/*
* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
* (C) 2015-2017 by Harald Welte <laforge@gnumonks.org>
* (C) 2020-2023 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <stdint.h>
#include <errno.h>
#include <osmocom/core/bits.h>
#include <osmocom/core/msgb.h>
#include <osmocom/core/utils.h>
#include <osmocom/gsm/gsm0502.h>
#include <osmocom/codec/codec.h>
#include <osmocom/coding/gsm0503_coding.h>
#include <osmocom/coding/gsm0503_amr_dtx.h>
#include <osmocom/netif/amr.h>
#include <osmo-bts/bts.h>
#include <osmo-bts/l1sap.h>
#include <osmo-bts/logging.h>
#include <osmo-bts/scheduler.h>
#include <osmo-bts/scheduler_backend.h>
#include <osmo-bts/msg_utils.h>
#include <sched_utils.h>
#include <amr_loop.h>
/* 3GPP TS 45.009, table 3.2.1.3-{2,4}: AMR on Uplink TCH/H.
*
* +---+---+---+---+---+---+
* | a | b | c | d | e | f | Burst 'a' received first
* +---+---+---+---+---+---+
* ^^^^^^^^^^^^^^^^^^^^^^^ FACCH frame (bursts 'a' .. 'f')
* ^^^^^^^^^^^^^^^ Speech frame (bursts 'a' .. 'd')
*
* TDMA frame number of burst 'f' is always used as the table index. */
static const uint8_t sched_tchh_ul_amr_cmi_map[26] = {
[10] = 1, /* TCH/H(0): a=0 / d=6 / f=10 */
[19] = 1, /* TCH/H(0): a=8 / d=15 / f=19 */
[2] = 1, /* TCH/H(0): a=17 / d=23 / f=2 */
[11] = 1, /* TCH/H(1): a=1 / d=7 / f=11 */
[20] = 1, /* TCH/H(1): a=9 / d=16 / f=20 */
[3] = 1, /* TCH/H(1): a=18 / d=24 / f=3 */
};
/* TDMA frame number of burst 'a' should be used as the table index.
* This mapping is valid for both FACCH/H(0) and FACCH/H(1). */
const uint8_t sched_tchh_dl_amr_cmi_map[26] = {
[4] = 1, /* TCH/H(0): a=4 */
[13] = 1, /* TCH/H(0): a=13 */
[21] = 1, /* TCH/H(0): a=21 */
[5] = 1, /* TCH/H(1): a=5 */
[14] = 1, /* TCH/H(1): a=14 */
[22] = 1, /* TCH/H(1): a=22 */
};
/* 3GPP TS 45.002, table 1 in clause 7: Mapping tables.
* TDMA frame number of burst 'f' is always used as the table index. */
static const uint8_t sched_tchh_ul_facch_map[26] = {
[10] = 1, /* FACCH/H(0): B0(0,2,4,6,8,10) */
[11] = 1, /* FACCH/H(1): B0(1,3,5,7,9,11) */
[19] = 1, /* FACCH/H(0): B1(8,10,13,15,17,19) */
[20] = 1, /* FACCH/H(1): B1(9,11,14,16,18,20) */
[2] = 1, /* FACCH/H(0): B2(17,19,21,23,0,2) */
[3] = 1, /* FACCH/H(1): B2(18,20,22,24,1,3) */
};
/* TDMA frame number of burst 'a' is used as the table index. */
extern const uint8_t sched_tchh_dl_facch_map[26];
/* 3GPP TS 45.002, table 2 in clause 7: Mapping tables for TCH/H2.4 and TCH/H4.8.
*
* +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
* | a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v |
* +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
*
* TCH/H(0): B0(0,2,4,6,8,10,13,15,17,19,21,23,0,2,4,6,8,10,13,15,17,19)
* TCH/H(1): B0(1,3,5,7,9,11,14,16,18,20,22,24,1,3,5,7,9,11,14,16,18,20)
* TCH/H(0): B1(8,10,13,15,17,19,21,23,0,2,4,6,8,10,13,15,17,19,21,23,0,2)
* TCH/H(1): B1(9,11,14,16,18,20,22,24,1,3,5,7,9,11,14,16,18,20,22,24,1,3)
* TCH/H(0): B2(17,19,21,23,0,2,4,6,8,10,13,15,17,19,21,23,0,2,4,6,8,10)
* TCH/H(1): B2(18,20,22,24,1,3,5,7,9,11,14,16,18,20,22,24,1,3,5,7,9,11)
*
* TDMA frame number of burst 'v' % 26 is the table index.
* This mapping is valid for both TCH/H(0) and TCH/H(1). */
static const uint8_t sched_tchh_ul_csd_map[26] = {
[19] = 1, /* TCH/H(0): B0(0 ... 19) */
[20] = 1, /* TCH/H(1): B0(1 ... 20) */
[2] = 1, /* TCH/H(0): B1(8 ... 2) */
[3] = 1, /* TCH/H(1): B1(9 ... 3) */
[10] = 1, /* TCH/H(0): B2(17 ... 10) */
[11] = 1, /* TCH/H(1): B2(18 ... 11) */
};
/* TDMA frame number of burst 'a' % 26 is the table index.
* This mapping is valid for both TCH/H(0) and TCH/H(1). */
extern const uint8_t sched_tchh_dl_csd_map[26];
static int decode_hr_facch(struct l1sched_ts *l1ts,
const struct trx_ul_burst_ind *bi)
{
struct l1sched_chan_state *chan_state = &l1ts->chan_state[bi->chan];
const sbit_t *bursts_p = chan_state->ul_bursts;
struct l1sched_meas_set meas_avg;
uint8_t data[GSM_MACBLOCK_LEN];
int n_errors, n_bits_total;
int rc;
rc = gsm0503_tch_hr_facch_decode(&data[0], BUFTAIL8(bursts_p),
&n_errors, &n_bits_total);
if (rc != GSM_MACBLOCK_LEN)
return rc;
/* average measurements of the last 6 bursts, obtain TDMA Fn of the first burst */
trx_sched_meas_avg(chan_state, &meas_avg, SCHED_MEAS_AVG_M_S6N6);
_sched_compose_ph_data_ind(l1ts, meas_avg.fn, bi->chan,
&data[0], GSM_MACBLOCK_LEN,
compute_ber10k(n_bits_total, n_errors),
meas_avg.rssi,
meas_avg.toa256,
meas_avg.ci_cb,
PRES_INFO_UNKNOWN);
return GSM_MACBLOCK_LEN;
}
/* Process a single Uplink TCH/H burst received by the PHY.
* This function is visualized in file 'doc/trx_sched_tch.txt'. */
int rx_tchh_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
{
struct l1sched_chan_state *chan_state = &l1ts->chan_state[bi->chan];
struct gsm_lchan *lchan = chan_state->lchan;
sbit_t *burst, *bursts_p = chan_state->ul_bursts;
uint32_t *mask = &chan_state->ul_mask;
uint8_t rsl_cmode = chan_state->rsl_cmode;
uint8_t tch_mode = chan_state->tch_mode;
uint8_t tch_data[240]; /* large enough to hold 240 unpacked bits for CSD */
int rc = 0; /* initialize to make gcc happy */
int amr = 0;
int n_errors = 0;
int n_bits_total = 0;
enum sched_meas_avg_mode meas_avg_mode = SCHED_MEAS_AVG_M_S6N4;
struct l1sched_meas_set meas_avg;
unsigned int fn_begin;
uint16_t ber10k = 0;
uint8_t is_sub = 0;
uint8_t ft;
bool fn_is_cmi;
/* If handover RACH detection is turned on, treat this burst as an Access Burst.
* Handle NOPE.ind as usually to ensure proper Uplink measurement reporting. */
if (chan_state->ho_rach_detect == 1 && ~bi->flags & TRX_BI_F_NOPE_IND)
return rx_rach_fn(l1ts, bi);
LOGL1SB(DL1P, LOGL_DEBUG, l1ts, bi, "Received TCH/H, bid=%u\n", bi->bid);
/* shift the buffer by 2 bursts leftwards */
if (bi->bid == 0) {
memmove(BUFPOS(bursts_p, 0), BUFPOS(bursts_p, 2), 20 * BPLEN);
memset(BUFPOS(bursts_p, 20), 0, 2 * BPLEN);
*mask = *mask << 2;
}
/* update mask */
*mask |= (1 << bi->bid);
/* store measurements */
trx_sched_meas_push(chan_state, bi);
/* copy burst to end of buffer of 24 bursts */
burst = BUFPOS(bursts_p, 20 + bi->bid);
if (bi->burst_len > 0) {
memcpy(burst, bi->burst + 3, 58);
memcpy(burst + 58, bi->burst + 87, 58);
}
/* wait until complete set of bursts */
if (bi->bid != 1)
return 0;
/* fill up the burst buffer so that we have 6 bursts in there */
if (OSMO_UNLIKELY((*mask & 0x3f) != 0x3f)) {
LOGL1SB(DL1P, LOGL_DEBUG, l1ts, bi,
"UL burst buffer is not filled up: mask=0x%02x != 0x3f\n",
*mask);
return 0; /* TODO: send BFI */
}
/* skip decoding of the last 4 bursts of FACCH/H */
if (chan_state->ul_ongoing_facch) {
chan_state->ul_ongoing_facch = 0;
/* we have already sent the first BFI when a FACCH/H frame
* was decoded (see below), now send the second one. */
trx_sched_meas_avg(chan_state, &meas_avg, meas_avg_mode);
/* meas_avg.fn now contains TDMA frame number of the first burst */
fn_begin = meas_avg.fn;
goto bfi;
}
/* TCH/H: speech and signalling frames are interleaved over 4 and 6 bursts,
* respectively, while CSD frames are interleaved over 22 bursts. Unless
* we're in CSD mode, decode only the last 6 bursts to avoid introducing
* additional delays. */
switch (tch_mode) {
case GSM48_CMODE_SIGN:
meas_avg_mode = SCHED_MEAS_AVG_M_S6N6;
/* fall-through */
case GSM48_CMODE_SPEECH_V1: /* HR or signalling */
rc = gsm0503_tch_hr_decode2(tch_data, BUFTAIL8(bursts_p),
!sched_tchh_ul_facch_map[bi->fn % 26],
&n_errors, &n_bits_total);
if (rc == GSM_HR_BYTES) { /* only for valid *speech* frames */
bool is_sid = osmo_hr_check_sid(tch_data, GSM_HR_BYTES);
lchan_set_marker(is_sid, lchan); /* DTXu */
}
break;
case GSM48_CMODE_SPEECH_AMR: /* AMR */
/* the first FN 0,8,17 or 1,9,18 defines that CMI is included
* in frame, the first FN 4,13,21 or 5,14,22 defines that CMR
* is included in frame.
*/
/* See comment in function rx_tchf_fn() */
switch (chan_state->amr_last_dtx) {
case AHS_ONSET:
case AHS_SID_FIRST_INH:
case AHS_SID_UPDATE_INH:
lchan_set_marker(false, lchan);
break;
}
fn_is_cmi = sched_tchh_ul_amr_cmi_map[bi->fn % 26];
/* See comment in function rx_tchf_fn() */
amr = sizeof(struct amr_hdr);
rc = gsm0503_tch_ahs_decode_dtx(tch_data + amr, BUFTAIL8(bursts_p),
!sched_tchh_ul_facch_map[bi->fn % 26],
!fn_is_cmi, chan_state->codec,
chan_state->codecs, &chan_state->ul_ft,
&chan_state->ul_cmr, &n_errors, &n_bits_total,
&chan_state->amr_last_dtx);
/* Tag all frames that are not regular AMR voice frames
as SUB-Frames */
if (chan_state->amr_last_dtx != AMR_OTHER) {
LOGL1SB(DL1P, LOGL_DEBUG, l1ts, bi,
"Received AMR DTX frame (rc=%d, BER %d/%d): %s\n",
rc, n_errors, n_bits_total,
gsm0503_amr_dtx_frame_name(chan_state->amr_last_dtx));
is_sub = 1;
}
/* See comment in function rx_tchf_fn() */
switch (chan_state->amr_last_dtx) {
case AHS_SID_FIRST_P1:
case AHS_SID_FIRST_P2:
case AHS_SID_UPDATE:
case AHS_SID_UPDATE_CN:
lchan_set_marker(true, lchan);
lchan->rtp_tx_marker = false;
break;
}
switch (chan_state->amr_last_dtx) {
case AHS_SID_FIRST_P1:
case AHS_SID_FIRST_P2:
case AHS_SID_UPDATE:
case AHS_SID_UPDATE_CN:
case AHS_SID_FIRST_INH:
case AHS_SID_UPDATE_INH:
meas_avg_mode = SCHED_MEAS_AVG_M_S6N2;
break;
case AHS_ONSET:
meas_avg_mode = SCHED_MEAS_AVG_M_S4N2;
break;
}
/* only good speech frames get rtp header */
if (rc != GSM_MACBLOCK_LEN && rc >= 4) {
if (chan_state->amr_last_dtx == AMR_OTHER) {
ft = chan_state->codec[chan_state->ul_ft];
} else {
/* SID frames will always get Frame Type Index 8 (AMR_SID) */
ft = AMR_SID;
}
rc = osmo_amr_rtp_enc(tch_data,
chan_state->codec[chan_state->ul_cmr],
ft, AMR_GOOD);
}
break;
/* CSD (TCH/H4.8): 6.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_6k0:
if (!sched_tchh_ul_csd_map[bi->fn % 26])
return 0; /* CSD: skip decoding attempt, need 2 more bursts */
/* FACCH/H does not steal TCH/H4.8 frames, but only disturbs some bits */
decode_hr_facch(l1ts, bi);
rc = gsm0503_tch_hr48_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
meas_avg_mode = SCHED_MEAS_AVG_M_S22N22;
break;
/* CSD (TCH/H2.4): 3.6 kbit/s radio interface rate */
case GSM48_CMODE_DATA_3k6:
if (!sched_tchh_ul_csd_map[bi->fn % 26])
return 0; /* CSD: skip decoding attempt, need 2 more bursts */
/* FACCH/H does not steal TCH/H2.4 frames, but only disturbs some bits */
decode_hr_facch(l1ts, bi);
rc = gsm0503_tch_hr24_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
meas_avg_mode = SCHED_MEAS_AVG_M_S22N22;
break;
default:
LOGL1SB(DL1P, LOGL_ERROR, l1ts, bi,
"TCH mode %u invalid, please fix!\n",
tch_mode);
return -EINVAL;
}
ber10k = compute_ber10k(n_bits_total, n_errors);
/* average measurements of the last N (depends on mode) bursts */
trx_sched_meas_avg(chan_state, &meas_avg, meas_avg_mode);
/* meas_avg.fn now contains TDMA frame number of the first burst */
fn_begin = meas_avg.fn;
if (tch_mode == GSM48_CMODE_SPEECH_AMR)
trx_loop_amr_input(chan_state, &meas_avg);
/* Check if the frame is bad */
if (rc < 4) {
LOGL1SB(DL1P, LOGL_NOTICE, l1ts, bi,
BAD_DATA_MSG_FMT "\n", BAD_DATA_MSG_ARGS);
rc = 0; /* this is how we signal BFI to l1sap */
} else if (rc == GSM_MACBLOCK_LEN) { /* FACCH */
chan_state->ul_ongoing_facch = 1;
/* In order to provide an even stream of measurement reports in *speech*
* mode, here we intentionally invalidate RSSI for FACCH, so that this
* report gets dropped in process_l1sap_meas_data(). The averaged results
* will be sent with the first (see below) and second (see above) BFIs. */
_sched_compose_ph_data_ind(l1ts, fn_begin, bi->chan,
&tch_data[amr], GSM_MACBLOCK_LEN,
ber10k,
tch_mode == GSM48_CMODE_SIGN ? meas_avg.rssi : 0,
meas_avg.toa256,
meas_avg.ci_cb,
PRES_INFO_UNKNOWN);
ber10k = 0;
bfi:
/* A FACCH/H frame replaces two speech frames, so we need to send two BFIs.
* One is sent here, another will be sent two bursts later (see above). */
rc = 0;
}
if (rsl_cmode == RSL_CMOD_SPD_SIGN)
return 0;
/* TCH or BFI */
return _sched_compose_tch_ind(l1ts, fn_begin, bi->chan,
&tch_data[0], rc,
ber10k,
meas_avg.rssi,
meas_avg.toa256,
meas_avg.ci_cb,
is_sub);
}
/* common section for generation of TCH bursts (TCH/H and TCH/F).
* FIXME: this function is over-complicated, refactor / get rid of it. */
extern void tch_dl_dequeue(struct l1sched_ts *l1ts, const struct trx_dl_burst_req *br,
struct msgb **msg_tch, struct msgb **msg_facch);
struct msgb *tch_dummy_msgb(size_t size, uint8_t pad);
/* obtain a to-be-transmitted TCH/H (Half Traffic Channel) burst */
int tx_tchh_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
{
struct l1sched_chan_state *chan_state = &l1ts->chan_state[br->chan];
uint8_t tch_mode = chan_state->tch_mode;
ubit_t *burst, *bursts_p = chan_state->dl_bursts;
uint8_t *mask = &chan_state->dl_mask;
struct msgb *msg_facch = NULL;
struct msgb *msg_tch = NULL;
struct msgb *msg = NULL;
/* send burst, if we already got a frame */
if (br->bid > 0) {
if ((*mask & 0x01) != 0x01)
return -ENOMSG;
goto send_burst;
}
*mask = *mask << 2;
/* BURST BYPASS */
/* shift buffer by 2 bursts for interleaving */
memmove(BUFPOS(bursts_p, 0), BUFPOS(bursts_p, 2), 20 * BPLEN);
memset(BUFPOS(bursts_p, 20), 0, 2 * BPLEN);
/* dequeue a TCH and/or a FACCH message to be transmitted */
tch_dl_dequeue(l1ts, br, &msg_tch, &msg_facch);
/* if we're sending 2 middle bursts of FACCH/H */
if (chan_state->dl_ongoing_facch) {
/* FACCH/H shall not be scheduled at wrong FNs */
OSMO_ASSERT(msg_facch == NULL);
msgb_free(msg_tch); /* drop 2nd speech frame */
chan_state->dl_ongoing_facch = 0;
goto send_burst;
}
/* no message at all, send a dummy L2 frame on FACCH */
if (msg_tch == NULL && msg_facch == NULL) {
int rc;
LOGL1SB(DL1P, LOGL_INFO, l1ts, br, "No TCH or FACCH prim for transmit.\n");
/* - If the channel mode is TCH/HS, transmit a dummy speech block
* with inverted CRC3, designed to induce a BFI condition in
* the MS receiver.
* - If the channel mode is TCH/AHS, transmit a dummy speech
* block with inverted CRC6, designed to induce a BFI
* condition in the MS receiver.
* - If the channel mode is one of the CSD modes, transmit an
* idle frame as described in 3GPP TS 44.021, sections 8.1.6
* and 10.2.3 (all data, status and E-bits set to binary '1').
* - In all other channel modes, transmit dummy FACCH
* like we always did before.
*/
switch (tch_mode) {
case GSM48_CMODE_DATA_6k0:
case GSM48_CMODE_DATA_3k6:
break; /* see below */
case GSM48_CMODE_SPEECH_V1:
rc = gsm0503_tch_hr_encode(BUFPOS(bursts_p, 0), NULL, 0);
if (rc == 0)
goto send_burst;
/* fall-through */
case GSM48_CMODE_SIGN:
default:
if (tch_mode == GSM48_CMODE_SPEECH_AMR) {
/* the first FN 4,13,21 or 5,14,22 defines that CMI is included
* in frame, the first FN 0,8,17 or 1,9,18 defines that CMR is
* included in frame. */
rc = gsm0503_tch_ahs_encode(BUFPOS(bursts_p, 0),
NULL, 0,
!sched_tchh_dl_amr_cmi_map[br->fn % 26],
chan_state->codec,
chan_state->codecs,
chan_state->dl_ft,
chan_state->dl_cmr);
if (rc == 0)
goto send_burst;
}
/* FACCH/H can only be scheduled at specific TDMA offset */
if (!sched_tchh_dl_facch_map[br->fn % 26]) {
/* FACCH/H is not allowed, send half-filled bursts with even numbered
* bits contaning 232 encoded bits of the previous L2 frame, and 232
* odd numbered bits all set to 0. */
goto send_burst;
}
/* TODO: use randomized padding */
msg_facch = tch_dummy_msgb(GSM_MACBLOCK_LEN, GSM_MACBLOCK_PADDING);
/* dummy LAPDm func=UI frame */
msg_facch->l2h[0] = 0x03;
msg_facch->l2h[1] = 0x03;
msg_facch->l2h[2] = 0x01;
break;
}
}
/* Unlike SACCH, FACCH has no dedicated slots on the multiframe layout.
* It's multiplexed together with TCH (speech or data) frames basically
* by replacing (stealing) their bits, either completely or partly. */
msg = (msg_facch != NULL) ? msg_facch : msg_tch;
if (msg == msg_facch) {
if (chan_state->rsl_cmode != RSL_CMOD_SPD_DATA)
chan_state->dl_ongoing_facch = 1;
chan_state->dl_facch_bursts = 6;
}
/* populate the buffer with bursts */
switch (tch_mode) {
case GSM48_CMODE_SIGN:
case GSM48_CMODE_SPEECH_V1:
gsm0503_tch_hr_encode(BUFPOS(bursts_p, 0), msg->l2h, msgb_l2len(msg));
break;
case GSM48_CMODE_SPEECH_AMR:
/* the first FN 4,13,21 or 5,14,22 defines that CMI is included
* in frame, the first FN 0,8,17 or 1,9,18 defines that CMR is
* included in frame. */
gsm0503_tch_ahs_encode(BUFPOS(bursts_p, 0),
msgb_l2(msg), msgb_l2len(msg),
!sched_tchh_dl_amr_cmi_map[br->fn % 26],
chan_state->codec,
chan_state->codecs,
chan_state->dl_ft,
chan_state->dl_cmr);
break;
/* CSD (TCH/H4.8): 6.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_6k0:
/* for half-rate CSD we run the encoder every 4th burst (like for TCH/F)
* because the interleaving is done as specified for the TCH/F9.6 */
if (sched_tchh_dl_csd_map[br->fn % 26]) {
if (msg_tch == NULL)
msg_tch = tch_dummy_msgb(4 * 60, 0x01);
gsm0503_tch_hr48_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_tch));
}
if (msg_facch != NULL)
gsm0503_tch_hr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_facch));
break;
/* CSD (TCH/H2.4): 3.6 kbit/s radio interface rate */
case GSM48_CMODE_DATA_3k6:
/* for half-rate CSD we run the encoder every 4th burst (like for TCH/F)
* because the interleaving is done as specified for the TCH/F9.6 */
if (sched_tchh_dl_csd_map[br->fn % 26]) {
if (msg_tch == NULL)
msg_tch = tch_dummy_msgb(4 * 36, 0x01);
gsm0503_tch_hr24_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_tch));
}
if (msg_facch != NULL)
gsm0503_tch_hr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_facch));
break;
default:
OSMO_ASSERT(0);
}
/* free messages */
msgb_free(msg_tch);
msgb_free(msg_facch);
send_burst:
/* compose burst */
burst = BUFPOS(bursts_p, br->bid);
memcpy(br->burst + 3, burst, 58);
memcpy(br->burst + 61, TRX_GMSK_NB_TSC(br), 26);
memcpy(br->burst + 87, burst + 58, 58);
br->burst_len = GSM_BURST_LEN;
if (chan_state->dl_facch_bursts > 0) {
chan_state->dl_facch_bursts--;
br->flags |= TRX_BR_F_FACCH;
}
*mask |= (1 << br->bid);
LOGL1SB(DL1P, LOGL_DEBUG, l1ts, br, "Transmitting burst=%u.\n", br->bid);
return 0;
}