Effective Rate of RIS-aided Networks with Location and Phase Estimation Uncertainty

in Proceedings of IEEE Wireless Communications and Networking Conference (WCNC) (2022, May)

Demand and Interference Aware Adaptive Resource Management for High Throughput GEO Satellite Systems

in IEEE Open Journal of the Communications Society (2022)

The scarce spectrum and power resources, the inter-beam interference, together with the high traffic demand, pose new major challenges for the next generation of Very High Throughput Satellite (VHTS ... [more ▼]

The scarce spectrum and power resources, the inter-beam interference, together with the high traffic demand, pose new major challenges for the next generation of Very High Throughput Satellite (VHTS) systems. Accordingly, future satellites are expected to employ advanced resource/interference management techniques to achieve high system spectrum efficiency and low power consumption while ensuring user demand satisfaction. This paper proposes a novel demand and interference aware adaptive resource management for geostationary (GEO) VHTS systems. For this, we formulate a multi-objective optimization problem to minimize the total transmit power consumption and system bandwidth usage while matching the offered capacity with the demand per beam. In this context, we consider resource management for a system with full-precoding, i.e. all beams are precoded; without precoding, i.e. no precoding is applied to any beam; and with partial precoding, i.e. only some beams are precoded. The nature of the problem is non-convex and we solve it by jointly using the Dinkelbach and Successive Convex Approximation (SCA) methods. The simulation results show that the proposed method outperforms the benchmark schemes. Specifically, we show that the proposed method requires low resource consumption, low computational time, and simultaneously achieves a high demand satisfaction. [less ▲]

Differential Phase Compensation in Over-the-air Precoding Test-bed for a Multi-beam Satellite

Scientific Conference (2022, April 10)

This article presents a closed-loop differential phase compensation system for a precoding-enabled multibeam satellite forward link and its validation by live experiments on a GEO satellite scenario. The ... [more ▼]

This article presents a closed-loop differential phase compensation system for a precoding-enabled multibeam satellite forward link and its validation by live experiments on a GEO satellite scenario. The precoding operation avoids inter-beam interference and maximizes the spectrum efficiency by full frequency reuse as an alternative to the traditional two-color or four-color reuse methods proposed in the DVB-S2 standard. However, the satellite payload introduces differential phase and frequency impairments, which can degrade the precoding performance. This work describes the implementation of the differential phase and frequency tracking and compensation loop in an end-to-end testbed over a multibeam satellite system with independent local oscillators. The developed system performs end-to-end real-time communication over the satellite link, including channel measurements and precompensation. Results are validated by an over-the-air demonstration using two beams of the SES-14 multibeam satellite. Each beam is transmitted by independent transponders, which results in differential frequency and phase offsets due to the transponder undisciplined local oscillators. This phase offset makes it impossible to use precoding without the phase compensation loop. We prove that the implemented system can successfully track and compensate the differential phase and frequency to improve precoding performance. [less ▲]

UAV Relay-Assisted Emergency Communications in IoT Networks: Resource Allocation and Trajectory Optimization

in IEEE Transactions on Wireless Communications (2022), 21(3), 1621-1637

Unmanned aerial vehicle (UAV) communication hasemerged as a prominent technology for emergency communi-cations (e.g., natural disaster) in the Internet of Things (IoT)networks to enhance the ability of ... [more ▼]

Unmanned aerial vehicle (UAV) communication hasemerged as a prominent technology for emergency communi-cations (e.g., natural disaster) in the Internet of Things (IoT)networks to enhance the ability of disaster prediction, damageassessment, and rescue operations promptly. A UAV can bedeployed as a flying base station (BS) to collect data from time-constrained IoT devices and then transfer it to a ground gateway(GW). In general, the latency constraint at IoT devices and UAV’slimited storage capacity highly hinder practical applicationsof UAV-assisted IoT networks. In this paper, full-duplex (FD)radio is adopted at the UAV to overcome these challenges. Inaddition, half-duplex (HD) scheme for UAV-based relaying isalso considered to provide a comparative study between twomodes (viz., FD and HD). Herein, a device is considered tobe successfully served iff its data is collected by the UAV andconveyed to GW timely during flight time. In this context,we aim to maximize the number of served IoT devices byjointly optimizing bandwidth, power allocation, and the UAVtrajectory while satisfying each device’s requirement and theUAV’s limited storage capacity. The formulated optimizationproblem is troublesome to solve due to its non-convexity andcombinatorial nature. Towards appealing applications, we firstrelax binary variables into continuous ones and transform theoriginal problem into a more computationally tractable form.By leveraging inner approximation framework, we derive newlyapproximated functions for non-convex parts and then develop asimple yet efficient iterative algorithm for its solutions. Next,we attempt to maximize the total throughput subject to thenumber of served IoT devices. Finally, numerical results showthat the proposed algorithms significantly outperform benchmarkapproaches in terms of the number of served IoT devices andsystem throughput. [less ▲]

Hybrid Analog/Digital Precoding for Downlink Massive MIMO LEO Satellite Communications

in IEEE Transactions on Wireless Communications (2022), 21(8), 5962-5976

Massive multiple-input multiple-output (MIMO) is promising for low earth orbit (LEO) satellite communications due to the potential in enhancing the spectral efficiency. However, the conventional fully ... [more ▼]

Massive multiple-input multiple-output (MIMO) is promising for low earth orbit (LEO) satellite communications due to the potential in enhancing the spectral efficiency. However, the conventional fully digital precoding architectures might lead to high implementation complexity and energy consumption. In this paper, hybrid analog/digital precoding solutions are developed for the downlink operation in LEO massive MIMO satellite communications, by exploiting the slow-varying statistical channel state information (CSI) at the transmitter. First, we formulate the hybrid precoder design as an energy efficiency (EE) maximization problem by considering both the continuous and discrete phase shift networks for implementing the analog precoder. The cases of both the fully and the partially connected architectures are considered. Since the EE optimization problem is nonconvex, it is in general difficult to solve. To make the EE maximization problem tractable, we apply a closed-form tight upper bound to approximate the ergodic rate. Then, we develop an efficient algorithm to obtain the fully digital precoders. Based on which, we further develop two different efficient algorithmic solutions to compute the hybrid precoders for the fully and the partially connected architectures, respectively. Simulation results show that the proposed approaches achieve significant EE performance gains over the existing baselines, especially when the discrete phase shift network is employed for analog precoding. [less ▲]

Throughput Maximization for Backscatter- and Cache-Assisted Wireless Powered UAV Technology

in IEEE Transactions on Vehicular Technology (2022), 71(5), 5187-5202

This paper investigates a wireless powered unmanned aerial vehicle (UAV) communication network with backscatter and caching technologies. Specifically, we assume a self-energized UAV with a cache memory ... [more ▼]

This paper investigates a wireless powered unmanned aerial vehicle (UAV) communication network with backscatter and caching technologies. Specifically, we assume a self-energized UAV with a cache memory is deployed as a flying backscatter device (BD), term the UAV-enabled BD (UB), to relay the source’s signals to the destination. Whereas the source S can act as a wireless charging station or a base station to supply power or transmit information to the UB using the dynamic time splitting (DTS) method. The UAV utilizes its harvested energy for backscattering (i.e., passive communication) and transmit information (i.e., active communication) to the destination. In this context, we aim to maximize the total throughput by jointly optimizing the DTS ratio and the UB’s trajectory with caching capability at the UB. The formulation is troublesome to solve since it is a non-convex problem. To find solutions, we decompose the original problem into two sub-problems, whereas we first optimize the DTS ratio for a given UB’s trajectory and the UB’s trajectory optimization for a given DTS ratio. By using the KKT conditions, a closed-form expression for the optimal value of the DTS ratio is obtained, greatly reducing the computation time. Moreover, the solution of the second sub-problem can be acquired by adopting the successive convex approximation (SCA) technique. Consequently, an efficient alternating algorithm is proposed by leveraging the block coordinate descent (BCD) method. To show the advantages of the proposed BCD-based algorithm, we also provide the solution of the original problem applying the inner approximation (IA) method. Finally, the intensive numerical results demonstrate that our proposed schemes achieve significant throughput gain in comparison to the benchmark schemes. [less ▲]

User Scheduling and Power Allocation for Precoded Multi-Beam High Throughput Satellite Systems With Individual Quality of Service Constraints

in IEEE Transactions on Vehicular Technology (2022)

Recurrent Design of Probing Waveform for Sparse Bayesian Learning Based DOA Estimation

in ICASSP 2022 - 2022 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) (2022)

Direction-of-arrival (DOA) estimation can be represented as a sparse signal recovery problem and effectively solved by sparse Bayesian learning (SBL). For the DOA estimation in active sensing, the SBL ... [more ▼]

Direction-of-arrival (DOA) estimation can be represented as a sparse signal recovery problem and effectively solved by sparse Bayesian learning (SBL). For the DOA estimation in active sensing, the SBL-based estimation error is related to the transmitted probing waveform. Therefore, it is expected to improve the estimation by waveform optimization. In this paper, we propose a recurrent scheme of waveform design by sequentially leveraging on the previous-round SBL estimates. Within this scheme, we formulate the waveform design problem as a minimization of the SBL estimation variance, which is non-convex and then solved by a majorization-minimization based algorithm. The simulations demonstrate the efficacy of the proposed design scheme in terms of avoiding incorrect detection and accelerating the DOA estimation convergence. Further, the results indicate that the waveform design is essentially a beampattern shaping methodology. [less ▲]

Physical Layer Security Analysis of SWIPT-Enabled Cooperative Wireless IoT Networks in the Presence of Friendly Jammer and Eavesdropper

in IEEE Internet of Things Journal (2022), 9(21),

—Physical layer security (PLS) and simultane ous wireless information and power transfer (SWIPT) in cooperative relaying have gained great interest as technolo gies for security and energy enhancement in ... [more ▼]

—Physical layer security (PLS) and simultane ous wireless information and power transfer (SWIPT) in cooperative relaying have gained great interest as technolo gies for security and energy enhancement in Internet-of Things (IoT) networks. In this work, we investigate PLS for a SWIPT- and AF-enabled cooperative wireless IoT system, consisting of one source, multiple energy harvesting (EH) relays, and one destination, in the presence of an eaves dropper that tries to overhear the confidential information. Furthermore, an EH-friendly jammer is deployed to trans mit jamming signals aimed at the eavesdropper to improve the security system. In this context, a low complexity, sub optimal, but efficient relay selection method is proposed. More specifically, the relay is selected to convey informa tion such that it has the best channel to the source. Based on the proposed system model, the performance analysis of intercept probability (IP), asymptotic IP, and non-zero secrecy probability (NZSP) is analyzed by considering the time switching (TS)-based relaying strategy. Particularly, Tan N. Nguyen is with the Wireless Communications Re search Group, Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam. (e mail:nguyennhattan@tdtu.edu.vn). Dinh-Hieu Tran, Symeon Chatzinotas, and Bjorn Ottersten are with ¨ the Interdisciplinary Centre for Security, Reliability and Trust (SnT), the University of Luxembourg, Luxembourg. (e-mail: {hieu.tran-dinh, symeon.chatzinotas, bjorn.ottersten} @uni.lu). Miroslav Voznak is with VSB - Technical University of Ostrava, 17. listopadu 15/2172, 708 33 Ostrava - Poruba, Czech Republic. (e-mail:miroslav.voznak@vsb.cz). H. V. Poor is with the Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ 08544 USA. (email: poor@princeton.edu). Byung-Seo Kim is with the Department of Software and Com munications Engineering, Hongik University, Sejong 30016, South Korea (e-mail: jsnbs@hongik.ac.kr). Corresponding author: Van-Duc Phan is at Faculty of Automobile Technology, Van Lang University, Ho Chi Minh City, Vietnam. (email: duc.pv@vlu.edu.vn). This research was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the grant SP2021/25 and e-INFRA CZ (ID:90140). the exact closed-form expression of IP is achieved applying modified Bessel function expansion. Finally, Monte-Carlo simulations are employed to corroborate the correctness and the efficiency of our mathematical analysis. [less ▲]

Throughput Enhancement in FD- and SWIPT-enabled IoT Networks over Non-Identical Rayleigh Fading

in IEEE Internet of Things Journal (2022), 9(12),

Simultaneous wireless information and power transfer (SWIPT) and full-duplex (FD) have emerged as prominent technologies to overcome limited energy re sources and improve spectral efficiency (SE) in ... [more ▼]

Simultaneous wireless information and power transfer (SWIPT) and full-duplex (FD) have emerged as prominent technologies to overcome limited energy re sources and improve spectral efficiency (SE) in Internet-of Things (IoT) networks. This article investigates the outage and throughput performance for a decode-and-forward (DF) relay SWIPT system, which consists of one source, multiple relays, and one destination. Herein, the relay nodes can harvest energy from the source’s signal and operate in the FD mode. Further, a sub-optimal, low-complexity, yet efficient relay selection scheme is proposed. Specifically, one relay is selected to convey information from a source to a destination so that it achieves the best channel from source to relays. Then, by considering two relaying strategies, termed static power splitting-based relaying (SPSR) and optimal dynamic power splitting-based relaying (ODPSR), performance analysis in terms of outage probability (OP) and throughput are performed for each one. Notably, the independent and non-identically distributed (i.n.i.d.) Rayleigh fading channels are considered, which poses new challenges for obtaining analytical expressions. In this context, we derive exact closed-form expressions for the OP and throughput of both SPSR and ODPSR schemes. Moreover, the optimal power splitting ratio of ODPSR is obtained to maximize the achievable capacity at the destination. Finally, extensive numerical and simulation results are presented to confirm our analytical findings. Both the simulation and analytical results show the superiority of ODPSR over SPSR. [less ▲]