1026 lines
35 KiB
C++
1026 lines
35 KiB
C++
// radio.cxx -- implementation of FGRadio
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// Class to manage radio propagation using the ITM model
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// Written by Adrian Musceac YO8RZZ, started August 2011.
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <cmath>
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#include <stdlib.h>
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#include <deque>
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#include "radio.hxx"
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#include <simgear/scene/material/mat.hxx>
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#include <Scenery/scenery.hxx>
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#include <boost/scoped_array.hpp>
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#define WITH_POINT_TO_POINT 1
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#include "itm.cpp"
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FGRadioTransmission::FGRadioTransmission() {
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_receiver_sensitivity = -105.0; // typical AM receiver sensitivity seems to be 0.8 microVolt at 12dB SINAD or less
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/** AM transmitter power in dBm.
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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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* 47 dBm - 50 W (center, sectors)
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* 50 dBm - 100 W (center, sectors)
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* 53 dBm - 200 W (sectors, on directional arrays)
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**/
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_transmitter_power = 43.0;
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_tx_antenna_height = 2.0; // TX antenna height above ground level
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_rx_antenna_height = 2.0; // RX antenna height above ground level
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_rx_antenna_gain = 1.0; // maximum antenna 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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_polarization = 1; // default vertical
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_propagation_model = 2;
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_root_node = fgGetNode("sim/radio", true);
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_terrain_sampling_distance = _root_node->getDoubleValue("sampling-distance", 90.0); // regular SRTM is 90 meters
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}
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FGRadioTransmission::~FGRadioTransmission()
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{
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}
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double FGRadioTransmission::getFrequency(int radio) {
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double freq = 118.0;
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switch (radio) {
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case 1:
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freq = fgGetDouble("/instrumentation/comm[0]/frequencies/selected-mhz");
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break;
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case 2:
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freq = fgGetDouble("/instrumentation/comm[1]/frequencies/selected-mhz");
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break;
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default:
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freq = fgGetDouble("/instrumentation/comm[0]/frequencies/selected-mhz");
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}
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return freq;
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}
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void FGRadioTransmission::receiveChat(SGGeod tx_pos, double freq, string text, int ground_to_air) {
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}
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double FGRadioTransmission::receiveNav(SGGeod tx_pos, double freq, int transmission_type) {
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// typical VOR/LOC transmitter power appears to be 100 - 200 Watt i.e 50 - 53 dBm
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// vor/loc typical sensitivity between -107 and -101 dBm
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// glideslope sensitivity between -85 and -81 dBm
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if ( _propagation_model == 1) {
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return LOS_calculate_attenuation(tx_pos, freq, 1);
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}
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else if ( _propagation_model == 2) {
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return ITM_calculate_attenuation(tx_pos, freq, 1);
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}
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return -1;
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}
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double FGRadioTransmission::receiveBeacon(SGGeod &tx_pos, double heading, double pitch) {
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// these properties should be set by an instrument
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_receiver_sensitivity = _root_node->getDoubleValue("station[0]/rx-sensitivity", _receiver_sensitivity);
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_transmitter_power = watt_to_dbm(_root_node->getDoubleValue("station[0]/tx-power-watt", _transmitter_power));
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_polarization = _root_node->getIntValue("station[0]/polarization", 1);
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_tx_antenna_height += _root_node->getDoubleValue("station[0]/tx-antenna-height", 0);
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_rx_antenna_height += _root_node->getDoubleValue("station[0]/rx-antenna-height", 0);
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_tx_antenna_gain += _root_node->getDoubleValue("station[0]/tx-antenna-gain", 0);
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_rx_antenna_gain += _root_node->getDoubleValue("station[0]/rx-antenna-gain", 0);
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double freq = _root_node->getDoubleValue("station[0]/frequency", 144.8); // by default stay in the ham 2 meter band
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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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return -1;
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}
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double signal = ITM_calculate_attenuation(tx_pos, freq, 1);
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return signal;
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}
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void FGRadioTransmission::receiveATC(SGGeod tx_pos, double freq, string text, int ground_to_air) {
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// adjust some default parameters in case the ATC code does not set them
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if(ground_to_air == 1) {
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_transmitter_power += 4.0;
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_tx_antenna_height += 30.0;
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_tx_antenna_gain += 2.0;
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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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return;
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}
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else {
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if ( _propagation_model == 0) { // skip propagation routines entirely
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fgSetString("/sim/messages/atc", text.c_str());
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}
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else if ( _propagation_model == 1 ) { // Use 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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return;
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}
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else {
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fgSetString("/sim/messages/atc", text.c_str());
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}
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}
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else if ( _propagation_model == 2 ) { // 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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return;
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}
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if ((signal > 0.0) && (signal < 12.0)) {
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/** for low SNR values need a way to make the conversation
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* hard to understand but audible
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* in the real world, the receiver AGC fails to capture the slope
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* and the signal, due to being amplitude modulated, decreases volume after demodulation
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* the workaround below is more akin to what would happen on a FM transmission
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* therefore the correct way would be to work on the volume
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**/
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/*
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string hash_noise = " ";
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int reps = (int) (fabs(floor(signal - 11.0)) * 2);
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int t_size = text.size();
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for (int n = 1; n <= reps; ++n) {
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int pos = rand() % (t_size -1);
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text.replace(pos,1, hash_noise);
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}
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*/
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//double volume = (fabs(signal - 12.0) / 12);
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//double old_volume = fgGetDouble("/sim/sound/voices/voice/volume");
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//fgSetDouble("/sim/sound/voices/voice/volume", volume);
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fgSetString("/sim/messages/atc", text.c_str());
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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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fgSetString("/sim/messages/atc", text.c_str());
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}
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}
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}
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}
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double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, int transmission_type) {
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if((freq < 40.0) || (freq > 20000.0)) // frequency out of recommended range
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return -1;
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/** ITM default parameters
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TODO: take them from tile materials (especially for sea)?
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**/
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double eps_dielect=15.0;
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double sgm_conductivity = 0.005;
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double eno = 301.0;
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double frq_mhz = freq;
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int radio_climate = 5; // continental temperate
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int pol= _polarization;
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double conf = 0.90; // 90% of situations and time, take into account speed
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double rel = 0.90;
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double dbloss;
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char strmode[150];
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int p_mode = 0; // propgation mode selector: 0 LOS, 1 diffraction dominant, 2 troposcatter
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double horizons[2];
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int errnum;
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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 = _rx_antenna_gain + _tx_antenna_gain;
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double signal = 0.0;
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double link_budget = tx_pow - _receiver_sensitivity - _rx_line_losses - _tx_line_losses + ant_gain;
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double signal_strength = tx_pow - _rx_line_losses - _tx_line_losses + ant_gain;
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double tx_erp = dbm_to_watt(tx_pow + _tx_antenna_gain - _tx_line_losses);
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FGScenery * scenery = globals->get_scenery();
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double own_lat = fgGetDouble("/position/latitude-deg");
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double own_lon = fgGetDouble("/position/longitude-deg");
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double own_alt_ft = fgGetDouble("/position/altitude-ft");
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double own_heading = fgGetDouble("/orientation/heading-deg");
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double own_alt= own_alt_ft * SG_FEET_TO_METER;
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SGGeod own_pos = SGGeod::fromDegM( own_lon, own_lat, own_alt );
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SGGeod max_own_pos = SGGeod::fromDegM( own_lon, own_lat, SG_MAX_ELEVATION_M );
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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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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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SGGeod sender_pos = pos;
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sender_alt_ft = sender_pos.getElevationFt();
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sender_alt = sender_alt_ft * SG_FEET_TO_METER;
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SGGeod max_sender_pos = SGGeod::fromGeodM( pos, SG_MAX_ELEVATION_M );
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SGGeoc sender_pos_c = SGGeoc::fromGeod( sender_pos );
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double point_distance= _terrain_sampling_distance;
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double course = SGGeodesy::courseRad(own_pos_c, sender_pos_c);
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double reverse_course = SGGeodesy::courseRad(sender_pos_c, own_pos_c);
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double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
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double probe_distance = 0.0;
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/** If distance larger than this value (300 km), assume reception imposssible to spare CPU cycles */
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if (distance_m > 300000)
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return -1.0;
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/** If above 8000 meters, consider LOS mode and calculate free-space att to spare CPU cycles */
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if (own_alt > 8000) {
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dbloss = 20 * log10(distance_m) +20 * log10(frq_mhz) -27.55;
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SG_LOG(SG_GENERAL, SG_BULK,
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"ITM Free-space mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation");
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//cerr << "ITM Free-space mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation" << endl;
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signal = link_budget - dbloss;
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return signal;
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}
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int max_points = (int)floor(distance_m / point_distance);
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//double delta_last = fmod(distance_m, point_distance);
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deque<double> elevations;
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deque<string*> materials;
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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;
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}
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double elevation_under_sender = 0.0;
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if (scenery->get_elevation_m( max_sender_pos, elevation_under_sender, NULL )) {
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transmitter_height = sender_alt - elevation_under_sender;
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}
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else {
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transmitter_height = sender_alt;
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}
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transmitter_height += _tx_antenna_height;
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receiver_height += _rx_antenna_height;
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//cerr << "ITM:: RX-height: " << receiver_height << " meters, TX-height: " << transmitter_height << " meters, Distance: " << distance_m << " meters" << endl;
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_root_node->setDoubleValue("station[0]/rx-height", receiver_height);
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_root_node->setDoubleValue("station[0]/tx-height", transmitter_height);
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_root_node->setDoubleValue("station[0]/distance", distance_m / 1000);
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unsigned int e_size = (deque<unsigned>::size_type)max_points;
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while (elevations.size() <= e_size) {
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probe_distance += point_distance;
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SGGeod probe = SGGeod::fromGeoc(center.advanceRadM( course, probe_distance ));
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const simgear::BVHMaterial *material = 0;
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double elevation_m = 0.0;
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if (scenery->get_elevation_m( probe, elevation_m, &material )) {
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const SGMaterial *mat;
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mat = dynamic_cast<const SGMaterial*>(material);
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if((transmission_type == 3) || (transmission_type == 4)) {
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elevations.push_back(elevation_m);
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if(mat) {
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const std::vector<string> mat_names = mat->get_names();
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string* name = new string(mat_names[0]);
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materials.push_back(name);
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}
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else {
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string* no_material = new string("None");
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materials.push_back(no_material);
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}
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}
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else {
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elevations.push_front(elevation_m);
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if(mat) {
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const std::vector<string> mat_names = mat->get_names();
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string* name = new string(mat_names[0]);
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materials.push_front(name);
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}
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else {
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string* no_material = new string("None");
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materials.push_front(no_material);
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}
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}
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}
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else {
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if((transmission_type == 3) || (transmission_type == 4)) {
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elevations.push_back(0.0);
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string* no_material = new string("None");
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materials.push_back(no_material);
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}
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else {
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string* no_material = new string("None");
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elevations.push_front(0.0);
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materials.push_front(no_material);
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}
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}
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}
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if((transmission_type == 3) || (transmission_type == 4)) {
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elevations.push_front(elevation_under_pilot);
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//if (delta_last > (point_distance / 2) ) // only add last point if it's farther than half point_distance
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elevations.push_back(elevation_under_sender);
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}
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else {
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elevations.push_back(elevation_under_pilot);
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//if (delta_last > (point_distance / 2) )
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elevations.push_front(elevation_under_sender);
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}
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double num_points= (double)elevations.size();
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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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boost::scoped_array<double> itm_elev( new double[size] );
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for(int i=0;i<size;i++) {
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itm_elev[i]=elevations[i];
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}
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if((transmission_type == 3) || (transmission_type == 4)) {
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// the sender and receiver roles are switched
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ITM::point_to_point(itm_elev.get(), receiver_height, transmitter_height,
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eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
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pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
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if( _root_node->getBoolValue( "use-clutter-attenuation", false ) )
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calculate_clutter_loss(frq_mhz, itm_elev.get(), materials, receiver_height, transmitter_height, p_mode, horizons, clutter_loss);
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}
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else {
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ITM::point_to_point(itm_elev.get(), transmitter_height, receiver_height,
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eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
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pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
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if( _root_node->getBoolValue( "use-clutter-attenuation", false ) )
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calculate_clutter_loss(frq_mhz, itm_elev.get(), materials, transmitter_height, receiver_height, p_mode, horizons, clutter_loss);
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}
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double pol_loss = 0.0;
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// TODO: remove this check after we check a bit the axis calculations in this function
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if (_polarization == 1) {
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pol_loss = polarization_loss();
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}
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//SG_LOG(SG_GENERAL, SG_BULK,
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// "ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum);
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//cerr << "ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum << endl;
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_root_node->setDoubleValue("station[0]/link-budget", link_budget);
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_root_node->setDoubleValue("station[0]/terrain-attenuation", dbloss);
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_root_node->setStringValue("station[0]/prop-mode", strmode);
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_root_node->setDoubleValue("station[0]/clutter-attenuation", clutter_loss);
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_root_node->setDoubleValue("station[0]/polarization-attenuation", pol_loss);
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//if (errnum == 4) // if parameters are outside sane values for lrprop, bail out fast
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// return -1;
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// temporary, keep this antenna radiation pattern code here
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double tx_pattern_gain = 0.0;
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double rx_pattern_gain = 0.0;
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double sender_heading = 270.0; // due West
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double tx_antenna_bearing = sender_heading - reverse_course * SGD_RADIANS_TO_DEGREES;
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double rx_antenna_bearing = own_heading - course * SGD_RADIANS_TO_DEGREES;
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double rx_elev_angle = atan((itm_elev[2] + transmitter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m) * SGD_RADIANS_TO_DEGREES;
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double tx_elev_angle = 0.0 - rx_elev_angle;
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if (_root_node->getBoolValue("use-tx-antenna-pattern", false)) {
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FGRadioAntenna* TX_antenna;
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TX_antenna = new FGRadioAntenna("Plot2");
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TX_antenna->set_heading(sender_heading);
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TX_antenna->set_elevation_angle(0);
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tx_pattern_gain = TX_antenna->calculate_gain(tx_antenna_bearing, tx_elev_angle);
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delete TX_antenna;
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}
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if (_root_node->getBoolValue("use-rx-antenna-pattern", false)) {
|
|
FGRadioAntenna* RX_antenna;
|
|
RX_antenna = new FGRadioAntenna("Plot2");
|
|
RX_antenna->set_heading(own_heading);
|
|
RX_antenna->set_elevation_angle(fgGetDouble("/orientation/pitch-deg"));
|
|
rx_pattern_gain = RX_antenna->calculate_gain(rx_antenna_bearing, rx_elev_angle);
|
|
delete RX_antenna;
|
|
}
|
|
|
|
signal = link_budget - dbloss - clutter_loss + pol_loss + rx_pattern_gain + tx_pattern_gain;
|
|
double signal_strength_dbm = signal_strength - dbloss - clutter_loss + pol_loss + rx_pattern_gain + tx_pattern_gain;
|
|
double field_strength_uV = dbm_to_microvolt(signal_strength_dbm);
|
|
_root_node->setDoubleValue("station[0]/signal-dbm", signal_strength_dbm);
|
|
_root_node->setDoubleValue("station[0]/field-strength-uV", field_strength_uV);
|
|
_root_node->setDoubleValue("station[0]/signal", signal);
|
|
_root_node->setDoubleValue("station[0]/tx-erp", tx_erp);
|
|
|
|
//_root_node->setDoubleValue("station[0]/tx-pattern-gain", tx_pattern_gain);
|
|
//_root_node->setDoubleValue("station[0]/rx-pattern-gain", rx_pattern_gain);
|
|
|
|
for (unsigned i =0; i < materials.size(); i++) {
|
|
delete materials[i];
|
|
}
|
|
|
|
return signal;
|
|
|
|
}
|
|
|
|
|
|
void FGRadioTransmission::calculate_clutter_loss(double freq, double itm_elev[], deque<string*> &materials,
|
|
double transmitter_height, double receiver_height, int p_mode,
|
|
double horizons[], double &clutter_loss) {
|
|
|
|
double distance_m = itm_elev[0] * itm_elev[1]; // only consider elevation points
|
|
unsigned mat_size = materials.size();
|
|
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
|
|
if((unsigned)mat >= mat_size) { //this tends to happen when the model interferes with the antenna (obstructs)
|
|
//cerr << "Array index out of bounds 0-0: " << mat << " size: " << mat_size << endl;
|
|
break;
|
|
}
|
|
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) );
|
|
if (frs_rad <= 0.0) { //this tends to happen when the model interferes with the antenna (obstructs)
|
|
//cerr << "Frs rad 0-0: " << frs_rad << endl;
|
|
continue;
|
|
}
|
|
//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
|
|
|
|
if((unsigned)mat >= mat_size) {
|
|
//cerr << "Array index out of bounds 1-1: " << mat << " size: " << mat_size << endl;
|
|
break;
|
|
}
|
|
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) );
|
|
if (frs_rad <= 0.0) {
|
|
//cerr << "Frs rad 1-1: " << frs_rad << endl;
|
|
continue;
|
|
}
|
|
//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
|
|
|
|
if((unsigned)mat >= mat_size) {
|
|
//cerr << "Array index out of bounds 1-2: " << mat << " size: " << mat_size << endl;
|
|
break;
|
|
}
|
|
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) );
|
|
if (frs_rad <= 0.0) {
|
|
//cerr << "Frs rad 1-2: " << frs_rad << " numpoints2 " << num_points_2nd << " j: " << j << endl;
|
|
continue;
|
|
}
|
|
//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
|
|
if((unsigned)mat >= mat_size) {
|
|
//cerr << "Array index out of bounds 2-1: " << mat << " size: " << mat_size << endl;
|
|
break;
|
|
}
|
|
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) );
|
|
if (frs_rad <= 0.0) {
|
|
//cerr << "Frs rad 2-1: " << frs_rad << " numpoints1 " << num_points_1st << " j: " << j << endl;
|
|
continue;
|
|
}
|
|
//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;
|
|
}
|
|
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
|
|
if((unsigned)mat >= mat_size) {
|
|
//cerr << "Array index out of bounds 2-2: " << mat << " size: " << mat_size << endl;
|
|
break;
|
|
}
|
|
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) );
|
|
if (frs_rad <= 0.0) {
|
|
//cerr << "Frs rad 2-2: " << frs_rad << " numpoints2 " << num_points_2nd << " j: " << j << endl;
|
|
continue;
|
|
}
|
|
//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
|
|
if((unsigned)mat >= mat_size) {
|
|
//cerr << "Array index out of bounds 2-3: " << mat << " size: " << mat_size << endl;
|
|
break;
|
|
}
|
|
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) );
|
|
if (frs_rad <= 0.0) {
|
|
//cerr << "Frs rad 2-3: " << frs_rad << " numpoints3 " << num_points_3rd << " j: " << j << endl;
|
|
continue;
|
|
}
|
|
|
|
//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... maybe do something with weather
|
|
clutter_loss = 0.0;
|
|
}
|
|
|
|
}
|
|
|
|
|
|
void FGRadioTransmission::get_material_properties(string* mat_name, double &height, double &density) {
|
|
|
|
if(!mat_name)
|
|
return;
|
|
|
|
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;
|
|
}
|
|
|
|
}
|
|
|
|
|
|
double FGRadioTransmission::LOS_calculate_attenuation(SGGeod pos, double freq, int transmission_type) {
|
|
|
|
double 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;
|
|
}
|
|
double pol_loss = 0.0;
|
|
if (_polarization == 1) {
|
|
pol_loss = polarization_loss();
|
|
}
|
|
// free-space loss (distance calculation should be changed)
|
|
dbloss = 20 * log10(distance_m) +20 * log10(frq_mhz) -27.55;
|
|
signal = link_budget - dbloss + pol_loss;
|
|
|
|
//cerr << "LOS:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm " << endl;
|
|
return signal;
|
|
|
|
}
|
|
|
|
/*** calculate loss due to polarization mismatch
|
|
* this function is only reliable for vertical polarization
|
|
* due to the V-shape of horizontally polarized antennas
|
|
***/
|
|
double FGRadioTransmission::polarization_loss() {
|
|
|
|
double theta_deg;
|
|
double roll = fgGetDouble("/orientation/roll-deg");
|
|
if (fabs(roll) > 85.0)
|
|
roll = 85.0;
|
|
double pitch = fgGetDouble("/orientation/pitch-deg");
|
|
if (fabs(pitch) > 85.0)
|
|
pitch = 85.0;
|
|
double theta = fabs( atan( sqrt(
|
|
pow(tan(roll * SGD_DEGREES_TO_RADIANS), 2) +
|
|
pow(tan(pitch * SGD_DEGREES_TO_RADIANS), 2) )) * SGD_RADIANS_TO_DEGREES);
|
|
|
|
if (_polarization == 0)
|
|
theta_deg = 90.0 - theta;
|
|
else
|
|
theta_deg = theta;
|
|
if (theta_deg > 85.0) // we don't want to converge into infinity
|
|
theta_deg = 85.0;
|
|
|
|
double loss = 10 * log10( pow(cos(theta_deg * SGD_DEGREES_TO_RADIANS), 2) );
|
|
//cerr << "Polarization loss: " << loss << " dBm " << endl;
|
|
return loss;
|
|
}
|
|
|
|
|
|
double FGRadioTransmission::watt_to_dbm(double power_watt) {
|
|
return 10 * log10(1000 * power_watt); // returns dbm
|
|
}
|
|
|
|
double FGRadioTransmission::dbm_to_watt(double dbm) {
|
|
return exp( (dbm-30) * log(10.0) / 10.0); // returns Watts
|
|
}
|
|
|
|
double FGRadioTransmission::dbm_to_microvolt(double dbm) {
|
|
return sqrt(dbm_to_watt(dbm) * 50) * 1000000; // returns microvolts
|
|
}
|
|
|
|
|