Modeling and performance analysis using extended fuzzy-timing Petri nets for networked virtual environments

Despite their attractive properties, networked virtual environments (net-VE s) are notoriously difficult to design, implement, and test due to the conc urrency, real-time and networking features in these systems. Net-VEs demand high quality-of-service (QoS) requirements on the network to maintain natu ral and real-time interactions among users. The current practice for net-VE design is basically trial and error, empirical, and totally lacks formal m ethods. This paper proposes to apply a Petri net formal modeling technique to a net-VE-NICE (narrative immersive constructionist/collaborative environ ment), 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 , we introduce extended fuzzy-timing Petri net (EFTN) modeling and analysis techniques. Then, we present EFTN models of the CAVE, NICE, and transport layer protocol used in NICE: transmission control protocol (TCP), We show t he possibility analysis based on the EFTN model for the CAVE. Then, by usin g these models and design/CPN as the simulation tool, we conducted various simulations to study real-time behavior, network effects and performance (l atencies and jitters) of NICE. Our simulation results are consistent with e xperimental data.