The review [6] is devoted to the history of HAPs and the current state of affairs without taking into account the aspects of the telecommunications sphere, which are among the main in this issue.
Airborne Communications Networks (ACNs) have received great attention as heterogeneous networks designed to use satellites, HAPs, and Low-Altitude Platforms (LAPs) as communication access. ACNs, unlike terrestrial wireless networks, are characterized by changing network topology and more vulnerable communication links. The review [7] covers communication networks based on LAPs, HAPs and integrated networks ACNs.
RPASs will become a component of 5G communication systems (and not only) to achieve global access to the Internet for everyone. The paper [8] proposes a new hierarchical network architecture that integrates inter-layer platforms for high and low altitudes into conventional terrestrial cellular networks. This provides additional bandwidth and expands coverage of underserved areas. Comparison and overview of various RPASs types for the provision of communication services are presented in the paper. An integrated architecture of an air-heterogeneous network is proposed and its characteristics are described.
RPASs need to effectively interact with each other and using the existing network infrastructure. The requirement for reliable communication is caused by errors in navigation, guidance and control systems that are introduced at each stage. Navigation systems introduce errors in the determination of the current coordinates and orientation parameters [9], and the guidance and control system may have corresponding deficiencies when a single drone is set to the required position [10].
RPASs deployment is seen as an alternative complement to existing cellular communications to achieve higher transmission efficiency with increased coverage and capacity. The article [11] provides an overview of advances in integrating 5G communications into wireless networks supported by RPASs. A taxonomy is given to classify existing research problems. Based on the proposed taxonomy, current issues and solutions for this newly emerging area are discussed.
The study [3] provides an overview of HAPS wireless service delivery in rural or remote areas using the cellular radio spectrum and focuses on the potential of using HAPS as an alternative to terrestrial systems. The feasibility of expanding the achievable wireless coverage using HAPS was investigated. This takes into account the coexistence of HAPS with terrestrial systems using intelligent techniques to dynamically manage radio resources and mitigate interference. The study has shown that effective intelligent radio resource and topology management can reduce intersystem interference. Potential techniques for extending coverage are discussed, such as using the spatial characteristics of lattice antennas, radio environment maps and inter-device communication.
With new technologies in autonomous avionics, antenna arrays, solar panel efficiency and battery energy density, HAPS has become an indispensable component of next-generation wireless networks. The review [12] presents the structures of future HAPS networks, proposes the integration of the emerging reconfigurable smart surface technology into the communication payload of HAPS systems, and discusses radio resource management in HAPS systems. The contribution of artificial intelligence to HAPS is noted, including machine learning in aspects of design, topology management, handover and resource allocation.
Terrestrial and satellite communication systems often face certain disadvantages and problems that can be solved by complementing them with HAPS systems. The article [4] considers HAPS as a base station for providing connectivity in a variety of applications. In contrast to conventional HAPS, which aims to reach a wide range of remote areas, it is expected that the next HAPS generation will have the necessary capabilities to meet the requirements for high throughput, low latency and compute resources. It focuses on the potential opportunities, target use cases, and challenges that are associated with the design and implementation of a future wireless access architecture.
In the review [13], RPAS networks are classified and the topology, control and behavior of the client server are investigated. Important aspects of self-organization and automated operations using Software-Defined Networks (SDN) are highlighted. The requirements of routing protocols for SDN networks and the need to create networks resistant to violations are discussed.
The review [14] outlines functions and requirements that are important to ensure reliable, efficient and energy efficient communications in basic UAV systems. The various UAV-to-UAV (U2U) and UAV-to-Infrastructure (U2I) network architectures and the various communication protocols that can be used at the network model layers are provided. A classification of data traffic that may be present in U2U and U2I communications is described. Various communication protocols and technologies are discussed that can be used for different channels and levels of the UAV-based network architecture. Efficient and uninterrupted communication in UAV-based networks is essential for their safe deployment and operation.
The book [15] focuses on the communication and networking aspects of UAVs and the fundamental knowledge required to conduct research in this area. The basic concepts and state of affairs in the field of UAV networks are outlined. Deployment procedures and risk analysis are discussed.
UAVs can be connected to cellular networks as a new type of user equipment, providing operators with significant revenues and guaranteeing service requirements. It is possible to upgrade UAV-based flying base stations that can move dynamically to increase coverage and spectral efficiency. Standards bodies are currently exploring the possibility of servicing commercial UAVs over cellular networks. The industry is testing prototypes of base stations and user equipment. Mathematical and algorithmic solutions for new problems arising in flying nodes in cellular networks are investigated. The article [16] provides an overview of developments that facilitate the integration of UAVs into cellular networks: types of consumer UAVs available off-the-shelf; interference problems; possible solutions for servicing aeronautical users with existing ground base stations; communication with flying repeaters and base stations created using UAVs.
The use of drone-based flying platforms is growing rapidly due to mobility, flexibility and adaptive altitude, which enables them to be used in wireless systems. UAVs can be used as aerial base stations to increase the coverage, capacity, reliability and energy efficiency of wireless networks. Drones can act as flying mobile terminals within a cellular network. These drones, connected to a cellular network, can use several applications, ranging from live video streaming to delivering goods. The article [17] provides detailed guidance on the UAVs use in wireless communications: 3D deployment, performance analysis, channel modeling and energy efficiency. Analytical foundations and mathematical tools such as optimization theory, machine learning, stochastic geometry, transport theory and game theory are described. The basic recommendations for the analysis, optimization and design of wireless communication systems based on UAVs are presented.
The main problem that needs to be solved for the successful introduction of drones in all areas is communication [18]. This review aims to outline the latest UAV communication technologies through research on suitable task modules, antennas, resource processing platforms, and network architectures. Methods such as machine learning and path planning are considered to improve existing communication methods with drones. Encryption and optimization techniques are discussed to ensure long-term and secure communications as well as power management. Applications of UAV networks are investigated for a variety of contextual purposes, from navigation to surveillance, ultra-reliable low latency communications, edge computing, and works related to artificial intelligence. The complex interaction between UAVs, advanced cellular communications and the Internet of things are the main topics of this article.
The best example of high-altitude RPAS with multisensory synthesis technology is the Global Hawk [19], which is equipped with an integrated surveillance and reconnaissance system HISAR (Hughes Integrated Surveillance & Reconnaissance). Such devices belong to the class HALE (High-Altitude Long Endurance), fly at an altitude of 20000 m and conduct strategic reconnaissance and target designation. The complex includes synthetic aperture radar and a moving target indicator, as well as optical and infrared sensors. All three subsystems can work simultaneously, and one processor works on their data. Digital data can be transmitted to the ground in real time with line-of-sight or over a satellite link at speeds up to 50 Mbps. RPASs such as the Global Hawk are expensive to manufacture and operate, which leads to the search for cheaper HAPS counterparts to provide Internet coverage in remote regions, target detection and recognition. There is interest in the development of low-cost UAVs networks, which together provide reliable communications, sufficient performance and have increased autonomy.
In the existing literature on HAPS and stratospheric drones, there is no quantitative information on the loss of data packets when communicating with drones. How is packet loss related to an increase in the number of cellular network users? How does the message size affect the percentage of losses? How does nonlinearity, modulation type, and antenna size affect packet loss? Our article is devoted to the development of these issues.