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Enforce N_PRB=2^x3^y5^z in SC-FDMA uplink scheduler #247

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Enforce N_PRB=2^x3^y5^z in SC-FDMA uplink scheduler #247

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With SC-FDMA, scheduler in uplink needs to schedule N_PRB=2^x3^y5^z*
PC-OC Jul 2, 2026
ce95a4d
Remove trailing spaces
PC-OC Jul 2, 2026
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10 changes: 10 additions & 0 deletions openair2/GNB_APP/gnb_config.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1731,6 +1731,16 @@ void RCconfig_nr_macrlc(configmodule_interface_t *cfg)
else
ul_bler_options->harq_round_max = *gpd(params, np, MACRLC_UL_HARQ_ROUND_MAX)->u8ptr;
RC.nrmac[j]->min_grant_prb = *gpd(params, np, MACRLC_MIN_GRANT_PRB)->u16ptr;
long uses_sc_fdma = 0;

@rorsc rorsc Jul 3, 2026

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that's exactly wrong. check_sc_fdma_rbsize() uses NR_PUSCH_Config__transformPrecoder_enabled to check if SC-FDMA is enabled. that constant is 0, so here, by default and if msg3_transformPrecoder is not set, will be set to enabled when it should be disabled.

please fix

@rorsc rorsc Jul 3, 2026

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IOW, initialize with NR_PUSCH_Config__transformPrecoder_disabled

if (RC.nrmac[j]->common_channels[0].ServingCellConfigCommon->uplinkConfigCommon->initialUplinkBWP->rach_ConfigCommon->choice.setup->msg3_transformPrecoder != NULL) {
uses_sc_fdma = *RC.nrmac[j]->common_channels[0].ServingCellConfigCommon->uplinkConfigCommon->initialUplinkBWP->rach_ConfigCommon->choice.setup->msg3_transformPrecoder;
}
int new_min = check_sc_fdma_rbsize(uses_sc_fdma, RC.nrmac[j]->min_grant_prb);
// NR_PUSCH_Config__transformPrecoder_enabled = 0 | NR_PUSCH_Config__transformPrecoder_disabled = 1, so !uses_sc_fdma should be used
if (!uses_sc_fdma && RC.nrmac[j]->min_grant_prb != new_min) {

@rorsc rorsc Jul 3, 2026

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i know that you have that comment, but it's really confusing that !uses_sc_fdma means "we have SC-FDMA"

one suggestion I have is to rename the variable and check

sc_fdma == NR_PUSCH_Config__transformPrecoder_enabled

then it's clear and the 0/1 confusion is not visible

LOG_W(NR_MAC, "min_rb value is set as %d. In SC-FDMA, it should be under format 2^x*3^y*5^z and has been automatically decreased to %d.\n", RC.nrmac[j]->min_grant_prb, new_min);
RC.nrmac[j]->min_grant_prb = new_min;
}
RC.nrmac[j]->identity_pm = *gpd(params, np, MACRLC_IDENTITY_PM)->u8ptr;
// PRB Blacklist
uint16_t prbbl[MAX_BWP_SIZE] = {0};
Expand Down
19 changes: 0 additions & 19 deletions openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
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Expand Up @@ -677,17 +677,6 @@ bool update_rb_mcs_tbs(NR_sched_pdsch_t *pdsch, uint32_t num_total_bytes, uint16
return true;
}

static bool multiple_2_3_5(int rb)
{
while (rb % 2 == 0)
rb /= 2;
while (rb % 3 == 0)
rb /= 3;
while (rb % 5 == 0)
rb /= 5;

return (rb == 1);
}

bool nr_find_nb_rb(uint16_t Qm,
uint16_t R,
Expand All @@ -701,10 +690,6 @@ bool nr_find_nb_rb(uint16_t Qm,
uint32_t *tbs,
uint16_t *nb_rb)
{
// for transform precoding only RB = 2^a_2 * 3^a_3 * 5^a_5 is allowed with a non-negative
while (transform_precoding == NR_PUSCH_Config__transformPrecoder_enabled && !multiple_2_3_5(nb_rb_max))
nb_rb_max--;

/* is the maximum (not even) enough? */
*nb_rb = nb_rb_max;
*tbs = nr_compute_tbs(Qm, R, *nb_rb, nb_symb_sch, nb_dmrs_prb, 0, 0, nrOfLayers) >> 3;
Expand All @@ -726,10 +711,6 @@ bool nr_find_nb_rb(uint16_t Qm,
int hi = nb_rb_max;
int lo = nb_rb_min;
for (int p = (hi + lo) / 2; lo + 1 < hi; p = (hi + lo) / 2) {
// for transform precoding only RB = 2^a_2 * 3^a_3 * 5^a_5 is allowed with a non-negative
while(transform_precoding == NR_PUSCH_Config__transformPrecoder_enabled &&
!multiple_2_3_5(p))
p++;

// If by increasing p for transform precoding we already hit the high, break to avoid infinite loop
if (p == hi)
Expand Down
43 changes: 39 additions & 4 deletions openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_ulsch.c
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Expand Up @@ -14,9 +14,42 @@
#include <openair2/UTIL/OPT/opt.h>
#include "LAYER2/nr_rlc/nr_rlc_oai_api.h"

static const uint16_t NR_TRANSFORM_PRECODE_RB_LUT[274] = {
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0, 1, 2, 3, 4, 5, 6, 6, 8, 9, 10, 10, 12, 12, 12, 15,
16, 16, 18, 18, 20, 20, 20, 20, 24, 25, 25, 27, 27, 27, 30, 30,
32, 32, 32, 32, 36, 36, 36, 36, 40, 40, 40, 40, 40, 45, 45, 45,
48, 48, 50, 50, 50, 50, 54, 54, 54, 54, 54, 54, 60, 60, 60, 60,
64, 64, 64, 64, 64, 64, 64, 64, 72, 72, 72, 75, 75, 75, 75, 75,
80, 81, 81, 81, 81, 81, 81, 81, 81, 81, 90, 90, 90, 90, 90, 90,
96, 96, 96, 96, 100, 100, 100, 100, 100, 100, 100, 100, 108, 108, 108, 108,
108, 108, 108, 108, 108, 108, 108, 108, 120, 120, 120, 120, 120, 125, 125, 125,
128, 128, 128, 128, 128, 128, 128, 135, 135, 135, 135, 135, 135, 135, 135, 135,
144, 144, 144, 144, 144, 144, 150, 150, 150, 150, 150, 150, 150, 150, 150, 150,
160, 160, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162,
162, 162, 162, 162, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180,
192, 192, 192, 192, 192, 192, 192, 192, 200, 200, 200, 200, 200, 200, 200, 200,
200, 200, 200, 200, 200, 200, 200, 200, 216, 216, 216, 216, 216, 216, 216, 216,
216, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225,
240, 240, 240, 243, 243, 243, 243, 243, 243, 243, 250, 250, 250, 250, 250, 250,
256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 270, 270,
270, 270
};

//#define SRS_IND_DEBUG
#define MAX_NUM_DATA_IND 1024


// With SC-FDMA the scheduler in uplink needs to schedule N_PRB=2^x3^y5^z
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// Check 6.3.1.4 of 38.211
int check_sc_fdma_rbsize(long transform_precoding, uint16_t rb)
{
if (transform_precoding == NR_PUSCH_Config__transformPrecoder_enabled) {
return rb < 274 ? NR_TRANSFORM_PRECODE_RB_LUT[rb] : NR_TRANSFORM_PRECODE_RB_LUT[273];

@francescomani francescomani Jul 2, 2026

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Not sure if it makes sense to check RB < 274 since the max BWP is 273 RBs. I would have rather put an assertion. But it's not a blocking point.

}
return rb;
}


/* \brief Get the number of UL TDAs that could be used in slot, reachable
* via specific k2. The output parameter first_idx is a pointer to the first
* suitable TDA, and the function returns the number of suitable TDAs, or 0. */
Expand Down Expand Up @@ -1760,11 +1793,11 @@ static int apply_ul_retransmission(gNB_MAC_INST *nrmac,
} else {
/* TDA changed vs original retx: recompute DMRS and TB size for new TDA */
NR_pusch_dmrs_t dmrs_info = get_ul_dmrs_params(scc, current_BWP, tda_info, nrOfLayers);
new_sched.rbSize = cand->sched_pusch.rbSize;
new_sched.rbSize = check_sc_fdma_rbsize(current_BWP->transform_precoding, cand->sched_pusch.rbSize);
new_sched.rbStart = cand->sched_pusch.rbStart;
new_sched.tb_size = nr_compute_tbs(retInfo->Qm,
retInfo->R,
cand->sched_pusch.rbSize,
new_sched.rbSize,
tda_info->nrOfSymbols,
dmrs_info.N_PRB_DMRS * dmrs_info.num_dmrs_symb,
0,
Expand Down Expand Up @@ -1819,6 +1852,7 @@ static int apply_ul_new_transmission(gNB_MAC_INST *nrmac,
* time_domain_allocation, tda_info already set by pipeline stages).
* Fill remaining dispatch fields: R, Qm, tb_size, dmrs_info, bwp_info. */
NR_sched_pusch_t sched = cand->sched_pusch;
sched.rbSize = check_sc_fdma_rbsize(current_BWP->transform_precoding, sched.rbSize);
sched.frame = sched_frame;
sched.slot = sched_slot;
sched.ul_harq_pid = -1;
Expand Down Expand Up @@ -2625,6 +2659,7 @@ bool nr_ul_check_phr(const nr_ul_sched_params_t *params,
pot.dmrs_info = dmrs_info;
pot.nrOfLayers = cand->sched_pusch.nrOfLayers;
pot.rbSize = rbSize;
pot.rbSize = check_sc_fdma_rbsize(current_BWP->transform_precoding, pot.rbSize);
pot.mcs = mcs;

uint16_t R;
Expand All @@ -2646,8 +2681,8 @@ bool nr_ul_check_phr(const nr_ul_sched_params_t *params,
NR_sched_pusch_t p1 = pot;
int tp = tx_power;

while (cand->ph < tp && p1.rbSize > params->min_rb) {
p1.rbSize--;
while (cand->ph < tp && p1.rbSize > params->min_rb && check_sc_fdma_rbsize(current_BWP->transform_precoding, p1.rbSize-1) >= params->min_rb) {
p1.rbSize = check_sc_fdma_rbsize(current_BWP->transform_precoding, --p1.rbSize);
p1.tb_size = nr_compute_tbs(p1.Qm, p1.R, p1.rbSize, p1.tda_info.nrOfSymbols, n_dmrs, 0, 0, p1.nrOfLayers) >> 3;
tp = compute_ph_rb_factor(current_BWP->scs, p1.rbSize) + (hasDeltaMCS ? compute_ph_mcs_factor(&p1) : 0);
}
Expand Down
2 changes: 2 additions & 0 deletions openair2/LAYER2/NR_MAC_gNB/mac_proto.h
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Expand Up @@ -89,6 +89,8 @@ void nr_schedule_ulsch(module_id_t module_id, frame_t frame, slot_t slot, nfapi_
/* \brief default UL preprocessor */
void nr_ulsch_preprocessor(gNB_MAC_INST *nr_mac, post_process_pusch_t *pp_pusch);

int check_sc_fdma_rbsize(long transform_precoding, uint16_t rb);

void nr_mac_pcch_queue_init(NR_COMMON_channels_t *cc);
void nr_mac_pcch_queue_free(NR_COMMON_channels_t *cc);
void nr_mac_pcch_enqueue(module_id_t module_id, uint64_t fiveg_s_tmsi, uint16_t ue_id);
Expand Down