Context- and social-aware middleware for opportunistic networks

Opportunistic networks are multi-hop ad hoc networks in which nodes opportunistically exploit any pair-wise contact to share and forward content, without requiring any pre-existing Internet infrastructure. Opportunistic networks tolerate partitions, long disconnections, and topology instability in general. In this challenging environment, leveraging users’ mobility represents the most effective way to deliver content to interested users. In this paper we propose a context- and social-aware middleware that autonomically learns context and social information on the users of the network, and that uses this information in order to predict users’ future movements. In order to evaluate the proposed middleware on a realistic scenario, we have designed and implemented a context- and social-aware content sharing service, exploiting the functionality of the middleware. Both the middleware and the content sharing service have been integrated with an existing data-centric architecture (the Haggle architecture) for opportunistic networks. Finally, we have validated the proposed content sharing application on a small-scale testbed and, on a larger scale, we have investigated the advantages provided by context- and social-aware sharing strategies by means of extensive simulations. The main result of this paper is the definition and implementation of a context- and social-aware middleware able to share context information with all the interested components improving the efficiency and performances of services and protocols in opportunistic networks. With respect to content sharing strategies that do not exploit context and social information, we have obtained up to 200% improvements in terms of hit rate (probability that users receive the content they request) and 99% reduction in resource consumption in terms of traffic generated on the network.     

A social-aware routing protocol for opportunistic networks

Understanding nodes mobility is of fundamental importance for data delivery in opportunistic and intermittently connected networks referred to as Delay Tolerant Networks (DTNs). The analysis of such mobility patterns and the understanding of how mobile nodes interact play a critical role when designing new routing protocols for DTNs. The Cultural Greedy Ant (CGrAnt) protocol is a hybrid Swarm Intelligence-based approach designed to address the routing problem in such dynamic and complex environment. CGrAnt is based on: (1) Cultural Algorithms (CA) and Ant Colony Optimization (ACO) and (2) operational metrics that characterize the opportunistic social connectivity between wireless users. The most promising message forwarders are selected via a greedy transition rule based mainly on local information captured from the DTN environment. Whenever global information is available, it can also be used to support decisions. We compare the performance of CGrAnt with Epidemic, PROPHET, and dLife protocols in two different mobility scenarios under varying networking parameters. Results obtained by the ONE simulator show that CGrAnt achieves a higher message delivery and lower message redundancy than the three protocols in both scenarios. The only exception is in one of the scenarios, when messages have a time to live lower than 900 min, where CGrAnt delivers a bit less messages than dLife, although with a lower message redundancy.     

高性能的机会网络数据转发机制—EH-EC

针对H-EC数据转发机制所存在的系统漏洞问题,提出了一种有效解决系统漏洞的方法,同时提出了一种对数据块进行有效划分的方法。在此基础上,设计并实现了一种新的数据转发机制——增强混合擦除编码机制（EH-EC）。在OMNET++下的仿真结果表明：EH-EC时延更少,转发成功率更高,但是相对H-EC会增加少量的路由信息冗余。     

Interest spaces: A unified interest-based dissemination framework for opportunistic networks

Embedded ubiquitous computing systems (EUCS) promise to grow remarkably in the near future. For such systems, new communication technologies are constructed to cope with the increasing functional and temporal demans. Because of the ubiquitousness of mobile devices nowadays, for example, traditional publish/subscribe is no longer an adequate model for data dissemination in mobile networks. Since any node can publish content at any time, the network can get congested easily, so a dissemination paradigm where mobile nodes contribute with a fraction of their resources is needed, through the use of opportunistic networks. Furthermore, a suitable organization for data dissemination in mobile networks should be centered around interests. Thus, we propose a unified interest-based dissemination framework for opportunistic networks entitled Interest Spaces, which simplifies dissemination by just allowing applications to mark data items with certain tags, letting the framework handle the caching, routing, forwarding, and disseminating. Similarly, applications that need to subscribe to channels simply have to specify the tags they are interested in, and the framework does the rest. However, the Interest Spaces framework also allows applications to have more control over the dissemination process if they wish, by specifying various criteria and dissemination rules. In this article, we present the architecture and components of Interest Spaces. We focus on data aggregation at the context layer, showing through simulations the benefits it brings in opportunistic dissemination. We also present a real-life use case for Interest Spaces through Chatty, an opportunistic chat application.     

机会网络数据收集中的转发控制

针对机会网络中由于节点移动、网络稀疏等各种原因通常导致网络拓扑动态变化大,消息源节点到汇聚节点之间往往不存在稳定的端到端的通信链路,提出了一种基于偏好顺序决策法(the technique for order preference by similarity to ideal so-lution,TOPSIS)的数据收集策略(data gathering based on the TOPSIS,DGT)。DGT策略根据节点的剩余能量、感知节点到汇聚节点的距离以及传感器节点的连通变化,采用TOPSIS评估选择下一跳中继节点。仿真实验表明,与现有的几种典型转发控制机制相比,DGT策略在保证较低传输延迟和较高传输成功率的基础上,通过减少节点间的转发次数,降低了网络传输开销。     

机会网络舆情传播的MCA模型及仿真研究

为了研究舆情主体的流动性和记忆能力对舆情在机会网络中传播的影响,提出移动实体、元胞容量和元胞吸引力新概念,扩展经典元胞自动机模型,并结合现代心理学的记忆理论,建立移动元胞自动机舆情传播模型。在此基础上,考虑舆情主体对新鲜观点存在抵触情绪,提出了舆情主体情感态度倾向性和态度转变阈值的概念,制定实体状态转换规则和移动规则,从而分析影响舆情在机会网络中传播的主要因素。结果表明:舆情主体流动性的提高、记忆时间阈值的增大可以促进舆情传播;不同情感态度的主体比例相差越大,舆情同质化率就越高;舆情主体的空间密度越高,舆情传播速度越快;舆情主体自身情感态度倾向性越大,舆情传播速度越慢。     

Trust and reputation management for opportunistic dissemination

Nodes in opportunistic networks need to cooperate to disseminate data. However, employing intermediate nodes for dissemination leads to several security issues. Here, we propose an opportunistic trust and reputation mechanism entitled SAROS, which detects and avoids malicious nodes, i.e. nodes which, upon receiving messages for other interested peers, modify their content in order to spread false information. This can negatively affect the network, by polluting it with spam messages, or dropping messages of interest to the nodes in the network. By detecting and avoiding malicious nodes, SAROS is able to increase the percentage of correct messages that reach their destinations.     

Association management for data dissemination over wireless mesh networks

To enable multimedia broadcasting services in mesh networks, it is critical to optimize the broadcast traffic load. Traditionally, users associate with access points (APs) with the strongest signal strength. We explore the concept of dual-association, where the AP for unicast traffic and the AP for broadcast traffic are independently chosen by exploiting overlapping coverages that are typical in mesh networks. The goal of our proposed solution is to optimize the overall network load by exploiting the flexibility provided by independent selection of unicast and broadcast APs. We propose a novel cost metric based on ETT (Expected Transmission Time) and the number of nodes in range of the APs, that are advertised in the beacons from the APs. Users periodically scan and associate with the AP which has the lowest cost metric. The proposed approach reduces the number of APs that handle the broadcast traffic resulting in a heavy reduction in control and data packet overhead. This leads to higher packet delivery rate and enhanced video quality measured in terms of PSNR. Our approach allows the freed up resources at APs to increase the unicast throughput. We compare the performance of our approach with traditional signal strength based association using extensive simulations and real experiments on an indoor testbed of 180 IEEE 802.11b based devices.     

Real-time data dissemination in mobile peer-to-peer networks

Mobile peer-to-peer networks have found many uses such as streaming of audio and video data. There are circumstances, such as emergency situations and disaster recovery, when real-time delivery is a fundamental requirement. The problem is challenging due to the limited network capacity, the variable transmission rates and the unpredictability with respect to the network conditions in the mobile peer-to-peer network.In this paper we address the problem of real-time data dissemination of multimedia streams in mobile peer-to-peer networks. Four routing algorithms are proposed based on a packet's deadline, priority or a combination of these metrics. They are simulated under different setups in a mobile peer-to-peer network with Bluetooth connectivity and nodes broadcasting audio and video streams using different priorities. We compare the performance of the algorithms using a number of metrics. Detailed experimental results are presented. Based on these results, propositions on the usage of the algorithms and the design of network requirements are presented.     

Strengthen nodal cooperation for data dissemination in mobile social networks

Data dissemination is a challenging issue in mobile social networks. It aims at increasing the overall delivery ratio and reducing the overall delivery delay. Most of the existing works assume all the users in a network are cooperative, i.e., the users are willing to carry the messages that they are not interested in while the nodes they meet maybe. In reality, the behaviors of each individual are naturally selfish, especially when the resources they have and they can access are limited. A data dissemination protocol cannot be pragmatic unless the selfishness is considered. This work proposes an incentive scheme to stimulate the users in a network to be more cooperative. Credits are the stimulus to encourage users to be more cooperative for data dissemination. We evaluate each node’s ability to fetch messages of a specific kind of interest and every single user can rent other nodes to help with obtaining the interested messages by paying credits. Extensive simulations on real traces are carried out to evaluate the proposed incentive scheme.     

Nature-inspired algorithm-based secure data dissemination framework for smart city networks

Neural Computing and Applications - Unceasing population growth and urbanization have intensified the traditional systems to deal with citizen lifestyle, environment, economic issues and good...     

机会网络中基于定向数据传输的地理路由算法

机会网络基于方向的地理路由(DIG)算法存在数据分组传输时延偏大以及成功率偏低的问题,这是由于DIG算法使数据在缓存中的等待时间过长且不能有效保证携带数据的节点向目的节点方向移动,针对该问题,提出了基于定向数据传输的地理路由(GRDDT)算法。该算法采用了一种新的数据转发机制并且更加有效地利用邻居表信息,有效避免了以上情形的出现,从而达到降低数据分组传输时延并提高成功率的目的。OPNET仿真实验结表明,与DIG算法相比,GRDDT算法在传输时延和数据传输成功率等方面的性能均得到提高。     

机会网络中的邻居发现性能优化方法分析

由于机会网络的节点移动性、能量有限性和网络稀疏性等,数据传输困难,选择一种可靠高效的邻居发现方法非常重要。现有的算法未能达到预期的性能优化效果,如主动探测方法是通过节点广播探测包来发现邻居节点,会消耗大量能量;被动侦听方法则是通过不断地侦听信道解析数据帧以得到邻居节点的信息,却无法准确侦听到所有邻居。文中分析了一种结合主动探测和被动侦听的邻居发现方案,并与现有方法作比较,通过仿真验证其对于邻居发现性能的优化效果。实验结果表明,此方法虽未能在丢包率、吞吐量和端到端时延等性能上体现出优势,但邻居发现数目提高约20%,并且提高了邻居探测过程中的能量有效性,能量最高节约了60%。     

An adaptive multimedia streaming dissemination system for vehicular networks

An adaptive seamless streaming dissemination system for vehicular networks is presented in this work. An adaptive streaming system is established at each local server to prefetch and buffer stream data. The adaptive streaming system computes the parts of prefetched stream data for each user and stores them temporarily at the local server, based on current situation of the users and the environments where they are located. Thus, users can download the prefetched stream data from the local servers instead of from the Internet directly, meaning that the video playing problem caused by network congestion can be avoided. Several techniques such as stream data prefetching, stream data forwarding, and adaptive dynamic decoding were utilized for enhancing the adaptability of different users and environments and achieving the best transmission efficiency. Fuzzy logic inference systems are utilized to determine if a roadside base station or a vehicle can be chosen to transfer stream data for users. Considering the uneven deployment of BSs and vehicles, a bandwidth reservation mechanism for premium users was proposed to ensure the QoS of the stream data premium users received. A series of simulations were conducted, with the experimental results verifying the effectiveness and feasibility of the proposed work.     

下一代电信网络性能监控系统设计

为了主动发现和跟踪解决电信网络服务质量问题,支持网络管理业务的平滑过渡,提出面向性能问题生命周期管理构建性能监控系统。参考下一代运营操作系统和软件,构建了端到端的性能问题生命周期管理流程和性能监控共享信息数据模型,设计了以组件为基础的系统结构。在运营商网络管理系统的基础上对系统进行实现和集成应用,应用表明,性能监控系统能有效支撑对性能问题的发现、分析和解决效果评估,并支持灵活的系统集成和持续的业务演进。     

机会网络路由协议

在机会网络中由于网络稀疏、节点移动和通信范围等因素的影响,有可能出现网络分裂或节点脱网,源节点和目的节点之间不一定存在完整的端到端路径,这为路由协议的设计带来巨大挑战,此问题近年来引起了研究人员越来越多的关注。首先介绍了机会网络的基本概念、体系结构和特点等;然后阐述了机会网络路由协议研究的进展,概括了机会网络路由协议中的新机制,对现有路由协议进行分类并详述它们的基本原理;通过比较对各种协议的特点进行分析阐述,最后给出未来研究的方向。     

适用于大规模无线传感器网的流量优化系统设计

针对大规模无线传感器网络(WSN)流量随访问者数量增加而上升的问题,设计并实现了一种适用于构建大型WSN并降低系统流量的应用系统框架。系统采用IPv6和低功耗无线个域网的IPv6技术(6LoWPAN)搭建大规模WSN,使用消息队列遥测传输(MQTT)协议和针对WSN设计的消息队列遥测传输(MQTT-SN)协议在应用层搭建了连接WSN和传统互联网的发布/订阅结构。实验结果显示,当系统中存在5个传感器节点时,与受限应用协议(CoAP)构建的WSN应用系统相比,提出的系统框架的数据流量仅为前者的18%左右。这表明该系统框架可有效地控制访问者增加对WSN流量造成的影响。     

Influence of mobility models on the performance of data dissemination and routing in wireless mobile ad hoc networks

Many routing protocols are proposed in the literature on mobile ad hoc networks (MANETs). Some of those protocols which have been investigated under different assumptions are unable to capture the actual characteristics of MANETs. Therefore, there is a necessity to investigate the performance of MANETs under a number of different protocols with various mobility models. This paper evaluates the performance of the single path routing protocols (AODV, DSR, and DSDV), in the presence of different network loads and differing mobility models. Our findings show that DSR routing protocol has a better performance compared to other protocols with respect to various metrics.     

Design and performance evaluation of a novel robotic catheter system for vascular interventional surgery

Vascular interventional surgery (VIS) is an effective treatment method for vascular diseases. However, there are many problems in traditional VIS, such as surgeons are radiated by X-ray, the lack of well skilled surgeons, the security of the surgery will be reduced due to the Surgeons’ fatigue, high risk of the surgery. To solve these problems, a robotic catheter system is needed to protect the surgeons and enhance the safety of the surgery. In this paper, a novel robotic catheter system with master–slave structure for VIS has been developed. This system is designed with the consideration of the operation method in traditional VIS, which allows the surgeon to operate a real catheter on the master side, then the surgeon make full use of the natural catheter manipulation experience and skills obtained in conventional catheter operation. The salve manipulator operates the catheter insert into the blood vessel with following the operation of the surgeon, and the operating force of the salve manipulator is detected. On the master side, a novel damper-based magnetorheological (MR) fluid is designed to realize the force feedback, which is also used to reappear the operation force from the salve manipulator. The damper connected directly with real catheter is a piston structure using the MR fluid to realize the force feedback. It can transmit the feedback force to surgeon’s hand through the operating catheter connected with damper, which seems that the surgeon operates the catheter beside the patient. The operating transparency of the developed system has been enhanced. The mechanism of the developed system has been introduced in detail. Performance evaluation experiments for the developed robotic catheter system have been done. The experimental results indicated that the developed robotic catheter system is fit for VIS.