An Efficient Synchronization Mechanism Adapting to Dynamic Network State for Networked Virtual Environments

One of key issues in multi-user interactive applications is to provide a consistent, shared view among participants while maintaining interactive performance. The buffered synchronization mechanism can support a consistent view by holding events in buffer until a fixed amount of time called playout delay expires and executing them at the same time at all participants. However, if events get lost or delayed, consistency may not be kept among participants, which causes an overhead to recover the lost information. On the other hand, the execution of events should be delayed more than it could have happened when the events arrive earlier than the playout delay. In this paper, we propose an efficient event synchronization scheme adapting dynamically to a network state that ensures a consistent view among participants while maintaining interactive performance. Each participant determines the playout delay dynamically based on the estimated network state. If a network state is unloaded, the playout delay decreases. It increases in case of a loaded network state. The simulation results show that the proposed scheme provides more consistent view among the participants than the static scheme when the loaded network state continues and improves the interactive performance when the network state is unloaded.