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openairinterface5g/radio/rfsimulator/apply_channelmod.c
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/*
* Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The OpenAirInterface Software Alliance licenses this file to You under
* the OAI Public License, Version 1.1 (the "License"); you may not use this file
* except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.openairinterface.org/?page_id=698
*
* Author and copyright: Laurent Thomas, open-cells.com
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*-------------------------------------------------------------------------------
* For more information about the OpenAirInterface (OAI) Software Alliance:
* contact@openairinterface.org
*/
#include <complex.h>
#include <common/utils/LOG/log.h>
#include <openair1/SIMULATION/TOOLS/sim.h>
#include "openair2/LAYER2/NR_MAC_gNB/mac_config.h"
#include "rfsimulator.h"
/*
Legacy study:
The parameters are:
gain&loss (decay, signal power, ...)
either a fixed gain in dB, a target power in dBm or ACG (automatic control gain) to a target average
=> don't redo the AGC, as it was used in UE case, that must have a AGC inside the UE
will be better to handle the "set_gain()" called by UE to apply it's gain (enable test of UE power loop)
lin_amp = pow(10.0,.05*txpwr_dBm)/sqrt(nb_tx_antennas);
a lot of operations in legacy, grouped in one simulation signal decay: txgain*decay*rxgain
multi_path (auto convolution, ISI, ...)
either we regenerate the channel (call again random_channel(desc,0)), or we keep it over subframes
legacy: we regenerate each sub frame in UL, and each frame only in DL
*/
void rxAddInput(const c16_t *input_sig,
cf_t *after_channel_sig,
int rxAnt,
channel_desc_t *channelDesc,
int nbSamples,
uint64_t TS,
uint32_t CirSize,
bool add_noise)
{
static uint64_t last_TS = 0;
if ((channelDesc->sat_height > 0) && (channelDesc->enable_dynamic_delay || channelDesc->enable_dynamic_Doppler)) { // model for transparent satellite on circular orbit
/* assumptions:
- The Earth is spherical, the ground station is static, and that the Earth does not rotate.
- An access or link is possible from the satellite to the ground station at all times.
- The ground station is located at the North Pole (positive Zaxis), and the satellite starts from the initial elevation angle 0° in the second quadrant of the YZplane.
- Satellite moves in the clockwise direction in its circular orbit.
*/
const double radius_earth = 6377900; // m
const double radius_sat = radius_earth + channelDesc->sat_height;
const double GM_earth = 3.986e14; // m^3/s^2
const double w_sat = sqrt(GM_earth / (radius_sat * radius_sat * radius_sat)); // rad/s
// start_time and end_time are when the pos_sat_z == pos_gnb_z (elevation angle == 0 and 180 degree)
const double start_phase = -acos(radius_earth / radius_sat); // SAT is just rising above the horizon
const double end_phase = -start_phase; // SAT is just falling behind the horizon
const double start_time = start_phase / w_sat; // in seconds
const double end_time = end_phase / w_sat; // in seconds
const uint64_t duration_samples = (end_time - start_time) * channelDesc->sampling_rate;
const double t = start_time + ((TS - channelDesc->start_TS) % duration_samples) / channelDesc->sampling_rate;
const double pos_sat_x = 0;
const double pos_sat_y = radius_sat * sin(w_sat * t);
const double pos_sat_z = radius_sat * cos(w_sat * t);
const double vel_sat_x = 0;
const double vel_sat_y = w_sat * radius_sat * cos(w_sat * t);
const double vel_sat_z = -w_sat * radius_sat * sin(w_sat * t);
const double pos_ue_x = 0;
const double pos_ue_y = 0;
const double pos_ue_z = radius_earth;
const double c = 299792458; // m/s
if (channelDesc->is_uplink) {
const double dir_ue_sat_x = pos_sat_x - pos_ue_x;
const double dir_ue_sat_y = pos_sat_y - pos_ue_y;
const double dir_ue_sat_z = pos_sat_z - pos_ue_z;
const double dist_ue_sat = sqrt(dir_ue_sat_x * dir_ue_sat_x + dir_ue_sat_y * dir_ue_sat_y + dir_ue_sat_z * dir_ue_sat_z);
const double vel_ue_sat = (vel_sat_x * dir_ue_sat_x + vel_sat_y * dir_ue_sat_y + vel_sat_z * dir_ue_sat_z) / dist_ue_sat;
double dist_sat_gnb = 0;
double vel_sat_gnb = 0;
double acc_sat_gnb = 0;
if (channelDesc->modelid == SAT_LEO_TRANS) {
const double acc_sat_x = 0;
const double acc_sat_y = -w_sat * w_sat * radius_sat * sin(w_sat * t);
const double acc_sat_z = -w_sat * w_sat * radius_sat * cos(w_sat * t);
const double pos_gnb_x = 0;
const double pos_gnb_y = 0;
const double pos_gnb_z = radius_earth;
const double dir_sat_gnb_x = pos_gnb_x - pos_sat_x;
const double dir_sat_gnb_y = pos_gnb_y - pos_sat_y;
const double dir_sat_gnb_z = pos_gnb_z - pos_sat_z;
dist_sat_gnb = sqrt(dir_sat_gnb_x * dir_sat_gnb_x + dir_sat_gnb_y * dir_sat_gnb_y + dir_sat_gnb_z * dir_sat_gnb_z);
vel_sat_gnb = (vel_sat_x * dir_sat_gnb_x + vel_sat_y * dir_sat_gnb_y + vel_sat_z * dir_sat_gnb_z) / dist_sat_gnb;
acc_sat_gnb = (acc_sat_x * dir_sat_gnb_x + acc_sat_y * dir_sat_gnb_y + acc_sat_z * dir_sat_gnb_z) / dist_sat_gnb;
}
const double prop_delay = (dist_ue_sat + dist_sat_gnb) / c;
if (channelDesc->enable_dynamic_delay)
channelDesc->channel_offset = prop_delay * channelDesc->sampling_rate;
const double f_Doppler_shift_ue_sat = (-vel_ue_sat / c) * channelDesc->center_freq;
if (channelDesc->enable_dynamic_Doppler)
channelDesc->Doppler_phase_inc = 2 * M_PI * f_Doppler_shift_ue_sat / channelDesc->sampling_rate;
if(TS - last_TS >= channelDesc->sampling_rate) {
last_TS = TS;
LOG_I(HW, "Satellite orbit: time %f s, Position = (%f, %f, %f), Velocity = (%f, %f, %f)\n", t, pos_sat_x, pos_sat_y, pos_sat_z, vel_sat_x, vel_sat_y, vel_sat_z);
LOG_I(HW, "Uplink delay %f ms, Doppler shift UE->SAT %f kHz\n", prop_delay * 1000, f_Doppler_shift_ue_sat / 1000);
LOG_I(HW, "Satellite velocity towards gNB: %f m/s, acceleration towards gNB: %f m/s²\n", vel_sat_gnb, acc_sat_gnb);
}
const int samples_per_subframe = channelDesc->sampling_rate / 1000;
const int abs_subframe = TS / samples_per_subframe;
if (abs_subframe % 10 == 0) { // update SIB19 information for the next frame
gnb_sat_position_update_t sat_position = {
.sfn = (abs_subframe / 10 + 1) % 1024,
.subframe = 0,
.delay = 2 * dist_sat_gnb / (c * 4.072e-9),
.drift = 2 * -vel_sat_gnb / (c * 0.2e-9),
.accel = 2 * acc_sat_gnb / (c * 0.2e-10),
.position.X = pos_sat_x / 1.3,
.position.Y = pos_sat_y / 1.3,
.position.Z = pos_sat_z / 1.3,
.velocity.X = vel_sat_x / 0.06,
.velocity.Y = vel_sat_y / 0.06,
.velocity.Z = vel_sat_z / 0.06,
};
// Here we update the SIB19 information directly in the gNB MAC layer.
// Without rf-simulaor, in a real system or with an external channel emulator, the SIB19 updates would
// be provided via an external interface (e.g. O-RAN E2 interface) to the MAC layer (in the O-DU).
// We do it directly here, because we can, and an E2 Interface implementation (e.g using FlexRIC)
// would pull too many dependencies into rf-simulator, just for updating SIB19.
nr_update_sib19(&sat_position);
}
} else {
const double dir_sat_ue_x = pos_ue_x - pos_sat_x;
const double dir_sat_ue_y = pos_ue_y - pos_sat_y;
const double dir_sat_ue_z = pos_ue_z - pos_sat_z;
const double dist_sat_ue = sqrt(dir_sat_ue_x * dir_sat_ue_x + dir_sat_ue_y * dir_sat_ue_y + dir_sat_ue_z * dir_sat_ue_z);
const double vel_sat_ue = (vel_sat_x * dir_sat_ue_x + vel_sat_y * dir_sat_ue_y + vel_sat_z * dir_sat_ue_z) / dist_sat_ue;
double dist_gnb_sat = 0;
if (channelDesc->modelid == SAT_LEO_TRANS) {
const double pos_gnb_x = 0;
const double pos_gnb_y = 0;
const double pos_gnb_z = radius_earth;
const double dir_gnb_sat_x = pos_sat_x - pos_gnb_x;
const double dir_gnb_sat_y = pos_sat_y - pos_gnb_y;
const double dir_gnb_sat_z = pos_sat_z - pos_gnb_z;
dist_gnb_sat = sqrt(dir_gnb_sat_x * dir_gnb_sat_x + dir_gnb_sat_y * dir_gnb_sat_y + dir_gnb_sat_z * dir_gnb_sat_z);
}
const double prop_delay = (dist_gnb_sat + dist_sat_ue) / c;
if (channelDesc->enable_dynamic_delay)
channelDesc->channel_offset = prop_delay * channelDesc->sampling_rate;
const double f_Doppler_shift_sat_ue = (vel_sat_ue / (c - vel_sat_ue)) * channelDesc->center_freq;
if (channelDesc->enable_dynamic_Doppler)
channelDesc->Doppler_phase_inc = 2 * M_PI * f_Doppler_shift_sat_ue / channelDesc->sampling_rate;
if(TS - last_TS >= channelDesc->sampling_rate) {
last_TS = TS;
LOG_I(HW, "Satellite orbit: time %f s, Position = (%f, %f, %f), Velocity = (%f, %f, %f)\n", t, pos_sat_x, pos_sat_y, pos_sat_z, vel_sat_x, vel_sat_y, vel_sat_z);
LOG_I(HW, "Downlink delay %f ms, Doppler shift SAT->UE %f kHz\n", prop_delay * 1000, f_Doppler_shift_sat_ue / 1000);
}
}
}
// channelDesc->path_loss_dB should contain the total path gain
// so, in actual RF: tx gain + path loss + rx gain (+antenna gain, ...)
// UE and NB gain control to be added
// Fixme: not sure when it is "volts" so dB is 20*log10(...) or "power", so dB is 10*log10(...)
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 = 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;
double Doppler_phase_cur = channelDesc->Doppler_phase_cur[rxAnt];
Doppler_phase_cur -= 2 * M_PI * round(Doppler_phase_cur / (2 * M_PI));
for (int i=0; i<nbSamples; i++) {
cf_t *out_ptr = after_channel_sig + i;
struct complexd rx_tmp= {0};
for (int txAnt=0; txAnt < nbTx; txAnt++) {
const struct complexd *channelModel= channelDesc->ch[rxAnt+(txAnt*channelDesc->nb_rx)];
//const struct complex *channelModelEnd=channelModel+channelDesc->channel_length;
for (int l = 0; l<(int)channelDesc->channel_length; l++) {
// let's assume TS+i >= l
// fixme: the rfsimulator current structure is interleaved antennas
// this has been designed to not have to wait a full block transmission
// but it is not very usefull
// it would be better to split out each antenna in a separate flow
// that will allow to mix ru antennas freely
// (X + cirSize) % cirSize to ensure that index is positive
const int idx = ((TS + i - l - dd) * nbTx + txAnt + CirSize) % CirSize;
const struct complex16 tx16 = input_sig[idx];
rx_tmp.r += tx16.r * channelModel[l].r - tx16.i * channelModel[l].i;
rx_tmp.i += tx16.i * channelModel[l].r + tx16.r * channelModel[l].i;
} //l
}
if (channelDesc->Doppler_phase_inc != 0.0) {
#ifdef CMPLX
double complex in = CMPLX(rx_tmp.r, rx_tmp.i);
#else
double complex in = rx_tmp.r + rx_tmp.i * I;
#endif
double complex out = in * cexp(Doppler_phase_cur * I);
rx_tmp.r = creal(out);
rx_tmp.i = cimag(out);
Doppler_phase_cur += channelDesc->Doppler_phase_inc;
}
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++;
}
channelDesc->Doppler_phase_cur[rxAnt] = Doppler_phase_cur;
if ( (TS*nbTx)%CirSize+nbSamples <= CirSize )
// Cast to a wrong type for compatibility !
LOG_D(HW,"Input power %f, output power: %f, channel path loss %f, noise coeff: %f \n",
10*log10((double)signal_energy((int32_t *)&input_sig[(TS*nbTx)%CirSize], nbSamples)),
10*log10((double)signal_energy((int32_t *)after_channel_sig, nbSamples)),
channelDesc->path_loss_dB,
10*log10(noise_per_sample));
}
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