Underwater sensor nodes will find applications in oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation and tactical surveillance applications. Moreover, unmanned or autonomous underwater vehicles (UUVs, AUVs), equipped with sensors, will enable the exploration of natural undersea resources and gathering of scientific data in collaborative monitoring missions. Underwater acoustic networking is the enabling technology for these applications. Underwater networks consist of a variable number of sensors and vehicles that are deployed to perform collaborative monitoring tasks over a given area. In this paper, several fundamental key aspects of underwater acoustic communications are investigated. Different architectures for two-dimensional and three-dimensional underwater sensor networks are discussed, and the characteristics of the underwater channel are detailed. The main challenges for the development of efficient networking solutions posed by the underwater environment are detailed and a cross-layer approach to the integration of all communication functionalities is suggested. Furthermore, open research issues are discussed and possible solution approaches are outlined. � 2005 Published by Elsevier B.V.

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Underwater acoustic sensor networks: research challenges

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A Break in the Clouds: Towards a Cloud Definition

Unmanned aerial vehicles (UAVs) have enormous potential in the public and civil domains. These are particularly useful in applications, where human lives would otherwise be endangered. Multi-UAV systems can collaboratively complete missions more efficiently and economically as compared to single UAV systems. However, there are many issues to be resolved before effective use of UAVs can be made to provide stable and reliable context-specific networks. Much of the work carried out in the areas of mobile ad hoc networks (MANETs), and vehicular ad hoc networks (VANETs) does not address the unique characteristics of the UAV networks. UAV networks may vary from slow dynamic to dynamic and have intermittent links and fluid topology. While it is believed that ad hoc mesh network would be most suitable for UAV networks yet the architecture of multi-UAV networks has been an understudied area. Software defined networking (SDN) could facilitate flexible deployment and management of new services and help reduce cost, increase security and availability in networks. Routing demands of UAV networks go beyond the needs of MANETS and VANETS. Protocols are required that would adapt to high mobility, dynamic topology, intermittent links, power constraints, and changing link quality. UAVs may fail and the network may get partitioned making delay and disruption tolerance an important design consideration. Limited life of the node and dynamicity of the network lead to the requirement of seamless handovers, where researchers are looking at the work done in the areas of MANETs and VANETs, but the jury is still out. As energy supply on UAVs is limited, protocols in various layers should contribute toward greening of the network. This paper surveys the work done toward all of these outstanding issues, relating to this new class of networks, so as to spur further research in these areas.

Survey of Important Issues in UAV Communication Networks

Recent developments and technological advancements in wireless communication, MicroElectroMechanical Systems (MEMS) technology and integrated circuits has enabled low-power, intelligent, miniaturized, invasive/non-invasive micro and nano-technology sensor nodes strategically placed in or around the human body to be used in various applications, such as personal health monitoring. This exciting new area of research is called Wireless Body Area Networks (WBANs) and leverages the emerging IEEE 802.15.6 and IEEE 802.15.4j standards, specifically standardized for medical WBANs. The aim of WBANs is to simplify and improve speed, accuracy, and reliability of communication of sensors/actuators within, on, and in the immediate proximity of a human body. The vast scope of challenges associated with WBANs has led to numerous publications. In this paper, we survey the current state-of-art of WBANs based on the latest standards and publications. Open issues and challenges within each area are also explored as a source of inspiration towards future developments in WBANs.

Wireless Body Area Networks: A Survey

Space-air-ground integrated network (SAGIN), as an integration of satellite systems, aerial networks, and terrestrial communications, has been becoming an emerging architecture and attracted intensive research interest during the past years. Besides bringing significant benefits for various practical services and applications, SAGIN is also facing many unprecedented challenges due to its specific characteristics, such as heterogeneity, self-organization, and time-variability. Compared to traditional ground or satellite networks, SAGIN is affected by the limited and unbalanced network resources in all three network segments, so that it is difficult to obtain the best performances for traffic delivery. Therefore, the system integration, protocol optimization, resource management, and allocation in SAGIN is of great significance. To the best of our knowledge, we are the first to present the state-of-the-art of the SAGIN since existing survey papers focused on either only one single network segment in space or air, or the integration of space-ground, neglecting the integration of all the three network segments. In light of this, we present in this paper a comprehensive review of recent research works concerning SAGIN from network design and resource allocation to performance analysis and optimization. After discussing several existing network architectures, we also point out some technology challenges and future directions.

Space-Air-Ground Integrated Network: A Survey

In this paper, we consider a network of energy constrained sensors deployed over a region. Each sensor node in such a network is systematically gathering and transmitting sensed data to a base station (via clusterheads). This paper focuses on reducing the power consumption of wireless sensor networks. We first extend LEACH's stochastic clusterhead selection algorithm by an average energy-based (LEACH-AE) deterministic component to reduce energy consumption. And then an unequal clustering idea is introduced to further reduce energy consumption of clusterheads. Simulation results show that our modified scheme can extend the network life by up to 38% before the first node dies in the network. Through both theoretical analysis and numerical results, it is shown that the proposed algorithm achieves better performance than the existing clustering algorithms such as LEACH, DCHS, LEACH-C.

An energy-efficient adaptive clustering algorithm for wireless sensor networks

https://opus.lib.uts.edu.au/bitstream/10453/32273/1/main%20%281%29.pdf

Including general environmental effects in K -factor approximation for rice-distributed VANET channels

The Optimised Link State Routing (OLSR) is a proactive routing protocol which relies on periodical broadcast of routing packets. However, due to the one-to-many relationship of broadcast traffic, the delivery of these packets can not be guaranteed by underlying MAC protocol, particularly in a congested condition. In this paper, the possible routing pathologies and failures of OLSR in a congested network are explored. In addition, a hybrid routing protocol which integrates OLSR with Reactive Route Recovery (OLSR-R3) is proposed to rectify the erratic routing behaviour described in this paper. Simulation studies are presented which show that the proposed solution is effective in addressing the underlining problems.

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OLSR-R 3 : Optimised link state routing with reactive route recovery

This paper presents two new route update strategies for performing proactive route discovery in mobile ad hoc networks (MANETs). The first strategy is referred to as minimum displacement update routing (MDUR). In this strategy, the rate at which route updates are sent into the network is controlled by how often a node changes its location by a required distance. The second strategy is called minimum topology change update (MTCU). In this strategy, the route updating rate is proportional to the level of topology change each node experiences. We implemented MDUR and MTCU on top of the fisheye state routing (FSR) protocol and investigated their performance by simulation. The simulations were performed in a number of different scenarios, with varied network mobility, density, traffic, and boundry. Our result indicate that both MDUR and MTCU produce significantly lower levels of control overhead than FSR and achieve higher levels of throughput as the dencity and the level of traffic in the network are increased.

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A new strategy to improve proactive route updates in mobile ad hoc networks

This paper presents a new route update strategy for performing proactive route discovery in Mobile Ad hoc Networks (MANETs). In this strategy, the rate at which route updates are sent into the network is controlled by how often a node changes its location by a required distance. We refer to this updating strategy as Minimum Displacement Update Routing (MDUR). We imple- mented MDUR on top of the Fisheye State Routing (FSR) protocol and investigated its performance by simulation. The simulations where performed in a number of different scenarios, with varied network mobility, density, traffic and boundary. Our results in- dicate that MDUR has lower levels of control overhead than FSR and achieves higher levels of throughput as the density and the level of traffic in the network is increased. I. INTRODUCTION Mobile Ad Hoc Networks (MANETs), are made up of a number of nodes, which are capable of performing routing without using a dedicated centralised controller or a base sta- tion. This key feature of these networks enable them to be em- ployed in places where an infrastructure is not available, such as in disaster relief and on battle grounds. However, the dy- namic nature of these networks and the scarcity of bandwidth in the wireless medium, along with the limited power in mo- bile devices (such as PDA's or laptops) makes routing in these networks a challenging task. A Routing protocols designed for MANETs must work consistently as the size and the density of the network varies and efficiently use the network resources to provide each user with the required levels of quality of service for different types of applications used. With so many variables to consider in order to design an efficient routing protocol for MANETs, a number of differ- ent types of routing strategies have been proposed by various authors. These protocols can be classified into three groups; global/proactive, on-demand/reactive and hybrid. Most proac- tive routing protocols are based on the link state and distance vector algorithms. In these protocols, each node maintains up- to-date routing information to every other node in the network by periodically exchanging distance vector or link state infor- mation using different updating strategies (discussed in the fol- lowing section). In on-demand routing protocols each node only maintains active routes. That is, when a node requires a route to a par- ticular destination, a route discovery is initiated. The route de- termined in the route discovery phase is maintained while the route is still active (i.e. the source has data to send to the desti- nation). The advantage of on-demand protocols is that they re- duce the amount of bandwidth usage and redundancy by deter- mining and maintaining routes when they are required. These

/pdf/displacement-based-route-update-strategies-for-proactive-1et90qokjk.pdf

Mehran Abolhasan

Papers

An energy-efficient adaptive clustering algorithm for wireless sensor networks

Including general environmental effects in K -factor approximation for rice-distributed VANET channels

OLSR-R 3 : Optimised link state routing with reactive route recovery

A new strategy to improve proactive route updates in mobile ad hoc networks

Displacement-based Route Update Strategies for Proactive Routing Protocols in Mobile Ad Hoc Networks