In beyond fifth-generation (B5G) applications, the effective wireless connectivity is not only requisite for the data transmission between multiple nodes, but also represents a key factor to ensure the safety of personnel or citizens in remote locations, especially in cases with environmental hazards or in emergency situations. However, a huge number of base stations is indispensable for global radio coverage. In addition, the terrestrial communication infrastructure is sensitive to natural disasters, e.g., earthquakes and floods. To further extend the wireless connectivity into remote and inaccessible areas and also enhance the reliability and resiliency of services, the non-terrestrial communications infrastructure should be leveraged. The non-terrestrial networks (NTNs) are capable of simultaneously interconnecting a massive number of devices that struggle for connectivity, while ensuring the successful management of data-intensive applications, redundant connections at critical sites, low latency, and enhanced capacity. In addition, NTNs can ensure the delivery of wireless services in challenging environments with highly mobile and dispersed nodes by exploiting network segments in space, air, and ground.

Aerial Communications

Beyond satellites, NTNs indicate networks or segments of networks with high- and low-altitude platforms (HAPs/LAPs) or airborne vehicles acting as aerial transceivers that operate at altitudes ranging between 8 and 50km above ground level. The term HAP defines both aircrafts flying in a roughly circular tight path in the stratosphere layer and quasi-stationary, solar-powered, non-pollutant, and environmentally friendly airships. Besides, LAPs fly at lower altitudes, in the troposphere, and intend to accomplish diverse missions. Among them, unmanned aerial vehicles (UAVs) constitute a type of small fueled aircraft employed for short time periods and allow for a rapid relay-based deployment of a multi-hop communication backbone. Indicative types of UAVs are drones, remotely piloted vehicles (RPVs), pilotless aircrafts, and robot planes. Since the links of terrestrial systems are often blocked, aerial platforms have great potential to attain a higher chance of line-of-sight (LoS) communication with the ground users and thus enhance the coverage and connectivity. B5G and Internet of Things (IoT) systems are expected to include aerial platforms as autonomous communicating nodes or aerial relays for attaining highly reliable connections between sensors and data collection points at high elevation angles and across urban, suburban, and rural terrains. Both HAPs and LAPs can be rapidly deployed and moved on-demand and can also carry a range of sensors, including geospatial sensor technologies gathering massive amounts of valuable data.

Aerial Platforms and Aerial Vehicles

Our research is focused on the analysis and design of new techniques for aerial communications across different network layers for enabling the B5G vision in many practical scenarios and in an energy-efficient, and secure manner. More specifically, we deal with the following fields of research for aerial communications:

• Channel modeling and statistical characterization of air-to-air (A2A) and air-to-ground (A2G) channels
• Development of aerial channel simulators
• Wireless communication technologies, e.g., mmWave, massive multiple input multiple output (MIMO), non-orthogonal multiple access (NOMA), free-space optical (FSO)
• Mobile Edge Computing (MEC)-enabled aerial network architectures
• Energy harvesting and wireless-powered communications
• Reconfigurable Intelligent Surface (RIS)-enabled aerial networks
• Software-defined radio (SDR), software-defined networking (SDN), and network function virtualization (NFV)
• Machine learning (ML) techniques for optimized performance of aerial networks
• Measurements and experimental demonstration for the A2G and A2A channels in various propagation environments
• Development of software-based and hardware-based security solutions for aerial networks