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/* -*- c++ -*- */
/*
* @file
* @author Piotr Krysik <ptrkrysik@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 <grgsm/gsmtap.h>
#include "control_channels_decoder_impl.h"
#define DATA_BYTES 23
namespace gr {
namespace gsm {
control_channels_decoder::sptr
control_channels_decoder::make()
{
return gnuradio::get_initial_sptr
(new control_channels_decoder_impl());
}
/*
* Constructor
*/
control_channels_decoder_impl::control_channels_decoder_impl()
: gr::block("control_channels_decoder",
gr::io_signature::make(0, 0, 0),
gr::io_signature::make(0, 0, 0)),
d_collected_bursts_num(0)
{
//initialize de/interleaver
int j, k, B;
for (k = 0; k < CONV_SIZE; k++)
{
B = k % 4;
j = 2 * ((49 * k) % 57) + ((k % 8) / 4);
interleave_trans[k] = B * 114 + j; //114=57 + 57
}
//initialize decoder
FC_init(&fc_ctx, 40, 184);
//setup input/output ports
message_port_register_in(pmt::mp("bursts"));
set_msg_handler(pmt::mp("bursts"), boost::bind(&control_channels_decoder_impl::decode, this, _1));
message_port_register_out(pmt::mp("msgs"));
}
control_channels_decoder_impl::~control_channels_decoder_impl()
{
}
void control_channels_decoder_impl::decode(pmt::pmt_t msg)
{
unsigned char iBLOCK[BLOCKS*iBLOCK_SIZE], hl, hn, conv_data[CONV_SIZE], decoded_data[PARITY_OUTPUT_SIZE];
d_bursts[d_collected_bursts_num] = msg;
d_collected_bursts_num++;
//get convecutive bursts
if(d_collected_bursts_num==4)
{
d_collected_bursts_num=0;
//reorganize data
for(int ii = 0; ii < 4; ii++)
{
pmt::pmt_t header_plus_burst = pmt::cdr(d_bursts[ii]);
int8_t * burst_bits = (int8_t *)(pmt::blob_data(header_plus_burst))+sizeof(gsmtap_hdr);
for(int jj = 0; jj < 57; jj++)
{
iBLOCK[ii*iBLOCK_SIZE+jj] = burst_bits[jj + 3];
iBLOCK[ii*iBLOCK_SIZE+jj+57] = burst_bits[jj + 88]; //88 = 3+57+1+26+1
}
}
//deinterleave
for (int k = 0; k < CONV_SIZE; k++)
{
conv_data[k] = iBLOCK[interleave_trans[k]];
}
//convolutional code decode
int errors = conv_decode(decoded_data, conv_data);
//std::cout << "Errors:" << errors << " " << parity_check(decoded_data) << std::endl;
// check parity
// If parity check error detected try to fix it.
if (parity_check(decoded_data))
{
FC_init(&fc_ctx, 40, 184);
unsigned char crc_result[PARITY_OUTPUT_SIZE];
if (FC_check_crc(&fc_ctx, decoded_data, crc_result) == 0)
{
//("error: sacch: parity error (errors=%d fn=%d)\n", errors, ctx->fn);
//std::cout << "Uncorrectable errors!" << std::endl;
errors = -1;
return;
} else {
//DEBUGF("Successfully corrected parity bits! (errors=%d fn=%d)\n", errors, ctx->fn);
//std::cout << "Corrected some errors" << std::endl;
memcpy(decoded_data, crc_result, PARITY_OUTPUT_SIZE);
errors = 0;
}
} else {
//std::cout << "Everything correct" << std::endl;
}
//compress bits
unsigned char outmsg[28];
unsigned char sbuf_len=224;
int i, j, c, pos=0;
for(i = 0; i < sbuf_len; i += 8) {
for(j = 0, c = 0; (j < 8) && (i + j < sbuf_len); j++){
c |= (!!decoded_data[i + j]) << j;
}
outmsg[pos++] = c & 0xff;
}
//send message with header of the first burst
pmt::pmt_t first_header_plus_burst = pmt::cdr(d_bursts[0]);
gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(first_header_plus_burst);
int8_t header_plus_data[sizeof(gsmtap_hdr)+DATA_BYTES];
memcpy(header_plus_data, header, sizeof(gsmtap_hdr));
memcpy(header_plus_data+sizeof(gsmtap_hdr), outmsg, DATA_BYTES);
((gsmtap_hdr*)header_plus_data)->type = GSMTAP_TYPE_UM;
pmt::pmt_t msg_binary_blob = pmt::make_blob(header_plus_data,DATA_BYTES+sizeof(gsmtap_hdr));
pmt::pmt_t msg_out = pmt::cons(pmt::PMT_NIL, msg_binary_blob);
message_port_pub(pmt::mp("msgs"), msg_out);
}
return;
}
} /* namespace gsm */
} /* namespace gr */
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