National Sun Yat-sen University Institutional Repository:Item 987654321/30407

行政院國家科學委員會補助專題研究計畫成果報告

※※※※※※※※※※※※※※※※※※※※※※※※※※

※

※

※

應用高階架構做網際網路模擬環境之設計

※

※

※

※※※※※※※※※※※※※※※※※※※※※※※※※※

計畫類別：□個別型計畫

□整合型計畫

計畫編號：NSC 89-2218-E-110-003

執行期間：

89 年 8 月 1 日 至 90 年 7 月 31 日

計畫主持人：李宗南

計畫參與人員：盧天麒 江傳文 周大源 謝明淑 余 謙 簡銘伸

林家瑋 林明堂

本成果報告包括以下應繳交之附件：

□赴國外出差或研習心得報告一份

□赴大陸地區出差或研習心得報告一份

□出席國際學術會議心得報告及發表之論文各一份

□國際合作研究計畫國外研究報告書一份

執行單位：國立中山大學資訊工程系

中

華

民

國

90

年

10

月

31

日

應用高階架構做網際網路模擬環境之設計

Design of Web-based Modeling and Simulation Envir onment Using High

Level Ar chitectur e (HLA)

計畫編號: NSC 89-2218-E-110-003

執行期間: 89 年 8 月 1 日 至 90 年 7 月 31 日

主持人：李宗南 教授 國立中山大學資訊工程系

計畫參與人員：盧天麒 江傳文 周大源 謝明淑 余 謙 簡銘伸 林家瑋 林

明堂

一、中文摘要 本計劃的目的是設計與實作出一個以網 路為基礎的多樣化資料處理系統架構，用 來做為一種分散式計算的環境。但是這個 系統不只能在網路上提供合作和分散式的 功能，還允許多人動態地加入參與整個環 境的互動，包括共同討論、設計、資料上 傳與下載、甚至執行他們自行設計的應用 程式來分享或使用資源。除了程式的本體 之外，另外為了增資系統的效能，我們還 加入了一套根據網路負載量而動態調整程 式執行方式的機制。 關鍵字：高階架構、協調機制、資料分散 管理、網路分散模擬環境

Abstr act

In this project, we present the design of a Web-based environment to support large-scale distributed simulation using Java and IEEE standard P1516 – High Level Architecture (HLA) framework and rules. The proposed HLA-based environment provides an architectural foundation to enhance interactivity, portability, and interoperability for Web-based simulations. A three-level control mechanism (3LCM) was implemented to HLA-based middleware, federateServer, in order to adaptively maintain information consistency and minimize message traffic for distributing information among client hosts and the federateServers. A dynamic filtering strategy (DFS), associated with the data distribution management (DDM) in the HLA RTI, is

proposed to minimize false positive updates and enhance the filtering efficiency of subscription regions within an HLA federation. To verify the feasibility of this prototype, a distributed discrete event simulation application in Java was developed and performance of the proposed modeling design and Java RMI’s distributed object model is presented. From the experimental results, we have shown that the proposed environment based on HLA using 3LCM and DFS is workable and practical for supporting a large-scale distributed simulation

Keywor ds: Distributed interactive simulation, high level architecture, data distribution management, networked virtual environment

二、緣由與目的

Web-based simulation [1], which is a grand-challenge technology, allows multiple users connected to a Web-based networked synthetic environment to interact simultaneously with one another and facilitate interoperability among simulations. This has become increasingly important for military training, in entertainment, industrial and academic sectors. A variety of relevant research areas have been studied within this domain [2], such as network architecture design [3], distributed virtual environments [4], simulation using Web technologies [5], Web-based modeling design [6], and so on. According to Fishwick et al. [7], the potential impact of simulations using Web

technologies tends toward three areas, education and training, publications, and simulation programs. However, one of the bottlenecks for developing a workable networked simulation environment is the limited network bandwidth. Attempts to overcome the bandwidth limitation have focused on two issues: increasing the network speed, and reducing unnecessary information transmissions over the network.

三、

研究方法與成果

In order to provide a more flexible and practical Web-based distributed simulation platform, we incorporate the three-level control mechanism [8] with an HLA federation execution. The incorporation of 3LCM with federateServer can greatly increase the number of client hosts. In terms of federation management in HLA, we let an individual host execute the three-level control mechanism (i.e. we designate this host as a federateServer) as a federate participating in a federation. However, all of the interactions, communications, and regulations of federates must rely upon RTI services. The federateServer (i.e. an HLA federate) can join the federation by applying the services of the RTI federation management. Based on a common high-level simulation architecture within the HLA and the proposed architectural design, it can support and facilitate the interoperability of all types of models and simulations on a large-scale Web-based distributed simulation environment.

The HLA is a convenient and powerful modeling and simulation (M&S) platform to develop distributed simulation applications. Compared with the RMI distributed object model, whose turnaround time increases dramatically as the number of client hosts increases, the turnaround time for the RTI distributed model just slightly increases. Simulation results show that the incorporation of the three-level control mechanism (3LCM) with HLA-based middleware, federateServer, can adaptively maintain information consistency and

minimize message traffic for distributing information among client hosts and the federateServers. The result shows that the environment remains almost constant turnaround time over all range of simulation, in other words, it can support even more number of clients and provide as much information consistency as possible for a large-scale Web-based distributed simulation. In general, when a simulation environment needs to support a large number of users, a federateServer should be used, otherwise one can directly connect the client host to the federation via the RTI.

Current version of the RTI does not automatically provide information filtering based on known functions, it only determines which federates should discover which objects by matching subscription and update regions. Therefore, we have proposed a dynamic filtering strategy (DFS) to minimize false positive updates and enhance the filtering efficiency of subscription regions on continuous coordinates. The simulation results show that the turnaround time for the federation with DFS function is smaller than the turnaround time for the federation without DFS function. Though the difference is not very significant in the experiment, we expect that it becomes more important, when the number of objects and regions in the routing space is large. From the experimental results, we have shown that our design, using HLA, is a workable and practical simulation prototype.

四. 計劃成果自評

In this project, we have explored the mechanism required to support a large-scale distributed simulation on the Web, and adopt High-level Architecture (HLA), which was developed by the Defense Modeling and Simulation Office (DMSO), to provide a more flexible distributed simulation environment. From the experimental results show that the design using HLA is a workable and practical simulation prototype. The results of this project has been published in ACM Trans. on Modeling and Computer Simulation, 2000[ 9]。

五、參考文獻

[1]

P

age, E. H. 1998. The Rise of

Web-Based Simulation: Implications for the High Level Architecture. In Proceedings of the 1998 Winter Simulation Conference (Washington, DC, Dec. 13-16), 1663-1668.

[2]

Z

yda, M. and Sheehan, J. 1997. Modeling and Simulation: Linking Entertainment & Defense, National Academy Press. ISBN 0-309-05842-2.

[3]

M

acedonia, M. R., Zyda, M. J., Pratt, D. R., Brutzman, D. P., and Barham, P. T. 1995. Exploiting Reality with Multicast Groups: A Network Architecture for Large-scale Virtual Environments. IEEE Computer Graphics & Applications. (Sep.), 38-45.

[4]

C

him, Jimmy H.P., Lau, Rynson W. H., Si, A., Leong, H. V., To, D., Green, M., and Lam, M. L. 1998. Multi-Resolution Model Transmission in Distributed Virtual Environments. In Proceedings of the 1998 ACM Symposium on Virtual Reality Software and Technology (Taipei, Taiwan, Nov. 2-5), 25-34.

[5]

E

vans, E and Rogers, D. 1997. Using Java Applets and CORBA for Multi-User Distributed Applications. IEEE Internet Computing Magazine. (May/June), 43-55.

[6]

P

age, E. H., Griffin, S. P. and Rother, S. L. 1997. Providing Conceptual Framework Support for Distributed Web-Based Simulation within the High Level Architecture. In Proceedings of SPIE: Enabling Technologies for Simulation Science II (Orlando, Fl, April 13-17), 287-292.

[7]

F

ishwick, P. A., Charnes, ed. J. M., Morrice, D. J., Brunner, D. T., and Swain, J. J. 1996. Web-Based Simulation: Some Personal Observations. In Proceedings of the 1996 Winter Simulation Conference (Coronado, CA, Dec. 8-11), 772-779.

[8]

L

u, T. C., Lin, M. T., and Lee, C. N. 1999. Control Mechanism for

Large-Scale Virtual Environments. Journal of Visual Languages and Computing. 10, 1 (Feb.), 69-85.

[9] Tain-chi Lu, Chungnan Lee, Ming-tang Lin, and Wen-yang Hsia, “Supporting Large-Scale Distributed Simulation Using HLA,” ACM Trans. on Modeling and Computer Simulation, Vol 10, No. 3, pp 268-294, July, 2000