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Add option to use global noise power for all RX channels in RFSimulator

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Added new command line option to channelmod: noise_power_dBFS. This options
allows the user to configure noise power in dBFS added instead of the per-channel
value.

This makes it so noise is not accumulated per channel reaching higher than expected
values.

The dBFS unit allows easy configuration. The gNB by default uses -36 dBFS setting.
To reach 3dB SNR one should set the noise_power_dBFS value to -39.

To configure using command line use --channelmod.noise_power_dBFS -50. Using this
setting the gNB and nrUE connect without issue.
This commit is contained in:
Bartosz Podrygajlo
2025-02-19 16:05:38 +01:00
parent 82fbb6bb04
commit 2fb541a68e
6 changed files with 54 additions and 11 deletions
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radio/rfsimulator/simulator.c
+31 -3
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@@ -1006,7 +1006,9 @@ static int rfsimulator_read(openair0_device *device, openair0_timestamp *ptimest
// Clear the output buffer
for (int a=0; a<nbAnt; a++)
memset(samplesVoid[a],0,sampleToByte(nsamps,1));
cf_t temp_array[nbAnt][nsamps];
bool apply_noise_per_channel = get_noise_power_dBFS() == INVALID_DBFS_VALUE;
int num_chanmod_channels = 0;
// Add all input nodes signal in the output buffer
for (int sock = 0; sock < MAX_FD_RFSIMU; sock++) {
buffer_t *ptr=&t->buf[sock];
@@ -1024,12 +1026,18 @@ static int rfsimulator_read(openair0_device *device, openair0_timestamp *ptimest
for (int a=0; a<nbAnt; a++) {//loop over number of Rx antennas
if ( ptr->channel_model != NULL ) { // apply a channel model
rxAddInput(ptr->circularBuf, (c16_t *) samplesVoid[a],
if (num_chanmod_channels == 0) {
memset(temp_array, 0, sizeof(temp_array));
}
num_chanmod_channels++;
rxAddInput(ptr->circularBuf,
temp_array[a],
a,
ptr->channel_model,
nsamps,
t->nextRxTstamp,
CirSize);
CirSize,
apply_noise_per_channel);
}
else { // no channel modeling
int nbAnt_tx = ptr->th.nbAnt; // number of Tx antennas
@@ -1063,6 +1071,26 @@ static int rfsimulator_read(openair0_device *device, openair0_timestamp *ptimest
} // end for a (number of rx antennas)
}
}
if (apply_noise_per_channel && num_chanmod_channels > 0) {
// Noise is already applied through the channel model
for (int a = 0; a < nbAnt; a++) {
sample_t *out = (sample_t *)samplesVoid[a];
for (int i = 0; i < nsamps; i++) {
out[i].r += lroundf(temp_array[a][i].r);
out[i].i += lroundf(temp_array[a][i].i);
}
}
} else if (num_chanmod_channels > 0) {
// Apply noise from global setting
int16_t noise_power = (int16_t)(32767.0 / powf(10.0, .05 * -get_noise_power_dBFS()));
for (int a = 0; a < nbAnt; a++) {
sample_t *out = (sample_t *)samplesVoid[a];
for (int i = 0; i < nsamps; i++) {
out[i].r += lroundf(temp_array[a][i].r + noise_power * gaussZiggurat(0.0, 1.0));
out[i].i += lroundf(temp_array[a][i].i + noise_power * gaussZiggurat(0.0, 1.0));
}
}
}
*ptimestamp = t->nextRxTstamp; // return the time of the first sample
t->nextRxTstamp+=nsamps;