分散式連網模擬環境之即時協調機制設計

根據美國國防部一九九五年十月頒佈的『模式與模擬發展計劃』內容所述，其計劃之首要目標乃為模式與模擬建構出一套完整的高階模擬架構(High Level Architecture, HLA)，此架構將成為美軍上下一貫之標準並廣泛運用於各類不同功能之軍事系統中。該技術架構之主要目的在於達成不同的模擬系統間之交流互動，並且提昇模擬系統和軟體元件之可重複使用率。而分散式模擬系統的各類需求是相當多元化的，HLA 可以提供較為一般性的骨幹架構以促成模擬系統的完整互動。在真實世界中，軍事衝突是沿著一條時序(Time Line)來依序發生，因此在電腦兵棋的推演當中必須有效的模擬出相同的軍事衝突時序。而推演運行的方式就是指於推演中模擬真實世界時序的前進方式，推演所經過的時間必須精確地模擬，並確保物理法則以及推演之完整性/真實性。每一個演習訓練均有其推演模擬的起始日期與時間，電腦兵棋系統的推演方式通常使用連續式計時，必要時可以配合步階式計時以調快戰演比。因此在分散式模擬架構下的電腦兵棋系統，必須也能夠很精確的讓事件在正確的時序發生，並且要達到同步模擬的狀態。舉個例子：模擬演訓中，一連串的命令並不一定是依照執行先後順序下達的，所以，在分散環境下必須要確保較早時序的命令不會被忽略而時序較晚的命令反而先被執行，亦即必須保持正確之因果關係。而這些時序控制可以在兩種層面上實現，一個是在作業系統層面，稱為執行基礎(Run-Time Infrastructure – RTI) ，另一種是在應用程式的層面，稱為federate。本論文所欲探討的即時時間管理服務即從此兩個層面來研究，也就是說，從執行基礎(RTI)的角度來研究如何設計即時時間管理模組，來改良現有之執行基礎(RTI)軟體的設計方式；另一個研究方向就是從federate角度來探討如何在現有執行基礎(RTI)軟體的限制下，提出federate的設計方式與運作規範以達即時性需求。因此本論文所研究的議題為: z 設計符合即時性需求的HLA Time Management 機制，以及滿足deadline 條件的LBTS 計算公式與演算法。 z 研究real-time 系統與lookahead 值之間的關係，以及探討降低「網路延遲」因素的 lookahead 值設定方式。 z 藉由實驗來提出對於不同網路環境、real-time 系統與lookahead 值三者之間的關係式，以利日後建構即時性模擬環境的依據。

關鍵字

高階模擬架構；執行基礎；時限；同步

並列摘要

In the real world scenario, the military conflicts have been taking place along the timeline. Hence, in order to realistically simulate the conflicts, the model of the software needs to effectively advance the simulation time in the same sequence. In other words, the software has to progress the events in the same order to ensure the causal and physical accuracies. Since simulation has the initial and ended time, the software is usually a successive time-stepping through the simulation. The time scale may also be changed during this period to coordinate with the time-step simulation. Hence, the time synchronization among distributive war game softwares is essential for the causal correctness of the simulated scenario. Time synchronization can be carried out in two levels. One is in the operating system level, called RTI in HLA terminology, and the other is the application level, called federate in HLA terminology. This dissertation attempts to have an in-depth research on the time management of the distributed simulation from these two levels. First, this research will study the real-time management issue from the perspective of the RTI. This study plans to ameliorate the time management mechanism of the existing commercializes RTI software. On the other hand, this research will also discuss the federate’s design issue in the real-time simulation. That is, the issue of how to design a real-time federate under the constraint of existing RTI software. In all, this dissertation would have some research issues as follows: z Design the LBTS equation and algorithm that could satisfy the hard deadline requirement. z Research the relationship between real-time system and lookahead value. z Use experiments to study the relationship among the different network environments, real-time systems and lookaheads. The relationship is valuable in the design and development of future real-time simulation environment.

並列關鍵字

High Level Architecture (HLA) ； Run-Time Infrastructure (RTI) ； Deadline ； Synchronization

參考文獻

[ABBO88] R. Abbott and H. Garcia-Molina, “Scheduling Real-Time Transactions,” SIGMOD RECORD, vol. 17, no. 1 (March 1988), pp. 71-81.

[ABKL05] Azzedine Boukerche, and Kaiyuan Lu, A Novel Approach to Real-Time RTI based Distributed Simulation System. Proceedings of the 38th Annual Simulation Symposium (ANSS’05) IEEE.

[CLIU73] C.L. Liu and J.W. Layland, “Scheduling Algorithms for Multiprogramming in a Hard Real Time Environment,” Journal of the ACM, vol. 20, no. 1 (January 73), pp. 4661.

[DMSO98] Defense Modeling and Simulation Office, “HLA glossary”, 5 Feb., 1998.

[FISH95] Fishwick, P. A., Simulation Model Design and Execution, Prentice Hall, New Jersey, 1995.

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分散式連網模擬環境之即時協調機制設計

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