WSF_SUBSURFACE_RADIO_TRANSCEIVER¶
- comm WSF_SUBSURFACE_RADIO_XMTR¶
- comm WSF_SUBSURFACE_RADIO_RCVR¶
- comm WSF_SUBSURFACE_RADIO_TRANSCEIVER¶
comm <name-or-type> WSF_SUBSURFACE_RADIO_TRANSCEIVER | WSF_SUBSURFACE_RADIO_XMTR | WSF_SUBSURFACE_RADIO_RCVR ... Platform Part Commands ... ... Articulated Part Commands ... ... Antenna Commands ... ... comm Commands ... ... WSF_COMM_TRANSCEIVER Commands ... ... WSF_RADIO_TRANSCEIVER Commands ... ... transmitter ... end_transmitter ... receiver ... end_receiver max_underwater_range_filter ... max_communication_depth ... minimum_horizon_angle ... set_VLF_comm ... unset_VLF_comm ... water_attenuation_factor ... ... WSF_SUBSURFACE_RADIO_TRANSCEIVER Commands ... end_comm
Note
WSF_SUBSURFACE_RADIO_XMTR and WSF_SUBSURFACE_RADIO_RCVR are transmit-only and receive-only versions of WSF_SUBSURFACE_RADIO_TRANSCEIVER.
Overview¶
WSF_SUBSURFACE_RADIO_TRANSCEIVER provides a baseline radio implementation that is capable of both transmitting and receiving using a transmitter and receiver. If a communication device is required to transmit or receive only, the WSF_SUBSURFACE_RADIO_XMTR and WSF_SUBSURFACE_RADIO_RCVR types are available. Both of these types are special cases of the WSF_SUBSURFACE_RADIO_TRANSCEIVER type and therefore share the same commands that are listed below in the command section.
The WSF_SUBSURFACE_RADIO_TRANSCEIVER inherits from WSF_RADAR_SENSOR and WSF_COMM_TRANSCEIVER and accepts keywords from the parent classes. Testing has been limited to the function of passing messages between an airborne platform and a second platform that can be at any altitude. Behaviors using more complex routing functions have not been verified.
The WSF_SUBSURFACE_RADIO_TRANSCEIVER provides a communications option that overrides the traditional horizon constraints to permit simulated communications with submerged submarines. Most WSF sensor and communications systems were designed to operate above the earth’s surface. Thus, when altitudes of transmitters or receivers have values of zero or less, then constraints are usually imposed to stop any further processing of the sensing or communications event. When two communications systems are of the WSF_SUBSURFACE_RADIO_TRANSCEIVER type, then messages can be delivered to platforms that are below the earth’s surface.
Two basic methods of communications are considered within this single communications type–very low frequency (VLF) and optical lasers. Both methods are intended to permit users to achieve communications “effects” for simulations. Neither has high fidelity to model the physics involved with the propagation of the waves.
The VLF communication mode results in near-perfect communications that are unconstrained by horizons or terrain. The mode is activated using the keyword set_VLF_comm. When in the VLF mode of operations, constraints are not imposed for absorption, attenuation, or horizon-angle limits.
The default state for WSF_SUBSURFACE_RADIO_TRANSCEIVER results in the state such that VLF communications behavior is not set (unset_VLF_comm) and thus, a set of path constraints will be imposed. The path constraints are intended to provide top-level “effects” that impose constraints which are intended to be consistent with effects for a laser-communications system. Laser-light energy is rapidly absorbed by water. The underwater path lengths (often only a few hundred feet) are usually very short. Unfortunately, the short underwater-transmission-path distances are often within the margins of errors for many range and earth-horizon calculations that are used in mission-level simulations.
Simplifying assumptions are made to permit and to restrict communication events when not operating as VLF:
The intersection of a spherical-earth surface with the straight-line path between transmitter and receiver is used to calculate a distance for the path through the water. This path is used for underwater range limits and the water-path absorption effects. The remainder of the slant-range is used for atmospheric absorption effects.
The method ignores detailed refraction effects, and it also ignores interactions for specific absorption and reflections as the energy penetrates the waves at the air-water boundary. These values are currently within the noise of other error sources. Therefore, detailed laser engineering-level models are more appropriate for study of these features.
The transmission distance is assumed to be approximated by spherical-one-earth-radius horizon distances between platforms. If terrain models are included, the terrain is allowed to block the path along the airborne part of the path.
Users can limit the communications capabilities that might be caused by water-entry-angle limits by using the keyword minimum_horizon_angle. This angle is measured from the horizon upward. Communications with angles less than this limit are stopped. The effect is to require platforms to reduce their slant range to be able to communicate.
Unrealistically long underwater ranges can be restricted by using the keyword max_underwater_range_filter. This range is limited to 1000 meters by default, and users can increase or decrease the value as desired. This keyword has an additional effect of permitting communication over the short range without regard to horizon or terrain.
Commands¶
- max_underwater_range_filter <length-value>¶
Prevents unrealistically long underwater ranges by specifying a range constraint for the underwater portion of the transmission path. This keyword also has an additional effect of permitting communication over the short range without regard to horizon or terrain.
Note
In addition to restricting ranges based on underwater path lengths, users can also restrict the total range by using the maximum_range keyword in the transmitter or receiver block.
Default: 1000 m
- max_communication_depth <length-value>¶
Specifies the maximum depth at which a submerged platform is permitted to exchange communication events. In order to reduce user input issues, the absolute value of the numeric input is used, and the value is converted to be a negative altitude to represent the depth below the surface for the submerged platform.
Default: negative infinity
- minimum_horizon_angle <angle-value>¶
Specifies the minimum angle acceptable for transmissions through the water’s surface. This angle is measured from the horizon upward. Communications with angles less than this limit are stopped. The effect is to require platforms to reduce their slant range to be able to communicate.
Default: -90 deg
- set_VLF_comm¶
- unset_VLF_comm¶
When the command is set_VLF_comm, then all horizon checks are ignored and the message is delivered.
Default: unset_VLF_comm
- water_attenuation_factor <dbratio-value>/<length-value>¶
Specifies a factor by which signals are attenuated as they pass through the water part of the transmission path. The format for data is a number followed by a dB ratio value, followed by a backslash, and then followed by a <length-value>.
A sample entry is:
water_attenuation_factor 0.5 dB/m
Default: 0.0 dB/m
Examples¶
The VLF communications option is activated by set_VLF_comm on WSF_SUBSURFACE_RADIO_TRANSCEIVER.
comm VLF_COMM WSF_SUBSURFACE_RADIO_TRANSCEIVER
debug
set_VLF_comm // Disables horizon checks for long-range comms
transmitter
frequency 30.0 khz
//power 10.0 kw // S/N and jamming are not modeled for VLF at current time
end_transmitter
receiver
frequency 30.0 khz
//maximum_range 500 km //Can limit VLF range
end_receiver
//max_communication_depth -400 ft //Can enforce a depth limit
end_comm
Operations with the optical-line-of-sight communications option is the default for WSF_SUBSURFACE_RADIO_TRANSCEIVER.
antenna_pattern UWCOM_ANTENNA
uniform_pattern
minimum_gain 70.0 db
end_uniform_pattern
end_antenna_pattern
comm UW_COMM WSF_SUBSURFACE_RADIO_TRANSCEIVER
debug
transmitter
frequency 600000.0 ghz
//Note: 'power' value needed to enable attenuation and jamming checks to compute S/I
power 1.0 kw
antenna_pattern UWCOM_ANTENNA
end_transmitter
receiver
frequency 600000.0 ghz
antenna_pattern UWCOM_ANTENNA
end_receiver
water_attenuation_factor 0.3 dB/m //Default = 0.0 dB/m
minimum_horizon_angle 3.0 deg //Default = -90 deg
max_underwater_range_filter 400.0 m //Default = 1000 meters
max_communication_depth -200.0 m //Default = negative infinity
end_comm
