A Framework for Trust and Reputation in Grid Environments

This paper examines the role of trust and reputation in Grid environments. As Grid technology becomes standardized and stable, business models are invented and increasingly applied, and economic implications can be observed. Asymmetrically distributed information may allow for opportunistic behavior of service providers or users who opportunistically exploit the information gap between providers and consumers on the quality of services. The paper takes up these economic issues by proposing a reputation-based conceptual framework for enabling future open Grid markets, to recommend the most promising Grid architecture and a corresponding reputation approach in a particular case.     

Network coding for unicast in a WiFi hotspot: Promises,challenges, and testbed implementation

In offices and residential buildings, WiFi networks have become a primary means for providing Internet access to wireless devices whose dominant traffic pattern is unicast. In the meantime, the emergence of network coding has brought about great promises for multicast in communication networks where intermediate nodes are allowed to process independent incoming information flows. Little is known about network coding for unicast, however. The objective of this paper is thus to depart from multicast scenarios and shed light on several possible unicast scenarios to which network coding may be applied in a WiFi hotspot in order to obtain communication benefits such as throughput gain, fairness, and reduced protocol complexity. We identify five representative scenarios in which network coding may be used to benefit unicasting in a WiFi hotspot. Several open research issues and practical challenges related to each scenario are discussed individually. To illustrate the benefits of network coding for unicast in a WiFi hotspot, we propose and implement iCORE: The interface COoperation Repeater-aided network coding Engine. iCORE is a practical system in which multi-channel multi-radio repeaters are used to relay unicast traffic for those terminals sitting far away from an access point and suffering from weak signals at a WiFi hotspot. It is based on our last scenario which illustrates the synergy among network coding, opportunistic routing, and interface management. Utilizing idle wireless interfaces and listening to traffic opportunistically, iCORE allows packets to move across the interfaces and to be coded across flows whenever it sees more transmission opportunities. We evaluate iCORE on a four-node chain-like topology testbed implemented using IEEE 802.11b/g radios and compare it to MORE – the state-of-art intra-flow network coding implementation based on opportunistic routing. Our experimental results reveal promising gains in terms of throughput over MORE.     

Cooperative car parking using vehicle-to-vehicle communication: An agent-based analysis

In this paper, we introduce a decentralized car parking approach for vast car park areas based on cooperation among vehicles through vehicle-to-vehicle communication, called Cooperative Car Parking (CoPark). In CoPark, the task of finding car parking spaces inside a large car parking area is done via smart agents in vehicles opportunistically cooperating with each other to locate parking spaces as near as possible to the final destination with reduced searching time. We comprehensively investigate a range of car parking circumstances and situations in our simulations to evaluate the proposed CoPark approach. We show that by strategic cooperation between agents in the CoPark approach, greater satisfaction can be achieved in terms of individual and social benefits, in the form of reduced search times for car park spaces and reduced walking distances from where cars are parked to a destination building.     

基于ZigBee和GSM的智能停车系统

设计了一种采用ZigBee低功耗通信技术采集和汇集车位信息、GSM实现用户交互的智能停车系统。系统主要由车位信息采集模块、信息集中处理模块以及用户终端3个部分组成。车位上的停车情况由地磁传感器的差分信息提取,用户可以通过GSM终端查询停车场的车位情况。系统可靠地完成了地磁传感器到用户终端的数据链路,实现了车位信息资源的共享,提高了车位信息的透明度,能够有效地提高城市停车的效率。     

一种基于分布式哈希表的Web服务目录系统

分析了集中式UDDI注册中心存在的缺点。结合P2P技术,基于分布式哈希表提供的高效的数据定位功能,提出了一种分布式Web服务目录系统,讨论了该系统下Web服务的发布与发现过程以及目录系统的维护。在该服务目录系统中,服务的描述信息分布在各个节点上,能够克服集中式UDDI注册中心的缺陷。     

Cooperative situation assessment in a maritime scenario

In large‐scale, complex domains such as space defense and security systems, situation assessment and decision making are evolving from centralized models to high‐level, net‐centric models. In this context, collaboration among the many actors involved in the situation assessment process is critical to achieve a prompt reaction as needed in the operational scenario. In this paper, we propose a multiagent‐based approach to situation assessment, where agents cooperate by sharing local information to reach a common and coherent assessment of situations. Specifically, we characterize situation assessment as a classification process based on OWL ontology reasoning, and we provide a protocol for cooperative multiagent situation assessment, which allows the agents to achieve coherent high‐level conclusions. We validate our approach in a real maritime surveillance scenario, where our prototype system effectively supports the user in detecting and classifying potential threats; moreover, our distributed solution performs comparably to a centralized method, while preserving independence of decision makers and dramatically reducing the amount of communication required. © 2012 Wiley Periodicals, Inc.     

User-assisted in-network caching in information-centric networking

In information-centric networking, in-network caching has the potential to improve network efficiency and content distribution performance by satisfying user requests with cached content rather than downloading the requested content from remote sources. In this respect, users who request, download, and keep the content may be able to contribute to in-network caching by sharing their downloaded content with other users in the same network domain (i.e., user-assisted in-network caching). In this paper, we examine various aspects of user-assisted in-network caching in the hopes of efficiently utilizing user resources to achieve in-network caching. Through simulations, we first show that user-assisted in-network caching has attractive features, such as self-scalable caching, a near-optimal cache hit ratio (that can be achieved when the content is fully cached by the in-network caching) based on stable caching, and performance improvements over in-network caching. We then examine the caching strategy of user-assisted in-network caching. We examine three caching strategies based on a centralized server that maintains all content availability information and informs each user of what to cache. We also examine three caching strategies based on each user’s content availability information. We first show that the caching strategy affects the distribution of upload overhead across users and the number of cache hits in each segment. One interesting observation is that, even with a small storage space (i.e., 0.1% of the content size per user), the centralized and distributed approaches improve the cache hit ratio by 50% and 45%, respectively. With an overall view of caching information, the centralized approach can achieve a higher cache hit ratio than the distributed approach. Based on this observation, we discuss a distributed approach with a larger view of caching information than the distributed approach and, through simulations, confirm that a larger view leads to a higher cache hit ratio. Another interesting observation is that the random distributed strategy yields comparable performance to more complex strategies.     

一类混合资源定位服务的优化模型

对一类用于分布式VOD系统的混合了单步k随机漫步和全局中心索引的资源定位服务,用基于Markov过程的模型来描述其中的定位过程,并引入可以描述额外信息的事件,使得其控制不但依赖于状态,而且还依赖于事件.在此基础上,给出了可以直接处理事件的策略优化方法以及状态聚集的相关问题.最后,通过实例仿真验证了所给出的模型和方法.     

Interactive middleware architecture for lifelog based context awareness

Due to the development of IT convergence, a wide variety of information is being produced and distributed rapidly in digital form. Lifelog based context awareness is a technology that provides a service automatically based on perceived situational information in ubiquitous environments. To offer customized services to users, the technology of acquiring lifelog based context information in real time is the most important consideration. We propose the interactive middleware architecture for lifelog based context awareness in distributed and ubiquitous environments. Conventional middleware to support ubiquitous environments stores and manages the situational information and service content acquired by centralized storage or a DBMS. Centralized situational information and service content management may impede the autonomy of mobile nodes and the interoperation between different middle software. The proposed method designs a system that can distribute and manage situational information in mobile nodes using mobile devices in distributed and ubiquitous environments and share the service content between interactive middleware through publication. The application system designed in this study was used in a scenario providing situational perception based mobile service and proved to be useful.     

Hybrid indoor and outdoor location services for new generation mobile terminals

In the last years, an increasing interest in location services characterized the market of mobile ubiquitous devices (smartphones, handhelds, etc.). Several technologies and solutions have been developed to determine the position of mobile devices in their operating space, each with its specific degree of precision and accuracy. In this scenario, the ideal location service should be able of tracking the mobile terminal in any place it moves to, both indoors and outdoors. However, while outdoor location services have already achieved a satisfactory degree of technological maturity and effectiveness, a really ubiquitous location service that works satisfactorily in both indoor and outdoor scenarios is not yet available. In order to cope with the above challenge, this work proposes a hybrid location approach designed to choose and switch among multiple positioning technologies supported by the mobile device and available in the surrounding environment, in a dynamic and transparent way during the user movement. It combines signal strength–based fingerprinting techniques for indoor positioning together with traditional GPS-based positioning for the outdoor localization and performs opportunistic technology switching according to a count-and-threshold mechanism. The resulting solution is able to leverage the different features of the wireless networks and of the global positioning technologies, in order to provide ubiquitous location services across indoor and outdoor scenarios, as well as to minimize power consumption of the mobile device.     

一种基于访问控制的安全Web服务发现机制

当前的Web服务发现机制大多依赖集中式的统一描述、发现和集成注册中心,但组织机构出于安全和地域的考虑,倾向于构建私有的分布式注册中心,只有注册且可信的请求者才能浏览到他们有权限访问的服务信息。该文给出Web服务发现阶段基于角色的访问控制模型RBAC4WSD,发现代理依照服务提供者指定的安全策略对请求者实施访问控制,并以跨国公司内部的文档服务为例介绍原型系统的实现。     

A token based distributed algorithm for supporting mutual exclusion in opportunistic networks

Opportunistic networks are essentially distributed networks with transient connectivity among nodes. Nodes in opportunistic networks are resource constrained, mobile and opportunistically come in contact with each other. In such a distributed network, nodes may require exclusive access to a shared object or resource. Ensuring freedom from starvation is a challenging problem in opportunistic networks due to limited pairwise connectivity and node failures. In this paper, we review mutual exclusion algorithms proposed for generic mobile ad hoc networks (MANETs) and discuss their applicability to opportunistic networks. Further, we propose a novel token based algorithm¹ and prove its correctness. Simulation results show that our algorithm is communication efficient as compared to other algorithms proposed for generic mobile ad hoc networks. We also propose a timeout based fault detection algorithm that exploits the intercontact time distributions.     

基于深度学习的高速服务区车位检测算法

本文利用卷积神经网络对高速公路服务区停车场进行场景分割与车位检测.首先,通过扩充高速公路服务区停车场数据集,利用卷积神经网络进行高速公路服务区停车场区域分割与车辆检测,并对特征提取网络进行权重共享,从而达到联合训练的目的及网络模型轻量化.进而,通过对车辆的纹理特征提取,采用金字塔特征融合的方法对小目标的识别进行强化.最后,利用高速公路服务区停车位的先验知识实时计算停车场的停车位信息.实际应用表明该方法在复杂场景下,对车位检测的准确率为94%,检测速度为每秒25帧,具有很强的泛化能力,适合用于高速公路服务区停车场车位检测.     

Distributed unequal clustering algorithm in large-scale wireless sensor networks using fuzzy logic

Clustering is a promising and popular approach to organize sensor nodes into a hierarchical structure, reduce transmitting data to the base station by aggregation methods, and prolong the network lifetime. However, a heavy traffic load may cause the sudden death of nodes due to energy resource depletion in some network regions, i.e., hot spots that lead to network service disruption. This problem is very critical, especially for data-gathering scenarios in which Cluster Heads (CHs) are responsible for collecting and forwarding sensed data to the base station. To avoid hot spot problem, the network workload must be uniformly distributed among nodes. This is achieved by rotating the CH role among all network nodes and tuning cluster size according to CH conditions. In this paper, a clustering algorithm is proposed that selects nodes with the highest remaining energy in each region as candidate CHs, among which the best nodes shall be picked as the final CHs. In addition, to mitigate the hot spot problem, this clustering algorithm employs fuzzy logic to adjust the cluster radius of CH nodes; this is based on some local information, including distance to the base station and local density. Simulation results demonstrate that, by mitigating the hot spot problem, the proposed approach achieves an improvement in terms of both network lifetime and energy conservation.     

Improving availability and performance with application-specific data replication

The emerging edge services architecture promises to improve the availability and performance of Web services by replicating servers at geographically distributed sites. A key challenge in such systems is data replication and consistency, so that edge server code can manipulate shared data without suffering the availability and performance penalties that would be incurred by accessing a traditional centralized database. This work explores using a distributed object architecture to build an edge service data replication system for an e-commerce application, the TPC-W benchmark, which simulates an online bookstore. We take advantage of application-specific semantics to design distributed objects that each manages a specific subset of shared information using simple and effective consistency models. Our experimental results show that by slightly relaxing consistency within individual distributed objects, our application realizes both high availability and excellent performance. For example, in one experiment, we find that our object-based edge server system provides five times better response time over a traditional centralized cluster architecture and a factor of nine improvement over an edge service system that distributes code but retains a centralized database.     

基于用户无感知的5G 移动性管理

5G移动通信系统将提供独立于无线技术的移动性管理,无论用户位置如何改变,都能确保业务和通信质量的 连续性。本文首先分析了5G移动通信系统在移动性管理的设计目标：低时延、低功耗、高可靠性和灵活性;其次,分析了5G移 动性管理的三个主要场景,分别是分布式移动性管理场景、集中式移动性管理场景、分布集中混合式场景;最后,对5G移动性 管理的网络控制切换和终端自动控制切换两种解决方案进行了对比分析。     

A lightweight privacy preserving SMS-based recommendation system for mobile users

In this paper, we propose a fully decentralized approach for recommending new contacts in the social network of mobile phone users. With respect to existing solutions, our approach is characterized by some distinguishing features. In particular, the application we propose does not assume any centralized coordination: It transparently collects and processes user information that is accessible in any mobile phone, such as the log of calls, the list of contacts or the inbox/outbox of short messages and exchanges it with other users. This information is used to recommend new friendships to other users. Furthermore, the information needed to perform recommendation is collected and exchanged between users in a privacy preserving way. Finally, information necessary to implement the application is exchanged transparently and opportunistically, by using the residual space in standard short messages occasionally exchanged between users. As a consequence, we do not ask users to change their habits in using SMS.     

Cooperative control through objective achievement

Cooperative control is a key issue for multirobot systems in many practical applications. In this paper, we address the problem of coordinating a set of mobile robots in the RoboCup soccer middle-size league. We show how the coordination problem that we face can be cast as a specific coalition formation problem, and we propose a distributed algorithm to efficiently solve it. Our approach is based on the distributed computation of a measure of satisfaction (called Agent Satisfaction) that each agent computes for each task. We detail how each agent computes the Agent Satisfaction by acquiring sensor perceptions through an omnidirectional vision system, extracting aggregated information from the acquired perception, and integrating such information with that communicated by the teammates. We empirically validate our approach in a simulated scenario and within RoboCup competitions. The experiments in the simulated scenario allow us to analyse the behaviour of the algorithm in different situations, while the use of the algorithm in real competitions validates the applicability of our approach to robotic platforms involved in a dynamic and complex scenario.     

An Advanced Parking Navigation System for Downtown Parking

This paper develops a novel parking navigation system for downtown parking that aims to mitigate parking competition by guiding drivers to appropriate vacant parking spaces. Given drivers’ real-time locations and their parking preferences, a two-sided matching algorithm is firstly adopted to achieve a stable driver-optimal matching, under which drivers will be assigned to their most appropriate parking spaces (if any), and have no incentive to misreport their private information (e.g., parking space preferences). Although drivers’ private information is required for the navigation system, a distributed solution procedure is applied to achieve the space assignment without disclosing such information. Lastly, simulation experiments are conducted to demonstrate the capability of the proposed navigation system on reducing driving time and the frequency of changed navigation compared with other navigation systems.