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In a wireless communications network served by a high altitude platform (HAP) the cochannel interference is a function of the antenna beamwidth, angular separation and sidelobe level. At the millimeter wave frequencies proposed for HAPs, an array of aperture type antennas on the platform is a practicable solution for serving the cells. We present a...
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... (18) where is the displacement transformed to a plane normal to and centered on antenna boresight, as shown in Fig. 6 ( 19) The pointing angles and subtended angles for each cell are, thus, a function of cell coordinates and dimensions and only, and may hence be rapidly generated on changing HAP height or cell width . Let and be the indices for the curve fits of the form in (1) for an elliptic beam, fitted to optimize directivity at the cell edges and ...
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... The superiority of hexagonal arrays over circular arrays was mentioned in [34]. Antennas serving cells produce interference in a HAPs system by intersecting the main lobes or sidelobes [37]. In fact, the array performance in terms of radiation pattern, gain, beam steering, peak sidelobe level (PSLL), antenna mutual coupling, and inter-element distance significantly influences the quality of overall wireless communication [29]. ...
The Uniform hexagonal array (UHA) sidelobe level (SLL) reduction is a crucial consideration for avoiding co-channel interference and improving Carrier-to-interference Ratio (CIR) performance in HAP wireless networks using the TVWS spectrum. The SLL reduction in UHA has been researched by applying evolutionary algorithms such as genetic algorithm (GA) and Particle Swarm Optimization (PSO). However, such algorithms have the drawbacks such as early convergence and the inability to reach globally. The beam pointing approaches for UHA antennas using Modified PSO (MPSO), for reducing the SLL on finding the optimal current weights is presented in this article. The UHA antenna array with 19 cells fitted with 169 elements in the HAPs cellular structure is considered to simulate the proposed approach. Then, the MPSO approach is employed and compared with the standard PSO algorithm and Uniform Weighting (UW) scheme. As per the simulation findings, the proposed approach drastically decreased sidelobes, with a reduction of up to −6.84dB and −13.3dB when compared to PSO and UW respectively. In other words, the proposed approach outperforms the UW and the PSO algorithms. Moreover, the CIR performance of the proposed approach has been demonstrated in terms of average outage probability and the proposed approach provides a better result.
... High Altitude Platform Station is an alternate approach for telecommunication infrastructure solution for rural and remote areas based on stratospheric airborne platform [3]. HAPs have the potential to provide line-ofsight links to a large number of users, situated over a large geographical area, and using considerably less communications infrastructure than that required if delivered by a terrestrial network [4]. The High-Altitude Platforms are said to be a radio communication station situated in the stratospheric layer of the atmosphere at an altitude of about 17-22km above the sea level. ...
... Number of air molecules per unit area decreases with an increase in altitude because of weakening of gravitational pull, air is denser closer to Earth's surface than that of higher altitude [3]. More than half of atmospheric molecules are present inside 5.5 km radius from Earth's surface so air pressure decreases rapidly with first few kilometers in altitude, afterwards it decreases monotonously [4]. Wind speed is a great factor that affects the positioning of HAP in space. ...
In this paper, we investigated the effect of different channel propagation characteristics on the performance of 4G systems from high altitude platforms (HAPs). The use of High-Altitude Platforms for communication purpose in the past focused mostly on the assumption that the platform is quasi stationary. The technical limitation of the assumption was that of ensuring stability in the positioning of the platform in space. The use of antenna steering and other approaches were proposed as a solution to the said problem. In this paper, we proposed a channel model which account for the motion of the platform. This was done by investigating the effect of Doppler shift on the carrier frequency as the signals propagate between the transmitter and receiver while the High-Altitude Platform is in motion. The basic free space model was used and subjected to the frequency variation caused by the continuous random shift due to the motion of the HAPs. The trajectory path greatly affects the system performance. A trajectory of 30km, 100km and 500km radii were simulated. An acute elevation angle was used in the simulation. The proposed model was also compared to two other channel models to illustrate its performance. The results show that the proposed model behave similar to the existing models except at base station ID 35 and 45 where the highest deviation of 20dBm was observed. Other stations that deviated were less than 2dBm.
... Moreover, [135] investigates interference for ground users with two HAPs, showing that better performance is achieved if the users are spatially well separated. In [136], the authors improve the capacity of HAP systems by using mmWave frequencies. [136] also evaluates ground users' capacity regarding the angular separation between the ground users and HAPs. ...
... In [136], the authors improve the capacity of HAP systems by using mmWave frequencies. [136] also evaluates ground users' capacity regarding the angular separation between the ground users and HAPs. Furthermore, [136] analyze the coverage of HAPs operating at 48 GHz and 28 GHz frequencies discussing various crucial system parameters, including beam type and frequency reuse for cell planning. ...
... [136] also evaluates ground users' capacity regarding the angular separation between the ground users and HAPs. Furthermore, [136] analyze the coverage of HAPs operating at 48 GHz and 28 GHz frequencies discussing various crucial system parameters, including beam type and frequency reuse for cell planning. [137] focuses on the deployment of HAPs to characterize the HAP-to-ground link in terms of path loss and maximizes the on-ground coverage. ...
This paper surveys the literature on point-to-point (P2P) links for integrated satellite-aerial networks, which are envisioned to be among the key enablers of the sixth-generation (6G) of wireless networks vision. The paper first outlines the unique characteristics of such integrated large-scale complex networks, often denoted by spatial networks, and focuses on two particular space-air infrastructures, namely, satellites networks and high-altitude platforms (HAPs). The paper then classifies the connecting P2P communications links as satellite-to-satellite links at the same layer (SSLL), satellite-to-satellite links at different layers (SSLD), and HAP-to-HAP links (HHL). The paper surveys each layer of such spatial networks separately, and highlights the possible natures of the connecting links (i.e., radio-frequency or free-space optics) with a dedicated survey of the existing link-budget results. The paper, afterwards, presents the prospective merit of realizing such an integrated satellite-HAP network towards providing broadband services in under-served and remote areas. Finally, the paper sheds light on several future research directions in the context of spatial networks, namely large-scale network optimization, intelligent offloading, smart platforms, energy efficiency, multiple access schemes, distributed spatial networks, and routing.
... Their analysis indicated that 4 km circular spacing is optimal. In [146], the authors investigated the coverage performance of HAPS systems operating in 28 GHz and 48 GHz via approximating curve-fitting of the antenna pattern radiation. The analysis allowed the authors to shed some light on important issues, such as antenna beam type and frequency re-use, which affect cell planning in HAPS systems. ...
... In order to serve a large number of users/devices with different QoS requirements, the SINR level at the receiver is critical and requires sophisticated power management schemes. A significant portion of the proposed power control schemes in the literature on HAPS systems dates back RRM, Interference Management and Placement optimization in HAPS [70][71][72], [46] [151][152][153][154][155][156] [160][161][162][163][164][165][166][167][168][169][170][171][172][173][174], [178][179][180][181][182][183][184][185][186][187] Power Control & Interference Management in HAPS [152][153][154][155][156], [160][161][162][163] HAP Placement and Constellation Optimization [70], [151], [175] Channel/Subchannel Allocation and Spectrum Sharing [164][165][166][167][168][169][170][171][172][173][174] Mobility Considerations in HAPS [155], [159][160] Power Control in Multicasting [156], [161] Joint Computational and Radio Power Control in HAPS [162,163] Joint Power, Subchannel and Time Allocation [168][169][170] Spectrum Management and Sharing [171][172][173][174] Antenna and Interference Management [71,72], [146], [178][179][180][181][182][183][184][185][186][187] Coordinated Multipoint ...
... Transmission and Platform Diversity [71], [183][184][185] Adaptive Cell Shapes [146], [178][179][180][181][182] Massive MIMO [72], [186][187] to early 2000s, when most wireless communications research employed wide-band CDMA (WCDMA) for their air interface technology [152]- [156]. The frameworks of these power allocation schemes are more general and could be suitable (with minor modifications) for other potential radio access technologies, like multicarrier-CDMA [157] or power domain NOMA [158]. ...
A High Altitude Platform Station (HAPS) is a network node that operates in the stratosphere at an of altitude around 20 km and is instrumental for providing communication services. Precipitated by technological innovations in the areas of autonomous avionics, array antennas, solar panel efficiency levels, and battery energy densities, and fueled by flourishing industry ecosystems, the HAPS has emerged as an indispensable component of next-generations of wireless networks. In this article, we provide a vision and framework for the HAPS networks of the future supported by a comprehensive and state-of-the-art literature review. We highlight the unrealized potential of HAPS systems and elaborate on their unique ability to serve metropolitan areas. The latest advancements and promising technologies in the HAPS energy and payload systems are discussed. The integration of the emerging Reconfigurable Smart Surface (RSS) technology in the communications payload of HAPS systems for providing a cost-effective deployment is proposed. A detailed overview of the radio resource management in HAPS systems is presented along with synergistic physical layer techniques, including Faster-Than-Nyquist (FTN) signaling. Numerous aspects of handoff management in HAPS systems are described. The notable contributions of Artificial Intelligence (AI) in HAPS, including machine learning in the design, topology management, handoff, and resource allocation aspects are emphasized. The extensive overview of the literature we provide is crucial for substantiating our vision that depicts the expected deployment opportunities and challenges in the next 10 years (next-generation networks), as well as in the subsequent 10 years (next-next-generation networks).
... Moreover, [124] investigates interference for ground users with two HAPs, showing that better performance is achieved if the users are spatially well separated. In [125], the authors improve the capacity of HAP systems by using mmWave frequencies. [125] also evaluates ground users' capacity regarding the angular separation between the ground users and HAPs. ...
... In [125], the authors improve the capacity of HAP systems by using mmWave frequencies. [125] also evaluates ground users' capacity regarding the angular separation between the ground users and HAPs. Furthermore, [125] analyze the coverage of HAPs operating at 48 GHz and 28 GHz frequencies discussing various crucial system parameters, including beam type and frequency reuse for cell planning. ...
... [125] also evaluates ground users' capacity regarding the angular separation between the ground users and HAPs. Furthermore, [125] analyze the coverage of HAPs operating at 48 GHz and 28 GHz frequencies discussing various crucial system parameters, including beam type and frequency reuse for cell planning. [126] focuses on the deployment of HAPs to characterize the HAP-to-ground link in terms of path loss and maximizes the on-ground coverage. ...
This paper overviews point-to-point (P2P) links for integrated satellite-aerial networks, which are envisioned to be among the key enablers of the sixth-generation (6G) of wireless networks vision. The paper first outlines the unique characteristics of such integrated large-scale complex networks, often denoted by spatial networks, and focuses on two particular space-air infrastructures, namely, satellites networks and high-altitude platforms (HAPs). The paper then classifies the connecting P2P communications links as satellite-to-satellite links at the same layer (SSLL), satellite-to-satellite links at different layers (SSLD), and HAP-to-HAP links (HHL). The paper overviews each layer of such spatial networks separately, and highlights the possible natures of the connecting links (i.e., radio-frequency or free-space optics) with a dedicated overview to the existing link-budget results. The paper, afterwards, presents the prospective merit of realizing such an integrated satellite-HAP network towards providing broadband services in under-served and remote areas. Finally, the paper sheds light on several future research directions in the context of spatial networks, namely large-scale network optimization, intelligent offloading, smart platforms, energy efficiency, multiple access schemes, and distributed spatial networks.
... According to [19], these transceivers are co-located on the platform and they offer Line-of-Sight (LoS) communication to a geographic service area of approximately 60km diameter. Introducing specially designed antenna beam profiles, the cells formed on the ground are circular and of equal size [20]. In a HAP architecture, interference between cells is largely due to the gain profile and sidelobe levels of the antennas used. ...
... Definition 1. The cell coverage is defined as an area where the received SNR at the UE is larger than a certain threshold γ th [12], [13] ...
Recently, reconfigurable intelligent surfaces (RIS) have attracted a lot of attention due to their capability of extending cell coverage by reflecting signals toward the receiver. In this letter, we analyze the coverage of a downlink RIS-assisted network with one base station (BS) and one user equipment (UE). Since the RIS orientation and the horizontal distance between the RIS and the BS have a significant influence on the cell coverage, we formulate an RIS placement optimization problem to maximize the cell coverage by optimizing the RIS orientation and horizontal distance. To solve the formulated problem, a coverage maximization algorithm (CMA) is proposed, where a closed-form optimal RIS orientation is obtained. Numerical results verify our analysis.
... Various studies related to HAPS mobile communications have been conducted [10][11][12][13][14]. For example, some studies focused on antenna optimization for specific cell configurations [10,11], whereas others evaluated communications quality with cellular systems such as 4G LTE and WiMAX [12][13][14]. ...
... Various studies related to HAPS mobile communications have been conducted [10][11][12][13][14]. For example, some studies focused on antenna optimization for specific cell configurations [10,11], whereas others evaluated communications quality with cellular systems such as 4G LTE and WiMAX [12][13][14]. However, detailed studies on various cell configuration types depending on the number of available cells, such as those aiming to optimize the antenna patterns and tilt angles by considering the required communications quality, have not been conducted in conventional research. ...
... First, we show the performance gain of our proposed method. For comparison, we consider the geometrical approach presented in [10], where the antenna parameters were defined as the region bounded by the antenna halfpower beamwidth contour. Fig. 5 shows a hexagonal cell layout, where each HAPS consists of 7 cells, to explain the following antenna beamwidth calculation. ...
High-altitude platform stations (HAPSs) are expected to provide ultrawide-coverage areas and disaster-resilient networks from the stratosphere at around 20 km by installing wireless equipment on HAPS. Because their altitude is much lower than that of communications satellites, HAPSs can provide mobile communications services directly to smartphones, which are commonly used in terrestrial networks, such as fourth generation Long Term Evolution. Considering the widespread nature of mobile broadband communications and the importance as a backup line in case of disaster, HAPSs are expected to provide a large capacity in the future. A cellular system with single-cell frequency reuse using multiple cells similar to terrestrial mobile communications should be introduced to achieve such a capacity. The number of cells that a HAPS can accommodate ranges from 1 to more than 100, depending on unmanned aerial vehicle (UAV) ability. By contrast, the optimal cell configuration, which depends on the number of available cells, has not been clarified in previous research. In this paper, we propose an optimization method for the cell configuration for HAPS mobile communications using a genetic algorithm, which can be generally applied regardless of the number of cells and can clarify the optimal cell configuration. Although many cells are required to achieve gigabit-class HAPS mobile communications, the heightened power consumption due to the large number of cells is a critical problem for UAVs. Thus, we also investigate the reduction of the total transmission power and demonstrate the feasibility of energy-efficient gigabit HAPS mobile communications with wide coverage.
... Their analysis indicates that 4 km circular spacing is optimal. In [143], the authors investigate the coverage performance of HAPS operating in 28 GHz and 48 GHz via approximating curve-fitting of the antenna pattern radiation. The analysis allows the authors to shed some lights on the importance issues, such as the type of the antenna beam and the frequency reuse, affecting the cell planning in HAPS systems. ...
... in HAPS [] Power Control & Interference Management in HAPS [153][154][155][156][157], [160][161][162][163] HAPS Placement and Constellation Optimization [175][176][177] Channel/Subchannel Allocation and Spectrum Sharing [164][165][166][167][168][169][170][171][172][173][174] Mobility and Power Control [156], [160][161] Power Control for Multicast Services [95], [98], [106][107][108] Joint Radio and Computational Power Management [163] Joint Power, Subchannel and Time Allocation [168][169][170] Spectrum Management and Sharing [171][172][173][174] Antenna and Interference Management [142,143] [178][179][180][181][182][183][184][185][186][187][188][189][190][191] Exploiting Coordinated Multipoint Transmission and Platform Diversity [142], [185][186][187] Adaptive Cell Shaping [143], [178][179][180][181][182][183][184] Massive MIMO for HAPS Systems [188][189][190][191] A significant portion of the proposed power control schemes in the HAPS systems literature dates back to early 2000's, where at that time, the air interface technology that was adopted in most wireless communications research works was the wide-band CDMA (WCDMA) [153]- [157]. The frameworks of these power allocation schemes are more general and could be suitable (with minor modifications) for other potential radio access technologies like multicarrier-CDMA [158] or power domain NOMA [159]. ...
... in HAPS [] Power Control & Interference Management in HAPS [153][154][155][156][157], [160][161][162][163] HAPS Placement and Constellation Optimization [175][176][177] Channel/Subchannel Allocation and Spectrum Sharing [164][165][166][167][168][169][170][171][172][173][174] Mobility and Power Control [156], [160][161] Power Control for Multicast Services [95], [98], [106][107][108] Joint Radio and Computational Power Management [163] Joint Power, Subchannel and Time Allocation [168][169][170] Spectrum Management and Sharing [171][172][173][174] Antenna and Interference Management [142,143] [178][179][180][181][182][183][184][185][186][187][188][189][190][191] Exploiting Coordinated Multipoint Transmission and Platform Diversity [142], [185][186][187] Adaptive Cell Shaping [143], [178][179][180][181][182][183][184] Massive MIMO for HAPS Systems [188][189][190][191] A significant portion of the proposed power control schemes in the HAPS systems literature dates back to early 2000's, where at that time, the air interface technology that was adopted in most wireless communications research works was the wide-band CDMA (WCDMA) [153]- [157]. The frameworks of these power allocation schemes are more general and could be suitable (with minor modifications) for other potential radio access technologies like multicarrier-CDMA [158] or power domain NOMA [159]. ...
A High Altitude Platform Station (HAPS) is a network node that operates in the stratosphere at an altitude around 20 km and is instrumental for providing communication services. Triggered by the technological innovations in the areas of autonomous avionics, array antennas, solar panel efficiency levels and the battery energy density, and fueled by the flourishing industry ecosystems, the HAPS exerts itself as an indispensable component of the next generations of wireless networks. In this article, we provide a vision and framework for the HAPS networks of the future supported by a comprehensive and state-of-the-art literature survey. We highlight the undiscovered potential of HAPS systems, and elaborate on their unique ability to serve metropolitan areas. The latest advancements and promising technologies in the HAPS energy and payload systems are discussed. The integration of the emerging Reconfigurable Smart Surface (RSS) technology in the communications payload of HAPS systems for providing a costeffective deployment is proposed. A detailed overview of the radio resource management in HAPS systems is presented along with synergistic physical layer techniques, including Faster-Than-Nyquist (FTN) signaling. Numerous aspects of handoff management in HAPS systems are delineated. The notable contribution of Artificial Intelligence (AI) in HAPS, including machine learning in the design, topology management, handoff, and resource allocation aspects are emphasized. The provided extensive overview of the literature is crucial for substantiating our vision that that depicts the expected deployment opportunities and challenges in the next 10 years (next-generation networks), as well as in the subsequent 10 years (next-next-generation networks).
... Apart from coverage area, other performance indicators are also affected by changes in UAV height, such as carrier to interference ratio and handovers. Focusing on mm-wave band, authors in [21] investigate coverage versus carrier to interference ratio patterns using an antenna pattern approximated by a cosine function raised to a power. Building upon the work in [21], the effect of lateral displacement of a UAV on interference and handovers is studied in [22]. ...
... Focusing on mm-wave band, authors in [21] investigate coverage versus carrier to interference ratio patterns using an antenna pattern approximated by a cosine function raised to a power. Building upon the work in [21], the effect of lateral displacement of a UAV on interference and handovers is studied in [22]. Authors in [23] measure Receive Signal Strength Indicator (RSSI) for three UAV based cellular networks using following models: ...
Current studies on Unmanned Aerial Vehicle (UAV) based cellular deployment consider UAVs as aerial base stations for air-to-ground communication. However, they analyze UAV coverage radius and altitude interplay while omitting or over-simplifying an important aspect of UAV deployment, i.e., effect of a realistic antenna pattern. This paper addresses the UAV deployment problem while using a realistic 3D directional antenna model. New trade-offs between UAV design space dimensions are revealed and analyzed in different scenarios. The sensitivity of coverage area to both antenna beamwidth and height is compared. The analysis is extended to multiple UAVs and a new packing scheme is proposed for multiple UAVs coverage that offers several advantages compared to prior approaches.
