In: IEEE Trans. on Systems, Man, and Cybernetics; B: Cybernetics, Vol. 30, No. 5, pages 737-756. 2000.
Abstract: Despite their attractive properties, networked virtual environments (net-VEs) are notoriously difficult to design, implement and test due to the concurrency, real-time and networking features in these systems. Net-VEs demand high quality-of-service (QoS) requirements on the network to maintain natural and real-time interactions among users. The current practice for net-VE design is basically trial and error, empirical, and totally lacks formal methods. This paper proposes to apply a Petri net formal modeling technique to a net-VE, NICE (narrative immersive constructionist/collaborative environment), predict the net-VE performance based on simulation, and improve the net-VE performance. NICE is essentially a network of collaborative virtual reality systems called the CAVE (CAVE automatic virtual environment). First, an extended fuzzy-timing Petri net (EFTN) modeling and analysis techniques are presented. Then EFTN models of the CAVE, NICE, and transport layer protocol used in NICE: transmission control protocol (TCP) are presented. It is shown that there is a possibility analysis based on the EFTN model for the CAVE. Then, by using these models and Design/CPN as the simulation tool, various simulations were conducted to study real-time behavior, network effects and performance (latencies and jitters) of NICE. The simulation results are consistent with experimental data.
Keywords: Design/CPN, NICE, discrete-event simulation, fuzzy Petri nets, fuzzy timing, networked virtual environments, performance analysis, quality-of-service.