Aerospace and Electronic Systems Magazine August 2016 - 4

Feature Article: DOI. No. 10.1109/MAES.2016.150170 Cellular for the Skies: Exploiting Mobile Network Infrastructure for Low Altitude Air-to-Ground Communications Luis Afonso, Nuno Souto, Pedro Sebastião, Marco Ribeiro, Tiago Tavares, Rui Marinheiro, University Institute of Lisbon, and the Instituto de Telecomunicações, Lisbon, Portugal INTRODUCTION Although the concept was born within military use, in recent years we have witnessed an impressive development of unmanned aerial vehicles (UAVs) for civil and academic applications. Driving this growth is the myriad of possible scenarios where this technology can be deployed, such as: fire detection, search and rescue operations, surveillance, police operations, building and engineering inspections, aerial photography and video for post-disaster assessment, agricultural monitoring, remote detection (radiation, chemical, electromagnetic), weather services, UAV photogrammetry, airborne relay networks, and more [1]. Undoubtedly, the increased use of UAVs has been sustained through the research and development of multiple low-cost solutions for the control of aerial vehicles, the evolution in microelectronics with multiple off-the-shelf components and sensors, and also through a growing global developers community with several UAV related open source projects. The safe operation of a UAV requires a communication link to deliver telemetry data, control commands, and other information between the vehicle and a ground control station (GCS). Different solutions have been studied and implemented, as discussed in [2], but most suffer from either a restricted operational range or a high implementation complexity. A potential alternative to overcome the range limitation with reduced complexity, which has not been adequately studied so far, is to use existing wide coverage mobile radio infrastructures, such as General Packet Radio Service/Enhanced Data rates for Global Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), and LTE-Advanced (LTE-A). In this article, we discuss the viability of Authors' address: L. Afonso, N. Souto, P. Sebastião, M. Ribeiro, T. Tavares, R. Marinheiro, ISCTE-University Institute of Lisbon, and the Instituto de Telecomunicações, Portugal, Av. Rovisco Pais, 1, Lisbon, 1049 - 001 Portugal, E-mail: (nuno.souto@lx.it. pt). Manuscript received August 7, 2015, revised December 15, 2015, and ready for publication February 16, 2016. Review handled by D. Ciuonzo. 0085/8985/16/$26.00 © 2016 IEEE 4 this approach. Based on our own experimental studies, performed within the scope of the Portuguese Remotely Piloted Semi-Autonomous Aerial Surveillance System Using Terrestrial Wireless Networks (SAAS) research project, we will focus on the advantages of using cellular networks as well as on the problems that can arise and possible solutions to deal with them. We present a flexible architecture for a multi-UAV, multi-operator system which can make use of third and fourth generation (3G/4G) wireless networks, and describe some results obtained from experimental tests using our unmanned aerial system (UAS) implementation. Finally, we comment on potential improvements that can be expected from future cellular networks in this context. UNMANNED AERIAL SYSTEMS In general, a UAS consists of the vehicle, known as an UAV, and the mechanisms, logistics, and equipment regarding its proper operation. UAVs can be grouped into different categories according to their size [3], with the micro aerial vehicle (MAV), which typically weighs less than 2 kg and operates at low altitudes, being the most appellative for civil use. Several companies and academic groups have developed proprietary and open source hardware/ firmware/software for UASs. The hardware includes the vehicle, flight avionics (which includes the flight controller), and the wireless communication subsystem. The firmware running on the flight controller is responsible for the stabilization of the vehicle, geolocation, and preprogramed waypoint navigation. Additional software is often provided for implementation of GCS functions namely, mission planning, monitoring, and control. A ground operator can use the GCS application to communicate with the flight controller platform using a bidirectional link. The most popular open source flight controller is the Ardupilot Mega (APM),1 although several other well-known platforms exist, such as Pixhawk,2 OpenPilot,3 and Paparazzi.4 A detailed comparison of different open source projects is provided in [4]. While most of these flight controllers are intended for multi-rotors, some also Ardupilot Mega, Multiplatform Autopilot. [Online]. http://ardupilot. com/. 2 Pixhawk Autopilot. [Online]. https://pixhawk.org. 3 Openpilot. [Online]. http://www.openpilot.org/. 4 Paparazzi Project. [Online]. http://wiki.paparazziuav.org/. 1 IEEE A&E SYSTEMS MAGAZINE AUGUST 2016 http://ardupilot.com/ http://ardupilot.com/ https://www.pixhawk.org http://www.openpilot.org/ http://wiki.paparazziuav.org/

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine August 2016