Communications¶
Communication devices lay the groundwork to enable many AFSIM features, including remote task assignment, chains of command, and many other simulation and modeling options.
They are platform parts which facilitate remote communications between and among platforms. These devices transmit and receive messages between platforms and can be wired or wireless. Communication devices must use the same network to communicate with each other.
AFSIM provides a number of predefined communication devices, the most common of which include:
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Quick Start¶
To get started with communications devices, the following comm command block can be added to an existing platform or platform type:
comm perfect_transceiver WSF_COMM_TRANSCEIVER end_comm
Any platforms which have a perfect_transceiver will be able to communicate with each other by default, allowing platforms to pass messages to others on the network. Higher fidelity communication networks may be modeled by introducing transmitter and receiver specifications, antenna commands, articulated part commands, bandwidth limitations, error rates, and signal-to-noise ratios.
Internal links may be added to processors to enable the communication of tracks from one platform to others.
Closer Look¶
Note
The following steps assume that the “simple_flight” scenario is present as discussed in Behaviors and Behavior Trees.
Adding Communications¶
To implement communications between the two aircraft in simple_flight, complete the following steps:
Create a new file called communications.txt.
Add the following code line to cargo_aircraft.txt:
include_once communications.txt
Open communications.txt in a Wizard text editor.
Add the following code to communications.txt:
# communications.txt # A component of the simple_flight demo comm AIR_RADIO_TRANSCEIVER WSF_RADIO_TRANSCEIVER transmitter frequency 120 mhz end_transmitter receiver frequency 120 mhz end_receiver end_comm
Add the following code to the platform type definition of CARGO_AIRCRAFT:
add comm atc AIR_RADIO_TRANSCEIVER end_comm
At this point, the two aircraft have an open communication channel on which to pass messages. However, they currently have no messages to send to one another.
Add Behaviors and Processors to Send a Message over Comms¶
Currently, the automated behavior in behaviors.txt will cause each aircraft to move out of the others way. This isn’t necessary, as it would be sufficient to have just one of the aircraft change altitude to avoid a collision.
Update behavior.txt to reflect the following:
# behaviors.txt # A component of the simple_flight demo behavior next_selector precondition return true; end_precondition end_behavior
behavior all_clear precondition WsfLocalTrackList trackList = PLATFORM.TrackList("track_proc"); return (trackList.Empty() && !PLATFORM.AuxDataBool("collisionExpected")); end_precondition execute WsfPlatform plat = PLATFORM; writeln(plat.Name(), " Report: All Clear"); end_execute end_behaviorbehavior entity_detected precondition WsfLocalTrackList trackList = PLATFORM.TrackList("track_proc"); return !trackList.Empty(); end_precondition execute WsfPlatform plat = PLATFORM; WsfTrack firstTrack = plat.TrackList("track_proc")[0]; writeln(plat.Name(), " Report: Entity Detected"); if (!plat.AuxDataBool("collisionWarningRcvd")) { plat.SetAuxData("collisionExpected", false); } if (plat.AuxDataBool("collisionWarningCooldown")) { plat.SetAuxData("collisionWarningCooldown", false); } else { WsfLocalTrackList trackList = plat.TrackList("track_proc"); int index = 0; foreach (WsfTrack t in trackList) { if (t.Target().IsValid()) { writeln("\t - Entity: ", t.Target().Name()); double lastDist = plat.AuxDataDouble("lastKnownDistance"); double currDist = plat.GroundRangeTo(t.CurrentLocation()); if (Math.Ceil(plat.Altitude()/100) == Math.Ceil(t.Altitude()/100) && (lastDist == -1 || lastDist > currDist)) { plat.SetAuxData("lastKnownDistance", currDist); writeln("\t - WARNING: Collision Expected!\n"); plat.SetAuxData("collisionExpected", true); plat.SetAuxData("collisionTrackIdx", index); } else { plat.SetAuxData("collisionExpected", false); } } index = index + 1; } } end_execute end_behaviorbehavior reroute precondition bool collisionExpected = PLATFORM.AuxDataBool("collisionExpected"); bool collisionWarningRcvd = PLATFORM.AuxDataBool("collisionWarningRcvd"); return (collisionExpected || collisionWarningRcvd); end_precondition execute WsfPlatform plat = PLATFORM; double altDelta = 100 * Math.Ceil(RANDOM.Uniform(0, 30) - 20); plat.GoToAltitude(plat.Altitude() + altDelta); writeln(plat.Name(), " Report: Rerouting"); writeln("\t - New Target Altitude = ", plat.Altitude() + altDelta, "m\n"); plat.SetAuxData("collisionWarningRcvd", false); plat.SetAuxData("collisionExpected", false); plat.SetAuxData("offRoute", true); end_execute end_behavior
behavior send_warning_message precondition bool collisionExpected = PLATFORM.AuxDataBool("collisionExpected"); bool collisionWarningRcvd = PLATFORM.AuxDataBool("collisionWarningRcvd"); bool trackListEmpty = PLATFORM.TrackList("track_proc").Empty(); return (collisionExpected && !collisionWarningRcvd && !trackListEmpty); end_precondition execute WsfPlatform plat = PLATFORM; if (plat.AuxDataBool("collisionWarningCooldown")) { plat.SetAuxData("collisionWarningCooldown", false); } else { writeln(plat.Name(), " Report: Sending Warning"); WsfLocalTrackList trackList = plat.TrackList("track_proc"); int collisionTrackIdx = plat.AuxDataInt("collisionTrackIdx"); WsfPlatform trackPlat = trackList[collisionTrackIdx].Target(); WsfComm platComm = plat.CommEntry(0); writeln("\t - Comm: ", platComm.Name()); writeln("\t - Destination: ", trackPlat.Name()); if (trackPlat.CommCount() > 0) { WsfComm trackComm = trackPlat.CommEntry(0); WsfMessage warningMessage = WsfMessage(); warningMessage.SetType("WARNING"); warningMessage.SetSubType("collision-expected"); platComm.SendMessage(warningMessage, trackComm); writeln("\t - Warning Sent(", warningMessage.Type(), ")"); plat.SetAuxData("collisionWarningCooldown", true); } else { writeln("\t - Warning Failed: Target has no comms!"); } } end_execute end_behaviorUpdate the CARGO_TASK_MANAGER as follows:
processor CARGO_TASK_MANAGER WSF_TASK_PROCESSOR update_interval 10 sec behavior_tree sequence selector behavior_node all_clear behavior_node entity_detected behavior_node next_selector end_selector selector behavior_node send_warning_message behavior_node reroute end_selector end_sequence end_behavior_tree end_processor
Create a WARNING PROCESSOR as follows:
processor WARNING_PROCESSOR WSF_SCRIPT_PROCESSOR on_message type WARNING script writeln(PLATFORM.Name(), " Report: Message Received"); WsfMessage warningMessage = (WsfMessage)MESSAGE; writeln("\t - Type: ", warningMessage.Type()); writeln("\t - Subtype: ", warningMessage.SubType()); writeln("\t - Origin: ", warningMessage.Originator()); PLATFORM.SetAuxData("collisionWarningRcvd", true); PLATFORM.SetAuxData("collisionExpected", true); end_script type default script writeln(PLATFORM.Name(), "Report: Message Received"); end_script end_on_message end_processor
Add a WARNING_PROCESSOR to the platform type definition of CARGO_AIRCRAFT as follows:
add processor warning_proc WARNING_PROCESSOR end_processor
Update the AIR_RADIO_TRANSCEIVER command block in the CARGO_AIRCRAFT platform type definition as follows:
add comm atc AIR_RADIO_TRANSCEIVER internal_link warning_proc end_comm
Update the aux_data command block in the CARGO_AIRCRAFT platform type definition as follows:
aux_data struct CARGO_AUX_DATA bool collisionExpected = false bool collisionWarningCooldown = false bool collisionWarningRcvd = false int collisionTrackIdx = 0 double lastKnownDistance = -1 end_struct end_aux_data
Finally, in platform_laydown.txt, increase the range of the cargo_radar for cargo-1 by adding the following code to the cargo-1 platform definition:
edit sensor cargo_radar maximum_range 40 nm end_sensor
These additions will provide cargo-1 with a longer range radar. When it detects cargo-2, and calculates that the two aircraft are on a collision course, it will create a warning message, and send it to cargo-2. Upon receiving the message, cargo-2 will reroute by changing its altitude, thus avoiding the collision without requiring cargo-1 to alter its route.
Summary¶
Communications devices are a means of connecting platforms to share information and tracks. Tracks are shared between platforms intuitively as detailed in Quick Start, but tracks are not the only information that can be shared. Though it may require scripting, behaviors, processors, or sensors, nearly any information may be communicated between or among platforms.
