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/* -*- c++ -*- */
/*
* @file
* @author (C) 2014 by 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.
*/
#include <string.h>
#include "gsm_constants.h"
#include "osmocom/coding/gsm0503_coding.h"
#include <osmocom/core/utils.h>
static int ubits2sbits(ubit_t *ubits, sbit_t *sbits, int count)
{
int i;
for (i = 0; i < count; i++) {
if (*ubits == 0x23) {
ubits++;
sbits++;
continue;
}
if ((*ubits++) & 1)
*sbits++ = -127;
else
*sbits++ = 127;
}
return count;
}
int decode_sch(const unsigned char *buf, int * t1_o, int * t2_o, int * t3_o, int * ncc_o, int * bcc_o)
{
int t1, t2, t3p, t3, ncc, bcc;
uint8_t result[4];
ubit_t bursts_u[SCH_DATA_LEN*2];
sbit_t bursts_s[SCH_DATA_LEN*2];
// extract encoded data from synchronization burst
/* buf, 39 bit */
/* buf + 39 + 64 = 103, 39 */
memcpy(bursts_u, buf, SCH_DATA_LEN);
memcpy(bursts_u + SCH_DATA_LEN, buf + SCH_DATA_LEN + N_SYNC_BITS, SCH_DATA_LEN);
ubits2sbits(bursts_u, bursts_s, SCH_DATA_LEN*2);
if(gsm0503_sch_decode(result, bursts_s)==-1){
return 1;
}
// Synchronization channel information, 44.018 page 171. (V7.2.0)
uint8_t decoded_data[25];
osmo_pbit2ubit_ext(decoded_data, 0, result, 0, 25, 1);
ncc =
(decoded_data[ 7] << 2) |
(decoded_data[ 6] << 1) |
(decoded_data[ 5] << 0);
bcc =
(decoded_data[ 4] << 2) |
(decoded_data[ 3] << 1) |
(decoded_data[ 2] << 0);
t1 =
(decoded_data[ 1] << 10) |
(decoded_data[ 0] << 9) |
(decoded_data[15] << 8) |
(decoded_data[14] << 7) |
(decoded_data[13] << 6) |
(decoded_data[12] << 5) |
(decoded_data[11] << 4) |
(decoded_data[10] << 3) |
(decoded_data[ 9] << 2) |
(decoded_data[ 8] << 1) |
(decoded_data[23] << 0);
t2 =
(decoded_data[22] << 4) |
(decoded_data[21] << 3) |
(decoded_data[20] << 2) |
(decoded_data[19] << 1) |
(decoded_data[18] << 0);
t3p =
(decoded_data[17] << 2) |
(decoded_data[16] << 1) |
(decoded_data[24] << 0);
t3 = 10 * t3p + 1;
// modulo arithmetic t3 - t2 mod 26
// tt = ((t3 + 26) - t2) % 26;
// fn = (51 * 26 * t1) + (51 * tt) + t3;
/*
* BSIC: Base Station Identification Code
* BCC: Base station Color Code
* NCC: Network Color Code
*
* FN: Frame Number
*/
// printf("bsic: %x (bcc: %u; ncc: %u)\tFN: %u\n", bsic, bsic & 7,
// (bsic >> 3) & 7, fn);
// if (fn_o)
// *fn_o = fn;
// if (bsic_o)
if (t1_o && t2_o && t3_o && ncc_o && bcc_o) {
*t1_o = t1;
*t2_o = t2;
*t3_o = t3;
*bcc_o = bcc;
*ncc_o = ncc;
}
return 0;
}
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