if (snr > 0 && snr < 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)snr - 11);
int t_size = text.size();
double FGATCController::calculate_attenuation(FGTrafficRecord * rec, FGAirportDynamics *parent,
int ground_to_air) {
- //////////////////////////////////////////////////
- /// Implement radio attenuation //
- /// based on the Longley-Rice propagation model//
- //////////////////////////////////////////////////
-
+
+ /// Implement radio attenuation
+ /// based on the Longley-Rice propagation model
+
FGScenery * scenery = globals->get_scenery();
// player aircraft position
double own_lat = fgGetDouble("/position/latitude-deg");
double own_alt_ft = fgGetDouble("/position/altitude-ft");
double own_alt= own_alt_ft * SG_FEET_TO_METER;
- cerr << "ITM:: pilot Lat: " << own_lat << ", Lon: " << own_lon << ", Alt: " << own_alt << endl;
+ //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 max_own_pos = SGGeod::fromDegM( own_lon, own_lat, SG_MAX_ELEVATION_M );
// position of sender radio antenna (HAAT)
// sender can be aircraft or ground station
double ATC_HAAT = 30.0;
- double Aircraft_HAAT = 7.0;
+ double Aircraft_HAAT = 5.0;
double sender_alt_ft,sender_alt;
double transceiver_height=0.0;
double receiver_height=0.0;
SGGeod sender_pos;
+ SGGeod max_sender_pos;
if(ground_to_air) {
sender_alt_ft = parent->getElevation();
- sender_alt = sender_alt_ft * SG_FEET_TO_METER + ATC_HAAT;
+ sender_alt = sender_alt_ft * SG_FEET_TO_METER;
sender_pos= SGGeod::fromDegM( parent->getLongitude(),
parent->getLatitude(), sender_alt );
+ max_sender_pos = SGGeod::fromDegM( parent->getLongitude(),
+ parent->getLatitude(), SG_MAX_ELEVATION_M );
}
else {
sender_alt_ft = rec->getAltitude();
- sender_alt = sender_alt_ft * SG_FEET_TO_METER + Aircraft_HAAT;
+ sender_alt = sender_alt_ft * SG_FEET_TO_METER;
sender_pos= SGGeod::fromDegM( rec->getLongitude(),
rec->getLatitude(), sender_alt );
+ max_sender_pos = SGGeod::fromDegM( rec->getLongitude(),
+ rec->getLatitude(), SG_MAX_ELEVATION_M );
}
SGGeoc sender_pos_c = SGGeoc::fromGeod( sender_pos );
- cerr << "ITM:: sender Lat: " << parent->getLatitude() << ", Lon: " << parent->getLongitude() << ", Alt: " << sender_alt << endl;
+ //cerr << "ITM:: sender Lat: " << parent->getLatitude() << ", Lon: " << parent->getLongitude() << ", Alt: " << sender_alt << endl;
double point_distance= 90.0; // regular SRTM is 90 meters
double course = SGGeodesy::courseRad(own_pos_c, sender_pos_c);
double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
double probe_distance = 0.0;
- cerr << "ITM:: Distance: " << distance_m << endl;
+ //cerr << "ITM:: Distance: " << distance_m << endl;
double max_points = distance_m / point_distance;
deque<double> _elevations;
- SGGeod probe_pilot = SGGeod::fromGeoc(center.advanceRadM( course, 0 ));
+ //SGGeod probe_pilot = SGGeod::fromGeoc(center.advanceRadM( course, 0 ));
+ SGGeod probe_pilot = max_own_pos;
double elevation_under_pilot = 0.0;
if (scenery->get_elevation_m( probe_pilot, elevation_under_pilot, NULL )) {
- receiver_height = own_alt - elevation_under_pilot;
+ receiver_height = own_alt - elevation_under_pilot + 3; //assume antenna located 3 meters above ground
}
- _elevations.push_front(receiver_height);
- SGGeod probe_sender = SGGeod::fromGeoc(center.advanceRadM( course, distance_m ));
+
+ //SGGeod probe_sender = SGGeod::fromGeoc(center.advanceRadM( course, distance_m ));
+ SGGeod probe_sender = max_sender_pos;
double elevation_under_sender = 0.0;
if (scenery->get_elevation_m( probe_sender, elevation_under_sender, NULL )) {
- transceiver_height = sender_alt - elevation_under_sender;
+ transmitter_height = sender_alt - elevation_under_sender;
}
+ if(ground_to_air)
+ transmitter_height += ATC_HAAT;
+ else
+ transmitter_height += Aircraft_HAAT;
+ cerr << "ITM:: RCVhgt: " << receiver_height << ", TRXhgt: " << transmitter_height << endl;
// If distance larger than this value (400 km), assume reception imposssible
// technically 400 km is no problem if LOS conditions exist,
// but we do this to spare resources
unsigned int e_size = (deque<unsigned>::size_type)max_points;
- while (_elevations.size() < e_size) {
+ while (_elevations.size() <= e_size) {
probe_distance += point_distance;
SGGeod probe = SGGeod::fromGeoc(center.advanceRadM( course, probe_distance ));
//cerr << "ITM:: Probe elev: " << elevation_m << endl;
}
}
-
- _elevations.push_front(transceiver_height);
+ _elevations.push_back(elevation_under_pilot);
+ _elevations.push_front(elevation_under_sender);
double max_alt_between=0.0;
for( deque<double>::size_type i = 0; i < _elevations.size(); i++ ) {
if (_elevations[i] > max_alt_between) {
}
double num_points= (double)_elevations.size();
- cerr << "ITM:: Max alt between: " << max_alt_between << ", num points:" << num_points << endl;
+ //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();
double eno = 301.0;
double frq_mhz = 125.0; // middle of bandplan
int radio_climate = 5; // continental temperate
- int pol=1; // assuming vertical polarization
+ int pol=1; // assuming vertical polarization although this is more complex in reality
double conf = 0.90; // my own tests in Radiomobile have worked best with these values
double rel = 0.80; // ^^
double dbloss;
int errnum;
/////////// radio parameters ///////////
- double receiver_sensitivity = -112.0; // typical AM receiver sensitivity in dBm
+ double 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
double transmitter_power = 43.0;
- double antenna_gain = 2.0;
+ double antenna_gain = 2.0; //real-life gain for conventional monopole/dipole antenna
if(ground_to_air)
transmitter_power = 49.0;
else
transmitter_power = 43.0;
if(ground_to_air)
- antenna_gain = 5.0; //pilot plane's antenna gain + Controller antenna gain
+ antenna_gain = 5.0; //pilot plane's antenna gain + ground station antenna gain
else
antenna_gain = 2.0; //pilot plane's antenna gain + AI aircraft antenna gain
double link_budget = transmitter_power - receiver_sensitivity + antenna_gain;
// else we need to calculate point to point link loss
- point_to_point(itm_elev, sender_alt, own_alt,
+ point_to_point(itm_elev, transmitter_height, receiver_height,
eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
pol, conf, rel, dbloss, strmode, errnum);
projects / flightgear.git / commitdiff