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Merge remote-tracking branch 'origin/fix-ema-init' into integration_2026_w16 (!4051)

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Fix EMA cold-start for noise and SNR/RSSI measurements

Initialize n0_subband_power and power control avg_snr/avg_rssi directly
from the first measurement instead of starting from zero.

Starting from zero causes the EMA to converge slowly, leading to
underestimated noise power at gNB startup. This results in inflated SNR
estimates, which triggers UE uplink power ramp-up, antenna saturation,
and a positive feedback loop of increasing noise.
This commit is contained in:
Jaroslava Fiedlerova
2026-04-16 23:09:51 +02:00
parent e5c54b5971 6f2d90fee9
commit 93df326273
5 changed files with 25 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
openair1/PHY/NR_ESTIMATION/nr_measurements_gNB.c
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@@ -162,6 +162,7 @@ void gNB_I0_measurements(PHY_VARS_gNB *gNB, int slot, int first_symb, int num_sy
int32_t n0_subband_tot_perANT[frame_parms->nb_antennas_rx];
memset(n0_subband_tot_perANT, 0, sizeof(n0_subband_tot_perANT));
bool init_meas = measurements->n0_subband_power == NULL;
allocCast2D(n0_subband_power,
unsigned int,
measurements->n0_subband_power,
@@ -174,6 +175,9 @@ void gNB_I0_measurements(PHY_VARS_gNB *gNB, int slot, int first_symb, int num_sy
if (nb_symb[rb] > 0) {
for (int aarx = 0; aarx < frame_parms->nb_antennas_rx; aarx++) {
tmp_n0_subband[aarx][rb] /= nb_symb[rb];
// Initialize n0_subband_power from the first measurement before EMA
if (init_meas)
n0_subband_power[aarx][rb] = tmp_n0_subband[aarx][rb];
// apply exponential moving average to smooth noise measurements
n0_subband_power[aarx][rb] = 0.9 * n0_subband_power[aarx][rb] + 0.1 * tmp_n0_subband[aarx][rb];
n0_subband_tot_perPRB += n0_subband_power[aarx][rb];

15
openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
View File

@@ -4190,6 +4190,21 @@ void nr_mac_pc_snr(nr_power_control_t *pc, int snrx10, int rssi)
pc->tpc_in_flight = PC_AVG_CNST * pc->tpc_in_flight; // + (1 - PC_AVG_CNST) * 0.0f
}
/**
* @brief Enter new SNR and RSSI value for the latest UL transmission as new
* fixed averages. Reset "TPC in flight" to zero.
*
* @param pc the power control loop
* @param snrx10 the current SNR measurement multiplied by 10
* @param rssi the current RSSI measurement
*/
void nr_mac_pc_reset_snr(nr_power_control_t *pc, int snrx10, int rssi)
{
pc->avg_snr = 0.1f * snrx10;
pc->avg_rssi = rssi;
pc->tpc_in_flight = 0.0f;
}
/**
* @brief Set a new target SNR for this power control loop, which can be
* updated on a continuous basis, and will be reflected immediately upon

3
openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_uci.c
View File

@@ -910,6 +910,9 @@ void handle_nr_uci_pucch_0_1(module_id_t mod_id, frame_t frame, slot_t slot, con
NR_SCHED_UNLOCK(&nrmac->sched_lock);
return;
}
// Msg4 Ack: reset average with first measurement
if (uci_01->ul_cqi != 0xff)
nr_mac_pc_reset_snr(&UE->UE_sched_ctrl.pucch_pc, uci_01->ul_cqi * 5 - 640, uci_01->rssi);
}
if (harq_confidence == 1) {
UE->mac_stats.pucch0_DTX++;

6
openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_ulsch.c
View File

@@ -762,11 +762,9 @@ static void nr_rx_ra_sdu(const module_id_t mod_id,
}
if (ul_cqi != 0xff) {
NR_UE_sched_ctrl_t *sched_ctrl = &UE->UE_sched_ctrl;
// Msg3: reset average. If this fails (e.g., ul_cqi == 0xff)
// Msg3: reset average with first measurement. If this fails (e.g., ul_cqi == 0xff)
// everything starts from predetermined value
sched_ctrl->pusch_pc.avg_snr = 0.1 * (ul_cqi * 5 - 640);
sched_ctrl->pusch_pc.avg_rssi = rssi;
nr_mac_pc_reset_snr(&UE->UE_sched_ctrl.pusch_pc, ul_cqi * 5 - 640, rssi);
}
if (!sdu) { // NACK

1
openair2/LAYER2/NR_MAC_gNB/mac_proto.h
View File

@@ -500,6 +500,7 @@ void post_process_ulsch(gNB_MAC_INST *nr_mac, post_process_pusch_t *pusch, NR_UE
float nr_mac_get_snr(const nr_power_control_t *pc);
void nr_mac_pc_snr(nr_power_control_t *pc, int snrx10, int rssi);
void nr_mac_pc_reset_snr(nr_power_control_t *pc, int snrx10, int rssi);
void nr_mac_set_target_snrx10(nr_power_control_t *pc, int target_snrx10);
void nr_mac_set_rssi_threshold(nr_power_control_t *pc, int rssi_threshold);
void nr_mac_signal_dtx(nr_power_control_t *pc);