laforge has submitted this change. (
https://gerrit.osmocom.org/c/osmo-bts/+/21185 )
Change subject: l1sap: add repeated uplink SACCH
......................................................................
l1sap: add repeated uplink SACCH
3GPP TS 44.006, section 11 describes a method how the uplink
SACCH transmission can be repeated to increase transmission
reliability.
Change-Id: I7e4cc33cc010866e41e3b594351a7f7bf93e08ac
Related: OS#4795, SYS#5114
---
M include/osmo-bts/gsm_data.h
M include/osmo-bts/scheduler.h
M src/common/l1sap.c
M src/osmo-bts-trx/sched_lchan_xcch.c
4 files changed, 80 insertions(+), 0 deletions(-)
Approvals:
Jenkins Builder: Verified
fixeria: Looks good to me, but someone else must approve
Hoernchen: Looks good to me, but someone else must approve
laforge: Looks good to me, approved
diff --git a/include/osmo-bts/gsm_data.h b/include/osmo-bts/gsm_data.h
index b5b616e..64102f5 100644
--- a/include/osmo-bts/gsm_data.h
+++ b/include/osmo-bts/gsm_data.h
@@ -326,6 +326,7 @@
struct abis_rsl_osmo_rep_acch_cap repeated_acch_capability;
bool repeated_dl_facch_active;
+ bool repeated_ul_sacch_active;
/* Message buffer to store DL-SACCH repeation candidate */
struct msgb *rep_sacch;
diff --git a/include/osmo-bts/scheduler.h b/include/osmo-bts/scheduler.h
index 6bb0b9b..6f05756 100644
--- a/include/osmo-bts/scheduler.h
+++ b/include/osmo-bts/scheduler.h
@@ -87,6 +87,7 @@
ubit_t *dl_bursts; /* burst buffer for TX */
enum trx_burst_type dl_burst_type; /* GMSK or 8PSK burst type */
sbit_t *ul_bursts; /* burst buffer for RX */
+ sbit_t *ul_bursts_prev;/* previous burst buffer for RX
(repeated SACCH) */
uint32_t ul_first_fn; /* fn of first burst */
uint8_t ul_mask; /* mask of received bursts */
diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index 05adbb1..1785e66 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -1131,6 +1131,8 @@
p = msgb_put(msg, GSM_MACBLOCK_LEN);
/* L1-header, if not set/modified by layer 1 */
p[0] = lchan->ms_power_ctrl.current;
+ if (lchan->repeated_ul_sacch_active)
+ p[0] |= 0x40; /* See also: 3GPP TS 44.004,
section 7.1 */
p[1] = lchan->rqd_ta;
le = &lchan->lapdm_ch.lapdm_acch;
if (lchan->repeated_acch_capability.dl_sacch)
@@ -1394,6 +1396,34 @@
return check_for_first_ciphrd(lchan, data, len);
}
+/* Decide if repeated UL-SACCH should be applied or not. If the BER level, of
+ * the received SACCH blocks rises above a certain threshold UL-SACCH
+ * repetition is enabled */
+static void repeated_ul_sacch_active_decision(struct gsm_lchan *lchan,
+ uint16_t ber10k)
+{
+ uint16_t upper = 0;
+ uint16_t lower = 0;
+
+ if (!lchan->repeated_acch_capability.ul_sacch)
+ return;
+
+ /* convert from RXQUAL value to ber10k vale,
+ * see also GSM 05.08, section 8.2.4 */
+ static const uint16_t ber10k_by_rxqual_upper[] =
+ { 0, 26, 51, 100, 190, 380, 760, 1500 };
+ static const uint16_t ber10k_by_rxqual_lower[] =
+ { 0, 10, 10, 30, 64, 130, 270, 540 };
+ upper = ber10k_by_rxqual_upper[lchan->repeated_acch_capability.rxqual];
+ lower = ber10k_by_rxqual_lower[lchan->repeated_acch_capability.rxqual];
+
+ /* If upper/rxqual == 0, then repeated UL-SACCH is always on */
+ if (ber10k >= upper)
+ lchan->repeated_ul_sacch_active = true;
+ else if (ber10k <= lower)
+ lchan->repeated_ul_sacch_active = false;
+}
+
/* DATA received from bts model */
static int l1sap_ph_data_ind(struct gsm_bts_trx *trx,
struct osmo_phsap_prim *l1sap, struct ph_data_param *data_ind)
@@ -1472,6 +1502,9 @@
return 0;
}
+ if (L1SAP_IS_LINK_SACCH(link_id))
+ repeated_ul_sacch_active_decision(lchan, data_ind->ber10k);
+
/* bad frame */
if (len == 0) {
if (L1SAP_IS_LINK_SACCH(link_id)) {
diff --git a/src/osmo-bts-trx/sched_lchan_xcch.c
b/src/osmo-bts-trx/sched_lchan_xcch.c
index b96bc0b..90f481a 100644
--- a/src/osmo-bts-trx/sched_lchan_xcch.c
+++ b/src/osmo-bts-trx/sched_lchan_xcch.c
@@ -34,6 +34,17 @@
#include <sched_utils.h>
+/* Add two arrays of sbits */
+static void add_sbits(sbit_t * current, const sbit_t * previous)
+{
+ unsigned int i;
+ for (i = 0; i < 464; i++) {
+ *current = (*current) / 2 + (*previous) / 2;
+ current++;
+ previous++;
+ }
+}
+
/*! \brief a single (SDCCH/SACCH) burst was received by the PHY, process it */
int rx_data_fn(struct l1sched_trx *l1t, enum trx_chan_type chan,
uint8_t bid, const struct trx_ul_burst_ind *bi)
@@ -49,6 +60,8 @@
int n_bits_total = 0;
uint16_t ber10k;
int rc;
+ struct gsm_lchan *lchan = chan_state->lchan;
+ bool rep_sacch = L1SAP_IS_LINK_SACCH(trx_chan_desc[chan].link_id) &&
lchan->repeated_ul_sacch_active;
/* 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. */
@@ -65,6 +78,14 @@
return -ENOMEM;
}
+ /* UL-SACCH requires additional memory to keep a copy of each previous
+ * burst set. */
+ if (L1SAP_IS_LINK_SACCH(trx_chan_desc[chan].link_id) &&
!chan_state->ul_bursts_prev) {
+ chan_state->ul_bursts_prev = talloc_zero_size(tall_bts_ctx,
464);
+ if (!chan_state->ul_bursts_prev)
+ return -ENOMEM;
+ }
+
/* clear burst & store frame number of first burst */
if (bid == 0) {
memset(*bursts_p, 0, 464);
@@ -115,10 +136,34 @@
"Received bad data (%u/%u)\n",
bi->fn % l1ts->mf_period, l1ts->mf_period);
l2_len = 0;
+
+ /* When SACCH Repetition is active, we may try to decode the
+ * current SACCH block by including the information from the
+ * information from the previous SACCH block. See also:
+ * 3GPP TS 44.006, section 11.2 */
+ if (rep_sacch) {
+ add_sbits(*bursts_p, chan_state->ul_bursts_prev);
+ rc = gsm0503_xcch_decode(l2, *bursts_p, &n_errors,
&n_bits_total);
+ if (rc) {
+ LOGL1S(DL1P, LOGL_NOTICE, l1t, bi->tn, chan,
bi->fn,
+ "Combining current SACCH block with
previous SACCH block also yields bad data (%u/%u)\n",
+ bi->fn % l1ts->mf_period,
l1ts->mf_period);
+ } else {
+ LOGL1S(DL1P, LOGL_DEBUG, l1t, bi->tn, chan,
bi->fn,
+ "Combining current SACCH block with
previous SACCH block yields good data (%u/%u)\n",
+ bi->fn % l1ts->mf_period,
l1ts->mf_period);
+ l2_len = GSM_MACBLOCK_LEN;
+ }
+ }
} else
l2_len = GSM_MACBLOCK_LEN;
ber10k = compute_ber10k(n_bits_total, n_errors);
+
+ /* Keep a copy to ease decoding in the next repetition pass */
+ if (rep_sacch)
+ memcpy(chan_state->ul_bursts_prev, *bursts_p, 464);
+
return _sched_compose_ph_data_ind(l1t, bi->tn, *first_fn,
chan, l2, l2_len,
meas_avg.rssi, meas_avg.toa256,
--
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I7e4cc33cc010866e41e3b594351a7f7bf93e08ac
Gerrit-Change-Number: 21185
Gerrit-PatchSet: 5
Gerrit-Owner: dexter <pma...@sysmocom.de>
Gerrit-Reviewer: Hoernchen <ew...@sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria <vyanits...@sysmocom.de>
Gerrit-Reviewer: laforge <lafo...@osmocom.org>
Gerrit-Reviewer: tnt <t...@246tnt.com>
Gerrit-MessageType: merged
