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Non-orthogonal multiple access (NOMA) has the potential to provide higher throughput than conventional orthogonal multiple access (OMA), which has been considered as a key technology for 5G. NOMA in satellite communication system can provide anytime, anywhere access with improved spectral efficiency and system capacity because of its ubiquitous cov...
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... visibility window, when we set the orbital altitude h = 600, 900 and 1200 km, the Doppler shift characterization curve is presented in Fig. 3 and the distance between LEO satellite and users is presented in Fig. 4. From these figures, we can get that the visible time increases with the orbital altitude. The change rate of the Doppler shift and the distance between LEO satellite and users decrease as the orbital altitude h ...
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Citations
... 2021 [111] Performance evaluation of the NOMA-based LEO satellite in the downlink scenario. 2020 [112] Based on 3GPP specifications, the limitations of the NTN on the New Radio (NR) approach were considered for purposes of supporting the future 6G-NTN system technology. ...
Until now many regions around the world are still uncovered by cellular terrestrial mobile system services due to the lack of economic feasibility as well as the difficulty of introducing such services. Conversely, a large geographic region can be covered by using only a single satellite, so it is worthwhile to extend the actual terrestrial services using satellite system. The new hybrid integrated “terrestrial-satellite” cellular system, known under the name of Non-Terrestrial Networks (NTN), will see the light with the support of future 6G technology. It is expected that 6G cellular mobile system will play the role of integrating terrestrial, aerial, maritime, and space communications into a universal network that could support a massive number of terminals with ultra-low latency. For the realization of the NTN system, new technologies should be introduced at the level of terrestrial cellular network, arial network, and satellite network. One of these promising technologies is represented by an efficient multiplexing technique known under the name of non-orthogonal multiple access (NOMA). With this technique, multiple users can be served on a single time-frequency resource block by using the concepts of superposition coding at the transmitter and successive interference cancellation (SIC) at the receiver. Moreover, NOMA has an achievable performance gain in terms of spectral efficiency over the traditional orthogonal multiple access (OMA) technique. Evaluation of a NOMA-based NTN system supported by 6G technologies in terms of system parameters and channel capacity represent the main objective of this paper.
... Integration of a rental service was proposed in [13] to enhance resource utilization, while [14] introduced a massive MIMO transmission technique with full frequency reuse to overcome instantaneous channel state information (CSI) challenges. In dynamic satellite networks, [15] explored the influence of the Doppler effect on the performance of NOMA downlink and suggested NOMA with OFDM for improved spectrum efficiency. Furthermore, a multi-satellite tracking technique for ship-borne digital phased arrays was presented in [16]. ...
Satellite systems face a significant challenge in effectively utilizing limited communication resources to meet the demands of ground network traffic, characterized by asymmetrical spatial distribution and time-varying characteristics. Moreover, the coverage range and signal transmission distance of low Earth orbit (LEO) satellites are restricted by notable propagation attenuation, molecular absorption, and space losses in sub-terahertz (THz) frequencies. This paper introduces a novel approach to maximize LEO satellite coverage by leveraging reconfigurable intelligent surface (RIS) within 6G sub-THz networks. Optimization objectives include improving end-to-end (E2E) data rate, optimizing satellite-remote user equipment (RUE) associations, data packet routing within satellite constellations, RIS phase shift, and ground base station (GBS) transmit power (i.e., active beamforming). The formulated joint optimization problem poses significant challenges because of its time-varying environment, non-convex characteristics, and NP-hard complexity. To address these challenges, we propose a block coordinate descent (BCD) algorithm that integrates balanced K-means clustering, multi-agent proximal policy optimization (MAPPO) deep reinforcement learning (DRL), and whale optimization algorithm (WOA) techniques. The performance of the proposed approach is demonstrated through comprehensive simulation results, demonstrating its superiority over existing baseline methods in the literature.
... The non-orthogonal multiple access (NOMA)-based space-air-ground integrated network (SAGIN) has recently gained increasing attention for its role in enhancing channel capability, expanding communication coverage, and improving system performance [1,2]. Several studies, such as [3][4][5], have explored the outage probability, average bit error rate, and ergodic capacity of NOMA-based SAGIN systems. However, with the recent increase in communication coverage, the vulnerability of the SAGIN system signal to attacks has become a concern, prompting a heightened focus on signal security for NOMAbased SAGIN. ...
Recently, non-orthogonal multiple access (NOMA)-based space–air–ground integrated networks (SAGINs) have gained increasing attention due to their robust communication, broader coverage, and resource-saving advantages. However, it is imperative to consider physical layer security as a crucial performance metric in NOMA-based SAGINs. This study addresses this concern by constructing a NOMA-based free space optical (FSO)/radio frequency (RF) dual-hop SAGIN system with eavesdroppers on both links. The two new fading channel models were proposed, considering the FSO link’s fog absorption and the RF link’s stochastic distribution based on Málaga and shadowed Rician distributions. The closed-form expressions for the secrecy outage probability are derived for the SAGIN system. Monte Carlo simulations were conducted to validate the theoretical findings. The results revealed the influence of fog absorption and the stochastic geometry distribution on the SAGIN system.
... In this section, numerical results are provided to present the system performance including BCP (P cov ), SOP (P sop ) and overall system SOP (P all ) under those two scenarios, and some parameters affecting the system performance are also discussed. The relevant parameter settings for the satellite link are shown in Table II [37], [46], and those for the underwater turbulence are shown in Tables III and IV [18]. In addition, it sets m = 1, d = 0.063, Ω = 0.0007, and R s = 0.1 bits/s/Hz. ...
In this work, the physical-layer security for a maritime relay-assisted hybrid satellite and underwater wireless optical communication system consisting of a satellite source, a maritime relay (R), an underwater destination, and an eavesdropper (E) is investigated. In addition, both R and E are with multiple antennas and randomly located. In real application scenarios, E may be different carriers, i.e., an aircraft in the air or a ship on the sea, with various scopes of activity. Therefore, two different randomly located scenarios are considered, such as randomly distributed in a three dimensional space and a two dimensional plane. Furthermore, the beam-angle information of the source is assumed to be unavailable to E, and E may be located outside of the beam coverage area. Therefore, the beam coverage probability (BCP) for E is also presented. Employing the stochastic geometry theory and the maximum ratio combining scheme, the analytical and asymptotic expressions of secrecy outage probability (SOP) are obtained. In addition, the overall system SOP is defined and presented by taking both SOP and BCP into account. Finally, Monte-Carlo simulations verify the accuracy of our analysis.
... An unmanned aerial vehicle space-ground-air integral relay network was proposed [34], where the NOMA-assisted unmanned aerial vehicle was equipped with a phased array antenna to receive satellite signals. According to the advantages of the downlink NOMA-BH in LEO satellite systems, Gao et al. [35] investigated the ergodic capacity, the outage probability, and mutual information of two users in a spot beam. As further achieving nonorthogonality in power and frequency domains of the BH network [36], the design of bandwidth compression was embedded in the NOMA scheme. ...
... REMARK 4 Upon substituting (35) and (36) into (28), the diversity orders of the user m with ipCSI/pCSI for the PD-NOMA-BH system are 0 and 1, respectively. We can observe the abovementioned remarks that the CD-NOMA-BH system have multicarrier effect and obtain upper diversity order than the PD-NOMA-BH system. ...
This paper investigates the application of a unified non-orthogonal multiple access framework in beam hopping (U-NOMA-BH) based satellite communication systems. More specifically, the proposed U-NOMA-BH framework can be applied to code-domain NOMA based BH (CD-NOMA-BH) and power-domain NOMA based BH (PD-NOMA-BH) systems. To satisfy dynamic-uneven traffic demands, we formulate the optimization problem to minimize the square of discrete difference by jointly optimizing power allocation, carrier assignment and beam scheduling. The non-convexity of the objective function and the constraint condition is solved through Dinkelbach's transform and variable relaxation. As a further development, the closed-from and asymptotic expressions of outage probability are derived for CD/PD-NOMA-BH systems. Based on approximated results, the diversity orders of a pair of users are obtained in detail. In addition, the system throughput of U-NOMA-BH is discussed in delay-limited transmission mode. Numerical results verify that: i) The gap between traffic requests of CD/PD-NOMA-BH systems appears to be more closely compared with orthogonal multiple access based BH (OMA-BH); ii) The CD-NOMA-BH system is capable of providing the enhanced traffic request and capacity provision; and iii) The outage behaviors of CD/PD-NOMA-BH are better than that of OMA-BH.
... Integration of a rental service was proposed in [13] to enhance resource utilization, while [14] introduced a massive MIMO transmission technique with full frequency reuse to overcome instantaneous channel state information (CSI) challenges. In dynamic satellite networks, [15] explored the influence of the Doppler effect on downlink NOMA performance and suggested NOMA with OFDM for improved spectrum efficiency. Additionally, a multi-satellite tracking technique for shipborne digital phased arrays was presented in [16]. ...
Satellite systems face a significant challenge in effectively utilizing limited communication resources to meet the demands of ground network traffic, characterized by asymmetrical spatial distribution and time-varying characteristics. Moreover, the coverage range and signal transmission distance of low Earth orbit (LEO) satellites are restricted by notable propagation attenuation, molecular absorption, and space losses in sub-terahertz (THz) frequencies. This paper introduces a novel approach to maximize LEO satellite coverage by leveraging reconfigurable intelligent surfaces (RISs) within 6G sub-THz networks. The optimization objectives encompass enhancing the end-to-end data rate, optimizing satellite-remote user equipment (RUE) associations, data packet routing within satellite constellations, RIS phase shift, and ground base station (GBS) transmit power (i.e., active beamforming). The formulated joint optimization problem poses significant challenges owing to its time-varying environment, non-convex characteristics, and NP-hard complexity. To address these challenges, we propose a block coordinate descent (BCD) algorithm that integrates balanced K-means clustering, multi-agent proximal policy optimization (MAPPO) deep reinforcement learning (DRL), and whale optimization (WOA) techniques. The performance of the proposed approach is demonstrated through comprehensive simulation results, exhibiting its superiority over existing baseline methods in the literature.
... A power-domain NOMA scheme for the downlink of an integrated satellite-terrestrial network was considered in [3], targeted at IoT applications. With particular reference to LEO constellations, the performance analysis of downlink NOMA is carried out in [9], in terms of ergodic capacity, outage probability, and mutual information, by considering the case of two ground users in one spot beam. ...
... In [11], a NOMA scheme has been introduced in uplink, in the context of a multi-layer satellite networks, composed by GEO and LEO satellites. The works [3], [9]- [11] do not consider intersatellite (IS) communication at all. ...
Communication between satellites in low-Earth orbit (LEO) constellations takes place through intersatellite links (ISLs). Unlike intra-plane ISLs, which interconnect satellites belonging to the same orbital plane with fixed relative distance, inter-plane ISLs experience significant Doppler frequency shifts, since satellites belonging to different orbital planes exhibit time-varying relative distance (required, e.g., to minimize the risk of physical collisions between satellites). In this paper, we consider the problem of connecting multiple satellites, belonging a massive LEO Walker Delta constellation, to a receiving satellite, referred to as the sink. Specifically, we consider a hybrid multiple access scheme, which employs a combination of non-orthogonal multiple access (NOMA), where ISLs share the same time-frequency resource blocks, and orthogonal multiple access (OMA), where ISLs employs orthogonal resource blocks. To this aim, the set of satellites transmitting towards the sink is divided into groups, where NOMA is employed within each group, whereas OMA is used to separate different groups. Such a scheme subsumes as special cases both pure-OMA and pure-NOMA. Our study highlights that similar Doppler frequency shifts have a large impact on the individual rates of the satellites in a pure-NOMA scheme, thus reducing the network fairness of this technique. Motivated by such a fact, we develop design strategies of the proposed hybrid NOMA-OMA scheme, which exploit inter-plane Doppler frequency diversity to enhance fairness among the satellites, while ensuring a significantly higher sum-rate capacity compared to the pure-OMA technique. Numerical results corroborate our theoretical analysis, by demonstrating both the fairness enhancement of the proposed techniques over the pure-NOMA scheme, as well as their capacity improvement over the pure-OMA one.
... Non-orthogonal multiple access (NOMA) has the potential to provide higher throughput than traditional orthogonal multiple access (OMA), which has been thought of as a key technology for SATCOM networks [71]. NOMA uses transmitter precoding to distinguish power domain users. ...
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 fifth generation and beyond wireless 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 user friendly 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.
... Optical Communication [57], [90], [91], [92], [93], [94], [96], [97], [98], [99], [100], [101], [102], [103], [104], [105], [106] , [107], [108], [109], [110] THz Communication [111], [112], [113], [114], [115], [116], [117], [118], [119], [120], [121], [122], [123], [124] RIS [125], [126], [127], [128], [129], [130], [131] Multiple Spacecraft & Uplink per Antenna [132], [133], [134] Mars Planetary Network [57], [58], [135], [136], [137], [138], [139], [140], [141], [142] Cognitive Radio [143], [144], [145], [146], [147], [148], [149], [150], [151], [152], [153], [154], [155], [156], [157], [158], [159] Acquisition, Tracking, and Navigation [160], [161], [162], [163], [164], [165], [166], [167] Delay Tolerant Networking [5], [168], [169], [170], [171], [172], [173], [174], [175], [176], [177], [178], [179], [180], [181], [182] , [183], [184], [185], [186], [187], [188], [189], [190] Multiple Access Schemes [191], [192], [193], [194], [195], [196], [197], [198], [199], [200], [201], [202], [203], [204] Environment-Aware Communications [205], [206], [207], [208] Artificial Intelligence [209], [210], [211], [212], [213], [214], [215], [216], [217], [218], [219] User Modem and Amplifier Terminal (ILLUMA-T), which is expected to be released in 2023 and complete an end-to-end (E2E) optical communications relay system. High-resolution data is envisioned to be transmitted from the International Space Station (ISS) to the LCRD using 1.2 Gbps optical links. ...
... In a NOMA-based GEO and LEO satellite network, [199] examined a joint user pairing and power allocation system, which can be helpfull in areostationary relay-orbiter networks on Mars. Additionaly, [200] investigated the performance of NOMA with LEO satellites taking into account the Doppler shift. [201] takes into account the utilization of RIS in NOMA, where a base station sends superposed signals to several users with the help of a RIS. ...
Space exploration has been on the rise since the 1960s. Along with the other planets such as Mercury, Venus, Saturn, and Jupiter, Mars certainly plays a significant role in the history of space exploration and has the potential to be the first extraterrestrial planet to host human life. In this context, tremendous effort has been put into developing new technologies to photograph, measure, and analyze the red planet. As the amount of data collected from science instruments around and on Mars increased, the need for fast and reliable communication between Earth and space probes has emerged. However, communicating over deep space has always been a big challenge due to the propagation characteristics of radio waves. Nowadays, the collaboration of private companies like SpaceX with space agencies to make Mars colonization a reality, introduces even more challenges, such as providing high data rate, low latency, energy-efficient, reliable, and mobility-resistant communication infrastructures in the Martian environment. Propagation medium and wireless channel characteristics of Mars should be extensively studied to achieve these goals. This survey article presents a comprehensive overview of the Mars missions and channel modeling studies of the near-Earth, interstellar, and near-planet links. Studies featuring three-dimensional (3D) channel modeling simulations on the Martian surface are also reviewed. We have also presented our own computer simulations considering various scenarios based on realistic 3D Martian terrains using the Wireless Insite software. Path loss exponent, power delay profile, and root-mean-square delay spread for these scenarios are calculated and tabularized in this study. Furthermore, future insights on emerging communication technologies for Mars are given.
... A whole plethora of other NOMA solutions can be found in [53,142]. However, it becomes a potential challenge to design advanced NOMA techniques in terms of integrating the diverse resource domains of mmWave/THz systems [54,267], cancelling the interference in UDNs, or enhancing the coverage area of UAV and satellite networks [73,109]. • 3D Beamforming: This concept emerges from that of sectorized antennas aiming for serving users roaming at different angles with the aid of sophisticated beamforming techniques and antenna configurations. Since mmWave carriers suffer from excessive pathloss, the employment of high-gain beamforming is critical. ...
Whilst the fifth-generation (5G) systems are being rolled out across the globe, researchers have turned their attention to the exploration of radical next-generation solutions. At this early evolutionary stage we survey five main research facets of this field, namely Facet 1: next-generation architectures, spectrum and services, Facet 2: next-generation networking, Facet 3: Internet of Things (IoT), Facet 4: wireless positioning and sensing, as well as Facet 5: applications of deep learning in 6G networks. In this paper, we have provided a critical appraisal of the literature of promising techniques ranging from the associated architectures, networking, applications as well as designs. We have portrayed a plethora of heterogeneous architectures relying on cooperative hybrid networks supported by diverse access and transmission mechanisms. The vulnerabilities of these techniques are also addressed and carefully considered for highlighting the most of promising future research directions. Additionally, we have listed a rich suite of learning-driven optimization techniques. We conclude by observing the evolutionary paradigm-shift that has taken place from pure single-component bandwidth-efficiency, power-efficiency or delay-optimization towards multi-component designs, as exemplified by the twin-component ultra-reliable low-latency mode of the 5G system. We advocate a further evolutionary step towards multi-component Pareto optimization, which requires the exploration of the entire Pareto front of all optiomal solutions, where none of the components of the objective function may be improved without degrading at least one of the other components.
