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Mobile communication standards have been developed into a new era of B5G and 6G. In recent years, low earth orbit (LEO) satellites and space Internet have become hot topics. The integrated satellite and terrestrial systems have been widely discussed by industries and academics, and even are expected to be applied in those huge constellations in con...
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... Terminal integration, meaning UE has a unified identity in accessing and is controlled uniformly by the network without the integrated system as another example, as shown in Figure 3(b). To decrease the transmission delay, nodes of the core network can be deployed in every earth station, and earth stations connect to mobile communication network or terrestrial internet with the core network. ...
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... technologies for solving these challenges cover novel network architecture, unified air interface, massive MIMO, multiple access and NOMA, frequency sharing and interference management, etc. a) Novel network architecture As shown in Figure 3(a), 6G network will have a multi-layer architecture including at least user end (UE), satellite stations, terrestrial stations, and core network (CN). The satellite stations may include different types, such as GEO, MEO and LEO. ...
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... It is predicted that by 2027, more than 30 billion IoT devices will be deployed around the world [7]. Limited by geographical location, it is difficult for traditional terrestrial networks to provide reliable services for IoT devices in maritime areaa, remote areas, and other areas without terrestrial network coverage [8]. Therefore, non-terrestrial networks, unaffected by geographical limitations, can provide reliable wide-area coverage for terrestrial IoT devices, becoming a crucial direction for future network development. ...
High-altitude platform (HAP) drones and satellites collaborate to form a network that provides edge computing services to terrestrial internet of things (IoT) devices, which is considered a promising method. In this network, IoT devices’ tasks can be split into multiple parts and processed by servers at non-terrestrial nodes in different locations, thereby reducing task processing delays. However, splitting tasks and allocating communication and computing resources are important challenges. In this paper, we investigate the task offloading and resource allocation problem in multi-HAP drones and multi-satellite collaborative networks. In particular, we formulate a task splitting and communication and computing resource optimization problem to minimize the total delay of all IoT devices’ tasks. To solve this problem, we first transform and decompose the original problem into two subproblems. We design a task splitting optimization algorithm based on deep reinforcement learning, which can achieve online task offloading decision-making. This algorithm structurally designs the actor network to ensure that output actions are always valid. Furthermore, we utilize convex optimization methods to optimize the resource allocation subproblem. The simulation results show that our algorithm can effectively converge and significantly reduce the total task processing delay when compared with other baseline algorithms.
... Therefore, the new waveform requires good performance in high Doppler and low signal-to-noise ratio environments, and the existing OFDM waveform is considered to be modified to alleviate its instability in highmobility environments. The applicability of waveforms in satellite scenarios has been studied based on the cyclic prefix OFDM and discrete Fourier transform-spread OFDM waveforms [9,123]. Principle-based simulation validation studies on OFDM and other communication waveforms have been conducted within ISAC waveforms. ...
With the evolution of fifth-generation (5G) to sixth-generation (6G) communication systems, the utilization of spectrum resources faces incremental challenges. Integrated sensing and communication (ISAC) technology, as a crucial element in 6G technology, is expected to enhance energy efficiency and spectrum utilization efficiency by integrating radar and communication signals, achieving environmental awareness, and enabling scene interconnection. Simultaneously, to realize the vision of seamless coverage in 6G, research on integrated satellite-terrestrial communication has been prioritized. To integrate the advantages, ISAC for integrated satellite–terrestrial networks (ISTNs) in 6G has emerged as a potential research direction. This paper offers an extensive overview of the present state of key technologies for ISAC and the development of ISTNs. Meanwhile, with a focus on the ISTN-oriented 6G ISAC system, several hotspot topics, including future application scenarios and key technological developments, are outlined and demonstrated.
... Research [42][43][44] discussed the necessity of satellite communication in the future and introduced relevant satellite communication technologies. UAVs, HAPs, and other aircraft are crucial components of the 6G air network. ...
Vehicular Ad-hoc Networks (VANETs) have enabled intelligent transportation systems by facilitating communication between vehicles and roadside infrastructure. However, the current 5G and 4G networks that support VANETs have certain limitations that hinder the full potential of VANET applications. These limitations include constraints in bandwidth, latency, connectivity, and security. The upcoming 6G network is expected to revolutionize VANETs by introducing several advancements. 6G will provide ultra-fast communication with significantly reduced latency, enabling real-time and high-bandwidth data exchange between vehicles. The network will also offer highly reliable and secure connectivity, ensuring the integrity and privacy of VANET communications. Precise localization and sensing capabilities will be enhanced in 6G-based VANETs, enabling accurate positioning of vehicles and improved situational awareness. This will facilitate collision avoidance, traffic management, and cooperative driving applications. Moreover, integrating edge computing in 6G networks will bring computing resources closer to the edge, lowering response times and facilitating faster decision-making in time-critical scenarios. This paper explores the key features and capabilities of 6G technology and how it can revolutionize intelligent transportation, addressing challenges and opportunities for adopting 6G in VANETs.
... N the recent decades, the burgeoning demands of high data throughput in the fifth-generation (5G) and even future the sixth-generation (6G) wireless mobile communication systems have promoted the blossom of diverse millimeterwave (mmWave) applications, such as customer premise equipment (CPE), base station, mobile terminal and so forth, as shown in Fig. 1. The mmWave wireless technology owns a higher data bit-rate beyond Gbps and a higher spectrum utilization in comparison with the low frequency bands below 6GHz (sub-6 GHz), which is a research hotspot in both academia and industry [1], [2]. The third generation partnership project (3GPP) has defined the licensed mmWave bands for 5G communication, which mainly includes the n258 (24.25-27.50 ...
A new taper-shaped linearly polarized (LP) magneto-electric (ME) dipole, excited by the U-shaped microstrip line through a coupling slot, is proposed in this paper. An ultra-wide simulated impedance bandwidth of 85% (20.5-50.6 GHz) and 1.5-dB gain bandwidth of 73% (22.3-47.9 GHz) with a peak gain up to 7.7 dBi are achieved, combining the advantages of simple and compact structure, high integration, easy assembling and stable radiation characteristics. For proof-of-concept demonstration, a 4 × 4 LP array antenna is then implemented with an ultra-wide measured impedance bandwidth of 91.8% (18.8-50.7 GHz) and 3-dB gain bandwidth of 69.3% (19.8 to 40.8 GHz) as well as a peak gain of 18.0 dBi. Subsequently, the LP element is conveniently extended to a dual-polarized (DP) one due to its 90∘ rotationally symmetrical structure, exhibiting a wide simulated overlapped bandwidth of 61.4% (23.7-44.7 GHz), port isolation exceeding 17 dB and a stable gain response with a peak gain of 7.5 dBi. Furthermore, two 1×4 DP active phased array antennas (APAAs) are designed by utilizing the integrated circuits (ICs) for 5G/6G millimeter-wave (mmWave) mobile terminal applications. Meanwhile, the beam-scanning performances at 28-and 38-GHz are measured for both polarizations. The validated advantages render the proposed antenna designs competitive candidates for diverse 5G/6G mmWave applications.
... The majority of the related literature concerns the conventional terrestrial-satellite integration that has started already in 2G communication systems and has now accelerated in 5G systems. While in 2G systems, the integration target was quite modest to support some simple dual operations between satellite and terrestrial systems, the integration target in 5G and 6G is to make satellite links more comprehensively compatible with that of the terrestrial system and to identify ways to tolerate the distinctive features of satellite links [9,22,24,25]. ...
Satellite communications systems provide a means to connect people and devices in hard-to-reach locations. Traditional geostationary orbit (GEO) satellite systems and low Earth orbit (LEO) constellations, having their own strengths and weaknesses, have been used as separate systems serving different markets and customers. In this article, we analyze how satellite systems in different orbits could be integrated together and used as a multi-layer satellite system (MLSS) to improve communication services. The optimization concerns combining the strengths of different layers that include a larger coverage area as one moves up by each layer of altitude and a shorter delay as one moves down by each layer of altitude. We review the current literature and market estimates and use the information to provide a thorough assessment of the economic, regulatory, and technological enablers of the MLSS. We define the MLSS concept and the architecture and describe our testbed and the simulation tools used as a comprehensive engineering proof-of-concept. The validation results confirm that the MLSS approach can intelligently exploit the smaller jitter of GEO and shorter delay of LEO connections, and it can increase the availability and resilience of communication services. As a main conclusion, we can say that multi-layered networks and the integration of satellite and terrestrial segments seem very promising candidates for future 6G systems.
... To meet the demands, non-terrestrial networks (NTNs) have been introduced as part of sixth-generation (6G) technologies, enabling communication from urban centers to remote areas [4,5]. The integrated air and terrestrial systems have been widely discussed by industries and academics [6]. Non-terrestrial network refers to networks, or segments of networks, that use an airborne or spaceborne vehicle for transmission, including satellites, high-altitude platform (HAP) stations, unmanned aircraft vehicles (UAVs), and so on [7]. ...
High-altitude platforms (HAPs) are considered to be the most important equipment for next-generation wireless communication technologies. In this paper, we investigate the channel characteristics under the configurations of massive multiple-input multiple-output (MIMO) space and large bandwidth at millimeter-wave (mmWave) bands, along with the moving essence of the HAP and ground terminals. A non-stationary three-dimensional (3D) geometry-based stochastic model (GBSM) is proposed for a HAP communication system. We use a cylinder-based geometric modeling method to construct the channel and derive the channel impulse response (CIR). Additionally, the birth–death process of the scatterers is enclosed using the Markov process. Large-scale parameters such as free space loss and rainfall attenuation are also taken into consideration. Due to the relative motion between HAP and ground terminals, the massive MIMO space, and the wide bandwidth in the mmWave band, the channel characteristics of HAP exhibit non-stationarities in time, space, and frequency domains. By deriving the temporal auto-correlation function (ACF), we explore the non-stationarity in the time domain and the impact of various parameters on the correlations across the HAP-MIMO channels. The spatial cross-correlation function (CCF) for massive MIMO scenarios, and the frequency correlation function (FCF) in the mmWave bands are also considered. Moreover, we conduct simulation research using MATLAB. Simulation results show that the theoretical results align well with the simulation results, and this highlights the fact that the constructed 3D GBSM can characterize the non-stationary characteristics of HAP-MIMO channels across the time, space, and frequency domains.
... Due to limitations in the coverage of ground information networks, they struggle to meet the wireless access demands in various scenarios, especially in areas such as mountains, oceans, and deserts where infrastructure development is lacking. In comparison, SATellite (SAT) networks possess extensive coverage and can compensate for the shortcomings of ground networks [1][2][3]. Additionally, aerial nodes such as Unmanned Aerial Vehicles (UAVs) and airships can provide instant network access services for devices that are distant from terrestrial information networks [4][5][6]. Therefore, 6G networks are gradually evolving towards the direction of Space-Air-Ground integrated networks [6,7]. ...
One of the goals of the sixth generation mobile networks (6G) is to achieve a larger network coverage area. Satellite networks enable global coverage, and aerial nodes such as Unmanned Aerial Vehicle (UAV) can serve as a supplement to ground networks in remote environments. Therefore, 6G networks are gradually evolving towards a Space-Air-Ground integrated networks. The combination of UAV networks and satellite networks is a research hotspot in the field of Space-Air integrated networks. However, the combination of UAV networks and satellite networks currently faces many challenges in terms of security. The characteristics of large propagation delay and unstable communication links in satellite networks make them vulnerable to various attacks, including eavesdropping, tampering, and impersonation. Meanwhile, existing research on UAV networks mainly focuses on UAV-Ground networking authentication mechanisms, which are not suitable for resource-constrained nodes in the Space-Air integration scenario. Therefore, based on elliptic curve public key cryptography and Chebyshev polynomial, we propose a secure networking authentication scheme for satellite nodes and UAV nodes in the Space-Air integration scenario. The security analysis indicates that our scheme possesses the security attributes such as mutual authentication, key agreement, identity anonymity, unlinkability, perfect forward-backward security and resistance against various protocol attacks, among other security properties. Performance analysis also indicates certain advantages of our scheme over existing schemes in terms of signaling, bandwidth, and computational overhead.
... T HE increasing demand for bandwidth in wireless communications has spurred the rapid development of satellite networks. A prevailing trend in the space sector is the deployment of numerous satellite constellations that allow for increasing user bandwidth [1], [2]. With the electromagnetic spectrum becoming more crowded, antennas for these links must meet various specifications, such as high efficiency, robust designs in hostile environments, compact size, or reduced sidelobes. ...
This paper showcases advancements in metallic array antennas tailored for mm-wave applications, supported by novel highly compact unbalanced dividers conceived in Ridge Gap Waveguide (RGW) technology. This innovative approach streamlines the feeding network by enabling high-weight-ratio dividers without adding design complexity. The study presents an
$8\times 8$
Ka-band antenna array employing Taylor amplitude tapering and featuring a compact corporate-fed design that effectively mitigates coupling effects between the feeding network and radiating elements. Experimental results highlight promising characteristics, boasting a matching better than
$-$
10 dB across the entire band of interest (29-31 GHz) and secondary lobes below
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20 dB while achieving a radiation efficiency exceeding 82%.
... In the past few decades, satellite and terrestrial networks typically developed independently and competed with each other [3]. Although the terrestrial network is advantageous in terms of high-speed data transmission and low latency, its coverage is limited, covering only about 6% of the Earth's surface and about 20% of the land area [4]. ...
Traditional low earth orbit (LEO) satellite networks are typically independent of terrestrial networks, which develop relatively slowly due to the on-board capacity limitation. By integrating emerging mobile edge computing (MEC) with LEO satellite networks to form the business-oriented “end-edge-cloud” multi-level computing architecture, some computing-sensitive tasks can be offloaded by ground terminals to satellites, thereby satisfying more tasks in the network. How to make computation offloading and resource allocation decisions in LEO satellite edge networks, nevertheless, indeed poses challenges in tracking network dynamics and handling sophisticated actions. For the discrete-continuous hybrid action space and time-varying networks, this work aims to use the parameterized deep Q-network (P-DQN) for the joint computation offloading and resource allocation. First, the characteristics of time-varying channels are modeled, and then both communication and computation models under three different offloading decisions are constructed. Second, the constraints on task offloading decisions, on remaining available computing resources, and on the power control of LEO satellites as well as the cloud server are formulated, followed by the maximization problem of satisfied task number over the long run. Third, using the parameterized action Markov decision process (PAMDP) and P-DQN, the joint computing offloading, resource allocation, and power control are made in real time, to accommodate dynamics in LEO satellite edge networks and dispose of the discrete-continuous hybrid action space. Simulation results show that the proposed P-DQN method could approach the optimal control, and outperforms other reinforcement learning (RL) methods for merely either discrete or continuous action space, in terms of the long-term rate of satisfied tasks.
... A very relevant branch of the literature is mainly focused on securing physical layers on heterogeneous networks [60,61]. Continuing the discourse, major improvements in the reliability of the solutions analyzed may be the implementation of satellite communication leading to the research undergoing for the sixth generation of cellular networks [62]. While this technology augments communication coverage, it introduces the need for meticulous implementation of encryption and authentication protocols [63]. ...
The increasing usage of autonomous and automatic systems within the automotive industry is steering us towards a more interconnected world. This enhanced interconnectivity fosters a more streamlined driving experience, reduces costs, and provides timely driver assistance. The electric/electronic (EE) architectures of modern vehicles are inherently complex due to the multitude of components they encompass. Contemporary architectures reveal that these components converge at an electronic control unit (ECU) called the central gateway, which could potentially represent a single point of failure. While this central unit is typically adequately safeguarded, the same cannot be said for the connected components, which often remain vulnerable to cyber threats. The ISO/SAE 21434 standard paved the way for automotive cybersecurity and could be used in parallel with other standards such as ISO 26262 and ISO PAS 21488. Automatic collision notification (ACN) is one of the most typical systems in a vehicle, and limited effort has been dedicated to identifying the most suitable architecture for this feature. This paper addresses the existing security and privacy gap of this feature by conducting a comparative analysis of security threats in two distinct ACN architectures. Notably, despite ACN architectures exhibiting inherent similarities, the primary distinction between the two architectures lies in their strategies for crash estimation and detection, followed by subsequent communication with emergency response teams. A rigorous security assessment was conducted using the ISO/SAE 21434 standard, employing the TARA and STRIDE methodologies through the Ansys medini analyze software. This analysis identified an average of 310 threats per architecture, including a significant number of high-level threats (11.8% and 15%, respectively), highlighting the importance of a comprehensive evaluation.
