A Deep Learning-Based Strategy to Predict Self-Interference in SFN DTT

This article belongs to the Proceedings of The 4th XoveTIC Conference[Abstract] A deep learning-based strategy for the analysis of the self-interference in single frequency networks (SFNs) for digital terrestrial television (DTT) broadcasting is considered. Several laboratory measurements were performed to create a dataset that relates the self-interference parameters and some quality metrics of the resulting received signal. The laboratory setup emulates an SFN scenario with two DTT transmitters. The strongest received signal and the relative values of attenuation and delay between the signals stand for the input parameters. The modulation error ratio (MER) of the strongest received signal, the MER of the resulting signal, and the SFN gain (SFNG) are the output parameters. This dataset is used to train four different multi-layer perceptron (MLP) models to predict accurate maps of interference and signal quality metrics. The considered models are suitable as complements for any multiple frequency network (MFN) coverage software with the capability to return the signal strength and the position data. This way, the SFN self-interference behavior can be predicted by considering only a proper description of the MFN coverage.This work has been funded by the Xunta de Galicia (by grant ED431C 2020/15, and grant ED431G2019/01 to support the CITIC, Centre for Information and Communications Technology Research, from the University System of Galicia), the Agencia Estatal de Investigación of Spain (by grants RED2018-102668-T and PID2019-104958RB-C42) and ERDF funds of the EU (FEDER Galicia 2014–2020 & AEI/FEDER Programs, UE), and the predoctoral grant BES-2017-081955.Xunta de Galicia; ED431C 2020/15Xunta de Galicia; ED431G2019/0

Eavesdropping and Jamming via Pilot Attacks in 5G Massive MIMO

Cursos e Congresos, C-155[Abstract] In thiswork, we investigate pilot attacks for 5G single-cell multi-user massive multipleinput multiple-output (MaMIMO) systems with a single-antenna active eavesdropper and a single-antenna jammer operating in time-division duplex (TDD) schemes. Firstly, we describe the attacks when the base station (BS) estimates the channel state information (CSI) based on the uplink pilot transmissions. Finally, we propose a reinforcement learning (RL)-based framework for maximizing the system sum rate that proved robust to the eavesdropping and jamming attacksCITIC is funded by the Xunta de Galicia through the collaboration agreement between the Consellería de Cultura, Educación, Formación Profesional e Universidades and the Galician universities for the reinforcement of the research centres of the Galician University System (CIGUS)

Deep Contextual Bandit and Reinforcement Learning for IRS-Assisted MU-MIMO Systems

© 2023 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/TVT.2023.3249353.[Abstract]: The combination of multiple-input multiple-output (MIMO) systems and intelligent reflecting surfaces (IRSs) is foreseen as a critical enabler of beyond 5G (B5G) and 6G. In this work, two different approaches are considered for the joint optimization of the IRS phase-shift matrix and MIMO precoders of an IRS-assisted multi-stream (MS) multi-user MIMO (MU-MIMO) system. Both approaches aim to maximize the system sum-rate for every channel realization. The first proposed solution is a novel contextual bandit (CB) framework with continuous state and action spaces called deep contextual bandit-oriented deep deterministic policy gradient (DCB-DDPG). The second is an innovative deep reinforcement learning (DRL) formulation where the states, actions, and rewards are selected such that the Markov decision process (MDP) property of reinforcement learning (RL) is appropriately met. Both proposals perform remarkably better than state-of-the-art heuristic methods in scenarios with high multi-user interference.This work has been supported by grants ED431C 2020/15 and ED431G 2019/01 (to support the Centro de Investigación de Galicia “CITIC”) funded by Xunta de Galicia and ERDF Galicia 2014-2020; and by grants PID2019-104958RB-C42 (ADELE) and BES-2017-081955 funded by MCIN/AEI/10.13039/501100011033.Xunta de Galicia; ED431C 2020/15Xunta de Galicia; ED431G 2019/0

Lattice-Based Analog Mappings for Low-Latency Wireless Sensor Networks

© 2023 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/JIOT.2023.3273194.[Abstract]: We consider the transmission of spatially correlated analog information in a wireless sensor network (WSN) through fading single-input and multiple-output (SIMO) multiple access channels (MACs) with low-latency requirements. A lattice-based analog joint source-channel coding (JSCC) approach is considered where vectors of consecutive source symbols are encoded at each sensor using an n -dimensional lattice and then transmitted to a multiantenna central node. We derive a minimum mean square error (MMSE) decoder that accounts for both the multidimensional structure of the encoding lattices and the spatial correlation. In addition, a sphere decoder is considered to simplify the required searches over the multidimensional lattices. Different lattice-based mappings are approached and the impact of their size and density on performance and latency is analyzed. Results show that, while meeting low-latency constraints, lattice-based analog JSCC provides performance gains and higher reliability with respect to the state-of-the-art JSCC schemes.This work was supported in part by the Xunta de Galicia under Grant ED431C 2020/15, and in part by MCIN/AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR under Grant PID2019-104958RB-C42 (ADELE), Grant TED2021-130240B-I00 (IVRY), and Grant BES-2017-081955. CITIC is funded by Xunta de Galicia through the collaboration agreement between the Consellería de Cultura, Educación, Formación Profesional e Universidades, and the Galician universities for the strengthening of the research centers of the Galician University System (CIGUS).Xunta de Galicia; ED431C 2020/1

Wideband User Grouping for Uplink Multiuser mmWave MIMO Systems With Hybrid Combining

[Abstract] Analog-digital hybrid precoding and combining schemes constitute an interesting approach to millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems due to the low hardware complexity and/or low power required for its deployment. However, the design of the hybrid precoders and combiners of a wideband multiuser (MU) mmWave MIMO system is challenging because the signal processing in the analog domain is constrained to be frequency flat. Furthermore, the number of radio frequency (RF) chains limits the number of individual streams that a common base station (BS) can simultaneously serve. This work jointly addresses the user scheduling, the user precoder design, and the BS hybrid combining design for the uplink of wideband MU mmWave MIMO systems. On the one hand, user precoding and BS hybrid combining are jointly designed to minimize the impact of having frequency-flat RF components. On the other hand, a number of users larger than the number of RF chains are served at the BS by employing a distributed quantizer linear coding (DQLC)-based non-orthogonal multiple access (NOMA) scheme. The use of this encoding strategy also allows exploiting the spatial correlation between the source information. Simulation results show remarkable performance gains of the proposed approaches for wideband mmWave MIMO hardware-constrained systems.10.13039/501100010801-Xunta de Galicia (Grant Number: ED431C 2020/15) 10.13039/501100010801-Centro de Investigación de Galicia CITIC (Grant Number: ED431G2019/01) 10.13039/501100011033-Agencia Estatal de Investigación of Spain (Grant Number: RED2018-102668-T and PID2019-104958RB-C42) European Regional Development Funds (ERDF) of the EU (ERDF Galicia 2014-2020 & AEI/ERDF programs, UE) Predoctoral (Grant Number: BES-2017-081955)Xunta de Galicia; ED431C 2020/15Xunta de Galicia; ED431G2019/0

User Grouping for the Uplink of Multiuser Hybrid mmWave MIMO

[Abstract] Hybrid analog/digital schemes for precoding/combining have proved to be a low-complexity and/or low-power strategy to obtain reasonable beamforming gains in multiuser millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems. Hybrid precoding/combining performs jointly baseband processing and analog processing in the radio frequency (RF) domain. In these systems, the number of RF chains limits the maximum number of streams simultaneously handled by the transceivers. In the uplink of a multiuser mmWave MIMO system, the hardware reduction based on hybrid transceivers is limited by the number of data streams that must be simultaneously served by the centralized node. Most works approach hybrid transceiver design by considering more RF chains than data streams, an unrealistic assumption when the number of nodes is large. On the other hand, statistically independent information is conventionally assumed in multiuser mmWave systems. This assumption does not hold in scenarios like wireless sensor networks (WSNs), where the sources produce correlated information. In this paper, by enabling inter-user correlation exploitation, we propose a grouping approach to handle a high number of individual sources with a limited number of RF chains through distributed quantizer linear coding (DQLC) mappings. The allocation of the users per group and the hybrid design of the combiner at the common central node to serve the grouped users is also analyzed. We also propose a hybrid minimum mean square error (MMSE) combining design in order to exploit the spatial correlation between the sources in a conventional uncoded mmWave uplink. Simulation results show the performance advantages of the proposed approaches in various hardware-constrained system settings.10.13039/501100010801-Xunta de Galicia (Grant Number: ED431G2019/01) 10.13039/501100011033-Agencia Estatal de Investigaci??n (Grant Number: TEC2016-75067-C4-1-R, RED2018-102668-T and PID2019-104958RB-C42) BES-2017-081955Xunta de Galicia; ED431G2019/0

Alternating Minimization for Wideband Multiuser IRS-Aided MIMO Systems Under Imperfect CSI

© 2023 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/TSP.2023.3336166[Abstract]: This work focuses on wideband intelligent reflecting surface (IRS)-aided multiuser MIMO systems. One of the major challenges of this scenario is the joint design of the frequency-dependent base station (BS) precoder and user filters, and the IRS phase-shift matrix which is frequency flat and common to all the users. In addition, we consider that the channel state information (CSI) is imperfect at both the transmitter and the receivers. A statistical model for the imperfect CSI is developed and exploited for the system design. A minimum mean square error (MMSE) approach is followed to determine the IRS phase-shift matrix, the transmit precoders, and the receiving filters. The broadcast (BC)- multiple access channel (MAC) duality is used to solve the optimization problem following an alternating minimization approach. Numerical results show that the proposed approach leads to substantial performance gains with respect to baseline strategies that neglect the inter-user interference and do not optimize the IRS phase-shift matrix. Further performance gains are obtained when incorporating into the system design the statistical information of the channel estimation errors.This work was supported by Grants PID2019-104958RB-C42 (ADELE), PID2022-137099NB-C42 (MADDIE), and BES-2017-081955 funded by MCIN/AEI/10.13039/501100011033. José P. González-Coma thanks the Defense University Center at the Spanish Naval Academy for all the support provided for this research

Intelligent Reflective Surfaces for Wireless Networks: An Overview of Applications, Approached Issues, and Open Problems

This article belongs to the Special Issue Reconfigurable Intelligent Surface (RIS) for Wireless Communications[Abstract] An intelligent reflective surface (IRS) is a novel and revolutionizing communication technology destined to enable the control of the radio environment. An IRS is a real-time controllable reflectarray with a massive number of low-cost passive elements which introduce a phase shift to the incoming signals from the sources before the propagation towards the destination. This technology introduces the notion of a smart propagation environment with the aim of improving the system performance. In this paper, we provide a comprehensive literature overview on IRS technology, including its basic concepts and reconfiguration, as well as its design aspects and applications for wireless communication systems. We also study the performance metrics and the setups considered in recent publications related to IRS and provide suggestions of future research lines based on still unexplored use cases in the state-of-the-art.This work has been funded by the Xunta de Galicia (by grant ED431C 2020/15, and grant ED431G2019/01 to support the Centro de Investigación de Galicia “CITIC”), the Agencia Estatal de Investigación of Spain (by grants RED2018-102668-T and PID2019-104958RB-C42) and ERDF funds of the EU (FEDER Galicia 2014–2020 & AEI/FEDER Programs, UE), and the predoctoral grant BES-2017-081955Xunta de Galicia; ED431C 2020/15Xunta de Galicia; ED431G2019/0

Métodos Avanzados de Codificación y Procesamiento de Señales para Sistemas MIMO Multiusuario

Programa Oficial de Doutoramento en Tecnoloxías da Información e das Comunicacións en Redes Móbiles. 5029V01[Resumo] Os sistemas de comunicacións sen fíos están a experimentar un crecemento constante nos últimos anos e agárdase que crezan aínda máis nos próximos anos axudados polo uso de novas técnicas de codificación e procesamento de sinal. Os servizos multimedia baseados en datos son cada vez máis demandados para actividades laborais e de socialización, e requiren de novas técnicas de codificación e procesamento do sinal para poderen ser despregados de forma efectiva. Por tanto, é de esperar que estas técnicas acheguen melloras canto á velocidade, a eficiencia enerxética, a fiabilidade, entre outros aspectos. Nos últimos anos a aplicación das técnicas de codificación avanzadas xogou un papel imprescindible para despregar as redes emerxentes de comunicacións sen fíos. Hoxe en día, a gran maioría dos sistemas de comunicación deséñanse seguindo unha aproximación dixital e de acordo co principio de separación fonte-canle. Con todo, os sistemas de comunicación baseados na optimización conxunta da codificación de fonte e canle (coñecidos pola súa sigla en inglés JSCC) seguen espertando interese nos investigadores, especialmente no caso de transmisión de sinais analóxicos. Os investigadores baséanse en que esta estratexia tamén é capaz de aproximarse aos límites teóricos, ademais de ofrecer vantaxes con respecto aos sistemas dixitais como, por exemplo, unha baixa complexidade e un mínimo retardo. A aplicación de novas técnicas para procesar o sinal é esencial na implementación das redes emerxentes de comunicacións sen fíos. Especificamente, na banda de ondas milimétricas (ou mmWave), a cal se considera para satisfacer os requisitos das novas xeracións de redes móbiles (5G e B5G), as arquitecturas híbridas foron recentemente propostas como un enfoque innovador que permite aumentar a eficiencia enerxética. Estas arquitecturas baséanse en dividir a precodificación dixital, usada en sistemas que fan uso de múltiples antenas tanto nos transmisores como nos receptores (MIMO, pola súa sigla en inglés), nunha parte analóxica de baixo consumo enerxético e outra dixital. A maioría dos enfoques de codificación e precodificación MIMO están condicionados pola canle de comunicacións sen fíos que, normalmente, segue sendo incontrolable. Por outra banda, o paradigma de control do medio de propagación vén recibindo moita atención por parte da comunidade científica no ámbito de redes emerxentes sen fíos. Este paradigma foi utilizado anteriormente para aplicacións de radar e satélite mediante o emprego de superficies reflectoras. Porén, non se consideraba para aplicacións móbiles debido á imposibilidade de implementar superficies reflectoras que fixesen fronte ao dinamismo das canles sen fíos por mor da mobilidade dos usuarios presente nestes sistemas. Con todo, os avances acadados na actualidade no estudo dos metamateriais cos que se fabrican estas superficies proporcionan garantías de reconfigurabilidade para habilitar o axuste en tempo real dos cambios de fase nas superficies reflectoras intelixentes (IRSs, pola súa sigla en inglés). Nesta tese, analizamos e deseñamos novos métodos de codificación de sinais analóxicos baseados no principio de optimización JSCC. Tamén analizamos e implementamos novas técnicas de procesamiento do sinal aplicadas ás arquitecturas híbridas na banda de mmWave. Finalmente, desenvolvemos técnicas de procesamento do sinal para establecer un mellor control do medio a través do uso de IRSs.[Resumen] Los sistemas de comunicaciones inalámbricas experimentan un crecimiento sin interrupciones en los últimos años, y se espera que se desarrollen aún más en los próximos años, acompañados en su despliegue por novedosas técnicas de codificación y procesamiento de señales. Los servicios multimedia y basados en datos son cada vez más demandados para actividades laborales y de socialización, y requieren de novedosas técnicas de codificación y procesamiento de señales para su despliegue. Se espera que estas técnicas aporten mejoras en cuanto a la tasa de datos, la eficiencia energética, la fiabilidad, etc. La aplicación de las técnicas de codificación juega un papel imprescindible en el despliegue de las redes emergentes de comunicaciones inalámbricas. Hoy en día, la gran mayoría de los sistemas de comunicaciones se diseñan siguiendo una aproximación digital y de acuerdo con el principio de separación. Sin embargo, los sistemas de comunicaciones basados en la optimización conjunta de la codificación de fuente y canal (JSCC, por sus siglas en inglés) siguen despertando interés en los investigadores, especialmente para la transmisión de señales analógicas. Los investigadores se basan en que la estrategia JSCC también es capaz de aproximarse a los límites teóricos, además de ofrecer ventajas con respecto a los sistemas digitales como, por ejemplo, baja complejidad y mínimo retardo. En la actualidad, la aplicación de novedosas técnicas de procesamiento de señales es esencial en la implementación de las redes emergentes de comunicaciones inalámbricas. Específicamente, en la banda de ondas milimétricas (mmWave), la cual ha despertado gran interés para el despliegue de nuevas generaciones móviles (5G y posteriores), las arquitecturas híbridas han ofrecido recientemente un enfoque innovador que permite aumentar la eficiencia energética. Estas arquitecturas están basadas en desacoplar la precodificación digital usada en sistemas de múltiples entradas y múltiples salidas (MIMO, por sus siglas en inglés) en una parte analógica de bajo consumo energético y otra digital. La mayoría de los enfoques de codificación y precodificación MIMO están condicionados por el canal inalámbrico de comunicaciones, el cual normalmente permanece incontrolable. Afortunadamente, el paradigma de control del medio de propagación está siendo considerado actualmente para redes emergentes de comunicaciones inalámbricas. Este paradigma se había empleado anteriormente para aplicaciones de radares y satélites a través de superficies reflectantes, pero no se consideraba para escenarios con movilidad debido a la incapacidad de implementar superficies reflectantes que hicieran frente al dinamismo de los canales inalámbricos. Sin embargo, los avances obtenidos en la actualidad en el estudio de los metamateriales ofrecen garantías de reconfigurabilidad en tiempo real de las superficies reflectantes inteligentes (IRSs, por sus siglas en inglés). En esta tesis analizamos e implementamos novedosos métodos de codificación de señales analógicas basados en el principio de optimización JSCC. También analizamos e implementamos novedosas técnicas de procesamiento de señales aplicadas a las arquitecturas híbridas en mmWave y con el objetivo de establecer un mejor control del medio de comunicaciones a través de las IRSs.[Abstract] Wireless communication systems have experienced a non-stopping growth in the last few years and are expected to grow even more in the following years, supported in their deployment by novel coding and signal processing techniques. Multimedia and mobile data-based services are increasingly in demand for online work and socialization purposes, and novel coding and signal processing techniques are required to cope with their implementation. These techniques are expected to accomplish improvements in terms of data rates, energy efficiency, reliability, etc. The use of encoding techniques plays an essential role in the deployment of emerging wireless communications networks. Nowadays, most communication systems are designed following a digital approach and according to the separation principle. However, communication systems based on the optimization of joint source-channel coding (JSCC) still arouse the interest of researchers, especially in the case of analog signal transmission. The researchers rely on the capability of this strategy to approach theoretical limits and offer advantages over digital systems, e.g., low complexity and minimal delay. Nowadays, the application of novel signal processing techniques is essential for the implementation of emerging wireless communications networks. Specifically, in the millimeter-wave (mmWave) band—which has received high interest for the deployment of 5G and beyond—hybrid architectures have recently offered an innovative approach to increase the energy efficiency of the systems. These architectures are based on decoupling the digital precoding used in multiple-input multiple-output (MIMO) systems into a low-complexity analog part and a baseband part. Most approaches related to the source coding and the MIMO precoding are conditioned to the wireless channel, which usually remains uncontrollable. Fortunately, the paradigm of propagation environment control is being considered for emerging wireless communications networks. This paradigm had previously been used for radar and satellite applications by means of reflecting surfaces but it was not considered for mobile communications due to the inability to cope with the dynamic wireless channels because of user mobility. However, currently, the advances obtained in the study of meta-materials provide certain guarantees for reconfigurability by enabling real-time phase shifts in the intelligent reflecting surfaces (IRSs). In this thesis, we analyze and implement new coding methods for analog signals based on the JSCC optimization principle. We also analyze and implement novel signal processing techniques applied to hybrid architectures in the mmWave band. Finally, we develop signal processing techniques for better control of the propagation environment through the IRSs

Análisis del comportamiento de la ganancia de SFN para DTMB

En los últimos años se ha venido desplegando en Cuba el servicio de Televisión Digital Terrestre (TDT) de acuerdo con el estándar DTMB en su esquema para redes de múltiples frecuencias (MFN). Sin embargo, como parte de la evolución de esta tecnología, algunos países han migrado hacia el despliegue de redes de una sola frecuencia (SFN), pues este esquema provee un uso más eficiente del espectro radioeléctrico. Estudios sobre SFN muestran que es posible con este esquema conseguir una distribución más homogénea de la calidad de la señal recibida y, además, las señales provenientes de transmisores diferentes pueden ser combinadas de forma constructiva para obtener una ganancia en la recepción. No obstante, algunos autores consideran que un aumento de la intensidad total de la señal recibida, no siempre se corresponde con una mejor recepción. Es por esto que se han considerado parámetros propios de la recepción como: relación señal a ruido (SNR) y razón de modulación errónea (MER), en lugar de la intensidad de la señal recibida para evaluar la ganancia. En este artículo se presenta un análisis, a partir de los resultados de mediciones de laboratorio, que permite caracterizar la ganancia de SFN (SFNG) para DTMB, considerando el parámetro MER como medida de la calidad de la señal recibida. Además, se presentan los resultados obtenidos de evaluar la capacidad de recepción de un receptor comercial en SFN con presencia de multitrayectos con valores de retardo cercanos a la duración del intervalo de guarda