Hybrid Satellite Terrestrial Research Articles

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.

Performance of Spectrum Sharing in Hybrid Satellite Terrestrial Network with Opportunistic Relay Selection

In this paper, we consider the uplink of a hybrid satellite-terrestrial spectrum sharing system, in which satellite terminal communicates with satellite through terrestrial relay-assisted transmission. To accommodate expanding networks within limited spectrum, spectrum sharing is considered a promising candidate. For the system in which satellite terminals and terrestrial terminals share spectrum, we propose opportunistic relay selected spectrum sharing method based on decoding and forwarding protocol. Selecting the optimal relay station is aimed at minimizing the outage probability of the satellite terminal and maximizing the throughput of the system. Due to spectrum sharing policy and imperfections in the RF front end, we also consider the effects of cochannel interference (CCI) and hardware impairments (HIs). The satellite link is modeled as Shadowed-Rician fading, and the terrestrial link uses Nakagami-m fading. In addition, we deduce the closed-form analytical expressions of the satellite terminal outage probability, deduce the asymptotic expressions under the condition of high signal-to-noise ratio, and analyze their achievable diversity orders. Numerical and simulation results validate the performance gain of opportunistic relay selection compared to partial relay selection. Monte Carlo simulations confirm the correctness of the theoretical analysis and illustrate the effects of CCI and HIs on the system.

Security Analysis in Multicasting over Shadowed Rician and α−μ Fading Channels: A Dual‐hop Hybrid Satellite Terrestrial Relaying Network

In this era of 5G technology, the ever-increasing demands for high data rates lead researchers to develop hybrid satellite-terrestrial (HST) networks as a substitution to the conventional cellular terrestrial systems. Since an HST network suffers from a masking effect which can be mitigated by adopting the terrestrial relaying strategy, in this work, wireless multicasting is focused on through an HST relaying network (HSTRN) in which a satellite sends messages to multiple terrestrial nodes via multiple relays under the wiretapping efforts of multiple eavesdroppers. The concern is to protect the multicast messages from being eavesdropped taking advantage of the well-known opportunistic relaying technique. It is considered that the satellite links follow Shadowed Rician fading whereas the terrestrial links undergo α − μ fading. The secrecy performance of the proposed HSTRN model is accomplished by deriving expressions for the probability of nonzero secrecy multicast capacity, ergodic secrecy multicast capacity, and secure outage probability for multicasting in closed-form. Capitalizing on the derived expressions, the authors analyze how a perfect secrecy level can be preserved in spite of harsh channel conditions and also present a secrecy trade-off in terms of the number of relays, multicast users, and multiple eavesdroppers. Finally, the numerical analyses are corroborated via Monte-Carlo simulations.

On the Performance of Hybrid Satellite-Terrestrial Content Delivery Networks With Non-Orthogonal Multiple Access

Wireless content delivery (CD) and non-orthogonal multiple access (NOMA) have been confirmed to be promising and effective approaches to gain substantial performance improvement for hybrid satellite-terrestrial (HST) networks. To improve the spectrum efficiency and reduce the delay of retrieving the content for the satellite user, we investigate the performance of the HST-CD network with the NOMA scheme, where the satellite proactively pushes/broadcasts the popular contents to the cache-enabled relay, and then the user is able to directly retrieve the required content from the relay with less transmission delay. Specifically, based on the practical propagation model along with the stochastic geometry, the outage probability for the cache-enabled relays of the considered network is theoretically derived. Besides, the hit probability of the user in the HST-CD network is also provided. Finally, both simulation and analytical results are provided to validate the effect of the HST-CD network with the NOMA scheme and proclaim the influence of key factors on the performance.

Optimal Beamforming for Hybrid Satellite Terrestrial Networks With Nonlinear PA and Imperfect CSIT

In hybrid satellite-terrestrial networks (HSTNs), spectrum sharing is crucial to alleviate the "spectrum scarcity" problem. Therein, the transmit beams should be carefully designed to mitigate the inter-satellite-terrestrial interference. Different from previous studies, this work considers the impact of both nonlinear power amplifier (PA) and large-scale channel state information at the transmitter (CSIT) on beamforming. These phenomena are usually inevitable in a practical HSTN. Based on the Saleh model of PA nonlinearity and the large-scale multi-beam satellite channel parameters, we formulate a beamforming optimization problem to maximize the achievable rate of the satellite system while ensuring that the inter-satellite-terrestrial interference is below a given threshold. The optimal amplitude and phase of desired beams are derived in a decoupled manner. Simulation results demonstrate the superiority of the proposed beamforming scheme.

On Performance Analysis of NOMA-Aided Hybrid Satellite Terrestrial Relay With Application in Small-Cell Network

Satellite communication systems need to be integrated with emerging small-cell network to provide seamless connectivity and high-speed broadband access for mobile users in future wireless networks. In this paper, we study a hybrid satellite-terrestrial relay system (HSTRS) employing small cell transmission under interference constraint with macro-cell users. To characterize such HSTRS-assisted small-cell network, Shadowed-Rician fading for satellite links and Nakagami-$m$ fading for terrestrial links are adopted. We further deploy non-orthogonal multiple access (NOMA) to improve spectrum efficiency. To provide performance analysis, we derive exact formulas for outage probability and throughput of the considered HSTRS, and further examine its achievable diversity order. More importantly, we conduct the performance analysis by indicating performance gaps among two users, and such a gap depends on power allocation factors. We evaluate key performance metrics through the derived analytical expressions to provide useful framework of HSTRN and to characterize the impact of interference in different cells, and integer values of the per-hop fading severity parameters. The useful guidelines are introduced in the design of futuristic HSTRS for small-cell communications.

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.

하이브리드 위성-지상 중계기 네트워크에서 실질적인 비디오 스트리밍 서비스 품질평가

본 논문에서는 MRC 기법을 사용하는 하이브리드 위성-지상 중계기 네트워크에 대해서 고려하고, 하이브리드 위성-지상 중계기 네트워크에서 비디오 스트리밍 서비스의 실질적인 품질을 평가해 본다. 이를 위해 품질 평가에서는 PSNR과 MOS를 성능지표로 활용하였다. 시뮬레이션 결과, 다양한 시뮬레이션 환경에서 지상 중계기의 수가 증가할수록 비디오 스트리밍 서비스의 품질이 향상되는 것을 살펴볼 수 있었다. 또한, MRC 기법을 사용하는 하이브리드 위성-지상 중계기 네트워크 덕분에 스펙트럼 효율 성능도 향상될 수 있는 것을 확인하였다. 성능분석 결과를 바탕으로 결론에서는 비디오 스트리밍 품질을 좀 더 효율적으로 향상하기 위한 추가적인 고려사항과 병행하여 적용될 수 있는 기술에 대하여 토론해 본다.

A Secure Hybrid Satellite-Terrestrial Communication Network With AF/DF and Relay Selection

This paper makes research on a secure hybrid satellite-terrestrial communication network with eavesdroppers at the primary and secondary receivers. To secure the transmitted messages, we adopt the null space beamforming to the amplified-and-forward (AF) relay protocol and weighted fractional data carrying artificial noise (WFDCAN) to the decoded-and-forward (DF) relay protocol at the satellite. Considering the time delay may be brought by the WFDCAN, we introduce a parameter θ to indicate the delay severity. The secrecy capacity is combined with θ to derive the maximum secrecy delay constrain. The secrecy capacity, the ASER of the up-link channel and the delay constrain of the down-link channel are applied as factors for a three level relay protocol selection scheme. To simplify the analyses and expressions, the models of the AF protocol and the DF protocol are integrated to form a new transmission model. Furthermore, the secrecy performance at the destination receiver is considered for terrestrial relay selection to enhance the security performance. We also apply the columns of the frequency hopping based multi-term weighted fractional fourier transform (FH-MWFRFT) matrix as signal processing vector to the base station of the terrestrial network to minimize the interference it brings to the terrestrial relays. The simulation results demonstrate that the proposed system could maintain the security at the relays and the secondary receiver while reducing the delay at the satellite in some conditions.

Hybrid Satellite Terrestrial Relay Networks With Cooperative Non-Orthogonal Multiple Access

In this letter, we investigate the outage probability (OP) and ergodic capacity of the downlink hybrid satellite terrestrial relay networks (HSTRNs) with a cooperative non-orthogonal multiple access (C–NOMA) scheme, in which a user with better channel condition acts as a relay node and forwards information to other users, thus alleviating the masking effect of users with poor channel conditions in heavy shadowing. Specifically, the exact analytical expression for the OP of the considered system is derived. Furthermore, the ergodic capacity expression is also developed to facilitate performance evaluation of the proposed framework. Finally, the simulations are provided to show the impact of key parameters on the considered system and the superiority of introducing the C–NOMA scheme to the HSTRNs.

Physical Layer Security for Hybrid Satellite Terrestrial Relay Networks With Joint Relay Selection and User Scheduling

In this paper, we investigate the impacts of joint relay selection and user scheduling scheme on the physical layer security for hybrid satellite-terrestrial relay systems, where multiple terrestrial relays, multiple terrestrial users, and multiple illegitimate eavesdroppers are considered in the network. To strengthen the system security against wiretapping attack, we present a joint opportunistic relay selection and the threshold based user scheduling scheme to balance the system performance and implementation complexity. Furthermore, two representative eavesdropping cases are considered, i.e., the Case I, colluding case: the eavesdroppers cooperate with each other and wiretap the information together, and the Case II, non-colluding case: the best eavesdropper will be chosen to wiretap the information channel. Besides, we derive the closed-form expressions for the average secrecy capacity based on the proposed relay selection and user scheduling scheme in the presence of two eavesdropping cases. To get more insights at high signal-to-noise ratios, the asymptotic expressions for the average secrecy capacity are also derived under two cases, from which we can get the effect of different parameters on the system performance conveniently. At last, analytical results are validated through comparison with the Monte Carlo simulations.

Broadband Hybrid Satellite-Terrestrial Communication Systems Based on Cognitive Radio toward 5G

The development of 5G terrestrial mobile communications technology has been a driving force for revolutionizing satellite mobile communications. Satellite mobile communications, which carry many unique features, such as large coverage and support for reliable emergency communications, should satisfy the requirements for convergence between terrestrial mobile communications and satellite mobile communications for future broadband hybrid S-T communications. On the other hand, CR is an attractive technique to support dynamic single-user or multi-user access in hybrid S-T communications. This article first discusses several key issues in applying cognitive radio to future broadband satellite communications toward 5G. Then we present an overview of future broadband hybrid S-T communications systems, followed by an introduction to a typical application scenario of futuristic CR-broadband hybrid S-T communication systems toward 5G. Moreover, we propose a space segment design based on a spectrum-sensing-based cooperative framework, in consideration of the presence of MUs. An experiment platform for the proposed CR-based hybrid S-T communications system is also demonstrated.

Outage Performance of Cognitive Hybrid Satellite–Terrestrial Networks With Interference Constraint

This paper investigates the performance of a cognitive hybrid satellite–terrestrial network, where the primary satellite communication network and the secondary terrestrial mobile network coexist, provided that the interference temperature constraint is satisfied. By using the Meijer-G functions, the exact closed-form expression of the outage probability (OP) for the secondary network is first derived. Then, the asymptotic result in a high-signal-to-noise-ratio (SNR) regime is presented to reveal the diversity order and coding gain of the considered system. Finally, computer simulations are carried out to confirm the theoretical results and reveal that a more loose interference constraint or heavier shadowing severity of a satellite interference link leads to a reduced OP, whereas stronger satellite interference power poses a detrimental effect on the outage performance.

Channel Estimation and Detection in Hybrid Satellite–Terrestrial Communication Systems

We address the problem of amplify-and-forward (AF) relaying in a hybrid satellite-terrestrial communication system with unknown channel gains. A masked destination earth station (ES) receives the signal forwarded by a relaying ES, i.e., from a terrestrial link. There is no direct transmission from the satellite to the destination ES. The satellite-relay ES (satellite link) and relay ES-destination ES (terrestrial link) links are assumed to follow shadowed Rician fading and Nakagami-m fading, respectively. A scheme for channel estimation and detection of transmitted signal from the satellite to the destination ES is proposed. The terrestrial link is estimated separately, whereas the cooperative hybrid link (satellite-relay-destination) is estimated jointly with symbol detection. The average symbol error rates of the M-ary phase-shift keying and M-ary quadrature amplitude modulation constellations are derived for the considered hybrid communication system. Moreover, we also derive the analytical diversity order of the considered system with estimated channel gains. It is shown by simulation and analysis that the estimation error does not affect the diversity order of the system. Furthermore, the average and asymptotic capacity of the system is also derived by using the moment-generating function approach.

Performance Analysis of Hybrid Satellite–Terrestrial Cooperative Systems with Fixed Gain Relaying

In this paper, we investigate the performance of a hybrid satellite---terrestrial cooperative relay system, where both of the source-relay and source---destination links experience independent non-identical shadowed-Rician fading while the relay-destination link undergoes uncorrelated Rayleigh fading. By employing maximal-ratio-combining at the destination to combine the signals from the direct link and the fixed-gain relay links, we first obtain the analytical expression for the moment generating function (MGF) of the output signal-to-noise ratio (SNR). Then, with the help of the obtained MGF, we derive the theoretical formulas for the ergodic capacity and average symbol error rate of the considered system. Moreover, the asymptotic analysis at high SNR is also presented to reveal the diversity order and array gain of the system. Finally, the effectiveness of the analytical results is verified through comparison with Monte Carlo simulations.

Symbol Error Analysis of Hybrid Satellite–Terrestrial Cooperative Networks With Cochannel Interference

This letter investigates the effect of cochannel interference (CCI) on a hybrid satellite-terrestrial cooperative relay network (HSTCN), where both the satellite-destination and satellite-relay links undergo the shadowed Rician fading, whereas the relay-destination link follows the Rayleigh fading. By assuming that decode-and-forward (DF) protocol is adopted at the terrestrial relay, and the destination is corrupted by multiple CCI, we first derive the analytical expression for the moment generating function (MGF) of the output signal-to-interference-plus-noise ratio (SINR). Then, based on the Meijer-G functions, we present an approximated yet accurate method to evaluate the average symbol error rate (ASER) of the cooperative network. Moreover, the asymptotic ASER at high signal-to-noise ratio (SNR) with respect to diversity order and array gain are also given to gain further insights. Finally, numerical results are provided to demonstrate the validity of the performance analysis as well as the impact of CCI on the HSTCN.