Interoperability Overview

Bring multiple simulations together for better training and research outcomes

Interoperability is a key need when one simulator has to connect to the rest of the simulated world, via a network. This network may link simulators that are as close together as side by side — using a local area network (LAN), or as far apart as facilities located across the country or the globe — using a wide area network (WAN).

In distributed simulation environments, each simulator is responsible for computing its own behaviour and condition and presenting this state to the network for the benefit of all the other items and simulators on the network. This is important, as each simulator will send interactions to represent events that happen within the simulation, and all simulators are responsible for evaluating those interactions to determine if they have any effect on their own behaviour or condition.

The Network Interface

The network interface is a software module that does the work of connecting to the network, publishing the simulator’s position and status, and listening for all the updates from the other network items. This software makes a list of everything so that the host simulation and/or the image generator has knowledge of what else is within the virtual environment. The simulator will use this knowledge to check for collisions with other entities and the effect of interactions on the simulator itself. The image generator, in turn, will use this information to render a 3D model of each entity and special effects depicting the interactions, like weapons fire and detonations.

Interoperability Standards

In the 1990s when simulators were first being connected into networks of distributed interactive simulations (DIS), government, academia, and industry came together to define an object model and a way to encode the information into packets — ‘protocol data units’ or PDUs. This first DIS standard made interoperability between simulators an efficient and predictable science. As the complexity of simulation networks grew and the variety of objects and interactions that simulators needed to communicate increased, a new standard was developed called the ‘High Level Architecture’ – HLA for short. Both standards have evolved through years of experience and collaboration and have been formalised and adopted by well-respected standards organizations — Simulation Interoperability Standards Organization (SISO) and the IEEE.

Setting Up the Network

Setting up a network can be simple for small local networks and very challenging for larger wide area networks that string together multiple sites and connecting simulators which use differing protocols. So, having tools that make the process of setting the network up, monitoring the network, and dealing with issues as they arise, is critical to large simulation success.

(Above abridged from The Tech Savvy Guide to Virtual Simulation written & published by VT MAK)