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dexter gerrit-no-reply at lists.osmocom.orgdexter has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/21185 )
Change subject: WIP: l1sap: add repeated uplink SACCH
......................................................................
WIP: 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, 55 insertions(+), 0 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/85/21185/1
diff --git a/include/osmo-bts/gsm_data.h b/include/osmo-bts/gsm_data.h
index ff6878d..4e925af 100644
--- a/include/osmo-bts/gsm_data.h
+++ b/include/osmo-bts/gsm_data.h
@@ -310,6 +310,7 @@
struct osmo_ecu_state *ecu_state;
struct abis_rsl_osmo_rep_acch_cap repeated_acch_capability;
+ bool repeated_ul_sacch_active;
};
static inline uint8_t lchan_get_ta(const struct gsm_lchan *lchan)
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 142a3c8..f63aff9 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -1080,6 +1080,8 @@
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_acch_capability.ul_sacch && 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)
diff --git a/src/osmo-bts-trx/sched_lchan_xcch.c b/src/osmo-bts-trx/sched_lchan_xcch.c
index b96bc0b..2e4993e 100644
--- a/src/osmo-bts-trx/sched_lchan_xcch.c
+++ b/src/osmo-bts-trx/sched_lchan_xcch.c
@@ -34,6 +34,24 @@
#include <sched_utils.h>
+/* Add two arrays of sbits */
+static void add_sbits(sbit_t *current, const sbit_t *previous)
+{
+ unsigned int i;
+ int result;
+ for (i = 0; i < 464; i++) {
+ result = *current + *previous;
+ if (result > 127)
+ result = 127;
+ else if (result < -127)
+ result = -127;
+ *current = (sbit_t) result;
+
+ 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 +67,11 @@
int n_bits_total = 0;
uint16_t ber10k;
int rc;
+ struct gsm_lchan *lchan = chan_state->lchan;
+ bool is_sacch = false;
+
+ if (chan == TRXC_SACCHTF || chan == TRXC_SACCHTH_0 || chan ==TRXC_SACCHTH_1)
+ is_sacch = true;
/* 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 +88,14 @@
return -ENOMEM;
}
+ /* UL-SACCH requires additional memory to keep a copy of each previous
+ * burst set. */
+ if (is_sacch && !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);
@@ -115,9 +146,29 @@
"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 (is_sacch && lchan->repeated_ul_sacch_active) {
+ 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);
+ l2_len = 0;
+ } else
+ l2_len = GSM_MACBLOCK_LEN;
+ }
} else
l2_len = GSM_MACBLOCK_LEN;
+ /* Keep a copy to ease decoding in the next repetition pass */
+ if (is_sacch && lchan->repeated_ul_sacch_active)
+ memcpy(chan_state->ul_bursts_prev, *bursts_p, 464);
+
ber10k = compute_ber10k(n_bits_total, n_errors);
return _sched_compose_ph_data_ind(l1t, bi->tn, *first_fn,
chan, l2, l2_len,
--
To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/21185
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I7e4cc33cc010866e41e3b594351a7f7bf93e08ac
Gerrit-Change-Number: 21185
Gerrit-PatchSet: 1
Gerrit-Owner: dexter <pmaier at sysmocom.de>
Gerrit-MessageType: newchange
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