The Researech Of Overlay Architecture And System Scalability For Distributed Virtual Environments

The development of network technology is driving the change of lives of humankind. Another technology—VR- virtual realism, makes the computer interface more"friendly"for people. The combine of the two technologies produces a new research field: distributed virtual environments (Network virtual environments), which build a virtual space for people. It make it possible for peoples to freedom cooperate, compact, interactive each other in this virtual space with the help of computer and network. Distributed virtual environment (DVE) is being its initial state. Its main applications include distributed interactive simulation (DIS), cooperate design, military simulation training, commerce network online games, video conference, remote education and medication. But its application fields are very huge and extensively.The trouble problem of DVE is its scalability. With the user scale increasing to a huge degree, the hardware of system will appear"overload"problem, which will weaken the performance of DVE system. An easy but expensive method for this problem is adding hardware to support large user scale. But the system complex is added together. So it is valuable to study the"soft"technologies (not adding hardware equipments) to help DVE system own a large user scale.The main works of this paper is following this idea. We try to use application layer multicast (ALM), Peer to Peer (P2P) and area of interest (AOI) to the designing of system architecture of DVE system to reduce network load and compute load and enlarge the scalability of DVE system, which will promote the development of large scale DVE systems.There are five innovations in the dissertation as the following. (1)Based on the traditional architecture of DVE system—client/server, importing the idea of P2P, at same time keeping the advantages of C/S, we present a dynamic hybrid DVE architecture. The theory analysis and simulation experiments have shown that it owns good effect on reduce server's load with the help of client node's hardware resource. At the same time it still keep the advantage of traditional C/S architecture.(2) For the characters of one to many and many to many communication model of DVE system we study the application of ALM to DVE communication system to reduce the total network load and compute load. For the real-time character of DVE system, we present the heuristic algorithm of minimum diameter tree for ALM and talk about the effect of the node cost and node degree. It owns the same computer complex with the other heuristic algorithm but get a more optimized minimum diameter tree.(3) Based on"AOI"character of the objects in DVE system, to optimize system communication load we study the AOI based ALM technology and present AOI based multi-tree DVE architecture. Theory analysis and simulation experiments results show that the combine of AOI technology and ALM can greatly reduce server load and improve the scalability of DVE.(4) We present an dynamic share mesh architecture for DVE system to reduce the change probability of network topology for the movement of client avatar in virtual space and reduce the total network load caused by it. This architecture can improve the robust ability of network topology for the dynamic character of DVE system and reduce the communication and control load.(5) We develop a DVE simulation tool by ourselves, which is used to verify theory works. A serious of simulation experiments has been made on it, which validates the result of theory research works. It will also give help for the following research works in the future.