From 00cb7efa2a120e9bea559ff3ee881f540c41fe15 Mon Sep 17 00:00:00 2001
From: Robert Schmidt <robert.schmidt@openairinterface.org>
Date: Wed, 24 Apr 2024 17:54:52 +0200
Subject: [PATCH] Use MeasurementTimingConfiguration to look up SSB ARFCN when
needed
MeasTimingConfig may not come with F1 Setup Request: some DUs send it
with the DU configuration update. Handle this gracefully by checking for
MTC before using it.
---
openair2/RRC/NR/rrc_gNB.c | 96 ++++++------------------------------
openair2/RRC/NR/rrc_gNB_du.c | 8 +--
2 files changed, 18 insertions(+), 86 deletions(-)
diff --git a/openair2/RRC/NR/rrc_gNB.c b/openair2/RRC/NR/rrc_gNB.c
index 52cb041aee5..ca848e749b8 100644
--- a/openair2/RRC/NR/rrc_gNB.c
+++ b/openair2/RRC/NR/rrc_gNB.c
@@ -186,79 +186,12 @@ static int get_ssb_scs(const f1ap_served_cell_info_t *cell_info)
return cell_info->mode == F1AP_MODE_TDD ? cell_info->tdd.tbw.scs : cell_info->fdd.dl_tbw.scs;
}
-static int get_dl_arfcn(const f1ap_served_cell_info_t *cell_info)
+static int get_ssb_arfcn(const nr_rrc_du_container_t *du)
{
- return cell_info->mode == F1AP_MODE_TDD ? cell_info->tdd.freqinfo.arfcn : cell_info->fdd.dl_freqinfo.arfcn;
-}
-
-static int get_dl_bw(const f1ap_served_cell_info_t *cell_info)
-{
- return cell_info->mode == F1AP_MODE_TDD ? cell_info->tdd.tbw.nrb : cell_info->fdd.dl_tbw.nrb;
-}
-
-static int get_ssb_arfcn(const f1ap_served_cell_info_t *cell_info, const NR_MIB_t *mib, const NR_SIB1_t *sib1)
-{
- DevAssert(cell_info != NULL && sib1 != NULL && mib != NULL);
- const NR_FrequencyInfoDL_SIB_t *freq_info = &sib1->servingCellConfigCommon->downlinkConfigCommon.frequencyInfoDL;
- AssertFatal(freq_info->scs_SpecificCarrierList.list.count == 1,
- "cannot handle more than one carrier, but has %d\n",
- freq_info->scs_SpecificCarrierList.list.count);
- AssertFatal(freq_info->scs_SpecificCarrierList.list.array[0]->offsetToCarrier == 0,
- "cannot handle offsetToCarrier != 0, but is %ld\n",
- freq_info->scs_SpecificCarrierList.list.array[0]->offsetToCarrier);
-
- long offsetToPointA = freq_info->offsetToPointA;
- long kssb = mib->ssb_SubcarrierOffset;
- uint32_t dl_arfcn = get_dl_arfcn(cell_info);
- int scs = get_ssb_scs(cell_info);
- int band = get_dl_band(cell_info);
- uint64_t freqpointa = from_nrarfcn(band, scs, dl_arfcn);
- uint64_t freqssb = 0;
- // 3GPP TS 38.211 sections 7.4.3.1 and 4.4.4.2
- // for FR1 offsetToPointA and k_SSB are expressed in terms of 15 kHz SCS
- // for FR2 offsetToPointA is expressed in terms of 60 kHz SCS and k_SSB expressed in terms of the subcarrier spacing provided
- // by the higher-layer parameter subCarrierSpacingCommon
- // FR1 includes frequency bands from 410 MHz (ARFCN 82000) to 7125 MHz (ARFCN 875000)
- // FR2 includes frequency bands from 24.25 GHz (ARFCN 2016667) to 71.0 GHz (ARFCN 2795832)
- if (dl_arfcn >= 82000 && dl_arfcn < 875000)
- freqssb = freqpointa + 15000 * (offsetToPointA * 12 + kssb) + 10ll * 12 * (1 << scs) * 15000;
- else if (dl_arfcn >= 2016667 && dl_arfcn < 2795832)
- freqssb = freqpointa + 60000 * offsetToPointA * 12 + (1 << scs) * 15000 * (kssb + 10ll * 12);
- else
- AssertFatal(false, "Invalid absoluteFrequencyPointA: %u\n", dl_arfcn);
-
- int band_size_hz = get_supported_bw_mhz(band > 256 ? FR2 : FR1, scs, get_dl_bw(cell_info)) * 1000 * 1000;
- uint32_t ssb_arfcn = to_nrarfcn(band, freqssb, scs, band_size_hz);
-
- LOG_D(NR_RRC,
- "freqpointa %ld Hz/%d offsetToPointA %ld kssb %ld scs %d band %d band_size_hz %d freqssb %ld Hz/%d\n",
- freqpointa,
- dl_arfcn,
- offsetToPointA,
- kssb,
- scs,
- band,
- band_size_hz,
- freqssb,
- ssb_arfcn);
-
- if (RC.nrmac) {
- // debugging: let's test this is the correct ARFCN
- // in the CU, we have no access to the SSB ARFCN and therefore need to
- // compute it ourselves. If we are running in monolithic, though, we have
- // access to the MAC structures and hence can read and compare to the
- // original SSB ARFCN. If the below creates problems, it can safely be
- // taken out (but the reestablishment will likely not work).
- const NR_ServingCellConfigCommon_t *scc = RC.nrmac[0]->common_channels[0].ServingCellConfigCommon;
- uint32_t scc_ssb_arfcn = *scc->downlinkConfigCommon->frequencyInfoDL->absoluteFrequencySSB;
- AssertFatal(ssb_arfcn == scc_ssb_arfcn,
- "mismatch of SCC SSB ARFCN original %u vs. computed %u! Note: you can remove this Assert, the gNB might run but UE "
- "connection instable\n",
- scc_ssb_arfcn,
- ssb_arfcn);
- }
-
- return ssb_arfcn;
+ DevAssert(du != NULL && du->mtc != NULL);
+ /* format has been verified when accepting MeasurementTimingConfiguration */
+ NR_MeasTimingList_t *mtlist = du->mtc->criticalExtensions.choice.c1->choice.measTimingConf->measTiming;
+ return mtlist->list.array[0]->frequencyAndTiming->carrierFreq;
}
///---------------------------------------------------------------------------------------------------------------///
@@ -582,13 +515,8 @@ static void rrc_gNB_generate_defaultRRCReconfiguration(const protocol_ctxt_t *co
f1ap_served_cell_info_t *cell_info = &du->setup_req->cell[0].info;
int scs = get_ssb_scs(cell_info);
int band = get_dl_band(cell_info);
- NR_MeasConfig_t *measconfig = NULL;
- if (du->mib != NULL && du->sib1 != NULL) {
- /* we cannot calculate the default measurement config without MIB&SIB1, as
- * we don't know the DU's SSB ARFCN */
- uint32_t ssb_arfcn = get_ssb_arfcn(cell_info, du->mib, du->sib1);
- measconfig = get_defaultMeasConfig(ssb_arfcn, band, scs);
- }
+ uint32_t ssb_arfcn = get_ssb_arfcn(du);
+ NR_MeasConfig_t *measconfig = get_defaultMeasConfig(ssb_arfcn, band, scs);
NR_SRB_ToAddModList_t *SRBs = createSRBlist(ue_p, false);
NR_DRB_ToAddModList_t *DRBs = createDRBlist(ue_p, false);
@@ -996,7 +924,7 @@ static void rrc_gNB_generate_RRCReestablishment(rrc_gNB_ue_context_t *ue_context
uint8_t xid = rrc_gNB_get_next_transaction_identifier(module_id);
ue_p->xids[xid] = RRC_REESTABLISH;
const f1ap_served_cell_info_t *cell_info = &du->setup_req->cell[0].info;
- uint32_t ssb_arfcn = get_ssb_arfcn(cell_info, du->mib, du->sib1);
+ uint32_t ssb_arfcn = get_ssb_arfcn(du);
int size = do_RRCReestablishment(ue_context_pP, buffer, RRC_BUF_SIZE, xid, cell_info->nr_pci, ssb_arfcn);
LOG_I(NR_RRC, "[RAPROC] UE %04x Logical Channel DL-DCCH, Generating NR_RRCReestablishment (bytes %d)\n", ue_p->rnti, size);
@@ -1286,6 +1214,14 @@ static void rrc_handle_RRCReestablishmentRequest(gNB_RRC_INST *rrc,
goto fallback_rrc_setup;
}
+ if (du->mtc == NULL) {
+ // some UEs don't send MeasurementTimingConfiguration, so we don't know the
+ // SSB ARFCN and can't do reestablishment. handle it gracefully by doing
+ // RRC setup procedure instead
+ LOG_E(NR_RRC, "no MeasurementTimingConfiguration for this cell, cannot perform reestablishment\n");
+ goto fallback_rrc_setup;
+ }
+
/* TODO: start timer in ITTI and drop UE if it does not come back */
// update with new RNTI, and update secondary UE association
diff --git a/openair2/RRC/NR/rrc_gNB_du.c b/openair2/RRC/NR/rrc_gNB_du.c
index a0d92a445a2..58b5dc6e7d1 100644
--- a/openair2/RRC/NR/rrc_gNB_du.c
+++ b/openair2/RRC/NR/rrc_gNB_du.c
@@ -166,14 +166,10 @@ void rrc_gNB_process_f1_setup_req(f1ap_setup_req_t *req, sctp_assoc_t assoc_id)
}
}
+ // MTC is mandatory, but some DUs don't send it in the F1 Setup Request, so
+ // "tolerate" this behavior, despite it being mandatory
NR_MeasurementTimingConfiguration_t *mtc =
extract_mtc(cell_info->measurement_timing_config, cell_info->measurement_timing_config_len);
- if (!mtc) {
- LOG_W(RRC, "cannot decode MeasurementTimingConfiguration of DU ID %ld, rejecting\n", req->gNB_DU_id);
- f1ap_setup_failure_t fail = {.cause = F1AP_CauseProtocol_semantic_error};
- rrc->mac_rrc.f1_setup_failure(assoc_id, &fail);
- return;
- }
const f1ap_gnb_du_system_info_t *sys_info = req->cell[0].sys_info;
NR_MIB_t *mib = NULL;
--
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