Thomas Schlichter
a9132a2f79
esp. for LEO NTN scenarios the timing drifts during initial sync, which is mostly compensated with --ntn-initial-time-drift. But there might be a residual time offset, and by extending the peak search window we make this more tolerant.
101 lines
3.6 KiB
C
101 lines
3.6 KiB
C
/*
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* Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The OpenAirInterface Software Alliance licenses this file to You under
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* the OAI Public License, Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.openairinterface.org/?page_id=698
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*-------------------------------------------------------------------------------
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* For more information about the OpenAirInterface (OAI) Software Alliance:
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* contact@openairinterface.org
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*/
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#include "PHY/types.h"
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#include "PHY/defs_nr_UE.h"
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#include "PHY/NR_UE_ESTIMATION/nr_estimation.h"
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#include "PHY/impl_defs_top.h"
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#include "executables/nr-uesoftmodem.h"
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#include "common/utils/LOG/vcd_signal_dumper.h"
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//#define DEBUG_PHY
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// Adjust location synchronization point to account for drift
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// The adjustment is performed once per frame based on the
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// last channel estimate of the receiver
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int nr_adjust_synch_ue(NR_DL_FRAME_PARMS *frame_parms,
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PHY_VARS_NR_UE *ue,
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module_id_t gNB_id,
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const int estimateSz,
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struct complex16 dl_ch_estimates_time[][estimateSz],
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uint8_t frame,
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uint8_t slot,
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short coef)
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{
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int max_val = 0, max_pos = 0;
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VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_UE_ADJUST_SYNCH, VCD_FUNCTION_IN);
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// search for maximum position within the cyclic prefix
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for (int i = -frame_parms->nb_prefix_samples; i < frame_parms->nb_prefix_samples; i++) {
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int temp = 0;
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int j = (i < 0) ? (i + frame_parms->ofdm_symbol_size) : i;
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for (int aa = 0; aa < frame_parms->nb_antennas_rx; aa++) {
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int Re = dl_ch_estimates_time[aa][j].r;
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int Im = dl_ch_estimates_time[aa][j].i;
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temp += (Re*Re/2) + (Im*Im/2);
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}
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if (temp > max_val) {
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max_pos = i;
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max_val = temp;
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}
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}
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// filter position to reduce jitter
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const int ncoef = 32767 - coef;
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ue->max_pos_iir = ((ue->max_pos_iir * coef) >> 15) + (max_pos * ncoef);
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const int diff = (ue->max_pos_iir + 16384) >> 15;
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// FIXME: Do we really need this hysteresis for FR2?
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int sampleShift = diff;
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if (frame_parms->freq_range == FR2)
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if (abs(diff) <= 2)
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sampleShift = 0;
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// PI controller
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const double PID_P = get_nrUE_params()->time_sync_P;
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const double PID_I = get_nrUE_params()->time_sync_I;
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int sample_shift = -round(sampleShift * PID_P + ue->max_pos_acc * PID_I);
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LOG_D(PHY,
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"Frame %d, Slot %d: max_pos = %d, max_pos filtered = %f, diff = %i, sampleShift = %i, max_pos_acc = %d, sample_shift (final) = %d, max_power = %d\n",
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frame,
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slot,
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max_pos,
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ue->max_pos_iir / 32768.0,
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diff,
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sampleShift,
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ue->max_pos_acc,
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sample_shift,
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max_val);
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// reset IIR filter for next offset calculation
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ue->max_pos_iir += -round(sampleShift * PID_P) * 32768;
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ue->max_pos_acc += max_pos;
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VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_UE_ADJUST_SYNCH, VCD_FUNCTION_OUT);
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return sample_shift;
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}
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