158 lines
5.6 KiB
C++
158 lines
5.6 KiB
C++
/* -*- 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 <grgsm/gsmtap.h>
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#include "control_channels_decoder_impl.h"
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#define DATA_BYTES 23
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namespace gr {
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namespace gsm {
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control_channels_decoder::sptr
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control_channels_decoder::make()
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{
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return gnuradio::get_initial_sptr
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(new control_channels_decoder_impl());
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}
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/*
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* Constructor
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*/
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control_channels_decoder_impl::control_channels_decoder_impl()
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: gr::block("control_channels_decoder",
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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_collected_bursts_num(0)
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{
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//initialize de/interleaver
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int j, k, B;
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for (k = 0; k < CONV_SIZE; k++)
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{
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B = k % 4;
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j = 2 * ((49 * k) % 57) + ((k % 8) / 4);
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interleave_trans[k] = B * 114 + j; //114=57 + 57
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}
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//initialize decoder
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FC_init(&fc_ctx, 40, 184);
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//setup input/output ports
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message_port_register_in(pmt::mp("bursts"));
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set_msg_handler(pmt::mp("bursts"), boost::bind(&control_channels_decoder_impl::decode, this, _1));
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message_port_register_out(pmt::mp("msgs"));
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}
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control_channels_decoder_impl::~control_channels_decoder_impl()
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{
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}
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void control_channels_decoder_impl::decode(pmt::pmt_t msg)
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{
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unsigned char iBLOCK[BLOCKS*iBLOCK_SIZE], hl, hn, conv_data[CONV_SIZE], decoded_data[PARITY_OUTPUT_SIZE];
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d_bursts[d_collected_bursts_num] = msg;
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d_collected_bursts_num++;
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//get convecutive bursts
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if(d_collected_bursts_num==4)
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{
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d_collected_bursts_num=0;
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//reorganize data
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for(int ii = 0; ii < 4; ii++)
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{
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pmt::pmt_t header_plus_burst = pmt::cdr(d_bursts[ii]);
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int8_t * burst_bits = (int8_t *)(pmt::blob_data(header_plus_burst))+sizeof(gsmtap_hdr);
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for(int jj = 0; jj < 57; jj++)
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{
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iBLOCK[ii*iBLOCK_SIZE+jj] = burst_bits[jj + 3];
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iBLOCK[ii*iBLOCK_SIZE+jj+57] = burst_bits[jj + 88]; //88 = 3+57+1+26+1
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}
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}
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//deinterleave
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for (int k = 0; k < CONV_SIZE; k++)
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{
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conv_data[k] = iBLOCK[interleave_trans[k]];
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}
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//convolutional code decode
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int errors = conv_decode(decoded_data, conv_data);
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//std::cout << "Errors:" << errors << " " << parity_check(decoded_data) << std::endl;
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// check parity
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// If parity check error detected try to fix it.
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if (parity_check(decoded_data))
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{
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FC_init(&fc_ctx, 40, 184);
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unsigned char crc_result[PARITY_OUTPUT_SIZE];
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if (FC_check_crc(&fc_ctx, decoded_data, crc_result) == 0)
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{
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//("error: sacch: parity error (errors=%d fn=%d)\n", errors, ctx->fn);
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//std::cout << "Uncorrectable errors!" << std::endl;
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errors = -1;
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return;
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} else {
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//DEBUGF("Successfully corrected parity bits! (errors=%d fn=%d)\n", errors, ctx->fn);
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//std::cout << "Corrected some errors" << std::endl;
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memcpy(decoded_data, crc_result, PARITY_OUTPUT_SIZE);
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errors = 0;
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}
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} else {
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//std::cout << "Everything correct" << std::endl;
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}
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//compress bits
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unsigned char outmsg[27];
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unsigned char sbuf_len=224;
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int i, j, c, pos=0;
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for(i = 0; i < sbuf_len; i += 8) {
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for(j = 0, c = 0; (j < 8) && (i + j < sbuf_len); j++){
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c |= (!!decoded_data[i + j]) << j;
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}
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outmsg[pos++] = c & 0xff;
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}
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//send message with header of the first burst
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pmt::pmt_t first_header_plus_burst = pmt::cdr(d_bursts[0]);
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gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(first_header_plus_burst);
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header->type = GSMTAP_TYPE_UM;
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int8_t * header_content = (int8_t *)header;
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int8_t header_plus_data[sizeof(gsmtap_hdr)+DATA_BYTES];
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memcpy(header_plus_data, header_content, sizeof(gsmtap_hdr));
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memcpy(header_plus_data+sizeof(gsmtap_hdr), outmsg, DATA_BYTES);
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pmt::pmt_t msg_binary_blob = pmt::make_blob(header_plus_data,DATA_BYTES+sizeof(gsmtap_hdr));
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pmt::pmt_t msg_out = pmt::cons(pmt::PMT_NIL, msg_binary_blob);
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message_port_pub(pmt::mp("msgs"), msg_out);
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}
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return;
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}
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} /* namespace gsm */
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} /* namespace gr */
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