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 analyze the error performance of a cooperative multihop parallel relay network over Nakagami-m fading channels using M-ary Phase-shift keying (MPSK) modulation. We derive the general closed form expression of the symbol error probability (SEP) and present numerical results on the performance of the network.

SEP of Multihop Relay Networks in Nakagami-m Fading Channels

In this paper, we propose three algorithms for placement of access points (APs) for the purpose of data transportation via train-to-wayside (T2W) communications along a rail network. The first algorithm is proposed to find the minimum number of APs so that the path-loss (PL) does not exceed a desired threshold. Through the second algorithm, the most optimal places for a desired number of APs are determined so that the average PL is minimum. The goal of the third algorithm is to determine the required number and optimal places of APs in a rail network. Furthermore, we propose a model to consider the effects of changes of communication characteristics on the efficiency of the network in different environments. Through such model, the algorithms proposed for placement of APs can be used in different railway scenarios. The proposed algorithms are validated through extensive simulations in Sydney Trains of Australia. The simulation results show that the proposed approach can improve the efficiency of the system at least 21% and up to 165% within 10 different scenarios. We also show that we can approximately transmit over 250 Gigabit data through T2W communications over common WiFi networks.

A Comprehensive Access Point Placement for IoT Data Transmission Through Train-Wayside Communications in Multi-Environment Based Rail Networks

Controlling water salinity plays a key role in farming efficiency. Current sensors are mostly expensive and need regular maintenance. In addition, they require electrical connections or extra power supply that leads to difficult and costly implementation in remote sensing scenarios. In this paper, an accurate and low-profile sensor is developed using a metamaterial perfect absorber (MPA) structure. The proposed sensor works based on the level and frequency of absorbed signals. Hence, there is no need for electrical connections, which enables remote sensing applications. Square shape channels have been created in a regular FR-4 substrate to facilitate sensing of water salinity level. A 7×7 array with a total size of 140mm×160mm has been fabricated that shows a resolution of 10 MHz per percentage of water salinity. The absorption frequency shifts from f=3.12 GHz to f=3.59 GHz for salinity level from 0% to 50%. A strong correlation between measurement and simulation results validates the design procedure.

Remote Water Salinity Sensor Using Metamaterial Perfect Absorber

Wireless Body Area Networks (WBANs) were designed to collect and transfer vital physiological parameters within a short distance of the human body by employing low-power, light-weight, small-sized and smart implantable or wearable sensor devices. Lately, WBANs are expected to support various types of applications with data rates from a few Kbps upto 10 Mbps and satisfy the heterogeneous requirements of both medical and consumer electronics applications. Hence, novel communication protocols that consider a unique set of constraints and demands of these networks need to be developed to provide optimum system efficiency and data transmission reliability. As the IEEE 802.15.6 Medium Access Control (MAC) protocol based on the latest WBANs standard, cannot maintain the balance between the strict energy limitation and Quality of Service (QoS) requirements of such networks, this paper focuses on developing MAC protocols to improve the performance of WBANs specifically in the saturation condition. Two IEEE802.15.6-based MAC protocols are proposed to enhance channel access for the highest user priority and the other user priorities in saturated networks. The simulation results show better network performance as well as lower energy consumption in the proposed MAC protocols compared to the IEEE 802.15.6 MAC protocol.

On improving the saturation performance of IEEE802.15.6-based MAC protocols in Wireless Body Area Networks

The paper presents a new scheme of concatenated codes, referred to as Serially Concatenated Turbo (SCT) codes. The code is constructed as the serial combinations of two turbo codes, i.e. turbo Recursive Systematic Convolutional (RSC) codes and turbo Bose Ray Chaudhuri Hocquenghem (BCH) codes, linked by a pseudo-random interleaver. In comparison with the conventional turbo RSC codes, SCT codes have higher minimum distance values. Based on conducted simulations, it is found that SCT codes outperform turbo RSC codes at the waterfall and error floor regions, while they require reasonable number of iterations at their iterative decoding structure to achieve good performance.

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Mehran Abolhasan

Papers

SEP of Multihop Relay Networks in Nakagami-m Fading Channels

A Comprehensive Access Point Placement for IoT Data Transmission Through Train-Wayside Communications in Multi-Environment Based Rail Networks

Remote Water Salinity Sensor Using Metamaterial Perfect Absorber

On improving the saturation performance of IEEE802.15.6-based MAC protocols in Wireless Body Area Networks

Serially Concatenated Turbo Codes