Common Radio Resource Management Strategies for Quality of Service Support in Heterogeneous Wireless Networks

Hoy en día existen varias tecnologías que coexisten en una misma zona formando un sistema heterogéneo. Además, este hecho se espera que se vuelva más acentuado con todas las nuevas tecnologías que se están estandarizando actualmente. Hasta ahora, generalmente son los usuarios los que eligen la tecnología a la que se van a conectar, ya sea configurando sus terminales o usando terminales distintos. Sin embargo, esta solución es incapaz de aprovechar al máximo todos los recursos. Para ello es necesario un nuevo conjunto de estrategias. Estas estrategias deben gestionar los recursos radioeléctricos conjuntamente y asegurar la satisfacción de la calidad de servicio de los usuarios. Siguiendo esta idea, esta Tesis propone dos nuevos algoritmos. El primero es un algoritmo de asignación dinámica de recusos conjunto (JDRA) capaz de asignar recursos a usuarios y de distribuir usuarios entre tecnologías al mismo tiempo. El algoritmo está formulado en términos de un problema de optimización multi-objetivo que se resuelve usando redes neuronales de Hopfield (HNNs). Las HNNs son interesantes ya que se supone que pueden alcanzar soluciones sub-óptimas en cortos periodos de tiempo. Sin embargo, implementaciones reales de las HNNs en ordenadores pierden esta rápida respuesta. Por ello, en esta Tesis se analizan las causas y se estudian posibles mejoras. El segundo algoritmo es un algoritmo de control de admisión conjunto (JCAC) que admite y rechaza usuarios teniendo en cuenta todas las tecnologías al mismo tiempo. La principal diferencia con otros algorimos propuestos es que éstos últimos toman las dicisiones de admisión en cada tecnología por separado. Por ello, se necesita de algún mecanismo para seleccionar la tecnología a la que los usuarios se van a conectar. Por el contrario, la técnica propuesta en esta Tesis es capaz de tomar decisiones en todo el sistema heterogéneo. Por lo tanto, los usuarios no se enlazan con ninguna tecnología antes de ser admitidos.Calabuig Soler, D. (2010). Common Radio Resource Management Strategies for Quality of Service Support in Heterogeneous Wireless Networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/7348Palanci

Optimum Transmission Through the Multiple-Antenna Gaussian Multiple Access Channel

"(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, 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 components of this work in other works."[EN] This paper studies the optimal points in the capacity region of Gaussian multiple access channels (GMACs) with constant fading, multiple antennas, and various power constraints. The points of interest maximize general rate objectives that arise in practical communication scenarios. Achieving these points constitutes the task of jointly optimizing the timesharing parameters, the input covariance matrices, and the order of decoding used by the successive interference cancellation receiver. To approach this problem, Carathéodory s theorem is invoked to represent time-sharing and decoding orders jointly as a finite-dimensional matrix variable. This variable enables us to use variational inequalities to extend results pertaining to problems with linear rate objectives to more general, potentially nonconvex, problems, and to obtain a necessary and sufficient condition for the optimality of the transmission parameters in a wide range of problems. Using the insights gained from this condition, we develop and analyze the convergence of an algorithm for solving, otherwise daunting, GMAC-based optimization problems.D. Calabuig was supported by Marie Curie International Outgoing Fellowship within the European Commission, Research Executive Agency, through the COMIC Project under Grant 253990. R. H. Gohary and H. Yanikomeroglu were supported in part by Huawei Canada Company, Ltd., and in part by the Ontario Ministry of Economic Development and Innovations within the Ontario Research Fund through the Research Excellence Program. This paper was presented at the 2013 IEEE International Symposium on Information Theory and the 2014 IEEE International Workshop on Signal Processing Advances in Wireless Communications.Calabuig Soler, D.; Gohary, RH.; Yanikomeroglu, H. (2016). Optimum Transmission Through the Multiple-Antenna Gaussian Multiple Access Channel. IEEE Transactions on Information Theory. 62(1):230-243. https://doi.org/10.1109/TIT.2015.2502244S23024362

Key Enabling Technologies for 5G: Millimeter-Wave and Massive MIMO

[EN] 5G wireless networks are expected to operate with orders of magnitude higher performance than the current 4G deployments. The demand for 5000 times higher data rates leads to the necessity of finding new techniques to increase spectral efficiency and of exploring new frequency bands above 6 GHz. It has been proved that from UHF up to C band, a significant increase in system spectral efficiency can be reached through various techniques, such as Coordinated Multi-Point (CoMP), Massive Multiple-Input-Multiple-Output (MIMO), and interference management and cancellation; still, the resulting performance will not cope with the full expectations of IMT-2020 and 5G-PPP requirements for 5G networks, mainly in terms of offering 10 Gbps peak data rates with connection densities of 100 k¿1 M devices/km2. To overcome this limitation, the future architecture of such 5G networks is being defined to be deployed on small cells and to use higher frequency bands, such as super high frequency (SHF, 3¿30 GHz) or extremely high frequency (EHF, 30¿300 GHz), also referred as to centimeter and millimeter wave bands, respectively.Cardona Marcet, N.; Correia, LM.; Calabuig Soler, D. (2017). Key Enabling Technologies for 5G: Millimeter-Wave and Massive MIMO. International Journal of Wireless Information Networks. 24(3):201-203. doi:10.1007/s10776-017-0366-zS20120324

Configurable node density generation with application to hotspot modelling

Mobility models are very relevant mainly when studying the performance of wireless systems by means of computer simulations. The main problem arises when deciding the best mobility model for a particular application. In some cases, it is very important to emulate hotspots or, in general, zones with different user (or node) densities. Current models do not allow complete control over hotspots, or in other words, they do not allow any general node density to be defined in the simulation area. Usually, when hotspots are modelled, closed zones are created with different numbers of users in each area, thus ensuring a fixed node density in each area. However, this approach results in an unfair comparison among users since they cannot move across zones. This paper proposes a new mechanism to solve these drawbacks. Using this mechanism, any general node density can be emulated allowing nodes to move around the entire simulation area. Any mobility model can be applied together with this density control mechanism, provided that the mobility model ensures a uniform node distribution. © 2010 Elsevier Ltd.This work has been funded by the Spanish Ministry of Science and Innovation under project TEC2008-06817-C02-01/TEC.Calabuig Soler, D.; Monserrat Del Río, JF.; Cardona Marcet, N. (2011). Configurable node density generation with application to hotspot modelling. Mathematical and Computer Modelling. 53(11-12):2229-2237. https://doi.org/10.1016/j.mcm.2010.08.028S222922375311-1

Fairness-Driven Fast Resource Allocation for Interference-Free Heterogeneous Networks

Resource allocation in heterogeneous wireless networks is a complex problem. This letter addresses this problem maximizing the sum of logarithms of received rates. From this function, and using the Karush-Kuhn-Tucker (KKT) conditions, this paper proposes an iterative algorithm for allocating resources, which is much faster than conventional techniques. This fast response can be used to optimize larger regions, getting closer to the performance of global and centralized algorithms. © 2012 IEEE.This work was supported by a Marie Curie International Outgoing Fellowship of the European Commission under the project COMIC.Calabuig Soler, D.; Monserrat Del Río, JF.; Cardona Marcet, N. (2012). Fairness-Driven Fast Resource Allocation for Interference-Free Heterogeneous Networks. IEEE Communications Letters. 16(7):1092-1095. doi:10.1109/LCOMM.2012.051512.120720S1092109516

Multi-user non-coherent detection for downlink MIMO communication

© 2014 IEEE. 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.[EN] Current cellular technologies are based on the concept of coherent communication, in which the channel matrix used for demodulation is estimated via reference or pilot signals. Coherent systems, however, involve a significant increase of the signalling overhead, especially when the number of transmission points is increased or when the mobile channel changes rapidly, which motivates the use of non-coherent techniques. This letter extends the use of non-coherent communications to a multi-user (MU) multiple-input multiple-output (MIMO) framework by combining superposition coding with a reduced-complexity detection method. Numerical results confirm that our scheme achieves higher user rates than non-coherent MU transmission based on time multiplexing. In addition to the well-known sum-rate gain of MU systems, an extra performance gain given by downlink non-coherent MU communication is shown and qualitatively justified.This work was performed in the framework of the FP7 project ICT-317669 METIS, supported in part by the European Union. The authors would like to acknowledge the contributions of their colleagues in METIS, although the views expressed are those of the authors and do not necessarily represent the project. The associate editor coordinating the review of this manuscript and approving it for publication was Prof. Chandra Ramabhadra Murthy.Roger Varea, S.; Calabuig Soler, D.; Cabrejas Peñuelas, J.; Monserrat Del Río, JF. (2014). Multi-user non-coherent detection for downlink MIMO communication. IEEE Signal Processing Letters. 21(10):1225-1229. https://doi.org/10.1109/LSP.2014.2330854S12251229211

Distribution of Road Hazard Warning Messages to Distant Vehicles in Intelligent Transport Systems

© 2018 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng 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.[EN] The efficient distribution of intelligent transport system (ITS) messages is fundamental for the deployment and acceptance of ITS applications by mobile network operators and the automotive industry. In particular, the distribution of road hazard warning (RHW) messages to distant vehicles requires special mechanisms. In this case, the combination of direct communication between vehicles and the wide area coverage provided by cellular networks might be crucial not only for reducing the data transmission costs but also for improving the timeliness of ITS information. Moreover, the application of clustering and cluster head selection mechanisms among vehicles can increase the efficiency of hybrid vehicular and cellular communication networks. This paper introduces a novel cluster head selection technique for the distribution of RHW messages, and proposes an implementation of another legacy technique that was originally intended for mobile ad-hoc networks (MANETs). This paper evaluates the performance of these techniques by the means of computer simulations in two scenarios with distinct congestion and propagation conditions. The simulation results show the potential benefit of hybrid networks compared with pure cellular transmissions, especially, if the novel cluster head selection technique is used.Calabuig Soler, D.; Martín-Sacristán, D.; Monserrat Del Río, JF.; Botsov, M.; Gozálvez Serrano, D. (2018). Distribution of Road Hazard Warning Messages to Distant Vehicles in Intelligent Transport Systems. IEEE Transactions on Intelligent Transportation Systems. 19(4):1152-1165. https://doi.org/10.1109/TITS.2017.2718103S1152116519

Distributed Hybrid Precoding for Indoor Deployments Using Millimeter Wave Band

[EN] DistributedAntenna Systems (DAS) are an alternative of network deployment that allows reducing the distance between transmitter and receiver by distributing the antennas throughout the coverage area. Moreover, the performance of the millimeter wave (mmWave) band can be significantly high within short transmitter-receiver distances. In this paper, the potential benefits of DAS deployments in the mmWave band are studied. To this aim, a distributed hybrid precoding (DHP) solution with remote antenna unit (RAU) selection capabilities is proposed and analyzed in an indoor DAS working in mmWaves and compared to two other indoor deployment strategies: a conventional cellular system with colocated antenna arrays and a small cell deployment. Theresults show that, using DHP, DAS not only brings huge gains to cell-edge users rate but also increases system capacity, becoming the best overall deployment. Further simulations including practical limitations have revealed that DAS using DHP is quite robust to combiner losses, although its performance is significantly degraded by outdated channel reports.This work has been supported by Ministerio de Economia y Competitividad, Spain (BES-2012-055975 and TEC2014-60258-C2-1-R), and by the European FEDER funds.Giménez Colás, S.; Calabuig Soler, D.; Roger Varea, S.; Monserrat Del Río, JF.; Cardona Marcet, N. (2017). Distributed Hybrid Precoding for Indoor Deployments Using Millimeter Wave Band. Mobile Information Systems. 2017:1-12. https://doi.org/10.1155/2017/5751809S112201

Time-frequency Grassmannian signalling for MIMO multi-channel-frequency-flat systems

In this paper, we consider the application of non-coherent Grassmannian signalling in practical multi-channel-frequency-flat multiple-input multiple-output (MIMO) wireless communication systems. In these systems, Grassmannian signalling, originally developed for single-channel block-fading systems, is not readily applicable. In particular, in such systems, the channel coefficients are constant across time and frequency, which implies that spectrally-efficient signalling ought to be jointly structured over these domains. To approach this goal, we develop a concatenation technique that yields a spectrally-efficient time-frequency Grassmannian signalling scheme, which enables the channel coherence bandwidth to be regarded as an additional coherence time. This scheme is shown to achieve the high signal-to-noise ratio non-coherent capacity of MIMO channels when the fading coefficients are constant over a time-frequency block. This scheme is also applicable in fast fading systems with coherence bandwidth exceeding that of one subchannel. The proposed scheme is independent of the symbol duration, i.e., the channel use duration, and is thus compatible with the transmit filter designs in current systems.The work of the first and second authors is supported, in part, by the Natural Sciences and Engineering Research Council of Canada (NSERC). This work is also supported, in part, by Huawei Canada Co., Ltd., in part, by the Ontario Ministry of Economic Development and Innovation's ORF-RE (Ontario Research Fund-Research Excellence) program, and, in part, by the Ministerio de Ciencia e Innovacion (project number TEC2011-27723-C02-02). The associate editor coordinating the review of this paper and approving it for publication was Z. Wang.Fouad, YMM.; Gohary, RH.; Cabrejas Peñuelas, J.; Yanikomeroglu, H.; Calabuig Soler, D.; Roger Varea, S.; Monserrat Del Río, JF. (2015). Time-frequency Grassmannian signalling for MIMO multi-channel-frequency-flat systems. IEEE Communications Letters. 19(3):475-478. https://doi.org/10.1109/LCOMM.2014.2386873S47547819

ESTUDIO DE LA ADAPTACIÓN AL ENLACE EN EL SISTEMA DE COMUNICACIONES MÓVILES 3.5G HSDPA

RESUMENLa tecnología HSDPA (High Speed Downlink Packet Access) es una evolución de UMTS (Universal Mobile Telecommunications System) creada por el 3GPP (3rd Generation Partnership Project) con el objetivo de aumentar la capacidad de transmisión en el enlace descendente. Su mejora se basa en la utilización de un canal compartido de comunicación gestionado de forma eficiente desde la estación base - por medio de un packet scheduler -, la utilización de mecanismos de retransmisión y combinación de información avanzados – hybrid ARQ (Automatic Repeat-reQuest) - y la posibilidad de emplear modulaciones de orden superior - 16QAM y 64QAM. Todas estas características serían inútiles sin unos buenos procedimientos de adaptación al enlace (link adaptation) que ajustaran los parámetros de transmisión a la calidad del enlace radio. El presente artículo aborda el estudio y optimización de los mecanismos de link adaptation en HSDPA aunque las técnicas propuestas pueden ser aplicadas a otros sistemas similares. Tras introducirse la temática del link adaptation se presenta el ‘estado del arte’ en la materia tanto en HSDPA como en otros sistemas celulares previos. En base a simulaciones realizadas a nivel de sistema se realiza un estudio pormenorizado de las prestaciones ofrecidas por el procedimiento más divulgado en la bibliografía, basado en el uso de indicadores de la calidad del canal. Para mejorar las prestaciones de los procedimientos comunes se proponen nuevas estrategias de procesado de los indicadores de calidad. Mediante simulación se ha demostrado la mejora obtenida con estas nuevas estrategias en lo referente a la maximización del throughtput de la transmisión.PALABRAS CLAVE: HSDPA, Adaptación al enlace, Indicadores de la calidad del canal   ABSTRACT HSDPA (High Speed Downlink Packet Access) technology is an evolved version of UMTS (Universal Mobile Telecommunications System) done by the 3GPP (3rd Generation Partnership Project) focused on the downlink capacity improvement. HSDPA enhancement is based on the efficient management of a shared channel performed by the Node-B - employing a packet scheduler -, the usage of advanced retransmission and combination mechanisms - hybrid ARQ (Automatic Repeat-reQuest) - and the availability of high order modulations - 16QAM and 64QAM -. All these characteristics would be worthless without good link adaptation procedures that adjust transmission parameters according to the radio link quality. This paper deals with the study and optimization of link adaptation mechanisms in HSDPA, although the proposed techniques could be easily extended to similar systems. Firstly, link adaptation is introduced and it is presented link adaptation ‘state of the art’ in HSDPA and other older cellular systems. Based on the results obtained with a system level HSDPA simulator, the performance of the link adaptation algorithm most common in the literature, which employs channel quality indicators, is assessed. In order to improve the performance of the common method, new channel quality indicator processing strategies have been proposed. Simulation results have shown non-negligible throughtput improvements with those new strategies. KEYWORDS: HSDPA, Link adaptation, Channel quality indicato