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sched-nr: fix sched not allocating CCCH at low MCS

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Signed-off-by: Carlo Galiotto <carlo@srs.io>
master
Carlo Galiotto 3 years ago committed by carlo-gal
parent 65dae777b1
commit 2b3158536a
3 changed files with 71 additions and 27 deletions
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6
srsgnb/hdr/stack/mac/sched_nr_ue.h
Unescape Escape View File

@ -61,7 +61,7 @@ public:
struct pdu_builder {
pdu_builder() = default;
explicit pdu_builder(uint32_t cc_, ue_buffer_manager& parent_) : cc(cc_), parent(&parent_) {}
void alloc_subpdus(uint32_t rem_bytes, sched_nr_interface::dl_pdu_t& pdu);
bool alloc_subpdus(uint32_t rem_bytes, sched_nr_interface::dl_pdu_t& pdu);
private:
uint32_t cc = SRSRAN_MAX_CARRIERS;
@ -180,9 +180,9 @@ public:
ul_harq_proc* find_empty_ul_harq() { return ue->harq_ent.find_empty_ul_harq(); }
/// Build PDU with MAC CEs and MAC SDUs
void build_pdu(uint32_t rem_bytes, sched_nr_interface::dl_pdu_t& pdu)
bool build_pdu(uint32_t rem_bytes, sched_nr_interface::dl_pdu_t& pdu)
{
ue->pdu_builder.alloc_subpdus(rem_bytes, pdu);
return ue->pdu_builder.alloc_subpdus(rem_bytes, pdu);
}
/// Channel Information Getters

62
srsgnb/src/stack/mac/sched_nr_grant_allocator.cc
Unescape Escape View File

@ -353,33 +353,51 @@ alloc_result bwp_slot_allocator::alloc_pdsch(slot_ue& ue, uint32_t ss_id, const
slot_cfg.idx = ue.pdsch_slot.to_uint();
// Value 0.95 is from TS 38.214 v15.14.00, Section 5.1.3, page 17
const static float max_R = 0.95;
double R_prime = max_R;
double R_prime;
const static int min_MCS_ccch = 4;
// The purpose of the external loop is to reset the MCS to a min value of 4 if there are not enough PRBs to
// allocate the SRB0/CCCH. This loop only affects the low MCS values
while (true) {
// Generate PDSCH
bool success = ue->phy().get_pdsch_cfg(slot_cfg, pdcch.dci, pdsch.sch);
srsran_assert(success, "Error converting DCI to grant");
if (ue.h_dl->nof_retx() != 0) {
srsran_assert(pdsch.sch.grant.tb[0].tbs == (int)ue.h_dl->tbs(), "The TBS did not remain constant in retx");
// The purpose of the internal loop is to decrease the MCS if the effective coderate is too high. This loop
// only affects the high MCS values
while (true) {
// Generate PDSCH
bool success = ue->phy().get_pdsch_cfg(slot_cfg, pdcch.dci, pdsch.sch);
srsran_assert(success, "Error converting DCI to grant");
if (ue.h_dl->nof_retx() != 0) {
srsran_assert(pdsch.sch.grant.tb[0].tbs == (int)ue.h_dl->tbs(), "The TBS did not remain constant in retx");
}
R_prime = pdsch.sch.grant.tb[0].R_prime;
if (ue.h_dl->nof_retx() > 0 or R_prime < max_R or mcs <= 0) {
break;
}
// Decrease MCS if first tx and rate is too high
mcs--;
pdcch.dci.mcs = mcs;
}
R_prime = pdsch.sch.grant.tb[0].R_prime;
if (ue.h_dl->nof_retx() > 0 or R_prime < max_R or mcs <= 0) {
if (R_prime >= max_R and mcs == 0) {
logger.warning("Couldn't find mcs that leads to R<0.95");
}
ue.h_dl->set_mcs(mcs);
ue.h_dl->set_tbs(pdsch.sch.grant.tb[0].tbs); // set HARQ TBS
pdsch.sch.grant.tb[0].softbuffer.tx = ue.h_dl->get_softbuffer().get();
pdsch.data[0] = ue.h_dl->get_tx_pdu()->get();
// Select scheduled LCIDs and update UE buffer state
bwp_pdsch_slot.dl.data.emplace_back();
// NOTE: ue.h_dl->tbs() has to be converted from bits to bytes
bool segmented_ccch_pdu = not ue.build_pdu(ue.h_dl->tbs() / 8, bwp_pdsch_slot.dl.data.back());
if (segmented_ccch_pdu) {
// In case of segmented PDU for CCCH, set minimum MCS to 4 and re-run the outer while loop
bwp_pdsch_slot.dl.data.pop_back();
mcs = min_MCS_ccch;
pdcch.dci.mcs = mcs;
logger.warning(
"SCHED: MCS increased to min value %d to allocate SRB0/CCCH for rnti=0x%x", min_MCS_ccch, ue->rnti);
} else {
break;
}
// Decrease MCS if first tx and rate is too high
mcs--;
pdcch.dci.mcs = mcs;
}
if (R_prime >= max_R and mcs == 0) {
logger.warning("Couldn't find mcs that leads to R<0.95");
}
ue.h_dl->set_mcs(mcs);
ue.h_dl->set_tbs(pdsch.sch.grant.tb[0].tbs); // set HARQ TBS
pdsch.sch.grant.tb[0].softbuffer.tx = ue.h_dl->get_softbuffer().get();
pdsch.data[0] = ue.h_dl->get_tx_pdu()->get();
// Select scheduled LCIDs and update UE buffer state
bwp_pdsch_slot.dl.data.emplace_back();
ue.build_pdu(ue.h_dl->tbs(), bwp_pdsch_slot.dl.data.back());
// Generate PUCCH
bwp_uci_slot.pending_acks.emplace_back();

30
srsgnb/src/stack/mac/sched_nr_ue.cc
Unescape Escape View File

@ -27,8 +27,16 @@ int ue_buffer_manager::get_dl_tx_total() const
return total_bytes;
}
void ue_buffer_manager::pdu_builder::alloc_subpdus(uint32_t rem_bytes, sched_nr_interface::dl_pdu_t& pdu)
// Return true if there is no SRB0/CCCH MAC PDU segmentation, false otherwise
bool ue_buffer_manager::pdu_builder::alloc_subpdus(uint32_t rem_bytes, sched_nr_interface::dl_pdu_t& pdu)
{
// In case of SRB0/CCCH PDUs, we need to check whether there is PDU segmentation; if LCID = 0 has emtpy buffer, no
// need to perform this check
bool check_ccch_pdu_segmentation =
parent->get_dl_tx_total(srsran::mac_sch_subpdu_nr::nr_lcid_sch_t::CCCH) > 0 ? true : false;
// First step: allocate MAC CEs until resources allow
srsran::deque<ce_t> restore_ces;
for (ce_t ce : parent->pending_ces) {
if (ce.cc == cc) {
// Note: This check also avoids thread collisions across UE carriers
@ -38,17 +46,35 @@ void ue_buffer_manager::pdu_builder::alloc_subpdus(uint32_t rem_bytes, sched_nr_
}
rem_bytes -= size_ce;
pdu.subpdus.push_back(ce.lcid);
parent->pending_ces.pop_front();
// If there is possibility of CCCH segmentation, we need to save the MAC CEs in a tmp queue to be later restored
if (check_ccch_pdu_segmentation) {
restore_ces.push_back(parent->pending_ces.front());
parent->pending_ces.pop_front();
}
}
}
// Second step: allocate the remaining LCIDs (LCIDs for MAC CEs are addressed above)
for (uint32_t lcid = 0; rem_bytes > 0 and is_lcid_valid(lcid); ++lcid) {
uint32_t pending_lcid_bytes = parent->get_dl_tx_total(lcid);
// Verify if the TBS is big enough to store the entire CCCH buffer
// Note: (pending_lcid_bytes > rem_bytes) implies (check_ccch_pdu_segmentation == true)
if (lcid == srsran::mac_sch_subpdu_nr::nr_lcid_sch_t::CCCH and pending_lcid_bytes > rem_bytes) {
// restore the MAC CEs as they were at the beginning of the function
for (ce_t ce : restore_ces) {
parent->pending_ces.push_back(ce);
}
// double check if this line is required
pdu.subpdus.clear();
return false;
}
if (pending_lcid_bytes > 0) {
rem_bytes -= std::min(rem_bytes, pending_lcid_bytes);
pdu.subpdus.push_back(lcid);
}
}
return true;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

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