In recent years, there has been a dramatic increase in the use of unmanned aerial vehicles (UAVs), particularly for small UAVs, due to their affordable prices, wide availability, and relative ease of operability. Existing and future applications of UAVs include remote surveillance and monitoring, relief operations, package delivery, and communication backhaul infrastructure. Additionally, UAVs are envisioned as an important component of 5G wireless technology and beyond. The unique application scenarios for UAVs necessitate accurate air-to-ground (AG) propagation channel models for designing and evaluating UAV communication links for control/non-payload as well as payload data transmissions. These AG propagation models have not been investigated in detail, relative to terrestrial propagation models. In this paper, a comprehensive survey is provided on available AG channel measurement campaigns, large and small scale fading channel models, their limitations, and future research directions for UAV communication scenarios.

A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles

Important requirements for automotive radar are high resolution, low hardware cost, and small size. Multiple-input, multiple-output (MIMO) radar technology has been receiving considerable attention from automotive radar manufacturers because it can achieve a high angular resolution with relatively small numbers of antennas. For that ability, it has been exploited in the current-generation automotive radar for advanced driverassistance systems (ADAS) as well as in next-generation highresolution imaging radar for autonomous driving. This article reviews MIMO radar basics, highlighting the features that make this technology a good fit for automotive radar and reviewing important theoretical results for increasing the angular resolution. The article also describes challenges arising during the application of existing MIMO radar theory to automotive radar that provide interesting problems for signal processing researchers.

MIMO Radar for Advanced Driver-Assistance Systems and Autonomous Driving: Advantages and Challenges

Unmanned aerial vehicles (UAVs) have stroke great interested both by the academic community and the industrial community due to their diverse military applications and civilian applications. Furthermore, UAVs are also envisioned to be part of future airspace traffic. The application functions delivery relies on information exchange among UAVs as well as between UAVs and ground stations (GSs), which further closely depends on aeronautical channels. However, there is a paucity of comprehensive surveys on aeronautical channel modeling in line with the specific aeronautical characteristics and scenarios. To fill this gap, this paper focuses on reviewing the air-to-ground (A2G), ground-to-ground (G2G), and air-to-air (A2A) channel measurements and modeling for UAV communications and aeronautical communications under various scenarios. We also provide the design guideline for managing the link budget of UAV communications taking account of link losses and channel fading effects. Moreover, we also analyze the receive/transmit diversity gain and spatial multiplexing gain achieved by multiple-antenna-aided UAV communications. Finally, we discuss the remaining challenge and open issues for the future development of UAV communication channel modeling.

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A Comprehensive Survey on UAV Communication Channel Modeling

The present invention provides systems and methods for improved data communication between communication terminals such as a base station and an unmanned aerial vehicle. In some instances, the systems and methods described herein provide robust transmission uplink data such as control data and wideband transmission of downlink data such as image data or other sensor data, while avoiding interference between the uplink data transmission and the downlink transmission.

Data communication systems and methods

The advances in photonic device technologies are bringing ultra-high-bit-rate networking-at speeds towards 100 Gb/s and beyond-much closer to practical reality. It is increasingly likely that in the longer term ultrafast optical time-division techniques-together with wavelength multiplexing-will be used in networks at all levels, from the transcontinental backbone to the desktop. Examples of devices include a subpicosecond clock source packaged inside a laptop personal computer and an OTDM switch on a single semiconductor chip, both produced at HHI. Advances similar to these make it possible now to envisage the use of OTDM techniques, not just in the highest layers of national and international networks, but also much closer to the user-such as the world-first demonstrations at BT Laboratories of a 40 Gb/s TDMA LAN and a 100 Gb/s packet self-routing switch for multiprocessor interconnection. Ultrafast networks might even provide the interconnection backplane inside future desktop routers and servers with massive throughput.

Ultra-high-bit-rate networking : From the transcontinental backbone to the desktop : Optical networks technology in Europe

Multiple-input multiple-output (MIMO) radars have been shown to improve target detection for surveillance applications thanks to their proven high-performance properties. In this paper, the design, implementation, and results of a complete 3-D imaging frequency-modulated continuous-wave MIMO radar demonstrator are presented. The radar sensor working frequency range spans between 16 and 17 GHz, and the proposed solution is based on a 24-transmitter and 24-receiver MIMO radar architecture, implemented by time-division multiplexing of the transmit signals. A modular approach based on conventional low-cost printed circuit boards is used for the transmit and receive systems. Using digital beamforming algorithms and radar processing techniques on the received signals, a high-resolution 3-D sensing of the range, azimuth, and elevation can be calculated. With the current antenna configuration, an angular resolution of 2.9° can be reached. Furthermore, by taking advantage of the 1-GHz bandwidth of the system, a range resolution of 0.5 m is achieved. The radio-frequency front-end, digital system and radar signal processing units are here presented. The medium-range surveillance potential and the high-resolution capabilities of the MIMO radar are proved with results in the form of radar images captured from the field measurements.

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A Portable 3-D Imaging FMCW MIMO Radar Demonstrator With a $24\times 24$ Antenna Array for Medium-Range Applications

In the course of a national research project, EADS Innovation Works has developed a waveform on a self-designed hybrid Software Defined Radio (SDR) platform, consisting of an FPGA (Xilinx Virtex 5) and a GPP (Intel Atom). The waveform realizes a video link between an Unmanned Ground Vehicle (UGV) and its Ground Control Station (GCS). This link is established indirectly with an Unmanned Aerial Vehicle (UAV) acting as a relay, in order to enable non-line-of-sight (NLOS) communication and to increase the communication range. Additionally, a direct video link from the UAV to the GCS is set up simultaneously as well as multiple low data rate control channels between the individual link partners. To cope with diverse operation areas, accompanied by a heterogeneous set of requirements, the waveform must offer outstanding adaptability and flexibility to maximize data rates in each scenario, while maintaining link robustness. The developed waveform is based on OFDM with freely customizable modulation parameters. Time Division Multiple Access (TDMA) is implemented on medium access layer to switch between the different users in the scenario (UGV, UAV, GCS). In this article, we give an overview of the waveform, its implementation on a hybrid platform and its validation for the intended field of application.

SDR OFDM Waveform Design for a UGV/UAV Communication Scenario

Avionic networks are to an increasing extent based on Ethernet physical layer implementations due to economical and technical motivations. While conventional Ethernet-based systems are built up in star topologies, the physical layer can also be used to establish linear networks. Power-over-Ethernet (PoE) uses Ethernet data cabling for the transmission of power. Existing technology however is not able to transmit sufficient power for many avionic applications, particularly for such implemented in a linear topology. With a customized PoE approach, the power capabilities of PoE links can significantly be increased to more than 100 W. With an adequate fail-safe concept, the reliability of a linear Ethernet implementation can be increased, reducing the immanent safety drawback of a linear topology. The presented methods offer the potential to significantly reduce cost, complexity and weight of Ethernet-based system installations, aiming at greener avionics for future aircraft.

Power-over-Ethernet for avionic networks

The aeronautic industry and its suppliers show increasing interest in utilizing the automotive FlexRay protocol for their applications, more than ever since an opening of the standard for all industries and field of applications becomes apparent. With its combination of deterministic and flexible c o m m u n ication and data rates up to 10 Mbit/s on a single twisted wire pair, FlexRay is a promising candidate for future system developments and the modernization of CAN based systems. Currently, the performance of the protocol is rather unknown i n a n aeronautic environment, in particular with respect to its physical layer. This paper analyzes the signal decoding process of FlexRay and derives dedicated signal integrity criteria for the protocol. An efficient method based on the transmission and evaluation of worst-case bit patterns is developed for the assessment of signal integrity on demanding topologies with significant attenuation and resulting inter-symbol interferences. RS485 is discussed as a possible alternative physical layer for the FlexRay protocol to improve the communication performance. Finally, a use-case topology with a harness length of 90 m is presented to evaluate the achievable performance when utilizing the FlexRay protocol. Signal integrity is demonstrated and validated on the topology at a data rate of 10 Mbit/s to prove the suitability of FlexRay for aeronautic applications.

Enabling FlexRay for avionic data buses

This paper reports experimental results comparing the performance of four platforms employed in spectrum sensing and dynamic spectrum access research: a sensing engine developed at imec and built around a prototype RFIC; the Universal Software Radio Peripheral (USRP) with the Iris software defined radio (SDR) solution; the TelosB sensor network platform; and the Wi-Spy low cost spectrum sensor solution targeted at the ISM band. We use experimental data to derive the receiver operating characteristics (ROC) of each of the four platforms. We observe that for low signal powers, narrow bandwidth signals, high shadowing, or stringent probability of false alarm (PFA) requirements tradeoffs among the platforms tested are most pronounced, whereas for high signal powers, large bandwidths, stable environments, and more flexible PFA requirements less expensive, commercial-off-the-shelf equipment performs sufficiently well.

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Christoph Heller

Papers

A Portable 3-D Imaging FMCW MIMO Radar Demonstrator With a $24\times 24$ Antenna Array for Medium-Range Applications

SDR OFDM Waveform Design for a UGV/UAV Communication Scenario

Power-over-Ethernet for avionic networks

Enabling FlexRay for avionic data buses

Experimental assessment of tradeoffs among spectrumsensing platforms