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NR UE: add PI controller to continuous frequency offset compensation

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This commit is contained in:
Thomas Schlichter
2025-04-10 13:56:20 +00:00
parent 84712f5f92
commit 18469302d8
4 changed files with 15 additions and 2 deletions
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doc/RUNMODEM.md
+2
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@@ -139,6 +139,8 @@ Here are some useful command line options for the NR UE:
| `--ue-fo-compensation` | Enables the initial frequency offset compensation at the UE. Useful when running over the air and/or without an external clock/time source. |
| `--cont-fo-comp` | Enables the continuous frequency offset (FO) estimation and compensation. Parameter value `1` specifies that the main FO contribution comes from the local oscillator's (LO) accuracy. Parameter value `2` specifies that the main FO contribution comes from Doppler shift. |
| `--initial-fo` | Sets the known initial frequency offset. Useful especially with large Doppler frequency, e.g. LEO satellite. |
| `--freq-sync-P` | Sets the coefficient for the Proportional part of the PI-controller for the continuous frequency offset compensation. Default value 0.01. |
| `--freq-sync-I` | Sets the coefficient for the Integrating part of the PI-controller for the continuous frequency offset compensation. Default value 0.001. |
| `--usrp-args` | Equivalent to the `sdr_addrs` field in the gNB config file. Used to identify the USRP and set some basic parameters (like the clock source). |
| `--clock-source` | Sets the clock source (internal or external). |
| `--time-source` | Sets the time source (internal or external). |
executables/nr-uesoftmodem.h
+6
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@@ -15,6 +15,8 @@
#define CONFIG_HLP_NTN_INIT_TIME_DRIFT "Initial NTN DL time drift (feeder link and service link), given in µs/s\n"
#define CONFIG_HLP_AUTONOMOUS_TA "Autonomously update TA based on DL drift (useful if main contribution to DL drift is movement, e.g. LEO satellite)\n"
#define CONFIG_HLP_INITIAL_FO "Initially compensated DL frequency offset (e.g. known Doppler shift in NTN LEO scenario)\n"
#define CONFIG_HLP_FREQ_SYNC_P "coefficient for Proportional part of continuous frequency offset compensation PI controller\n"
#define CONFIG_HLP_FREQ_SYNC_I "coefficient for Integrating part of continuous frequency offset compensation PI controller\n"
#define CONFIG_HLP_CONT_FO_COMP "Enable continuous frequency offset (FO) estimation and compensation and specify main FO source (1 = local oscillator, 2 = Doppler shift)\n"
#define CONFIG_HLP_AGC "Rx Gain control used for UE\n"
@@ -68,6 +70,8 @@
{"ntn-initial-time-drift", CONFIG_HLP_NTN_INIT_TIME_DRIFT, 0, .dblptr=&(nrUE_params.ntn_init_time_drift), .defdblval=0.0, TYPE_DOUBLE, 0}, \
{"autonomous-ta", CONFIG_HLP_AUTONOMOUS_TA, PARAMFLAG_BOOL, .iptr=&(nrUE_params.autonomous_ta), .defintval=0, TYPE_INT, 0}, \
{"initial-fo", CONFIG_HLP_INITIAL_FO, 0, .dblptr=&(nrUE_params.initial_fo), .defdblval=0.0, TYPE_DOUBLE, 0}, \
{"freq-sync-P", CONFIG_HLP_FREQ_SYNC_P, 0, .dblptr=&(nrUE_params.freq_sync_P), .defdblval=0.01, TYPE_DOUBLE, 0}, \
{"freq-sync-I", CONFIG_HLP_FREQ_SYNC_I, 0, .dblptr=&(nrUE_params.freq_sync_I), .defdblval=0.001, TYPE_DOUBLE, 0}, \
{"cont-fo-comp", CONFIG_HLP_CONT_FO_COMP, 0, .iptr=&(nrUE_params.cont_fo_comp), .defintval=0, TYPE_INT, 0}, \
{"agc", CONFIG_HLP_AGC, PARAMFLAG_BOOL, .iptr=&(nrUE_params.agc), .defintval=0, TYPE_INT, 0}, \
}
@@ -94,6 +98,8 @@ typedef struct {
double ntn_init_time_drift;
int autonomous_ta;
double initial_fo;
double freq_sync_P;
double freq_sync_I;
int cont_fo_comp;
int agc;
char *usrp_args;
openair1/PHY/defs_nr_UE.h
+1
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@@ -463,6 +463,7 @@ typedef struct PHY_VARS_NR_UE_s {
double initial_fo; /// initial frequency offset provided by the user
int cont_fo_comp; /// flag enabling the continuous frequency offset estimation and compensation
double freq_offset; /// currently compensated frequency offset
double freq_off_acc; /// accumulated frequency error (for PI controller)
/// Timing Advance updates variables
/// Timing advance update computed from the TA command signalled from gNB
openair1/SCHED_NR_UE/phy_procedures_nr_ue.c
+6 -2
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@@ -932,9 +932,13 @@ int pbch_pdcch_processing(PHY_VARS_NR_UE *ue, const UE_nr_rxtx_proc_t *proc, nr_
if (get_nrUE_params()->cont_fo_comp && pbchSuccess == 0) {
double freq_offset = nr_ue_pbch_freq_offset(fp, estimateSz, dl_ch_estimates);
LOG_D(PHY,"compensated frequency offset = %.3f Hz, detected residual frequency offset = %.3f Hz\n", ue->freq_offset, freq_offset);
LOG_D(PHY,"compensated frequency offset = %.3f Hz, detected residual frequency offset = %.3f Hz, accumulated frequency offset = %.3f Hz\n", ue->freq_offset, freq_offset, ue->freq_off_acc);
ue->freq_offset += freq_offset;
// PI controller
const double PID_P = get_nrUE_params()->freq_sync_P;
const double PID_I = get_nrUE_params()->freq_sync_I;
ue->freq_offset += freq_offset * PID_P + ue->freq_off_acc * PID_I;
ue->freq_off_acc += freq_offset;
}
}
LOG_D(PHY, "Doing N0 measurements in %s\n", __FUNCTION__);