On network simulation for performance evaluation of real-time Internet-based teleoperation

In this paper we discuss various approaches to simulating real-time Internet-based teleoperation systems. Focus is on simulation of the communication link, which is a critical component in teleoperation systems. Some of the objectives of simulations are to compare the performance of operators in fixed network conditions and to compare the performance of an operator over varying network conditions. To accomplish these goals, NS-2 is used with modified classes to model teleoperation systems. Two methods for simulation are co-simulation, where the system dynamics and the network are simulated at the same time, and sequential simulation, where the network and system dynamics are simulated in separate steps. The differences in accuracy and implementation are compared by an illustrative experiment. This paper also investigates methods for interactive simulations, which receive command inputs from an external master device controlled by a human operator. The real-time scheduler and network emulation are NS-2 addons that enable interactive simulations. Since computation time is an important limitation for simulations, a sequential simulation approach can be used for large-scale networks.