Location tracking using quorums in mobile ad hoc networks

We explore applications of quorum systems to the problem of tracking locations of mobile users in mobile ad hoc networks (MANETs). The location tracking system uses biquorum systems, a generalization of traditional quorum systems. We performed extensive simulations of the location tracking system. The simulation results show that our strict biquorum implementation has better performance than the traditional strict quorum implementations. Moreover, our results show that randomized dynamic quorum implementations have better overall performance than strict (bi)quorum implementations.     

基于图着色的无线自组网极小连通支配集算法

基于连通支配集算法的虚拟主干网技术对于无线自组网的路由优化、能量保护和资源分配都具有重要的作用。通过引入极大独立集和极小支配集概念,基于图着色思想提出一种新的适合于无线自组网的极小连通支配集算法,从理论上证明了该算法的正确性和高效性,也通过仿真实验分析了该算法在多种情况下的实际性能,仿真结果表明新算法在簇头和主干节点数目方面具有较好的性能,特别在节点密集的网络环境中更加突出。     

An efficient anycast scheme for discovering k services in cluster‐based mobile ad hoc networks

Anycast is a one‐to‐any bidirectional transmission scheme that can be used to provide various service‐oriented applications. However, traditional anycast cannot support some distributed applications that need to locate multiple servers such as network time protocols and threshold cryptography. Although there are some extended anycast schemes that can support the discovery of k services, they may cause high control overhead, low satisfaction ratio, or high searching latency when there are more service requesters and providers. The main reasons for these shortcomings are unknown service information and limited hierarchical structure. This work proposes an efficient anycast scheme, called AnyKast, for discovering k services in cluster‐based mobile ad hoc networks. In the AnyKast scheme, an anycast tree based on the clustering and virtual backbone is established to reduce unnecessary message transmission. In the anycast tree, anycast clusterheads disseminate their information to certain specific nodes that take the service information and perform the service selection task instead of blindly searching. Furthermore, to decrease the cost of service information collection and maintenance, scope flooding is used to limit the information transmission, and information piggybacking and periodical inquiry mechanism are used to increase the service information accuracy. The experimental results demonstrate that our scheme can effectively discover services, reduce request and reply message control overhead, and lower the searching latency. Copyright © 2010 John Wiley & Sons, Ltd.     

移动分布式无线网络中具有QoS保证的UPMA协议

该文基于有效竞争预约接入、无冲突轮询传输的思想提出了支持节点移动性、多跳网络结构和服务质量(QoS)的依据用户妥善安排的多址接入(UPMA)协议。它大大提高了信道的使用效率,保证了发送节点能快速接入信道,同时,最大程度地保证所有实时业务的时延和带宽要求。最后,我们考察了它对Internet数据业务的支持性能。     

The rise and fall of spatio-temporal clusters in mobile ad hoc networks

Cluster detection has been widely applied to the problem of efficient data delivery in highly dynamic mobile ad hoc networks. By grouping participants who meet most often into clusters, hierarchical structures in the network are formed which can be used to efficiently transfer data between the participants. However, data delivery algorithms which rely on clusters can be inefficient in some situations. In the case of dynamic networks formed by encounters between humans, sometimes called Pocket Switched Networks (PSNs), cluster based data delivery methods may see a drop in efficiency if obsolete cluster membership persists despite changes to behavioural patterns. Our work aims to improve the relevance of clusters to particular time frames, and thus improve the performance of cluster based data delivery algorithms in PSNs. Furthermore, we will show that by detecting spatio-temporal clusters in PSNs, we can now improve on the data delivery success rates and efficiency of data delivery algorithms which do not use clustering; something which has been difficult to demonstrate in the past.     

一种高效的无线自组网全网可靠广播协议

现有大部分的无线自组网广播协议采用最小虚拟骨干子网进行全网广播,能最小化广播的总发送次数。但是,由于未考虑无线链路的不可靠性,这些协议在实际网络中的广播效率并不高。为此,提出了一种高效的全网可靠广播协议（ENWRB）,该协议采用网络编码技术减少单跳广播的重传次数,并通过一种基于链路感知的虚拟骨干网选择算法产生更高效的广播骨干网。仿真结果表明,在确保所有节点成功接收广播消息的相同前提下,ENWRB协议的效率显著高于HCA(Hierarchical CDS-based Algorithm)协议。     

A new distributed approximation algorithm for constructing minimum connected dominating set in wireless ad hoc networks

In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd.     

Secure routing in mobile wireless ad hoc networks

We discuss several well known contemporary protocols aimed at securing routing in mobile wireless ad hoc networks. We analyze each of these protocols against requirements of ad hoc routing and in some cases identify fallibilities and make recommendations to overcome these problems so as to improve the overall efficacy of these protocols in securing ad hoc routing, without adding any significant computational or communication overhead.     

Self-regulating network utilization in mobile ad hoc wireless networks

In mobile ad hoc wireless LANs, it is very difficult to maintain a targeted network utilization due to the time-varying nature of the contention-based medium access control protocol and the lack of a central control. Furthermore, previous research has been mainly focusing on the aspect of optimizing the performance at each station. But doing so may result in a very low overall network utilization. Therefore, self-regulating network utilization is very important to provide quality-of-service (QoS) in mobile ad hoc wireless networks. Through self-disciplining its own behaviors locally, each station will optimize its protocol parameters to meet the targeted overall network utilization, which is very important for QoS provisioning to multimedia services. This paper proposes and evaluates a fully distributed scheme for each station to self-regulate its behaviors through adapting the local protocol parameters to meet the targeted overall network utilization with the changes in the network environment such as the number of stations and channel quality.     

Accountability for wireless LANs, ad hoc networks, and wireless mesh networks [security in mobile ad hoc]

Accountability is an extremely important issue in computer and network systems. One of the goals of accountability is the capability to trace an event (e.g., the leaking of secure information or an outside attack), even after the event occurred so that the causes can be determined. This article first provides a survey of accountability with a general overview of the topic, using electronic patient records and various computer and network attacks as a model. Then, it describes and analyzes practical framework applications of accountability systems. An insurable network architecture, called A-NET is proposed. Then, an algorithm to achieve true accountable administration is proposed, namely, that an administrator's activities must be accountable. Finally, accountability for wireless LANs, ad hoc networks, and wireless mesh networks are studied.     

Predicting group partitions in mobile ad hoc networks

Group mobility is prevalent in many mobile ad hoc network applications such as disaster recovery, military actions, etc., and group partitions are unavoidable in such kinds of dynamic networks. Group partition may occur when mobile nodes move in diverse mobility patterns and causes the network to be partitioned into disconnected components. It may result in severe link disconnections, which then interrupt intergroup communications. By examining the group mobility pattern, we can predict the possibility of network partitions, and thus minimize the amount of communication disruptions. In this paper, we introduce a system for predicting potential group partitions in mobile ad hoc networks. On the basis of historical group mobility information, a quadratic regression model is formulated to predict the direction and speed of a group's movement. A group's micromovement is ignored and is replaced by significant linear displacement to measure its mobility to improve the prediction accuracy. We also discuss the notion of safe distance between adjacent groups, based on which the time duration before the occurrence of group partitioning can be measured. Experimental results show that our proposed prediction method demonstrates its effectiveness and efficiency in group partition predictions such that remedial actions can be taken in advance to avoid network disconnection. Copyright © 2011 John Wiley & Sons, Ltd.     

Location-aware resource management in mobile ad hoc networks

We propose an innovative resource management scheme for TDMA based mobile ad hoc networks. Since communications between some important nodes in the network are more critical, they should be accepted by the network with high priority in terms of network resource usage and quality of service (QoS) support. In this scheme, we design a location-aware bandwidth pre-reservation mechanism, which takes advantage of each mobile node’s geographic location information to pre-reserve bandwidth for such high priority connections and thus greatly reduces potential scheduling conflicts for transmissions. In addition, an end-to-end bandwidth calculation and reservation algorithm is proposed to make use of the pre-reserved bandwidth. In this way, time slot collisions among different connections and in adjacent wireless links along a connection can be reduced so that more high priority connections can be accepted into the network without seriously hurting admissions of other connections. The salient feature of our scheme is the collaboration between the routing and MAC layer that results in the more efficient spatial reuse of limited resources, which demonstrates how cross-layer design leads to better performance in QoS support. Extensive simulations show that our scheme can successfully provide better communication quality to important nodes at a relatively low price. Finally, several design issues and future work are discussed. Xiang Chen received the B.E. and M.E. degrees in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 1997 and 2000, respectively. Afterwards, he worked as a MTS (member of technical staff) in Bell Laboratories, Beijing, China. He is currently working toward the Ph.D. degree in the department of Electrical and Computer Engineering at the University of Florida. His research is focused on protocol design and performance evaluation in wireless networks, including cellular networks, wireless LANs, and mobile ad hoc networks. He is a member of Tau Beta Pi and a student member of IEEE. Wei Liu received the BE and ME degrees in electrical engineering from Huazhong University of Science and Technology, Wuhan, China, in 1998 and 2001, respectively. He is currently pursuing the P.hD. degree in the Department of Electrical and Computer Engineering, University of Florida, Gainesville, where he is a research assistant in the Wireless Networks Laboratory (WINET). His research interest includes QoS, secure and power efficient routing, and MAC protocols in mobile ad hoc networks and sensor networks. He is a student member of the IEEE. Hongqiang Zhai received the B.E. and M.E. degrees in electrical engineering from Tsinghua University, Beijing, China, in July 1999 and January 2002 respectively. He worked as a research intern in Bell Labs Research China from June 2001 to December 2001, and in Microsoft Research Asia from January 2002 to July 2002. Currently he is pursuing the Ph.D. degree in the Department of Electrical and Computer Engineering, University of Florida. He is a student member of IEEE. Yuguang Fang received a Ph.D. degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D. degree in Electrical Engineering from Boston University in May 1997. From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering at University of Florida where he got the early promotion to Associate Professor with tenure in August 2003 and to Full Professor in August 2005. He has published over 180 papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEETransactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications and Networking Conference (WCNC’2000).     

Connectivity management in mobile ad hoc networks using particle swarm optimization

This paper proposes a dynamic mobile ad hoc network (MANET) management system to improve network connectivity by using controlled network nodes, called agents. Agents have predefined wireless communication capabilities similar to the other nodes in the MANET, however their movements, and thus their locations, are dynamically determined to optimize network connectivity. A new approach to measuring connectivity using a maximum flow formulation is proposed – this is both responsive and tractable. Furthermore, users’ locations are predicted for several time steps ahead and this is shown to improve network connectivity over the network operation period. A particle swarm optimization (PSO) algorithm uses the maximum flow objective to choose optimal locations of the agents during each time step of network operation. The proposed MANET management system is rigorously tested on numerous static and dynamic problems. Computational results show that the proposed approach is effective in improving the connectivity of MANETs and predicting movements of user nodes and deploying agents accordingly significantly improves the overall performance of a MANET.     

Robust throughput and routing for mobile ad hoc wireless networks

Flows transported across mobile ad hoc wireless networks suffer from route breakups caused by nodal mobility. In a network that aims to support critical interactive real-time data transactions, to provide for the uninterrupted execution of a transaction, or for the rapid transport of a high value file, it is essential to identify robust routes across which such transactions are transported. Noting that route failures can induce long re-routing delays that may be highly interruptive for many applications and message/stream transactions, it is beneficial to configure the routing scheme to send a flow across a route whose lifetime is longer, with sufficiently high probability, than the estimated duration of the activity that it is selected to carry. We evaluate the ability of a mobile ad hoc wireless network to distribute flows across robust routes by introducing the robust throughput measure as a performance metric. The utility gained by the delivery of flow messages is based on the level of interruption experienced by the underlying transaction. As a special case, for certain applications only transactions that are completed without being prematurely interrupted may convey data to their intended users that is of acceptable utility. We describe the mathematical calculation of a network’s robust throughput measure, as well as its robust throughput capacity. We introduce the robust flow admission and routing algorithm (RFAR) to provide for the timely and robust transport of flow transactions across mobile ad hoc wireless network systems.     

Future trust management framework for mobile ad hoc networks [security in mobile ad hoc]

In mobile ad hoc networks nodes should collaborate with each other to support the functions of the network. The trust management framework, which evaluates the trust of participating nodes, is used to force nodes to cooperate in a normal way. We make an effort to design a robust and attack-resistant trust management framework for the future. In this article we describe the vulnerabilities of and possible attacks on existing frameworks. An objective trust management framework is proposed to overcome these vulnerabilities. We provide a theoretical basis and skeleton for this framework. The performance evaluation and security analysis are provided showing the effectiveness and robustness of the OTMF compared with existing frameworks.     

Intrusion detection techniques in mobile ad hoc and wireless sensor networks

Mobile ad hoc networks and wireless sensor networks have promised a wide variety of applications. However, they are often deployed in potentially adverse or even hostile environments. Therefore, they cannot be readily deployed without first addressing security challenges. Intrusion detection systems provide a necessary layer of in-depth protection for wired networks. However, relatively little research has been performed about intrusion detection in the areas of mobile ad hoc networks and wireless sensor networks. In this article, first we briefly introduce mobile ad hoc networks and wireless sensor networks and their security concerns. Then, we focus on their intrusion detection capabilities. Specifically, we present the challenge of constructing intrusion detection systems for mobile ad hoc networks and wireless sensor networks, survey the existing intrusion detection techniques, and indicate important future research directions.     

Detecting and avoiding wormhole attacks in wireless ad hoc networks [security in mobile ad hoc]

A particularly severe attack on routing protocols in ad hoc networks is the so-called worm- hole attack in which two or more colluding attackers record packets at one location, and tunnel them to another location for replay at that remote location. When this attack targets specifically routing control packets, the nodes that are close to the attackers are shielded from any alternative routes with more than one or two hops to the remote location. All routes are thus directed to the wormhole established by the attackers. In the optimized link state routing protocol, if a wormhole attack is launched during the propagation of link state packets, the wrong link information percolates throughout the network, leading to routing disruption. In this article we devise an efficient method to detect and avoid wormhole attacks in the OLSR protocOLSR protocolol. This method first attempts to pinpoint links that may potentially be part of a wormhole tunnel. Then a proper wormhole detection mechanism is applied to suspicious links by means of an exchange of encrypted probing packets between the two supposed neighbors (endpoints of the wormhole). The proposed solution exhibits several advantages, among which are its nonreliance on any time synchronization or location information, and its high detection rate under various scenarios.     

Mobile learning object authoring tool and management system for mobile ad hoc wireless networks

Mobile learning can augment formal education and bridge the gap between formal and informal education by creating extended learning communities using any digital technology in connected or infrastructure‐less environments. With the use of ad hoc networks and mobile authoring tools, we can now create an ‘on‐the‐fly’ learning scenario, where learners can create, share, and view content from their mobile devices without the need for server–client or infrastructure‐based liaisons. Mobile learning, however, is not just about sharing content or learning using mobile, wireless, and portable devices. Rather, it is learning across spatiotemporal contexts that enables learners to form knowledge and understanding in different scenarios. When facing limited resources stemming from the characteristics of mobility and wireless technologies, determining the best practices for content creation and delivery becomes a challenge. This paper describes the architecture of a mobile‐focused learning network designed so that learning tools, activities, contexts, and interactions are created as necessary over time and space while adhering to traditional learning object standards. Copyright © 2015 John Wiley & Sons, Ltd.     

Patient monitoring using ad hoc wireless networks: reliability and power management

In the health care domain, a major challenge is how to provide better health care services to an increasing number of people using limited financial and human resources. Wireless patient monitoring has the potential to support these multiple and conflicting requirements. However, the current quality and reliability of patient monitoring have not been very satisfactory due to the unpredictable and spotty coverage of infrastructure-oriented wireless networks. Ad hoc wireless networks can be formed among mobile and wearable patient-monitoring devices for improving the coverage of patient monitoring when infrastructure-oriented networks are not accessible. In this article, we provide support for reliable wireless patient monitoring by presenting several protocols for power management of devices, assisted power control, and sleep strategy. The performance results show that high reliability of message delivery can be obtained while maintaining a level of power conservation.     

动态无线传感器网络自组织协议的研究

目前多数移动自组织路由协议选择路径都是基于跳数最短的单径路由.从能量角度看,多数路由协议并没有充分利用网络资源.文章提出一种多径节能路由(Muhipath Saving Dynamic Source Routing,MSDR)协议.实验结果表明,该协议不仅提高了网络可靠性,而且还有效地延长了节点的工作时间和网络的整体寿命.