43 research outputs found
A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future
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).Comment: To appear in IEEE Communications Surveys & Tutorial
HAPS for 6G Networks: Potential Use Cases, Open Challenges, and Possible Solutions
High altitude platform station (HAPS), which is deployed in the stratosphere
at an altitude of 20-50 kilometres, has attracted much attention in recent
years due to their large footprint, line-of-sight links, and fixed position
relative to the Earth. Compared with existing network infrastructure, HAPS has
a much larger coverage area than terrestrial base stations and is much closer
than satellites to the ground users. Besides small-cells and macro-cells, a
HAPS can offer one mega-cell, which can complement legacy networks in 6G and
beyond wireless systems. This paper explores potential use cases and discusses
relevant open challenges of integrating HAPS into legacy networks, while also
suggesting some solutions to these challenges. The cumulative density functions
of spectral efficiency of the integrated network and cell-edge users are
studied and compared with terrestrial network. The results show the capacity
gains achieved by the integrated network are beneficial to cell-edge users.
Furthermore, the advantages of a HAPS for backhauling aerial base stations are
demonstrated by the simulation results
Joint Beamforming and User Association Design for Integrated HAPS-Terrestrial Networks
Located in the stratospheric layer of Earth's atmosphere, the high altitude
platform station (HAPS) is a promising network infrastructure, which can bring
significant advantages to sixth-generation (6G) and beyond wireless
communications systems by forming vertical heterogeneous networks (vHetNets).
However, if not dealt with properly, integrated networks suffer from several
performance challenges compared to standalone networks. In harmonized
integrated networks, where different tiers share the same frequency spectrum,
interference is an important challenge to be addressed. This work focuses on an
integrated HAPS-terrestrial network, serving users in an overlapped urban
geographic area, and formulates a fairness optimization problem, aiming to
maximize the minimum spectral efficiency (SE) of the network. Due to the highly
nonconvex nature of the formulated problem, we develop a rapid converging
iterative algorithm that designs the massive multiple-input multiple-output
(mMIMO) beamforming weights and the user association scheme such that the
propagated inter- and intra-tier interference is managed. Simulation results
demonstrate the proposed algorithm's superiority over standalone terrestrial
networks and scenario where only the beamforming weights are optimized.Comment: 8 pages singlecolumn, 5 figures, under review in IEEE Communications
Letter
Terahertz-Enpowered Communications and Sensing in 6G Systems: Opportunities and Challenges
The current focus of academia and the telecommunications industry has been
shifted to the development of the six-generation (6G) cellular technology, also
formally referred to as IMT-2030. Unprecedented applications that 6G aims to
accommodate demand extreme communications performance and, in addition,
disruptive capabilities such as network sensing. Recently, there has been a
surge of interest in terahertz (THz) frequencies as it offers not only massive
spectral resources for communication but also distinct advantages in sensing,
positioning, and imaging. The aim of this paper is to provide a brief outlook
on opportunities opened by this under-exploited band and challenges that must
be addressed to materialize the potential of THz-based communications and
sensing in 6G systems.Comment: 2023 the 9th International Conference on Computer and Communications
(ICCC). arXiv admin note: text overlap with arXiv:2307.1032
The Coverage, Capacity and Coexistence of Mixed High Altitude Platform and Terrestrial Segments
This thesis explores the coverage, capacity and coexistence of High Altitude Platform (HAP) and terrestrial segments in the same service area. Given the limited spectrum available, mechanisms to manage the co-channel interference to enable effective coexistence between the two infrastructures are examined. Interference arising from the HAP, caused by the relatively high transmit power and the antenna beam profile, has the potential to significantly affect the existing terrestrial system on the ground if the HAP beams are deployed without a proper strategy. Beam-pointing strategies exploiting phased array antennas on the HAPs are shown to be an effective way to place the beams, with each of them forming service cells onto the ground in the service area, especially dense user areas. Using a newly developed RF clustering technique to better point the cells over an area of a dense group of users, it is shown that near maximum coverage of 96% of the population over the service area can be provided while maintaining the coexistence with the existing terrestrial system.
To improve the user experience at the cell edge, while at the same time improving the overall capacity of the system, Joint Transmission – Coordinated Multipoint (JT-CoMP) is adapted for a HAP architecture. It is shown how the HAP can potentially enable the tight scheduling needed to perform JT-CoMP due to the centralisation of all virtual E-UTRAN Node Bs (eNodeBs) on the HAP. A trade-off between CINR gain and loss of capacity when adapting JT-CoMP into the HAP system is identified, and strategies to minimise the trade-off are considered. It is shown that 57% of the users benefit from the JT-CoMP.
In order to enable coordination between the HAP and terrestrial segments, a joint architecture based on a Cloud – Radio Access Network (C-RAN) system is introduced. Apart from adapting a C-RAN based system to centrally connect the two segments together, the network functional split which varies the degree of the centralised processing is also considered to deal with the limitations of HAP fronthaul link requirements. Based on the fronthaul link requirements acquired from the different splitting options, the ground relay station diversity to connect the HAP to centralised and distributed units (CUs and DUs) is also considered
Space-Air-Ground Integrated 6G Wireless Communication Networks: A Review of Antenna Technologies and Application Scenarios
A review of technological solutions and advances in the framework of a Vertical Heterogeneous Network (VHetNet) integrating satellite, airborne and terrestrial networks is presented. The disruptive features and challenges offered by a fruitful cooperation among these segments within a ubiquitous and seamless wireless connectivity are described. The available technologies and the key research directions for achieving global wireless coverage by considering all these layers are thoroughly discussed. Emphasis is placed on the available antenna systems in satellite, airborne and ground layers by highlighting strengths and weakness and by providing some interesting trends in research. A summary of the most suitable applicative scenarios for future 6G wireless communications are finally illustrated
Terahertz Communications and Sensing for 6G and Beyond: A Comprehensive View
The next-generation wireless technologies, commonly referred to as the sixth
generation (6G), are envisioned to support extreme communications capacity and
in particular disruption in the network sensing capabilities. The terahertz
(THz) band is one potential enabler for those due to the enormous unused
frequency bands and the high spatial resolution enabled by both short
wavelengths and bandwidths. Different from earlier surveys, this paper presents
a comprehensive treatment and technology survey on THz communications and
sensing in terms of the advantages, applications, propagation characterization,
channel modeling, measurement campaigns, antennas, transceiver devices,
beamforming, networking, the integration of communications and sensing, and
experimental testbeds. Starting from the motivation and use cases, we survey
the development and historical perspective of THz communications and sensing
with the anticipated 6G requirements. We explore the radio propagation, channel
modeling, and measurements for THz band. The transceiver requirements,
architectures, technological challenges, and approaches together with means to
compensate for the high propagation losses by appropriate antenna and
beamforming solutions. We survey also several system technologies required by
or beneficial for THz systems. The synergistic design of sensing and
communications is explored with depth. Practical trials, demonstrations, and
experiments are also summarized. The paper gives a holistic view of the current
state of the art and highlights the issues and challenges that are open for
further research towards 6G.Comment: 55 pages, 10 figures, 8 tables, submitted to IEEE Communications
Surveys & Tutorial
Unmanned Aerial Vehicle (UAV)-Enabled Wireless Communications and Networking
The emerging massive density of human-held and machine-type nodes implies larger traffic deviatiolns in the future than we are facing today. In the future, the network will be characterized by a high degree of flexibility, allowing it to adapt smoothly, autonomously, and efficiently to the quickly changing traffic demands both in time and space. This flexibility cannot be achieved when the network’s infrastructure remains static. To this end, the topic of UAVs (unmanned aerial vehicles) have enabled wireless communications, and networking has received increased attention. As mentioned above, the network must serve a massive density of nodes that can be either human-held (user devices) or machine-type nodes (sensors). If we wish to properly serve these nodes and optimize their data, a proper wireless connection is fundamental. This can be achieved by using UAV-enabled communication and networks. This Special Issue addresses the many existing issues that still exist to allow UAV-enabled wireless communications and networking to be properly rolled out
Data Center-Enabled High Altitude Platforms: A Green Computing Alternative
Information technology organizations and companies are seeking greener
alternatives to traditional terrestrial data centers to mitigate global warming
and reduce carbon emissions. Currently, terrestrial data centers consume a
significant amount of energy, estimated at about 1.5% of worldwide electricity
use. Furthermore, the increasing demand for data-intensive applications is
expected to raise energy consumption, making it crucial to consider sustainable
computing paradigms. In this study, we propose a data center-enabled High
Altitude Platform (HAP) system, where a flying data center supports the
operation of terrestrial data centers. We conduct a detailed analytical study
to assess the energy benefits and communication requirements of this approach.
Our findings demonstrate that a data center-enabled HAP is more
energy-efficient than a traditional terrestrial data center, owing to the
naturally low temperature in the stratosphere and the ability to harvest solar
energy. Adopting a data center-HAP can save up to 14% of energy requirements
while overcoming the offloading outage problem and the associated delay
resulting from server distribution. Our study highlights the potential of a
data center-enabled HAP system as a sustainable computing solution to meet the
growing energy demands and reduce carbon footprint