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Distributed virtual reality system of local physical clock synchronization

Round-trip time between these two values are precise and measurable. Gusella and Zatti 3.1.3Berkeley algorithm describes an internal synchronization algorithm. In this algorithm, suppose a group of computers, select one of the co-ordination as the host, the host periodically call the other to synchronize the computer (known as the slave machine). Slave unit's clock value them back to the host. Host by observing the round-trip time to estimate even if they do the local machine. This is somewhat similar to Cristian methods, the difference is obtained by calculating the value of the algorithm (including its own clock reading of the average). From the probability point of view, such an approach can cover a single clock offset. In addition, the host sends the clock of each slave machine to adjust the amount needed to update and not the current time,[link widoczny dla zalogowanych], so it will not because the message delivery time and causing more uncertainty. 3.1.4 Network Time Protocol Cristian and Berkeley algorithm method is mainly applied within the enterprise network. The Network Time Protocol (NetworkTimeProtocol, m) defines the time of service architecture and time information published on the Internet protocol. NTP's main features are: first, to provide a service, so users across the Internet to accurately synchronized with UTC. Second, to provide a connection loss in a long reliable service to survive, mainly by providing more than Kang to provide more up to the path to re-configure the server to continue to provide services. Again, enabling customers to effectively re-synchronize frequently in order to offset that exist on most computers offset rate. Finally, it provides protection against the interference of the time service, whether accidental or malicious. 4, distributed virtual reality system, a local physical clock synchronization of the following is a simple local distributed virtual reality system diagram (Figure 1). I l reference clock synchronization module clock synchronization module I L_1 local entities control module clock lI lI lI external coordinate conversion module analysis module lI foreign entity attribute data communication module local data communication module lI l1 local data communication module I Figure 1 client server local Distributed Virtual Reality System Model main draw on the model of physical clock synchronization Cristian method, where a server to manage multiple clients, form a local virtual reality system, the server is responsible for multiple clients local time synchronization. Firstly, the system server integrated with the system reference time other local systems to achieve external synchronization. Then the system clock synchronization system of sub-module local physical clock synchronization. To ensure the long term be able to synchronize the entire system, there are several improvements: First, the algorithm of Cristian made some corrections and clock synchronization module on each startup, the server periodically sends a message to each client, by calculating the round-trip time estimates the client's local time, and to his readings of the clock and they do mean operation. The one hand to cover a single clock offset, on the other hand only be sent to each client's need to adjust the amount of the clock can be eliminated because of the many messaging brings uncertainty. Second, the migration rate of each machine to observe, if the local machine's clock has to go fast or go slow trend, by adjusting the clock's update frequency to be modified (software or hardware). Third, the use of data filtering algorithms NTP server and the client to estimate the minimum offset, precision reference system to determine the minimum period to resynchronize the server. Through the above method, it basically can be achieved in a distributed virtual reality system,[link widoczny dla zalogowanych], the physical clock synchronization problem, and can achieve high accuracy. 5 Conclusion This virtual reality system for distributed clock synchronization with the physical theory has done some preliminary research. When it comes to the distributed virtual reality system, the synchronization of physical clocks put forward higher requirements,[link widoczny dla zalogowanych], this introduces some of the ways to achieve such a system also has some reference value. References [1] GeorgeCoulouris, JeanDollimore, TuneKingberg,[link widoczny dla zalogowanych], Jin Beihong, such as translation. Distributedsystemconceptsanddesign. Machinery Industry Press, 2004. [2] Zhang Maojun. Virtual reality system. Science Press, 2OO2. [3] Ding-Fang Chen, Ya-Bo Luo. Virtual design. Machine Cross Industry Press,[link widoczny dla zalogowanych], 2OO2. [4] Zhang Yong, Deng Zhongliang. The Environment of virtual reality research network communication. Computer Engineering and Applications ,2003,10-13.

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