Shadowed Rician Research Articles

Outage Performance of Satellite-Terrestrial Channels With Shadowed Rician Fading via Large Deviations Principle

Outage Performance of Satellite-Terrestrial Channels With Shadowed Rician Fading via Large Deviations Principle

Performance analysis of rate‐splitting multiple access in intelligent reflecting surface‐assisted uplink hybrid satellite‐terrestrial networks

SummaryIn this paper, we investigate the performance of a rate‐splitting multiple access (RSMA)‐based intelligent reflecting surface (IRS)‐assisted uplink hybrid satellite‐terrestrial network. We consider three different scenarios based on the channel phase knowledge at the IRS, namely, the ideal, partial, and blind cases. In the ideal case, the IRS has full knowledge of both the user‐to‐IRS and IRS‐to‐satellite channel phase information. In the partial case, the IRS has only the user‐to‐IRS channel phase information. Last, in the blind case, the IRS has no any knowledge of the phase information. We assume that the user‐to‐IRS channel follows Rician fading, and the IRS‐to‐satellite channel follows the shadowed Rician fading. The closed‐form tight outage probability expressions for all three scenarios are derived. The accuracy of the derivations is confirmed by simulation results. In addition, it is shown that the performance of the RSMA‐based system is superior to those of the conventional non‐orthogonal and orthogonal multiple access‐based systems with a small number of reflecting elements at high target rates.

Downlink Analysis and Evaluation of Multi-Beam LEO Satellite Communication in Shadowed Rician Channels

Downlink Analysis and Evaluation of Multi-Beam LEO Satellite Communication in Shadowed Rician Channels

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.

On Performance Analysis of Wireless Network over Double Shadowed Rician Fading Channel

In the wireless network, many physical conditions may arise where received signal power is shadowed by moving objects along the propagation paths, and further shadowing of the received signal may result from moving objects around the transmitters or receivers. This phenomenon is mathematically modelled in terms of the double (or dual) shadowing process brought about by fading channels where both dominant and scattered wave components fluctuate together. In this present study, the outcome aspects of dual-shadowed wireless fading channels are explored in accordance with outage analysis, channel capacity, and average bit error rate (ABER) for coherent as well as non-coherent modulation schemes. Here, the Rician envelope, which undergoes two shadowing effects, is assumed. The channel format described here is such that both dominant and scattered signals are impacted by the Nakagami m random variable (RV). As a model, the mathematical expressions are derived for channel capacity, outage analysis, and ABER for dual-shadowed Rician fading channels. The effects of different shadowing parameters are explored, and corresponding results are plotted. All the evaluative results are recognised by emulating the simulation results for various values of the fading parameters.

Performance Evaluation of SSK Modulation Over Shadowed-Rician Land Mobile Satellite Links

We investigate the performance of satellite communication systems acquiring the space shift keying (SSK) modulation technique over shadowed-rician (SR) land mobile satellite (LMS) link. Specifically, we discuss the analytical performance of the considered system over independent and identically distributed SR fading channels in terms of symbol error rate (SER), diversity order, and average capacity. The SER of the considered set-up is derived by utilizing moment generating function (MGF) expression over the SR fading LMS communication links. The analytical diversity order of the scheme is derived by using SER expression. We consider the effect of elevation angles on the SER performance, diversity order, and channel capacity of the considered SSK-assisted satellite communication system. As observed from simulation and analytical results, the performance of the considered set-up can be raised by improving elevation angles. Further, a closed-form expression of the average capacity of the SSK assisted satellite communication system is also derived. It is shown through simulation and analysis that the fading conditions and elevation angle does not affect the diversity order of the system, but it adversely acts on the SER performance and average capacity of the system.

Performance analysis of weather‐dependent satellite–terrestrial network with rate adaptation hybrid free‐space optical and radio frequency link

SummaryDue to the rapid development of satellite laser communication technology, free‐space optical (FSO) links present a promising alternative to traditional radio frequency (RF) links. In this paper, taking the influence of weather factors into consideration, we investigate the performance of the hybrid FSO/RF links where the feeder link operates in the FSO band and the user link operates in the hybrid FSO/RF band. Specifically, the FSO feeder link is modeled by the gamma–gamma distribution in the presence of beam wander and pointing error, and the detection method adopts either the intensity modulation with direct intensity (IM/DD) or heterodyne detection. The RF user link is assumed to follow the shadowed Rician model. In addition, in order to improve the transmission rate of the link under the time‐varying satellite–terrestrial channel, a rate adaptation scheme is proposed. The performance of the system under study is evaluated in terms of the outage probability, average bit error rate (BER), and average transmission rate. Our results provide some important insights, for example, (1) due to the constraints of the feeder link and weather factors, there is an upper limit on the outage performance and bit error rate of the hybrid link; (2) the adaptive transmission strategy can significantly improve the transmission rate of the link compared with traditional design.

Age-Optimal Network Coding HARQ Scheme for Satellite-Based Internet of Things

Satellite-based Internet of Things (S-IoT) is viewed as an efficient solution to provide timely status updates to the terrestrial user equipment (UE), due to its ubiquitous coverage and broadband access capability inherited from high throughput satellite (HTS). However, the conventional hybrid automatic repeat request (HARQ) cannot guarantee the freshness of status update transmission, because the reliable transmission needs the retransmission of the lost packets, which deteriorates the freshness due to the nontrivial propagation delay and high bit error rate (BER) of the satellite–territory link (STL). In this article, we propose an age-optimal network coding HARQ (NC HARQ) scheme with the metric of information timeliness, i.e., Age of Information (AoI) to realize timely status updates in S-IoT. First, we model the STL as a shadowed Rician (SR) fading channel and derive the closed-form expressions of BER. Then, we propose a fixed interval NC inserted HARQ (f-NC HARQ) scheme, where the NC packets are inserted in the information packets with fixed interval to accelerate the recovery of lost information packets and derive the expressions of Peak AoI (PAoI) and average end-to-end delay. Furthermore, we propose an adaptive NC inserted HARQ (A-NC HARQ) scheme for the drastic variations in the SR fading channel, where the transmission of the status update is modeled as a partially observable Markov decision process (POMDP) problem and solved by a low complexity improved fast informed bound (iFIB) algorithm. Simulation results validate the accuracy of our theoretical derivations and show that the A-NC HARQ scheme can achieve the lowest PAoI and average end-to-end delay.

On the Error Performance of LoRa-Enabled Aerial Networks Over Shadowed Rician Fading Channels

UAVs can be used as aerial relays to provide communication services in remote uncovered areas or dense environments with occasional high capacity demands. However, due to the low power of Internet-of-Things (IoT) devices, UAV-based IoT applications, such as precision agriculture and environment monitoring, may experience high shadowing or equipment failure, which degrades the communications’ quality between IoT devices and their gateways. To tackle this issue, we consider the long range (LoRa) communication technology. Specifically, we investigate the performance of LoRA-enabled aerial communications, where a LoRa gateway communicates with a distant IoT device through the assistance of an amplify-and-forward (AF) aerial relay. Under the assumption of shadowed Rician fading channels, we characterize at first the end-to-end LoRa communication link. Then, we derive an exact symbol error rate expression for the underlying system model. Finally, numerical results are presented to corroborate the efficacy of our derived expressions and provide valuable insights into the error performance of LoRa-enabled aerial networks.

UAV-Assisted RF/FSO Relay System for Space-Air-Ground Integrated Network: A Performance Analysis

Space-air-ground integrated networks (SAGIN) within UAV-assisted free-space optical (FSO) communication systems can efficiently accommodate massive connections and provide highly reliable and seamless communications. In this work, we investigate the performance of a UAV-assisted, asymmetric, dual-hop radio frequency (RF)/FSO system with the amplified-and-forward relay protocol for the SAGIN. Specifically, the shadowed Rician fading is utilized in this study to characterize the shadowing effect on the RF signal for the satellite-to-UAV link. Meanwhile, the atmospheric turbulence effect on the optical signal for the UAV-to-terrestrial user link is modeled by the Málaga distribution fading, in view of the pointing error impairments. For comparison, the heterodyne detection technique is employed, as well as the intensity modulation with direct detection technique, in improving performance of the relay system. Thus, we derive the closed-form expressions for the cumulative distribution function, probability density function, the moment generating function, and particularly, the moments of the end-to-end RF/FSO system, in terms of Meijer’s G-function. Utilizing these derived formulae, the precise closed-form expressions for the outage probability, the average bit error rate (BER) with various modulation schemes, and the ergodic capacity are given. In specific, the tight asymptotic results for the outage probability and the average BER at the high SNR regions are derived using the asymptotic expansion of Meijer’s G-function. Furthermore, closed-form expressions are presented for the case that the FSO link experiences Gamma-Gamma distribution by changing some specific parameters. Finally, extensive numerical results validate the theoretical results with the Monte-Carlo simulation.

Performance Analysis of HSTC Network with Non-Static Terrestrial Nodes in a Fading Environment

In this paper, Hybrid satellite-terrestrial systems (HSTC) are preferred in dynamic type environments with high mobility of nodes due to the performance enhancement features in multiple relay-based selective decode-and-forward (DF) approach. Because of the satellite link, aerial satellite to destination and satellite to relay links, are not the same due to time-selective shadowed Rician fading. Time-selective Rician fading depends on parameters like the angle of elevation of the satellite, the terrestrial relay node, and the node destination links, considered to be distinctively time-selective Nakagami faded. Here, per-frame average symbol error rate (SER) and outage probability are derived in a closed-form expression with consideration of M-ary PSK modulated symbols transmission. After evaluation, it was detected that the system performance is significantly degraded due to the time-varying nature of the links (dynamic environment). After various simulations and calculations, it was established that the error rate of the HSTC is significantly low by increasing the elevation angle of the satellite on the relay point. The performance enhancement can be observed by enhancing the satellite angle at the destination node of user equipment.

Integrated Satellite-Terrestrial System Capacity Over Mix Shadowed Rician and Nakagami Channels

In this paper, we evaluate the ergodic capacity analysis of a integrated satellite-terrestrial cooperative communication system under independent and non-identical shadowed Rician and Nakagami-m fading channels. Multiple cooperative relay nodes are assumed between satellite and the destination node. Amplify-and-forward (AF) cooperative protocol is used at each fixed relay node for signal amplification. While for signals combining at the destination node, the maximum ratio combining(MRC) technique is exploited. An analytical approach is derived to evaluate the performance of the system in terms of ergodic capacity. We derive the approximate closed-form expression for calculating the ergodic capacity of the proposed system. It is shown that the derived analytical expression is very tight and applicable to the general operating conditions with the help of satellite channel date available from the literature. The analytical results are compared with Monte Carlo simulations, and they seem to agree well.

On the Performance of Mixed FSO/RF SWIPT Systems With Secrecy Analysis

In this article, we consider secure communication over asymmetric dual-hop simultaneous wireless information and power transfer system having one free-space optical (FSO) link followed by one radio frequency (RF) link. We assume that the optical transmitter conveys secure information to the RF receiver through an intermediate relay, which exploits the decode-and-forward relaying technique. The FSO link encounters Málaga (M) distributed turbulence with pointing error, and RF link suffers double shadowed Rician fading. We investigate the consequences of pointing error, atmospheric turbulence, and energy harvesting on the performance of the proposed mixed FSO/RF SWIPT framework. Specifically, we derive the analytical expressions for statistical characteristics such as probability density function, amount of fading, average bit error rate (BER), outage probability (OP), and ergodic capacity. The asymptotic expression for OP is also derived to obtain the diversity order of the system. Based on these results, the physical layer security analysis is carried out, and the analytical expressions for secure OP and strictly positive secrecy capacity are derived. Herein, the two eavesdroppers are considered. In the first scenario, it is assumed that only the FSO link is overheard, while in the second scenario, both FSO and RF links are under simultaneous eavesdropping attack.

On Physical Layer Security of Double Shadowed Rician Fading Channels

On Physical Layer Security of Double Shadowed Rician Fading Channels

Outage Analysis of Coordinated NOMA Transmission for LEO Satellite Constellations

This work investigates the performance of a downlink non-orthogonal multiple access (NOMA) based coordinated low-earth orbit (LEO) satellite system. Two LEO satellites are assumed to coordinate their transmissions to serve three users simultaneously using NOMA protocol, where only one user lies in the intersection of the footprints of the two satellites. We investigate the reliability of the proposed architecture, which is expressed in terms of the outage probability (OP). We derive closed-form expressions of the users’ OPs taking into considerations different realistic losses effects on the link budget including receiver antenna gain, satellite antenna gain, antennas pointing errors, shadowing, small-scale fading, and large-scale free space path loss. The channels between satellites and the three users are assumed to follow shadowed-Rician (SR) fading. The mathematical analysis is verified by the extensive representative Monto-Carlo simulations. Finally, we demonstrate the impact of the system parameters on the considered system as well as the superiority of the NOMA scheme over conventional OMA system.

Reliability of Spectrum-Efficient Mixed Satellite-Underwater Systems

The combination of radio-frequency (RF) communication and underwater optical wireless communication (UOWC) plays a vital role in the underwater Internet of things (UIoT). This correspondence proposes a dual-hop hybrid satellite underwater system that exploits non-orthogonal multiple access (NOMA) as a spectrum-efficient access technique. The RF link from the satellite to the relay on an oil platform is presumptively subject to a Shadowed-Rician (SR) fading, while the UOWC channels from the relay to the underwater destinations are suggested to follow Exponential-Generalized Gamma (EGG) distributions. The reliability of the system is characterized in terms of both underwater destinations and system outage probabilities (OPs). We derive new closed-form expressions for the OPs under imperfect successive interference cancellation (SIC) conditions. Furthermore, the asymptotic OP and the diversity order (DO) are obtained to learn more about the system’s performance. The results are verified through an extensive representative Monte-Carlo simulation. Also, we investigate the performance against the turbulence of the salty water, air bubbles level (BL), temperature gradients (TG), shadowing parameters, and satellite pointing errors due to satellite motion, even if the beam is pointed at the center of the directive antenna relay, the beam will randomly oscillate. Finally, we contrast our approach with the conventional orthogonal multiple access (OMA) scheme to demonstrate its superiority.

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 Physical Layer Security of Mixed FSO-RF SWIPT System With Non-Ideal Power Amplifier

Free-space optical (FSO) links are contemplated as a potential paradigm to yield efficient point-to-point communication in wireless systems. Notably, these links are used to provide the proficient wireless connectivity between the radio frequency (RF) wireless network and the fiber optic-based network. To this end, more attention has been paid to mixed FSO-RF systems where single-hop FSO transmission and single-hop RF transmission configuration is used. In this paper, we propose a mixed FSO-RF dual-hop simultaneous wireless information and power transfer (SWIPT) relaying system in the presence of power amplifier (PA). It is assumed that FSO links suffer from Málaga (M)-turbulence with pointing errors and RF links experience the double shadowed Rician fading. Particularly, the physical layer security is analyzed by deriving the closed-form expressions for secrecy metrics such as secure outage probability, strictly positive secrecy capacity, and secrecy throughput. We consider the three scenarios: 1) FSO-side eavesdropping attack 2) RF-side eavesdropping attack 3) Simultaneous FSO- and RF-side eavesdropping attacks. The asymptotic approximations for the final results are also derived to obtain secrecy diversity order. The effect of SWIPT parameters and PA efficiency on the secrecy performance are then further investigated in detail. In summary, the results show that the reliability and security of the proposed system can be enhanced by utilizing efficient PAs at the RF front end depending on the eavesdropper's location and can also be controlled by the SWIPT parameters.

Secrecy Analysis for Orthogonal Time Frequency Space Scheme Based Uplink LEO Satellite Communication

Recently, satellite communication (Sat-Com) has developed rapidly, and its security is critical. In this letter, we investigate the security performance for an uplink low earth orbit (LEO) Sat-Com system, where the cooperative UAV is employed to send jamming signals against the reconnaissance satellite. In particular, the uplink transmission is based on the orthogonal time frequency space (OTFS) technique, in order to combat the severe Doppler effect caused by the high mobility of the LEO satellite. As a pioneer work, we derive the closed-form expression for the security outage probability (SOP) at the legitimate receiver, where a novel moment matching approach is used for finding a summed probability distribution function (PDF) of the shadowed-Rician (SR) distributed terms. Furthermore, we analyze the SOP advantage achieved by the OTFS scheme over the traditional orthogonal frequency division multiplexing (OFDM) scheme. Simulation results validate the theoretical results for SOP performance of the uplink LEO Sat-Com, and show the effectiveness of employing UAV jammer in terms of enhancing secrecy transmission.

Outage Analysis for Terrestrial-Satellite Spectrum Sharing

This letter investigates the effect of the interference due to spectrum sharing between terrestrial and satellite systems. Based on a realistic coexistence model, we provide an exact closed-form outage probability expression of the satellite link in the presence of the terrestrial interference. We assume Nakagami fading both for terrestrial and satellite links, with an additional consideration for the shadowed Rician fading satellite link. Numerical results show that uncontrolled terrestrial interference can significantly degrade the outage performance of the satellite link. The obtained formulas are useful in predicting and preventing harmful interference when designing coexistence mechanisms for terrestrial and satellite systems.