Energy Harvesting in High Altitude Platform Station Enabled Sensor Networks

Semi-Markov modeling approach for the reliability analysis of a multiple high altitude platform station system

The object of this study is a stratospheric airship-based telecommunication platform, employed as a high-altitude platform station (HAPS), designed to operate at altitudes of 20–30 km and provide broadband connectivity in regions with limited terrestrial infrastructure such as rural and remote areas of the Republic of Kazakhstan. The key research problem is to ensure stable connectivity of HAPS-based telecommunication platforms under strong stratospheric winds, with limited payload capacity and energy resources, while developing a scalable network architecture for multi-airship coordination. This paper proposes a network concept based on modular nano-airships, which reduces drag, enhances maintainability, and ensures continuous service. Calculations of lifting capacity, aerodynamic drag of different envelope shapes, energy balance, and the coverage radius of a single station were performed. Experimental tests of a prototype confirmed the feasibility of using the sub-GHz band (433 MHz) to provide long-range communication under ground test conditions, where signal attenuation was found to be minimal compared to higher frequencies. Due to the obtained characteristics, the hypothesis of employing a group of smaller airships instead of a single large carrier was confirmed. This is explained by their reduced sensitivity to wind loads, flexibility in network configuration, and lower operational risks. Unlike traditional satellite systems, which are expensive to launch and maintain, stratospheric airships can be recovered, repaired, and redeployed at relatively low cost, offering an economically viable solution for developing regions. The results can be applied in the creation of national communication networks for remote and sparsely populated areas of the Republic of Kazakhstan, in emergency response operations, and as a complementary layer to satellite constellations. The proposed concept demonstrates that modular HAPS networks are a realistic and scalable alternative, capable of providing broadband access under real-world atmospheric and geographic constraints

Sustainability and latency are two critical parameters for future generations of cellular communication networks, such as the sixth generation (6G). Moreover, the "connecting the unconnected" initiative—enabling ubiquitous connectivity—is expected to play a vital role in 6G and beyond networks. In this regard, this work is positioned at the intersection of these concepts. More specifically, network energy consumption is minimized through the application of cell switching concepts, while simultaneously reducing the number of handovers. A mixed-integer programming (MIP) optimization problem was modelled, and a heuristic-based solution algorithm was developed. To address ubiquitous connectivity, high-altitude platform stations (HAPS) are integrated into the network architecture as IMT base stations (i.e., HIBS). The inclusion of HIBSs provides additional capacity for cell switching and traffic offloading purposes, while also enhancing connectivity through their extensive coverage footprints. The efficacy of the developed optimization problem and heuristic-based solution was validated through simulation studies, in which various users, terrestrial base stations, and HIBSs were incorporated into the system modelling. The results confirm that the proposed methodology effectively reduces both energy consumption and the number of handovers, with performance strongly influenced by the handover penalty and the number of users in the network. Overall, the findings suggest that the outcomes of this research can enable more efficient and sustainable industrial operations and management through minimized energy consumption and handovers along with the huge coverage of HIBSs.

The object of the study is the methods of radio frequency resource management in stratospheric communication systems based on high altitude platform stations (HAPS). The problem addressed is the limited radio frequency spectrum, frequency overlap with fifth- and sixth-generation (5G/6G) networks, and the high probability of interference, which complicate efficient spectrum utilization and coordination. The obtained results indicate that within the frequency bands recommended by the International Telecommunication Union (ITU) — 21.4–22.0 GHz, 24.25–27.5 GHz, 47.2–47.5 GHz, and 47.9–48.2 GHz — the probability of interference reaches up to 70% in the 27.5–28.35 GHz band. By applying cognitive radio (CR) technology, interference levels decreased by 60%, and spectrum utilization efficiency increased by 35%. Dynamic spectrum access (DSA) improved spectrum efficiency by 30–45%, while spectrum sharing methods enhanced it by 40–60%. A brief explanation of the results shows that the proposed management approaches significantly increase the efficiency of radio frequency resource use and substantially reduce interference. For example, at a bandwidth of 100 MHz and a signal-to-noise ratio (SNR) of 10, the channel capacity reached approximately 332 Mbps. The distinctive features of the results lie in the comprehensive use of modern technologies that effectively address spectrum scarcity and interference issues, ensuring compatibility of HAPS with existing terrestrial and satellite communication systems. The proposed approaches are suitable for implementation in international and national spectrum coordination and licensing frameworks aimed at expanding broadband connectivity in underserved regions

High-altitude platform stations (HAPS) are systems that fly about 20 km above Earth to provide internet and monitor the environment. These solar-powered systems can stay in the air for months, bringing fast, reliable internet to remote areas and providing critical communication during emergencies like hurricanes or other natural disasters. HAPS are already being tested to connect communities, track wildfires, and check air quality. They have great potential to bring the internet everywhere, closing the so-called internet divide, but there are challenges. Current rules for airplanes need to be updated to include HAPS, and HAPS must be made tough enough to handle the extreme conditions in Earth’s stratosphere. Costs must also come down to make HAPS more affordable for underserved areas. If these challenges can be solved, HAPS could transform how people stay connected.

This paper examines cybersecurity threats in high-altitude platform station (HAPS) systems through reference architecture and attack tree methods. Given the rising commercial and military interest in these systems to enable next-generation 6G and hybrid telecommunication architectures, the threat of cyber and electronic attacks is increasing. The study focuses on providing the complete reference architecture of an aerostatic HAPS system equipped with a hybrid free-space optical and radio frequency transponder payload to be employed as a node of a nonterrestrial network. This study investigates potential attack vectors across various subsystems by coupling the attack tree methodology with the attack surface mapping derived from the reference architecture. Recommendations for mitigating cyberthreats and a secure-by-design approach are proposed to enhance the safety of future HAPS systems.

The aerial–terrestrial integrated Internet of Things (ATI-IoT) utilizes both aerial platforms (e.g., drones and high-altitude platform stations) and terrestrial networks to establish comprehensive and seamless connectivity across diverse geographical regions. The integration offers significant advantages, including expanded coverage in remote and underserved areas, enhanced reliability of data transmission, and support for various applications such as emergency communications, vehicular ad hoc networks, and intelligent agriculture. However, due to the inherent openness of wireless channels, ATI-IoT faces potential network threats and attacks, and its security issues cannot be ignored. In this regard, incorporating physical layer security techniques into ATI-IoT is essential to ensure data integrity and confidentiality. Motivated by the aforementioned factors, this review presents the latest advancements in ATI-IoT that facilitate physical layer security. Specifically, we elucidate the endogenous safety and security of wireless communications, upon which we illustrate the current status of aerial–terrestrial integrated architectures along with the functions of their components. Subsequently, various emerging techniques (e.g., intelligent reflective surfaces-assisted networks, device-to-device communications, covert communications, and cooperative transmissions) for ATI-IoT enabling physical layer security are demonstrated and categorized based on their technical principles. Furthermore, given that aerial platforms offer flexible deployment and high re-positioning capabilities, comprehensive discussions on practical applications of ATI-IoT are provided. Finally, several significant unresolved issues pertaining to technical challenges as well as security and sustainability concerns in ATI-IoT enabling physical layer security are outlined.

Stochastic fluid queue modelling and its analysis for power saving in high altitude platform station system: an analytical approach

Semantic communication technology, as it allows for source data meaning extraction and the transmission of appropriate semantic information only, has the potential to extend Shannon’s paradigm, which is concerned with the reproduction of a message from one location to another, regardless of its meaning. Nevertheless, some user terminals (UTs) may experience inadequate service due to their geolocation in reference to the base stations, which may entirely affect the accuracy of transmission and complicate deployment and implementation. A High-Altitude Platform Station (HAPS) serves as a key enabler for the deployment of wireless broadband in inaccessible areas, such as in coastal, desert, and mountainous areas. This paper proposes a novel HAPS relay-based semantic communication scheme, named DeepSTAS, which leverages deep learning techniques to enhance transmission accuracy. The proposed scheme focuses on attention-based semantic signal decoding, denoising, and forwarding modes; thus, called a CSA-DCGAN SDF HAPS relay network. The simulation results reveal that the proposed system with attention mechanisms significantly outperforms the system without attention mechanisms, both in peak signal-to-noise ratio (PSNR) and multi-scale structural similarity index (MS-SSIM); the proposed system can achieve a 2 dB gain when leveraging the attention mechanisms, and a PSNR of 38.5 dB can be obtained, with an MS-SSIM exceeding 0.999 at an approximate SNR of only 20 dB. The system provides considerable performance, more than 37 dB, and a corresponding MS-SSIM close to 0.999 at an estimated SNR of 20 dB when the CIFAR-100 dataset is considered and an MS-SSIM of 0.965 at an approximate SNR of only 10 dB on the Kodak dataset. The proposed system holds promise to maintain consistent performance even at low SNRs across various channel conditions.

This paper investigates the integration of High-Altitude Platform Stations (HAPS) with Deep Learning (DL) models to enhance coverage capabilities. Recognizing the inherent limitations of traditional HAPS coverage, which is typically confined to a circular area, this work proposes a novel approach utilizing a 60-element Concentric Circular Array (CCA) operating at 2.1 GHz. To dynamically generate multiple vertical/horizontal (V/H) directional beams, the system integrates a Deep Neural Network (DNN) with a modified version of the Gravitational Search Algorithm and Particle Swarm Optimization (MGSA-PSO) algorithm. This hybrid approach optimizes the feeding phases of the CCA elements, enabling the system to effectively cover diverse road paths. Furthermore, the study incorporates realistic scenarios by utilizing the Computer Simulation Technology-Microwave Studio Suite (CST) with the Earth Explorer (EE) user interface tool to model real-world road paths, including those traversing challenging terrains such as rugged deserts with mountain chains and forested areas.

ABSTRACTThe emergence of the 5G generation has considerably advanced wireless communication systems, with higher data rates and increased connectivity. Massive Multiple Input Multiple Output (mMIMO) structures, utilizing numerous antennas, improve spectral efficiency. High‐Altitude Platform Stations (HAPS) provide promising deployment structures for 5G networks. However, it faces challenges including useful resource allocation, interference mitigation, and dynamic beamforming adaptation. This study proposes an efficient method for optimizing communication systems through the use of HAPS through aggregate of game theory and dynamic optimization strategies. The model introduces a novel method known as Dynamic Levysalp Fusion Optimization (DLSFO), which integrates the Levy Flight Algorithm (LFA) and Improved Slap Swarm Optimization (ISSO) to enhance exploration and avoid local optima in mMIMO systems. The findings demonstrate the effectiveness of the proposed method with a system latency (SL), bit error rate (BER), and sum rate, showcasing its potential to increase overall system performance for multi‐person, multi‐beam conversation systems on HAPS.

In Japan, the DEURAS system has been deployed to detect and locate illegal radio sources that either exceed permissible transmission power limits or operate on unauthorized frequencies. This system utilizes receiving antennas installed on high-rise buildings and radio towers to capture radio signals and estimate the location of the transmission source. However, in densely built urban environments, the accuracy of location estimation is often compromised due to signal reflections and diffractions. Additionally, in large-scale disasters such as earthquakes, terrestrial infrastructure may be severely damaged, making it essential to develop a localization system that operates independently of ground-based stations. To overcome these limitations, this study proposes a localization system based on a high-altitude-platform station (HAPS), which operates at an altitude of approximately 20 km. The feasibility and effectiveness of the proposed system are evaluated through numerical simulations, considering various environmental conditions. The results demonstrate that HAPS-based localization significantly improves positioning accuracy, offering a robust and high-precision alternative for radio source detection, particularly in scenarios where traditional ground-based systems are unreliable or unavailable.

The first operational high altitude platform station is taking its place in the stratosphere after years of testing

Dimensioning Space-Air-Ground Integrated Networks for In-Flight 6G Slice Orchestration

System Design and Parameter Optimization for Remote Coverage From NOMA-Based High-Altitude Platform Stations (HAPS)

In this article, we propose a cell-free network architecture for an unmanned aerial vehicle (UAV) base station (BS), i.e., UBS, incorporating high-altitude platform stations (HAPSs) as central processing units (CPUs). The goal is to guarantee the quality of service (QoS) of user equipment (UE), reduce energy consumption, extend communication time, and facilitate rescue operations. The millimeter-wave (mmWave) frequency band is deployed in access and backhaul links to satisfy UE QoS requirements and high backhaul demands. The proposed framework jointly optimizes user association, backhaul bandwidth allocation, and power allocation to maximize energy efficiency while meeting QoS requirements. The optimization problem, modeled as non-convex mixed-integer nonlinear fractional programming, is solved through a three-stage iterative algorithm. This includes (1) optimizing power allocation based on Dinkelbach transformation and a successive convex approximation (SCA) method, (2) clustering UBSs using the Lagrangian method, and (3) deriving a closed-form bandwidth allocation factor. The proposed algorithm significantly outperforms many traditional algorithms in performance while maintaining low computational complexity.

Reliability analysis of energy management subsystem in a high altitude platform station using hierarchical stochastic models and machine learning

R&D of High Altitude Platform Station (HAPS) towards B5G/6G

In recent years, lithium-sulfur (Li-S) batteries have been widely developed as next generation secondary batteries for aircraft applications such as drones and HAPS (High Altitude Platform Station), which are requires high gravimetric energy density. In order to achieve the cell design of 350 Wh/kg class Li-S batteries, we should focus on these three steps.First, we need to develop elemental and process technologies to achieve the capacity close to the theoretical sulfur capacity. Second, we need to use an electrolyte that is sparsely soluble or insoluble in polysulfide. Thirdly, we have to minimize the components other than the active material. The cathode is conventionally composed sulfur in Ketjen black (KB) on aluminum foil current collector. However, this limits the capacity of about 1250 mAh/g. Additionally, increasing the thickness of the cathode is an effective method for minimizing the number of cathode substrates, however, it is difficult to balance the high sulfur loading amounts and the high-rate performances, due to a difficulty to make adequate Li ion and electron paths.1) Micro-porous carbon has been reported as a supporting material that can exhibit a capacity close to the theoretical sulfur capacity2), In this study, we focused on activated carbon (AC) manufactured by Kuraray, which is commercially available and has a proven track record of mass synthesis. We used it in combination with ultra-thin aluminum sheet, successfully achieving a 350 Wh/kg class Li-S laminated battery.S/AC composite was obtained by mixing sulfur and AC (YP-80F, Kuraray) with weight ratio of 60 : 40, followed by heating at 155 °C for 12 h. Afterward the of S/AC were de-agglomerated by using the energy ball milling (MM500nano, Retsch). S/AC cathode was fabricated by coating S/AC slurry (S/AC: carbon nanofiber (CNF) : binder = 92.5 :4 :3.5 by weight) on Al sheet. To assemble the cell, the cathode (S loading: 4.7 mg/cm2) was pressed to reduce its thickness by 34%. 5 Ah class laminated cell was prepared by stacking 10 sheets of the S/AC cathodes, 11 sheets of Li anodes, 20 sheets of a separator, and the electrolyte lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/lithium bis(fluorosulfonyl)imide (LiFSI) : sulfolane (SL) : hydrofluoroether (HFE) = 0.8/0.2: 1: 1.7 (molar ratio)). Electrochemical performances were tested with voltage range between 1.0 V – 3.3 V after activation process.Focusing on the de-agglomeration of the positive electrode active material, we investigated a dispersion process of S/AC composite to achieve a capacity close to the theoretical sulfur capacity. After preparing S/AC composite, the A/AC was de-agglomerated using the ball milling. Figure 1 shows the comparison of the capacity of dispersion phase A and B at each cycle. It was found that the dispersion treatment increases the initial capacity close to the theoretical capacity of 1672 mAh/g. Also, the dispersion treatment (phase B) increased the capacities up to the 15th cycle, compared with those without the treatment (phase A). This suggest that the well dispersed S/ACimproved the diffusion of Li ions.Furthermore, in order to increase the energy density of the battery, we adopted an ultra-thin Al current collector of 7 μm in thickness instead of the conventional 20 μm thick Al sheet, and using the above dispersion process, we fabricated a large 70 mm x 70mm Li-S laminated battery.Fig.2 shows its charge-discharge curve of a new designed Li-S battery. The first plateau, which is generally observed around 2.3 V in a conventional S/KB system, is not confirmed. This is a feature of micro-porous carbon system. The Li-S battery delivered a discharge capacity of 6.7 Ah, which is equal to 1632 mAh/g-S.Fig. 3 shows a comparison of battery weights by employing KB and AC. The capacity of S/KB is approximately 1150 mAh/g-S, which is smaller than that of the AC (1632 mAh/g-S). Therefore, the loading amount of the active material can be reduced by employing the AC instead of KB, resulting in reduction of the carbon constituting the complex at the same time. Consequently, a laminate-type battery with high capacity of 6.7 Ah, and energy density (351 Wh/kg, laminate film and tabs are excluded in this calculation) was achieved.In the presentation, I would like to discuss the effect of de-agglomeration of the S/AC composite. [References] [1]. H. Nara, et.al., J. Electrochem. Soc., 164, A5026–A5030 (2017).[2] S. Usuki, et. al., J. Electrochem. Soc., 85, 650–655 (2017). [Acknowledgement] This work was partly supported by Advanced Low Carbon Technology Research, Development Program Special Priority Research Area “Next-Generation Rechargeable Battery” (ALCA-Spring) from the Japan Science and Technology Agency (JST) (Grant Number JPMJAL1301). Figure 1