/2;
            }
            // We work only with our subslot
            our_sub=true;
        }
        if(our_sub) {

            if (fn_mod13 <= 1)
            {
                // add to b1 and b3
                d_bursts[0][fn_mod13] = msg_out;
                d_bursts[2][fn_mod13+2] = msg_out;



                d_frame_numbers[0][fn_mod13] = frame_nr;
                d_frame_numbers[2][fn_mod13+2] = frame_nr;
            }
            else if (fn_mod13 >=2 && fn_mod13 <=3)
            {
                // add to b1 and b2
                d_bursts[0][fn_mod13] = msg_out;
                d_bursts[1][fn_mod13-2] = msg_out;


                d_frame_numbers[0][fn_mod13] = frame_nr;
                d_frame_numbers[1][fn_mod13-2] = frame_nr;
                //d_frame_numbers[1][fn_mod13 - 4] = frame_nr;
            }
            else if (fn_mod13 >=4 && fn_mod13 <=5)
            {
                // add to b1 and b2
                d_bursts[1][fn_mod13-2] = msg_out;
                d_bursts[2][fn_mod13-4] = msg_out;



                d_frame_numbers[1][fn_mod13-2] = frame_nr;
                d_frame_numbers[2][fn_mod13-4] = frame_nr;
                //d_frame_numbers[1][fn_mod13 - 4] = frame_nr;
            }
            // send burst 1 or burst 2 to output
            //if ( fn_mod26 == 2 || fn_mod26 == 5 || fn_mod26 == 9)
            if(fn_mod13 == 1 || fn_mod13 == 3|| fn_mod13 == 5)
            {
                int tch_burst_nr = 0;

                if(fn_mod13==5) {
                    tch_burst_nr = 1;
                }
                if(fn_mod13==1) {
                    tch_burst_nr = 2;
                }

                //check for a situation where some bursts were lost
                //in this situation frame numbers won't be consecutive
                frames_are_consecutive = true;
                // std::cout<<"br="<<tch_burst_nr<<" Array: ";
                // std::cout<<d_frame_numbers[tch_burst_nr][0]<<" ";
                bool one_tree=true;
                for(int jj=1; jj<4; jj++)
                {

                    if (((d_frame_numbers[tch_burst_nr][jj] - d_frame_numbers[tch_burst_nr][jj-1]) != 2) && frames_are_consecutive)
                    {
                        frames_are_consecutive = false;

                        if (tch_burst_nr == 2 && jj == 2
                                && d_frame_numbers[tch_burst_nr][jj] - d_frame_numbers[tch_burst_nr][jj - 1] == 3)
                        {
                            //  std::cout<<" YEAH ";
                            frames_are_consecutive = true;
                        }

                    }
                    //}
            }
            // std::cout<<std::endl;

            if(frames_are_consecutive)
            {

                for(int jj=0; jj<4; jj++)
                {

                    message_port_pub(pmt::mp("tch_bursts"), d_bursts[tch_burst_nr][jj]);
                }

                // useless
                //                        d_bursts_stolen[tch_burst_nr] = false;
            }
        }
    }

}
}
}   /* namespace gsm */
} /* namespace gr */