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Under high-mobility scenarios, the traditional coherent demodulation schemes (CDS) have limited performance, because reference signals cannot effectively track the channel variations with an affordable overhead. As an alternative solution, non-coherent demodulation schemes (NCDS) based on differential modulation have been proposed. Even in the absence of reference signals, they are capable of outperforming the CDS with a reduced complexity. The literature on NCDS laid the theoretical foundations for simplified channel and signal models, often single-carrier and spatially uncorrelated flat-fading channels. This chapter explains the most recent results assuming orthogonal frequency division multiplexing (OFDM) signaling and realistic channel models.

Proceeding of: IEEE Global Communications Conference (GLOBECOM 2022) A novel time division duplex massive MIMO approach based on performing a blind channel estimation in the uplink using differentially encoded data and a precoding in the downlink, also with differentially encoded data, is proposed. In this system, the use of any type of explicit pilot symbol is completely avoided while maintaining spatial multiplexing capabilities in the downlink. We perform an analysis of the full system in terms or signal-to-interference-and-noise ratio (SINR) for the uplink and the downlink. The performance of the channel estimation using differentially encoded data is also analyzed, since it affects the performance of the downlink data transmission. A multi-user allocation strategy in an OFDM grid is proposed. The analysis is corroborated via numerical results and the proposed scheme is shown to outperform its coherent counterpart. This work has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie ETN TeamUp5G, grant agreement No. 813391, and the Spanish National Project IRENE-EARTH (PID2020-115323RB-C33) (MINECO/AEI/FEDER, UE).

Proceedings of IEEE GLOBECOM 2022: IEEE Global Communications Conference, 4-8 December 2022, Rio de Janeiro, Brazil. The Reconfigurable Intelligent Surfaces (RIS) constitute one of the prominent technologies for the next generation of wireless communications. They are mainly envisioned to efficiently enhance the signal coverage in cases where the direct communication link is weak or obstructed. Recently, beam training based on codebook selection has been proposed as a low-latency means for tuning the RIS phase profile according to a desired performance metric. However, it requires the transmission of reference signals to measure the performance with different RIS phase configurations available in the codebook, which reduces the spectral efficiency. In this paper, we consider the uplink of a Multiple-Input Signal-Output (MISO) communication system with Orthogonal Frequency-Division Multiplexing (OFDM) and present a novel scheme for simultaneous RIS phase configuration and data transmission. The proposed scheme is based on non-coherent differential modulation, which is deployed both in the beam training and the data transmission phases. In the former phase, it also enables energy measurement for the determination of the best RIS phase profile. Then, in the latter phase, a higher throughput can be established through the high gain reflective link. Our numerical results showcase that our proposal can double the system throughput with lower complexity, as compared to the generic state-of-the-art approach. This work has been funded by the Spanish National project IRENE-EARTH (PID2020-115323RB-C33/AEI /10.13039/501100011033) and the EU H2020 RISE-6G project under grant number 101017011.

Proceeding of: 31st Annual Conference of the European Association for Education in Electrical and Information Engineering (EAEEIE 2022), Coimbra, Portugal, 26 June-1 July 2022 Many of the new mobile communication devices will be things that power and monitor our homes, city infrastructure and transport. Controlling drones thousands of miles away, performing remote surgeries or being immersed in video with no latency will also be a huge game changer. Those are some of the few things that make the fifth generation (5G) a revolution expected to be a thrust to the economy. To that end, the design and density of deployment of new networks is also changing becoming more dense, what introduces new challenges into play. What else will it add to previous generations? The MOOC about Ultra-dense networks for 5G and its evolution has been prepared by the researchers of an European MSCA ITN, named TeamUp5G, and introduces the most important technologies that support 5G mobile communications, with an emphasis on increasing capacity and reducing power. The content spans from aspects of communication technologies to use cases, prototyping and the future ahead, not forgetting issues like interference management, energy efficiency or spectrum management. The aim of the MOOC is to fill the gap in graduation and post-graduation learning on content related to emerging 5G technologies and its applications, including the future 6G. The target audience involves engineers, researchers, practitioners and students. This paper describes the content and the learning outcomes of the MOOC, the main tasks and resources involved in its creation, the joint contributions from the academic and non-academic sector, and aspects like copyright compliance, quality assurance, testing and details on communication and enrollment, followed by the discussion of the lessons learned. This work has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie ETN TeamUp5G, grant agreement No. 813391.

Proceedings of: 2022 IEEE Wireless Communications and Networking Conference (WCNC), 10-13 April 2022, Austin, USA. Reconfigurable Intelligent Surfaces (RISs) are an emerging technology in the evolution towards the Sixth Generation (6G) of mobile communications. They are capable of enhancing the overall system performance and extending the coverage of the existing cells. They are built by a large amount of low-cost meta-elements that can be configured by tuning their phase shifts, and hence, the channel response can be constructively combined and forwarded to some specific direction. Many algorithms have been proposed to obtain the optimum phase shifts, generally assuming a single-carrier system and/or a medium-size RIS to constrain the complexity of the optimization process. In this work, we propose a flexible and scalable unsupervised learning model, capable of obtaining the best phase shifts for any scenario. Our proposal is able to handle multi-carrier waveforms and very large-size RIS, considering both continuous and discrete phase shifts. Besides, we also propose the use of clustering to reduce further the complexity while maintaining the performance. A comparison in terms of achievable rate and time execution is provided in order to show the superiority of our proposal against the existing solutions. This work has been funded by the Spanish National projects IRENE-EARTH (PID2020-115323RB-C33 / AEI/ 10.13039/501100011033) and AMATISTA (CDTI IDI20200861).

Augmented reality (AR) has been presented lately as one of the key technology fields in which 5G networks can become a disruptive tool, raising interest from both industry and academia. The main goal of this article is to extend the current state of the art of distributed AR studies and implementations by extracting the main AR algorithms' offloading requirements individually. This extension is further achieved by depicting the data flow between these algorithms and their hardware requirements. From the obtained results, we estimate a preliminary set of network key performance indicators (KPIs) for a subset of three examples of distributed AR implementations highlighting the necessity of 5G technologies and their ecosystem to unveil the full potential of AR. Finally, based on these KPls, we propose a set of 5G configuration parameters for a successful distributed AR implementation. As most of the described algorithms are also used in virtual reality (VR) applications, our contributions can facilitate future distributed implementations of both AR and VR applications. This work has received funding from the European Union (EU) Horizon 2020 research and innovation programme under the Marie Skodowska-Curie ETN TeamUp5G, grant agreement no. 813391.

Ponencia presentada en la Jornada de Innovación Docente 2021: aprendizaje activo, celebrada el 6 de julio de 2021 en la Universidad Carlos III de Madrid.

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This poster has been accepted for presentation at the IEEE Communication Theory Workshop (IEEE CTW 2018 ), 15-16 May, 2018, Miramar Beach, Florida. Massive MIMO combined with OFDM are key techniques in the evolution of mobile communications. In this context, to the best of our knowledge, the channel estimation and the equalizers have never been jointly considered. We propose an alternative low-complexity method to compute the ZF equalizers, which consists of exchanging the order of the interpolation and computation of the equalizer. For massive MIMO, this strategy provides the same performance and considerably lower number of operations, compared to the traditional scheme. This work has been partly funded by projects MACHINE (TSI-100102-2015-17), ELISA (TEC2014-59255-C3-3-R) and TERESA-ADA (TEC2017-90093-C3-2-R) (MINECO/AEI/FEDER, UE).

Ponencia presentada en: XXX Simposium Nacional de la Unión Científica Internacional de Radio, los dias 2 y 4 septiembre 2015, en Pamplona (españa). Video services are expected to become more than 70% of the mobile traffic in 2020. Broadcast and multicast service is the most efficient mechanism to deliver the same content to many users. Not only focusing on venue casting, but also distributing many other media such as software updates and breaking news, 5G broadcasting is a key driver to achieve the spectral efficiency needed for the 1,000 times traffic growth that is expected for the upcoming years. Improvements in some areas, such as resource allocation techniques for broadcast/multicast services, are needed. The utilization of the Conventional Multicast Scheme (CMS) approach for multicast resource allocation presents intrinsic inefficiencies, because of the different channel conditions of the users which demand the service. This paper presents some resource allocation strategies based on the use of multicast subgroups. We propose a multicast resource allocation algorithm including memory, which results in improvements of the service throughput at the time a high fairness among the users is guaranteed. In addition, an algorithm of joint resource allocation among multicast and unicast transmissions is developed. This strategy allows the system to take advantage of the subframes reserved for each purpose by the Long Term Evolution (LTE) standard, looking for the best joint allocation of the available resources, and results in important improvements in the service throughput This work was supported in part by the Spanish Ministry of Economy and Competitiveness, National Plan for Scientific Research, Development and Technological Innovation (IN-NPACTO subprogram), LTExtreme project (IPT-2012-0525-430000), and the projects TEC2011-29006-C03-03 (GRE3NSYST) and TEC2014-59255-C3-3-R (ELISA). Publicada

Proceeding of: 2nd International Conference on Wireless Communication Systems and Networks (MIC-Wireless 2015), Barcelona, August 7th-9th 2015 This paper investigates the use of bit loading al- gorithms in order to use ESIM OFDM in frequency selective channels. This work focuses on maximizing the bit rate minimiz- ing the loss of spectral efficiency because of the insertion of idle subcarriers. Besides, the modified ESIM OFDM is generalized to support groups of subcarriers of arbitrary size based on the number of idle subcarriers. The effect of this generalization, as well as the new bit distribution after using bit loading, on the peak to average power ratio (PAPR) and the bit error rate (BER) are analyzed. Additionally a novel way to evaluate the BER in such a system is proposed. The proposed scheme is shown to outperform the original ESIM OFDM performance in terms of PAPR, at the cost of a small degradation of the BER. This improvement in the PAPR makes the proposed scheme a good candidate for Optical Wireless Communication (OWC) systems, and This work has been partly funded by project TEC2014-59255-C3-3-R (ELISA)

This proceeding at: The 22nd European Signal Processing Conference (EUSIPCO), took place 2014, September, 01-05 in Lisbon (Portugal). An interference aware precoding scheme based on limited channel state information at the transmitter (CSIT) is consid-ered for its use in the downlink of a cellular system. The transmitter precoder used is based on an MMSE-ZF criterion in order to maximize the user rate while the interference to other users is reduced. The proposed scheme also exploits the network topology, so that each BS can categorize the users into two groups, according to the level of interference that the BS is introducing in those users. On the receiver end, each user makes use of the whole channel state information at the receiver (CSIR) by employing an MMSE filter. This approach enables a reduction in the complexity of the system, while improving the performance of the whole network. This work has been partially funded by research projects COMONSENS (CSD2008-00010), and GRE3N (TEC2011-29006-C03-03. Publicado

Interference in a cellular network is one of the main impairments that needs to be overcome. Coordination among the Base Stations may enable the use of the interference to improve the transmission rate at the cost of increased computational complexity and more stringent backhaul and feedback requirements. Practical problems of global coordination can be reduced through clustering which, in turn, will introduce Out of Cluster Interference (OCI). OCI can seriously hamper the advantages brought by precoding techniques like Block Diagonalization (BD). In this work we propose a mixed transmission strategy using BD and Single User transmission that is able to overcome the problems introduced by the OCI, in combination with a low complexity scheduling algorithm that enables an increased transmission rate in a multiuser scenario.

This proceeding at: European Wireless 2014, took place 2014 Mai, 14-16, in Barcelona (España). The event web site of http://www.ew2014.org/ Mobile video service is one of the most increasing uses expected in future generation cellular networks, including multicast video services. Based upon Evolved Multimedia Broadcast and Multicast Service (eMBMS) available with 3rd Generation Partnership Project (3GPP) release 9, Long Term Evolution (LTE) can provide broadcast/multicast content delivery with a single-frequency network mode. This means sending the same multimedia content to a mass audience within a specific area. However, it is not always possible to use multicast transmission to every user because of their different channel conditions, so unicast transmission should also be used to fulfill Quality of Service (QoS) requirements for multicast services. This paper proposes a Joint Multicast/Unicast Scheduling (JMUS) strategy for multicast service delivery. This method is based on dynamic optimization at each LTE frame, obtaining the optimal Modulation and Coding Scheme (MCS) for multicast transmission, the optimal number of subframes reserved for multicast transmission and allocating the remaining resources using a unicast scheduling metric for guaranteed data-rate. The goal of the scheduling technique proposed is to maximize the overall throughput, guaranteeing a target bit rate for all the users in the area. A new JMUS with dynamic optimization is presented to improve QoS performance. Finally, a fast search algorithm is evaluated to approach the optimal values for dynamic optimization with an order of magnitude fewer iterations than using exhaustive search. This work was supported in part by the Spanish Min-istry of Economy and Competitiveness, National Plan for Scienti?c Research, Development and Technological Inno-vation (INNPACTO subprogram), LTExtreme project (IPT- 2012-0525-430000) and the subproject TEC2011-29006-C03-03 (GRE3N-SYST). Publicado

The proceeding at: 21st European Signal Processing Conference (EUSIPCO 2013), took place 2013, September 09-13, in Marrakech, Septiembre 2013. Block Diagonalization (BD) is a linear precoding transmission technique able to achieve full multiplexing gain in multiple antenna systems. In this work we present a Multiple-Input Multiple-Output (MIMO) implementation based on Orthogonal Frequency Division Multiplexing (OFDM) made up of a transmitter with 4 antennas and 2 users equipped with 2 antennas each one, which allows us to evaluate the performance of BD in indoor scenarios. First, the theoretic achievable rates are obtained for the measured channel in an offline evaluation. After that, the bit error rate performance is evaluated regarding the system sum throughput. To the best of our knowledge, this is the first time that BD performance is validated using a multiuser MIMO testbed. This work has been partially funded by research projects COMONSENS (CSD2008-000 1 0), and GRE3N (TEC20 11-29006-C03-02). Publicado

Audiovisuales: Entrevista 1ª parte. Disponible en: https://arcamm.uc3m.es/arcamm/# .-- Entrevista 2ª parte. Disponible en: https://arcamm.uc3m.es/arcamm/?item=dd05fdc9e25f37f2c047c1a699d56627 .-- Entrevista 3ª parte. Disponible en: https://arcamm.uc3m.es/arcamm/?item=15e5fc3a1fae74e560dd60fa31e1ef36 .-- Entrevista completa. Disponible en: http://www.youtube.com/watch?feature=player_embedded&v=i_BgPT0O_WM Internet es ya parte de la vida cotidiana. Las tecnologías de la información y las comunicaciones han transformado radicalmente el mundo de los negocios, la educación, la comunicación o el ocio, en apenas una década.

Audiovisulaes: Entrevista a Esther Arias, Oficina Española de Patentes y Marcas. Disponible en https://www.youtube.com/watch?v=K38IC0NDctE . La gestión interna de los derechos de propiedad industrial e intelectual procedentes de los resultados de la investigación desarrollada en la Universidad Carlos III de Madrid es competencia de su Parque Científico. Dependiente del vicerrectorado de Investigación, es el responsable de la transferencia de tecnología y conocimiento a las empresas.Un servicio de la UC3M es la plataforma ORIÓN-UC3M, en que la persona investigadora o gestora del grupo de investigación introduce, a medida que se producen, sus ofertas en la plataforma. Contiene: El Parque Científico UC3M, gestor de los derechos de propiedad industrial e intelectual (p. 22) .Los inventores opinan. La experiencia de proteger sus resultados con el Parque Científico UC3M / Valentín Miguel Moreno, Ana García–Armada (p. 23) .-- Más opiniones / Raúl Sánchez–Reíllo, Manuel Armenteros (p. 24).

Proceeding at: Opnetwork2013, took place 2013, August, 1-2, in Washington (USA) Mobile video is one of the most popular uses for mobile broadband networks. Based upon evolved Multimedia Broadcast Multicast Service (eMBMS) available with 3GPP Release 9, LTE can provide broadcast/multicast content delivery with a single-frequency network mode that sends the same multimedia content to a mass audience within a specific area. In this paper, we describe a performance analysis carried out for this type of network using OPNET Modeler. We propose a new algorithm to create, dynamically, Multicast-Broadcast Single Frequency Network (MBSFN) areas that will optimize the efficiency of multicast transmissions of events to a large number of users in a limited area. This work was supported in part by the National Scientific Research, Development and Technological Innovation, LTExtreme project (IPT-2012-0525-430000). Publicado

La ponencia presentada en: XXVIII Simposium Nacional de la Unión Científica Internacional de Radio. URSI 2013. Santiago de Compostela, 11-13 Sept. 2013. Mobile video is one of the most popular uses for mobile broadband networks. Based upon evolved Multimedia Broadcast Multicast Service (eMBMS) available with 3GPP release 9, LTE can provide broadcast/multicast content delivery with a single-frequency network mode that send the same multimedia content to mass audience within a specific area. In this paper, we carry out a Signal to Interference plus Noise Ratio (SINR) performance analysis for this type of networks, using OPNET Modeler tool. Several scenarios have been considered, with different number of users receiving multicast video data from the same source and different number of eNodeBs. This study includes the comparison of SINR in scenarios with 1, 3 and 7 different frequencies using multicast without MBMS or with MBMS SFN. The results show a comparison in the cell throughput between the different scenarios, as well as the performance obtained using different sizes of MBMS SFN areas. Este trabajo ha sido en parte financiado por el Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, proyecto LTExtreme (IPT-2012- 0525-430000). Publicado