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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/apply_channelmod.c
+7 -6
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@@ -42,12 +42,13 @@
legacy: we regenerate each sub frame in UL, and each frame only in DL
*/
void rxAddInput(const c16_t *input_sig,
c16_t *after_channel_sig,
cf_t *after_channel_sig,
int rxAnt,
channel_desc_t *channelDesc,
int nbSamples,
uint64_t TS,
uint32_t CirSize)
uint32_t CirSize,
bool add_noise)
{
if ((channelDesc->sat_height > 0) && (channelDesc->enable_dynamic_delay || channelDesc->enable_dynamic_Doppler)) { // model for transparent satellite on circular orbit
/* assumptions:
@@ -127,12 +128,12 @@ void rxAddInput(const c16_t *input_sig,
const double pathLossLinear = pow(10,channelDesc->path_loss_dB/20.0);
// Energy in one sample to calibrate input noise
// the normalized OAI value seems to be 256 as average amplitude (numerical amplification = 1)
const double noise_per_sample = pow(10,channelDesc->noise_power_dB/10.0) * 256;
const double noise_per_sample = add_noise ? pow(10,channelDesc->noise_power_dB/10.0) * 256 : 0;
const uint64_t dd = channelDesc->channel_offset;
const int nbTx=channelDesc->nb_tx;
for (int i=0; i<nbSamples; i++) {
struct complex16 *out_ptr=after_channel_sig+i;
cf_t *out_ptr = after_channel_sig + i;
struct complexd rx_tmp= {0};
for (int txAnt=0; txAnt < nbTx; txAnt++) {
@@ -166,8 +167,8 @@ void rxAddInput(const c16_t *input_sig,
channelDesc->Doppler_phase_cur[rxAnt] += channelDesc->Doppler_phase_inc;
}
out_ptr->r = lround(rx_tmp.r*pathLossLinear + noise_per_sample*gaussZiggurat(0.0,1.0));
out_ptr->i = lround(rx_tmp.i*pathLossLinear + noise_per_sample*gaussZiggurat(0.0,1.0));
out_ptr->r += rx_tmp.r * pathLossLinear + noise_per_sample * gaussZiggurat(0.0, 1.0);
out_ptr->i += rx_tmp.i * pathLossLinear + noise_per_sample * gaussZiggurat(0.0, 1.0);
out_ptr++;
}