Dynamic Beam-Layout Design for MEO High Throughput Satellite Systems

Scientific Conference (2022, December 04)

We propose a traffic-oriented beam-layout optimization framework for a medium Earth orbit (MEO) high throughput satellite (HTS) system. The designed beam-layout plans have the objective of dynamic traffic ... [more ▼]

We propose a traffic-oriented beam-layout optimization framework for a medium Earth orbit (MEO) high throughput satellite (HTS) system. The designed beam-layout plans have the objective of dynamic traffic load balancing with minimal radio resource management. We model and evaluate the high directivity and the high reconfigurability capabilities of next-generation HTS systems that are equipped with a processing power on board. The resulting payload flexibility is compared numerically against the on-ground counterpart. Adequate key performance indicators, such as the Jain’s fairness index, the load distribution gap and optimization convergence time, are used to benchmark the system against state-of-the-art solutions. Results show that a dynamic HTS in MEO is capable of efficiently attaining high quality load balancing performance under realistic spatiotemporally varying traffic demands. [less ▲]

Physical Layer Security in AF-Based Cooperative SWIPT Sensor Networks

in IEEE Sensors Journal (2022)

Physical layer security (PLS) with radio-frequency (RF) energy harvesting (EH) in wireless sensor networks has received significant interest as a technology for secure information transmission and ... [more ▼]

Physical layer security (PLS) with radio-frequency (RF) energy harvesting (EH) in wireless sensor networks has received significant interest as a technology for secure information transmission and prolonging the network lifetime as well as improving energy efficiency. This paper investigates PLS for a simultaneous wireless information and power transfer (SWIPT) cooperative network, which consists of multiple sensor sources, one EH relay (R), and one destination (D) in the presence of one eavesdropper (E). Further, a low-complexity, suboptimal, yet efficient sensor source selection scheme is proposed. Specifically, one sensor source is chosen to transmit information to the relay and destination such that it obtains the best channel from sensor sources to the relay. Then, by considering two relaying strategies, termed the direct link plus static power splitting-based relaying (SPSR) and direct link plus optimal dynamic power splitting-based relaying (ODPSR), the performance analysis in terms of intercept probability (IP) and outage probability (OP) are carried out for each one. Notably, the eavesdropper and destination utilize maximal ratio combining (MRC) to incorporate the received signals from the selected sensor source and the relay, which poses new challenges in obtaining the analytical expressions. In this context, we derive analytical expressions for the OP (for SPSR and ODPSR) at the destination and the IP (for SPSR) at the eavesdropper by adopting the series representation of the modified Bessel function. Finally, Monte Carlo simulations are conducted to validate the theoretical analysis and the proposed schemes’ effectiveness. Simulation results show the superiority of our scheme compared to the benchmarks. [less ▲]

Coexistence of eMBB and URLLC in Open Radio Access Networks: A Distributed Learning Framework

in IEEE Global Communications Conference (IEEE Globecom), Rio de Janeiro, Brazil, Dec. 2022 (2022, December)

Optimizing Computational and Communication Resources for MEC Network Empowered UAV-RIS Communication

Scientific Conference (2022, December)

With the technological evolution and new applications, user equipment (UEs) has become a vital part of our lives. However, limited computational capabilities and finite battery life bottleneck the ... [more ▼]

With the technological evolution and new applications, user equipment (UEs) has become a vital part of our lives. However, limited computational capabilities and finite battery life bottleneck the performance of computationally demanding applications. A practical solution to enhance the quality of experience (QoE) is to offload the extensive computation to the mobile edge cloud (MEC). Moreover, the network’s performance can be further improved by deploying an unmanned aerial vehicle (UAV) integrated with intelligent reflective surfaces (IRS): an effective alternative to massive antenna systems to enhance the signal quality and suppress interference. In this work, the MEC network architecture is assisted by UAV-IRS to provide computational services to the UEs. To do so, a cost minimization problem in terms of computing time and hovering energy consumption is formulated. Furthermore, to achieve an efficient solution to a formulated challenging problem, the original optimization problem is decoupled into sub-problems using the block-coordinate decent method. Moreover, numerical results are compared to baseline schemes to determine the effectiveness of the proposed scheme. Simulation results demonstrate that the optimal allocation of local computational resources results in minimizing tasks’ computational time and hovering energy consumption. [less ▲]

Hybrid Active-Passive Reconfigurable IntelligentSurface-Assisted UAV Communications

Poster (2022, December)

We consider a novel hybrid active-passive reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicle (UAV) air-ground communications system. Unlike the conventional passive RIS, the hybrid ... [more ▼]

We consider a novel hybrid active-passive reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicle (UAV) air-ground communications system. Unlike the conventional passive RIS, the hybrid RIS is equipped with a few active elements to not only reflect but also amplify the incident signals for significant performance improvement. Towards a fairness design, our goal is to maximize the minimum rate among users through jointly optimizing the location and power allocation of the UAV and the RIS reflecting/amplifying coefficients. The formulated optimization problem is nonconvex and challenging, which is efficiently solved via block coordinate descend and successive convex approximation. Our numerical results show that a hybrid RIS requires only 4 active elements and a power budget of 0 dBm to achieve an improvement of 52.08% in the minimum rate, while that achieved by a conventional passive RIS with the same total number of elements is only 18.06%. [less ▲]

Intelligent and Secure Radio Environments for 6G Vehicular Aided HetNets: Key Opportunities and Challenges

in IEEE Communications standards Magazine (2022)

Reconfigurable meta-surfaces are emerging as a novel and revolutionizing technology to enable intelligent wireless environments. Due to the low cost, improved efficiency, and passive nature of reflecting ... [more ▼]

Reconfigurable meta-surfaces are emerging as a novel and revolutionizing technology to enable intelligent wireless environments. Due to the low cost, improved efficiency, and passive nature of reflecting elements, it is becoming possible to program and control the wireless environment. Since wireless physical layer technologies can generally adapt to the wireless environment, their combination with reconfigurable surfaces and deep learning approaches can open new avenues for achieving secure 6G vehicular aided heterogeneous networks (HetNets). Motivated by these appealing advantages, this work provides an intelligent and secure radio environment (ISRE) paradigm for 6G vehicular aided HetNets. We present an overview of enabling technologies for ISRE-based 6G vehicular aided HetNets. We discuss features, design goals, and applications of such networks. Next, we outline new opportunities provided by ISRE-based 6G vehicular HetNets and we present a case study using the contextual bandit approach in terms of best IRS for secure communications. Finally, we discuss some future research opportunities. [less ▲]

Non-Geostationary Satellite Communications Systems

Book published by The Institution of Engineering and Technology (IET) (2022)

Reliability of Spectrum-Efficient Mixed Satellite-Underwater Systems

in IEEE Open Journal of the Communications Society (2022), 3

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 ... [more ▼]

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. [less ▲]

Integration of backscatter communication with multi-cell NOMA: a spectral efficiency optimization under imperfect SIC

Poster (2022, November 03)

Future wireless networks are expected to connect large-scale low-powered communication devices using the available spectrum resources. Backscatter communications (BC) is an emerging technology towards ... [more ▼]

Future wireless networks are expected to connect large-scale low-powered communication devices using the available spectrum resources. Backscatter communications (BC) is an emerging technology towards battery-free transmission in future wireless networks by leveraging ambient radio frequency (RF) waves that enable communications among wireless devices. Non-orthogonal multiple access (NOMA) has recently drawn significant attention due to its high spectral efficiency. The combination of these two technologies can play an important role in the development of future networks. This paper proposes a new optimization approach to enhance the spectral efficiency of nonorthogonal multiple access (NOMA)-BC network. Our framework simultaneously optimizes the power allocation of base station and reflection coefficient (RC) of the backscatter device in each cell under the assumption of imperfect signal decoding. The problem of spectral efficiency maximization is coupled on power and RC which is challenging to solve. To make this problem tractable, we first decouple it into two subproblems and then apply the decomposition method and Karush-Kuhn-Tucker conditions to obtain the efficient solution. Numerical results show the performance of the proposed NOMA-BC network over the pure NOMA network without BC. [less ▲]

Spectral Efficiency Analysis of Hybrid Relay-Reflecting Intelligent Surface-Assisted Cell-Free Massive MIMO Systems

in IEEE Transactions on Wireless Communications (2022)

A cell-free (CF) massive multiple-input-multiple-output (mMIMO) system can provide uniform spectral efficiency (SE) with simple signal processing. On the other hand, a recently introduced technology ... [more ▼]

A cell-free (CF) massive multiple-input-multiple-output (mMIMO) system can provide uniform spectral efficiency (SE) with simple signal processing. On the other hand, a recently introduced technology called hybrid relay-reflecting intelligent surface (HR-RIS) can customize the physical propagation environment by simultaneously reflecting and amplifying radio waves in preferred directions. Thus, it is natural that incorporating HR-RIS into CF mMIMO can be a symbiotic convergence of these two technologies for future wireless communications. This motivates us to consider an HR-RIS-aided CF mMIMO system to utilize their combined benefits. We first model the uplink/downlink channels and derive the minimum-mean-square-error estimate of the effective channels. We then present a comprehensive analysis of SE performance of the considered system. Specifically, we derive closed-form expressions for the uplink and downlink SE. The results reveal important observations on the performance gains achieved by HR-RISs compared to conventional systems. The presented analytical results are also valid for conventional CF mMIMO systems and those aided by passive reconfigurable intelligent surfaces. Such results play an important role in designing new transmission strategies and optimizing HR-RIS-aided CF mMIMO systems. Finally, we provide extensive numerical results to verify the analytical derivations and the effectiveness of the proposed system design under various settings. [less ▲]