HLA中基于Agent的层次过滤机制

数据分发管理是HLA接口规范中定义的六大服务之一。为解决仿真应用中网络带宽、处理资源受限和提高系统可扩缩性提供了可能。文章介绍了HLA中数据分发管理DDM的基本内容；研究分析了最新发展的基于移动Agent的实现方法，提出了基于Agent的层次过滤机制对其进行了改进，解决了仿真结点计算能力受限的问题。     

基于Agent的数据仓库的研究

结合可移动的软件Agent技术,提出了基于Agent的数据仓库。它的提出使得用户可以更加有效地管理分布的、异构的集成环境。着重讨论了基于Agent的数据仓库的体系结构,并在此基础上讨论了一些实现中的问题。     

传感器网络中基于移动代理的数据融合方法研究

在传感器网络中采用移动代理来进行数据融合是一个新颖的思路,它与传统的数据融合方法相比拥有诸多优势,有必要为数据融合设计一种基于移动代理的计算模型,使得移动代理在传感节点间迁移的同时能够进行有效的数据融合.我们对基于移动代理的数据融合方法进行了深入的探索,设计了基于移动代理的数据融合框架,提出了一种与移动代理路由紧密结合的按分辨率并行量化交叠的数据融合算法--PQOR,并将其成功地运用到目标分类识别的应用场景中.仿真结果表明:与传统的数据融合算法相比,PQOR能够以较小的代价达到应用的要求,其优势随着网络节点规模的增长更为明显.     

基于策略和代理的无线传感器网络数据管理架构

为方便用户对无线传感器网络中的数据进行有效管理,并进一步减少网络中的数据流量,对无线传感器网络数据管理的现状进行了分析和研究,提出了一种基于策略技术和代理的数据管理体系结构。该架构结合了策略技术和代理技术,进行了优势互补,用移动代理把用户的策略信息传到各个节点。策略技术的使用可以减少移动代理的代码的大小,在每个节点上都由策略代理来执行策略信息。     

A bandwidth and effective hit optimal cache scheme for wireless data access networks with client injected updates

In this paper, we propose an optimal cache replacement policy for data access applications in wireless networks where data updates are injected from all the clients. The goal of the policy is to increase effective hits in the client caches and in turn, make efficient use of the network bandwidth in wireless environment. To serve the applications with the most updated data, we also propose two enhanced cache access policies making copies of data objects strongly consistent. We analytically prove that a cache system, with a combination of our cache access and replacement policy, guarantees the optimal number of effective cache hits and optimal cost (in terms of network bandwidth) per data object access. Results from both analysis and extensive simulations demonstrate that the proposed policies outperform the popular Least Frequently Used (LFU) scheme in terms of both effective hits and bandwidth consumption. Our flexible system model makes the proposed policies equally applicable to applications for the existing 3G, as well as upcoming LTE, LTE Advanced and WiMAX wireless data access networks.     

一种基于MA的无线传感器网络IDS模型研究

本文针对分簇式无线传感器网络的特点,将入侵检测技术与移动Agent技术相结合,提出一种基于MA的无线传感器网络入侵检测方案,采用多个Agent模块分布协作,运用一种基于聚类的入侵检测算法,从而达到提高无线传感器网络的安全性、可靠性,降低入侵检测能量消耗的目的。     

A Framework for Cache Management for Mobile Databases: Design and Evaluation

In a mobile computing environment, database servers disseminate information to multiple mobile clients via wireless channels. Due to the low bandwidth and low reliability of wireless channels, it is important for a mobile client to cache its frequently accessed database items into its local storage. This improves performance of database queries and improves availability of database items for query processing during disconnection. In this paper, we investigate issues on caching granularity, coherence strategy, and replacement policy of caching mechanisms for a mobile environment utilizing point-to-point communication paradigm.We first illustrate that page-based caching is not suitable in the mobile context due to the lack of locality among database items. We propose three different levels of caching granularity: attribute caching, object caching, and hybrid caching, a hybrid approach of attribute and object caching. Next, we show that existing coherence strategies are inappropriate due to frequent disconnection in a mobile environment, and propose a cache coherence strategy, based on the update patterns of database items. Via a detail simulation model, we examine the performance of various levels of caching granularity with our cache coherence strategy. We observe, in general, that hybrid caching could achieve a better performance. Finally, we propose several cache replacement policies that can adapt to the access patterns of database items. For each given caching granularity, we discover that our replacement policies outperform conventional ones in most situations.     

银河高性能分布仿真系统的设计和实现

面向新一代的分布交互仿真应用,设计并实现了一个基于ＨＬＡ／ＲＴＩ的系统－银河高性能分布仿真系统,该系统的高性能,先进性和创造性表现在,基于ＨＬＡ／ＲＴＩ的分布交互仿真软,硬件平台,基于数据过滤／组播的数据分发管理策略,物理和逻辑相结合的多种时间管理方法,基于ＭＰＰ机传输技术的多机系统强实时互连机制,多agent虚拟环境的多媒体表现技术,它可适用于强实时高性能单／多系统仿真,弱实时多系统综合仿真。     

A resource-awareness information extraction architecture on mobile grid environment

With the advances in mobile grid technology, it is possible to store ever greater amounts of information in the mobile data grid environment. The issues of information retrieval and knowledge discovery from wireless or mobile grids are becoming increasingly important. In this paper, we use mobile agent technology to propose the RAKER, a resource-aware information extraction architecture on the mobile grid. The RAKER can dynamically determine processing and policies for information extraction, employing our proposed resource estimation model to achieve high levels of performance and availability. With it, mobile users can extract information or knowledge stored on mobile grids in an efficient, effective and transparent way without worrying about the most important issue in mobile computing, which is energy consumption. We show the implementation with an example to demonstrate the use of RAKER. In addition, we display its performance by measuring latency and energy consumption and simulating the availability of the system.     

Performance evaluation of an optimal cache replacement policy for wireless data dissemination

Data caching at mobile clients is an important technique for improving the performance of wireless data dissemination systems. However, variable data sizes, data updates, limited client resources, and frequent client disconnections make cache management a challenge. We propose a gain-based cache replacement policy, Min-SAUD, for wireless data dissemination when cache consistency must be enforced before a cached item is used. Min-SAUD considers several factors that affect cache performance, namely, access probability, update frequency, data size, retrieval delay, and cache validation cost. The paper employs stretch as the major performance metric since it accounts for the data service time and, thus, is fair when items have different sizes. We prove that Min-SAUD achieves optimal stretch under some standard assumptions. Moreover, a series of simulation experiments have been conducted to thoroughly evaluate the performance of Min-SAUD under various system configurations. The simulation results show that, in most cases, the Min-SAUD replacement policy substantially outperforms two existing policies, namely, LRU and SAIU.     

基于移动Agent的无线应用软件测试系统

介绍了基于移动Agent技术实现的用于测试与网络相关的无线应用软件的测试系统,并提出了将系统的弱移动机制改造成为强移动的新思路用以提高测试环境的真实性。利用了对源程序插入代码来捕捉和恢复程序状态的方法,加入的代码在程序需要捕捉状态时捕捉到程序状态信息并在重新运行时恢复状态。实现了在不修改Java虚拟机的情况下基于Java的移动Agent强迁移。     

普适计算中的服务访问控制模型

随着无线移动终端的迅速发展和广泛使用,结合移动Agent的优势,本文提出了一个基于移动Agent在固定设备和移动设备组成的普适计算混合环境中提供服务访问控制的模型。该模型主要包括基于Jess推理机的逻辑规则控制引擎,用户隐私信息存储层,供点对点Agent使用的查询接口和获得更多外部资源的服务接口。最后通过一个约会订餐的场景来对本模型进行分析。     

Energy saving strategies for cooperative cache replacement in mobile ad hoc networks

Data caching on mobile clients is widely seen as an effective solution to improve system performance. In particular, cooperative caching, based on the idea of sharing and coordination of cache data among multiple users, can be particularly effective for information access in mobile ad hoc networks where mobile clients are moving frequently and network topology is changing dynamically. Most existing cache strategies perform replacement independently, and they seldom consider coordinated replacement and energy saving issues in the context of a mobile ad hoc network. In this paper, we analyse the impact of energy on designing a cache replacement policy and formulate the Energy-efficient COordinated cache Replacement Problem (ECORP) as a 0-1 knapsack problem. A dynamic programming algorithm called ECORP-DP and a heuristic algorithm called ECORP-Greedy are presented to solve the problem. Simulations, using both synthetic workload traces and real workload traces in our experiments, show that the proposed policies can significantly reduce energy consumption and access latency when compared to other replacement policies.     

可移动的虚拟桌面:无线云终端

无线云终端的手段之一可以使手机用户获取运行在机房服务器的手机虚机的桌面。由于手机品牌繁多,这一手段促进了移动终端的中央管理。介绍此技术的方法,包括手机虚机的基础平台和管理软件。测试结果显示:大批量的用户可以经过3G无线传输使用Android和WinMobile的桌面。在未来,移动终端还有潜力同时获取虚拟桌面、视频,以及传输物联网应用的传感信息,并使用机房里小巧的手机虚机及物理服务器的能力。     

Agent scheduling model for adaptive dynamic load balancing in agent-based distributed simulations

Agent-based distributed simulations are confronted with load imbalance problem, which significantly affects simulation performance. Dynamic load balancing can be effective in decreasing simulation execution time and improving simulation performance. The characteristics of multi-agent systems and time synchronization mechanisms make the traditional dynamic load balancing approaches not suitable for dynamic load balancing in agent-based distributed simulations. In this paper, an adaptive dynamic load balancing model in agent-based distributed simulations is proposed. Due to the complexity and huge time consuming for solving the model, a distributed approximate optimized scheduling algorithm with partial information (DAOSAPI) is proposed. It integrates the distributed mode, approximate optimization and agent set scheduling approach. Finally, experiments are conducted to verify the efficiency of the proposed algorithm and the simulation performance under dynamic agent scheduling. The experiments indicate that DAOSPI has the advantage of short execution time in large-scale agent scheduling, and the distributed simulation performance under this dynamic agent scheduling outperforms that under static random agent distribution.     

Call admission control policies in cellular wireless networks with spectrum renting

Radio spectrum is scarce and precious resource in wireless networks. To efficiently utilize radio spectrum, a wireless network can rent radio channels from another wireless network and returns back the rented channels when the rented channels are required to be withdrawn. The rental and withdrawal of radio channels result in two phenomena: (i) variable number of radio channels in a wireless network and (ii) call dropping due to the channel withdrawal. Call admission control aims to provide good quality-of-services for mobile users while efficiently utilize radio channels. Many call admission control policies in the previous literatures were studied without the two phenomena. In this paper, we study three call admission control policies, namely, fixed-reservation policy, single-threshold policy and multiple-threshold policy in a wireless network which rents channels from another wireless network. We develop numerical analyses to analyze and compare the performances of the three call admission control policies. Numerical results show that the multiple-threshold policy produces higher throughput than the single-threshold and fixed-reservation policies under the same constraint of quality-of-services.     

Adaptation of agent-based non-repudiation protocol to mobile digital right management (DRM)

Non-repudiation of a mobile digital rights management (DRM) ensures that when a user (U) sends some message to a rights issuer (RI), neither U nor RI can deny having participated in this transaction. An evidence of a transaction is generated by wireless PKI mechanism such that U and RI cannot repudiate sending and receiving the message respectively. U generates a mobile agent which carries encrypted payment information to RI. This mobile agent is also issued a proxy certificate by U; this certificate guarantees the binding relationship between them. One trusted third party acts as a lightweight notary for evidence generation. One advantage of this agent-based non-repudiation protocol is to reduce inconvenience for mobile clients such as connection time; it causes difficulty for fair transaction for mobile DRM.     

An agent-based metric for quality of services over wireless networks

In a wireless LAN environment, clients tend to associate with the nearest access point (AP) which usually provides the strongest signal. However, this does not guarantee that users will receive the best quality of service (QoS) if the population sharing the network capacity were not considered. In other words, within the same access point, the more the population is, the less bandwidth each user will share, and the worse the quality of service will be. In this paper, we proposed an anticipative agent assistance (AAA) which is an agent-based metric for evaluating and managing the resource information of the wireless access points, computing the potential AP list, and providing clients with resource information of APs. We also propose a novel QoS feedback mechanism which allows users to promptly adjust the service quality with AAA according to the throughput and delay requirements. We evaluate the performance of our proposed method using the ns-2 simulator. Numerical results show that AAA achieves: (1) reduce the transmission delay, (2) increase the throughput, (3) improve the network utilization, (4) accommodate more users to access the networks, and (5) achieve load-balancing. Our metric is implementation feasible in various IEEE WLAN environments.     

移动实时事务预留广播空间的验证协议

在无线数据广播环境中,从移动客户机到服务器的上行带宽非常有限,传统的并发控制协议不适合这种不对称通信环境.本文提出一种可变乐观并发控制协议,服务器周期性向移动客户机广播数据对象,同时把一个广播周期分成若干个子周期,在两个连续的子周期间,一个保留空间被预留来存放服务器更新事务在第一个子周期开始后修改的所有数据对象,移动只读事务通过比较服务器更新事务提交的写集合和自己读集合来自主进行一致性验证,如果只读事务不能通过部分验证,它不会被草率地夭折并重新启动,相反,应用一个改进的向前验证策略,帮助移动只读事务争取更多提交机会.最后,本文进行充分的实验对提出的算法性能进行了评价.     

VeSense: High-performance and energy-efficient vehicular sensing platform

Although vehicular sensing where mobile users in vehicles continuously gather, process, and share location-sensitive and context-sensitive sensor data (e.g., street images, road condition, traffic flow) is emerging, little effort has been investigated in a model-based energy-efficient network paradigm of sensor information sharing in vehicular environments. Upon these optimization frameworks, a suite of optimization subproblems: a program partitioning and network resource allocation problem, we propose a distributed vehicular sensing platform, called VeSense where mobile users in vehicles publish/access sensor data via a cloud computing-based distributed P2P overlay network. The key objective is to satisfy the vehicular sensing application’s quality of service requirements by modeling each subsystem: mobile clients, wireless network medium, and distributed cloud services. By simulations based on experimental data, we present the proposed system can achieve up to 37 times more energy-efficient and 73 times faster compared to a standalone mobile application, in various vehicular sensing scenarios applying a realistic mobility model.