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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.comnet.2009.08.020 Byline: Zhenxia Zhang, Richard W. Pazzi, Azzedine Boukerche Keywords: Mobility management; Wireless mesh networks; Handoff; Seamless roaming; Real-time application Abstract: Recent advances in wireless mesh networks (WMNs) have overcome the drawbacks of traditional wired networks and wireless ad hoc networks. WMNs will play a leading role in the next generation of networks, and the question of how to provide seamless mobility management for WMNs is the driving force behind the research. The inherent characteristics of WMNs, such as relatively static backbones and highly mobile clients, require new mobility management solutions to be designed and implemented. In this paper, a hybrid routing protocol for forwarding packets is proposed: this involves both link layer routing and network layer routing. Based on the hybrid routing protocol, a mobility management scheme for WMNs is presented. Both intra-domain and inter-domain mobility management have been designed to support seamless roaming in WiFi-based WMNs. During intra-domain handoff, gratuitous ARP messages are used to provide new routing information, thus avoiding re-routing and location update. For inter-domain handoff, redundant tunnels are removed in order to minimize forwarding latency. Comprehensive simulation results illustrate that our scheme has low packet latency, low packet loss ratio and short handoff latency. As a result, real-time applications over 802.11 WMNs such as VoIP can be supported. Author Affiliation: PARADISE Research Laboratory, SITE, University of Ottawa, Canada K1N 6N5 Article Note: (footnote) [star] This work is partially supported by NSERC, Canada Research Chairs Program, The Ontario Research Fund (ORF), ORNEC, The Early Ontario Researcher Award, The Ontario Centres of Excellence (OCE), and MRI Ontario Funds.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.comnet.2007.09.023 Byline: Athanasios Bamis (a), Azzedine Boukerche (b), Ioannis Chatzigiannakis (c)(d), Sotiris Nikoletseas (c)(d) Keywords: Wireless ad hoc; Mobile networks; Mobility classification; Routing; Algorithmic design; Simulation; Performance evaluation Abstract: In mobile ad hoc networks (MANETs), the mobility of the nodes is a complicating factor that significantly affects the effectiveness and performance of the routing protocols. Our work builds upon recent results on the effect of node mobility on the performance of available routing strategies (i.e., path-based, using support) and proposes a protocol framework that exploits the usually different mobility rates of the nodes by adapting the routing strategy during execution. We introduce a metric for the relative mobility of the nodes, according to which the nodes are classified into mobility classes. These mobility classes determine, for any pair of origin and destination, the routing technique that best corresponds to their mobility properties. Moreover, special care is taken for nodes remaining almost stationary or moving with high (relative) speeds. Our key design goal is to limit the necessary implementation changes required to incorporate existing routing protocols into our framework. We provide extensive evaluation of the proposed framework, using a well-known simulator (NS2). Our first findings demonstrate that the proposed framework improves, in certain cases, the performance of existing routing protocols. Author Affiliation: (a) ENALAB, Yale University, New Haven, CT 06520, United States (b) SITE, University of Ottawa, Ontario, Canada K1N 6N5 (c) CEID, University of Patras, Rio 26500, Greece (d) Research Academic Computer Technology Institute (RACTI), Research Unit 1, 61 Riga Ferraiou Strasse, Rio 26500, Greece Article Note: (footnote) [star] This work has been partially supported by the IST Programme of the European Union under contract number IST-2005-15964 (AEOLUS). Dr. A. Boukerche's work is partially supported by NSERC and Canada Research Chair Program and CFI Funds.

Multi-channel cognitive radio ad hoc networks (CRAHNs) and information-centric networking (ICN) will be indispensable for enabling envisioned multimedia-based smart services within the umbrella of smart cities. Cognitive radios enable the efficient and opportunistic use of spectrum bands by using vacant licensed channels, whereas information- centric networking improves content distribution by decoupling producers and consumers. In this work, we discuss the design of information-centric cognitive radio-based networking for multimedia- based applications in smart cities. We examine the potential of the joint design of CRAHNs and ICN, and thoroughly review fundamental aspects and challenges of CR and ICN for smart cities. Subsequently, we qualitatively study the capability of information-centric cognitive radio-based networking for improving network connectivity, content search and distribution, reliability and confined delay in smart city safety and infotainment-based applications. Finally, we highlight future research directions for the design of protocols for this envisioned network that will support smart cities. [ABSTRACT FROM AUTHOR]

Addressing communication reliability and security has always been of significant importance in wireless networks. Opportunistic routing (OR) protocols comprise a promising area of research that aims to improve the reliability of communications, particularly in lossy networks. The main concept behind OR protocols is to utilize the broadcast nature of the wireless medium and determine a group of neighboring node candidates, known as candidate set, to collaboratively forward packets towards the destination using a candidate coordination approach. However, similar to traditional routing protocols, OR protocols operate poorly in the presence of malicious nodes and attackers. Therefore, researchers have designed and developed a number of security enhancements, considering the specific characteristics of such protocols. In this paper, following a brief overview on OR protocols, we examine, classify, and compare the different categories of security approaches proposed for OR protocols. More precisely, we divide security-related OR protocols into three categories, including trust-based approaches, game-theory-oriented solutions, and other related protocols. Furthermore, the most significant algorithms of each category are investigated as case studies. Finally, a comparison of different protocols is presented considering the main features, advantages, and shortcomings of each protocol. [ABSTRACT FROM AUTHOR]

Underwater wireless sensor networks (UWSNs) will pave the way for a new era of underwater monitoring and actuation applications. The envisioned landscape of UWSN applications will help us learn more about our oceans, as well as about what lies beneath them. They are expected to change the current reality where no more than 5% of the volume of the oceans has been observed by humans. However, to enable large deployments of UWSNs, networking solutions toward efficient and reliable underwater data collection need to be investigated and proposed. In this context, the use of topology control algorithms for a suit-able, autonomous, and on-the-fly organization of the UWSN topology might mitigate the undesired effects of underwater wireless communications and consequently improve the performance of networking services and protocols designed for UWSNs. This article presents and discusses the intrinsic properties, potentials, and current research challenges of topology control in underwater sensor networks. We propose to classify topology control algorithms based on the principal methodology used to change the network topology. They can be categorized in three major groups: power control, wireless interface mode management, and mobility assisted-based techniques. Using the proposed classification, we survey the current state of the art and present an in-depth discussion of topology control solutions designed for UWSNs. [ABSTRACT FROM AUTHOR]

Underwater sensor networks have enabled a new era in scientific and industrial underwater monitoring and exploration applications. However, these networks are energy-constrained and, more problematically, energy-hungry, as a consequence of the use of underwater acoustic links. In this work, we thoroughly review potential techniques for greening underwater sensor networks. In a top-down approach, we discuss the principal design and challenges of the appealing highlighted techniques. We also exemplify their use by surveying recent proposals in underwater sensor networks. Finally, we describe potential future research directions for energy conservation in underwater networks. [ABSTRACT FROM PUBLISHER]

Simulations have been used extensively for evaluating scenarios, which are very difficult, costly or impractical to implement in real systems. Testing in a synthetic, realistic environment provides a means to determine the viability of solutions. Simulations have proved to be very useful in the verification of algorithms and protocols, offering tools for testing them in different situations. The simulation of vehicular area networks pose additional challenges as realistic mobility models are crucial and must be incorporated in scenario elements while applications and communication protocols are tested. Several simulators and simulation frameworks have been designed that aim to synthetically reproduce communication and mobility of vehicles as realistically as possible. The majority of such simulators merge pre-existing networking and mobility simulators, which add issues regarding compatibility and realism. Such simulators present limited run-time 3D visualization tools, essential for providing immersive environments. Therefore, in this paper, we propose real-time simulation and 3D visualization for vehicular networks of realistic scenarios. This proposed simulation system generates output in real time, making use of 3D-modelled real-world maps and effectively generating visualization as elements are updated in the simulation. Experiments have been conducted with simulation and visualization components to evaluate delays and performance of the proposed simulator. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

VANETs have emerged as an exciting research and application area. Increasingly vehicles are being equipped with embedded sensors, processing and wireless communication capabilities. This has opened a myriad of possibilities for powerful and potential life-changing applications on safety, efficiency, comfort, public collaboration and participation, while they are on the road. Although, considered as a special case of a Mobile Ad Hoc Network, the high but constrained mobility of vehicles bring new challenges to data communication and application design in VANETs. This is due to their highly dynamic and intermittent connected topology and different application’s QoS requirements. In this work, we survey VANETs focusing on their communication and application challenges. In particular, we discuss the protocol stack of this type of network, and provide a qualitative comparison between most common protocols in the literature. We then present a detailed discussion of different categories of VANET applications. Finally, we discuss open research problems to encourage the design of new VANET solutions. [ABSTRACT FROM AUTHOR]

Transmission Control Protocol (TCP) performs poorly over wireless networks. Some research indicates that the TCP congestion control mechanism may cause burstiness in the traffic flow. Numerous TCP segments are delivered simultaneously, while an acknowledgement of a retransmission is successfully received. Burstiness leads to a highly contentious network, which markedly increases the probability of packet loss on wireless networks. TCP pacing is a possible solutions for TCP burstiness on multi-hop networks. In this algorithm, TCP segment transmissions are distributed over the whole Round Trip Time. Most pacing protocols attempt to insert a delay interval into the TCP transmissions. However, there is a similar pacing algorithm in IEEE802.11, known as the contention window mechanism. In this paper, we first measure and analyze the way that the contention window size affects TCP throughput in different scenarios. We propose a cross-layer TCP pacing protocol by contention control in the MAC layer, called TCP Contention Control (TCP-CC). It adjusts the lower bound of the contention window in order to optimize the overall TCP throughput in both one-hop and multi-hop topology. Finally, comparative simulations are conducted in order to verify the improvements of our protocol on both TCP Reno and TCP Vegas. [ABSTRACT FROM AUTHOR]

Video dissemination over Vehicular Ad Hoc Networks is an attractive technology that supports many novel applications. The merit of this work lies in the design of an efficient video dissemination protocol that provides high video quality at different data rates for urban scenarios. Our objective is to improve received video quality while meeting delay and packet loss. In this work, we first employ a reliable scheme known as connected dominating set, which is an efficient receiver-based routing scheme for broadcasting video content. To avoid repeated computing of the connected dominating set, we add three statuses to each node. In nonscalable video coding, the distribution of lost frames can cause a major impact on video quality at the receiver's end. Therefore, for the second step, we employ Interleaving to spread out the burst losses and to reduce the influence of loss distributions. Although Interleaving can reduce the influence of cluster frame loss, single packet loss is also a concern due to collisions, and to intermittent disconnection in the topology. In order to fix these single packet losses, we propose a store-carry-forward scheme for the nodes in order to retransmit the local buffer stored packets. The results, when compared to the selected base protocols, show that our proposed protocol is an efficient solution for video dissemination over urban Vehicular Ad Hoc Networks. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc networks have emerged as a promising research area. Designing a realistic coverage protocol for RSU deployment in vehicular networks presents a challenge due to different service area, assorted mobility patterns, and resource constraints. In order to resolve these problems, this paper proposes a geometry-based sparse coverage protocol GeoCover , which aims to consider the geometrical attributes of road networks, movement patterns of vehicles and resource limitations. By taking the dimensions of road segments into account, GeoCover provides a buffering operation to suit different types of road topology. By discovering hotspots from trace files, GeoCover is able to depict the mobility patterns and to discover the most valuable road area to be covered. To solve the resource-constrained coverage problem, we provide two variants of sparse coverage which take into consideration budget constraints and quality constraints, respectively. The coverage problem is resolved by both genetic algorithm and greedy algorithm. The simulation results verify that our coverage protocol is reliable and scalable for urban vehicular networks. [ABSTRACT FROM AUTHOR]

In this paper, we present an Efficient COngestion DEtection (ECODE) protocol that aims at evaluating the traffic characteristics of each road segment (i.e., the road section connecting between any two successive intersections). Moreover, ECODE efficiently and reliably detects road segments with high traffic congestion in any urban grid-layout area. The traffic situation and the congestion level of each road segment changes from time to time. Proactive, reactive, and hybrid iterative execution schemes have been proposed to execute ECODE repeatedly and to thus obtain a more real-time traffic evaluation of each road segment. These iterative execution schemes aim also at investigating the effects of several data dissemination mechanisms that are usually used to control the congestion over the communication network. ECODE is discussed and its performance is reported on and compared to previous protocols in this field; an extensive set of scenarios and experiments have been used which are in turn implemented by NS-2. From the experimental results, ECODE achieves a 30% more accurate evaluation of traffic characteristics compared to previous protocols in this field. Moreover, it consumes on average 60% of the bandwidth that was consumed by the previous protocols. Considering the iterative execution schemes of ECODE, the proactive scheme consumes 50% more bandwidth than the reactive scheme. However, the accuracy of the traffic evaluation per road segment using the reactive scheme is lower than the accuracy of the proactive scheme used for short intervals. The hybrid scheme lies between the proactive and the reactive schemes in terms of the bandwidth consumption and the accuracy of congestion level evaluation. Finally, we have used ECODE to evaluate the traffic congestion level and to investigate the traffic distribution over some main streets in the downtown area of Ottawa; this has been set up as a practical example of the application of ECODE. [ABSTRACT FROM AUTHOR]

In recent years, we have witnessed a growing interest in Vehicular Networks from both the research community and industry. Several potential applications of Vehicular Networks are envisioned such as road safety and security, streaming services, traffic monitoring and driving comfort, just to mention a few. It is critical that the existence of convenience or driving comfort services do not negatively affect the performance of safety services. In essence, the dissemination of safety services or the discovery of convenience applications require the communication among service providers and service requesters through constrained bandwidth resources. Therefore, service discovery techniques for vehicular networks must efficiently use the available common resources. In this paper, we present a bandwidth-efficient and scalable hybrid adaptive service discovery protocol (VSDP) for Vehicular Networks. VSDP aims at providing high success ratio while guaranteeing low response time and good scalability when the number of requests increases. Our proposed protocol finds the service provider and its routing information simultaneously which results in overall bandwidth savings. It uses diverse channels to exchange discovery and routing packets, thereby decreasing the congestion on single channels and decreasing the delay of service discovery. Our proposed service discovery protocol adapts the advertisement zone size of service providers based on an efficient adaptation mechanism that takes into consideration network condition and application requirements. The adaptation process is based on an adjustment technique and a prediction technique. We discuss the implementation of our protocol, present its proof of correctness as well as the performance evaluation through an extensive set of simulation experiments and using different mobility models. Our results show the scalability of our protocol. They indicate that our techniques can achieve significant success rate (more than 90 percent), while guaranteeing low response time (in the order of milliseconds) and low bandwidth usage when compared to existing service discovery techniques. [ABSTRACT FROM AUTHOR]

Behavioral patterns prediction in the context of Vehicular Ad hoc Networks (VANETs) has been receiving increasing attention due to the enabling of on-demand, intelligent traffic analysis and real-time responses to traffic issues. One of these patterns, sequential patterns, is a type of behavioral pattern that describes the occurrence of events in a timely and ordered fashion. In the context of VANETs, these events are defined as an ordered list of road segments traversed by vehicles during their trips from a starting point to their final intended destination. In this paper, a new set of formal definitions depicting vehicular paths as sequential patterns is described. Also, five novel communication schemes have been designed and implemented under a simulated environment to collect vehicular paths; such schemes are classified under two categories: RSU (Road Side Unit)-based and Vehicle-based. After collection, extracted frequent paths are obtained through data mining, and the probability of these frequent paths is measured. In order to evaluate the effectiveness and efficiency of the proposed schemes, extensive experimental analysis has been realized. [ABSTRACT FROM AUTHOR]

Abstract: With the growing popularity of vehicle-based mobile devices, vehicular networks are becoming an essential part of wireless heterogeneous networks. Therefore, vehicular networks have been widely studied in recent years. Because of limited transmission range of wireless antennas, mobile vehicles should also switch their access points to maintain the connections as conventional mobile nodes. Considering the inherent characteristics of vehicular networks such as dynamic topology and high speed, the question of how to implement handoff protocol under real-time scenarios is very important. IEEE 802.11p protocol is designed for vehicular networks for the long distance transmission. To reduce handoff latency for 802.11p protocol, the authentication phase is waived during the handoff. However, security is also very important for wireless communications, and authentication can forbid access from malicious nodes and prevent wireless communications from potential attacks. Thus, in this paper, a lightweight authentication scheme is introduced to balance the security requirements and the handoff performance for 802.11p vehicular networks. In our scheme, the access points are divided into different trust groups, and the authentication process is completed in a group-based method. Once a vehicle is authenticated by an access point group, during the handoff within the same group, few extra authentication operations are needed. As a result, there is no extra overhead introduced to the authentication servers. Simulation results demonstrate that our authentication scheme only introduces small handoff latency and it is ideal for vehicular networks. [Copyright &y& Elsevier]

With the rapidly growing popularity of mobile ad hoc networks (MANETs), many security concerns have arisen from this type of network. In particular, malicious nodes will jeopardize the security of mobile networks if the issues of secure data exchange are not handled properly. Encryption cannot fully protect the data communicated between nodes, as routing information may expose the identities of the communicating nodes and put their relationships at risk. In this paper, we propose an efficient anonymous routing protocol that uses a mobile agent paradigm for MANETs, which we refer to as ARMA. In our protocol, we take advantage of a trust system to prevent effectively the misbehavior of malicious nodes so that only trustworthy nodes are allowed to participate in communications. Furthermore, we present the Malicious Encryption and Malicious ID attacks, as well as other attacks, and note how our scheme is robust to them. Through the proof of protocol correctness, our protocol is analyzed to show how it offers provable security properties. Finally, we provide its performance evaluation based on simulation experiments implemented in an ns-2 simulator. Compared to the secure distributed route construction protocol (SDAR) protocol, our experimental results demonstrate that our scheme not only achieves the necessary anonymity in wireless and mobile networks, but also provides more security with reasonably little additional overhead. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The establishment of a localization system is an important task in wireless sensor networks. Due to the geographical correlation between sensed data, location information is commonly used to name the gathered data and address nodes and regions in data dissemination protocols. In general, to estimate its location, a node needs the position information of at least three reference points (neighbors that know their positions). In this work, we propose a different scheme in which only two reference points are required in order to estimate a position. To choose between the two possible solutions of an estimate, we use the known direction of the recursion. This approach leads to a recursive localization system that works with low-density networks (increasing by 40 percent the number of nodes with estimates in some cases), reduces the position error by almost 30 percent, requires 37 percent less processor resources to estimate a position, uses fewer beacon nodes, and also indicates the node position error based on its distance to the recursion origin. No GPS-enabled node is required, since the recursion origin can be used as a relative coordinate system. The algorithm's evaluation is performed by comparing it with a similar localization system; also, experiments are made to evaluate the impact of both systems in geographic algorithms. [ABSTRACT FROM AUTHOR]

Abstract: Applications that require fine-grain monitoring of physical environments subjected to critical conditions, such as fire, leaking of toxic gases and explosions, pose a great challenge to sensor network protocols. These networks have to provide a fast, reliable, fault-tolerant and energy-aware channel for events diffusion, which meets the requirements of query-based, event-driven and periodic sensor networks application scenarios. These requirements have to be met even in the presence of emergency conditions that can lead to node failures and path disruption to the sink. This paper proposes two routing protocols: periodic, event-driven and query-based protocol (PEQ) and its variation CPEQ, two fault-tolerant and low-latency algorithms that meet sensor network requirements for critical conditions supervision in context-aware physical environments. While PEQ can provide low latency for event notification, fast broken path reconfiguration, and high reliability in the delivery of event packets for low-network data traffic, CPEQ is a cluster-based routing protocol that groups sensor nodes to efficiently relay the sensed data to the sink by uniformly distributing energy dissipation among the nodes and reducing latency for high-network data traffic (typical in emergency situations). PEQ and its variant CPEQ use the publish/subscribe paradigm to disseminate requests across the network. We discuss both PEQ and CPEQ protocols, their implementation, and report on the performance results of several scenarios using NS-2 simulator. The results obtained are compared with the well-known directed diffusion (DD) protocol, and show that our proposed algorithms exhibit a clear indication to meet the constraints and requirements of critical condition supervision in context-aware physical environments. Our results indicate that PEQ outperforms DD in the average delay since it uses the shortest path for the delivery of packets and speed up new subscriptions by using the reverse path used for event notification packets. CPEQ also outperforms DD in both the average delay and in the packet delivery ratio when the network scales up. [Copyright &y& Elsevier]

Ad hoc networks are useful for providing communication support where no fixed infrastructure exists or the deployment of a fixed infrastructure is not economically profitable, and movement of communicating parties is allowed. Therefore, such networks are designed to operate in widely varying environments, from military networks to low-power sensor networks and other embedded systems. Frequent topology changes caused by node mobility make routing in ad hoc wireless networks a challenging problem. In this paper, we propose an efficient ad hoc routing algorithm, which we refer to as GZRP, a hybrid protocol that makes use of the ZRP scheme and the Global Positioning System (GPS). As opposed to the ZRP original scheme, our GZRP scheme consists of propagating the routing (query) messages only to the nodes that are further away from the query source. We discuss the algorithm, its implementation, and report on the performance of GZRP scheme, and compare it to the ZRP routing protocol using an extensive simulation experiment. Our results indicate clearly that GZRP outperforms ZRP by reducing significantly the number of route query messages, and thereby increases the efficiency of the network load. Furthermore, we show that careful GPS screening angle is an important factor in the success of the GZRP ad hoc routing protocol. [ABSTRACT FROM AUTHOR]

Introduces articles about wireless and mobile communication systems, published in the March 2001 issue of the periodical 'Journal of Interconnection Networks.' Routing problem in ad hoc mobile networks; Performance of on-demand ad hoc routing protocols; Use of global positioning systems to reduce the overhead of traffic flow.

In this paper, we present the performance evaluation of an algorithm for preserving temporal relationships of events in Wireless Sensor Actor Networks (WSANs). The algorithm consists of two modules, which deal with the problems of temporal event ordering and time synchronization. These two problems are approached as a whole as they complement each other: in order to temporally order the events, the nodes must be synchronized. The goal of the proposed event ordering algorithm for WSANs is to reduce the overhead in terms of energy dissipation and delay. We also propose a tunable time synchronization algorithm employing a hybrid synchronization scheme suited for clustered topology. The proposed algorithm utilizes the message exchange necessary for event ordering and routing for synchronization purposes by piggybacking messages with synchronization pulses and replies to reduce the communication cost of synchronization. Simulation experiments showed that the event ordering algorithm is capable of reducing the overhead when compared to previously proposed algorithms. The synchronization algorithm demonstrated that the combination of synchronization techniques was well suited for the communication mode utilized in a clustered topology. The approach of piggybacking synchronization pulses and replies resulted in a considerable gain, which we demonstrated in the number of messages that were piggybacked for synchronization purposes. [ABSTRACT FROM AUTHOR]