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Autonomous robotic swarms are envisioned for a variety of sensing applications in space exploration, search and rescue, and disaster management. An important capability of a swarm is sensing spatio-temporal processes such as radio wave propagation and seismic activities. The spa-tio-temporal properties of these processes dictate the required sensing position and time accuracy, as well as update rate. A dedicated wireless communication system needs to be jointly designed for swarm information exchange, self-localization, and sensing. In this article, we emphasize the role of time in a robotic swarm. We introduce the system ingredients and dive into realistic clock models. Clock models and channel access schemes decisively influence the swarm self-localization and synchronization accuracy, and consequently the swarm sensing performance. Finally, we discuss practical implementation aspects, introduce our developed swarm radio system, and give an outlook on a moon-analog exploration mission. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles, also known as drones, are expected to play major roles in future smart cities, for example, by delivering goods and merchandise, serving as mobile hotspots for broadband wireless access, and maintaining surveillance and security. The goal of this survey article is to study various potential cyber and physical threats that may arise from the use of UAVs, and subsequently review various ways to detect, track, and interdict malicious drones. In particular, we review techniques that rely on ambient radio frequency signals (emitted from UAVs), radars, acoustic sensors, and computer vision techniques for detection of malicious UAVs. We present some early experimental and simulation results on range estimation of UAVs and receding horizon tracking of UAVs. Finally, we summarize common techniques that are considered for interdiction of UAVs. [ABSTRACT FROM AUTHOR]

Meeting the diverse delay requirements of emerging wireless applications is one of the most critical goals for the design of ultra-dense networks. Although the delay of point-to-point communications has been well investigated using classical queueing theory, the delay of multipoint- to-multipoint communications, such as in ultra-dense networks, has not been explored in depth. The main technical difficulty lies in the interacting queues problem, in which the service rate is coupled with the statuses of other queues. In this article, we elaborate on the main challenges in the delay analysis in ultra-dense networks. Several promising approaches, such as introducing the dominant system and the simplified system, to bypass these difficulties are proposed and summarized to provide useful guidance. [ABSTRACT FROM PUBLISHER]

The article discusses the history of Radio Wave Propagation in wireless communications. It discusses the experiments and theories of Guglielmo Marconi, an Italian inventor known for his pioneering work on long-distance radio transmission. Also discusses the high frequency propagation through ionosphere at global communications for thousands of kilometers, also includes MIMO (multiple input, multiple output), an antenna technology for wireless communications which increases spectral efficiency.

Beyond-5G and 6G networks aim at providing flexible compute and connect technologies, which may support innovative use cases and unprecedented services by means of a concrete and sustainable transformation of existing network designs into smart-connected telecommunication infrastructures. Such a revolution might include full control of the propagation environment, which is a weak point of legacy communication solutions, that can be empowered by the adoption of a novel technology, namely Reconfigurable Intelligent Surfaces, which are man-made passive surfaces comprising up to thousands of reconfigurable unit elements. The novel approach of modifying the radio wave propagation can bring extraordinary benefits to how we conceive the wireless connectivity paradigm. This Feature Topic (FT) deeply investigates the taxonomy of such envisioned services, the feasibility of advanced use-cases, as well as specific architectural, protocol and system requirements to build RIS-based networks. [ABSTRACT FROM AUTHOR]

Over the past five years, coherent transmission technologies have delivered more than an order of magnitude improvement in the capacity- reach product for long-haul DWDM transmission systems. This article provides a working definition of "coherent transmission" based on current market realities; provides a functional model for beyond 100G coherent systems, and then examines five key technologies that will deliver beyond 100G: evolving transmitter technologies, including Nyquist pulse shaping and nonlinear compensation of transmitter devices; nonlinear compensation for the propagation effect; further advances in FEC technology; flexible grid DWDM and coherent super-channels. In each case we explain the factors in terms of optical or electronic component performance that are most likely to result in system performance limitations, and discuss engineering strategies to mitigate those limitations. [ABSTRACT FROM AUTHOR]

Optimizing the cellular network?s cell locations is one of the most fundamental problems of network design. The general objective is to provide the desired QoS with the minimum system cost. In order to meet a growing appetite for mobile data services, heterogeneous networks have been proposed as a cost- and energyefficient method of improving local spectral efficiency. While unarticulated cell deployments can lead to localized improvements, there is a significant risk posed to network-wide performance due to the additional interference. The first part of the article focuses on state-of-the-art modelling and radio planning methods based on stochastic geometry and Monte Carlo simulations, and the emerging automatic deployment prediction technique for low-power nodes, or LPNs, in heterogeneous networks. The technique advises an LPN where it should be deployed, given certain knowledge of the network. The second part of the article focuses on algorithms that utilize interference and physical environment knowledge to assist LPN deployment. The proposed techniques can not only improve network performance, but also reduce radio planning complexity, capital expenditure, and energy consumption of the cellular network. The theoretical work is supported by numerical results from system-level simulations that employ real cellular network data and physical environments. [ABSTRACT FROM PUBLISHER]

Uncompressed high-definition video streaming over wireless personal area networks is a challenging problem because of the high data rate requirement and channel variations. With the advances in RF technology and the huge bandwidth available worldwide in the 57-66 GHz millimeter-wave unlicensed spectrum, mmWave WPANs that can support multigigabit transmission are being developed. However, compared to low-frequency signals (2.4 or 5 GHz), mmWave signals are more fragile; indeed, the propagation losses are significantly higher. In this article we present an mmWave system for supporting uncompressed HD video up to 3 Gb/s. The system includes various efficient error protection and concealment schemes that exploit unequal error resilience properties of uncompressed video. Some of them have been adopted in the emerging 60 GHz WPAN standards such as WirelessHD, ECMA TC48, and IEEE 802.15.3c. Simulations using real uncompressed HD images indicate that the proposed mmWave system can maintain, under poor channel conditions, good average peak-signal-to-noise-ratio and low video quality metric scores. [ABSTRACT FROM AUTHOR]

This article analyzes the wireless coverage problem of remote regions with low user density and propagation problems due to irregular terrain and high tree density. The use of a wireless mesh network is proposed as a solution where user data is transmitted directly to a base station when it is possible or relayed through other nodes in a multi-hop manner when there is not a direct link. The mesh topology uses short links with higher capacity instead of long links with low capacity. We analyze radio propagation and MAC protocols, including random sources, queues, and packet delays. The article is based on the coverage of a realistic rural region near Medellin, a mid size city in Colombia, and it shows that a wireless mesh network is an alternative to a typical cell based solution. It includes propagation analysis and MAC protocol behavior, so it is not limited to a radio coverage problem but also traffic, scheduling, and routing analysis. [ABSTRACT FROM AUTHOR]

Wireless solutions are rapidly growing in machine-to-machine communications in industrial environments. These environments provide challenging conditions in terms of radio wave propagation as well as electromagnetic interference. In this article, results from the characterization of radio channel properties are summarized in order to provide some guidelines for the choice of wireless solutions in industrial environments. In conclusion, it is essential to know the sensitivity of industrial processes to time delay in data transfer. Furthermore, it is important to be aware of the radio interference environment and the manner in which different wireless technologies react upon interference. These steps will minimize the risk of unforeseen expensive disturbances in industrial processes. [ABSTRACT FROM PUBLISHER]

In this article, we aim to evaluate the influences of different propagation models on the results of V2X simulations. First, we analyze how the models free space propagation, Rayleigh fading, and Ricean fading in synthetic scenarios with and without background communication influence the simulation of communication in general. After that, we investigate the impact of the models on the simulated behavior of a V2X traffic efficiency application in a real inner city scenario. Our results show that the selection of the propagation model affects the number of delivered messages, but exerts no significant influence on the simulated effectiveness of a V2X traffic efficiency application in urban areas. Under those circumstances, a simplified propagation model is sufficient. [ABSTRACT FROM PUBLISHER]