Real Time Communication Systems' Simulation With Real Communication Devices In Simulation Loop

This paper presents the new concept of the communication networks' simulations, which enable real time simulations, with the real communication equipment in the simulation loop. In the context of project "Modeling of Command and Control information systems we develop the simulation system, which can be used in the tactical network's planning and evaluation process. This simulation system is based on the OPNET Modeler simulation tool, which is combined by our utilities (TPGen, ModCom), that enables traffic modeling of Command and Control information system (C2IS) used in Slovenian army /1, 2/. We developed also the expert system for automatic simulation results analysis to evaluate tactical networks' performances /3, 4/.In the context of this project we also research the possibilities for real time tactical network simulations, where real tactical units' computers with installed C2IS communication are connected to the simulated wireless communication infrastructure on virtual terrain. The first such simulator is Battlespace communication network planner and simulator, which are described in /5, 6/. This simulator is based on special hardware communication equipment controlled by OPNET simulation tool, where real traffic is influenced by simulation results in real time. In our research we used, instead to the special hardware, the new OPNET Modelers software module System-in-the-Loop (SITL) /7, 8/. This module allows interconnections and packets exchange between real and simulated communication devices or networks. This simulation concept is one of the most important novelties, in the last years and it was also presented in the OPNET conference OPNETWORK 2007 in Washington /10/.Figure 1 shows all possible types of the SITL simulations. Figure 2 shows the example of the real-sim-real SITL simulation type, where real computers communicate through the simulated network. The mechanisms of real time SITL simulations with required software and hardware equipment are shown on the block scheme from Figure 3. In our SITL simulation test case of transmitting voice over IP (VoIP), we connect two external laptop computers across the simulated network as shown in Figure 4. The simulated network, which was modeled in OPNET simulation tool, is more detailed shown in Figure 5. The connectivity between external laptops was tested using ping utility as shown in Figure 6. As VoIP application /15/ we used freeware D-Voicer /12/ installed on real laptop computers. Figure 7 shows the user interface of active D-Voicer application on both, client and server, side. The results of SITL simulation, where real digital voice stream is transmitted through simulated network are shown in Figures 8 and 9.In the third part we present the proposed concept of real time SITL tactical wireless networks' suitable for Slovenian army. The simulation concept is similar as in VoIP example case, described in previous section. The main difference is in the used communication applications, which are for this case Command and Control Information System (C2IS). In Slovenian case this C2IS consists from Iris Replication Mechanism (IRM) in conjunction with Sitaware graphical interface /1, 2, 16/ as shown in Figure 10. Tactical radios of military units we modeled, in OPNET Modeler simulation tool, using standard wireless routers connected over SITL gateway to the real tactical computers. Communication parameters of wireless routers are defined according to communication parameters of real tactical radios and modems. In OPNET Modeler simulation tools are considered influences modeled virtual terrain on wireless links using different radio wave propagation models /13, 19-22/. Simulated tactical network can be very realistically visualized using 3DNV visualization tool as shown in Figure 11.