-// commradio.cxx -- implementation of FGCommRadio
+// radio.cxx -- implementation of FGRadio
// Class to manage radio propagation using the ITM model
// Written by Adrian Musceac, started August 2011.
//
#endif
#include <math.h>
+
#include <stdlib.h>
#include <deque>
-
+#include "radio.hxx"
+#include <simgear/scene/material/mat.hxx>
#include <Scenery/scenery.hxx>
#define WITH_POINT_TO_POINT 1
#include "itm.cpp"
-FGRadio::FGRadio() {
+FGRadioTransmission::FGRadioTransmission() {
+
- /////////// radio parameters ///////////
_receiver_sensitivity = -110.0; // typical AM receiver sensitivity seems to be 0.8 microVolt at 12dB SINAD
- // AM transmitter power in dBm.
- // Note this value is calculated from the typical final transistor stage output
- // !!! small aircraft have portable transmitters which operate at 36 dBm output (4 Watts)
- // later store this value in aircraft description
- // ATC comms usually operate high power equipment, thus making the link asymetrical; this is ignored for now
+
+ /** AM transmitter power in dBm.
+ * Typical output powers for ATC ground equipment, VHF-UHF:
+ * 40 dBm - 10 W (ground, clearance)
+ * 44 dBm - 20 W (tower)
+ * 47 dBm - 50 W (center, sectors)
+ * 50 dBm - 100 W (center, sectors)
+ * 53 dBm - 200 W (sectors, on directional arrays)
+ **/
_transmitter_power = 43.0;
- //pilot plane's antenna gain + AI aircraft antenna gain
- //real-life gain for conventional monopole/dipole antenna
- _antenna_gain = 2.0;
- _propagation_model = 2; // choose between models via option: realistic radio on/off
+ _tx_antenna_height = 2.0; // TX antenna height above ground level
+
+ _rx_antenna_height = 2.0; // RX antenna height above ground level
+
+
+ _rx_antenna_gain = 1.0; // gain expressed in dBi
+ _tx_antenna_gain = 1.0;
+
+ _rx_line_losses = 2.0; // to be configured for each station
+ _tx_line_losses = 2.0;
+
+ _polarization = 1; // default vertical
+
+ _propagation_model = 2;
+ _terrain_sampling_distance = fgGetDouble("/sim/radio/sampling-distance", 90.0); // regular SRTM is 90 meters
}
-FGRadio::~FGRadio()
+FGRadioTransmission::~FGRadioTransmission()
{
}
-double FGRadio::getFrequency(int radio) {
+double FGRadioTransmission::getFrequency(int radio) {
double freq = 118.0;
switch (radio) {
case 1:
return freq;
}
+/*** TODO: receive multiplayer chat message and voice
+***/
+void FGRadioTransmission::receiveChat(SGGeod tx_pos, double freq, string text, int ground_to_air) {
+}
+
+/*** TODO: receive navaid
+***/
+double FGRadioTransmission::receiveNav(SGGeod tx_pos, double freq, int transmission_type) {
+
+ // typical VOR/LOC transmitter power appears to be 200 Watt ~ 53 dBm
+ // vor/loc typical sensitivity between -107 and -101 dBm
+ // glideslope sensitivity between -85 and -81 dBm
+ if ( _propagation_model == 1) {
+ return LOS_calculate_attenuation(tx_pos, freq, 1);
+ }
+ else if ( _propagation_model == 2) {
+ return ITM_calculate_attenuation(tx_pos, freq, 1);
+ }
+
+ return -1;
+}
-void FGRadio::receiveText(SGGeod tx_pos, double freq, string text,
- int ground_to_air) {
+/*** Receive ATC radio communication as text
+***/
+void FGRadioTransmission::receiveATC(SGGeod tx_pos, double freq, string text, int ground_to_air) {
+
+ if(ground_to_air == 1) {
+ _transmitter_power += 6.0;
+ _tx_antenna_height += 30.0;
+ _tx_antenna_gain += 3.0;
+ }
+
+
double comm1 = getFrequency(1);
double comm2 = getFrequency(2);
- if ( (freq != comm1) && (freq != comm2) ) {
+ if ( !(fabs(freq - comm1) <= 0.0001) && !(fabs(freq - comm2) <= 0.0001) ) {
return;
}
else {
- double signal = ITM_calculate_attenuation(tx_pos, freq, ground_to_air);
- if (signal <= 0)
- return;
- if ((signal > 0) && (signal < 12)) {
- //for low SNR values implement a way to make the conversation
- //hard to understand but audible
- //how this works in the real world, is the receiver AGC fails to capture the slope
- //and the signal, due to being amplitude modulated, decreases volume after demodulation
- //the implementation below is more akin to what would happen on a FM transmission
- //therefore the correct way would be to work on the volume
- /*
- string hash_noise = " ";
- int reps = fabs((int)signal - 11);
- int t_size = text.size();
- for (int n=1;n<=reps * 2;n++) {
- int pos = rand() % t_size -1;
- text.replace(pos,1, hash_noise);
+
+ if ( _propagation_model == 0) {
+ fgSetString("/sim/messages/atc", text.c_str());
+ }
+ else if ( _propagation_model == 1 ) {
+ // TODO: free space, round earth
+ double signal = LOS_calculate_attenuation(tx_pos, freq, ground_to_air);
+ if (signal <= 0.0) {
+ return;
+ }
+ else {
+
+ fgSetString("/sim/messages/atc", text.c_str());
+ /** write signal strength above threshold to the property tree
+ * to implement a simple S-meter just divide by 3 dB per grade (VHF norm)
+ **/
+ fgSetDouble("/sim/radio/comm1-signal", signal);
+ }
+ }
+ else if ( _propagation_model == 2 ) {
+ // Use ITM propagation model
+ double signal = ITM_calculate_attenuation(tx_pos, freq, ground_to_air);
+ if (signal <= 0.0) {
+ return;
+ }
+ if ((signal > 0.0) && (signal < 12.0)) {
+ /** for low SNR values implement a way to make the conversation
+ * hard to understand but audible
+ * in the real world, the receiver AGC fails to capture the slope
+ * and the signal, due to being amplitude modulated, decreases volume after demodulation
+ * the workaround below is more akin to what would happen on a FM transmission
+ * therefore the correct way would be to work on the volume
+ **/
+ /*
+ string hash_noise = " ";
+ int reps = (int) (fabs(floor(signal - 11.0)) * 2);
+ int t_size = text.size();
+ for (int n = 1; n <= reps; ++n) {
+ int pos = rand() % (t_size -1);
+ text.replace(pos,1, hash_noise);
+ }
+ */
+ double volume = (fabs(signal - 12.0) / 12);
+ double old_volume = fgGetDouble("/sim/sound/voices/voice/volume");
+ SG_LOG(SG_GENERAL, SG_BULK, "Usable signal at limit: " << signal);
+ //cerr << "Usable signal at limit: " << signal << endl;
+ fgSetDouble("/sim/sound/voices/voice/volume", volume);
+ fgSetString("/sim/messages/atc", text.c_str());
+ fgSetDouble("/sim/radio/comm1-signal", signal);
+ fgSetDouble("/sim/sound/voices/voice/volume", old_volume);
+ }
+ else {
+ fgSetString("/sim/messages/atc", text.c_str());
+ /** write signal strength above threshold to the property tree
+ * to implement a simple S-meter just divide by 3 dB per grade (VHF norm)
+ **/
+ fgSetDouble("/sim/radio/comm1-signal", signal);
}
- */
}
- fgSetString("/sim/messages/atc", text.c_str());
+
}
}
-double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq,
- int transmission_type) {
+/*** Implement radio attenuation
+ based on the Longley-Rice propagation model
+***/
+double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, int transmission_type) {
- /// Implement radio attenuation
- /// based on the Longley-Rice propagation model
- ////////////// ITM default parameters //////////////
- // in the future perhaps take them from tile materials?
+
+ /** ITM default parameters
+ TODO: take them from tile materials (especially for sea)?
+ **/
double eps_dielect=15.0;
double sgm_conductivity = 0.005;
double eno = 301.0;
else
frq_mhz = freq;
int radio_climate = 5; // continental temperate
- int pol=1; // assuming vertical polarization although this is more complex in reality
+ int pol= _polarization;
double conf = 0.90; // 90% of situations and time, take into account speed
double rel = 0.90;
double dbloss;
char strmode[150];
+ int p_mode = 0; // propgation mode selector: 0 LOS, 1 diffraction dominant, 2 troposcatter
+ double horizons[2];
int errnum;
- double tx_pow,ant_gain;
+ double clutter_loss = 0.0; // loss due to vegetation and urban
+ double tx_pow = _transmitter_power;
+ double ant_gain = _rx_antenna_gain + _tx_antenna_gain;
double signal = 0.0;
- if(transmission_type == 1)
- tx_pow = _transmitter_power + 6.0;
-
- if((transmission_type == 1) || (transmission_type == 3))
- ant_gain = _antenna_gain + 3.0; //pilot plane's antenna gain + ground station antenna gain
- double link_budget = tx_pow - _receiver_sensitivity + ant_gain;
+ double link_budget = tx_pow - _receiver_sensitivity - _rx_line_losses - _tx_line_losses + ant_gain;
FGScenery * scenery = globals->get_scenery();
SGGeoc center = SGGeoc::fromGeod( max_own_pos );
SGGeoc own_pos_c = SGGeoc::fromGeod( own_pos );
- // position of sender radio antenna (HAAT)
- // sender can be aircraft or ground station
- double ATC_HAAT = 30.0;
- double Aircraft_HAAT = 5.0;
+
double sender_alt_ft,sender_alt;
double transmitter_height=0.0;
double receiver_height=0.0;
SGGeoc sender_pos_c = SGGeoc::fromGeod( sender_pos );
//cerr << "ITM:: sender Lat: " << parent->getLatitude() << ", Lon: " << parent->getLongitude() << ", Alt: " << sender_alt << endl;
- double point_distance= 90.0; // regular SRTM is 90 meters
+ double point_distance= _terrain_sampling_distance;
double course = SGGeodesy::courseRad(own_pos_c, sender_pos_c);
double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
double probe_distance = 0.0;
- // If distance larger than this value (300 km), assume reception imposssible
+ /** If distance larger than this value (300 km), assume reception imposssible */
if (distance_m > 300000)
return -1.0;
- // If above 9000, consider LOS mode and calculate free-space att
- if (own_alt > 9000) {
+ /** If above 8000 meters, consider LOS mode and calculate free-space att */
+ if (own_alt > 8000) {
dbloss = 20 * log10(distance_m) +20 * log10(frq_mhz) -27.55;
+ SG_LOG(SG_GENERAL, SG_BULK,
+ "ITM Free-space mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation");
+ //cerr << "ITM Free-space mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation" << endl;
signal = link_budget - dbloss;
return signal;
}
- double max_points = distance_m / point_distance;
+ int max_points = (int)floor(distance_m / point_distance);
+ double delta_last = fmod(distance_m, point_distance);
+
deque<double> _elevations;
+ deque<string> materials;
+
double elevation_under_pilot = 0.0;
if (scenery->get_elevation_m( max_own_pos, elevation_under_pilot, NULL )) {
- receiver_height = own_alt - elevation_under_pilot + 3; //assume antenna located 3 meters above ground
+ receiver_height = own_alt - elevation_under_pilot;
}
double elevation_under_sender = 0.0;
transmitter_height = sender_alt;
}
- if(transmission_type == 1)
- transmitter_height += ATC_HAAT;
- else
- transmitter_height += Aircraft_HAAT;
- cerr << "ITM:: RX-height: " << receiver_height << ", TX-height: " << transmitter_height << ", Distance: " << distance_m << endl;
+ transmitter_height += _tx_antenna_height;
+ receiver_height += _rx_antenna_height;
+
+
+ SG_LOG(SG_GENERAL, SG_BULK,
+ "ITM:: RX-height: " << receiver_height << " meters, TX-height: " << transmitter_height << " meters, Distance: " << distance_m << " meters");
+ cerr << "ITM:: RX-height: " << receiver_height << " meters, TX-height: " << transmitter_height << " meters, Distance: " << distance_m << " meters" << endl;
unsigned int e_size = (deque<unsigned>::size_type)max_points;
while (_elevations.size() <= e_size) {
probe_distance += point_distance;
SGGeod probe = SGGeod::fromGeoc(center.advanceRadM( course, probe_distance ));
-
+ const SGMaterial *mat = 0;
double elevation_m = 0.0;
- if (scenery->get_elevation_m( probe, elevation_m, NULL )) {
+ if (scenery->get_elevation_m( probe, elevation_m, &mat )) {
if((transmission_type == 3) || (transmission_type == 4)) {
_elevations.push_back(elevation_m);
+ if(mat) {
+ const std::vector<string> mat_names = mat->get_names();
+ materials.push_back(mat_names[0]);
+ }
+ else {
+ materials.push_back("None");
+ }
}
else {
_elevations.push_front(elevation_m);
+ if(mat) {
+ const std::vector<string> mat_names = mat->get_names();
+ materials.push_front(mat_names[0]);
+ }
+ else {
+ materials.push_front("None");
+ }
}
}
else {
if((transmission_type == 3) || (transmission_type == 4)) {
- _elevations.push_back(elevation_m);
+ _elevations.push_back(0.0);
+ materials.push_back("None");
}
else {
- _elevations.push_front(0.0);
+ _elevations.push_front(0.0);
+ materials.push_front("None");
}
}
}
if((transmission_type == 3) || (transmission_type == 4)) {
_elevations.push_front(elevation_under_pilot);
- _elevations.push_back(elevation_under_sender);
+ if (delta_last > (point_distance / 2) ) // only add last point if it's farther than half point_distance
+ _elevations.push_back(elevation_under_sender);
}
else {
_elevations.push_back(elevation_under_pilot);
- _elevations.push_front(elevation_under_sender);
+ if (delta_last > (point_distance / 2) )
+ _elevations.push_front(elevation_under_sender);
}
}
double num_points= (double)_elevations.size();
- //cerr << "ITM:: Max alt between: " << max_alt_between << ", num points:" << num_points << endl;
+
_elevations.push_front(point_distance);
_elevations.push_front(num_points -1);
int size = _elevations.size();
//cerr << "ITM:: itm_elev: " << _elevations[i] << endl;
}
-
- // first Fresnel zone radius
- // frequency in the middle of the bandplan, more accuracy is not necessary
- double fz_clr= 8.657 * sqrt(distance_m / 0.125);
-
- // TODO: If we clear the first Fresnel zone, we are into line of sight teritory
-
- // else we need to calculate point to point link loss
if((transmission_type == 3) || (transmission_type == 4)) {
// the sender and receiver roles are switched
point_to_point(itm_elev, receiver_height, transmitter_height,
eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
- pol, conf, rel, dbloss, strmode, errnum);
-
+ pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
+ if( fgGetBool( "/sim/radio/use-clutter-attenuation", false ) )
+ clutterLoss(frq_mhz, distance_m, itm_elev, materials, receiver_height, transmitter_height, p_mode, horizons, clutter_loss);
}
else {
-
point_to_point(itm_elev, transmitter_height, receiver_height,
eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
- pol, conf, rel, dbloss, strmode, errnum);
+ pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
+ if( fgGetBool( "/sim/radio/use-clutter-attenuation", false ) )
+ clutterLoss(frq_mhz, distance_m, itm_elev, materials, transmitter_height, receiver_height, p_mode, horizons, clutter_loss);
}
-
+ SG_LOG(SG_GENERAL, SG_BULK,
+ "ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum);
cerr << "ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum << endl;
- //if (errnum == 4)
+ cerr << "Clutter loss: " << clutter_loss << endl;
+ //if (errnum == 4) // if parameters are outside sane values for lrprop, the alternative method is used
// return -1;
- signal = link_budget - dbloss;
+ signal = link_budget - dbloss - clutter_loss;
return signal;
}
+
+/*** Calculate losses due to vegetation and urban clutter (WIP)
+* We are only worried about clutter loss, terrain influence
+* on the first Fresnel zone is calculated in the ITM functions
+***/
+void FGRadioTransmission::clutterLoss(double freq, double distance_m, double itm_elev[], deque<string> materials,
+ double transmitter_height, double receiver_height, int p_mode,
+ double horizons[], double &clutter_loss) {
+
+ distance_m = itm_elev[0] * itm_elev[1]; // only consider elevation points
+
+ if (p_mode == 0) { // LOS: take each point and see how clutter height affects first Fresnel zone
+ int mat = 0;
+ int j=1;
+ for (int k=3;k < (int)(itm_elev[0]) + 2;k++) {
+
+ double clutter_height = 0.0; // mean clutter height for a certain terrain type
+ double clutter_density = 0.0; // percent of reflected wave
+ get_material_properties(materials[mat], clutter_height, clutter_density);
+
+ double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
+ // First Fresnel radius
+ double frs_rad = 548 * sqrt( (j * itm_elev[1] * (itm_elev[0] - j) * itm_elev[1] / 1000000) / ( distance_m * freq / 1000) );
+
+ //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
+
+ double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
+ double d1 = j * itm_elev[1];
+ if ((itm_elev[2] + transmitter_height) > ( itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
+ d1 = (itm_elev[0] - j) * itm_elev[1];
+ }
+ double ray_height = (grad * d1) + min_elev;
+
+ double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
+ double intrusion = fabs(clearance);
+
+ if (clearance >= 0) {
+ // no losses
+ }
+ else if (clearance < 0 && (intrusion < clutter_height)) {
+
+ clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else if (clearance < 0 && (intrusion > clutter_height)) {
+ clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else {
+ // no losses
+ }
+ j++;
+ mat++;
+ }
+
+ }
+ else if (p_mode == 1) { // diffraction
+
+ if (horizons[1] == 0.0) { // single horizon: same as above, except pass twice using the highest point
+ int num_points_1st = (int)floor( horizons[0] * itm_elev[0]/ distance_m );
+ int num_points_2nd = (int)ceil( (distance_m - horizons[0]) * itm_elev[0] / distance_m );
+ //cerr << "Diffraction 1 horizon:: points1: " << num_points_1st << " points2: " << num_points_2nd << endl;
+ int last = 1;
+ /** perform the first pass */
+ int mat = 0;
+ int j=1;
+ for (int k=3;k < num_points_1st + 2;k++) {
+ if (num_points_1st < 1)
+ break;
+ double clutter_height = 0.0; // mean clutter height for a certain terrain type
+ double clutter_density = 0.0; // percent of reflected wave
+ get_material_properties(materials[mat], clutter_height, clutter_density);
+
+ double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[num_points_1st + 2] + clutter_height) / distance_m;
+ // First Fresnel radius
+ double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_1st - j) * itm_elev[1] / 1000000) / ( num_points_1st * itm_elev[1] * freq / 1000) );
+
+ //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
+
+ double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[num_points_1st + 2] + clutter_height);
+ double d1 = j * itm_elev[1];
+ if ( (itm_elev[2] + transmitter_height) > (itm_elev[num_points_1st + 2] + clutter_height) ) {
+ d1 = (num_points_1st - j) * itm_elev[1];
+ }
+ double ray_height = (grad * d1) + min_elev;
+
+ double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
+ double intrusion = fabs(clearance);
+
+ if (clearance >= 0) {
+ // no losses
+ }
+ else if (clearance < 0 && (intrusion < clutter_height)) {
+
+ clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else if (clearance < 0 && (intrusion > clutter_height)) {
+ clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else {
+ // no losses
+ }
+ j++;
+ mat++;
+ last = k;
+ }
+
+ /** and the second pass */
+ mat +=1;
+ j =1; // first point is diffraction edge, 2nd the RX elevation
+ for (int k=last+2;k < (int)(itm_elev[0]) + 2;k++) {
+ if (num_points_2nd < 1)
+ break;
+ double clutter_height = 0.0; // mean clutter height for a certain terrain type
+ double clutter_density = 0.0; // percent of reflected wave
+ get_material_properties(materials[mat], clutter_height, clutter_density);
+
+ double grad = fabs(itm_elev[last+1] + clutter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
+ // First Fresnel radius
+ double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_2nd - j) * itm_elev[1] / 1000000) / ( num_points_2nd * itm_elev[1] * freq / 1000) );
+
+ //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
+
+ double min_elev = SGMiscd::min(itm_elev[last+1] + clutter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
+ double d1 = j * itm_elev[1];
+ if ( (itm_elev[last+1] + clutter_height) > (itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
+ d1 = (num_points_2nd - j) * itm_elev[1];
+ }
+ double ray_height = (grad * d1) + min_elev;
+
+ double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
+ double intrusion = fabs(clearance);
+
+ if (clearance >= 0) {
+ // no losses
+ }
+ else if (clearance < 0 && (intrusion < clutter_height)) {
+
+ clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else if (clearance < 0 && (intrusion > clutter_height)) {
+ clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else {
+ // no losses
+ }
+ j++;
+ mat++;
+ }
+
+ }
+ else { // double horizon: same as single horizon, except there are 3 segments
+
+ int num_points_1st = (int)floor( horizons[0] * itm_elev[0] / distance_m );
+ int num_points_2nd = (int)floor(horizons[1] * itm_elev[0] / distance_m );
+ int num_points_3rd = (int)itm_elev[0] - num_points_1st - num_points_2nd;
+ //cerr << "Double horizon:: horizon1: " << horizons[0] << " horizon2: " << horizons[1] << " distance: " << distance_m << endl;
+ //cerr << "Double horizon:: points1: " << num_points_1st << " points2: " << num_points_2nd << " points3: " << num_points_3rd << endl;
+ int last = 1;
+ /** perform the first pass */
+ int mat = 0;
+ int j=1; // first point is TX elevation, 2nd is obstruction elevation
+ for (int k=3;k < num_points_1st +2;k++) {
+ if (num_points_1st < 1)
+ break;
+ double clutter_height = 0.0; // mean clutter height for a certain terrain type
+ double clutter_density = 0.0; // percent of reflected wave
+ get_material_properties(materials[mat], clutter_height, clutter_density);
+
+ double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[num_points_1st + 2] + clutter_height) / distance_m;
+ // First Fresnel radius
+ double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_1st - j) * itm_elev[1] / 1000000) / ( num_points_1st * itm_elev[1] * freq / 1000) );
+
+ //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
+
+ double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[num_points_1st + 2] + clutter_height);
+ double d1 = j * itm_elev[1];
+ if ( (itm_elev[2] + transmitter_height) > (itm_elev[num_points_1st + 2] + clutter_height) ) {
+ d1 = (num_points_1st - j) * itm_elev[1];
+ }
+ double ray_height = (grad * d1) + min_elev;
+
+ double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
+ double intrusion = fabs(clearance);
+
+ if (clearance >= 0) {
+ // no losses
+ }
+ else if (clearance < 0 && (intrusion < clutter_height)) {
+
+ clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else if (clearance < 0 && (intrusion > clutter_height)) {
+ clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else {
+ // no losses
+ }
+ j++;
+ last = k;
+ }
+ mat +=1;
+ /** and the second pass */
+ int last2=1;
+ j =1; // first point is 1st obstruction elevation, 2nd is 2nd obstruction elevation
+ for (int k=last+2;k < num_points_1st + num_points_2nd +2;k++) {
+ if (num_points_2nd < 1)
+ break;
+ double clutter_height = 0.0; // mean clutter height for a certain terrain type
+ double clutter_density = 0.0; // percent of reflected wave
+ get_material_properties(materials[mat], clutter_height, clutter_density);
+
+ double grad = fabs(itm_elev[last+1] + clutter_height - itm_elev[num_points_1st + num_points_2nd + 2] + clutter_height) / distance_m;
+ // First Fresnel radius
+ double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_2nd - j) * itm_elev[1] / 1000000) / ( num_points_2nd * itm_elev[1] * freq / 1000) );
+
+ //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
+
+ double min_elev = SGMiscd::min(itm_elev[last+1] + clutter_height, itm_elev[num_points_1st + num_points_2nd +2] + clutter_height);
+ double d1 = j * itm_elev[1];
+ if ( (itm_elev[last+1] + clutter_height) > (itm_elev[num_points_1st + num_points_2nd + 2] + clutter_height) ) {
+ d1 = (num_points_2nd - j) * itm_elev[1];
+ }
+ double ray_height = (grad * d1) + min_elev;
+
+ double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
+ double intrusion = fabs(clearance);
+
+ if (clearance >= 0) {
+ // no losses
+ }
+ else if (clearance < 0 && (intrusion < clutter_height)) {
+
+ clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else if (clearance < 0 && (intrusion > clutter_height)) {
+ clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else {
+ // no losses
+ }
+ j++;
+ mat++;
+ last2 = k;
+ }
+
+ /** third and final pass */
+ mat +=1;
+ j =1; // first point is 2nd obstruction elevation, 3rd is RX elevation
+ for (int k=last2+2;k < (int)itm_elev[0] + 2;k++) {
+ if (num_points_3rd < 1)
+ break;
+ double clutter_height = 0.0; // mean clutter height for a certain terrain type
+ double clutter_density = 0.0; // percent of reflected wave
+ get_material_properties(materials[mat], clutter_height, clutter_density);
+
+ double grad = fabs(itm_elev[last2+1] + clutter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
+ // First Fresnel radius
+ double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_3rd - j) * itm_elev[1] / 1000000) / ( num_points_3rd * itm_elev[1] * freq / 1000) );
+
+
+ //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
+
+ double min_elev = SGMiscd::min(itm_elev[last2+1] + clutter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
+ double d1 = j * itm_elev[1];
+ if ( (itm_elev[last2+1] + clutter_height) > (itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
+ d1 = (num_points_3rd - j) * itm_elev[1];
+ }
+ double ray_height = (grad * d1) + min_elev;
+
+ double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
+ double intrusion = fabs(clearance);
+
+ if (clearance >= 0) {
+ // no losses
+ }
+ else if (clearance < 0 && (intrusion < clutter_height)) {
+
+ clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else if (clearance < 0 && (intrusion > clutter_height)) {
+ clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
+ }
+ else {
+ // no losses
+ }
+ j++;
+ mat++;
+
+ }
+
+ }
+ }
+ else if (p_mode == 2) { // troposcatter: ignore ground clutter for now...
+ clutter_loss = 0.0;
+ }
+
+}
+
+/*** Temporary material properties database
+* height: median clutter height
+* density: radiowave attenuation factor
+***/
+void FGRadioTransmission::get_material_properties(string mat_name, double &height, double &density) {
+
+ if(mat_name == "Landmass") {
+ height = 15.0;
+ density = 0.2;
+ }
+
+ else if(mat_name == "SomeSort") {
+ height = 15.0;
+ density = 0.2;
+ }
+
+ else if(mat_name == "Island") {
+ height = 15.0;
+ density = 0.2;
+ }
+ else if(mat_name == "Default") {
+ height = 15.0;
+ density = 0.2;
+ }
+ else if(mat_name == "EvergreenBroadCover") {
+ height = 20.0;
+ density = 0.2;
+ }
+ else if(mat_name == "EvergreenForest") {
+ height = 20.0;
+ density = 0.2;
+ }
+ else if(mat_name == "DeciduousBroadCover") {
+ height = 15.0;
+ density = 0.3;
+ }
+ else if(mat_name == "DeciduousForest") {
+ height = 15.0;
+ density = 0.3;
+ }
+ else if(mat_name == "MixedForestCover") {
+ height = 20.0;
+ density = 0.25;
+ }
+ else if(mat_name == "MixedForest") {
+ height = 15.0;
+ density = 0.25;
+ }
+ else if(mat_name == "RainForest") {
+ height = 25.0;
+ density = 0.55;
+ }
+ else if(mat_name == "EvergreenNeedleCover") {
+ height = 15.0;
+ density = 0.2;
+ }
+ else if(mat_name == "WoodedTundraCover") {
+ height = 5.0;
+ density = 0.15;
+ }
+ else if(mat_name == "DeciduousNeedleCover") {
+ height = 5.0;
+ density = 0.2;
+ }
+ else if(mat_name == "ScrubCover") {
+ height = 3.0;
+ density = 0.15;
+ }
+ else if(mat_name == "BuiltUpCover") {
+ height = 30.0;
+ density = 0.7;
+ }
+ else if(mat_name == "Urban") {
+ height = 30.0;
+ density = 0.7;
+ }
+ else if(mat_name == "Construction") {
+ height = 30.0;
+ density = 0.7;
+ }
+ else if(mat_name == "Industrial") {
+ height = 30.0;
+ density = 0.7;
+ }
+ else if(mat_name == "Port") {
+ height = 30.0;
+ density = 0.7;
+ }
+ else if(mat_name == "Town") {
+ height = 10.0;
+ density = 0.5;
+ }
+ else if(mat_name == "SubUrban") {
+ height = 10.0;
+ density = 0.5;
+ }
+ else if(mat_name == "CropWoodCover") {
+ height = 10.0;
+ density = 0.1;
+ }
+ else if(mat_name == "CropWood") {
+ height = 10.0;
+ density = 0.1;
+ }
+ else if(mat_name == "AgroForest") {
+ height = 10.0;
+ density = 0.1;
+ }
+ else {
+ height = 0.0;
+ density = 0.0;
+ }
+
+}
+
+/*** implement simple LOS propagation model (WIP)
+***/
+double FGRadioTransmission::LOS_calculate_attenuation(SGGeod pos, double freq, int transmission_type) {
+ double frq_mhz;
+ if( (freq < 118.0) || (freq > 137.0) )
+ frq_mhz = 125.0; // sane value, middle of bandplan
+ else
+ frq_mhz = freq;
+ double dbloss;
+ double tx_pow = _transmitter_power;
+ double ant_gain = _rx_antenna_gain + _tx_antenna_gain;
+ double signal = 0.0;
+
+ double sender_alt_ft,sender_alt;
+ double transmitter_height=0.0;
+ double receiver_height=0.0;
+ double own_lat = fgGetDouble("/position/latitude-deg");
+ double own_lon = fgGetDouble("/position/longitude-deg");
+ double own_alt_ft = fgGetDouble("/position/altitude-ft");
+ double own_alt= own_alt_ft * SG_FEET_TO_METER;
+
+
+ double link_budget = tx_pow - _receiver_sensitivity - _rx_line_losses - _tx_line_losses + ant_gain;
+
+ //cerr << "ITM:: pilot Lat: " << own_lat << ", Lon: " << own_lon << ", Alt: " << own_alt << endl;
+
+ SGGeod own_pos = SGGeod::fromDegM( own_lon, own_lat, own_alt );
+
+ SGGeod sender_pos = pos;
+
+ sender_alt_ft = sender_pos.getElevationFt();
+ sender_alt = sender_alt_ft * SG_FEET_TO_METER;
+
+ receiver_height = own_alt;
+ transmitter_height = sender_alt;
+
+ double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
+
+
+ transmitter_height += _tx_antenna_height;
+ receiver_height += _rx_antenna_height;
+
+
+ /** radio horizon calculation with wave bending k=4/3 */
+ double receiver_horizon = 4.12 * sqrt(receiver_height);
+ double transmitter_horizon = 4.12 * sqrt(transmitter_height);
+ double total_horizon = receiver_horizon + transmitter_horizon;
+
+ if (distance_m > total_horizon) {
+ return -1;
+ }
+
+ // free-space loss (distance calculation should be changed)
+ dbloss = 20 * log10(distance_m) +20 * log10(frq_mhz) -27.55;
+ signal = link_budget - dbloss;
+ SG_LOG(SG_GENERAL, SG_BULK,
+ "LOS:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm ");
+ //cerr << "LOS:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm " << endl;
+ return signal;
+
+}
+
+
projects / flightgear.git / blobdiff