On-demand power management for ad hoc networks

Battery power is an important resource in ad hoc networks. It has been observed that in ad hoc networks, energy consumption does not reflect the communication activities in the network. Many existing energy conservation protocols based on electing a routing backbone for global connectivity are oblivious to traffic characteristics. In this paper, we propose an extensible on-demand power management framework for ad hoc networks that adapts to traffic load. Nodes maintain soft-state timers that determine power management transitions. By monitoring routing control messages and data transmission, these timers are set and refreshed on-demand. Nodes that are not involved in data delivery may go to sleep as supported by the MAC protocol. This soft state is aggregated across multiple flows and its maintenance requires no additional out-of-band messages. We implement a prototype of our framework in the ns-2 simulator that uses the IEEE 802.11 MAC protocol. Simulation studies using our scheme with the Dynamic Source Routing protocol show a reduction in energy consumption near 50% when compared to a network without power management under both long-lived CBR traffic and on–off traffic loads, with comparable throughput and latency. Preliminary results also show that it outperforms existing routing backbone election approaches.     

Application versus network layer multicasting in ad hoc networks: the ALMA routing protocol

Application layer multicasting has emerged as an appealing alternative to network layer multicasting in wireline networks. Here, we examine the suitability of application layer multicast in ad hoc networks. To this effect, we propose a flexible receiver-driven overlay multicast protocol which we call Application Layer Multicast Algorithm (ALMA). ALMA constructs an overlay multicast tree in a dynamic, decentralized and incremental way. First, ALMA is receiver-driven: the member nodes find their connections according to their needs. Second, it is flexible, and thus, it can satisfy the performance goals and the needs of a wide range of applications. Third, it is highly adaptive: it reconfigures the tree in response to mobility or congestion. In addition, our protocol has the advantages of an application layer protocol: (a) simplicity of deployment, (b) independence from lower layer protocols, and (c) capability of exploiting features such as reliability and security that may be provided by the lower layers. Through extensive simulations, we show that ALMA performs favorably against the currently best application layer and network layer protocols. In more detail, we find that ALMA performs significantly better than ODMRP, a network layer, for small group sizes. We conclude that the application layer approach and ALMA seem very promising for ad hoc multicasting.     

Security considerations in ad hoc sensor networks

In future smart environments, ad hoc sensor networks will play a key role in sensing, collecting, and disseminating information about environmental phenomena. As sensor networks come to be wide-spread deployment, security issues become a central concern. So far, the main research focus has been on making sensor networks feasible and useful, and less emphasis has been placed on security. This paper analyzes security challenges in wireless sensor networks and summarizes key issues that need be solved for achieving security in an ad hoc network. It gives an overview of the current state of solutions on such key issues as secure routing, prevention of denial-of-service, and key management service.     

Power proximity based key management for secure multicast in ad hoc networks

As group-oriented services become the focal point of ad hoc network applications, securing the group communications becomes a default requirement. In this paper, we address the problem of group access in secure multicast communications for wireless ad hoc networks. We argue that energy expenditure is a scarce resource for the energy-limited ad hoc network devices and introduce a cross-layer approach for designing energy-efficient, balanced key distribution trees to perform key management. To conserve energy, we incorporate the network topology (node location), the “power proximity” between network nodes and the path loss characteristics of the medium in the key distribution tree design. We develop new algorithms for homogeneous as well as heterogeneous environments and derive their computational complexity. We present simulation studies showing the improvements achieved for three different but common environments of interest, thus illustrating the need for cross-layer design approaches for security in wireless networks. Loukas Lazos received the B.S. and M.S. degrees from the Electrical Engineering Department, National Technical University of Athens, Athens, Greece, in 2000 and 2002, respectively. He is currently working towards the Ph.D. degree in the Electrical Engineering Department, University of Washington, Seattle. His current research interests focus on cross-layer designs for energy-efficient key management protocols for wireless ad-hoc networks, as well as secure localization systems for sensor networks. Radha Poovendran received the Ph.D. degree in electrical engineering from the University of Maryland, College Park, in 1999. He has been an Assistant Professor in the Electrical Engineering Department, University of Washington, Seattle, since September 2000. His research interests are in the areas of applied cryptography for multiuser environment, wireless networking, and applications of information theory to security. Dr. Poovendran is a recipient of the Faculty Early Career Award from the National Science Foundation (2001), Young Investigator Award from the Army Research Office (2002), Young Investigator Award from the Office of Naval Research (2004), and the 2005 Presidential Early Career Award for Scientists and Engineers, for his research contributions in the areas of wired and wireless multiuser security.     

Improved ID-based security framework for ad hoc network

As mobile devices with wireless communication capacity become more and more popular, the study on ad hoc networks that offer convenient infrastructure-free communication has arose the attention from both the academic and the industry. However, the previous security schemes proposed for ad hoc networks either suffer from the structure support problems or have security flaws. This paper examines the weaknesses of a Bohio–Miri’s recent work, and then proposes our new schemes to enhance the security and the performance. The security of the proposed protocols is proved in the random oracle model.     

SPREAD: Improving network security by multipath routing in mobile ad hoc networks

We propose and investigate the SPREAD scheme as a complementary mechanism to enhance secure data delivery in a mobile ad hoc network. The basic idea is to transform a secret message into multiple shares, and then deliver the shares via multiple paths to the destination so that even if a certain number of message shares are compromised, the secret message as a whole is not compromised. We present the overall system architecture and discuss three major design issues: the mathematical model for the generation and reconstruction of the secret message shares, the optimal allocation of the message shares onto multiple paths in terms of security, and the multipath discovery techniques in a mobile ad hoc network. Our extensive simulation results justify the feasibility and the effectiveness of the SPREAD approach.

Location safety protection in ad hoc networks

Many routing protocols and applications developed for ad hoc networks rely on location information of participating nodes. The exposure of such information, however, presents significant safety threats to the networks. In this paper, we investigate the problem of preventing an adversary from locating (and thus destroying) nodes based on their location information they disclose in communications. Our idea is to reduce location resolution to achieve a desired level of safety protection. We define the safety level of a geographic region to be the ratio of its area and the number of nodes inside it. The higher safety level a region has, the less attractive for an adversary to search over it for the nodes. When a node has to disclose its location, it can compute a cloaking box that meets a desired level of safety requirement and report that as its current location information. To implement this simple idea, there are several challenges. First, each cloaking box must be as small as possible in order to minimize the impact of reduced location resolution on the efficiency of network operating and applications. Second, nodes must be able to compute their cloaking boxes without having to reveal their accurate position. Finally, given a sequence of cloaking boxes, they must not be correlated to refine an area whose safety level is less than the requirement. Our research addresses these challenges with cost-effective solutions in the context of both stationary and mobile ad hoc networks. We evaluate the performance of our techniques through both mathematical analysis and simulation. In addition, we present a new geographic routing protocol which can work with blurred location information and evaluate the impact of location resolution reduction on the performance of this technique.     

Enabling SIP-based sessions in ad hoc networks

The deployment of infrastructure-less ad hoc networks is suffering from the lack of applications in spite of active research over a decade. This problem can be solved to a certain extent by porting successful legacy Internet applications and protocols to the ad hoc network domain. Session Initiation Protocol (SIP) is designed to provide the signaling support for multimedia applications such as Internet telephony, Instant Messaging, Presence etc. SIP relies on the infrastructure of the Internet and an overlay of centralized SIP servers to enable the SIP endpoints discover each other and establish a session by exchanging SIP messages. However, such an infrastructure is unavailable in ad hoc networks. In this paper, we propose two approaches to solve this problem and enable SIP-based session setup in ad hoc networks (i) a loosely coupled approach, where the SIP endpoint discovery is decoupled from the routing procedure and (ii) a tightly coupled approach, which integrates the endpoint discovery with a fully distributed cluster based routing protocol that builds a virtual topology for efficient routing. Simulation experiments show that the tightly coupled approach performs better for (relatively) static multihop wireless networks than the loosely coupled approach in terms of the latency in SIP session setup. The loosely coupled approach, on the other hand, generally performs better in networks with random node mobility. The tightly coupled approach, however, has lower control overhead in both the cases. This work was partially done while the author was a graduate student in CReWMaN, University of Texas at Arlington. Dr. Nilanjan Banerjee is a Senior Research Engineer in the Networks Research group at Motorola India Research Labs. He is currently working on converged network systems. He received his Ph.D. and M.S. in computer science and engineering from University of Texas at Arlington. He received his B.E. degree in the same discipline from Jadavpur University, India. His research interests include telecom network architectures and protocols, identity management and network security, mobile and pervasive computing, measures for performance, modeling and simulation, and optimization in dynamic systems. Dr Arup Acharya is a Research Staff Member in the Internet Infrastructure and Computing Utilities group at IBM T.J. Watson Research Center and leads the Advanced Networking micropractice in On-Demand Innovation Services. His current work includes SIP-based services such as VoIP, Instant Messaging and Presence, and includes customer consulting engagements and providing subject matter expertise in corporate strategy teams. Presently, he is leading a IBM Research project on scalability and performance of SIP servers for large workloads. In addition, he also works on different topics in mobile/wireless networking such as mesh networks. He has published extensively in conferences/journals and has been awarded seven patents. Before joining IBM in 2000, he was with NEC C&C Research Laboratories, Princeton. He received a B.Tech degree in Computer Science from the Indian Institute of Technology, Kharagpur and a PhD in Computer Science from Rutgers University in 1995. Further information is available at Dr. Sajal K. Das is a Professor of Computer Science and Engineering and also the Founding Director of the Center for Research in Wireless Mobility and Networking (CReWMaN) at the University of Texas at Arlington (UTA). His current research interests include sensor networks, resource and mobility management in wireless networks, mobile and pervasive computing, wireless multimedia and QoS provisioning, wireless internet architectures and protocols, grid computing, applied graph theory and game theory. He has published over 400 research papers in these areas, holds four US patents in wireless internet and mobile networks. He received Best Paper Awards in IEEE PerCom’06, ACM MobiCom’99, ICOIN’02, ACM MSwiM’00 and ACM/IEEE PADS’97. He is also recipient of UTA’s Outstanding Faculty Research Award in Computer Science (2001 and 2003), College of Engineering Research Excellence Award (2003), the University Award for Distinguished record of Research (2005), and UTA Academy of Distinguished Scholars Award (2006). He serves as the Editor-in-Chief of Pervasive and Mobile Computing journal, and as Associate Editor of IEEE Transactions on Mobile Computing, ACM/Springer Wireless Networks, IEEE Transactions on Parallel and Distributed Systems. He has served as General or Program Chair and TPC member of numerous IEEE and ACM conferences. He is a member of IEEE TCCC and TCPP Executive Committees.     

Improving TCP performance in ad hoc networks using signal strength based link management

Mobility in ad hoc networks causes frequent link failures, which in turn causes packet losses. TCP attributes these packet losses to congestion. This incorrect inference results in frequent TCP re-transmission time-outs and therefore a degradation in TCP performance even at light loads. We propose mechanisms that are based on signal strength measurements to alleviate such packet losses due to mobility. Our key ideas are (a) if the signal strength measurements indicate that a link failure is most likely due to a neighbor moving out of range, in reaction, facilitate the use of temporary higher transmission power to keep the link alive and, (b) if the signal strength measurements indicate that a link is likely to fail, initiate a route re-discovery proactively before the link actually fails. We make changes at the MAC and the routing layers to predict link failures and estimate if a link failure is due to mobility. We also propose a simple mechanism at the MAC layer that can help alleviate false link failures, which occur due to congestion when the IEEE 802.11 MAC protocol is used. We compare the above proactive and reactive schemes and also demonstrate the benefits of using them together and along with our MAC layer extension. We show that, in high mobility, the goodput of a TCP session can be improved by as much as 75% at light loads (when there is only one TCP session in the network) when our methods are incorporated. When the network is heavily loaded (i.e., there are multiple TCP sessions in the network), the proposed schemes can improve the aggregate goodput of the TCP sessions by about 14–30%, on average.     

基于UWB的Ad hoc无线网络

介绍了采用超宽带UWB技术的Adhoc无线网络,重点阐述了网络的两个关键技MAC协议和路由算法协议.     

Evolution and future directions of the ad hoc on-demand distance-vector routing protocol

The ad hoc on-demand distance-vector (AODV) routing protocol has been designed for use in ad hoc networks, which are presently receiving wide interest within many diverse research communities. These networks represent a significant departure from traditional wired networks due to the distinguishing characteristics of both the wireless channel and mobile devices. Consequently, AODV incorporates many novel features for handling mobility, reduced capacity links, and the variable, indeterminate nature of the signaling range of wireless media. Since its initial design, AODV has evolved in a number of ways for improved performance, robustness, and better scalability. Nevertheless, we see many opportunities for continued improvement. This paper describes the current state of AODV, including its base functionality as well as optional features that improve performance and add capabilities. We also offer some direction for the continued evolution of AODV by presenting areas that can be targeted for future enhancements. Many of the described current and planned features are a result of AODV’s history and evolution within the Internet engineering task force.     

Probabilistic reliable multicast in ad hoc networks

When striving for reliability, multicast protocols are most commonly designed as deterministic solutions. Such an approach seems to make the reasoning about reliability guarantees (traditionally, binary, “all-or-nothing”-like) in the face of packet losses and/or node crashes. It is however precisely this determinism that tends to become a limiting factor when aiming at both reliability and scalability, particularly in highly dynamic networks, e.g., ad hoc networks. Gossip-based multicast protocols appear to be a viable path towards providing multicast reliability guarantees. Such protocols embrace the non-deterministic nature of ad hoc networks, providing analytically predictable probabilistic reliability guarantees at a reasonable overhead.

This paper presents the Route Driven Gossip (RDG) protocol, a gossip-based multicast protocol designed precisely to meet a more practical specification of probabilistic reliability in ad hoc networks. Our RDG protocol can be deployed on any basic on-demand routing protocol, achieving a high level of reliability without relying on any inherent multicast primitive. We illustrate our RDG protocol by layering it on top of the “bare” Dynamic Source Routing protocol, and convey our claims of reliability and scalability through both analysis and simulation.     

Routing characteristics of ad hoc networks with unidirectional links

Unidirectional links in an ad hoc network can result from factors such as heterogeneity of receiver and transmitter hardware, power control or topology control algorithms, or differing sources of interference or jamming. Previously proposed metrics for evaluating the difficulty of a unidirectional scenario are limited in scope and are frequently misleading. To be able to analyze ad hoc network routing protocol behavior in a complex networking environment, it is not sufficient to merely assign a single level of difficulty to a unidirectional network scenario; the many interrelated routing characteristics of these scenarios must be understood. In this paper, we develop a set of metrics for describing these characteristics, for example for characterizing routing scenarios in simulations, analysis, and testbed implementations. Based on these metrics, we perform a detailed simulation analysis of the routing characteristics of the three most common simulation models for generating unidirectional links in ad hoc networks: the random-power model, the two-power model, and the three-power model. Our findings enable protocol designers to better choose a set of network scenarios and parameters that truly explore a wide range of a routing protocol’s behaviors in the presence of unidirectional links, and to better understand the complex interplay between routing mechanisms and network conditions.     

Secure hosts auto-configuration in mobile ad hoc networks

All existing routing protocols of Mobile Ad Hoc networks (MANET) assume that IP addresses of hosts are already configured before they join the network. In traditional schemes, this task is delegated to the dynamic host configuration protocol (DHCP [R. Droms, Dynamic host configuration protocol, RFC 2131, March 1997]), which allots an IP address to each requesting node. However, this process can not be applied in the context of MANET because of the lack of infrastructure and the great mobility that characterize them. A manual management of the addresses can be considered as long as the number of nodes remains reasonable. On the other hand, it is not possible any more since the network reaches a certain size. Some works proposed solutions to allow an automatic configuration of the nodes, i.e. without human intervention. Unfortunately these processes, often inspired of the traditional wired networks, are not always well adapted to MANET and appear relatively greedy concerning for example the delay, the address space or the bandwidth. Moreover, they apply only to ideal networks in which all nodes can trust each other. In this manner, they do absolutely not consider the security aspects and are thus not adapted to a real use in potentially hostile environment. In this paper, we propose a node auto-configuration scheme which uses the buddy system technique to allocate the addresses, as well as an algorithm allowing to authenticate the participants inside the network.     

Smart antenna based broadcasting in wireless ad hoc networks

Smart antennas have the advantage over traditional omnidirectional antennas of being able to orientate radio signals into the concerned directions in either transmission mode or in reception mode. Since the omnidirectional antenna use in broadcasting over the whole network is the source of an excessive redundancy of broadcast packet receptions within each node, we suggest using smart antennas to improve the medium usage in the case of broadcasting. We propose to adapt a current broadcast protocol to smart antenna applications and present two smart antenna broadcast approaches. We also present a comparative performance study between omnidirectional and smart antennas when broadcasting. We show that we can improve battery power utilisation and bandwidth usage with smart antennas.     

Estimating the value of co-operation approaches for multi-hop ad hoc networks

In multi-hop ad hoc networks, each node may be involved in forwarding data acting as a router. Unfortunately, in civilian scenarios with usually an open community, it is not obvious why nodes should forward foreign data and waste their battery power, CPU cycles, etc. Some work has already been done in proposing approaches to intensify participation in ad hoc networks. However, it is more or less a question of belief whether these approaches really benefit the community. This work gives a rational estimation of the effect of approaches that intensify participation in ad hoc networks. We present essential results assuming in particular low-dense networks that use on-demand routing protocols by applying some fundamental statistics to the problem.     

一种基于北斗的混合式无线自组网系统设计

在林业、消防、治安反恐、军事等领域,任务单元之间灵活、可靠的动态自组网数据传递,是提高一体化指挥能力和快速响应能力的关键所在。传统的无线局域自组网技术易受距离、遮挡等条件限制,在大区域、有遮挡条件下的应用有一定局限性。文章基于北斗系统定位和短报文通信能力,结合无线局域自组网技术,利用北斗应用终端设备为骨干构建了分层编组逻辑网络,有效扩大了覆盖范围和增强了组网可靠性。不同参数的网络变化与修复过程的仿真表明,该系统能够实现动态环境中网络修复与重组,提供可靠通信保障,解决了多种场合下所需的精确、无间断一体化指挥要求。     

Topology and mobility considerations in mobile ad hoc networks

A highly dynamic topology is a distinguishing feature and challenge of a mobile ad hoc network. Links between nodes are created and broken, as the nodes move within the network. This node mobility affects not only the source and/or destination, as in a conventional wireless network, but also intermediate nodes, due to the network’s multihop nature. The resulting routes can be extremely volatile, making successful ad hoc routing dependent on efficiently reacting to these topology changes.

In order to better understand this environment, a number of characteristics have been studied concerning the links and routes that make up an ad hoc network. Several network parameters are examined, including number of nodes, network dimensions, and radio transmission range, as well as mobility parameters for maximum speed and wait times. In addition to suggesting guidelines for the evaluation of ad hoc networks, the results reveal several properties that should be considered in the design and optimization of MANET protocols.     

Load balancing and resource reservation in mobile ad hoc networks

To ensure uninterrupted communication in a mobile ad hoc network, efficient route discovery is crucial when nodes move and/or fail. Hence, protocols such as Dynamic Source Routing (DSR) precompute alternate routes before a node moves and/or fails. In this paper, we modify the way these alternate routes are maintained and used in DSR, and show that these modifications permit more efficient route discovery when nodes move and/or fail. Our routing protocol also does load balancing among the number of alternate routes that are available. Our simulation results show that maintenance of these alternate routes (without affecting the route cache size at each router) increases the packet delivery ratio. We also show that our approach enables us to provide QoS guarantees by ensuring that appropriate bandwidth will be available for a flow even when nodes move. Towards this end, we show how reservations can be made on the alternate routes while maximizing the bandwidth usage in situations where nodes do not move. We also show how the load of the traffic generated due to node movement is shared among several alternate routes. In addition, we adaptively use Forward Error Correction techniques with our protocol and show how it can improve the packet delivery ratio.     

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).