5G Radio Access Networks Enabling Efficient Point-to-Multipoint Transmissions

© 2019 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] The first release of 5th Generation (5G) technology from 3rd Generation Project Partnership (3GPP) Rel'15 has been completed in December 2018. An open issue with this release of standards is that it only supports unicast communications in the core network and Point-To-Point (PTP) transmissions in the Radio Access Network (RAN), and does not support multicast/broadcast communications and Point-To-Multipoint (PTM) transmissions, which are 3GPP system requirements for 5G applications in a number of vertical sectors, such as Automotive, Airborne Communications, Internet-of-Things, Media & Entertainment, and Public Warning & Safety systems. In this article, we present novel mechanisms for enhancing the 5G unicast architecture with minimal footprint, to enable efficient PTM transmissions in the RAN, and to support multicast communications in the Rel'15 core as an in-built delivery optimization feature of the system. This approach will enable completely new levels of network management and delivery cost-efficiency.This work was supported in part by the European Commission under the 5G Infrastructure Public Private Partnership project "5G-Xcast: Broadcast and Multicast Communication Enablers for the Fifth Generation of Wireless Systems" (H2020-ICT-2016-2 call, grant 761498). The views expressed here are those of the authors and do not necessarily represent the project.Säily, M.; Barjau, C.; Navrátil, D.; Prasad, A.; Gomez-Barquero, D.; Tesema, FB. (2019). 5G Radio Access Networks Enabling Efficient Point-to-Multipoint Transmissions. IEEE Vehicular Technology Magazine. 14(4):29-37. https://doi.org/10.1109/MVT.2019.2936657S293714

Language ideologies in the female Brazilian diaspora in Serbia: interdisciplinary perspective ; Языковые идеологии в женской бразильской диаспоре в Сербии: междисциплинарная перспектива

Predmet ovog rada su jezičke ideologije pripadnica brazilske dijaspore u Srbiji, izvornih govornica portugalskog jezika, koje su u braku ili vanbračnoj zajednici sa Srbima, izvornim govornicima srpskog jezika. Jezičke ideologije su raširene u svim društvima, u kojima utiču na jezičko ponašanje govornika i govornica, reprodukuju se, prenose se, održavaju se i menjaju, često sasvim implicitno, ali i eksplicitno, kroz iznošenje stavova prema jeziku. Zato je proučavanje stavova prema jeziku jedan od najboljih načina da se identifikuju jezičke ideologije koje preovladavaju u određenoj govornoj zajednici. U ovom istraživanju polazimo od te međupovezanosti stavova prema jeziku i jezičkih ideologija i analiziramo stavove ispitanica prema manjinskom i većinskom jeziku, kao i prema nekim drugim jezičkim varijetetima i sa njima povezanim pojmovima...This paper focuses on the linguistic ideologies of female members of the Brazilian diaspora in Serbia, native speakers of the Portuguese language, who are married to or in a domestic partnership with Serbs, native speakers of the Serbian language. Language ideologies are widespread in every society, affecting the linguistic behaviour of speakers, being reproduced, transmitted, maintained, and changed, often quite implicitly, as well as explicitly, by expressing attitudes toward language. That is why studying attitudes towards language is one of the best ways to identify linguistic ideologies that are dominant in a specific speech community. This study starts off with this interconnectedness of attitudes towards language and language ideologies and analyzes the attitudes of respondents towards the minority and majority languages, as well as towards a few other language varieties and terms related to these..

Network-driven handover in 5G

Currently, users’ expectations regarding technological performance are constantly increasing. An example of this is the growing consumption of multimedia content via the Internet. Multimedia applications with a variable number of users/requests have variable demand over time that may expose the limitation of the network channels. This may cause a problem of demand mobility generated by the service/application. Each generation of mobile networks has specific handover processes, which in the case of 4G can be controlled according to the applications requirements, with the possibility of multiconnectivity. This process was massified in 5G. The main contribution of this dissertation is the development and analysis of decision models for controlling the video streaming and user association to a BS in the network architecture. The scenario considered refers to a football stadium with multiple points of view – video streams – that each spectator can request to view on their cell phone or tablet. The developed simulator models the stadium scenario using a combination of services, which occur on the 5G network. Vertical handover generated by the network is used,aidedbynetworkslicing. Thenetworkslicingactsinthepartofthebandwidthdivision between the different antennas and allows the throughput of the different broadcast (FeMBMS)channelsto becontrolledbytheservice -theradionetworkcapacitylimitsthe throughput. The results obtained in a case of 80000 spectators who select different beams over time, considering8basestations(BS),showthatthequalityofexperienceishighonlywhenthe handover and the control of beam diffusion by BS are managed according to the application requirements. The network recovers from huge peaks by handling as many requests at once as possible. Instead of the user only getting the steam in a good quality or not getting it at all, the network performs a best-effort solution of downgrading the quality of multicasting in order to expend less resources with the same quantity of requests. The network state is taken into consideration. Although there are load peaks on the network, it is never congested.Atualmente, as expectativas dos utilizadores em relação à capacidade tecnológica não param de aumentar. Exemplo disso é o crescente consumo de conteúdo multimédia através da Internet. Aplicações multimédia com número variável de utilizadores e pedidos têm um fluxo de serviço variável ao longo do tempo. Esta variância pode expor a limitação de canais de rede, que consequentemente pode causar um problema de mobilidade gerado pelo serviço/aplicação. Cada geração de redes móveis possui processos de handover de utilizadores específicos, que no caso da geração 4G passou a ser controlado em função das aplicações, com a possibilidade de multiconectividade. Este processo foi massificado no 5G. A principal contribuição desta dissertação é o desenvolvimento e análise de modelos de decisão para controlar a difusão de vídeo e a associação de utilizadores à rede rádio na arquitetura da rede. O cenário considerado reflete um estádio de futebol com vários pontos de vista - diferentes feixes de vídeo - que cada espectador pode solicitar e visualizar no seu telemóvel ou tablet. O simulador desenvolvido modela o cenário do estádio usando uma combinação de serviços, que ocorrem na rede 5G. É usado handover vertical gerado pela rede auxiliado por network slicing que atua na parte da divisão da largura de banda entre as diferentes antenas e permite que a taxa de débito dos diferentes canais de difusão (FeMBMS) seja controlada pelo serviço - a capacidade da rede rádio limita a taxa de transferência. Os resultados obtidos no caso de 80000 espectadores que selecionam diferentes feixes ao longo do tempo, considerando 8 estações base (BS), mostram que a qualidade de experiência somente é elevada quando o handover e o controlo da difusão de feixes pelas BS são geridos de acordo com os requisitos da aplicação. A rede recupera a estabilidade após enormes picos de transferência gerindo os seus recursos. Em vez do utilizador ser prejudicado na totalidade quando a rede não tem recursos e ser privado de obter serviço, é utilizado um processo alternativo em que a rede diminui a qualidade de multicasting, gastando menos recursos com a mesma quantidade de pedidos. O estado da rede é sempre tido em consideração - embora hajam picos de carga na rede, esta nunca fica congestionada

Measurement-Driven Algorithm and System Design for Wireless and Datacenter Networks

The growing number of mobile devices and data-intensive applications pose unique challenges for wireless access networks as well as datacenter networks that enable modern cloud-based services. With the enormous increase in volume and complexity of traffic from applications such as video streaming and cloud computing, the interconnection networks have become a major performance bottleneck. In this thesis, we study algorithms and architectures spanning several layers of the networking protocol stack that enable and accelerate novel applications and that are easily deployable and scalable. The design of these algorithms and architectures is motivated by measurements and observations in real world or experimental testbeds. In the first part of this thesis, we address the challenge of wireless content delivery in crowded areas. We present the AMuSe system, whose objective is to enable scalable and adaptive WiFi multicast. AMuSe is based on accurate receiver feedback and incurs a small control overhead. This feedback information can be used by the multicast sender to optimize multicast service quality, e.g., by dynamically adjusting transmission bitrate. Specifically, we develop an algorithm for dynamic selection of a subset of the multicast receivers as feedback nodes which periodically send information about the channel quality to the multicast sender. Further, we describe the Multicast Dynamic Rate Adaptation (MuDRA) algorithm that utilizes AMuSe's feedback to optimally tune the physical layer multicast rate. MuDRA balances fast adaptation to channel conditions and stability, which is essential for multimedia applications. We implemented the AMuSe system on the ORBIT testbed and evaluated its performance in large groups with approximately 200 WiFi nodes. Our extensive experiments demonstrate that AMuSe can provide accurate feedback in a dense multicast environment. It outperforms several alternatives even in the case of external interference and changing network conditions. Further, our experimental evaluation of MuDRA on the ORBIT testbed shows that MuDRA outperforms other schemes and supports high throughput multicast flows to hundreds of nodes while meeting quality requirements. As an example application, MuDRA can support multiple high quality video streams, where 90% of the nodes report excellent or very good video quality. Next, we specifically focus on ensuring high Quality of Experience (QoE) for video streaming over WiFi multicast. We formulate the problem of joint adaptation of multicast transmission rate and video rate for ensuring high video QoE as a utility maximization problem and propose an online control algorithm called DYVR which is based on Lyapunov optimization techniques. We evaluated the performance of DYVR through analysis, simulations, and experiments using a testbed composed of Android devices and o the shelf APs. Our evaluation shows that DYVR can ensure high video rates while guaranteeing a low but acceptable number of segment losses, buffer underflows, and video rate switches. We leverage the lessons learnt from AMuSe for WiFi to address the performance issues with LTE evolved Multimedia Broadcast/Multicast Service (eMBMS). We present the Dynamic Monitoring (DyMo) system which provides low-overhead and real-time feedback about eMBMS performance. DyMo employs eMBMS for broadcasting instructions which indicate the reporting rates as a function of the observed Quality of Service (QoS) for each UE. This simple feedback mechanism collects very limited QoS reports which can be used for network optimization. We evaluated the performance of DyMo analytically and via simulations. DyMo infers the optimal eMBMS settings with extremely low overhead, while meeting strict QoS requirements under different UE mobility patterns and presence of network component failures. In the second part of the thesis, we study datacenter networks which are key enablers of the end-user applications such as video streaming and storage. Datacenter applications such as distributed file systems, one-to-many virtual machine migrations, and large-scale data processing involve bulk multicast flows. We propose a hardware and software system for enabling physical layer optical multicast in datacenter networks using passive optical splitters. We built a prototype and developed a simulation environment to evaluate the performance of the system for bulk multicasting. Our evaluation shows that the optical multicast architecture can achieve higher throughput and lower latency than IP multicast and peer-to-peer multicast schemes with lower switching energy consumption. Finally, we study the problem of congestion control in datacenter networks. Quantized Congestion Control (QCN), a switch-supported standard, utilizes direct multi-bit feedback from the network for hardware rate limiting. Although QCN has been shown to be fast-reacting and effective, being a Layer-2 technology limits its adoption in IP-routed Layer 3 datacenters. We address several design challenges to overcome QCN feedback's Layer- 2 limitation and use it to design window-based congestion control (QCN-CC) and load balancing (QCN-LB) schemes. Our extensive simulations, based on real world workloads, demonstrate the advantages of explicit, multi-bit congestion feedback, especially in a typical environment where intra-datacenter traffic with short Round Trip Times (RTT: tens of s) run in conjunction with web-facing traffic with long RTTs (tens of milliseconds)

Learning for Network Applications and Control

The emergence of new Internet applications and technologies have resulted in an increased complexity as well as a need for lower latency, higher bandwidth, and increased reliability. This ultimately results in an increased complexity of network operation and management. Manual management is not sufficient to meet these new requirements. There is a need for data driven techniques to advance from manual management to autonomous management of network systems. One such technique, Machine Learning (ML), can use data to create models from hidden patterns in the data and make autonomous modifications. This approach has shown significant improvements in other domains (e.g., image recognition and natural language processing). The use of ML, along with advances in programmable control of Software- Defined Networks (SDNs), will alleviate manual network intervention and ultimately aid in autonomous network operations. However, realizing a data driven system that can not only understand what is happening in the network but also operate autonomously requires advances in the networking domain, as well as in ML algorithms. In this thesis, we focus on developing ML-based network architectures and data driven net- working algorithms whose objective is to improve the performance and management of future networks and network applications. We focus on problems spanning across the network protocol stack from the application layer to the physical layer. We design algorithms and architectures that are motivated by measurements and observations in real world or experimental testbeds. In Part I we focus on the challenge of monitoring and estimating user video quality of experience (QoE) of encrypted video traffic for network operators. We develop a system for REal-time QUality of experience metric detection for Encrypted Traffic, Requet. Requet uses a detection algorithm to identify video and audio chunks from the IP headers of encrypted traffic. Features extracted from the chunk statistics are used as input to a random forest ML model to predict QoE metrics. We evaluate Requet on a YouTube dataset we collected, consisting of diverse video assets delivered over various WiFi and LTE network conditions. We then extend Requet, and present a study on YouTube TV live streaming traffic behavior over WiFi and cellular networks covering a 9-month period. We observed pipelined chunk requests, a reduced buffer capacity, and a more stable chunk duration across various video resolutions compared to prior studies of on-demand streaming services. We develop a YouTube TV analysis tool using chunks statistics detected from the extracted data as input to a ML model to infer user QoE metrics. In Part II we consider allocating end-to-end resources in cellular networks. Future cellular networks will utilize SDN and Network Function Virtualization (NFV) to offer increased flexibility for network infrastructure operators to utilize network resources. Combining these technologies with real-time network load prediction will enable efficient use of network resources. Specifically, we leverage a type of recurrent neural network, Long Short-Term Memory (LSTM) neural networks, for (i) service specific traffic load prediction for network slicing, and (ii) Baseband Unit (BBU) pool traffic load prediction in a 5G cloud Radio Access Network (RAN). We show that leveraging a system with better accuracy to predict service requirements results in a reduction of operation costs. We focus on addressing the optical physical layer in Part III. Greater network flexibility through SDN and the growth of high bandwidth services are motivating faster service provisioning and capacity management in the optical layer. These functionalities require increased capacity along with rapid reconfiguration of network resources. Recent advances in optical hardware can enable a dramatic reduction in wavelength provisioning times in optical circuit switched networks. To support such operations, it is imperative to reconfigure the network without causing a drop in service quality to existing users. Therefore, we present a ML system that uses feedforward neural networks to predict the dynamic response of an optically circuit-switched 90-channel multi-hop Reconfigurable Optical Add-Drop Multiplexer (ROADM) network. We show that the trained deep neural network can recommend wavelength assignments for wavelength switching with minimal power excursions. We extend the performance of the ML system by implementing and testing a Hybrid Machine Learning (HML) model, which combines an analytical model with a neural network machine learning model to achieve higher prediction accuracy. In Part IV, we use a data-driven approach to address the challenge of wireless content delivery in crowded areas. We present the Adaptive Multicast Services (AMuSe) system, whose objective is to enable scalable and adaptive WiFi multicast. Specifically, we develop an algorithm for dynamic selection of a subset of the multicast receivers as feedback nodes. Further, we describe the Multicast Dynamic Rate Adaptation (MuDRA) algorithm that utilizes AMuSe’s feedback to optimally tune the physical layer multicast rate. Our experimental evaluation of MuDRA on the ORBIT testbed shows that MuDRA outperforms other schemes and supports high throughput multicast flows to hundreds of nodes while meeting quality requirements. We leverage the lessons learned from AMuSe for WiFi and use order statistics to address the performance issues with LTE evolved Multimedia Broadcast/Multicast Service (eMBMS). We present the Dynamic Monitoring (DyMo) system which provides low-overhead and real-time feedback about eMBMS performance to be used for network optimization. We focus on the Quality of Service (QoS) Evaluation module and develop a Two-step estimation algorithm which can efficiently identify the SNR Threshold as a one time estimation. DyMo significantly outperforms alternative schemes based on the Order-Statistics estimation method which relies on random or periodic sampling

Επισκόπηση των ενεργειών προτυποποίησης και των δυνατοτήτων του LTE-LTE Advanced-LTE Advanced Pro

Η παρούσα εργασία σκοπεύει στην παρουσίαση της τεχνολογίας του LTE, που αποτελεί τη βάση των δικτύων κινητής τηλεφωνίας 4G. Η παρουσίαση δεν επικεντρώνεται μόνο στα τεχνικά/λειτουργικά χαρακτηριστικά της τεχνολογίας, αλλά ασχολείται και με την ιστορική εξέλιξή τους, όπως αυτή αποτυπώνεται στα διάφορα releases. Πρόκειται για μία κατάδυση στα releases 8-14, δίνοντας βάρος στις ανάγκες που επιδιώχτηκε να καλυφθούν, στις προδιαγραφές που τέθηκαν, στις λύσεις που προτάθηκαν και στα ζητήματα που έμειναν για μελλοντική πρόβλεψη. Έπειτα από μία βασική εισαγωγή στην τεχνολογία του LTE όπως αυτή ορίστηκε στο πιστοποιητικό γέννησής της, το Release 8, η οποία και κάλυψε τα ζητήματα της αρχιτεκτονικής και των λύσεων φυσικού επιπέδου, επιλέχτηκε η παρουσίαση κάθε release ξεχωριστά, όπου και περιγράφονταν οι επιμέρους τεχνολογίες που είτε εισάγονταν είτε εμπλουτίζονταν με το release αυτό. Με αυτό τον τρόπο δίνεται μια σαφέστερη εικόνα της εξέλιξης, των νέων απαιτήσεων που προέκυπταν αλλά και της προοδευτικής λειτουργικής αναβάθμισης της τεχνολογίας αυτής. Για να επιτευχθεί ο σκοπός αυτός, η μελέτη των releases συνδυάστηκε με την εξέταση και άλλων πηγών, τόσο ακαδημαϊκών όσο και από τηλεπικοινωνιακούς κολοσσούς και ενώσεις, που στόχευαν αφενός στη συνοπτική παρουσίαση κάθε release και των τεχνολογιών του, αφετέρου τις συνέδεαν με το γενικότερο τηλεπικοινωνιακό πλαίσιο. Κατά τη μελέτη του υλικού, μας δόθηκε η ευκαιρία να διαπιστώσουμε την πλειάδα των τεχνολογιών που πρέπει να ενσωματώνει ένα σύγχρονο τηλεπικοινωνιακό σύστημα και των διαφορετικών λειτουργιών που πρέπει να επιτελεί. Επίσης, συνειδητοποιήσαμε πως το LTE είναι στραμμένο στο μέλλον: ενώ η τεχνολογία 4G δε βρίσκεται καν στο μέγιστο της ακμής της, το 5G είναι ήδη στα σκαριά, με ορίζοντα το 2020.The present assignment aims at presenting the technology of LTE, the core of the 4G cellular networks. The presentation does not focus on the technical and functional details of LTE only, but deals with their evolution over time as well, as this is illustrated in the various releases. Actually, it is a dive into releases 8 to 14, focusing on the needs behind them, the specifications, the requirements, the proposed solutions and the issues left for future releases. After a brief introduction in the LTE technology, as this has been defined in Release 8, which covers the physical layer and architecture aspects of the technology, the presentation of each of the following releases separately at a chronological order was adopted, where the technologies related to each release were presented. In that way, a clear review of the evolution described by each release is shown, including the new requirements arised and the step-by-step enhancement of LTE. For that reason, the study of releases was combined with the reviewing of other sources, both academic and commercial, in order to achieve a better level of presentation of each release and a connection to the market. While examining the material, we had the opportunity to understand the vast number of underlying technologies of each modern telecommunications system and of the diversity of functions this has to implement. Moreover, we took into consideration that LTE’s community is always future-oriented: while 4G is still in growth, the technology of 5G is to be standardized

On reliable and energy efficient massive wireless communications: the road to 5G

La quinta generación de redes móviles (5G) se encuentra a la vuelta de la esquina. Se espera provea de beneficios extraordinarios a la población y que resuelva la mayoría de los problemas de las redes 4G actuales. El éxito de 5G, cuya primera fase de estandarización ha sido completada, depende de tres pilares: comunicaciones tipo-máquina masivas, banda ancha móvil mejorada y comunicaciones ultra fiables y de baja latencia (mMTC, eMBB y URLLC, respectivamente). En esta tesis nos enfocamos en el primer pilar de 5G, mMTC, pero también proveemos una solución para lograr eMBB en escenarios de distribución masiva de contenidos. Específicamente, las principales contribuciones son en las áreas de: 1) soporte eficiente de mMTC en redes celulares; 2) acceso aleatorio para el reporte de eventos en redes inalámbricas de sensores (WSNs); y 3) cooperación para la distribución masiva de contenidos en redes celulares. En el apartado de mMTC en redes celulares, esta tesis provee un análisis profundo del desempeño del procedimiento de acceso aleatorio, que es la forma mediante la cual los dispositivos móviles acceden a la red. Estos análisis fueron inicialmente llevados a cabo por simulaciones y, posteriormente, por medio de un modelo analítico. Ambos modelos fueron desarrollados específicamente para este propósito e incluyen uno de los esquemas de control de acceso más prometedores: access class barring (ACB). Nuestro modelo es uno de los más precisos que se pueden encontrar en la literatura y el único que incorpora el esquema de ACB. Los resultados obtenidos por medio de este modelo y por simulación son claros: los accesos altamente sincronizados que ocurren en aplicaciones de mMTC pueden causar congestión severa en el canal de acceso. Por otro lado, también son claros en que esta congestión se puede prevenir con una adecuada configuración del ACB. Sin embargo, los parámetros de configuración del ACB deben ser continuamente adaptados a la intensidad de accesos para poder obtener un desempeño óptimo. En la tesis se propone una solución práctica a este problema en la forma de un esquema de configuración automática para el ACB; lo llamamos ACBC. Los resultados muestran que nuestro esquema puede lograr un desempeño muy cercano al óptimo sin importar la intensidad de los accesos. Asimismo, puede ser directamente implementado en redes celulares para soportar el tráfico mMTC, ya que ha sido diseñado teniendo en cuenta los estándares del 3GPP. Además de los análisis descritos anteriormente para redes celulares, se realiza un análisis general para aplicaciones de contadores inteligentes. Es decir, estudiamos un escenario de mMTC desde la perspectiva de las WSNs. Específicamente, desarrollamos un modelo híbrido para el análisis de desempeño y la optimización de protocolos de WSNs de acceso aleatorio y basados en cluster. Los resultados muestran la utilidad de escuchar el medio inalámbrico para minimizar el número de transmisiones y también de modificar las probabilidades de transmisión después de una colisión. En lo que respecta a eMBB, nos enfocamos en un escenario de distribución masiva de contenidos, en el que un mismo contenido es enviado de forma simultánea a un gran número de usuarios móviles. Este escenario es problemático, ya que las estaciones base de la red celular no cuentan con mecanismos eficientes de multicast o broadcast. Por lo tanto, la solución que se adopta comúnmente es la de replicar e contenido para cada uno de los usuarios que lo soliciten; está claro que esto es altamente ineficiente. Para resolver este problema, proponemos el uso de esquemas de network coding y de arquitecturas cooperativas llamadas nubes móviles. En concreto, desarrollamos un protocolo para la distribución masiva de contenidos, junto con un modelo analítico para su optimización. Los resultados demuestran que el modelo propuesto es simple y preciso, y que el protocolo puede reducir el conLa cinquena generació de xarxes mòbils (5G) es troba molt a la vora. S'espera que proveïsca de beneficis extraordinaris a la població i que resolga la majoria dels problemes de les xarxes 4G actuals. L'èxit de 5G, per a la qual ja ha sigut completada la primera fase del qual d'estandardització, depén de tres pilars: comunicacions tipus-màquina massives, banda ampla mòbil millorada, i comunicacions ultra fiables i de baixa latència (mMTC, eMBB i URLLC, respectivament, per les seues sigles en anglés). En aquesta tesi ens enfoquem en el primer pilar de 5G, mMTC, però també proveïm una solució per a aconseguir eMBB en escenaris de distribució massiva de continguts. Específicament, les principals contribucions són en les àrees de: 1) suport eficient de mMTC en xarxes cel·lulars; 2) accés aleatori per al report d'esdeveniments en xarxes sense fils de sensors (WSNs); i 3) cooperació per a la distribució massiva de continguts en xarxes cel·lulars. En l'apartat de mMTC en xarxes cel·lulars, aquesta tesi realitza una anàlisi profunda de l'acompliment del procediment d'accés aleatori, que és la forma mitjançant la qual els dispositius mòbils accedeixen a la xarxa. Aquestes anàlisis van ser inicialment dutes per mitjà de simulacions i, posteriorment, per mitjà d'un model analític. Els models van ser desenvolupats específicament per a aquest propòsit i inclouen un dels esquemes de control d'accés més prometedors: el access class barring (ACB). El nostre model és un dels més precisos que es poden trobar i l'únic que incorpora l'esquema d'ACB. Els resultats obtinguts per mitjà d'aquest model i per simulació són clars: els accessos altament sincronitzats que ocorren en aplicacions de mMTC poden causar congestió severa en el canal d'accés. D'altra banda, també són clars en què aquesta congestió es pot previndre amb una adequada configuració de l'ACB. No obstant això, els paràmetres de configuració de l'ACB han de ser contínuament adaptats a la intensitat d'accessos per a poder obtindre unes prestacions òptimes. En la tesi es proposa una solució pràctica a aquest problema en la forma d'un esquema de configuració automàtica per a l'ACB; l'anomenem ACBC. Els resultats mostren que el nostre esquema pot aconseguir un acompliment molt proper a l'òptim sense importar la intensitat dels accessos. Així mateix, pot ser directament implementat en xarxes cel·lulars per a suportar el trànsit mMTC, ja que ha sigut dissenyat tenint en compte els estàndards del 3GPP. A més de les anàlisis descrites anteriorment per a xarxes cel·lulars, es realitza una anàlisi general per a aplicacions de comptadors intel·ligents. És a dir, estudiem un escenari de mMTC des de la perspectiva de les WSNs. Específicament, desenvolupem un model híbrid per a l'anàlisi de prestacions i l'optimització de protocols de WSNs d'accés aleatori i basats en clúster. Els resultats mostren la utilitat d'escoltar el mitjà sense fil per a minimitzar el nombre de transmissions i també de modificar les probabilitats de transmissió després d'una col·lisió. Pel que fa a eMBB, ens enfoquem en un escenari de distribució massiva de continguts, en el qual un mateix contingut és enviat de forma simultània a un gran nombre d'usuaris mòbils. Aquest escenari és problemàtic, ja que les estacions base de la xarxa cel·lular no compten amb mecanismes eficients de multicast o broadcast. Per tant, la solució que s'adopta comunament és la de replicar el contingut per a cadascun dels usuaris que ho sol·liciten; és clar que això és altament ineficient. Per a resoldre aquest problema, proposem l'ús d'esquemes de network coding i d'arquitectures cooperatives anomenades núvols mòbils. En concret, desenvolupem un protocol per a realitzar la distribució massiva de continguts de forma eficient, juntament amb un model analític per a la seua optimització. Els resultats demostren que el model proposat és simple i precísThe 5th generation (5G) of mobile networks is just around the corner. It is expected to bring extraordinary benefits to the population and to solve the majority of the problems of current 4th generation (4G) systems. The success of 5G, whose first phase of standardization has concluded, relies in three pillars that correspond to its main use cases: massive machine-type communication (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communication (URLLC). This thesis mainly focuses on the first pillar of 5G: mMTC, but also provides a solution for the eMBB in massive content delivery scenarios. Specifically, its main contributions are in the areas of: 1) efficient support of mMTC in cellular networks; 2) random access (RA) event-reporting in wireless sensor networks (WSNs); and 3) cooperative massive content delivery in cellular networks. Regarding mMTC in cellular networks, this thesis provides a thorough performance analysis of the RA procedure (RAP), used by the mobile devices to switch from idle to connected mode. These analyses were first conducted by simulation and then by an analytical model; both of these were developed with this specific purpose and include one of the most promising access control schemes: the access class barring (ACB). To the best of our knowledge, this is one of the most accurate analytical models reported in the literature and the only one that incorporates the ACB scheme. Our results clearly show that the highly-synchronized accesses that occur in mMTC applications can lead to severe congestion. On the other hand, it is also clear that congestion can be prevented with an adequate configuration of the ACB scheme. However, the configuration parameters of the ACB scheme must be continuously adapted to the intensity of access attempts if an optimal performance is to be obtained. We developed a practical solution to this problem in the form of a scheme to automatically configure the ACB; we call it access class barring configuration (ACBC) scheme. The results show that our ACBC scheme leads to a near-optimal performance regardless of the intensity of access attempts. Furthermore, it can be directly implemented in 3rd Generation Partnership Project (3GPP) cellular systems to efficiently handle mMTC because it has been designed to comply with the 3GPP standards. In addition to the analyses described above for cellular networks, a general analysis for smart metering applications is performed. That is, we study an mMTC scenario from the perspective of event detection and reporting WSNs. Specifically, we provide a hybrid model for the performance analysis and optimization of cluster-based RA WSN protocols. Results showcase the utility of overhearing to minimize the number of packet transmissions, but also of the adaptation of transmission parameters after a collision occurs. Building on this, we are able to provide some guidelines that can drastically increase the performance of a wide range of RA protocols and systems in event reporting applications. Regarding eMBB, we focus on a massive content delivery scenario in which the exact same content is transmitted to a large number of mobile users simultaneously. Such a scenario may arise, for example, with video streaming services that offer a particularly popular content. This is a problematic scenario because cellular base stations have no efficient multicast or broadcast mechanisms. Hence, the traditional solution is to replicate the content for each requesting user, which is highly inefficient. To solve this problem, we propose the use of network coding (NC) schemes in combination with cooperative architectures named mobile clouds (MCs). Specifically, we develop a protocol for efficient massive content delivery, along with the analytical model for its optimization. Results show the proposed model is simple and accurate, and the protocol can lead to energy savings of up to 37 percent when compared to the traditional approach.Leyva Mayorga, I. (2018). On reliable and energy efficient massive wireless communications: the road to 5G [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/115484TESI

Potentzia domeinuko NOMA 5G sareetarako eta haratago

Tesis inglés 268 p. -- Tesis euskera 274 p.During the last decade, the amount of data carried over wireless networks has grown exponentially. Several reasons have led to this situation, but the most influential ones are the massive deployment of devices connected to the network and the constant evolution in the services offered. In this context, 5G targets the correct implementation of every application integrated into the use cases. Nevertheless, the biggest challenge to make ITU-R defined cases (eMBB, URLLC and mMTC) a reality is the improvement in spectral efficiency. Therefore, in this thesis, a combination of two mechanisms is proposed to improve spectral efficiency: Non-Orthogonal Multiple Access (NOMA) techniques and Radio Resource Management (RRM) schemes. Specifically, NOMA transmits simultaneously several layered data flows so that the whole bandwidth is used throughout the entire time to deliver more than one service simultaneously. Then, RRM schemes provide efficient management and distribution of radio resources among network users. Although NOMA techniques and RRM schemes can be very advantageous in all use cases, this thesis focuses on making contributions in eMBB and URLLC environments and proposing solutions to communications that are expected to be relevant in 6G

Applications of 5G Communications in Civil Protection

Τα δίκτυα πέμπτης γενιάς θεωρούνται ευρέως ως μία από τις πιο θεμελιώδεις τεχνολογικές εξελίξεις του τρέχοντος αιώνα, προσφέροντας υψηλή ταχύτητα, χαμηλή καθυστέρηση και κλιμάκωση. Τα επόμενα χρόνια, τα δίκτυα πέμπτης γενιάς αναμένεται να δημιουργήσουν τη χωρητικότητα, την απόδοση και την ευελιξία του ασύρματου δικτύου για να υποστηρίξουν μια εκρηκτική αύξηση στις συνδεδεμένες συσκευές, μαζί με πρωτοποριακές εφαρμογές. Αυτή η καινοτόμος νέα τεχνολογία μπορεί να βελτιώσει όλο το φάσμα της καθημερινής ζωής από την υγεία στην ψυχαγωγία και από τη γεωργία στην πολιτική προστασία. Οι κρίσιμες επικοινωνίες, ο ακρογωνιαίος λίθος της Πολιτικής Προστασίας, θα επωφεληθούν σε μεγάλο βαθμό από το 5G. Η παρούσα εργασία μελετά πώς νέα στοιχεία και τεχνολογίες του 5G όπως η επαυξημένη πραγματικότητα, η ηλεκτρονική υγεία και η βελτιστοποιημένη δρομολόγηση ασθενοφόρων μπορούν να υποστηρίξουν την Πολιτική Προστασία ενισχύοντας παράλληλα το περιβάλλον και την οικονομία.5G networks are widely considered as one of the most fundamental technology developments of our century, providing ultra-high-speed, low-latency and scalability. Over the coming years, 5G is expected to create the wireless network capacity, performance and flexibility to support an explosive increase in connected devices, along with exciting new use cases. This innovative technology can improve the whole spectrum of everyday life from health to entertainment and from agriculture to civil protection. Mission critical Communications, the cornerstone of civil protection, are to be greatly impacted by 5G. This thesis studies how new 5G components and technologies such as augmented reality, ehealth and optimized routing of ambulances are able to support the role of civil protection while enhancing the protection of the environment and the economy