The use of unmanned aerial vehicles (UAVs) is growing rapidly across many civil application domains, including real-time monitoring, providing wireless coverage, remote sensing, search and rescue, delivery of goods, security and surveillance, precision agriculture, and civil infrastructure inspection. Smart UAVs are the next big revolution in the UAV technology promising to provide new opportunities in different applications, especially in civil infrastructure in terms of reduced risks and lower cost. Civil infrastructure is expected to dominate more than $45 Billion market value of UAV usage. In this paper, we present UAV civil applications and their challenges. We also discuss the current research trends and provide future insights for potential UAV uses. Furthermore, we present the key challenges for UAV civil applications, including charging challenges, collision avoidance and swarming challenges, and networking and security-related challenges. Based on our review of the recent literature, we discuss open research challenges and draw high-level insights on how these challenges might be approached.

Unmanned Aerial Vehicles: A Survey on Civil Applications and Key Research Challenges

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

Local positioning will be one of the most exciting features of the next generation of wireless systems. Completely new concepts and features for wireless data transmission and transponder systems will emerge. Self-organizing sensor networks, ubiquitous computing, location sensitive billing, context dependent information services, tracking and guiding are only some of the numerous possible application areas. This article introduces different concepts of several existing and emerging systems and applications.

Wireless local positioning

As the rapid development of automotive telematics, modern vehicles are expected to be connected through heterogeneous radio access technologies and are able to exchange massive information with their surrounding environment. By significantly expanding the network scale and conducting both real time and long term information processing, the traditional Vehicular Ad- Hoc Networks U+0028 VANETs U+0029 are evolving to the Internet of Vehicles U+0028 IoV U+0029, which promises efficient and intelligent prospect for the future transportation system. On the other hand, vehicles are not only consuming but also generating a huge amount and enormous types of data, which are referred to as Big Data. In this article, we first investigate the relationship between IoV and big data in vehicular environment, mainly on how IoV supports the transmission, storage, computing of the big data, and in return how IoV benefits from big data in terms of IoV characterization, performance evaluation and big data assisted communication protocol design. We then investigate the application of IoV big data for autonomous vehicles. Finally the emerging issues of the big data enabled IoV are discussed.

Internet of vehicles in big data era

The demand for high-capacity wireless services is bringing increasing challenges, especially for delivery of the “last mile”. Terrestrially, the need for line-of-sight propagation paths represents a constraint unless very large numbers of base-station masts are deployed, while satellite systems have capacity limitations. An emerging solution is offered by high-altitude platforms (HAPs) operating in the stratosphere at altitudes of up to 22 km to provide communication facilities that can exploit the best features of both terrestrial and satellite schemes. This paper outlines the application and features of HAPs, and some specific development programmes. Particular consideration is given to the use of HAPs for delivery of future broadband wireless communications.

High-altitude platforms for wireless communications

The aim of this book is to present the modern design principles and analysis of lens antennas. It gives graduates and RF/ Microwave professionals the design insights in order to make full use of lens antennas. Why do we want to write a book in lens antennas? Because this topic has not been thoroughly publicized, its importance is underestimated. As antennas play a key role in communication systems, recent development in wireless communications would indeed benefit from the characteristics of lens antennas: low profile, and low cost etc.

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Modern lens antennas for communications engineering

In the present climate of growth in bandwidth-hungry telecommunication applications, wireless infrastructure providers are under continuous pressure to exploit the limited radio spectrum as efficiently as possible. In this context, high-altitude platforms (HAPs) are increasingly being cited as having an important role to play in future systems and applications. They have the potential to exploit many of the best aspects of terrestrial and satellite-based systems, while offering advantageous propagation characteristics. Such platforms may be airships or aircraft and for environmental considerations would ideally be solar powered. This paper reviews some of the studies under the European HeliNet programme-a consortium-led project to develop a pilotless solar-powered aircraft from which broadband communication services could be supported. Millimetre wave antennas and propagation characteristics are discussed in particular.

Broadband communications from a high-altitude platform: the European HeliNet programme

In a wireless communications network served by a high altitude platform (HAP) the cochannel interference is a function of the antenna beamwidth, angular separation and sidelobe level. At the millimeter wave frequencies proposed for HAPs, an array of aperture type antennas on the platform is a practicable solution for serving the cells. We present a method for predicting cochannel interference based on curve-fit approximations for radiation patterns of elliptic beams which illuminate cell edges with optimum power, and a means of estimating optimum beamwidths for each cell of a regular hexagonal layout. The method is then applied to a 121 cell architecture. Where sidelobes are modeled as a flat floor at 40-dB below peak directivity, a cell cluster size of four yields carrier-to-interference ratios (CIRs), which vary from 15 dB at cell edges to 27 dB at cell centers. On adopting a cluster size of seven, these figures increase, respectively, to 19 and 30 dB. On reducing the sidelobe level, the improvement in CIR can be quantified. The method also readily allows for regions of overlapping channel coverage to be shown.

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Optimizing an array of antennas for cellular coverage from a high altitude platform

A method of significantly improving the capacity of high-altitude platform (HAP) communications networks operating in the millimeter-wave bands is presented. It is shown how constellations of HAPs can share a common frequency allocation by exploiting the directionality of the user antenna. The system capacity of such constellations is critically affected by the minimum angular separation of the HAPs and the sidelobe level of the user antenna. For typical antenna beamwidths of approximately 5/spl deg/ an inter-HAP spacing of 4 km is sufficient to deliver optimum performance. The aggregate bandwidth efficiency is evaluated, both theoretically using the Shannon equation, and using practical modulation and coding schemes, for multiple HAP configurations delivering either single or multiple cells. For the user antenna beamwidths used, it is shown that capacity increases are commensurate with the increase in the number of platforms, up to 10 HAPs. For increases beyond this the choice of constellation strategy becomes increasingly important.

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Improving the system capacity of broadband services using multiple high-altitude platforms

Spherical lens antennas can produce multiple beams from multiple feeds, and these may be scanned to any angle. While an electrically large, uniform dielectric sphere offers mediocre aperture efficiency, this can be usefully increased by varying the dielectric constant with radius, as in the Luneburg lens. A continuous radial variation is difficult to achieve in practice and so a series of concentric shells is often preferred. A useful variant is that of the hemisphere lens used with a ground plane: this offers a relatively low-profile solution which is advantageous for a vehicle-mounted scanning antenna. A theory for the hemisphere lens radiation pattern is developed where this is described as the superposition of two spherical lens patterns i.e. that of the real and virtual sources. Measured radiation patterns of such lens antennas are reported which validate this theory. A prototype lens antenna is then reported which uses only two layers of dielectric material, which presents significant fabrication cost savings compared to a traditional Luneburg antenna. This 236 mm diameter lens offers 35.1 dBi of gain at 28 GHz (68% aperture efficiency) while scanning over a 150° solid angle.

J. Thornton

Papers

Modern lens antennas for communications engineering

Broadband communications from a high-altitude platform: the European HeliNet programme

Optimizing an array of antennas for cellular coverage from a high altitude platform

Improving the system capacity of broadband services using multiple high-altitude platforms

Wide-scanning multi-layer hemisphere lens antenna for Ka band