Signal Processing | Dr. Jorge Querol

RPDMA: A PAPR-Aware Multiple Access Scheme

Thu, 01 Jan 2026 00:00:00 +0000

Abstract & Overview

This paper proposes a novel Multiple Access (MA) scheme called Ramanujan Periodic subspace Division Multiple Access (RPDMA) for subcarrier sizes N = 2m, m ∊ N, to address the high Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiple Access (OFDMA). Building on the properties of Ramanujan subspaces, we design transmitter and receiver models that allocate users on a subspace-wise basis, ensuring zero inter-user interference, providing inherent frequency diversity. We analyze the computational complexity of OFDMA, SC-FDMA, and RPDMA, and find that RPDMA has substantially lower per-user transmitter complexity than both OFDMA and SC-FDMA, while its receiver complexity is comparable to SC-FDMA and higher than that of OFDMA. We further introduce a generalized framework, termed Nested Periodic-subspace Division Multiple Access (NPDMA), which unifies both RPDMA and OFDMA under a common family of multi-carrier MA schemes. We derive the theoretical PAPR of RPDMA and demonstrate its superiority over OFDMA. The analysis is validated through numerical simulations under two multi-user scenarios with diverse Quality of Service (QoS) requirements. The results demonstrate that RPDMA achieves lower PAPR than both OFDMA and SC FDMA, with users assigned larger subspaces benefiting from even greater PAPR reduction. We prove that both the sum and per-user Spectral Efficiency (SE) of RPDMA are identical to those of OFDMA and SC-FDMA. In terms of Bit Error Rate (BER), SC-FDMA achieves the best performance, while RPDMA still outperforms OFDMA as the SNR increases.

Publication Metadata

Authors: Goli Srikanth, Shaik Basheeruddin Shah, Nazar T. Ali, Vijay Kumar Chakka, Jorge Querol, Ahmed Altunaiji, Dragan I. Olćan
Venue: IEEE Open Journal of Vehicular Technology (2026)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/ojvt.2026.3661153
Open Access Repository: ORBiLu – University of Luxembourg

A Study of Lunar Proximity Networks: Scenarios and Architectures

Mon, 01 Jan 2024 00:00:00 +0000

Abstract & Overview

High data rate, adaptive, inter networked proximity communications for Space, part of the ESA project PROSPECT, is focused on selecting the best-fit terrestrial technology for lunar proximity communications scenarios. This study explores the concept of lunar proximity networks, which play an essential role in enabling direct and short-range communication between devices on the lunar surface. The study is organized to analyze scenarios where these networks are applicable, the potential communication architectures, and the technologies that could be utilized. Furthermore, it includes a trade-off analysis that focuses on the lunar channel model and technology selection, followed by simulation results that offer valuable insights into the performance and feasibility of these networks. The study ends with recommendations for the design and implementation of lunar proximity networks, highlighting their pivotal role in future lunar missions to support the long-term human mission to the Moon.

Publication Metadata

Authors: Mouhamad CHEHAITLY, Houcine CHOUGRANI, Sumit KUMAR, Youssouf DRIF, Jorge Querol, Stefano PETRI, Leonardo TURCHI, Symeon CHATZINOTAS
Venue: The IEEE Wireless in Space and Extreme Environments (2024)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/wisee61249.2024.10850404
Open Access Repository: ORBiLu – University of Luxembourg

Edge Learning Optimization in Task-Oriented NOMA Communications for Autonomous Vehicle Perception

Mon, 01 Jan 2024 00:00:00 +0000

Abstract & Overview

The Internet of Vehicles (IoV) is undergoing swift advancements in capability and intelligence, poised to facilitate a diverse range of innovative applications. Within the IoV, edge learning empowers intelligent applications and services by leveraging data -driven tasks. Therefore, in this paper, we propose optimizing the edge learning error prediction within an edge-supported Non-Orthogonal Multiple Access (NOMA) in task-oriented communications. Specifically, we consider three autonomous vehicle perception tasks, called: object detection, traffic sign, and weather classification. For this purpose, we propose a novel approach based on the Particle Swarm Optimization (PSO) algorithm to jointly minimize the edge learning error and optimize power allocation variables. Moreover, we investigate alternative benchmark schemes, including Quantum Particle Swarm Optimization, Cuckoo Search, and Butterfly Op-timization algorithms. Satisfactorily, our simulations substantiate the superiority of the PSO algorithm over the baseline schemes, delivering superior performance with reduced computation time.

Publication Metadata

Authors: Carla E Garcia, Mario R Camana, Abuzar B Mohammad, Jorge Querol, Symeon Chatzinotas
Venue: 2024 IEEE Wireless Communications and Networking Conference (WCNC) (2024)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/wcnc57260.2024.10570514

Rate-Splitting Multiple Access for Secure Communications Over CR MISO SWIPT Systems With Non-Linear EH Users

Mon, 01 Jan 2024 00:00:00 +0000

Abstract & Overview

In this paper, we investigate a secure transmission for a rate-splitting multiple-access (RSMA)-based multiple-input single-output (MISO) underlay cognitive radio (CR) system. The proposed network is composed of a set of secondary users (SUs) that utilize simultaneous wireless information and power transfer (SWIPT) technology and an additional set of non-linear energy harvesting (EH) users. Moreover, the system model under consideration is exposed to multiple eavesdroppers. Thus, we propose to minimize the transmit power intended to the SUs and EH users while maximizing the artificial noise (AN) generated by the secondary transmitter, aiming to counter eavesdroppers’ wiretaps while satisfying the quality-of-service constraints. Therefore, we develop a novel approach based on ant colony regression (ACOR) and semidefinite relaxation (SDR) methods to solve the challenging and non-convex problem which is further transformed into a bilevel optimization problem. Afterward, we investigate a comparative solution based on the particle swarm optimization (PSO) algorithm, the successive convex approximation (SCA) technique, and analyze the incidence of linear and non-linear EH designs. In addition, we compare the RSMA-based scheme with non-orthogonal multiple-access (NOMA), space-division multiple access (SDMA), and zero-forcing (ZF) techniques. Satisfactorily, simulation results prove the proposed ACOR-SDR framework achieves better performance and lower complexity than its counterparts.

Publication Metadata

Authors: Carla E. García, Mario R. Camana, Jorge Querol, Symeon Chatzinotas
Venue: IEEE Transactions on Green Communications and Networking (2024)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/tgcn.2024.3404891
Open Access Repository: ORBiLu – University of Luxembourg

End-to-end performance evaluation of slp waveforms

Sun, 01 Jan 2023 00:00:00 +0000

Abstract & Overview

In this paper, we investigate the demodulation and decoding of the symbol-level precoded (SLP) signal using the conventional logarithmic likelihood ratio (LLR) and low-density parity check (LDPC) decoding algorithms operating in real-time on the software-defined radio (SDR) receiver. Its conventional forward error correction (FEC) is designed assuming symmetric additive white Gaussian noise (AWGN). While SLP generates asymmetric constellation point clouds it is unclear if it can achieve similar FEC gains in an end-to-end coded setup. The receiver is implemented based on the DVB-S2X standard. It estimates multi-beam interference-limited channel coefficients by using the orthogonal pilots embedded into the DVB-S2X frames to facilitate precoding at the transmitter. After the received frames are fully synchronized the payload symbols are decoded in two stages: soft decision using the LLR and hard decision using the LDPC decoders. We benchmark the bit error rate (BER) and frame error rate (FER) of the complete decoding chain while using the zero-forcing (ZF) and the selected SLP channel-interference canceling techniques. The conducted in-lab experiments show that the SLP can improve BER and FER performance in the conventional receiving and decoding design for symmetric constellations while achieving its original optimization goals.

Publication Metadata

Authors: Jevgenij Krivochiza, Juan Carlos Merlano Duncán, Jorge Querol, Symeon Chatzinotas
Venue: IEEE Access (2023)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/access.2023.3327643
Open Access Repository: ORBiLu – University of Luxembourg

Short-Packet Communication Assisted Reliable Control of UAV for Optimum Coverage Range

Sun, 01 Jan 2023 00:00:00 +0000

Abstract & Overview

The reliability of command and control (C2) operation of the UAV is one of the crucial aspects for the success of UAV applications beyond 5G wireless networks. In this paper, we focus on the short-packet communication to maximize the coverage range of reliable UAV control. We quantify the reliability performance of the C2 transmission from a multi-antenna ground control station (GCS), which also leverages maximal-ratio transmission beamforming, by deriving the closed-form expression for the average block error rate (BLER). To obtain additional insights, we also derive the asymptotic expression of the average BLER in the high-transmit power regime and subsequently analyze the possible UAV configuration space to find the optimum altitude. Based on the derived average BLER, we formulate a joint optimization problem to maximize the range up to which a UAV can be reliably controlled from a GCS. The solution to this problem leads to the optimal resource allocation parameters including blocklength and transmit power while exploiting the vertical degrees of freedom for UAV placement. Finally, we present numerical and simulation results to corroborate the analysis and to provide various useful design insights.

Publication Metadata

Authors: Sourabh Solanki, Vibhum Singh, Sumit Gautam, Jorge Querol, Symeon Chatzinotas
Venue: ICC 2023-IEEE International Conference on Communications (2023)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/icc45041.2023.10279207
Open Access Repository: ORBiLu – University of Luxembourg

System Analysis of Lunar Computations Communication Architectures

Sun, 01 Jan 2023 00:00:00 +0000

Abstract & Overview

This research contribution by Laura Chikosman, Miguel Angel OLIVARES MENDEZ, Juan Carlos MERLANO DUNCAN, Sumit Kumar et al. (2023), published in Space Resources Week, investigates “System Analysis of Lunar Computations Communication Architectures” within the domains of Satellite Communications, Signal Processing. The work is part of Dr. Jorge Querol’s research portfolio in advanced satellite communications, non-terrestrial networks (NTN), and radio-frequency signal processing at SnT (University of Luxembourg) and UPC-BarcelonaTech.

Publication Metadata

Authors: Laura Chikosman, Miguel Angel OLIVARES MENDEZ, Juan Carlos MERLANO DUNCAN, Sumit Kumar, Chandan Kumar SHEEMAR, Symeon Chatzinotas, Loveneesh Rana, Andreas Hein, Youssouf Drif, Swetha Varadarajulu, Jorge Querol
Venue: Space Resources Week (2023)
Research Areas: Satellite Communications, Signal Processing

Wireless and networking technologies for social distancing-indoor and outdoor

Fri, 01 Jan 2021 00:00:00 +0000

Abstract & Overview

This chapter reviews the suitability of the most relevant wireless and networking communications technologies (e.g. GNSS, cellular, WiFi, Bluetooth and RFID) for the implementation of social distancing applications such as interpersonal distancing, real-time area monitoring, or geo-fencing.

Publication Metadata

Authors: Jorge Querol, Alejandro González, Vu Nguyen Ha, Sumit Kumar, Symeon Chatzinotas
Venue: Institution of Engineering and Technology eBooks (2021)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1049/pbte104e_ch3

Altimetric performance of the GEROS experiment at the ISS

Fri, 01 Jan 2016 00:00:00 +0000

Abstract & Overview

The GNSS rEflectometry, Radio Occultation and Scatterometry onboard the International Space Station (GEROS-ISS) is an innovative experiment for climate research, proposed in 2011 within a call of the European Space Agency (ESA) for installation at the ISS. This international proposal was the only one selected for further studies by ESA out of ~25 submitted ones. In this work, an updated assessment of the instrument performance for the near-nadir altimetry (GNSS-R) mode and scatterometry is assessed, including the effect of the inter-modulation signals, and the expected degradation due to presence of radio-frequency interference coming from DME/TACAN systems. These results correspond to the study lead by Airbus Defence and Space-Spain, one of the two parallel Phase A studies conducted by ESA.

Publication Metadata

Authors: A. Camps, H. Park, R. Onrubia, D. Pascual, Jorge Querol, A. Alonso-Arroyo, J. Benito, A. Andres-Beivide, S. Moreno, X. Ballesteros, M. Segarra, R. Vilaseca, A. Rius, M. Martin-Neira
Venue: 2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS) (2016)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/igarss.2016.7730468

Impact of multi-path by ISS structure on GEROS-ISS measured waveforms

Fri, 01 Jan 2016 00:00:00 +0000

Abstract & Overview

The GNSS rEflectometry, Radio Occultation and Scatterometry onboard the International Space Station (GEROS-ISS) experiment consists of the installation of a GNSS reflectometry (GNSS-R) instrument on the International Space Station (ISS). Due to the complex structure of ISS, the GEROS-ISS instrument suffers from multipath effects. The collected signals are not only from received directly, but also after multiple reflections in the ISS structure. This work analyzes the multipath effect of the GEROS-ISS instrument based on the ISS structure. Using the ray tracing simulation, all rays reaching the instrument after one or two reflections are computed, as well as the corresponding additional delays. This information, together with the direction of arrival to the antenna arrays (up and down-looking), and the co- and cross-polar antenna patterns is used to assess the impact of multipath on the waveforms are demonstrated.

Publication Metadata

Authors: Hyuk Park, Adriano Camps, Ivan Sekulic, J. M. Rius, Daniel Pascual, Alberto Alonso-Arroyo, Jorge Querol, Raul Onrubia
Venue: 2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS) (2016)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/igarss.2016.7730463

Improvement of PAU/PARIS end-to-end performance simulator (P 2 EPS): Land scattering including topography

Fri, 01 Jan 2016 00:00:00 +0000

Abstract & Overview

This work presents an improvement of the P2EPS end-to-end simulator to assess the performances of Global Navigation Satellite System Reflectometry (GNSS-R) space missions over land. Beyond the single specular reflection model, topography effects are included. In order to avoid the computational burden of facet approach based on the bi-static radar model, the Phong reflection model is employed. By calculating the delay, Doppler frequency, and relative intensity of scattered points, the topography effects can be accounted for as a sort of impulse response in the delay, and Doppler domains to be convolved with the Woodward Ambiguity function.

Publication Metadata

Authors: Hyuk Park, Adriano Camps, Daniel Pascual, Alberto Alonso-Arroyo, Jorge Querol, Raul Onrubia
Venue: 2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS) (2016)
Research Areas: Satellite Communications, Signal Processing
DOI: 10.1109/igarss.2016.7730464

MCU Controlled DC-DC Buck/Boost Converter for Supercapacitors

Sun, 01 Jan 2012 00:00:00 +0000

Abstract & Overview

This work is focused on DC to DC conversion, what is a crucial function to enable the use of supercapacitors for energy storage. A theoretical study and comparison of methods, algorithms and techni …

Publication Metadata

Authors: Jorge Querol
Venue: Conference Paper (2012)
Research Areas: Satellite Communications, Signal Processing