Quantifying Potential Energy Efficiency Gain in Green Cellular Wireless Networks

Conventional cellular wireless networks were designed with the purpose of providing high throughput for the user and high capacity for the service provider, without any provisions of energy efficiency. As a result, these networks have an enormous Carbon footprint. In this paper, we describe the sources of the inefficiencies in such networks. First we present results of the studies on how much Carbon footprint such networks generate. We also discuss how much more mobile traffic is expected to increase so that this Carbon footprint will even increase tremendously more. We then discuss specific sources of inefficiency and potential sources of improvement at the physical layer as well as at higher layers of the communication protocol hierarchy. In particular, considering that most of the energy inefficiency in cellular wireless networks is at the base stations, we discuss multi-tier networks and point to the potential of exploiting mobility patterns in order to use base station energy judiciously. We then investigate potential methods to reduce this inefficiency and quantify their individual contributions. By a consideration of the combination of all potential gains, we conclude that an improvement in energy consumption in cellular wireless networks by two orders of magnitude, or even more, is possible.Comment: arXiv admin note: text overlap with arXiv:1210.843

System optimisation and radio planning for future LTE-advanced

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThis work is related to wireless communication. In this Thesis three main issues are addressed for future cellular networks: power consumption, interference and mobility. These issues continue to be a burden on the system’s performance as long as technology keeps evolving. In the presented chapters, the focus was to introduce greater intelligence to the LTE system algorithms and bring to them a dynamic and self-organizing approach. The first approach concerns power consumption in wireless terminals. The currently applied solution to save energy is the DRX mechanism. It organizes the time when the terminal wakes up and starts receiving data, and when it goes into sleep mode in order to save its battery power. The current DRX is described as static or fixed which makes its parameters unsuitable for the nature of the bursty traffic. In this work an adaptive DRX mechanism is proposed and evaluated as the wireless terminal battery saving algorithm. The second approach is co-channel interference mitigation. To increase the system’s capacity and avoid spectrum scarcity, small cells such as Femtocells are deployed and operate on the same frequency bands as the Macrocell. Although these small nodes increase the system capacity, however, the challenges will be in the femtocells planning and management in addition to the interference issues. Here a dynamic interference cancellation approach is presented to enable the Femtocell to track the allocated resources to the Macro-users, and to avoid using them. The third approach concerns mobility management in heterogeneous networks. The wireless terminal may have different mobility levels during handover which increases the handover failures due to failure in handover commands and aging of the reported parameters. This issue is presented in detail with the aim to avoid performance degradation and improve the reporting mechanisms during fast mobility levels. For this regard the presented method proposes more cooperation between the serving cell and the end-user so that the large amount of overhead and measurement are reduced. Simulations with different configurations are conducted to present the results of the proposed models. Results show that the proposed models bring improvements to the LTE system. The enhanced self-organized architecture in the three presented approaches performs well in terms of power saving, dynamic spectrum utilization by Femtocells, and mitigation of sudden throughput degradation due to the serving cell’s downlink signal outage during mobility.Brunel University Londo

Energy Efficiency in Communications and Networks

The topic of "Energy Efficiency in Communications and Networks" attracts growing attention due to economical and environmental reasons. The amount of power consumed by information and communication technologies (ICT) is rapidly increasing, as well as the energy bill of service providers. According to a number of studies, ICT alone is responsible for a percentage which varies from 2% to 10% of the world power consumption. Thus, driving rising cost and sustainability concerns about the energy footprint of the IT infrastructure. Energy-efficiency is an aspect that until recently was only considered for battery driven devices. Today we see energy-efficiency becoming a pervasive issue that will need to be considered in all technology areas from device technology to systems management. This book is seeking to provide a compilation of novel research contributions on hardware design, architectures, protocols and algorithms that will improve the energy efficiency of communication devices and networks and lead to a more energy proportional technology infrastructure

THROUGHPUT OPTIMIZATION AND ENERGY EFFICIENCY OF THE DOWNLINK IN THE LTE SYSTEM

Nowadays, the usage of smart phones is very popular. More and more people access the Internet with their smart phones. This demands higher data rates from the mobile network operators. Every year the number of users and the amount of information is increasing dramatically. The wireless technology should ensure high data rates to be able to compete with the wire-based technology. The main advantage of the wireless system is the ability for user to be mobile. The 4G LTE system made it possible to gain very high peak data rates. The purpose of this thesis was to investigate the improvement of the system performance for the downlink based on different antenna configurations and different scheduling algorithms. Moreover, the fairness between the users using different schedulers has been analyzed and evaluated. Furthermore, the energy efficiency of the scheduling algorithms in the downlink of LTE systems has been considered. Some important parts of the LTE system are described in the theoretical part of this thesis.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Energy Management in LTE Networks

Wireless cellular networks have seen dramatic growth in number of mobile users. As a result, data requirements, and hence the base-station power consumption has increased significantly. It in turn adds to the operational expenditures and also causes global warming. The base station power consumption in long-term evolution (LTE) has, therefore, become a major challenge for vendors to stay green and profitable in competitive cellular industry. It necessitates novel methods to devise energy efficient communication in LTE. Importance of the topic has attracted huge research interests worldwide. Energy saving (ES) approaches proposed in the literature can be broadly classified in categories of energy efficient resource allocation, load balancing, carrier aggregation, and bandwidth expansion. Each of these methods has its own pros and cons leading to a tradeoff between ES and other performance metrics resulting into open research questions. This paper discusses various ES techniques for the LTE systems and critically analyses their usability through a comprehensive comparative study

Monitoring and testing in LTE networks: from experimental analysis to operational optimisation

L'avvento di LTE e LTE-Adavanced, e la loro integrazione con le esistenti tecnologie cellulari, GSM e UMTS, ha costretto gli operatori di rete radiomobile ad eseguire una meticolosa campagna di test e a dotarsi del giusto know-how per rilevare potenziali problemi durante il dispiegamento di nuovi servizi. In questo nuovo scenario di rete, la caratterizzazione e il monitoraggio del traffico nonchè la configurazione e l'affidibilità degli apparati di rete, sono di importanza fondamentale al fine di prevenire possibili insidie durante la distribuzione di nuovi servizi e garantire la migliore esperienza utente possibile. Sulla base di queste osservazioni, questa tesi di dottorato offre un percorso completo di studio che va da un'analisi sperimentale ad un'ottimizzazione operativa. Il punto di partenza del nostro lavoro è stato il monitoraggio del traffico di un eNodeB di campo con tre celle, operativo nella banda 1800 MHz. Tramite campagne di misura successive, è stato possibile seguire l'evoluzione della rete 4G dagli albori del suo dispiegamento nel 2012, fino alla sua completa maturazione nel 2015. I dati raccolti durante il primo anno, evidenziavano uno scarso utilizzo della rete LTE, dovuto essenzialmente alla limitata penetrazione dei nuovi smartphone 4G. Nel 2015, invece, abbiamo assistito ad un aumento netto e decisivo del numero di utenti che utilizzano la tecnolgia LTE, con statistiche aggregate (come gli indici di marketshare per i sistemi operativi degli smartphones, o la percentuale di traffico video) che rispecchiano i trend nazionali e internazionali. Questo importante risultato testimonia la maturità della tecnologia LTE, e ci permette di considerare il nostro eNodeB un punto di osservazione prezioso per l'analisi del traffico. Di pari passo con l'evoluzione dell'infrastruttura, anche i telefoni cellulari hanno avuto una sorprendente evoluzione nel corso degli ultimi due decenni, a partire da dispositivi semplici con servizi di sola voce, fino agli smartphone di ultima generazione che offrono servizi innovativi, come Internet mobile, geolocalizzazione e mappe, servizi multimediali, e molti altri. Monitorare il traffico reale ci ha quindi permesso di studiare il comportamento degli utenti e individuare i servizi maggiormente utilizzati. Per questo, sono state sviluppate diverse librerie software per l'analisi del traffico. In particolare, è stato sviluppato in C++14 un framework/tool per la classificazione del traffico. Il progetto, disponibile su github, si chiama MOSEC, un acronimo per MOdular SErvice Classifier. MOSEC consente di definire e utilizzare un numero arbitrario di plug-in, che processano il pacchetto secondo le loro logiche e possono o no ritornare un valore di classificazione. Una strategia di decisione finale consente di classificare i vari flussi, basandosi sulle classificazioni di ciascun plug-in. Abbiamo quindi validato la bontà del processi di classificazione di MOSEC utilizzando una traccia labellata come ground-truth di classificazione. I risultati mostrano una eccellente capacità di classificazione di traffico TCP-HTTP/HTTPS, mediamente superiore a quella di altri tool di classificazione (nDPI, PACE, Layer-7), ed evidenzia alcune lacune per quanto riguarda la classificazione di traffico UDP. Le carattistiche dei flussi di traffico utente (User Plane) hanno un impatto diretto sul consumo energetico dei terminali e indiretto sul traffico di controllo (Control Plane) che viene generato. Pertanto, la conoscenza delle proprietà statistiche dei vari flussi consente di affrontare un problema del cross-layer optimization, per ridurre il consumo energetico dei terminali variando dei parametri configurabili sugli eNodeB. E' noto che la durata della batteria dei nuovi smartphone, rappresenta uno dei maggiori limiti nell'utilizzo degli stessi. In particolare, lo sviluppo di nuovi servizi e applicazioni capaci di lavorare in background, senza la diretta interazione dell’utente, ha introdotto nuovi problemi riguardanti la durata delle batterie degli smartphone e il traffico di segnalazione necessario ad acquisire/rilasciare le risorse radio. In conformità a queste osservazioni, è stato condotto uno studio approfondito sul meccanismo DRX (Discontinuous Reception), usato in LTE per consentire all’utente di risparmiare energia quando nessun pacchetto è inviato o ricevuto. I parametri DRX e RRC Inactivity Timer influenzano notevolmente l’energia consumata dai vari device. A seconda che le risorse radio siano assegnate o meno, l’UE si trova rispettivamente negli stati di RRC Connected e RRC Idle. Per valutare il consumo energetico degli smartphone, è stato sviluppato un algoritmo che associa un valore di potenza a ciascuno degli stati in cui l’UE può trovarsi. La transizione da uno stato all’altro è regolata da diversi timeout che sono resettati ogni volta che un pacchetto è inviato o ricevuto. Utilizzando le tracce di traffico reale, è stata associata una macchina a stati a ogni UE per valutare il consumo energetico sulla base dei pacchetti inviati e ricevuti. Osservando le caratteristiche statistiche del traffico User Plane è stata ripetuta la simulazione utilizzando dei valori dell’Inactivity Timer diversi da quello impiegato negli eNodeB di rete reale, alla ricerca di un buon trade-off tra risparmio energetico e aumento del traffico di segnalazione. I risultati hanno permesso di determinare che l'Inactivity Timer, settato originariamente sull'eNodeB era troppo elevato e determinava un consumo energetico eccesivo sui terminali. Diminuendone il valore fino a 10 secondi, si può ottenere un risparmio energetico fino al 50\% (a secondo del traffico generato) senza aumentare considerevolemente il traffico di controllo. I risultati dello studio di cui sopra, tuttavia, non tengono in considerazione lo stato di stress cui può essere sottoposto un eNodeB per effetto dell'aumento del traffico di segnalazione, nè, tantomeno, dell'aumento della contesa di accesso alla rete durante la procedura di RACH, necessaria per ristabilire il bearer radio (o connessione RRC) tra terminale ed eNodeB. Valutare le performance di sistemi hardware e software per la rete mobile di quarta generazione, cosi come individuare qualsiasi possibile debolezza all’interno dell’architettura, è un lavoro complesso. Un possibile caso di studio, è proprio quello di valutare la robustezza delle Base Station quando riceve molte richieste di connessioni RRC, per effetto di una diminuzione dell'Inactivity Timer. A tal proposito, all’interno del Testing LAB di Telecom Italia, abbiamo utilizzato IxLoad, un prodotto sviluppato da Ixia, come generatore di carico per testare la robustezza di un eNodeB. I test sono consistiti nel produrre un differente carico di richieste RRC sull'interfaccia radio, similmente a quelle che si avrebbero diminuendo l'Inactivity Timer. Le proprietà statistiche del traffico di controllo sono ricavate a partire dall'analisi dalle tracce di traffico reale. I risultati hanno dimostrato che, anche a fronte di un carico sostenuto di richieste RRC solo una minima parte (percentuale inferiore all'1\% nel caso più sfavorevole) di procedure fallisce. Abbassare l'inactivity timer anche a valori inferiori ai 10 secondi non è quindi un problema per la Base Station. Rimane da valutare, infine, cosa succede a seguito dell'aumento delle richieste di accesso al canale RACH, dal punto di vista degli utenti. Quando due o più utenti tentano, simultaneamente, di accedere al canale RACH, utilizzando lo stesso preambolo, l’eNodeB potrebbe non essere in grado di decifrare il preambolo. Se i due segnali interferiscono costruttivamente, entrambi gli utenti riceveranno le stesse risorse per trasmettere il messaggio di RRC Request e, a questo punto, l’eNodeB può individuare la collisione e non trasmetterà nessun acknowledgement, forzando entrambi gli utenti a ricominciare la procedura dall’inizio. Abbiamo quindi proposto un modello analitico per calcolare la probabilità di collisione in funzione del numero di utenti e del carico di traffico offerto, quando i tempi d’interarrivo tra richieste successive é modellata con tempi iper-esponenziali. In più, abbiamo investigato le prestazioni di comunicazioni di tipo Machine-to-Machine (M2M) e Human-to-Human (H2H), valutando, al variare del numero di preamboli utilizzati, la probabilità di collisione su canale RACH, la probabilità di corretta trasmissione considerando sia il tempo di backoff che il numero massimo di ritrasmissioni consentite, e il tempo medio necessario per stabilire un canale radio con la rete di accesso. I risultati, valutati nel loro insieme, hanno consentito di esprimere delle linee guida per ripartire opportunamente il numero di preamboli tra comunicazioni M2M e H2H. The advent of LTE and LTE-Advanced, and their integration with existing cellular technologies, GSM and UMTS, has forced the mobile radio network operators to perform meticulous tests and adopt the right know-how to detect potential new issues, before the activation of new services. In this new network scenario, traffic characterisation and monitoring as well as configuration and on-air reliability of network equipment, is of paramount relevance in order to prevent possible pitfalls during the deployment of new services and ensure the best possible user experience. Based on this observation, this research project offers a comprehensive study that goes from experimental analysis to operational optimization. The starting point of our work has been monitoring the traffic of an already deployed eNodeB with three cells, operative in the 1800 MHz band. Through subsequent measurement campaigns, it was possible to follow the evolution of the 4G network by the beginning of its deployment in 2012, until its full maturity in 2015. The data collected during the first year, showed a poor use of the LTE network, mainly due to the limited penetration of new 4G smartphone. In 2015, however, we appreciate a clear and decisive increase in the number of terminals using LTE, with aggregate statistics (e.g. marketshare for smartphone operating systems, or the percentage of video traffic) that reflect the national trend. This important outcome testifies the maturity of LTE technology, and allows us to consider our monitored eNodeB as a valuable vantage point for traffic analysis. Hand in hand with the evolution of the infrastructure, even mobile phones have had a surprising evolution over the past two decades, from simple devices with only voice services, towards smartphones offering novel services such as mobile Internet, geolocation and maps, multimedia services, and many more. Monitoring the real traffic has allowed us to study the users behavior and identify the services most used. To this aim, various software libraries for traffic analysis have been developed. In particular, we developed a C/C++ library that analyses Control Plane and User Plane traffic, which provides corse and fined-grained statistics at flow-level. Another framework/tool has been exclusively dedicated to the topic of traffic classification. Among the plethora of existing tool for traffic classification we provide our own solution, developed from scratch. The project, which is available on github, is named MOSEC, an acronym for Modular SErvice Classifier. The modularity is given by the possibility to implement multiple plug-ins, each one will process the packet according to its logic, and may or may not return a packet/flow classification. A final decision strategy allows to classify the various streams, based on the classifications of each plug-in. Despite previous approaches, the ability of keeping together multiple classifiers allows to mitigate the deficiency of each classifiers (e.g. DPI\nomenclature{DPI}{Deep Packet Inspection} does not work when packets are encrypted or DNS\nomenclature{DNS}{Domain Name Server} queries don't have to be sent if name resolution is cached in device memory) and exploit their full-capabilities when it is feasible. We validated the goodness of MOSEC using a labelled trace synthetically created by colleagues from UPC BarcelonaTech. The results show excellent TCP-HTTP/HTTPS traffic classification capabilities, higher, on average, than those of other classification tools (NDPI, PACE, Layer-7). On the other hand, there are some shortcomings with regard to the classification of UDP traffic. The characteristics of User Plane traffic have a direct impact on the energy consumed by the handset devices, and an indirect impact on the Control Plane traffic that is generated. Therefore, the acquaintances of the statistical properties of the various flows, allows us to deal with the problem of cross-layer optimization, that is reducing the power consumption of the terminals by varying some control plane parameters configurable on the eNodeB. It is well known that the battery life of the new smartphones is one of the major limitations in the use of the same. In particular, the birth of new services and applications capable of working in the background without direct user interaction, introduced new issues related to the battery lifetime and the signaling traffic necessary to acquire/release the radio resources. Based on these observations, we conducted a thorough study on the DRX mechanism (Discontinuous Reception), exploited by LTE to save smartphones energy when no packet is sent or received. The DRX configuration set and the RRC Inactivity Timer greatly affect the energy consumed by the various devices. Depending on which radio resources are allocated or not, the user equipment is in the states of RRC Connected and Idle, respectively. To evaluate the energy consumption of smartphones, an algorithm simulates the transition between all the possible states in which an UE can be and maps a power value to each of these states. The transition from one state to another is governed by different timeouts that are reset every time a packet is sent or received. Using the traces of real traffic, we associate a state machine to each for assessing the energy consumption on the basis of the sent and received packets. We repeated these simulations using different values of the inactivity timer, that appear to be more suitable than the one currently configured on the monitored eNodeB, looking for a good trade-off between energy savings and increased signaling traffic. The results highlighted that the Inactivity Timer set originally sull'eNodeB was too high and determined an excessive energy consumption on the terminals. Reducing the value up to 10 seconds permits to achieve energy savings of up to 50\% (depending on the underling traffic profile) without up considerably the control traffic. The results of the study mentioned above, however, do not consider neither the stress level which the eNodeB is subject to, given the raise of signaling traffic that could occur, nor the increase of collision probability during the RACH procedure, needed to re-establish the radio bearer (or RRC connection ) between the terminal and eNodeB . Evaluate the performance of hardware and software systems for the fourth-generation mobile network, as well as identify any possible weakness in the architecture, it is a complex job. A possible case study, is precisely to assess the robustness of the base station when it receives many requests for RRC connections, as effect of a decrease of the inactivity timer. In this regard, within the Testing LAB of Telecom Italia, we used IxLoad, a product developed by Ixia, as a load generator to test the robustness of one eNodeB. The tests consisted in producing a different load of RRC request on the radio interface, similar to those that would be produced by decreasing the inactivity timer to certain values. The statistical properties for the signalling traffic are derived from the analysis of real traffic traces. The main outcomes have shown that, even in the face of an high load of RRC requests only a small part (less than 1\% in the most unfavorable of the cases) of the procedure fails. Therefore, even lowering the inactivity timer at values lower than 10 seconds is not an issue for the Base Station. Finally, remains to be evaluated how such surge of RRC request impacts on users performance. If one of the users under coverage in the RRC Idle is paged for an incoming packet or need to send an uplink packet a state transition from RRC Idle to RRC Connected is needed. At this point, the UE initiates the random access procedure by sending the random access channel preamble (RACH Preamble). When two or more users attempt, simultaneously, to access the RACH channel, using the same preamble, the eNodeB may not be able to decipher the preamble. If the two signals interfere constructively, both users receive the same resources for transmitting the RRC Request message and, at this point, the eNodeB can detect the collision and will not send any acknowledgment, forcing both users to restart the procedure from the beginning. We have proposed an analytical model to calculate the probability of a collision based on the number of users and the offered traffic load, when the interarrival time between requests is modeled with hyper-exponential times. In addition, we investigated some performance for Machine-to-Machine (M2M) and Human-to-Human (H2H) type communications, including the probability of correct transmission considering either the backoff time either the maximum number of allowed retransmissions, and the average time required to established a radio bearer with the access network. The results, considered as a whole, have made possible to express the guidelines to properly distribute the number of preambles in H2H and M2M communications

Apport de la Qualité de l’Expérience dans l’optimisation de services multimédia : application à la diffusion de la vidéo et à la VoIP

The emerging and fast growth of multimedia services have created new challenges for network service providers in order to guarantee the best user's Quality of Experience (QoE) in diverse networks with distinctive access technologies. Usually, various methods and techniques are used to predict the user satisfaction level by studying the combined impact of numerous factors. In this thesis, we consider two important multimedia services to evaluate the user perception, which are: video streaming service, and VoIP. This study investigates user's QoE that follows three directions: (1) methodologies for subjective QoE assessment of video services, (2) regulating user's QoE using video a rate adaptive algorithm, and (3) QoE-based power efficient resource allocation methods for Long Term Evaluation-Advanced (LTE-A) for VoIP. Initially, we describe two subjective methods to collect the dataset for assessing the user's QoE. The subjectively collected dataset is used to investigate the influence of different parameters (e.g. QoS, video types, user profile, etc.) on user satisfaction while using the video services. Later, we propose a client-based HTTP rate adaptive video streaming algorithm over TCP protocol to regulate the user's QoE. The proposed method considers three Quality of Service (QoS) parameters that govern the user perception, which are: Bandwidth, Buffer, and dropped Frame rate (BBF). The BBF method dynamically selects the suitable video quality according to network conditions and user's device properties. Lastly, we propose a QoE driven downlink scheduling method, i.e. QoE Power Escient Method (QEPEM) for LTE-A. It esciently allocates the radio resources, and optimizes the use of User Equipment (UE) power utilizing the Discontinuous Reception (DRX) method in LTE-AL'émergence et la croissance rapide des services multimédia dans les réseaux IP ont créé de nouveaux défis pour les fournisseurs de services réseau, qui, au-delà de la Qualité de Service (QoS) issue des paramètres techniques de leur réseau, doivent aussi garantir la meilleure qualité de perception utilisateur (Quality of Experience, QoE) dans des réseaux variés avec différentes technologies d'accès. Habituellement, différentes méthodes et techniques sont utilisées pour prédire le niveau de satisfaction de l'utilisateur, en analysant l'effet combiné de multiples facteurs. Dans cette thèse, nous nous intéressons à la commande du réseau en intégrant à la fois des aspects qualitatifs (perception du niveau de satisfaction de l'usager) et quantitatifs (mesure de paramètres réseau) dans l'objectif de développer des mécanismes capables, à la fois, de s'adapter à la variabilité des mesures collectées et d'améliorer la qualité de perception. Pour ce faire, nous avons étudié le cas de deux services multimédia populaires, qui sont : le streaming vidéo, et la voix sur IP (VoIP). Nous investiguons la QoE utilisateur de ces services selon trois aspects : (1) les méthodologies d'évaluation subjective de la QoE, dans le cadre d'un service vidéo, (2) les techniques d'adaptation de flux vidéo pour garantir un certain niveau de QoE, et (3) les méthodes d'allocation de ressource, tenant compte de la QoE tout en économisant l'énergie, dans le cadre d'un service de VoIP (LTE-A). Nous présentons d'abord deux méthodes pour récolter des jeux de données relatifs à la QoE. Nous utilisons ensuite ces jeux de données (issus des campagnes d'évaluation subjective que nous avons menées) pour comprendre l'influence de différents paramètres (réseau, terminal, profil utilisateur) sur la perception d'un utilisateur d'un service vidéo. Nous proposons ensuite un algorithme de streaming vidéo adaptatif, implémenté dans un client HTTP, et dont le but est d'assurer un certain niveau de QoE et le comparons à l'état de l'art. Notre algorithme tient compte de trois paramètres de QoS (bande passante, taille de mémoires tampons de réception et taux de pertes de paquets) et sélectionne dynamiquement la qualité vidéo appropriée en fonction des conditions du réseau et des propriétés du terminal de l'utilisateur. Enfin, nous proposons QEPEM (QoE Power Efficient Method), un algorithme d'ordonnancement basé sur la QoE, dans le cadre d'un réseau sans fil LTE, en nous intéressant à une allocation dynamique des ressources radio en tenant compte de la consommation énergétiqu

A methodology for obtaining More Realistic Cross-Layer QoS Measurements in mobile networks: A VoIP over LTE Use Case

Los servicios de voz han sido durante mucho tiempo la primera fuente de ingresos para los operadores móviles. Incluso con el protagonismo creciente del tráfico de datos, los servicios de voz seguirán jugando un papel importante y no desaparecerán con la transición a redes basadas en el protocolo IP. Por otra parte, hace años que los principales actores en la industria móvil detectaron claramente que los usuarios no aceptarían una degradación en la calidad de los servicios de voz. Es por esto que resulta crítico garantizar la experiencia de usuario (QoE) en la transición a redes de nueva generación basadas en conmutación de paquetes. El trabajo realizado durante esta tesis ha buscado analizar el comportamiento y las dependencias de los diferentes servicios de Voz sobre IP (VoIP), así como identificar configuraciones óptimas, mejoras potenciales y metodologías que permitan asegurar niveles de calidad aceptables al mismo tiempo que se trate de minimizar los costes. La caracterización del rendimiento del tráfico de datos en redes móviles desde el punto de vista de los usuarios finales es un proceso costoso que implica la monitorización y análisis de un amplio rango de protocolos y parámetros con complejas dependencias. Para abordar desde la raíz este problema, se requiere realizar medidas que relacionen y correlen el comportamiento de las diferentes capas. La metodología de caracterización propuesta en esta tesis proporciona la posibilidad de recoger información clave para la resolución de problemas en las comunicaciones IP, relaciolándola con efectos asociados a la propagación radio, como cambios de celda o pérdida de enlaces, o con carga de la red y limitaciones de recursos en zonas geográficas específicas. Dicha metodología se sustenta en la utilización de herramientas nativas de monitorización y registro de información en smartphones, y la aplicación de cadenas de herramientas para la experimentación extensiva tanto en redes reales y como en entornos de prueba controlados. Con los resultados proporcionados por esta serie de herramientas, tanto operadores móviles y proveedores de servicio como desarrolladores móviles podrían ganar acceso a información sobre la experiencia real del usuario y sobre cómo mejorar la cobertura, optimizar los servicios y adaptar el funcionamiento de las aplicaciones y el uso de protocolos móviles basados en IP en este contexto. Las principales contribuciones de las herramientas y métodos introducidos en esta tesis son los siguientes: - Una herramienta de monitorización multicapa para smartphones Android, llamada TestelDroid, que permite la captura de indicadores clave de rendimiento desde el propio equipo de usuario. Asimismo proporciona la capacidad de generar tráfico de forma activa y de verificar el estado de alcanzabilidad del terminal, realizando pruebas de conectividad. - Una metodología de post-procesado para correlar la información presente en las diferentes capas de las medidas realizadas. De igual forma, se proporciona la opción a los usuarios de acceder directamente a la información sobre el tráfico IP y las medidas radio y de aplicar metodologías propias para la obtención de métricas. - Se ha realizado la aplicación de la metodología y de las herramientas usando como caso de uso el estudio y evaluación del rendimiento de las comunicaciones basadas en IP a bordo de trenes de alta velocidad. - Se ha contribuido a la creación de un entorno de prueba realista y altamente configurable para la realización de experimentos avanzados sobre LTE. - Se han detectado posibles sinergias en la utilización de instrumentación avanzada de I+D en el campo de las comunicaciones móviles, tanto para la enseñanza como para la investigación en un entorno universitario