Hybrid Satellite-terrestrial Relay Network Research Articles

Capacity Analysis of Hybrid Satellite-Terrestrial Systems with Selection Relaying.

A hybrid satellite-terrestrial relay network is a simple and flexible solution that can be used to improve the performance of land mobile satellite systems, where the communication links between satellite and mobile terrestrial users can be unstable due to the multipath effect, obstacles, as well as the additional atmospheric losses. Motivated by these facts, in this paper, we analyze a system where the satellite-terrestrial links undergo shadowed Rice fading, and, following this, terrestrial relay applies the selection relaying protocol and forwards the information to the final destination using the communication link subjected to Nakagami-m fading. For the considered relaying protocol, we derive the exact closed-form expressions for the outage probability, outage capacity, and ergodic capacity, presented in polynomial-exponential form for the integer-valued fading parameters. The presented numerical results illustrate the usefulness of the selection relaying for various propagation scenarios and system geometry parameters. The obtained analytical results are corroborated by an independent simulation method, based on the originally developed fading simulator.

Performance Analysis of NOMA-Based Hybrid Satellite-Terrestrial Relay Networks With CCI

Hybrid satellite-terrestrial relay networks (HSTRNs) which exploit relay cooperative technology in the integrated system of satellites and terrestrial base stations (BSs) are expected to offer enhanced transmission performance benefited from the spatial gain of independent fading paths. To enable multi-user accessing and resource sharing among users, non-orthogonal multiple access (NOMA) technique can be applied in HSTRNs. In this paper, we consider a NOMA-based HSTRN where a satellite transmits signals to a relay base station (RBS) and a destination ground station (DGS), and RBS also serves a cellular user (CU) and DGS simultaneously by leveraging NOMA scheme. We assume that the satellite shares spectrum with a number of cellular small BSs (SBSs), hence SBSs will cause co-channel interference (CCI) to DGS, RBS and CU. We examine the transmission characteristics of the satellite and terrestrial links, and derive the closed-form expressions of the outage probability (OP) and average symbol error rate (ASER) of DGS and CU, respectively. Specially, we consider the effect of perfect and imperfect successive interference cancellation (SIC) on the ASER performance of CU. Then, considering the stochastic characteristics of satellite links and CCI, we analyze the mean energy efficiency (MEE) of the satellite and propose an optimal power allocation scheme which maximizes the MEE of the satellite and achieves system performance optimization. Simulation results demonstrate the effectiveness of the theoretical analysis and the proposed power allocation scheme.

Outage Analysis of Alamouti-NOMA Scheme for Hybrid Satellite–Terrestrial Relay Networks

In this article, we investigate the performance of hybrid satellite–terrestrial relay networks with multiuser downlink nonorthogonal multiple access. The satellite applies Alamouti space–time block coding, and users exploit a receive antenna selection technique. Communication between the satellite and users is assumed to be established with the aid of a half-duplex terrestrial relay equipped with multiple receive antennas and operating in amplify-and-forward mode, because of the heavy masking effects attributed to environmental obstacles. Subsequently, the satellite–relay link is exposed to shadowed-Rician fading, whereas the relay–users links undergo Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> fading, which is a generic statistical channel model for nonterrestrial networks. To be more practical, we consider imperfect successive interference cancellation. The exact outage probability of each user and the corresponding asymptotic expression at the high signal-to-noise ratio are derived to demonstrate the system performance. The analysis indicates that the shadowing conditions do not affect the array gain when the diversity order is dominated by the multiantenna configuration of the second hop. The theoretical derivations are validated by using Monte Carlo simulations. The numerical results indicate that the proposed scheme significantly improves the performance of each user under various shadowing conditions. It also outperforms orthogonal multiple access when proper power levels are allocated to users.

Coverage Probability Analysis of Amplify and Forward Based Multi-user Hybrid Satellite Terrestrial Relay Network

This article examines coverage probability for a multi-user hybrid satellite terrestrial relay network (HSTRN) with opportunistic user scheme. Better quality information are gathered via HSTRN-based networks for users on the ground. Simultaneous satellite signals are amplified by relays and relayed to terrestrial users with the highest instantaneous signal-to-noise ratio (SNR) on an individual channel. Analytically approximate coverage probability is derived for fixed and variable gain relaying. The multi-user relay network is analyzed under Nakagami-m fading, and Rician shadowed fading. We perform simulation and analytical validation to validate our study and compare the performance of fixed and variable gain relaying.

Outage Probability Analysis of Rate Splitting Multiple Access-Based Hybrid Satellite-Terrestrial Relay Network with Relay Selection

Outage Probability Analysis of Rate Splitting Multiple Access-Based Hybrid Satellite-Terrestrial Relay Network with Relay Selection

Performance analysis of multi-satellite hybrid satellite-terrestrial relay networks

Performance analysis of multi-satellite hybrid satellite-terrestrial relay networks

Refracting RIS-Aided Hybrid Satellite-Terrestrial Relay Networks: Joint Beamforming Design and Optimization

Reconfigurable intelligent surface (RIS) has been viewed as a promising solution in constructing reconfigurable radio environment of the propagation channel and boosting the received signal power by smartly coordinating the passive elements’ phase shifts at the RIS. Inspired by this emerging technique, this article focuses on joint beamforming design and optimization for RIS-aided hybrid satellite-terrestrial relay networks, where the links from the satellite and base station (BS) to multiple users are blocked. Specifically, a refracting RIS cooperates with a BS, where the latter operates as a half-duplex decode-and-forward relay, in order to strengthen the desired satellite signals at the blocked users. Considering the limited onboard power resource, the design objective is to minimize the total transmit power of both the satellite and BS while guaranteeing the rate requirements of users. Since the optimized beamforming weight vectors at the satellite and BS, and phase shifters at the RIS are coupled, leading to a mathematically intractable optimization problem, we propose an alternating optimization scheme by utilizing singular value decomposition and uplink–downlink duality to optimize beamforming weight vectors, and using Taylor expansion and penalty function methods to optimize phase shifters iteratively. Finally, simulation results are provided to verify the superiority of the proposed scheme compared to the benchmark schemes.

Outage Analysis of Multi-Relay NOMA-Based Hybrid Satellite-Terrestrial Relay Networks

This article investigates the outage performance of a novel two-user multi-relay non-orthogonal multiple access (NOMA)-based hybrid satellite-terrestrial relay network (HSTRN), in which one user has a direct link to the satellite (termed as the direct-link user), while the other user (termed as the relay-aided user) seeks the help of the direct-link user or the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> dedicated decode-and-forward (DF) relays to acquire its desired signal. A relaying protocol and a three-stage relay selection strategy are proposed for minimizing the whole system outage probability (WSOP) and providing full diversity order (DO) for both users. Exact and asymptotic outage probabilities of the considered network are derived, showing that under the proposed relay selection strategy, the relay-aided user, the direct-link user and the whole system each can achieve a DO of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K + 1$</tex-math></inline-formula> . Finally, numerical results are presented to verify the theoretical analyses, manifest the impacts of key parameters on the system performance, and demonstrate the advantages of our proposed relay selection scheme over other benchmarks.

Uplink Outage Performance of NOMA-Based Hybrid Satellite-Terrestrial Relay Networks Over Generalized Inhomogeneous Fading Channels

In this paper, we investigate the outage performance of an uplink (UL) non-orthogonal multiple access (NOMA)-based hybrid satellite-terrestrial relay network (HSTRN), in which two users communicate with the satellite through a decode-and-forward (DF) relay due to the lack of direct link. To provide a comprehensive yet hitherto unexplored outage analysis framework, we consider a more generalized channel model, i.e., the terrestrial and satellite links, respectively, undergo <inline-formula> <tex-math notation="LaTeX">$\alpha -\mu $ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$\kappa -\mu $ </tex-math></inline-formula> shadowed fadings. Under fixed power allocation (FPA) for both multiple access phase and relaying phase, we firstly study three successive interference cancellation (SIC) decoding schemes, of which the first two are refined from existing schemes, while the third one, named as <i>extended SIC (ESIC)</i>, is proposed in this paper to satisfy the quality of service (QoS) decoding criterion, which is shown to offer better performances for both users as compared to the former two SIC schemes. We also propose a novel dynamic power allocation (DPA) scheme for the multiple access phase, termed as <i>enhanced DPA (EDPA)</i>, to overcome both users&#x2019; error floor (EF) issue yet provide better user fairness than the conventional DPA in the literature. We then analyze the exact and asymptotic outage performance for three SIC and the <i>EDPA</i> schemes under the generalized channel setting. It is shown that both the proposed <i>ESIC</i> and <i>EDPA</i> can circumvent the EF issue and moreover, each has its own advantage in terms of the diversity order (DO). Our results also reveal that there exists a trade-off between <i>ESIC</i> and <i>EDPA</i>, since the former requires a premise on users&#x2019; targets rates to overcome the EF and once this premise is satisfied, no DO degradation will occur, while the latter does not entail such a premise but may face potential DO degradation. Finally, we present numerical results to verify the theoretical analysis, manifest the impacts of key parameters on the system performance, and demonstrate the advantages of our proposed network over other benchmarks.

Performance Analysis of the Hybrid Satellite-Terrestrial Relay Network With Opportunistic Scheduling Over Generalized Fading Channels

A hybrid satellite-terrestrial relay network (HSTRN) has been envisioned as a promising communication architecture for future wireless communications, which can prominently reduce the impact of shadow fading and expand service coverage. In this paper, we conduct theoretical performance analysis for a dual-hop communication system, consisting of multiple relays and multiple users in the HSTRN with the amplify-and-forward protocol. For the shadowing effect and the multipath effect, we introduce the shadowed-Rician distribution and Nakagami-<inline-formula><tex-math notation="LaTeX">$m$</tex-math></inline-formula> fading to characterize the channel models for the satellite-relay and the relay-user links, respectively. Additionally, the opportunistic scheduling scheme is employed, where the optimal relay and the optimal user are selected from the alternative nodes with the maximum instantaneous signal-to-noise ratio. Thereafter, the analytical expressions including ergodic capacity and average symbol error rate (SER) are derived. More specifically, we also present the asymptotic behavior of the average SER at the high signal-to-noise ratio (SRN) regime. The theoretical analysis is validated by the numerical results. Moreover, the results also reveal that the performance of the system can be improved by increasing the number of relays and users under different channel parameters and various modulation schemes.

Performance analysis of PDMA-based hybrid satellite–terrestrial networks with decode-and-forward relaying

As one of the most promising non-orthogonal multiple access (NOMA) technologies in 5G communication, pattern division multiple access (PDMA) has theoretically higher spectrum utilization and a larger communication capacity than conventional orthogonal multiple access (OMA) technologies. In this letter, PDMA is applied to hybrid satellite–terrestrial networks with decode-and-forward (DF) relaying in the downlink, and an in-depth study on the performance of outage probability (OP), ergodic capacity and system throughput is performed. For a more comprehensive analysis, hybrid satellite–terrestrial relay networks (HSTRNs) with conventional OMA technology are used in the comparative analysis. Analysis and simulation results show that PDMA-based hybrid satellite–terrestrial relay networks outperform the other system in terms of OP and ergodic capacity.

Symbol Error Analysis of Amplify-and-Forward Based Multiuser Hybrid Satellite-Terrestrial Relay Network

In this letter, we study the average symbol error rate (ASER) performance in a multiuser hybrid satellite-terrestrial relay network (HSTRN) with opportunistic scheduling. The signal broadcast from the satellite is amplified by relay and forwarded to the terrestrial user that has the maximum instantaneous signal-to-noise ratio (SNR) in its channel. Specifically, both the approximate analytical formula and asymptotic expression at high SNRs of the ASER are derived for the fixed gain relaying as well as the variable gain relaying. Monte Carlo simulation are provided to verify our analysis and indicate the performance disparity between the two kinds of relaying protocols.

Physical Layer Secrecy Analysis of Multihop Hybrid Satellite-Terrestrial Relay Networks with Jamming

This paper explores the secrecy analysis of a multihop hybrid satellite-terrestrial relay network (HSTRN) with jamming, where one satellite source is aimed at communicating with destination users via multihop decode-and-forward (DF) terrestrial relays, in the existence of an eavesdropper. All the destination users are deployed randomly following a homogeneous Poisson point process (PPP) based on stochastic geometry. Each relay operates not only as a conventional DF relay to forward the received signal but also as a jammer to generate intentional interference to degrade the eavesdropper link, considering shadowed-Rician fading for legitimate link and wiretap link while Rayleigh fading for jamming link. To characterize the secrecy performance of the considered network, the accurate analytical expression for the secrecy outage probability (SOP) is derived. In order to reveal further insights on the achievable diversity order of the network, the asymptotic behavior of SOP expression at high signal-to-noise ratio (SNR) region is deduced. Moreover, the throughput of the system is discussed to characterize the secrecy performance. Finally, the theoretical results are validated through comparison with simulation results and show that (1) the secrecy performance of the considered network gets better with the decreasing of the hops and with the decreasing severity of the channel fading scenario, (2) the relay of the network operating as a jammer can provide better secrecy performance without extra network resources, and (3) small hops and high SNR can yield to high throughput of the system.

Outage of NOMA-Based Hybrid Satellite-Terrestrial Multi-antenna DF Relay Networks

This letter analyzes the outage performance of a novel two-user non-orthogonal multiple access (NOMA)-based hybrid satellite-terrestrial relay network (HSTRN), in which one user can directly receive the signals from the satellite while the other user can only acquire its desired signal through a multiple-antenna decode-and-forward (DF) relay. In particular, a novel DF relaying protocol is designed to deal with the unbalanced channel condition and improve the performance for both users. Numerical results are provided to validate our analyses, unveil the impacts of key parameters on the system performance, and demonstrate the advantages of our proposed scheme over other benchmarks.

Outage Analysis of NOMA-Based Multiple-Antenna Hybrid Satellite-Terrestrial Relay Networks

In this letter, the outage performance of a novel non-orthogonal multiple access (NOMA)-based hybrid satellite-terrestrial relay network (HSTRN) is analyzed, where the satellite can directly communicate with one user while communicating with the other user only through an amplify-and-forward (AF) multiple-antenna relay. Exact and asymptotic outage probabilities of both users are derived by considering both fixed gain (FG) and variable gain (VG) AF relaying protocols, along with practical imperfect successive interference cancellation (I-SIC). Numerical results are provided to validate our analysis and unveil some useful engineering insights, such as the impacts of I-SIC, the number of antennas and the choice of relaying protocols on the system performance.

Hybrid Satellite-Terrestrial Relay Network: Proposed Model and Application of Power Splitting Multiple Access.

The development of hybrid satellite-terrestrial relay networks (HSTRNs) is one of the driving forces for revolutionizing satellite communications in the modern era. Although there are many unique features of conventional satellite networks, their evolution pace is much slower than the terrestrial wireless networks. As a result, it is becoming more important to use HSTRNs for the seamless integration of terrestrial cellular and satellite communications. With this intent, this paper provides a comprehensive performance evaluation of HSTRNs employing non-orthogonal multiple access technique. The terrestrial relay is considered to be wireless-powered and harvests energy from the radio signal of the satellite. For the sake of comparison, both amplify-and-forward (AF) and decode-and-forward (DF) relaying protocols are considered. Subsequently, the closed-form expressions of outage probabilities and ergodic capacities are derived for each relaying protocol. Extensive simulations are performed to verify the accuracy of the obtained closed-form expressions. The results provided in this work characterize the outage and capacity performance of such a HSTRN.

Outage analysis of partial relay selection based on shadowing side information in hybrid satellite‐terrestrial relay networks

AbstractEnabling to increase the data rate and reliability of satellite‐terrestrial communication, hybrid satellite‐terrestrial relay network (HSTRN) has attracted wide attention recently. In the HSTRN, traditional partial relay selection (PRS) schemes are mainly based on complete channel state information (CSI) of the satellite‐relay links, which may be outdated and thus deteriorate the system performance. To reduce the feedback overhead of CSI as well as guarantee the communication performance of HSTRN, we firstly propose a PRS scheme only based on shadowing side information of the composite satellite‐relay links. Then, we derive accurate outage probability expressions to theoretically analyze system performance of HSTRN with PRS based on shadowing side information, where the satellite‐relay and relay‐destination links are modeled as composite generalized‐K fading and Nakagami‐m fading, respectively. In addition, in order to understand the diversity gain of the HSTRN more clearly, we analyze the asymptotic results at high signal‐to‐noise ratio region. Simulation results show that our proposed scheme is robust to outdated CSI and can achieve approximate performance as the traditional complete CSI‐based PRS scheme under a better channel environment. Moreover, the accuracy of exact outage probability and asymptotic OP analyses are validated.

Cooperative jamming for physical layer security in hybrid satellite terrestrial relay networks

To integrate the satellite communications with the LTE/5G services, the concept of Hybrid Satellite Terrestrial Relay Networks (HSTRNs) has been proposed. In this paper, we investigate the secure transmission in a HSTRN where the eavesdropper can wiretap the transmitted messages from both the satellite and the intermediate relays. To effectively protect the message from wiretapping in these two phases, we consider cooperative jamming by the relays, where the jamming signals are optimized to maximize the secrecy rate under the total power constraint of relays. In the first phase, the Maximal Ratio Transmission (MRT) scheme is used to maximize the secrecy rate, while in the second phase, by interpolating between the sub-optimal MRT scheme and the null-space projection scheme, the optimal scheme can be obtained via an efficient one-dimensional searching method. Simulation results show that when the number of cooperative relays is small, the performance of the optimal scheme significantly outperforms that of MRT and null-space projection scheme. When the number of relays increases, the performance of the null-space projection approaches that of the optimal one.

Hybrid Satellite-Terrestrial Relay Networks With Adaptive Transmission

Hybrid satellite-terrestrial relay network (HSTRN) has been viewed as a flexible and promising solution to be developed with heterogeneous devices and integrated infrastructures for improved coverage and reduced latency. Taking the requirements of overall spectral and power efficiency into account, we consider different adaptive transmission schemes for the hybrid architecture oriented to potential applications in practical scenarios, and obtain the analytical expressions for the achievable channel capacity with respect to different schemes, i.e., optimal power and rate adaptation, and truncated channel inversion and fixed rate. Numerical simulations confirm the validity of the derived theoretical results, and provide useful guidance for emerging applications in HSTRN that are under various fixed/adaptive transmit power or rate requirements.

Physical-Layer Security in Space Information Networks: A Survey

Research and processing development on satellite communications has strongly re-emerged in recent years. Following the prosperity of various wireless services provided by satellite communications, the security issue has raised growing concerns since the space information network is susceptible to be eavesdropped by illegal adversaries in such a large-scale wireless network. Recently, the physical-layer security (PLS) has emerged as an alternative security paradigm that explores the randomness of the wireless channel to achieve confidentiality and authentication. The success story of the PLS technique now spans a decade and thrives to provide a layer of defense in satellite communications. With this position, a comprehensive survey of satellite communications is conducted in this article with an emphasis on PLS. We first briefly introduce essential background and the view of the satellite Internet of Things (IoT), as well as discuss related research challenges faced by the emerging integrated network architecture. Then, we revisit the most popular satellite channel model influenced by many factors and list the commonly used secrecy performance metrics. Also, we provide an exhaustive review of state-of-the-art research activity on PLS in satellite communications, which we categorize by different architectures including land mobile satellite communication networks, hybrid satellite-terrestrial relay networks, and satellite-terrestrial integrated networks. In addition, a number of open research problems are identified as possible future research directions.