FGRadio::FGRadio() {
- /////////// radio parameters ///////////
+ /** radio parameters (which should probably be set for each radio via constructor) */
_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.
+ * 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
+ **/
_transmitter_power = 43.0;
- //pilot plane's antenna gain + AI aircraft antenna gain
- //real-life gain for conventional monopole/dipole antenna
+
+ /** 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
}
else {
*/
- double signal = ITM_calculate_attenuation(tx_pos, freq, ground_to_air);
- //cerr << "Signal: " << signal << endl;
- if (signal <= 0.0) {
- //cerr << "Signal below sensitivity: " << signal << " dBm" << endl;
- return;
- }
- if ((signal > 0.0) && (signal < 12.0)) {
- //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 = (int) (fabs(floor(signal - 11.0)) * 2);
- //cerr << "Reps: " << reps << endl;
- int t_size = text.size();
- for (int n = 1; n <= reps; ++n) {
- int pos = rand() % (t_size -1);
- //cerr << "Pos: " << pos << endl;
- text.replace(pos,1, hash_noise);
- }
- */
- double volume = (fabs(signal - 12.0) / 12);
- double old_volume = fgGetDouble("/sim/sound/voices/voice/volume");
- //cerr << "Usable signal at limit: " << signal << endl;
- fgSetDouble("/sim/sound/voices/voice/volume", volume);
+ if ( _propagation_model == 0) {
fgSetString("/sim/messages/atc", text.c_str());
- fgSetDouble("/sim/sound/voices/voice/volume", old_volume);
}
- else {
- //cerr << "Signal completely readable: " << signal << " dBm" << endl;
- fgSetString("/sim/messages/atc", text.c_str());
+ else if ( _propagation_model == 1 ) {
+ // free space, round earth
+ }
+ else if ( _propagation_model == 2 ) {
+ // Use ITM propagation model
+ double signal = ITM_calculate_attenuation(tx_pos, freq, ground_to_air);
+ if (signal <= 0.0) {
+ SG_LOG(SG_GENERAL, SG_BULK, "Signal below receiver minimum sensitivity: " << signal);
+ //cerr << "Signal below receiver minimum sensitivity: " << signal << endl;
+ 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/sound/voices/voice/volume", old_volume);
+ }
+ else {
+ SG_LOG(SG_GENERAL, SG_BULK, "Signal completely readable: " << signal);
+ //cerr << "Signal completely readable: " << signal << endl;
+ fgSetString("/sim/messages/atc", text.c_str());
+ }
+
}
//}
}
+/*** Implement radio attenuation
+ based on the Longley-Rice propagation model
+***/
double FGRadio::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;
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
+ /** 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 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 8000, consider LOS mode and calculate free-space att
+ /** 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;
- cerr << "LOS-mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation" << endl;
+ SG_LOG(SG_GENERAL, SG_BULK,
+ "LOS-mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation");
+ //cerr << "LOS-mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation" << endl;
signal = link_budget - dbloss;
return signal;
}
else
transmitter_height += Aircraft_HAAT;
+ 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;
}
- // first Fresnel zone radius
- // frequency in the middle of the bandplan, more accuracy is not necessary
+ /** 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 territory
eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
pol, conf, rel, dbloss, strmode, errnum);
}
-
+ 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)
+ //if (errnum == 4) // if parameters are outside sane values for lrprop, the alternative method is used
// return -1;
signal = link_budget - dbloss;
return signal;
projects / flightgear.git / commitdiff