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rfsimulator: add delay and Doppler simulation for circular orbit and add according channel models SAT_LEO_TRANS and SAT_LEO_REGEN

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Delay and Doppler computation is done as in Matlab function dopplerShiftCircularOrbit:
https://de.mathworks.com/help/satcom/ref/dopplershiftcircularorbit.html
This commit is contained in:
Thomas Schlichter
2024-08-20 16:46:25 +02:00
parent 68b07d542c
commit 6a8edaf317
4 changed files with 149 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openair1/SIMULATION/TOOLS/random_channel.c
+37 -2
View File
@@ -128,6 +128,7 @@ void fill_channel_desc(channel_desc_t *chan_desc,
chan_desc->first_run = 1;
chan_desc->ip = 0.0;
chan_desc->max_Doppler = max_Doppler;
chan_desc->Doppler_phase_cur = calloc(nb_rx, sizeof(double));
chan_desc->ch = calloc(nb_tx*nb_rx, sizeof(struct complexd *));
chan_desc->chF = calloc(nb_tx*nb_rx, sizeof(struct complexd *));
chan_desc->a = calloc(nb_taps, sizeof(struct complexd *));
@@ -1653,6 +1654,37 @@ channel_desc_t *new_channel_desc_scm(uint8_t nb_tx,
0);
break;
case SAT_LEO_TRANS:
case SAT_LEO_REGEN:
nb_taps = 1;
Td = 0;
channel_length = 1;
ricean_factor = 0.0;
aoa = 0.0;
maxDoppler = 0;
chan_desc->sat_height = 600e3;
chan_desc->enable_dynamic_delay = true;
chan_desc->enable_dynamic_Doppler = false; // TODO: requires UE to support continuous Doppler estimation, compensation and pre-compensation
fill_channel_desc(chan_desc,nb_tx,
nb_rx,
nb_taps,
channel_length,
default_amp_lin,
NULL,
NULL,
Td,
sampling_rate,
channel_bandwidth,
ricean_factor,
aoa,
forgetting_factor,
maxDoppler,
channel_offset,
path_loss_dB,
0);
printf("%s: satellite orbit height %f km\n", map_int_to_str(channelmod_names, channel_model), chan_desc->sat_height / 1000);
break;
default:
LOG_W(OCM,"channel model not yet supported\n");
free(chan_desc);
@@ -1711,6 +1743,7 @@ void free_channel_desc_scm(channel_desc_t *ch) {
free(ch->R_sqrt[i]);
free(ch->R_sqrt);
free(ch->Doppler_phase_cur);
free(ch->ch);
free(ch->chF);
free(ch->a);
@@ -1743,9 +1776,9 @@ int random_channel(channel_desc_t *desc, uint8_t abstraction_flag) {
struct complexd phase, alpha, beta;
start_meas(&desc->random_channel);
// For AWGN channel, the received signal (Srx) is equal to transmitted signal (Stx) plus noise (N), i.e., Srx = Stx + N,
// For AWGN and SAT_LEO_* channels, the received signal (Srx) is equal to transmitted signal (Stx) plus noise (N), i.e., Srx = Stx + N,
// therefore, the channel matrix is the identity matrix.
if (desc->modelid == AWGN) {
if (desc->modelid == AWGN || desc->modelid == SAT_LEO_TRANS || desc->modelid == SAT_LEO_REGEN) {
for (aarx=0; aarx<desc->nb_rx; aarx++) {
for (aatx = 0; aatx < desc->nb_tx; aatx++) {
desc->ch[aarx+(aatx*desc->nb_rx)][0].r = aarx%desc->nb_tx == aatx ? 1.0 : 0.0;
@@ -2071,6 +2104,8 @@ static void display_channelmodel(channel_desc_t *cd,int debug, telnet_printfunc_
cd->forgetting_factor);
prnt("Initial phase: %lf nb_path: %i \n",
cd->ip, cd->nb_paths);
if (cd->modelid == SAT_LEO_TRANS || cd->modelid == SAT_LEO_REGEN)
prnt("satellite orbit height: %f\n", cd->sat_height);
for (int i=0; i<cd->nb_taps ; i++) {
prnt("taps: %i lin. ampli. : %lf delay: %lf \n",i,cd->amps[i], cd->delays[i]);
openair1/SIMULATION/TOOLS/sim.h
+16
View File
@@ -126,6 +126,18 @@ typedef struct {
char *model_name;
/// flags to properly trigger memory free
unsigned int free_flags;
/// time stamp when the time varying channel emulation starts (when client connected)
uint64_t start_TS;
/// height of LEO satellite
float sat_height;
/// flag to enable dynamic delay simulation for LEO satellite
bool enable_dynamic_delay;
/// flag to enable dynamic Doppler simulation for LEO satellite
bool enable_dynamic_Doppler;
/// Doppler phase increment (might vary over time, e.g. for LEO satellite)
float Doppler_phase_inc;
/// current Doppler phase of each RX antenna (for continuous phase from one block to the next)
float *Doppler_phase_cur;
} channel_desc_t;
typedef struct {
@@ -218,6 +230,8 @@ typedef enum {
EPA_low,
EPA_medium,
EPA_high,
SAT_LEO_TRANS,
SAT_LEO_REGEN,
} SCM_t;
#define CHANNELMOD_MAP_INIT \
{"custom",custom},\
@@ -253,6 +267,8 @@ typedef enum {
{"EPA_low",EPA_low},\
{"EPA_medium",EPA_medium},\
{"EPA_high",EPA_high},\
{"SAT_LEO_TRANS",SAT_LEO_TRANS},\
{"SAT_LEO_REGEN",SAT_LEO_REGEN},\
{NULL, -1}
#define CONFIG_HLP_SNR "Set average SNR in dB (for --siml1 option)\n"
radio/rfsimulator/apply_channelmod.c
+90 -12
View File
@@ -28,7 +28,7 @@
#include <unistd.h>
#include <stdbool.h>
#include <errno.h>
#include <complex.h>
#include <common/utils/assertions.h>
#include <common/utils/LOG/log.h>
@@ -52,14 +52,85 @@
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,
c16_t *after_channel_sig,
int rxAnt,
channel_desc_t *channelDesc,
int nbSamples,
uint64_t TS,
uint32_t CirSize
) {
void rxAddInput(const c16_t *input_sig,
c16_t *after_channel_sig,
int rxAnt,
channel_desc_t *channelDesc,
int nbSamples,
uint64_t TS,
uint32_t CirSize)
{
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 = 6371e3; // 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 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;
double vel_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);
vel_gnb_sat = (vel_sat_x * dir_gnb_sat_x + vel_sat_y * dir_gnb_sat_y + vel_sat_z * dir_gnb_sat_z) / dist_gnb_sat;
}
const double c = 299792458; // m/s
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;
const double f_Doppler_shift_gnb_sat = (-vel_gnb_sat / c) * channelDesc->center_freq;
if (channelDesc->enable_dynamic_Doppler)
channelDesc->Doppler_phase_inc = 2 * M_PI * (f_Doppler_shift_gnb_sat + f_Doppler_shift_sat_ue) / channelDesc->sampling_rate;
static uint64_t last_TS = 0;
if(TS - last_TS >= channelDesc->sampling_rate) {
last_TS = TS;
LOG_I(HW, "Satellite orbit: time %f s, Doppler: gNB->SAT %f kHz, SAT->UE %f kHz, Delay %f ms\n", t, f_Doppler_shift_gnb_sat / 1000, f_Doppler_shift_sat_ue / 1000, prop_delay * 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
@@ -94,9 +165,16 @@ void rxAddInput( const c16_t *input_sig,
} //l
}
// Fixme: lround(), rount(), ... is detected by valgrind as error, not found why
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));
if (channelDesc->Doppler_phase_inc != 0.0) {
double complex in = CMPLX(rx_tmp.r, rx_tmp.i);
double complex out = in * cexp(channelDesc->Doppler_phase_cur[rxAnt] * I);
rx_tmp.r = creal(out);
rx_tmp.i = cimag(out);
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++;
}
radio/rfsimulator/simulator.c
+6
View File
@@ -709,6 +709,10 @@ static bool flushInput(rfsimulator_state_t *t, int timeout, int nsamps_for_initi
samplesVoid[i]=(void *)&v;
rfsimulator_write_internal(t, t->lastWroteTS > 1 ? t->lastWroteTS - 1 : 0, samplesVoid, 1, t->tx_num_channels, 1, false);
buffer_t *b = &t->buf[conn_sock];
if (b->channel_model)
b->channel_model->start_TS = t->lastWroteTS;
} else {
if ( events[nbEv].events & (EPOLLHUP | EPOLLERR | EPOLLRDHUP) ) {
socketError(t,fd);
@@ -761,6 +765,8 @@ static bool flushInput(rfsimulator_state_t *t, int timeout, int nsamps_for_initi
nsamps_for_initial;
LOG_D(HW, "UE got first timestamp: starting at %lu\n", t->nextRxTstamp);
b->trashingPacket=true;
if (b->channel_model)
b->channel_model->start_TS = t->nextRxTstamp;
} else if (b->lastReceivedTS < b->th.timestamp) {
int nbAnt= b->th.nbAnt;