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NR UE: add support for continuous UL frequency offset pre-compensation

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Depending on the main source of frequency offset, pre-compensate the UL frequency offset (FO) accordingly.
Therefore modify the flag `--cont-fo-comp` to accept an integer value, where
 - `1` specifies, that the main FO contribution comes from the accuracy of the local oscillator (LO)
 - `2` specifies, that the main FO contribution comes from Doppler shift
This commit is contained in:
Thomas Schlichter
2025-01-14 13:21:58 +01:00
parent aac4642910
commit 84712f5f92
3 changed files with 14 additions and 3 deletions
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3
doc/RUNMODEM.md
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@@ -136,7 +136,8 @@ Here are some useful command line options for the NR UE:
| Parameter | Description |
|--------------------------|---------------------------------------------------------------------------------------------------------------|
| `--ue-scan-carrier` | Scan for cells in current bandwidth. This option can be used if the SSB position of the gNB is unknown. If multiple cells are detected, the UE will try to connect to the first cell. By default, this option is disabled and the UE attempts to only decode SSB given by `--ssb`. |
| `--ue-fo-compensation` | Enables the frequency offset compensation at the UE. Useful when running over the air and/or without an external clock/time source. |
| `--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. |
| `--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). |

10
executables/nr-ue.c
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@@ -41,6 +41,7 @@
#include "instrumentation.h"
#include "common/utils/threadPool/notified_fifo.h"
#include "position_interface.h"
#include "nr_phy_common.h"
/*
* NR SLOT PROCESSING SEQUENCE
@@ -554,6 +555,15 @@ static void RU_write(nr_rxtx_thread_data_t *rxtxD, bool sl_tx_action)
writeBlockSize -= dummyBlockSize;
}
// pre-compensate UL frequency offset
if (flags != TX_BURST_INVALID && get_nrUE_params()->cont_fo_comp) {
double ul_freq_offset = -UE->freq_offset * ((double)fp->ul_CarrierFreq / (double)fp->dl_CarrierFreq);
if (get_nrUE_params()->cont_fo_comp == 2) // different from LO frequency error compensation, Doppler UL pre-compensation has to be negative
ul_freq_offset = -ul_freq_offset;
for (int i = 0; i < fp->nb_antennas_tx; i++)
nr_fo_compensation(ul_freq_offset, fp->samples_per_subframe, writeTimestamp, txp[i], writeBlockSize);
}
int tmp = openair0_write_reorder(&UE->rfdevice, writeTimestamp, txp, writeBlockSize, fp->nb_antennas_tx, flags);
AssertFatal(tmp == writeBlockSize, "");
}

4
executables/nr-uesoftmodem.h
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@@ -15,7 +15,7 @@
#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_CONT_FO_COMP "Enable continuous frequency offset estimation and compensation\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"
/***************************************************************************************************************************************/
@@ -68,7 +68,7 @@
{"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}, \
{"cont-fo-comp", CONFIG_HLP_CONT_FO_COMP, PARAMFLAG_BOOL, .iptr=&(nrUE_params.cont_fo_comp), .defintval=0, TYPE_INT, 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}, \
}
// clang-format on