一种基于历史的DDM实现方法

DDM是HLA接口规范中定义的六大服务之一。它允许盟员声明其在路由空间中的更新区域和定购区域,从而达到减少HLA盟员间数据交换量的目的。它是RTI服务实现效率的关键,其核心问题是如何减少需要匹配的区域,以减少计算量。文章简要介绍了现有的几种方法,并分析了其各自的特点,在此基础上提出了一种基于历史的DDM方法。     

在HLA／DDM中多播组的分配方法

DDM是HLA接口规范中定义的六大服务之一,它允许邦员声明其在路由空间中的分布区域和定购区域,从而达到减少HLA邦员间数据交换量的目的。具体实现方法是数据过滤,其核心问题是如何将邦员中具有相似的公布区域或定购区域的对象聚集到一个多播组中。解决这个问题的传统方法是基于固定网络的方法,但该法存在一定缺陷。本文提出了
三种新的可选方法,并对这些方法的过滤效果和计算开销进行了评估。     

Scalability and Performance Evaluation of DDM-Based Aggregation/Dissaggregation Protocols for Large-Scale Distributed Interactive Simulations Systems

Aggregation/disaggregation is a method for implementing multi-resolution simulations within a High Level Architecture (HLA) federation. HLA is a U.S. Department of Defense (DoD) developed standard to facilitate linking different types of simulations, in various locations, to form an or interactive, full-scale simulation, called a federation. Data Distribution Management (DDM) is a High Level Architecture/Run-time Infrastructure (HLA/RTI) service that manages the distribution of state updates and interaction information and controls the volume of data exchanged, in large-scale distributed simulations. The purpose of HLA is to promote interoperability and reuse among heterogenous simulations, including those simulations that offer varied levels of resolution, to provide practical training to military personnel of different ranks. The purpose of Aggregation/disaggregation is to ensure consistency in state updates between federates simulating objects at various levels of resolution. This paper focuses on the scalability of aggregation/disaggregation with different DDM implementations and examines the effects, on performance of large-scale simulations. We implement a federate-based aggregation/disaggregation scheme, originally introduced in [TAN01], with a tank dogfight scenario, aggregating five tanks into one tank battalion and disaggregating the battalion back into five individual entities (tanks). The DDM methods we analyze consist of the Fixed Grid-Based method, the Dynamic Grid-Based method and the Region-Based method. In [TAN01], testing of this federate-based aggregation/disaggregation was limited to a dual federation and a single DDM scheme. In an effort to determine the scalability of aggregation/disaggregation, with three methods of DDM, we measure the communication overhead and analyze performance during a federation execution. We present the results of extensive testing, varying the number of aggregation/disaggregation requests, the number of multi-resolution federates participating in the federation, the number of objects, the number/size of the grids and report on the performance evlauation of our protocols using an extensive set of simulation experiments. This work was partially supported by Grants from NSERC, Canada Research Chairs Program, Canada Foundation for Innovation, OIT/Distinguished Researcher Award.     

HLA联邦成员设计中同步问题的研究

基于HLA的分布交互式仿真是目前仿真领域的研究热点。由于HLA联邦是由多个HLA联邦成员协同组成的一个分步交互式仿真系统，所以在HLA联邦成员设计中必须考虑同步问题。该文系统分析了HLA联邦成员设计中的同步问题，包括联邦成员启动阶段的同步问题和仿真阶段的同步问题，并对相应的同步问题给出了非常实用的解决方法。     

聚类的组播组分配策略在DDM中的实现

DDM(DataDistributionManagement)服务是高层体系结构HLA(HighLevelArchitecture)中定义的六大服务之一,它主要目的是通过减少网络间不相关数据的分发,提高网络的利用效率。一种常用的DDM优化方法是使用组播,组播是一种非常适合一对多的通信方式,它能够将更新数据发送到一个指定的定购者子集里。传统的DDM组播使用固定网格分配算法,在资源使用和数据发送方面存在一定的问题,不适合超大规模的仿真。本文在固定网格算法基础上提出了一种基于聚类的组播组分配算法,通过聚类,将固定网格的组播组进行合并,减少组播组的使用数量,提高网络资源的利用率,最后从实验结果上分析了聚类组播算法的优缺点。     

一种基于网格的DDM区域匹配算法

在大规模分布式交互仿真中,数据分发管理(DDM)的重要功能是减少联邦成员接收不相关数据,实现数据过滤。它允许联邦成员在路径空间中通过更新区域或订购区域表达它们要发送或接收数据的范围,通过区域匹配运算确定数据供求关系,实现数据过滤。其关键是如何减少需要匹配的区域,以减少区域匹配运算量,文章以此为目的,提出一种基于网格的区域匹配算法。     

基于StarLink的民意模型的改造和测试

针对基于StarLink的民意模型,首先在理解高层体系结构的基础上,将它设计为具有三类联盟成员的联盟,接着详细地分析了联盟成员之间的信息流程和每类联盟成员内部的信息流,最后给出了基于该联盟的仿真实验方案和结果。实验结果表明,StarLink能够有效支持大中规模的仿真系统应用。     

HLA仿真技术综述

建模与仿真高层体系结构(HLA)已成为电气和电子工程师协会(IEEE)标准。基于HLA所开发的仿真系统中的各成员既可能由现有的仿真系统改造而成，也可能要完全重新开发，而各种模型之间的关系必须体现在各成员的具体实现中。该文围绕基于HLA的系统建模与仿真问题从理论和实践两方面较为详细地介绍了HLA的有关概念、主要内容和基本规范，给出了基于HLA标准编写的鱼雷联邦成员仿真程序的部分代码的框架，并指出基于HLA标准编写的仿真程序是复杂大系统仿真、尤其是武器系统仿真的发展方向。该文对于学习HLA标准有一定的参考价值和指导意义。     

利用模型驱动体系架构开发分布仿真系统

作为现有分布交互仿真的标准，尽管HLA的原理非常优秀，但由于其实现上存在的一些问题，致使HLA的应用仅仅局限于军队的某些仿真领域。HLA所倡导的可重用性也受限于特定的仿真支撑平台，如果仿真平台改变，则现在基于HLA开发的仿真组件的可重用性将无法得到很好的体现。模型驱动体系架构(MDA)是对象管理组织(OMG)提出的一种先进的软件开发模式，其核心思想是将系统的行为逻辑模型与特定的目标平台分离，此模型仅需建立一次，然后可以重用于现有的或将来可能推出的不同的软件平台。将MDA技术应用到HLA将会带来诸多的好处。该文简要介绍了MDA的概念，阐述了MDA将会给仿真领域带来的巨大影响，最后给出了利用MDA开发分布仿真系统的一般步骤。     

一种基于跳表的DDM相交区域快速查询算法

HLA是为提高仿真系统的互操作性和可重用性而提出的新型分布仿真标准。HLA中数据分发管理服务的目的是通过邦员对数据公布和订购区域的表达来过滤一个邦员所接收到的数据,同时减少对网络带宽的消耗。DDM的核心是多维矩形区域动态相交查找的问题,其算法性能的好坏对DDM的效率是至关重要的。现有的一些动态区域查找算法还不能同时满足高效、精确且易于实现等要求,为此设计出一种基于跳表数据结构的用于快速相交区域查找的区问跳表,同时分析了区间跳表的构造原则以及基本操作的流程,并在此基础上提出了基于区间跳表的相交区域查找算法。该算法的匹配精度高,时间复杂度低,且具有编程实现简单的特点。     

一种混合的动态DDM实现方法

介绍了HLA中数据分发管理DDM的基本内容和过程，分析了目前两种经典的DDM实现方法；在此基础上综合了现有方法的优点，提出了一种混合的动态的DDM实现方法，提高了区域匹配的精度，降低了网络资源的消耗，对DDM方法进行了改进。     

A hybrid multicast–unicast assignment approach for data distribution management in HLA

The main focus of data distribution management (DDM) in HLA is to reduce the amount of data received by federates in large-scale distributed simulations. The use of limited multicast resources plays a key role in the performance of DDM. In order to improve the performance of DDM by using communication protocol effectively, a hybrid multicast–unicast data transmission problem and its formal definition are presented, and then a hybrid multicast–unicast assignment approach is proposed. The approach uses a new adaptive communication protocol selection (ACPS) strategy to utilize the advantages of multicast and unicast, avoid their disadvantages, and consider the inter-relationship between connections. It includes the ACPS static assignment algorithm and the ACPS dynamic assignment algorithm, according to the difference between the static connections and the dynamic connections. In our approach, a concept of distance is presented to measure the inter-relationship between connections for multicast and the message redundancy for unicast, which is the core of the two algorithms in order to gather the connections to a multicast group or to balance the use of unicast and multicast for best performance. As a result, our algorithms can more effectively decide whether a new connection should use unicast or multicast communication, and whether adjusting previous assignment result can further improve the performance. In addition, a control mechanism is introduced to deal with connection changes during the dynamic assignment. The experiment results indicate that our algorithms can utilize the multicast and unicast communication resources effectively, as well as can achieve better performance than existing methods in the real running environment.     

An Efficient Adaptive Transmission Control Scheme for Large-Scale Distributed Simulation Systems

Data distribution management (DDM) is one of the most critical component of any large-scale interactive distributed simulation systems. The aim of DDM is to reduce and control the volume of information exchanged among the simulated entities (federates) in a large-scale distributed simulation system. In order to fulfill its goal, a considerable amount of DDM messages needs to be exchanged within the simulation (federation). The question of whether each message should be sent immediately after it is generated or held until it can be grouped with other DDM messages needs to be investigated further. Our experimental results have shown that the total DDM time of a simulation varies considerably depending on which transmission strategy is used. Moreover, in the case of grouping, the DDM time depends on the size of the group. In this paper, we propose a novel DDM approach, which we refer to as Adaptive Grid-based (AGB) DDM. The AGB protocol is distinct from all existing DDM implementations, because it is able to predict the average amount of data generated in each time step of a simulation. Therefore, the AGB DDM approach controls a simulation running in the most appropriate mode to achieve a desired performance. This new DDM approach consists of two adaptive control parts: 1) the Adaptive Resource Allocation Control (ARAC) scheme and 2) the Adaptive Transmission Control (ATC) scheme. The focus of this paper is on the ATC scheme. We describe how to build a switching model to predict the average amount of DDM messages generated and how the ATC scheme uses this estimation result to optimize the overall DDM time. Our experimental results provide a clear evidence that the ATC scheme is able to achieve the best performance in DDM time when compared to all existing DDM protocols using an extensive set of experimental case studies.     

基于MOM的HLA/RTI管理盟员的设计与实现

为了在仿真运行过程中对联盟、盟员以及RTI进行监控，HLA中引入了管理对象模型(MOM)，该模型是HLA／RTI架构中的重要组成部分。该文介绍了IEEEl516规范中定义的MOM，并在此基础上对其进行了扩展。结合我们StarLink RTI的开发实践，提出了通过代理盟员实现MOM的设计方案，在该RTI中实现了对MOM的支持。最后在此基础上，设计并实现了管理盟员StarFM。     

基于位移残差的数据分发管理区域匹配及传输算法

高层体系结构(high level architecture,HLA)是建模与仿真的国际标准,它规定了数据分发管理服务(data distribution management,DDM)来减少不相关数据的发送与接收,从而减少网络带宽占用.发布区域与订购区域之间匹配计算的效率是影响数据分发管理服务质量的重要因素.区域信息的传输同样非常重要,盟员间通过区域信息的传输来保持区域的正确性和一致性,但区域信息的传输同样会给网络带来负载.现有算法通常是在区域保真度和网络负载两者之间做折中处理,难以兼顾。因此,本文充分考虑了变化区域的匹配效率以及区域传输的带宽占用问题,做出以下贡献:1)定义了区域变化与区域匹配变化之间的映射关系,采用该映射可以明显减少区域改变后所需要的匹配计算次数,从而提高了匹配效率;2)将区域更新信息划分为两种数据表达,区域快照与区域残差.通过尽量传输区域残差来代替传输完整的区域信息可以有效减少区域信息传输所消耗的网络带宽.因此,本文提出一种基于位移残差的DDM匹配与传输算法,给出了算法的理论分析与测试结果,并且对算法在实际应用中的表现进行了测试对比,给出了数据对比与结果分析.实验结果表明,基于位移残差的DDM匹配与传输算法具有良好的匹配效率,并且能够大大减少网络带宽占用,尤其是在具有大量不断变化区域的情况下.     

数据分发管理匹配算法的R-树实现

数据分发管理（DDM）是高层体系结构（HLA）接口规范的6类服务之一，高效的区域匹配算法是DDM研究的重点和难点．当前的多种匹配算法往往只适用于特定的应用环境，且效率不够理想．R-树法是在空间索引技术的基础上提出的一种新的匹配算法，该方法用R-树对DDM区域的矩形进行组织，并利用Hash索引对其叶结点的组织方式进行了改进．实验结果表明R树法可有效减少动态DDM的维护开销，提高分布交互仿真的实时性,通过调整R-树的相关参数，可以进一步改善匹配算法的性能．     

Comparing high level architecture data distribution management specifications 1.3 and 1516

The high level architecture (HLA) is a standard for federations of distributed simulations that exchange run-time data. HLA's data distribution management (DDM) services reduce data delivered to simulations based on their declarations of data produced and required. The HLA specifications, including DDM, were changed substantially from the Department of Defense 1.3 standard to the IEEE 1516 standard. The two DDM specifications' (DDM 1.3 and DDM 1516) power to define intersimulation data flows are compared. A transformation from DDM 1.3 to DDM 1516 configurations and a mapping from DDM 1516 to DDM 1.3 configurations prove that the DDM specifications are equivalently powerful.     

分布式协同虚拟实验室的设计与实现

讨论了可用于网络研究和学习的分布式协同虚拟实验室技术,提出了该技术的HLA/Java 3D构建方案.将实验系统定义为一个联邦,实验目标由联邦成员协同完成.联邦成员由4个线程组成,其中Applet线程和远程更新线程负责虚拟实验室图形渲染,联邦成员主线程和RTI回调线程实现协同控制.该系统完成了该4个线程的设计,并用队列和阻塞实例实现了线程之间的协调,解决了RTI重入问题.实验结果表明该方案是可行的.