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osmocom-bb/src/host/trxcon/src/sched_lchan_tchf.c

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/*
* OsmocomBB <-> SDR connection bridge
* TDMA scheduler: handlers for DL / UL bursts on logical channels
*
* (C) 2017-2022 by Vadim Yanitskiy <axilirator@gmail.com>
* (C) 2021-2024 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 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.
*
*/
#include <errno.h>
#include <string.h>
#include <stdint.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/bits.h>
#include <osmocom/gsm/protocol/gsm_04_08.h>
#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/gsm/gsm0502.h>
#include <osmocom/coding/gsm0503_coding.h>
#include <osmocom/coding/gsm0503_amr_dtx.h>
#include <osmocom/codec/codec.h>
#include <osmocom/bb/l1sched/l1sched.h>
#include <osmocom/bb/l1sched/logging.h>
/* Burst Payload LENgth (short alias) */
#define BPLEN GSM_NBITS_NB_GMSK_PAYLOAD
/* Burst BUFfer capacity (in BPLEN units) */
#define BUFMAX 24
/* Burst BUFfer position macros */
#define BUFPOS(buf, n) &buf[(n) * BPLEN]
#define BUFTAIL8(buf) BUFPOS(buf, (BUFMAX - 8))
/* 3GPP TS 45.009, table 3.2.1.3-{1,3}: AMR on Downlink TCH/F.
*
* +---+---+---+---+---+---+---+---+
* | a | b | c | d | e | f | g | h | Burst 'a' received first
* +---+---+---+---+---+---+---+---+
* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Speech/FACCH frame (bursts 'a' .. 'h')
*
* TDMA frame number of burst 'h' is always used as the table index. */
static const uint8_t sched_tchf_dl_amr_cmi_map[26] = {
[11] = 1, /* TCH/F: a=4 / h=11 */
[20] = 1, /* TCH/F: a=13 / h=20 */
[3] = 1, /* TCH/F: a=21 / h=3 (21+7=28, 25 is idle -> 29. 29%26=3) */
};
/* TDMA frame number of burst 'a' should be used as the table index. */
static const uint8_t sched_tchf_ul_amr_cmi_map[26] = {
[0] = 1, /* TCH/F: a=0 */
[8] = 1, /* TCH/F: a=8 */
[17] = 1, /* TCH/F: a=17 */
};
static int decode_fr_facch(struct l1sched_lchan_state *lchan)
{
uint8_t data[GSM_MACBLOCK_LEN];
int n_errors, n_bits_total;
int rc;
rc = gsm0503_tch_fr_facch_decode(&data[0], BUFTAIL8(lchan->rx_bursts),
&n_errors, &n_bits_total);
if (rc != GSM_MACBLOCK_LEN)
return rc;
/* calculate AVG of the measurements (FACCH/F takes 8 bursts) */
l1sched_lchan_meas_avg(lchan, 8);
l1sched_lchan_emit_data_ind(lchan, &data[0], GSM_MACBLOCK_LEN,
n_errors, n_bits_total, false);
return GSM_MACBLOCK_LEN;
}
int rx_tchf_fn(struct l1sched_lchan_state *lchan,
const struct l1sched_burst_ind *bi)
{
int n_errors = -1, n_bits_total = 0, rc;
sbit_t *bursts_p, *burst;
uint8_t tch_data[290];
size_t tch_data_len;
uint32_t *mask;
int amr = 0;
uint8_t ft;
/* Set up pointers */
mask = &lchan->rx_burst_mask;
bursts_p = lchan->rx_bursts;
LOGP_LCHAND(lchan, LOGL_DEBUG,
"Traffic received: fn=%u bid=%u\n", bi->fn, bi->bid);
if (bi->bid == 0) {
/* Shift the burst buffer by 4 bursts leftwards */
memmove(BUFPOS(bursts_p, 0), BUFPOS(bursts_p, 4), 20 * BPLEN);
memset(BUFPOS(bursts_p, 20), 0, 4 * BPLEN);
*mask = *mask << 4;
} else {
/* Align to the first burst of a block */
if (*mask == 0x00)
return 0;
}
/* Update mask */
*mask |= (1 << bi->bid);
/* Store the measurements */
l1sched_lchan_meas_push(lchan, bi);
/* Copy burst to end of buffer of 24 bursts */
burst = BUFPOS(bursts_p, 20 + bi->bid);
memcpy(burst, bi->burst + 3, 58);
memcpy(burst + 58, bi->burst + 87, 58);
/* Wait until complete set of bursts */
if (bi->bid != 3)
return 0;
/* Calculate AVG of the measurements */
l1sched_lchan_meas_avg(lchan, 8); // XXX
/* Check for complete set of bursts */
if ((*mask & 0xff) != 0xff) {
LOGP_LCHAND(lchan, LOGL_ERROR,
"Received incomplete (%s) traffic frame at fn=%u (%u/%u)\n",
l1sched_burst_mask2str(mask, 8), lchan->meas_avg.fn,
lchan->meas_avg.fn % lchan->ts->mf_layout->period,
lchan->ts->mf_layout->period);
/* NOTE: do not abort here, give it a try. Maybe we're lucky ;) */
}
/* TCH/F: speech and signalling frames are interleaved over 8 bursts, while
* CSD frames are interleaved over 22 bursts. Unless we're in CSD mode,
* decode only the last 8 bursts to avoid introducing additional delays. */
switch (lchan->tch_mode) {
case GSM48_CMODE_SIGN:
case GSM48_CMODE_SPEECH_V1: /* FR */
rc = gsm0503_tch_fr_decode(&tch_data[0], BUFTAIL8(bursts_p),
1, 0, &n_errors, &n_bits_total);
break;
case GSM48_CMODE_SPEECH_EFR: /* EFR */
rc = gsm0503_tch_fr_decode(&tch_data[0], BUFTAIL8(bursts_p),
1, 1, &n_errors, &n_bits_total);
break;
case GSM48_CMODE_SPEECH_AMR: /* AMR */
/* we store tch_data + 2 header bytes, the amr variable set to
* 2 will allow us to skip the first 2 bytes in case we did
* receive an FACCH frame instead of a voice frame (we do not
* know this before we actually decode the frame) */
amr = 2;
rc = gsm0503_tch_afs_decode_dtx(&tch_data[amr], BUFTAIL8(bursts_p),
!sched_tchf_dl_amr_cmi_map[bi->fn % 26],
lchan->amr.codec,
lchan->amr.codecs,
&lchan->amr.dl_ft,
&lchan->amr.dl_cmr,
&n_errors, &n_bits_total,
&lchan->amr.last_dtx);
/* only good speech frames get rtp header */
if (rc != GSM_MACBLOCK_LEN && rc >= 4) {
if (lchan->amr.last_dtx == AMR_OTHER) {
ft = lchan->amr.codec[lchan->amr.dl_ft];
} else {
/* SID frames will always get Frame Type Index 8 (AMR_SID) */
ft = AMR_SID;
}
rc = osmo_amr_rtp_enc(&tch_data[0],
lchan->amr.codec[lchan->amr.dl_cmr],
ft, AMR_GOOD);
if (rc < 0)
LOGP_LCHAND(lchan, LOGL_ERROR,
"osmo_amr_rtp_enc() returned rc=%d\n", rc);
}
break;
/* CSD (TCH/F14.4): 14.5 kbit/s radio interface rate */
case GSM48_CMODE_DATA_14k5:
/* FACCH/F does not steal TCH/F14.4 frames, but only disturbs some bits */
decode_fr_facch(lchan);
rc = gsm0503_tch_fr144_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
break;
/* CSD (TCH/F9.6): 12.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_12k0:
/* FACCH/F does not steal TCH/F9.6 frames, but only disturbs some bits */
decode_fr_facch(lchan);
rc = gsm0503_tch_fr96_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
break;
/* CSD (TCH/F4.8): 6.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_6k0:
/* FACCH/F does not steal TCH/F4.8 frames, but only disturbs some bits */
decode_fr_facch(lchan);
rc = gsm0503_tch_fr48_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
break;
/* CSD (TCH/F2.4): 3.6 kbit/s radio interface rate */
case GSM48_CMODE_DATA_3k6:
/* TCH/F2.4 employs the same interleaving as TCH/FS (8 bursts),
* so FACCH/F *does* steal TCH/F2.4 frames completely. */
if (decode_fr_facch(lchan) == GSM_MACBLOCK_LEN)
return 0; /* TODO: emit BFI? */
rc = gsm0503_tch_fr24_decode(&tch_data[0], BUFTAIL8(bursts_p),
&n_errors, &n_bits_total);
break;
default:
LOGP_LCHAND(lchan, LOGL_ERROR, "Invalid TCH mode: %u\n", lchan->tch_mode);
return -EINVAL;
}
/* Check decoding result */
if (rc < 4) {
LOGP_LCHAND(lchan, LOGL_ERROR,
"Received bad frame (rc=%d, ber=%d/%d) at fn=%u\n",
rc, n_errors, n_bits_total, lchan->meas_avg.fn);
/* Send BFI (DATA.ind without payload) */
tch_data_len = 0;
} else if (rc == GSM_MACBLOCK_LEN) {
/* FACCH received, forward it to the higher layers */
l1sched_lchan_emit_data_ind(lchan, &tch_data[amr], GSM_MACBLOCK_LEN,
n_errors, n_bits_total, false);
/* Send BFI (DATA.ind without payload) */
if (lchan->tch_mode == GSM48_CMODE_SIGN)
return 0;
tch_data_len = 0;
} else {
/* A good TCH frame received */
tch_data_len = rc;
}
/* Send a traffic frame to the higher layers */
return l1sched_lchan_emit_data_ind(lchan, &tch_data[0], tch_data_len,
n_errors, n_bits_total, true);
}
int tx_tchf_fn(struct l1sched_lchan_state *lchan,
struct l1sched_burst_req *br)
{
struct msgb *msg_facch, *msg_tch, *msg;
ubit_t *bursts_p, *burst;
const uint8_t *tsc;
uint32_t *mask;
int rc;
/* Set up pointers */
mask = &lchan->tx_burst_mask;
bursts_p = lchan->tx_bursts;
if (br->bid > 0) {
if ((*mask & 0x01) != 0x01)
return -ENOENT;
goto send_burst;
}
/* Shift the burst buffer by 4 bursts leftwards for interleaving */
memmove(BUFPOS(bursts_p, 0), BUFPOS(bursts_p, 4), 20 * BPLEN);
memset(BUFPOS(bursts_p, 20), 0, 4 * BPLEN);
*mask = *mask << 4;
/* dequeue a pair of TCH and FACCH frames */
msg_tch = l1sched_lchan_prim_dequeue_tch(lchan, false);
msg_facch = l1sched_lchan_prim_dequeue_tch(lchan, true);
/* prioritize FACCH over TCH */
msg = (msg_facch != NULL) ? msg_facch : msg_tch;
/* populate the buffer with bursts */
switch (lchan->tch_mode) {
case GSM48_CMODE_SIGN:
if (msg == NULL)
msg = l1sched_lchan_prim_dummy_lapdm(lchan);
/* fall-through */
case GSM48_CMODE_SPEECH_V1:
case GSM48_CMODE_SPEECH_EFR:
/* if msg == NULL, transmit a dummy speech block with inverted CRC3 */
rc = gsm0503_tch_fr_encode(BUFPOS(bursts_p, 0),
msg ? msgb_l2(msg) : NULL,
msg ? msgb_l2len(msg) : 0, 1);
/* confirm traffic sending (pass ownership of the msgb/prim) */
if (OSMO_LIKELY(rc == 0))
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
else /* unlikely: encoding failed, drop msgb/prim */
msgb_free(msg);
/* drop the other msgb/prim */
msgb_free((msg == msg_facch) ? msg_tch : msg_facch);
break;
case GSM48_CMODE_SPEECH_AMR:
{
bool amr_fn_is_cmr = !sched_tchf_ul_amr_cmi_map[br->fn % 26];
unsigned int offset = 0;
if (msg != NULL && msg != msg_facch) { /* TCH/AFS: speech */
if (!l1sched_lchan_amr_prim_is_valid(lchan, msg, amr_fn_is_cmr)) {
msgb_free(msg);
msg_tch = NULL;
msg = NULL;
}
/* pull the AMR header - sizeof(struct amr_hdr) */
offset = 2;
}
/* if msg == NULL, transmit a dummy speech block with inverted CRC6 */
rc = gsm0503_tch_afs_encode(BUFPOS(bursts_p, 0),
msg ? msgb_l2(msg) + offset : NULL,
msg ? msgb_l2len(msg) - offset : 0,
amr_fn_is_cmr,
lchan->amr.codec,
lchan->amr.codecs,
lchan->amr.ul_ft,
lchan->amr.ul_cmr);
/* confirm traffic sending (pass ownership of the msgb/prim) */
if (OSMO_LIKELY(rc == 0))
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
else /* unlikely: encoding failed, drop prim */
msgb_free(msg);
/* drop the other primitive */
msgb_free((msg == msg_facch) ? msg_tch : msg_facch);
break;
}
/* CSD (TCH/F14.4): 14.5 kbit/s radio interface rate */
case GSM48_CMODE_DATA_14k5:
if ((msg = msg_tch) != NULL) {
OSMO_ASSERT(msgb_l2len(msg) == 290);
gsm0503_tch_fr144_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
/* Confirm data sending (pass ownership of the msgb/prim) */
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
} else {
ubit_t idle[290];
memset(&idle[0], 0x01, sizeof(idle));
gsm0503_tch_fr144_encode(BUFPOS(bursts_p, 0), &idle[0]);
}
if ((msg = msg_facch) != NULL) {
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
/* Confirm FACCH sending (pass ownership of the msgb/prim) */
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
}
break;
/* CSD (TCH/F9.6): 12.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_12k0:
if ((msg = msg_tch) != NULL) {
OSMO_ASSERT(msgb_l2len(msg) == 4 * 60);
gsm0503_tch_fr96_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
/* Confirm data sending (pass ownership of the msgb/prim) */
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
} else {
ubit_t idle[4 * 60];
memset(&idle[0], 0x01, sizeof(idle));
gsm0503_tch_fr96_encode(BUFPOS(bursts_p, 0), &idle[0]);
}
if ((msg = msg_facch) != NULL) {
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
/* Confirm FACCH sending (pass ownership of the msgb/prim) */
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
}
break;
/* CSD (TCH/F4.8): 6.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_6k0:
if ((msg = msg_tch) != NULL) {
OSMO_ASSERT(msgb_l2len(msg) == 2 * 60);
gsm0503_tch_fr48_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
/* Confirm data sending (pass ownership of the msgb/prim) */
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
} else {
ubit_t idle[2 * 60];
memset(&idle[0], 0x01, sizeof(idle));
gsm0503_tch_fr48_encode(BUFPOS(bursts_p, 0), &idle[0]);
}
if ((msg = msg_facch) != NULL) {
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
/* Confirm FACCH sending (pass ownership of the msgb/prim) */
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
}
break;
/* CSD (TCH/F2.4): 3.6 kbit/s radio interface rate */
case GSM48_CMODE_DATA_3k6:
if ((msg = msg_facch) != NULL) {
/* FACCH/F does steal a TCH/F2.4 frame completely */
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
msgb_free(msg_tch);
} else if ((msg = msg_tch) != NULL) {
OSMO_ASSERT(msgb_l2len(msg) == 2 * 36);
gsm0503_tch_fr24_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
} else {
ubit_t idle[2 * 36];
memset(&idle[0], 0x01, sizeof(idle));
gsm0503_tch_fr24_encode(BUFPOS(bursts_p, 0), &idle[0]);
}
break;
default:
LOGP_LCHAND(lchan, LOGL_ERROR,
"TCH mode %s is unknown or not supported\n",
gsm48_chan_mode_name(lchan->tch_mode));
msgb_free(msg_facch);
msgb_free(msg_tch);
break;
}
send_burst:
/* Determine which burst should be sent */
burst = BUFPOS(bursts_p, br->bid);
/* Update mask */
*mask |= (1 << br->bid);
/* Choose proper TSC */
tsc = l1sched_nb_training_bits[lchan->tsc];
/* Compose a new burst */
memset(br->burst, 0, 3); /* TB */
memcpy(br->burst + 3, burst, 58); /* Payload 1/2 */
memcpy(br->burst + 61, tsc, 26); /* TSC */
memcpy(br->burst + 87, burst + 58, 58); /* Payload 2/2 */
memset(br->burst + 145, 0, 3); /* TB */
br->burst_len = GSM_NBITS_NB_GMSK_BURST;
LOGP_LCHAND(lchan, LOGL_DEBUG, "Scheduled fn=%u burst=%u\n", br->fn, br->bid);
return 0;
}
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