ITT Industries AEROSPACE/COMMUNICATIONS DIVISION

1. INTRODUCTION Recently, there has been increased interest in the simulation of large-scale radio networks. Two major and conflicting obstacles in the simulation of large-scale radio networks are the simulation run time and the accuracy of the simulation results. Since all projects have time constrains, it is often not impossible to conduct lengthy simulation experiments. In our experience, for example, it frequently takes 18 hours to simulate a 120-node radio network with a very detailed model on a top-of-the-line Sun workstation. For larger networks, run times are often impractically long. On the other hand, if a simplified model is used, the results may not be accurate enough for analysis purposes. In [1], we proposed an approach to the simulation of large-scale network by distributing the computation load of a simulation among several workstations. This not only reduces the memory requirements on each workstation but also reduces the execution time (due to parallelism). The simulation architecture introduced in [1] utilizes commercial off-the-shelf software and hardware. OPNET is selected as the tool for network simulation while a fiber-optic ring network is used for communication among workstations. Using a conservative approach [2], a controller is utilized to synchronize execution of events in the workstations. Our distributed simulation system has several advantages. First, it is independent of network topology and its complexity. Second, it is independent of the model and the speed of the workstations used. Third, there is no dependence on the amount of traffic in the network. That is, any traffic, light or heavy, can be used in the simulation. Fourth, there are no restrictions on the type of protocol selected. This means any protocol can be implemented with complete conformity. In addition to the analysis of large-scale static networks, we are interested in the simulation of large-scale dynamic networks. In a mobile environment, the nodes move in a random or predetermined fashion and it is often difficult to track the evolution of the network topology without a graphical display. To solve this problem, we developed a WIN NT program to monitor the progress of the simulation.