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 (Early Access) (2022)

For extensive coverage areas, multi-beam high throughput satellite (HTS) communication is a promising technology that plays a crucial role in delivering broadband services to many users with diverse ... [more ▼]

For extensive coverage areas, multi-beam high throughput satellite (HTS) communication is a promising technology that plays a crucial role in delivering broadband services to many users with diverse Quality of Service (QoS) requirements. This paper focuses on multi-beam HTS systems where all beams reuse the same spectrum. In particular, we propose a novel user scheduling and power allocation design capable of providing guarantees in terms of the individual QoS requirements while maximizing the system throughput under a limited power budget. Precoding is employed in the forward link to mitigate mutual interference among the users in multiple-access scenarios over different coherence time intervals. The combinatorial optimization structure from user scheduling requires an extremely high cost to obtain the global optimum even when a reduced number of users fit into a time slot. Therefore, we propose a heuristic algorithm yielding a good trade-off between performance and computational complexity, applicable to a static operation framework of geostationary (GEO) satellite networks. Although the power allocation optimization is signomial programming, non-convex on a standard form, the solution can be lower bounded by the global optimum of a geometric program with a hidden convex structure. A local solution to the joint user scheduling and power allocation problem is consequently obtained by a successive optimization approach. Numerical results demonstrate the effectiveness of our algorithms on GEO satellite networks by providing better QoS satisfaction combined with outstanding overall system throughput. [less ▲]

Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels

in IEEE Transactions on Wireless Communications (2022), 21(7), 5106-5128

Cell-Free Massive multiple-input multiple-output (MIMO) and reconfigurable intelligent surface (RIS) are two promising technologies for application to beyond-5G networks. This paper considers Cell-Free ... [more ▼]

Cell-Free Massive multiple-input multiple-output (MIMO) and reconfigurable intelligent surface (RIS) are two promising technologies for application to beyond-5G networks. This paper considers Cell-Free Massive MIMO systems with the assistance of an RIS for enhancing the system performance under the presence of spatial correlation among the engineered scattering elements of the RIS. Distributed maximum-ratio processing is considered at the access points (APs). We introduce an aggregated channel estimation approach that provides sufficient information for data processing with the main benefit of reducing the overhead required for channel estimation. The considered system is studied by using asymptotic analysis which lets the number of APs and/or the number of RIS elements grow large. A lower bound for the channel capacity is obtained for a finite number of APs and engineered scattering elements of the RIS, and closed-form expressions for the uplink and downlink ergodic net throughput are formulated in terms of only the channel statistics. Based on the obtained analytical frameworks, we unveil the impact of channel correlation, the number of RIS elements, and the pilot contamination on the net throughput of each user. In addition, a simple control scheme for optimizing the configuration of the engineered scattering elements of the RIS is proposed, which is shown to increase the channel estimation quality, and, hence, the system performance. Numerical results demonstrate the effectiveness of the proposed system design and performance analysis. In particular, the performance benefits of using RISs in Cell-Free Massive MIMO systems are confirmed, especially if the direct links between the APs and the users are of insufficient quality with high probability. [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 ▲]

Detection of Spoofing Attacks in Aeronautical Ad-Hoc Networks Using Deep Autoencoders

in IEEE Transactions on Information Forensics and Security (2022), 17

We consider an aeronautical ad-hoc network relying on aeroplanes operating in the presence of a spoofer. The aggregated signal received by the terrestrial base station is considered as “clean” or “normal” ... [more ▼]

We consider an aeronautical ad-hoc network relying on aeroplanes operating in the presence of a spoofer. The aggregated signal received by the terrestrial base station is considered as “clean” or “normal”, if the legitimate aeroplanes transmit their signals and there is no spoofing attack. By contrast, the received signal is considered as “spurious” or “abnormal” in the face of a spoofing signal. An autoencoder (AE) is trained to learn the characteristics/features from a training dataset, which contains only normal samples associated with no spoofing attacks. The AE takes original samples as its input samples and reconstructs them at its output. Based on the trained AE, we define the detection thresholds of our spoofing discovery algorithm. To be more specific, contrasting the output of the AE against its input will provide us with a measure of geometric waveform similarity/dissimilarity in terms of the peaks of curves. To quantify the similarity between unknown testing samples and the given training samples (including normal samples), we first propose a so-called deviation-based algorithm . Furthermore, we estimate the angle of arrival (AoA) from each legitimate aeroplane and propose a so-called AoA-based algorithm . Then based on a sophisticated amalgamation of these two algorithms, we form our final detection algorithm for distinguishing the spurious abnormal samples from normal samples under a strict testing condition. In conclusion, our numerical results show that the AE improves the trade-off between the correct spoofing detection rate and the false alarm rate as long as the detection thresholds are carefully selected. [less ▲]

Sleep quality and the evolution of the COVID- 19 pandemic in five European countries

in PLoS ONE (2022), 17(12), 0278971

Healthy and sustainable food shopping: a survey of intentions and motivations

in Frontiers in Nutrition (2022), 9

Joint Communications and Sensing for Hybrid Massive MIMO LEO Satellite Systems With Beam Squint

in 2022 IEEE International Conference on Communications Workshops (ICC Workshops) (2022)

To improve the efficient utilization of spectral and hardware resources, joint communications and sensing (JCS) has drawn extensive attention. Most existing JCS works focus on terrestrial networks and can ... [more ▼]

To improve the efficient utilization of spectral and hardware resources, joint communications and sensing (JCS) has drawn extensive attention. Most existing JCS works focus on terrestrial networks and can not be straightforwardly applied in satellite systems due to the significantly different electromagnetic wave propagation properties. In this work, we investigate the application of JCS in massive multiple-input multiple-output (MIMO) low earth orbit (LEO) satellite systems. We first charac-terize the statistical wave propagation properties by considering beam squint effects. Based on this analysis, we propose a beam squint-aware JCS technique for hybrid analog/digital massive MIMO LEO satellite systems exploiting statistical channel s-tate information. Simulation results demonstrate that both the wireless communications and target sensing can be operated simultaneously with satisfactory performance, and the beam squint effects can be efficiently mitigated with the proposed method in typical LEO satellite systems. [less ▲]

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 ▲]

Unlimited Sampling for FMCW Radars: A Proof of Concept

in 2022 IEEE Radar Conference (RadarConf22) (2022)

High-resolution FMCW radar systems are becoming an integral aspect of applications ranging from automotive safety and autonomous driving to health monitoring of infants and the elderly. This integration ... [more ▼]

High-resolution FMCW radar systems are becoming an integral aspect of applications ranging from automotive safety and autonomous driving to health monitoring of infants and the elderly. This integration provides challenging scenarios that require radars with extremely high dynamic range (HDR) ADCs; these ADCs need to avoid saturation while offering high-performance and high-fidelity data-acquisition. The recent concept of Unlimited Sensing allows one to achieve high dynamic range (HDR) acquisition by recording low dynamic range, modulo samples. Interestingly, oversampling of these folded measurements, with a sampling rate independent of the modulo threshold, is sufficient to guarantee their perfect reconstruction for band-limited signals. This contrasts with the traditional methodology of increasing the dynamic range by adding a programmable-gain amplifier or operating multiple ADCs in parallel. This paper demonstrates an FMCW radar prototype that utilises the unlimited sampling strategy. Our hardware experiments show that even with the use of a modulo measurements of lower precision, the US reconstruction is able to match the performances of the conventional acquisition. Furthermore, our real-time processing capability demonstrates that our “proof-of-concept” approach is a viable solution for HDR FMCW radar signal processing, thus opening a pathway for future hardware-software optimization and integration of this technology with other mainstream systems. [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 ▲]