refactor receiveATC(), implement simple LOS routine, set comm1-signal property

diff --git a/src/ATC/trafficcontrol.cxx b/src/ATC/trafficcontrol.cxx
index 2b0d20c6793bbe2924c29e13b9d0d084941f8538..cf0b16f313ae33231720fc7a00e5c795aa23a40c 100644 (file)
--- a/src/ATC/trafficcontrol.cxx
+++ b/src/ATC/trafficcontrol.cxx
@@ -762,7 +762,7 @@ void FGATCController::transmit(FGTrafficRecord * rec, FGAirportDynamics *parent,
                                             rec->getLatitude(), sender_alt );
                                }
                                double frequency = ((double)stationFreq) / 100;
-                       radio->receiveText(sender_pos, frequency, text, ground_to_air);
+                       radio->receiveATC(sender_pos, frequency, text, ground_to_air);
                        delete radio;
                }
                else {

diff --git a/src/Radio/radio.cxx b/src/Radio/radio.cxx
index 9b3d0320f6eb5d3a84803f95116f77acc488d4bd..260894655729249c6bef29b24e455f686107afdc 100644 (file)
--- a/src/Radio/radio.cxx
+++ b/src/Radio/radio.cxx
@@ -34,14 +34,15 @@
 
 FGRadio::FGRadio() {
        
-       /** radio parameters (which should probably be set for each radio via constructor) */
+       /** radio parameters (which should probably be set for each radio) */
+       
        _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
+       *       later possibly store this value in aircraft description
+       *       ATC comms usually operate high power equipment, thus making the link asymetrical; this is taken care of in propagation routines
        **/
        _transmitter_power = 43.0;
        
@@ -74,10 +75,16 @@ double FGRadio::getFrequency(int radio) {
        return freq;
 }
 
+/*** TODO: receive multiplayer chat message and voice
+***/
+void FGRadio::receiveChat(SGGeod tx_pos, double freq, string text,
+       int ground_to_air) {
 
+}
 
-
-void FGRadio::receiveText(SGGeod tx_pos, double freq, string text,
+/*** Receive ATC radio communication as text
+***/
+void FGRadio::receiveATC(SGGeod tx_pos, double freq, string text,
        int ground_to_air) {
 
        /*
@@ -93,7 +100,19 @@ void FGRadio::receiveText(SGGeod tx_pos, double freq, string text,
                        fgSetString("/sim/messages/atc", text.c_str());
                }
                else if ( _propagation_model == 1 ) {
-                       // free space, round earth
+                       // TODO: free space, round earth
+                       double signal = LOS_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;
+                       }
+                       else {
+                               SG_LOG(SG_GENERAL, SG_BULK, "Signal completely readable: " << signal);
+                               //cerr << "Signal completely readable: " << signal << endl;
+                               fgSetString("/sim/messages/atc", text.c_str());
+                               fgSetDouble("/sim/radio/comm1-signal", signal);
+                       }
                }
                else if ( _propagation_model == 2 ) {
                        // Use ITM propagation model
@@ -126,12 +145,14 @@ void FGRadio::receiveText(SGGeod tx_pos, double freq, string text,
                                //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 {
                                SG_LOG(SG_GENERAL, SG_BULK, "Signal completely readable: " << signal);
                                //cerr << "Signal completely readable: " << signal << endl;
                                fgSetString("/sim/messages/atc", text.c_str());
+                               fgSetDouble("/sim/radio/comm1-signal", signal);
                        }
                        
                }
@@ -221,8 +242,8 @@ double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq,
        if (own_alt > 8000) {
                dbloss = 20 * log10(distance_m) +20 * log10(frq_mhz) -27.55;
                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;
+                       "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;
        }
@@ -338,3 +359,72 @@ double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq,
        return signal;
 
 }
+
+/*** implement simple LOS propagation model (WIP)
+***/
+double FGRadio::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 = _antenna_gain;
+       double signal = 0.0;
+       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;
+       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;
+       
+       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; 
+
+       //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);
+       
+       if(transmission_type == 1) 
+               transmitter_height += ATC_HAAT;
+       else
+               transmitter_height += Aircraft_HAAT;
+       
+       /** 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;
+       
+}

diff --git a/src/Radio/radio.hxx b/src/Radio/radio.hxx
index 4b2b67c85560d50ea95f5416f52e7c63a4eb78d1..378cfa37b71d600c25706a4d6e9ffcdf1c777cfa 100644 (file)
--- a/src/Radio/radio.hxx
+++ b/src/Radio/radio.hxx
@@ -46,6 +46,7 @@ private:
        
        int _propagation_model; /// 0 none, 1 round Earth, 2 ITM
        double ITM_calculate_attenuation(SGGeod tx_pos, double freq, int ground_to_air);
+       double LOS_calculate_attenuation(SGGeod tx_pos, double freq, int ground_to_air);
        
 public:
 
@@ -56,8 +57,9 @@ public:
     void setFrequency(double freq, int radio);
     double getFrequency(int radio);
     void setTxPower(double txpower) { _transmitter_power = txpower; };
-    // transmission_type: 1 for ground to air, 2 for air to air, 3 for pilot to ground, 4 for pilot to air
-    void receiveText(SGGeod tx_pos, double freq, string text, int transmission_type);
+    // 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
+    void receiveATC(SGGeod tx_pos, double freq, string text, int transmission_type);
+    void receiveChat(SGGeod tx_pos, double freq, string text, int transmission_type);
     void setPropagationModel(int model) { _propagation_model = model; };
     
 };