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/*
* (C) 2017-2018 by sysmocom - s.f.m.c. GmbH, Author: Max <msuraev@sysmocom.de>
* (C) 2018 by Vadim Yanitskiy <axilirator@gmail.com>
* (C) 2011-2012 by Luca Melette <luca@srlabs.de>
*
* All Rights Reserved
*
* SPDX-License-Identifier: GPL-2.0+
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*/
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <arpa/inet.h>
#include <osmocom/core/bits.h>
#include <osmocom/core/gsmtap.h>
#include <osmocom/coding/gsm0503_coding.h>
#include "l1ctl_proto.h"
#include "rlcmac.h"
#include "gprs.h"
/**
* We store both DL and UL burst buffers
* for all possible timeslots...
*/
static struct burst_buf burst_buf_dl[8] = { 0 };
static struct burst_buf burst_buf_ul[8] = { 0 };
int process_pdch(struct l1ctl_burst_ind *bi, bool verbose)
{
int n_errors, n_bits_total, rc, len, i;
ubit_t buf[GSM_BURST_PL_LEN];
struct gprs_message *gm;
struct burst_buf *bb;
uint8_t l2[200];
uint16_t arfcn;
uint32_t fn;
uint8_t tn;
bool ul;
/* Get burst parameters */
fn = ntohl(bi->frame_nr);
arfcn = ntohs(bi->band_arfcn);
ul = !!(arfcn & GSMTAP_ARFCN_F_UPLINK);
tn = bi->chan_nr & 7;
/* Select a proper DL / UL buffer */
bb = ul ? &burst_buf_ul[tn] : &burst_buf_dl[tn];
/* Align to first frame */
if ((bb->count == 0) && (((fn % 13) % 4) != 0))
return 0;
/* Debug print */
if (verbose)
printf("Processing %s burst fn=%u, tn=%u\n",
ul ? "UL" : "DL", fn, tn);
/* Unpack hard-bits (1 or 0) */
osmo_pbit2ubit_ext(buf, 0, bi->bits, 0, 57, 0);
osmo_pbit2ubit_ext(buf, 59, bi->bits, 57, 57, 0);
/* Set the stealing flags */
buf[57] = bi->bits[14] & 0x10;
buf[58] = bi->bits[14] & 0x20;
/* Convert hard-bits (1 or 0) to soft-bits (-127..127) */
for (i = 0; i < GSM_BURST_PL_LEN; i++)
bb->bursts[GSM_BURST_PL_LEN * bb->count + i] = buf[i] ?
-(bi->snr >> 1) : (bi->snr >> 1);
/* Store the first frame number */
if (bb->count == 0)
bb->fn_first = fn;
/* Collect the measurements */
bb->rxl[bb->count] = bi->rx_level;
bb->snr[bb->count] = bi->snr;
/* Wait until complete set of bursts (4/4) */
if (++bb->count < 4)
return 0;
/* Debug print */
if (verbose)
printf("Collected 4/4 bursts on tn=%u\n", tn);
/* Flush the burst counter */
bb->count = 0;
/* Attempt to decode */
len = gsm0503_pdtch_decode(l2, bb->bursts, NULL,
&n_errors, &n_bits_total);
/* Debug print */
if (verbose)
printf("GSM 05.03 decoding %s (%s=%d)\n",
len <= 0 ? "failed" : "success",
len <= 0 ? "rc" : "len", len);
/* Skip bad blocks... */
if (len <= 0)
return -EIO;
/**
* HACK: for some reason, the handler expects
* 53-byte messages, while libosmocoding
* generates 54 bytes ?? O_o ??
*/
len--;
/* Handle decoded message */
gm = (struct gprs_message *) malloc(sizeof(struct gprs_message) + len);
if (!gm)
return -ENOMEM;
gm->fn = bb->fn_first;
gm->arfcn = arfcn;
gm->len = len;
gm->tn = tn;
/* Average the measurements */
gm->rxl = MEAS_AVG(bb->rxl);
gm->snr = MEAS_AVG(bb->snr);
/* Copy the message payload */
memcpy(gm->msg, l2, len);
/* Handle the message */
rc = rlc_type_handler(gm);
free(gm);
return rc;
}
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