477 research outputs found
The Role of Physical Layer Security in Satellite-Based Networks
In the coming years, 6G will revolutionize the world with a large amount of
bandwidth, high data rates, and extensive coverage in remote and rural areas.
These goals can only be achieved by integrating terrestrial networks with
non-terrestrial networks. On the other hand, these advancements are raising
more concerns than other wireless links about malicious attacks on
satellite-terrestrial links due to their openness. Over the years, physical
layer security (PLS) has emerged as a good candidate to deal with security
threats by exploring the randomness of wireless channels. In this direction,
this paper reviews how PLS methods are implemented in satellite communications.
Firstly, we discuss the ongoing research on satellite-based networks by
highlighting the key points in the literature. Then, we revisit the research
activities on PLS in satellite-based networks by categorizing the different
system architectures. Finally, we highlight research directions and
opportunities to leverage the PLS in future satellite-based networks
Joint Beamforming and Power Allocation for Satellite-Terrestrial Integrated Networks With Non-Orthogonal Multiple Access
In this paper, we propose a joint optimization design for a non-orthogonal multiple access (NOMA)-based satellite-terrestrial integrated network (STIN), where a satellite multicast communication network shares the millimeter wave spectrum with a cellular network employing NOMA technology. By assuming that the satellite uses multibeam antenna array and the base station employs uniform planar array, we first formulate a constrained optimization problem to maximize the sum rate of the STIN while satisfying the constraint of per-antenna transmit power and quality-of-service requirements of both satellite and cellular users. Since the formulated optimization problem is NP-hard and mathematically intractable, we develop a novel user pairing scheme so that more than two users can be grouped in a cluster to exploit the NOMA technique. Based on the user clustering, we further propose to transform the non-convex problem into an equivalent convex one, and present an iterative penalty function-based beamforming (BF) scheme to obtain the BF weight vectors and power coefficients with fast convergence. Simulation results confirm the effectiveness and superiority of the proposed approach in comparison with the existing works
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges
With the rapid development of marine activities, there has been an increasing
number of maritime mobile terminals, as well as a growing demand for high-speed
and ultra-reliable maritime communications to keep them connected.
Traditionally, the maritime Internet of Things (IoT) is enabled by maritime
satellites. However, satellites are seriously restricted by their high latency
and relatively low data rate. As an alternative, shore & island-based base
stations (BSs) can be built to extend the coverage of terrestrial networks
using fourth-generation (4G), fifth-generation (5G), and beyond 5G services.
Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs.
Despite of all these approaches, there are still open issues for an efficient
maritime communication network (MCN). For example, due to the complicated
electromagnetic propagation environment, the limited geometrically available BS
sites, and rigorous service demands from mission-critical applications,
conventional communication and networking theories and methods should be
tailored for maritime scenarios. Towards this end, we provide a survey on the
demand for maritime communications, the state-of-the-art MCNs, and key
technologies for enhancing transmission efficiency, extending network coverage,
and provisioning maritime-specific services. Future challenges in developing an
environment-aware, service-driven, and integrated satellite-air-ground MCN to
be smart enough to utilize external auxiliary information, e.g., sea state and
atmosphere conditions, are also discussed
Reconfigurable Intelligent Surfaces for 6G Non-Terrestrial Networks: Assisting Connectivity from the Sky
This paper studies the potential of RIS-integrated NTNs to revolutionize the
next-generation connectivity. First, it discusses the fundamentals of RIS
technology. Secondly, it delves into reporting the recent advances in
RIS-enabled NTNs. Subsequently, it presents a novel framework based on the
current state-of-the-art for low earth orbit satellites (LEO) communications,
wherein the signal received at the user terminal traverses both a direct link
and an RIS link, and the RIS is mounted on a high-altitude platform (HAP)
situated within the stratosphere. Finally, the paper concludes by highlighting
open challenges and future research directions to revolutionize the realm of
RIS-integrated NTNs.Comment: 6,
Evaluation of multi-user multiple-input multiple-output digital beamforming algorithms in B5G/6G low Earth orbit satellite systems
Satellite communication systems will be a key component of 5G and 6G networks to achieve the goal of providing unlimited and ubiquitous communications and deploying smart and sustainable networks. To meet the ever-increasing demand for higher throughput in 5G and beyond, aggressive frequency reuse schemes (i.e., full frequency reuse), combined with digital beamforming techniques to cope with the massive co-channel interference, are recognized as a key solution. Aimed at (i) eliminating the joint optimization problem among the beamforming vectors of all users, (ii) splitting it into distinct ones, and (iii) finding a closed-form solution, we propose a beamforming algorithm based on maximizing the users' signal-to-leakage-and-noise ratio served by a low Earth orbit satellite. We investigate and assess the performance of several beamforming algorithms, including both those based on channel state information at the transmitter, that is, minimum mean square error and zero forcing, and those only requiring the users' locations, that is, switchable multi-beam. Through a detailed numerical analysis, we provide a thorough comparison of the performance in terms of per-user achievable spectral efficiency of the aforementioned beamforming schemes, and we show that the proposed signal to-leakage-plus-noise ratio beamforming technique is able to outperform both minimum mean square error and multi-beam schemes in the presented satellite communication scenario
Robust Secure Precoding for UAV-Aided Multi-beam Satellite NOMA Communications
The wide coverage and broadcasting characteristics of satellite communications lead to multi-beam downlinks being vulnerable to security threats, such as eavesdropping, hacking and illegal access. This paper takes into account the case of multiple users and an eavesdropper (Eve) in the target beam. In particular, we consider the deployment of an unmanned aerial vehicle to generate artificial noise in order to confuse Eve, while acting as a relay for the legitimate users. In addition, a nonorthogonal multiple access (NOMA) strategy is used to support multi-user communication and to improve the transmission rate. Considering the constraints due to quality of service, total and per-beam transmit power of the satellite, two robust secure precoding algorithms are presented to maximize the minimal achievable secrecy rate of the legitimate users for both noncritical and critical applications. Since the formulated optimization problems are non-convex, we first use the arithmeticgeometric mean inequality to solve the non-convex constraint of the successive interference cancellation decoding order, and the logarithmic parameter form is addressed by using the first-order Taylor series expansion. Besides, the secure outage probability constraint of the critical case is effectively resolved by applying the Bernstein-type inequality/decomposition-based large deviation inequality. Moreover, semi-definite relaxation and penalty function optimization methods are adopted to design the transmit power of the satellite in two cases, respectively. Simulation results verify the effectiveness and superiority of the proposed robust precoding design methods
Self-Evolving Integrated Vertical Heterogeneous Networks
6G and beyond networks tend towards fully intelligent and adaptive design in
order to provide better operational agility in maintaining universal wireless
access and supporting a wide range of services and use cases while dealing with
network complexity efficiently. Such enhanced network agility will require
developing a self-evolving capability in designing both the network
architecture and resource management to intelligently utilize resources, reduce
operational costs, and achieve the coveted quality of service (QoS). To enable
this capability, the necessity of considering an integrated vertical
heterogeneous network (VHetNet) architecture appears to be inevitable due to
its high inherent agility. Moreover, employing an intelligent framework is
another crucial requirement for self-evolving networks to deal with real-time
network optimization problems. Hence, in this work, to provide a better insight
on network architecture design in support of self-evolving networks, we
highlight the merits of integrated VHetNet architecture while proposing an
intelligent framework for self-evolving integrated vertical heterogeneous
networks (SEI-VHetNets). The impact of the challenges associated with
SEI-VHetNet architecture, on network management is also studied considering a
generalized network model. Furthermore, the current literature on network
management of integrated VHetNets along with the recent advancements in
artificial intelligence (AI)/machine learning (ML) solutions are discussed.
Accordingly, the core challenges of integrating AI/ML in SEI-VHetNets are
identified. Finally, the potential future research directions for advancing the
autonomous and self-evolving capabilities of SEI-VHetNets are discussed.Comment: 25 pages, 5 figures, 2 table
Hybrid satellite–terrestrial networks toward 6G : key technologies and open issues
Future wireless networks will be required to provide more wireless services at higher data rates and with global coverage. However, existing homogeneous wireless networks, such as cellular and satellite networks, may not be able to meet such requirements individually, especially in remote terrain, including seas and mountains. One possible solution is to use diversified wireless networks that can exploit the inter-connectivity between satellites, aerial base stations (BSs), and terrestrial BSs over inter-connected space, ground, and aerial networks. Hence, enabling wireless communication in one integrated network has attracted both the industry and the research fraternities. In this work, we provide a comprehensive survey of the most recent work on hybrid satellite–terrestrial networks (HSTNs), focusing on system architecture, performance analysis, design optimization, and secure communication schemes for different cooperative and cognitive HSTN network architectures. Different key technologies are compared. Based on this comparison, several open issues for future research are discussed
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