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osmo-bts-trx: implement FACCH/[FH] support for CSD 

The FACCH/[FH] coding rules are specified in 3GPP TS 45.003, sections
4.2 and 4.3.  The key difference is that unlike with speech channels,
FACCH does not replace data frames completely, but disturb a fixed
amount of bits fom them.  This is why we need to use separate
gsm0503_tch_[fh]r_facch_{en,de}code() API for data channels.

Change-Id: I4c6736e84c271240d457998de688c0baf59fe578
Depends: libosmocore.git I0c7a9c180dcafe64e6aebe53518d3d11e1f29886
Related: OS#1572
This commit is contained in:
Vadim Yanitskiy 2023-05-30 16:48:37 +07:00
parent 95407f3f63
commit deef79ffae
2 changed files with 143 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

126
src/osmo-bts-trx/sched_lchan_tchf.c
View File

@ -69,6 +69,34 @@ static const uint8_t sched_tchf_dl_amr_cmi_map[26] = {
extern const uint8_t sched_tchh_dl_amr_cmi_map[26];
static int decode_fr_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_fr_facch_decode(&data[0], BUFTAIL8(bursts_p),
&n_errors, &n_bits_total);
if (rc != GSM_MACBLOCK_LEN)
return rc;
/* average measurements of the last 8 bursts, obtain TDMA Fn of the first burst */
trx_sched_meas_avg(chan_state, &meas_avg, SCHED_MEAS_AVG_M_S8N8);
_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;
}
/*! \brief a single TCH/F burst was received by the PHY, process it */
int rx_tchf_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
{
@ -224,12 +252,16 @@ int rx_tchf_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
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(l1ts, bi);
rc = gsm0503_tch_fr96_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
meas_avg_mode = SCHED_MEAS_AVG_M_S24N22;
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(l1ts, bi);
rc = gsm0503_tch_fr48_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
meas_avg_mode = SCHED_MEAS_AVG_M_S24N22;
@ -237,7 +269,8 @@ int rx_tchf_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
#if 0
/* TODO: 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) */
/* TCH/F2.4 employs the same interleaving as TCH/FS (8 bursts),
* so FACCH/F *does* steal TCH/F2.4 frames completely. */
rc = gsm0503_tch_fr24_decode(&tch_data[0], BUFTAIL8(bursts_p),
&n_errors, &n_bits_total);
meas_avg_mode = SCHED_MEAS_AVG_M_S8N8;
@ -245,6 +278,8 @@ int rx_tchf_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
#endif
/* 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(l1ts, bi);
rc = gsm0503_tch_fr144_decode(&tch_data[0], BUFPOS(bursts_p, 0),
&n_errors, &n_bits_total);
meas_avg_mode = SCHED_MEAS_AVG_M_S24N22;
@ -316,9 +351,10 @@ int rx_tchf_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
/* common section for generation of TCH bursts (TCH/H and TCH/F).
* FIXME: this function is over-complicated, refactor / get rid of it. */
struct msgb *tch_dl_dequeue(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
void tch_dl_dequeue(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br,
struct msgb **msg_tch, struct msgb **msg_facch)
{
struct msgb *msg1, *msg2, *msg_tch = NULL, *msg_facch = NULL;
struct msgb *msg1, *msg2;
struct l1sched_chan_state *chan_state = &l1ts->chan_state[br->chan];
uint8_t rsl_cmode = chan_state->rsl_cmode;
uint8_t tch_mode = chan_state->tch_mode;
@ -330,50 +366,39 @@ struct msgb *tch_dl_dequeue(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br
if (msg1) {
l1sap = msgb_l1sap_prim(msg1);
if (l1sap->oph.primitive == PRIM_TCH) {
msg_tch = msg1;
*msg_tch = msg1;
if (msg2) {
l1sap = msgb_l1sap_prim(msg2);
if (l1sap->oph.primitive == PRIM_TCH) {
LOGL1SB(DL1P, LOGL_FATAL, l1ts, br, "TCH twice, please FIX!\n");
msgb_free(msg2);
} else
msg_facch = msg2;
*msg_facch = msg2;
}
} else {
msg_facch = msg1;
*msg_facch = msg1;
if (msg2) {
l1sap = msgb_l1sap_prim(msg2);
if (l1sap->oph.primitive != PRIM_TCH) {
LOGL1SB(DL1P, LOGL_FATAL, l1ts, br, "FACCH twice, please FIX!\n");
msgb_free(msg2);
} else
msg_tch = msg2;
*msg_tch = msg2;
}
}
}
/* check validity of message */
if (msg_facch && msgb_l2len(msg_facch) != GSM_MACBLOCK_LEN) {
if (*msg_facch != NULL && msgb_l2len(*msg_facch) != GSM_MACBLOCK_LEN) {
LOGL1SB(DL1P, LOGL_FATAL, l1ts, br, "Prim has odd len=%u != %u\n",
msgb_l2len(msg_facch), GSM_MACBLOCK_LEN);
msgb_l2len(*msg_facch), GSM_MACBLOCK_LEN);
/* free message */
msgb_free(msg_facch);
msg_facch = NULL;
}
/* prioritize FACCH over speech */
if (msg_facch) {
/* 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) them. This is common for both TCH/F and
* TCH/H, with the only difference that FACCH/H steals two TCH frames
* (not just one) due to a longer interleaving period. */
msgb_free(msg_tch);
return msg_facch;
msgb_free(*msg_facch);
*msg_facch = NULL;
}
/* check validity of message, get AMR ft and cmr */
if (msg_tch) {
if (*msg_tch != NULL) {
int len;
uint8_t cmr_codec;
int ft, i;
@ -401,7 +426,7 @@ struct msgb *tch_dl_dequeue(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br
len = GSM_EFR_BYTES;
break;
case GSM48_CMODE_SPEECH_AMR: /* AMR */
len = osmo_amr_rtp_dec(msg_tch->l2h, msgb_l2len(msg_tch),
len = osmo_amr_rtp_dec(msgb_l2((*msg_tch)), msgb_l2len(*msg_tch),
&cmr_codec, &cmi, &ft_codec,
&bfi, &sti);
if (len < 0) {
@ -433,7 +458,7 @@ struct msgb *tch_dl_dequeue(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br
goto free_bad_msg;
}
/* pull the AMR header, it's not being sent over Um */
msg_tch->l2h += sizeof(struct amr_hdr);
(*msg_tch)->l2h += sizeof(struct amr_hdr);
len -= sizeof(struct amr_hdr);
break;
case GSM48_CMODE_DATA_14k5: /* TCH/F14.4 */
@ -464,18 +489,16 @@ inval_mode2:
LOGL1SB(DL1P, LOGL_ERROR, l1ts, br, "TCH mode invalid, please fix!\n");
goto free_bad_msg;
}
if (msgb_l2len(msg_tch) != len) {
if (msgb_l2len(*msg_tch) != len) {
LOGL1SB(DL1P, LOGL_ERROR, l1ts, br, "Cannot send payload with "
"invalid length! (expecting %d, received %d)\n",
len, msgb_l2len(msg_tch));
len, msgb_l2len(*msg_tch));
free_bad_msg:
/* free message */
msgb_free(msg_tch);
msg_tch = NULL;
msgb_free(*msg_tch);
*msg_tch = NULL;
}
}
return msg_tch;
}
/* obtain a to-be-transmitted TCH/F (Full Traffic Channel) burst */
@ -485,7 +508,9 @@ int tx_tchf_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
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;
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) {
@ -502,11 +527,9 @@ int tx_tchf_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
memmove(BUFPOS(bursts_p, 0), BUFPOS(bursts_p, 4), 20 * BPLEN);
memset(BUFPOS(bursts_p, 20), 0, 4 * BPLEN);
/* dequeue a message to be transmitted */
msg = tch_dl_dequeue(l1ts, br);
/* no message at all, send a dummy L2 frame on FACCH */
if (msg == NULL) {
/* dequeue a TCH and/or a FACCH message to be transmitted */
tch_dl_dequeue(l1ts, br, &msg_tch, &msg_facch);
if (msg_tch == NULL && msg_facch == NULL) {
static const uint8_t dummy[GSM_MACBLOCK_LEN] = {
0x03, 0x03, 0x01, /* TODO: use randomized padding */
0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,
@ -538,7 +561,11 @@ int tx_tchf_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
goto send_burst;
}
if (msgb_l2len(msg) == GSM_MACBLOCK_LEN)
/* 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)
chan_state->dl_facch_bursts = 8;
/* populate the buffer with bursts */
@ -562,28 +589,39 @@ int tx_tchf_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
break;
/* CSD (TCH/F9.6): 12.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_12k0:
gsm0503_tch_fr96_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
gsm0503_tch_fr96_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_tch));
if (msg_facch != NULL)
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_facch));
break;
/* CSD (TCH/F4.8): 6.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_6k0:
gsm0503_tch_fr48_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
gsm0503_tch_fr48_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_tch));
if (msg_facch != NULL)
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_facch));
break;
#if 0
/* TODO: CSD (TCH/F2.4): 3.6 kbit/s radio interface rate */
case GSM48_CMODE_DATA_3k6:
gsm0503_tch_fr24_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
/* FACCH/F does steal a TCH/F2.4 frame completely */
if (msg == msg_facch)
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_facch));
else
gsm0503_tch_fr24_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_tch));
break;
#endif
/* CSD (TCH/F14.4): 14.5 kbit/s radio interface rate */
case GSM48_CMODE_DATA_14k5:
gsm0503_tch_fr144_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
gsm0503_tch_fr144_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_tch));
if (msg_facch != NULL)
gsm0503_tch_fr_facch_encode(BUFPOS(bursts_p, 0), msgb_l2(msg_facch));
break;
default:
OSMO_ASSERT(0);
}
/* free message */
msgb_free(msg);
/* free messages */
msgb_free(msg_tch);
msgb_free(msg_facch);
send_burst:
/* compose burst */

74
src/osmo-bts-trx/sched_lchan_tchh.c
View File

@ -126,6 +126,34 @@ static const uint8_t sched_tchh_dl_csd_map[26] = {
[18] = 1, /* TCH/H(1): B2(18 ... 11) */
};
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;
}
/*! \brief a single TCH/H burst was received by the PHY, process it */
int rx_tchh_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
{
@ -295,6 +323,8 @@ int rx_tchh_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
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/F 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;
@ -303,6 +333,8 @@ int rx_tchh_fn(struct l1sched_ts *l1ts, const struct trx_ul_burst_ind *bi)
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/F 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;
@ -375,7 +407,8 @@ bfi:
/* common section for generation of TCH bursts (TCH/H and TCH/F).
* FIXME: this function is over-complicated, refactor / get rid of it. */
extern struct msgb *tch_dl_dequeue(struct l1sched_ts *l1ts, const struct trx_dl_burst_req *br);
extern void tch_dl_dequeue(struct l1sched_ts *l1ts, const struct trx_dl_burst_req *br,
struct msgb **msg_tch, struct msgb **msg_facch);
/* 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)
@ -384,7 +417,9 @@ int tx_tchh_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
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;
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) {
@ -407,18 +442,20 @@ int tx_tchh_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
goto send_burst;
}
/* dequeue a message to be transmitted */
msg = tch_dl_dequeue(l1ts, br);
/* 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) {
msgb_free(msg); /* drop 2nd speech frame */
/* 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 == NULL) {
if (msg_tch == NULL && msg_facch == NULL) {
static const uint8_t dummy[GSM_MACBLOCK_LEN] = {
0x03, 0x03, 0x01, /* TODO: use randomized padding */
0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,
@ -451,13 +488,19 @@ int tx_tchh_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
}
gsm0503_tch_hr_encode(BUFPOS(bursts_p, 0), dummy, sizeof(dummy));
chan_state->dl_ongoing_facch = 1;
if (chan_state->rsl_cmode != RSL_CMOD_SPD_DATA)
chan_state->dl_ongoing_facch = 1;
chan_state->dl_facch_bursts = 6;
goto send_burst;
}
if (msgb_l2len(msg) == GSM_MACBLOCK_LEN) {
chan_state->dl_ongoing_facch = 1; /* first of two TCH frames */
/* 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;
}
@ -481,18 +524,23 @@ int tx_tchh_fn(struct l1sched_ts *l1ts, struct trx_dl_burst_req *br)
break;
/* CSD (TCH/H4.8): 6.0 kbit/s radio interface rate */
case GSM48_CMODE_DATA_6k0:
gsm0503_tch_hr48_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
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:
gsm0503_tch_hr24_encode(BUFPOS(bursts_p, 0), msgb_l2(msg));
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 message */
msgb_free(msg);
/* free messages */
msgb_free(msg_tch);
msgb_free(msg_facch);
send_burst:
/* compose burst */