Remove hard-coded values wherever possible;
Make most of the station parameters configurable outside the attenuation functions with the ultimate goal of exposing them via the property tree
This commit is contained in:
adrian
parent
0c66ca6785
commit
1c1e954de2
2 changed files with 31 additions and 60 deletions
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@ -23,8 +23,7 @@
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#endif
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#include <math.h>
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#define NDEBUG
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#include <assert.h>
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#include <stdlib.h>
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#include <deque>
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#include "radio.hxx"
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@ -37,15 +36,10 @@
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FGRadioTransmission::FGRadioTransmission() {
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/** radio parameters (which should probably be set for each radio) */
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_receiver_sensitivity = -110.0; // typical AM receiver sensitivity seems to be 0.8 microVolt at 12dB SINAD
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/** AM transmitter power in dBm.
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* Note this value is calculated from the typical final transistor stage output
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* small aircraft have portable transmitters which operate at 36 dBm output (4 Watts) others operate in the range 10-20 W
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* later possibly store this value in aircraft description
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* ATC comms usually operate high power equipment, thus making the link asymetrical; this is taken care of in propagation routines
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* Typical output powers for ATC ground equipment, VHF-UHF:
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* 40 dBm - 10 W (ground, clearance)
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* 44 dBm - 20 W (tower)
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@ -59,18 +53,14 @@ FGRadioTransmission::FGRadioTransmission() {
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_rx_antenna_height = 2.0; // RX antenna height above ground level
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/** pilot plane's antenna gain + AI aircraft antenna gain
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* real-life gain for conventional monopole/dipole antenna
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**/
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_antenna_gain = 2.0;
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_rx_antenna_gain = 1.0;
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_rx_antenna_gain = 1.0; // gain expressed in dBi
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_tx_antenna_gain = 1.0;
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_rx_line_losses = 2.0; // to be configured for each station
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_tx_line_losses = 2.0;
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_propagation_model = 2; // choose between models via option: realistic radio on/off
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_propagation_model = 2;
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_terrain_sampling_distance = fgGetDouble("/sim/radio/sampling-distance", 90.0); // regular SRTM is 90 meters
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}
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@ -124,10 +114,16 @@ double FGRadioTransmission::receiveNav(SGGeod tx_pos, double freq, int transmiss
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void FGRadioTransmission::receiveATC(SGGeod tx_pos, double freq, string text, int ground_to_air) {
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if(ground_to_air == 1) {
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_transmitter_power += 6.0;
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_tx_antenna_height += 30.0;
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_tx_antenna_gain += 3.0;
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}
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double comm1 = getFrequency(1);
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double comm2 = getFrequency(2);
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if ( !(fabs(freq - comm1) <= 0.0001) && !(fabs(freq - comm2) <= 0.0001) ) {
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//cerr << "Frequency not tuned: " << freq << " Radio1: " << comm1 << " Radio2: " << comm2 << endl;
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return;
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}
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else {
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@ -139,13 +135,10 @@ void FGRadioTransmission::receiveATC(SGGeod tx_pos, double freq, string text, in
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// TODO: free space, round earth
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double signal = LOS_calculate_attenuation(tx_pos, freq, ground_to_air);
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if (signal <= 0.0) {
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SG_LOG(SG_GENERAL, SG_BULK, "Signal below receiver minimum sensitivity: " << signal);
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//cerr << "Signal below receiver minimum sensitivity: " << signal << endl;
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return;
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}
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else {
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SG_LOG(SG_GENERAL, SG_BULK, "Signal completely readable: " << signal);
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//cerr << "Signal completely readable: " << signal << endl;
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fgSetString("/sim/messages/atc", text.c_str());
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/** write signal strength above threshold to the property tree
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* to implement a simple S-meter just divide by 3 dB per grade (VHF norm)
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@ -157,8 +150,6 @@ void FGRadioTransmission::receiveATC(SGGeod tx_pos, double freq, string text, in
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// Use ITM propagation model
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double signal = ITM_calculate_attenuation(tx_pos, freq, ground_to_air);
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if (signal <= 0.0) {
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SG_LOG(SG_GENERAL, SG_BULK, "Signal below receiver minimum sensitivity: " << signal);
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//cerr << "Signal below receiver minimum sensitivity: " << signal << endl;
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return;
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}
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if ((signal > 0.0) && (signal < 12.0)) {
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@ -188,8 +179,6 @@ void FGRadioTransmission::receiveATC(SGGeod tx_pos, double freq, string text, in
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fgSetDouble("/sim/sound/voices/voice/volume", old_volume);
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}
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else {
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SG_LOG(SG_GENERAL, SG_BULK, "Signal completely readable: " << signal);
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//cerr << "Signal completely readable: " << signal << endl;
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fgSetString("/sim/messages/atc", text.c_str());
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/** write signal strength above threshold to the property tree
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* to implement a simple S-meter just divide by 3 dB per grade (VHF norm)
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@ -233,16 +222,11 @@ double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, i
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double clutter_loss = 0.0; // loss due to vegetation and urban
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double tx_pow = _transmitter_power;
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double ant_gain = _antenna_gain;
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double ant_gain = _rx_antenna_gain + _tx_antenna_gain;
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double signal = 0.0;
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if(transmission_type == 1)
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tx_pow = _transmitter_power + 6.0;
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if((transmission_type == 1) || (transmission_type == 3))
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ant_gain = _antenna_gain + 3.0; //pilot plane's antenna gain + ground station antenna gain
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double link_budget = tx_pow - _receiver_sensitivity + ant_gain;
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double link_budget = tx_pow - _receiver_sensitivity - _rx_line_losses - _tx_line_losses + ant_gain;
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FGScenery * scenery = globals->get_scenery();
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@ -259,11 +243,7 @@ double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, i
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SGGeoc center = SGGeoc::fromGeod( max_own_pos );
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SGGeoc own_pos_c = SGGeoc::fromGeod( own_pos );
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/** position of sender radio antenna (HAAT)
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sender can be aircraft or ground station
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**/
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double ATC_HAAT = 30.0;
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double Aircraft_HAAT = 5.0;
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double sender_alt_ft,sender_alt;
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double transmitter_height=0.0;
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double receiver_height=0.0;
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@ -302,7 +282,7 @@ double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, i
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double elevation_under_pilot = 0.0;
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if (scenery->get_elevation_m( max_own_pos, elevation_under_pilot, NULL )) {
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receiver_height = own_alt - elevation_under_pilot + 3; //assume antenna located 3 meters above ground
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receiver_height = own_alt - elevation_under_pilot;
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}
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double elevation_under_sender = 0.0;
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@ -313,10 +293,10 @@ double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, i
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transmitter_height = sender_alt;
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}
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if(transmission_type == 1)
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transmitter_height += ATC_HAAT;
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else
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transmitter_height += Aircraft_HAAT;
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transmitter_height += _tx_antenna_height;
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receiver_height += _rx_antenna_height;
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SG_LOG(SG_GENERAL, SG_BULK,
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"ITM:: RX-height: " << receiver_height << " meters, TX-height: " << transmitter_height << " meters, Distance: " << distance_m << " meters");
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@ -383,7 +363,7 @@ double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, i
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}
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double num_points= (double)_elevations.size();
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//cerr << "ITM:: Max alt between: " << max_alt_between << ", num points:" << num_points << endl;
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_elevations.push_front(point_distance);
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_elevations.push_front(num_points -1);
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int size = _elevations.size();
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@ -442,7 +422,6 @@ void FGRadioTransmission::clutterLoss(double freq, double distance_m, double itm
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double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
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// First Fresnel radius
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double frs_rad = 548 * sqrt( (j * itm_elev[1] * (itm_elev[0] - j) * itm_elev[1] / 1000000) / ( distance_m * freq / 1000) );
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assert(frs_rad > 0);
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//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
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@ -494,7 +473,6 @@ void FGRadioTransmission::clutterLoss(double freq, double distance_m, double itm
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double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[num_points_1st + 2] + clutter_height) / distance_m;
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// First Fresnel radius
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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) );
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assert(frs_rad > 0);
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//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
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@ -539,7 +517,6 @@ void FGRadioTransmission::clutterLoss(double freq, double distance_m, double itm
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double grad = fabs(itm_elev[last+1] + clutter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
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// First Fresnel radius
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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) );
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assert(frs_rad > 0);
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//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
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@ -592,7 +569,6 @@ void FGRadioTransmission::clutterLoss(double freq, double distance_m, double itm
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double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[num_points_1st + 2] + clutter_height) / distance_m;
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// First Fresnel radius
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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) );
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assert(frs_rad > 0);
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//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
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@ -637,7 +613,6 @@ void FGRadioTransmission::clutterLoss(double freq, double distance_m, double itm
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// First Fresnel radius
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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) );
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assert(frs_rad > 0);
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//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
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double min_elev = SGMiscd::min(itm_elev[last+1] + clutter_height, itm_elev[num_points_1st + num_points_2nd +2] + clutter_height);
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@ -682,7 +657,6 @@ void FGRadioTransmission::clutterLoss(double freq, double distance_m, double itm
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// First Fresnel radius
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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) );
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assert(frs_rad > 0);
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//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
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@ -847,10 +821,9 @@ double FGRadioTransmission::LOS_calculate_attenuation(SGGeod pos, double freq, i
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frq_mhz = freq;
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double dbloss;
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double tx_pow = _transmitter_power;
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double ant_gain = _antenna_gain;
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double ant_gain = _rx_antenna_gain + _tx_antenna_gain;
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double signal = 0.0;
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double ATC_HAAT = 30.0;
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double Aircraft_HAAT = 5.0;
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double sender_alt_ft,sender_alt;
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double transmitter_height=0.0;
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double receiver_height=0.0;
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@ -859,13 +832,8 @@ double FGRadioTransmission::LOS_calculate_attenuation(SGGeod pos, double freq, i
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double own_alt_ft = fgGetDouble("/position/altitude-ft");
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double own_alt= own_alt_ft * SG_FEET_TO_METER;
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if(transmission_type == 1)
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tx_pow = _transmitter_power + 6.0;
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if((transmission_type == 1) || (transmission_type == 3))
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ant_gain = _antenna_gain + 3.0; //pilot plane's antenna gain + ground station antenna gain
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double link_budget = tx_pow - _receiver_sensitivity + ant_gain;
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double link_budget = tx_pow - _receiver_sensitivity - _rx_line_losses - _tx_line_losses + ant_gain;
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//cerr << "ITM:: pilot Lat: " << own_lat << ", Lon: " << own_lon << ", Alt: " << own_alt << endl;
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@ -881,10 +849,10 @@ double FGRadioTransmission::LOS_calculate_attenuation(SGGeod pos, double freq, i
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double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
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if(transmission_type == 1)
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transmitter_height += ATC_HAAT;
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else
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transmitter_height += Aircraft_HAAT;
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transmitter_height += _tx_antenna_height;
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receiver_height += _rx_antenna_height;
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/** radio horizon calculation with wave bending k=4/3 */
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double receiver_horizon = 4.12 * sqrt(receiver_height);
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@ -44,7 +44,6 @@ private:
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double _transmitter_power;
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double _tx_antenna_height;
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double _rx_antenna_height;
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double _antenna_gain;
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double _rx_antenna_gain;
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double _tx_antenna_gain;
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double _rx_line_losses;
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@ -72,6 +71,10 @@ public:
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void setRxSensitivity(double sensitivity) { _receiver_sensitivity = sensitivity; };
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void setTxAntennaHeight(double tx_antenna_height) { _tx_antenna_height = tx_antenna_height; };
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void setRxAntennaHeight(double rx_antenna_height) { _rx_antenna_height = rx_antenna_height; };
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void setTxAntennaGain(double tx_antenna_gain) { _tx_antenna_gain = tx_antenna_gain; };
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void setRxAntennaGain(double rx_antenna_gain) { _rx_antenna_gain = rx_antenna_gain; };
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void setTxLineLosses(double tx_line_losses) { _tx_line_losses = tx_line_losses; };
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void setRxLineLosses(double rx_line_losses) { _rx_line_losses = rx_line_losses; };
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void setPropagationModel(int model) { _propagation_model = model; };
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// transmission_type: 0 for air to ground 1 for ground to air, 2 for air to air, 3 for pilot to ground, 4 for pilot to air
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void receiveATC(SGGeod tx_pos, double freq, string text, int transmission_type);
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