Satellite and high altitude platform-based inter-vehicle communications in vast and desolate areas

In order to solve the problem of inter-vehicle communication （IVC） in vast and desolate areas such as the desert and the Gobi, two vehicle network models are proposed. One is based on satellite communication and the other is based on high altitude platform （ HAP ） communication. The system outline and networking modes of the two models are described. In the satellite communication based model, all the vehicles are equipped with vehicle-bone satellite communication on the move terminals and the communication signals between vehicles are forwarded by satellite. In the high altitude platform-based model, the HAPs are equipped with base station facilities to form aerial base stations, and vehicles can communicate with each other via common terrestrial mobile communication devices. Some key parameters such as path loss, link loss and system capacity are also computed. The analysis shows that both the two models can satisfy the requirement of IVC in the descriptive environment.

COOPERATIVE DIRECTIONAL INTER-CELL HANDOVER SCHEME IN HIGH ALTITUDE PLATFORM COMMUNICATIONS SYSTEMS

A novel Cooperative Directional inter-cell Handover Scheme(CDHS) for High Altitude Platform(HAP) communications systems is proposed,in which the handover target cell and the two cells adjacent to this handover target cell work cooperatively to exploit the traffic fluctuation to improve handover performance.Users in the overlap area of the overloaded handover target cell will be forced to handover directionally before their optimal handover boundary in order to free up resources for the handover calls which would otherwise be dropped due to the shortage of resources and queue time out.Simulation results show that the handover call dropping probability is greatly reduced(at least 60%) compared with the general queue handover scheme,with little performance reduction to the call blocking probability,and the Not in the Best Cell(NBC) average time is only increased moderately.Moreover,an optimal cell radius can be achieved for a specific platform speed by minimizing the unified system performance,which is the linear combination of the handover call dropping probability and the NBC average time.

Statistical Modeling of the High Altitude Platform Dual-Polarized MIMO Propagation Channel

In order to investigate the benefit of multiple-input multiple-output(MIMO) technique applying to the high altitude platform(HAP), a 2×2 MIMO statistical model, which can accurately describe the channel between HAP and high-speed train, is presented. And dual polarization diversity is particularly considered. Based on first-order three-state Markov chain, the single-input single-output(SISO) channel, a subset of the MIMO channel is first established. The ray tracing approach applied to the digital relief model(DRM) which covers the railway between Xi'an and Zhengzhou is used to obtain the state probability vector and matrix of the state transition probability. The proposed model considers both Doppler shift and temporal correlation, and the polarization correlation and spatial correlation statistical properties of large-scale fading and smallscale fading are analyzed. Moreover, useful numerical results on the MIMO HAP channel outage capacity are provided based on which, significant capacity gains with respect to the conventional SISO case are illustrated. Such statistical channel model can be applied to the future wireless communication system between HAP and high-speed train.

STEERABLE ANTENNAS MOVEMENT COMPENSATION FOR HIGH ALTITUDE PLATFORM

High Altitude Platform(HAP) must compensate for relative motion with respect to the ground because of the stratosphere complexity,which is important to guarantee Quality of Service(QoS) in intended coverage area.With analysis on HAP movement models for predicting the geographical coverage in the cases of shift horizontally and vertically,yaw,roll and pitch,the mechanisms of steerable antennas movement compensation are investigated.The mechanism is applied to a scenario of 127 cell architecture,with a cell cluster size of four.By the simulation results of Carrier to Interference Ratio(CIR),the steerable antenna movement compensation mechanism decrease influence of HAP movement and guarantee effective coverage of the service area.

CAPACITY CALCULATION OF TD-CDMA HIGH ALTITUDE PLATFORM SYSTEM

A capacity calculation method of High Altitude Platform System(HAPS) is proposed in which TD-CDMA multiple access schemes are applied.With the influence of both power limit and bandwidth limit on capacity integrated,the paper derives the equations by which the capacity of TD-CDMA systems can be calculated,and performs calculation on a practical system.This calculation method is quite simple and effective with a comparatively small error,which is essential to the de-signing and research on HAPS.

Propagation Modeling and Characteristic Analysis of Terahertz Waves via High Altitude Platforms

Satellite-to-ground terahertz communication is limited by the power of signal source and antenna gain level,and has large path loss,which is difficult to implement.In this paper,a feasible scheme of satellite-to-ground terahertz communication using High Altitude Platforms(HAPs)as relay is presented,and the path loss on terahertz communication links is modeled and analyzed.Combined with the path loss model,the transmission loss along HAP-to-ground paths under different seasons and complex weather environment in Ali,Xizang,China is calculated.The results show that the transmission characteristics of terahertz waves in winter and summer are significantly different,mainly reflected in the number and bandwidth of usable atmospheric windows.Furthermore,the additional attenuation caused by the typical sand dust and ice cloud environment on terahertz band can reach 6.1 dB and 1.9 dB at the maximum respectively.With the aid of high gain antenna,the usable communication frequencies of the HAP-to-ground links in winter are significantly more than those in summer.When the transmitting and receiving antenna gain is 40 dBi respectively,the usable communication frequency can reach 1.35 THz in winter,while it is limited to less than 1 THz in summer,up to 0.493 THz.

Overview of development and regulatory aspects of high altitude platform system

High Altitude Platform(HAP)systems comprise airborne base stations deployed above 20 km and below 50 km to provide wireless access to devices in large areas.In this paper,two types of applications using HAP systems:one with HAP Station(HAPS)and the other with HAPS as International Mobile Telecommunication(IMT)Base Station(HIBS)are introduced.The HAP system with HAPS has already received wide recognition from the academia and the industry and is considered as an effective solution to provide internet access between fixed points in suburban and rural areas as well as emergencies.HAP systems with HIBS to serve IMT user terminal have just started to draw attention from researchers.The HIBS application is expected to be an anticipate mobile service application complementing the IMT requirement for cell phone or other mobile user terminals in which the service field of HAPS application cannot reach.After describing and characterizing the two types of systems,coexistence studies and simulation results using both the Power Fluxed Density(PFD)mask and separation distance based methods are presented in this paper.This paper also predicts future trends of the evolution paths for the HAP systems along with challenges and possible solutions from the standpoint of system architectures and spectrum regulation.

Low Altitude Satellite Constellation for Futuristic Aerial-Ground Communications

This paper discusses the significance and prospects of low altitude small satellite aerial vehicles to ensure smooth aerial-ground communications for next-generation broadband networks.To achieve the generic goals of fifthgeneration and beyondwireless networks,the existing aerial network architecture needs to be revisited.The detailed architecture of low altitude aerial networks and the challenges in resource management have been illustrated in this paper.Moreover,we have studied the coordination between promising communication technologies and low altitude aerial networks to provide robust network coverage.We talk about the techniques that can ensure userfriendly control and monitoring of the low altitude aerial networks to bring forth wireless broadband connectivity to a new dimension.In the end,we highlight the future research directions of aerial-ground communications in terms of access technologies,machine learning,compressed sensing,and quantum communications.

基于高空平台的边缘计算卸载:网络、算法和展望

高空平台(high altitude platform,HAP)技术与多接入边缘计算(multi-access edge computing,MEC)技术的结合将MEC服务器部署区域由地面扩展到空中,打破传统地面MEC网络的局限性,为用户提供无处不在的计算卸载服务。针对基于HAP的MEC卸载研究进行综述,首先,从HAP计算节点的优势、网络组成部分、网络结构、主要挑战及其应对技术4个方面分析基于HAP的MEC网络;其次,分别从图论、博弈论、机器学习、联邦学习等理论的角度对基于HAP的MEC卸载算法进行横向分析和纵向对比;最后,指出基于HAP的MEC卸载技术目前存在的问题,并对该技术的未来研究方向进行展望。

Analysis of Wireless Backhaul Networks Based on Aerial Platform Technology for 6G Systems

As next generation communication technologies emerge,new high data rate applications and high-definition large-screen video streaming have become very popular.As a result,network traffic has been increasing so much that existing backhaul networks soon will not be able to support all traffic demands.To support these needs in future 6G mobile systems,the establishment of an additional backhaul wireless network is considered essential.As one of the solutions,a wireless backhaul network based on an aerial platform has been proposed.In order to explore the potential of aerial platforms as wireless backhaul networks,in this paper,the categories for wireless backhaul networks based on aerial platforms are investigated.This paper includes a survey of the definitions and characteristics of low altitude platforms(LAPs)and high altitude platforms(HAPs),as well as channel models according to the atmosphere.For wireless backhaul network designs based on aerial platforms,altitude and platform selection options,deployment options,energy issues,and security based on target location and performance were considered in the analysis and investigation.

A novel 3-D spatial temporal channel model for high mobility HAPS-based communications scenario

A high altitude platform station （HAPS） based communications scenario for providing Intemet access and broadband multimedia services to the passengers on board of a high speed train （traveling up to 300km/h） is proposed. Regarding the addressed scenario, when the propagation link between HAPS and train is blocked by obstacles, a three-dimensional （3-D） geometrical single cylinder spatial-temporal channel model is presented, in which closed form, mathematically tractable space-time correlation functions are obtained. It shows that the correlation functions determined by the 3-D model are of significant difference with those of the conventional 2-D model. Based on the analysis model, the paper derives a realized simulation model using sum-of-sinusoids approach, and applies method of equal areas （MEA） and modified method of equal areas （MMEA） to determine the model parameters. The fitting performance of the simulation model with the analysis one is evaluated by two means-square error （MSE） performance criteria. Finally, numerical simulation results verify the mathematical analysis conclusion, when N ≥21, simulation model has an excellent fitness with the analysis one.

6G技术中的空中接入网:进展与展望

空中接入网(aerial access network, AAN)具有抗毁性强、覆盖范围广、视距传播概率高的特点,与地面网络相结合能够缓解流量负载压力,提供全时空的连接与服务,可有效助力第六代移动通信网络(6th generation mobile networks, 6G)“万物智联”愿景的实现.因此,在分析AAN中的卫星通信和高空平台(high altitude platform station, HAPS)技术研究进展的基础上,研究了卫星通信在数据接入方面的应用以及HAPS在一体化网络架构中的作用,探究了卫星与HAPS两种技术对未来网络的影响以及进一步优化二者的潜在方法.最后,对卫星接入的数据碰撞问题和HAPS的缓存问题进行讨论分析,并从上述问题出发展望了卫星通信和HAPS技术的未来发展方向.

HOT SPOT RELIEF WITH EMBEDDED BEAM FOR CDMA SYSTEMS IN HAPS

This paper proposes a novel micro/macro beam coverage scheme used in High Altitude Platform System (HAPS) Code Division Multiple Access (CDMA) systems. A relief of traffic burden in hot spot areas is achieved by embedding micro-beams into the macro-beams at the hot spot locations, together with appropriate power ratio control and user ratio control. The simulation results show that the hot spot problem can be relieved efficiently with the presented configuration, and a higher and more stable system capacity is expectable despite the variation of user distribution.

Distortion minimization for multimedia transmission in NOMA HAP-UAV integrated aerial access networks

Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel characteristics, this paper constructs an integrated network comprising the High Altitude Platform(HAP) and Unmanned Air Vehicles(UAVs) with the NonOrthogonal Multiple Access(NOMA) technology. In order to improve the transmission quality of images and videos, a power management scheme is proposed to minimize the distortion of the transmissions from the HAP and UAVs to the terminals. The power control is formulated as a non-convex problem constrained by the maximal transmit power and the minimal terminal rate requirements. The variable substitution and the first-order Tailor’s expansion is used to transform it into a sequence of convex problems, which are subsequently solved through the gradient projection method. Simulation demonstrates the signal distortion and error rate improvement achieved by the proposed algorithm.