Navy Communications System Modeling and Simulation

Underwater Communications

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Modeling and simulation of communication systems are essential for users to develop implement and analyze a network in real-time without the risks. To meet the need, SCALABLE developed the EXata communications system simulation software. EXata is a comprehensive suite of tools for emulating large wired and wireless networks. EXata provides a cost-effective and easy-to-use alternative to physical testbeds that typically have high equipment costs, complex setup requirements and limited scalability.

The user is able to work with a high performance, high fidelity, communications system simulation engine, in which an extremely accurate “virtual” models environment can be created, and then analyzed through a series of scenarios to identify where there are weak points or failure modes that need to be addressed. This allows for a lab-based risk reduction work environment that is repeatable, verifiable and highly cost effective.

EXata’s ability to provide communications visualization and communications system simulations is why the US Navy chose to leverage EXata simulation software to implement underwater communications modeling and communications visualization. EXata will model acoustic and optical communications and will help the Navy to analyze and assess network performance including Anti-Access/Area Denial (A2/AD) and Disconnected, Interrupted, and Low-bandwidth (DIL) environments.

EXata and the US Navy are able to prepare for future warfare and find new and innovative ways to make use of underwater communications. Unmanned underwater vehicles (UUVs) hold promise for stealthy surveillance, particularly in areas that pose difficulties for submarines such as shallow waters and channels. However, the underwater communication environment that is needed for command and control, and transfer of sensor data has its own set of challenges. Acoustic channels are subject to distortion, multipath effects, and noise, and have very low data rates. Underwater laser can achieve high data rates but is very limited in range due to absorption in sea water. UUVs have limited battery life and must return to underwater stations to recharge and transfer data, which must then be transferred to the surface or shore. Swarms of UUVs will need to be controlled in hostile environments.

EXata will model acoustic and optical communications, while Scenario Player will provide communications visualization to help the Navy analyze and assess network performance including Anti-Access/Area Denial (A2/AD) and Disconnected, Interrupted, and Low-bandwidth (DIL) environments. EXata will enable analysis of underwater network resiliency and self-healing performance, and help the Navy to develop network policies that will assure missions.

Using Network Digital Twins to Model Multi-domain Battlefield Networks

Multi-domain network planners and operators can use digital twins to adapt to evolving traffic and resource demands as well as to changes in protocols and technologies. Using a network digital twin, they can safely experiment with different solutions, determine the optimal configuration for their networks and assess their resiliency to cyberattacks in a high fidelity, easy-to-use, easy-to-integrate, real-time, or faster-than-real-time live-virtual-constructive environment with in-depth visualization and analysis capabilities. This webinar will describe and demonstrate how SCALABLE’s emulation platform, EXata, can be used to create and leverage multi-domain network digital twins including:

  • Multi-Domain Network Digital Twin Technology
  • Multi-Domain Network Digital Twin Applications and Benefits
  • Multi-Domain Network Digital Twin Capability Demonstrations

Multi-Domain – Seabed to Space

High-fidelity, physics-based undersea and multi-domain cyber, communications and networking modeling and simulation. Underwater Communication Networks (UCN) are enablers of current and future military and commercial applications involving undersea exploration, monitoring, and surveillance.

  • UCNs simulator can be used to investigate real-time underwater command and control, data transfer, and exfiltration
  • UCN simulators are used for training under realistic operating conditions in both military and civilian contexts
  • UCN-X, a novel M&S system for UCNs based on the EXata network can be used for simulation of end-to-end communications over a network that spans underwater, afloat, ashore, air and space-based assets


Underwater Communications Network Library

The Underwater Communications Networks (UCN) Model Library can be incorporated into QualNet, EXata, and NDT, adding support for underwater acoustic and optical communications. The UCN Model will enable analysis of underwater network resiliency and self-healing performance, and provide communications visualization and communications system simulations. It provides high fidelity simulation of underwater acoustic and Free-Space Optical (FSO) communications.

Propagation models:

BELLHOP Acoustic Propagation Model: BELLHOP is a beam tracing model for predicting acoustic pressure fields in ocean environments. It allows for variations in the Sound Speed Profile (SSP) which refract the beam away from the straight line path. Reflection of the ray from the ocean surface and seabed are also calculated. It also optionally includes the geometric spreading and Thorp absorption processes. Since the beam tracing is quite slow to run, the properties of the environment are calculated prior torunningthe simulation in EXata. The values obtained from beam tracing are loaded into the simulation to providepathloss, arrival delay, and multi-path interference values.

Thorp Acoustic Pathloss Model: – Sound losses in the ocean are due to both spreading and absorption, both are modeled in UCN. In deep water, the spreading will be spherical, in shallow water the spreading will be cylindrical. In both cases, the loss will be in an inverse power of the distance between source and receiver. Absorption is due to effects of molecules dissolved in the water, this is frequency dependent, it results in an energy loss that is an exponential function of distance. The Thorp model of absorption includes terms for the most important modes of acoustic absorption and is valid for a range of frequencies between about 100 Hz and 50kHz.

Beer-Lambert Optical Pathloss Model: Light traveling through seawater is both scattered and absorbed. The coefficient of absorption and scattering are wavelength dependent and are also a strong function of the minerals dissolved in the water and particulate matter floating in it. These parameters are often referred to as the Intrinsic Optical Parameters (IOPs) of the medium.

Physical Layer Models:

The Acoustic PHY model is based upon the Abstract PHY model. The Abstract PHY model is described in Wireless Model Library.

There are many sources of sound in the undersea environment. In the frequency range used for acoustic communications, the dominant sources of noise are wind and shipping. Other ambient noise sources include turbulence, rain, and thermal noise. Anthropogenic sources also include communications devices, sonar, and explosions dues to seismic exploration. Marine life, most notably whales and shrimp, can also contribute to noise. When a signal is being received at an underwater communications node, the receiver will also pick up the ambient noise. This noise, combined with signals from other transmitters, and the inter-symbol interference, reduces the receiver’s ability to correctly discern the received signal.

The Optical PHY model is based upon the Abstract PHY model, which is described in Wireless Model Library. The Abstract PHY model is extended to include geometric factors of beam transmission and reception, an Optical Noise model, and a receiver model that supports Non-Return to Zero On-Off Keyed (NRZ-OOK) encoding scheme. The Optical PHY model uses a combination of an antenna pattern along with some geometric terms to determine the strength of the received signal. The antenna model supports the orientation of the platform that the transmitter or receivers are mounted on along with the mounting angle of the receiver relative to the pointing direction of the platform.

The Optical Noise model includes sources of noise from scatted sunlight and internal receiver noise. The sun is a powerful source of light, some light from the sun reaches the receiver due to scattering in the water. The single scattering model is used to approximate the sunlight entering the receiver, light is scattered out of the beam but not back into it. The light scattered into the receiver depends on the pointing direction of the receiver, the depth, and the IOPs.

Related Resources

Maritime Communications & Network Modeling and Simulation

Live-Virtual-Constructive (LVC) models facilitate the use of real-time network emulations and integrations
with live hardware and software to create at scale network representations for in-field or lab-based use.

Network Digital Twins for 21st Century Wargaming

Effective wargaming must be part of an integrated process, requiring accurate modeling of networks and their behavior to correctly predict scenario outcomes.

Underwater Communications Networks Model Library

The Underwater Communications Networks (UCN) Model Library can be incorporated into QualNet, EXata, and NDT, adding support for underwater acoustic and optical communications.

Key Features of EXata

Real Time Emulator

Seamlessly interface with other live equipment and applications

Cyber Testing

Test the resiliency of your network to Cyber Attacks

Network Digital Twin

Test your network in a low-cost, zero-risk environment


Model thousands of nodes with parallel execution

Model Fidelity

Models simulate accurate real-world behavior

Commercial enterprises, educational institutions, and governmental organizations around the world all depend on reliable, effective networks to deliver business-critical, mission-critical communications, and information. SCALABLE maintains a highly experienced group of technical professionals to support customers and projects of any scale and solve challenging problems with our advanced network digital twin technology.

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