Tuesday, September 10, 2013

Roots of Distributed Simulation, revisiting SIMNET

Recently I was digging the roots of distributed simulation and trying to make some reading about the history. Any reference that I read starts straightly with the SIMNET effort. The discussion that started in the mid 70's about enabling technologies for distributed and interactive simulation are summarized in many references. Here at this post, I just would like to revisit SIMNET and summarize my notes from the "kind of" famous paper of Duncan Miller and Jack Thorpe,  SIMNET: The Advent of Simulator Networking
It is noted that not long ago but in late 70s, development and application of simulation technology was only available in engineering research and development labs. Considering the 30-40 year operation life-cycle of platforms, this means, we are currently seeing at most the simulators for second generations of the first simulated platforms. Like now we are discussing the training devices for 5th generation fighters or 4th generation (fly by wire) airliners, on the other hand, the first that had training simulators were 4th generation fighters and 3rd generation airliners.
The next interesting note to mention is the motivation back in 78 while they are trying to launch a networked simulation technology development project, was to enable training for improving the collective skills of teams. So it wasn't the platform simulated that challenged the simulation technology back at 70's, but the training goals. Today on the other hand, while we widely use distributed simulation to train teams, we can not think in any other way to simulate large and complex systems (of systems) of today's world.
While SIMNET was launched in 1983, the aim was to demonstrate networked simulation technologies in 4 interconnected testbeds, each of which would have at least 50-100 vehicles.  And due to high data rate requirements of the flight simulators, the project started with ground vehicles. To me, these numbers are still amazing to develop and demonstrate a technology. Aren't they?
Then the project achieves number of important milestones, each of which are cornerstones at today's simulation technology. First distributed simulation concept demonstration in 1984, first real time out of the window demonstration in 1985, first mission level scenario with re-configurable image generators and number of moving objects in 1986 and first air platform in 1987. At the end 250 simulators were installed in 9 operational training sites.
As the last note, maybe, we can list the technologies SIMNET inherited to simulation literature. First to mention of course is communication protocol, Distributed Interactive Simulation (DIS) which will then turn out to be an IEEE standard that is still actively maintained. One of the cornerstones introduced with DIS can be pronounced as the dead reckoning algorithms. Then we need to mention the realistic control/display interactions in manned vehicle simulators were first demonstrated in SIMNET. And lastly, the earliest implementations of Semi Automated Forces (SAF) were introduced in SIMNET.
It was a nice reading for me at all. And I would strongly recommend Miller's paper to anyone who would like to revisit the history of distributed simulation.  

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