High Altitude Platform Networks Research Articles

Efficient Data Transmission Scheme for Massive High Altitude Platform Networks

Efficient Data Transmission Scheme for Massive High Altitude Platform Networks

Networking of Internet of UAVs: Challenges and Intelligent Approaches

Internet of unmanned aerial vehicle (I-UAV) networks promise to accomplish sensing and communication tasks quickly, robustly, safely, and cost-efficiently via effective situation awareness and cooperation among UAVs. To achieve the promising benefits, the crucial IUAV networking issue should be tackled. This article argues that I-UAV networking can be classified into two categories: quality-of-service (QoS) driven networking and quality-of-experience (QoE) driven networking. Each category of networking poses emerging challenges that have severe effects on the safe and efficient accomplishment of I-UAV missions. This article elaborately analyzes these challenges and expounds on the corresponding intelligent approaches to tackle the I-UAV networking issue. Besides, considering the uplifting effect of extending the scalability of I-UAV networks through cooperating with high altitude platforms (HAPs), this article gives an overview of the integrated I-UAV and HAP network and presents the corresponding networking challenges and intelligent approaches.

Beam Size Optimization for High-Altitude Platforms to Ground Links in FSO Communications

Free-space optical (FSO) communication has been used in practice mainly for short-distance transmission because it requires light of sight (LoS) between the transmitter and receiver. For long-distance communication, to avoid terrestrial obstacles, high-altitude platforms (HAPs) flying at stratosphere are used to carry intermediate FSO transceivers which relay data through several hops from the source to the destination stations. A HAP can communicate with a large ground area if its FSO transceiver projects a wide beam onto the ground. However, an excessively large beam makes the FSO transceiver consume a lot of energy. This study investigates the problem of finding individual optimal beam sizes for FSO transceivers on HAPs so that the total cost of the HAP network, including the amortization, energy, and maintenance costs, is minimized. An optimization algorithm was proposed and implemented. The simulation results show the network designed by the algorithm achieves a nearly optimal number of HAPs, leading to a low network cost.

Spectrum Sharing Between High Altitude Platform Network and Terrestrial Network: Modeling and Performance Analysis

Achieving seamless global coverage is one of the ultimate goals of space-air-ground integrated network, as a part of which High Altitude Platform (HAP) network can provide wide-area coverage. However, deploying a large number of HAPs will lead to severe congestion of existing frequency bands. Spectrum sharing improves spectrum utilization. The coverage performance improvement and interference caused by spectrum sharing need to be investigated. To this end, this paper analyzes the performance of spectrum sharing between HAP network and terrestrial network. We firstly generalize the Poisson Point Process (PPP) to curves, surfaces and manifolds to model the distribution of terrestrial Base Stations (BSs) and HAPs. Then, the closed-form expressions for coverage probability of HAP network and terrestrial network are derived based on differential geometry and stochastic geometry. We verify the accuracy of closed-form expressions by Monte Carlo simulation. The results show that HAP network has less interference to terrestrial network. Low height and suitable deployment density can improve the coverage probability and transmission capacity of HAP network.

Uplink Multiple Access With Semi-Grant-Free Transmission in Integrated Satellite-Aerial-Terrestrial Networks

This paper investigates a semi-grant-free (SGF) based transmission strategy to provide a flexible connectivity for various kinds of users in an integrated satellite-aerial-terrestrial network (ISATN). Herein, a high-altitude platform (HAP) termed as a grant-based user (GBU), which serves multiple mobile terminals (MTs) through space division multiple access (SDMA), wants to access a satellite network with multiple earth stations (ESs) termed as grant-free users (GFUs) simultaneously via non-orthogonal multiple access (NOMA) assisted SGF. To this end, we first propose two SGF-based uplink transmission schemes for both perfect channel state information (CSI) and imperfect CSI cases. When perfect CSI is available, a zero-forcing based beamforming (BF) scheme is used in HAP network while an adaptive transmit power allocation (ATPA) approach is adopted for SGF transmission. When only imperfect CSI is available, BF scheme employing the derived channel correlation matrix of HAP-MT link is proposed to achieve SDMA, and a novel ATPA strategy with rate probability constraint is proposed to guarantee quality-of-service of the GBU. Next, we derive the closed-form throughput expressions to evaluate the performance of the considered ISATN with the proposed two SGF-based schemes. Finally, computer simulations are conducted to validate the theoretical performance analysis and show the superiority of the proposed schemes over the related works. Moreover, our numerical results not only demonstrate a satisfactory performance of the proposed SGF-based scheme using imperfect CSI, but also reveal the impact of CSI errors on the system performance.

Joint HAP deployment and resource allocation for HAP‐UAV‐terrestrial integrated networks

While the terrestrial base stations (TBSs) in the fifth-generation (5G) network provide high throughput for the conventional terrestrial users (TUs), it is still challenging for the network to support massive TUs and unmanned aerial vehicles (UAVs) simultaneously due to the complicated air–ground channel and severe interference. In this paper, the deployment of a high-altitude platform (HAP) as a supplement for the terrestrial networks, in which the HAP and TBSs serve TUs and UAVs simultaneously in a joint manner, is studied. The novel network has two challenges. First, the deployment of the HAP, which is a new degree of freedom, should be optimized considering the terrestrial network. Second, the channel of the joint HAP and TBS network that serves multiple TUs and UAVs concurrently is complicated, and the resource allocation of the network should be designed. To tackle the above two challenges, a joint resource allocation and HAP deployment problem are formulated, and a gradient-and-matching-based algorithm is proposed to solve it efficiently. Simulation results show that the HAP and the proposed algorithm enhance the sum-rate of the network by over 30%, and the average data rate of both the TUs and the UAVs can be effectively improved.

Survivable free space optical mesh network using high-altitude platforms

Free space optical (FSO) communication refers to the information transmission technology based on the propagation of optical signals in space. FSO communication requires that the transmitter and receiver directly see each other. High-altitude platforms (HAPs) have been proposed for carrying FSO transceivers in the stratosphere. A multihop HAP network with FSO links can relay traffic between ground FSO nodes. In this study, we propose an end-to-end switching model for forwarding traffic between massive pairs of ground FSO nodes over a HAP network. A protection mechanism is employed for improving the communication survivability in the presence of clouds, which may break the line of sight (LoS) between HAPs and ground nodes. We propose an algorithm to identify a set of necessary HAPs and to design the HAP network topology in integrating the protection mechanism. The design aims to a network with the minimal equipment cost. The results demonstrate that, even though networks with survivable capacity use more resources, they are not necessary much more expensive than those without survivability in terms of equipment, i.e., HAPs and FSO devices, and in terms of wavelength resource utilization.

Robust Multi-Objective Beamforming for Integrated Satellite and High Altitude Platform Network With Imperfect Channel State Information

In this paper, we propose a robust beamforming (BF) scheme for an integrated satellite and high altitude platform network, where a multibeam satellite system shares the millimeter wave spectrum with a high altitude platform system. Specifically, we first exploit the weighted Tchebycheff method and formulate a multi-objective optimization problem to obtain the Pareto optimal trade-off between two conflicting yet desirable objectives, namely, sum rate maximization and total transmit power minimization, while satisfying the quality-of-service constraints of both earth stations and mobile terminals and per-antenna transmit power budget. Then, by using the angular information based imperfect channel state information, we propose a low-complexity discretization method to transform the non-convex objective function and constraints to the convex ones. Furthermore, a monotonic optimization scheme combined with iterative penalty function algorithm is presented to obtain the BF weight vectors with low computational complexity and fast convergence rate. Finally, numerical results are provided to confirm the effectiveness and superiority of the proposed approach in comparison to the existing related works.

5G Capacity Design Based on User Demand in Single High Altitude Platform Network

HAPS (High Altitude Platform Station) is an alternative technology of communication system that utilizes terrestrial and satellite systems. HAPS technology is in stratosphere layer with a height of 17-22 km above the earth's surface. HAPS has some advantages, which are wide range area, communication ability on line of sight (LOS), dan low propagation delay. One of the applications that can be employed in HAPS system is cellular with 5G technology. Cellular system is used in wireless communication since it has big capacity. This study analyzes the capacity of 5G cellular in single HAPS system in which the bandwidths used are 0.1 GHz and 1 GHz. Simulation result shows that outage probability using 0.1 GHz bandwidth resulting the capacity in single HAPS system, which is maksimum 550 users in reference cell can achive 10-15 and it also happen when using 1 GHz with maksimum 5500 users in reference cell*****HAPS (High Altitude Platform Station) adalah alternatif teknologi telekomunikasi sebagai pelengkap sistem eksisiting yaitu terestrial dan satelit. Salah satu aplikasi yang dapat digunakan dalam sistem HAPS adalah teknologi seluler 5G. Namun, interferensi merupakan salah satu masalah dalam mencapai kapasitas maksimum. Teknik multispot beam dan power control keduanya digunakan untuk mengatasi masalah tersebut. Teknik multispot beam ini berfungsi seperti pada sistem antena BTS terestrial. Akan tetapi antena multispot beam pada sistem HAPS ditempatkan berdekatan pada satu wahana atau platform HAPS. Oleh karena itu sinyal interferensi dari tiap pengguna akan menempuh jarak lintasan yang hampir sama dengan sinyal yang diinginkan. Berbeda dengan sistem BTS terestrial di mana setiap pengguna mendapat kontrol daya dari BTS yang berada di setiap sel. Panjang lintasan yang diambil oleh setiap sinyal pengguna berbeda sehingga nilai shadowing juga berbeda. Paper ini bertujuan untuk mengevaluasi kapasitas 5G seluler dalam sistem HAPS tunggal di mana bandwidth yang digunakan adalah 0,1 GHz dan 1 GHz. Hasil simulasi menunjukkan bahwa probabilitas outage menggunakan bandwidth 0,1 GHz menghasilkan kapasitas dalam sistem HAPS tunggal, maksimum 550 pengguna dan jika menggunakan 1 GHz maka maksimum jumlah pengguna adalah 5500 pengguna dalam referensi sel

High-Altitude Platform for Free-Space Optical Communication: Performance Evaluation and Reliability Analysis

High-altitude platforms (HAPs) have been proposed previously for transmitting radio frequency signals from ground stations over large distances of several hundred kilometers. These HAP architectures suffer from the limitations of data rate. The availability of the system has also not been evaluated for these architectures. In this paper, we propose a high-capacity and highly reliable optical wireless multi-hop HAP network configuration with free-space optical links from the ground stations and between the serial HAPs in the stratosphere. In the proposed scheme, communication services for long distance requiring very high bandwidth are transmitted optically from the ground station to the HAP station in the stratosphere, where it can cover distances of several hundreds of kilometers on the free-space optical links with serial multiple hops and be transmitted back optically to the distant ground receiver. In order to increase reliability and availability, particularly with reference to fading of vertical links due to atmospheric conditions, alternate slant links are added as redundant paths. The closed-form expressions for the average bit error rate and average channel capacity are derived assuming the composite channel model, which includes atmospheric attenuation, turbulence, and pointing errors. The gamma-gamma distribution with beam wander effect is used to model the atmospheric turbulence. Beam optimization is also done using the Nelder-Mead simplex algorithm. The effects of beam wandering and random pointing error are mitigated by using multi-hop HAP architecture. Link availability and system downtime of the complete ground-to-ground FSO network and reconfigured architecture has been calculated for component failure and atmospheric turbulence, moderate fog, rain, and snow. The proposed reconfigured architecture has high availability, meeting telecom requirements, and high mean time between failures and lower system downtime.

Diversity Performance Analysis on Multiple HAP Networks.

One of the main design challenges in wireless sensor networks (WSNs) is achieving a high-data-rate transmission for individual sensor devices. The high altitude platform (HAP) is an important communication relay platform for WSNs and next-generation wireless networks. Multiple-input multiple-output (MIMO) techniques provide the diversity and multiplexing gain, which can improve the network performance effectively. In this paper, a virtual MIMO (V-MIMO) model is proposed by networking multiple HAPs with the concept of multiple assets in view (MAV). In a shadowed Rician fading channel, the diversity performance is investigated. The probability density function (PDF) and cumulative distribution function (CDF) of the received signal-to-noise ratio (SNR) are derived. In addition, the average symbol error rate (ASER) with BPSK and QPSK is given for the V-MIMO model. The system capacity is studied for both perfect channel state information (CSI) and unknown CSI individually. The ergodic capacity with various SNR and Rician factors for different network configurations is also analyzed. The simulation results validate the effectiveness of the performance analysis. It is shown that the performance of the HAPs network in WSNs can be significantly improved by utilizing the MAV to achieve overlapping coverage, with the help of the V-MIMO techniques.

Using a HAP Network to Transfer WiMAX OFDM Signals: Outage Probability Analysis

Transferring wireless broadband services across extremely far distances on Earth is usually implemented nowadays either by ground-based or satellite communications. Terrestrial networks require, however, heavy installation and maintenance costs, whereas satellite networks suffer from excessively high power requirements. An alternative but highly challenging solution is to employ a network consisting of high-altitude platforms (HAPs). In this paper, we propose a way of delivering WiMAX traffic using a serial multi-hop HAP network configuration. HAPs are located at specific locations in the stratosphere, pick up the traffic from the Earth region they cover, and communicate with each other using optical links. In such a configuration, we determine the WiMAX quality of service by evaluating the outage probability for the entire HAP network. The overall performance is examined by using a channel model that takes into account laser path loss and pointing error effects. The findings of the present study indicate that the consideration of specific network and channel model parameters is crucial toward the design and implementation of future multi-hop HAP networks.

High altitude platform networks: A feedback suppression algorithm for reliable multicast/broadcast services

High Altitude Platforms (HAP) are currently considered as an alternative solution for providing reliable multicast and broadcast services. The major problem limiting the scalability of such systems is Feedback Implosion, a problem arising whenever a large number of users transmit their feedback messages. In the present Letter, a novel scheme is proposed which takes into account rain attenuation being the dominant factor impairing link performance. The proposed scheme is based on the selection of an Area Representative (AR) which is responsible for providing quick feedback messages to the HAP, thus suppressing feedback messages sent by other users. The proposed scheme is assessed both through analytical modeling and simulation with very satisfactory results.

Network architectures exploiting multiple HAP constellations for load balancing

This paper addresses network architectures in a constellation of high altitude platforms (HAPs) with overlapping coverage areas, focusing on the additional network elements/functionalities required...

Selection Combining Site Diversity Performance in High Altitude Platform Networks

High altitude platform networks operating in Ka-bands and V-bands exhibit severe degradation due to multiple atmospheric phenomena. In such frequencies, site diversity is a very efficient fade mitigation technique. This letter introduces a novel physical analytical model for the evaluation of selection combining site diversity error performance, taking into account the spatial correlation of rain attenuation and the total attenuation statistics. The outage performance of selection combining reception is being calculated through exact close-form formulas. Numerical results highlight the significant improvement against single site reception and determine the optimum relative positioning of main and diverse sites.

A new methodology for estimating the impact of co-channel interference from high-altitude platforms to terrestrial systems

This paper addresses an in-depth analysis of the stratosphere-to-Earth co-channel interference produced by high-altitude platforms (HAPs) and proposes a new methodology for the evaluation of its impact to terrestrial systems in terms of fractional degradation in performance, taking into account parameters such as HAP's mobility, realistic distribution of azimuth and elevation angles of the terrestrial microwave links (TMLs), and gradual high-altitude platform network (HAPN) loading. Simulations performed for different HAPN configurations, prove that the implementation of the methodology proposed, may lead to a more efficient use of the spectrum shared between the two services.

Interference Environment Between High Altitude Platform Networks (HAPN), Geostationary (GEO) Satellite and Wireless Terrestrial Systems

A new broadband telecommunication system has been recently proposed for provision of fixed, mobile and personal services adopting the use of high altitude platform stations placed in a fixed position in the stratospheric layer at heights from 15.5 to 30 km. The International Telecommunication Union (ITU) has allocated a pair of 300 MHz of spectrum in the V band for these services, which is already in use by geostationary satellite and wireless terrestrial systems as co-primary allocations. This paper addresses an in-depth co-channel interference analysis and proposes a C/I (carrier-to-interference) calculation model applicable to all the interference propagation paths as well as sharing criteria between HAPN, GEO satellite and wireless terrestrial systems extracted from simulations performed in urban, suburban and rural environments. By evaluating the interference density cumulative probability distribution functions, sufficient geographical separation distances between the ground stations are proposed which guarantee the harmonic co-existence between the three broadband systems. Maintaining the platform stable in the stratosphere is a key issue, and in this paper the effect of the three different stratospheric platform's movement models (ITU, HELINET, HALO) appearing in the literature, on C/I levels is estimated.