Terrestrial Satellite Communication Research Articles

Application of 6G Technology in Satellite-Terrestrial Communications

In the contemporary digital era, the accelerated dissemination of data and pervasive interconnectivity have emerged as pivotal drivers of social advancement. The increasing demand for high-performance satellite-terrestrial communications systems, which are vital for achieving seamless global coverage, presents a significant challenge. The advent of 6G technology offers a promising avenue for addressing the current limitations of satellite-terrestrial communications. This paper presents a comprehensive review of the potential applications of 6G technology in satellite-terrestrial communication systems, with a particular focus on its capacity to transform these systems. By achieving seamless global connectivity, 6G technology is positioned to address the limitations of current communication technologies and enhance communication speeds, reliability, and efficiency. This research indicates that the integration of satellite and terrestrial communication networks through 6G not only improves the overall efficiency and coverage of the communication network, but also addresses existing challenges such as limited coverage, high latency and scarce spectrum resources. As research and development progresses, it will be essential to facilitate the widespread adoption and evolution of 6G technology in satellite-terrestrial communications through strengthened global cooperation and standardisation.

Hybrid satellite terrestrial communication systems with buffer-aided relaying

Hybrid satellite terrestrial communication systems with buffer-aided relaying

Beacon-Based Uplink Transmission for LoRaWAN Direct to LEO Satellite Internet of Things

Direct-to-satellite IoT (DtS-IoT) communication structure is a promising solution to provide connectivity and extend the coverage of traditional low-power and long-range technologies, especially for isolated and remote areas where deploying traditional infrastructure is impracticable. Despite their bounded visibility, the Low Earth Orbit (LEO) satellites complement the terrestrial networks, offering broader gateway coverage and terrestrial network traffic offloading. However, the dynamics of LEO and the nature of such integration come with several challenges affecting the efficacy of the network. Therefore, this paper proposes Beacon-based Uplink LoRaWAN (BU-LoRaWAN) to enhance satellite-terrestrial communication efficiency. The proposed scheme exploits the LoRaWAN class B synchronization mechanism to provide efficient uplink transmission from LoRaWAN devices placed on the ground to satellite gateways. BULoRaWAN proposes an uplink transmission slot approach to synchronize ground devices’ uplink traffic with LEO-based orbiting gateways. It also uses a queue data structure to buffer end devices’ ready-to-send packets until the appropriate moment. BU-LoRaWAN avoids possible transmission collision by optimizing a random transmission slot for an end device within the beacon window. The proposed system is implemented and evaluated using OMNeT++ network simulator and FLoRaSat framework. The result demonstrates the feasibility of the proposed system. BU-LoRaWAN achieves better performance compared to the standard LoRaWAN, which manages to deliver almost double the traffic delivered by the standard one.

A Smart Secure model for Detection of DDoS Malicious Traces in Integrated LEO Satellite-Terrestrial Communications

For many researchers, defense against DDoS attacks has always been a major subject of attention. Within the LEO Satellite-Terrestrial (LSTN) network field, distributed denial of service (DDoS) attacks is considered to be one of the most potentially harmful attack techniques. For the facilitation of network protection by the detection of DDoS malicious traces inside a network of satellite devices, machine learning algorithms plays a significant role. This paper uses modern machine learning approaches on a novel benchmark Satellite dataset. The STIN and NSL-KDD datasets has been used to detect network anomalies. The pre-processing of data has been performed effectively and a host of ML methods have been applied to classify the outputs into normal, regular node or untrustable /malicious node. We have evaluated the analysis results in presence of attacks as well as without presence of attacks, supervised machine learning techniques basic measurements like accuracy, True positive, False positive etc. Our proposed trust model shows better accuracy, nearby 98% and we have shown that our proposed machine learning based security model performs better to get rid of DDoS attacks on integrated LEO satellite-terrestrial networks without compromising on the packet routing efficiency. We are able to improve routing speed and improve network security against distributed denial of service (DDoS) attacks by integrating an ensemble-based trust model trained on NSL-KDD+STIN+Exata Simulated resultant dataset with ACO for routing decisions. In dynamic network scenarios, as trustworthiness is an essential criterion in route decision-making, this proposed approach signifies resilient and adaptable routing.

ISAC towards 6G Satellite–Terrestrial Communications: Principles, Status, and Prospects

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.

Enabling Data Sharing Through Data Trusts in LEO Satellite Internet

Due to the advantages of low latency, small propagation loss, and global coverage, LEO satellite network becomes a cost-effective long-distance communication solution for IoT devices in remote areas. Nevertheless, the LEO satellite IoT devices deployed for specific tasks are idle most of the time, raising the obvious question for future research: how to effectively share these idle sensing resources. Fortunately, data trusts emerge as a promising strategy to leverage the idle sensing resources. However, the data trust model faces privacy and security challenges in LEO satellite IoT scenarios to achieve trusted data trading. Therefore, this paper proposes a blockchainenabled data trust model and a trusted data trading scheme for device providers, data trustees, and general users. Furthermore, exploiting the homomorphic encryption technology, we realize the fine-grained data query and device match in the premise of privacy protection for device providers and general users. Lastly, considering the openness of satellite-terrestrial communication links and the limited computing power of LEO satellite IoT devices, we design a non-interactive lightweight authentication protocol based on zero-knowledge proof. The simulation results verify the feasibility, effectiveness, and security performance of the proposed data sharing for LEO satellite IoT.

Resource Allocation and Load Balancing for Beam Hopping Scheduling in Satellite-Terrestrial Communications: A Cooperative Satellite Approach

Resource Allocation and Load Balancing for Beam Hopping Scheduling in Satellite-Terrestrial Communications: A Cooperative Satellite Approach

Широкополосный элемент антенной решетки СВЧ диапазона с управляемой поляризацией

There is an increasing interest with domestic satellite communication and broadband access services [1]. An integral part of such systems are ground terminals, the operating frequencies of which includes centimeter and millimeter bands. These circumstances require timely development of client terminal antennas. The article is devoted to the study of a compact Orthomode transducer combined with radiating element of relatively small electrical size (up to ≈ 1 λ), which can be used as part of an antenna array of a terrestrial satellite communication terminal. The proposed solution will make it possible to create arrays with controlled polarization in a wide frequency range. According to the modeling results, the frequency overlap coefficient of 1.4 is achievable, which corresponds to 93% of the standard waveguide frequency range.

RIS-Assisted Covert Transmission in Satellite–Terrestrial Communication Systems

With the development of the sixth-generation wireless communication technology, the difficulty of covert communication in the satellite communications system (SCS) is further increased. In this paper, a satellite covert communication system based on reconfigurable intelligent surface (RIS) is studied, which consists of a satellite, a terrestrial receiver, RIS, and a warden. Specifically, the ground terminal simultaneously receives the signal transmitted by the satellite and the signal reflected by RIS, while the warden wants to overhear the transmitted signal from the satellite and that reflected by the RIS. The main target of this wort is to maximize the minimum covert rate to improve signal quality while considering the limited onboard resources, the hardware constraints of RIS, and the requirement to implement covert communication. To address the non-convex problem, we propose an effective alternating optimization scheme by jointly optimizing transmitter precoding and RIS to improve the covert communication performance of the considered system. In addition to ideal RIS, we also consider the non-ideal RIS, the angle of which is discrete in the actual case. In addition, several simplified methods are proposed to decrease the computational complexity of the covert communication optimal problem under multiple terminals. Finally, simulation results are provided to verify the superiority of the proposed scheme compared with the benchmark scheme, which suggests that the considered RIS-based satellite-terrestrial covert communication system can significantly improve the achievable masking.

Deep Learning Based Hybrid Intrusion Detection Systems to Protect Satellite Networks

Despite the fact that satellite-terrestrial systems have advantages such as high throughput, low latency, and low energy consumption, as well as low exposure to physical threats and natural disasters and cost-effective global coverage, their integration exposes both of them to particular security challenges that can arise due to the migration of security challenges from one to another. Intrusion Detection Systems (IDS) can also be used to provide a high level of protection for modern network environments such as satellite-terrestrial integrated networks (STINs). To optimize the detection performance of malicious activities in network traffic, four hybrid intrusion detection systems for satellite-terrestrial communication systems (SAT-IDSs) are proposed in this paper. All the proposed systems exploit the sequential forward feature selection (SFS) method based on random forest (RF) to select important features from the dataset that increase relevance and reduce complexity and then combine them with a machine learning (ML) or deep learning (DL) model; Random Forest (RF), Long Short-Term memory (LSTM), Artificial Neural Networks (ANN), and Gated Recurrent Unit (GRU). Two datasets—STIN, which simulates satellite networks, and UNSW-NB15, which simulates terrestrial networks—were used to evaluate the performance of the proposed SAT-IDSs. The experimental results indicate that selecting significant and crucial features produced by RF-SFS vastly improves detection accuracy and computational efficiency. In the first dataset (STIN), the proposed hybrid ML system SFS-RF achieved an accuracy of 90.5% after using 10 selected features, compared to 85.41% when using the whole dataset. Furthermore, the RF-SFS-GRU model achieved the highest performance of the three proposed hybrid DL-based SAT-IDS with an accuracy of 87% after using 10 selected features, compared to 79% when using the entire dataset. In the second dataset (UNSW-NB15), the proposed hybrid ML system SFS-RF achieved an accuracy of 78.52% after using 10 selected features, compared to 75.4% when using the whole dataset. The model with the highest accuracy of the three proposed hybrid DL-based SAT-IDS was the RF-SFS-GRU model. It achieved an accuracy of 79% after using 10 selected features, compared to 74% when using the whole dataset.

UAV-Assisted Secure Communication for Coordinated Satellite-Terrestrial Networks

This letter investigates an unmanned aerial vehicle (UAV)-assisted satellite-terrestrial communication network. Specifically, a three-dimensional mobile UAV helps to enhance coverage and simultaneously enable secure communication between the satellite and ground users with the internal eavesdropper. Moreover, non-orthogonal multiple access protocol is adopted, such that the spectral efficiency can be further improved. Aiming to maximize the secrecy rate, a joint cooperative jamming, transmit power, and UAV trajectory optimization problem is proposed. To deal with its non-convexity, we propose an iterative optimization algorithm that first optimally addresses the jamming and transmit power optimization in close forms and then uses an iterative relaxation technique to design the UAV trajectory for the given power. Simulation results highlight the critical role of the mobile UAV and significantly confirm the effectiveness of the proposed algorithm over the benchmark schemes.

On the performance of hybrid beamforming for massive-MIMO low earth orbit satellite systems

Integrated satellite-terrestrial communications using low earth orbit (LEO) satellites for high data rate transmissions are expected to be incorporated in future wireless networks (e.g., in 6G and beyond). To this end, equipping LEO satellites with a large-scale antenna array in the context of massive multiple-input multiple-output (MIMO) has gained significant research interest both in academia and in industry. However, a fully digital implementation of MIMO signal processing for massive MIMO LEO satellites is not viable due to the high power and complexity requirements. To address this, hybrid antenna array architectures are proposed. This work considers fully-connected hybrid antenna array architecture and analyses the performance of hybrid beamforming (HBF) for massive MIMO LEO satellites. We consider two scenarios relating to the angular spread of user terminals (UTs) on the ground, i.e., small angular spread where UTs are uniformly distributed in a small coverage area, and large angular spread where UTs are uniformly distributed in a large coverage area. The sum rate performance of HBF in different scenarios of user angular spread, and channel state information is analysed and important insights are provided. The performance of HBF is also compared with the fully digital beamforming and analogonly beamforming.

NOMA-based spectrum sensing for satellite-terrestrial communication

With the continuous development of wireless communication technology, the number of access devices continues to soar, which poses a grate challenge to the already scarce spectrum resources. Meanwhile, 6G will be an era of air-space-terrestrial-sea integration, and satellite spectrum resources are also very tight in the context of giant constellations. In this paper, we propose a Non-Orthogonal Multiple Access (NOMA) based spectrum sensing scheme for the future satellite-terrestrial communication scenarios, and design the transceiver from uplink and downlink scenarios, respectively. In order to better identify the user's transmission status, we obtain the feature values of each user through feature detection to make decision. We combine these two technologies to design the transceiver architecture and deduce the threshold value of feature detection in the satellite-terrestrial communication scenario. Simulations are performed in each scenario, and the results illustrate that the proposed scheme combining NOMA and spectrum sensing can greatly improve the throughput with a similar detection probability as Orthogonal Multiple Access (OMA).

Efficient User Scheduling for Uplink Hybrid Satellite-Terrestrial Communication

Due to increasing demands of seamless connection and massive information exchange across the world, the integrated satellite-terrestrial communication systems develop rapidly. To shed lights on the design of this system, we consider an uplink communication model consisting of a single satellite, a single terrestrial station and multiple ground users. The terrestrial station uses decode-and-forward (DF) to facilitate the communication between ground users and the satellite. The channel between the satellite and the terrestrial station is assumed to be a quasi-static shadowed Rician fading channel, while the channels between the terrestrial station and ground users are assumed to experience independent quasi-static Rayleigh fading. We consider two cases of channel state information (CSI) availability. When perfect CSI is available, we derive the instantaneous achievable sum rate of all ground users and formulate an optimization problem to maximize the sum rate. When only channel distribution information (CDI) is available, we derive a closed-form expression for the outage probability and formulate another optimization problem to minimize the outage probability. Both optimization problems correspond to scheduling algorithms for ground users. For both cases, we propose low-complexity user scheduling algorithms and demonstrate the efficiency of our scheduling algorithms via numerical simulations.

UAV-Assisted Satellite-Terrestrial Secure Communication Using Large-Scale Antenna Array With One-Bit ADCs/DACs

Unmanned aerial vehicle (UAV) equipped with large-scale antenna array constitutes a promising relaying candidate for reliable and secure satellite-terrestrial communication. Due to the limitation of energy consumption, a novel UAV architecture with one-bit analog-to-digital converters (ADCs) and one-bit digital-to-analog converters (DACs) is proposed firstly. Leveraging the additive quantization noise model, the exact closed-form expressions of both ergodic capacity and ergodic achievable secrecy rate are derived for UAV-assisted satellite-terrestrial communication systems using large-scale antenna array with one-bit ADCs/DACs. To enhance the transmission capacity and combat the eavesdropper simultaneously, maximum-ratio combining (MRC) is used by UAV to receive signals from satellite and location-based beamforming (LBB) is adopted by UAV to forward signals to destination, where the beamformer is optimized based on the derived expression of the ergodic achievable secrecy rate. Simulation results validate the accuracy of our analytical ergodic achievable secrecy rate, and demonstrate that our proposed MRC/LBB scheme has better secrecy rate than its conventional location-based counterpart.

Green Interference Based Symbiotic Security in Integrated Satellite-Terrestrial Communications

In this paper, we investigate secure transmissions in integrated satellite-terrestrial communications and the green interference based symbiotic security scheme is proposed. Particularly, the co-channel interference induced by the spectrum sharing between satellite and terrestrial networks and the inter-beam interference due to frequency reuse among satellite multi-beam serve as the green interference to assist the symbiotic secure transmission, where the secure transmissions of both satellite and terrestrial links are guaranteed simultaneously. Specifically, to realize the symbiotic security, we formulate a problem to maximize the sum secrecy rate of satellite users by cooperatively beamforming optimizing and a constraint of secrecy rate of each terrestrial user is guaranteed. Since the formulated problem is non-convex and intractable, the Taylor expansion and semi-definite relaxation (SDR) are adopted to further reformulate this problem, and the successive convex approximation (SCA) algorithm is designed to solve it. Finally, the tightness of the relaxation is proved. In addition, numerical results verify the efficiency of our proposed approach.

V/Ka-band LEO high-throughput satellite and integrated satellite–terrestrial network experiment system: First two years flight results

Satellite Internet technology has evolved significantly over the past few years. Low Earth orbit (LEO) satellite communication technology and its applications have received growing interest in the field of global communication, due to their advantages of faster speed, lower latency, higher throughput, etc. GalaxySpace’s first satellite (YINHE-1) has been the world’s first V/Ka-band LEO broadband satellite with a communication capacity of 24 Gbps. The satellite was launched on the 16th of January 2020, and a series of in-orbit tests and satellite–terrestrial communication experiments were carried out within the two years of orbital flight. YINHE-1 is still operating and will participate in subsequent missions developed by GalaxySpace. This paper describes the overall scheme of satellite design and presents an integrated satellite–terrestrial network experiment system. Based on the two-year in-orbit test results, the Q/V band feed beam tracking, throughput and latency, communication under low elevation angles, and user beam switching are evaluated. In addition, the experiment results of integrated satellite–terrestrial communication are analyzed in detail. It is shown that the LEO broadband satellite possesses satisfactory capability in LTE/5G backhaul and Internet applications.

Collaborative Long-Short Term Bandwidth Allocation for Satellite-Terrestrial Networks

To improve users’ communication experience when they access satellite-terrestrial networks, we propose a long-short term bandwidth allocation strategy for beam-hopping low-earth-orbit satellites. Our strategy consists of two collaboratively functioned parts, the prediction-based long-term (PLT) bandwidth allocation and the trend-based short-term (TST) bandwidth allocation. At the beginning of each long term, the PLT method allocates bandwidth resources according to the maximum traffic volume predicted by Hull moving average (HMA), and the Q-learning assisted TST method adjusts the bandwidth allocation of the last short term with consideration of the traffic trend when necessary. Simulation results demonstrate that the proposed strategy is lightweight and can effectively reduce the blocking ratio and improve the supply-demand ratio of satellite-terrestrial communications.

Security of Satellite-Terrestrial Communications: Challenges and Potential Solutions

The integration of satellite and terrestrial networks has become inevitable in the next generations of communications networks due to emerging needs of ubiquitous connectivity of remote locations. New and existing services and critical infrastructures in remote locations in sea, on land and in space will be seamlessly connected through a diverse set of terrestrial and non-terrestrial communication technologies. However, the integration of terrestrial and non-terrestrial systems will open up both systems to unique security challenges that can arise due to the migration of security challenges from one to another. Similarly, security challenges can also arise due to the incompatibility of distinct systems or incoherence of security policies. The resulting security implications, thus, can be highly consequential due to the criticality of the infrastructures such as space stations, autonomous ships, and airplanes, for instance. Therefore, in this article we study existing security challenges in satellite-terrestrial communication systems and discuss potential solutions for those challenges. Furthermore, we provide important research directions to encourage future research on existing security gaps.

Latency versus Reliability in LEO Mega-Constellations: Terrestrial, Aerial, or Space Relay

Large low earth orbit (LEO) mega-constellation systems have been designed and deployed as a global backbone to provide ubiquitous connectivity across the world. However, due to the high traffic load/congestion arisen from the required numerous information relay and forwarding, it is a challenge for LEO mega-constellation systems to set up long-distance connections between two remote terrestrial users for real-time communications, which requires strict low latency. Other than inter-LEO satellite links (ILSL), introducing third-party relays, such as terrestrial, aerial, and satellite relays, is an alternative way to improve the latency performance for wide-area deliveries of real-time traffic. However, the reliability of the transmitted signal will unavoidably degrade, because of the increased path-loss attributed to long-distance relaying transmissions. Then, to reveal the principle that the third-party relays affect the latency and reliability, in this work, an LEO satellite-terrestrial communication scenario is considered, in which two remote terrestrial users communicate with each other via an LEO mega-constellation system. Analysis models are built up to investigate the end-to-end time delay and outage performance while considering different ILSL, terrestrial, aerial, and satellite relay assisted transmission scenarios. More specifically, by applying geometrical probability theory, exact/approximated closed-form analytical expressions have been derived for average time delay