Books & Chapters

ABSTRACT
This paper focuses on multi-tenant 5G networks with virtualization and mobile edge computing capabilities, in the scope of cloud-enabled small cell deployments. In this context, the work here presented deals with the service management and orchestration challenges that arise when handling service mapping on the multi-tenant distributed cloud-enabled radio access network architecture. For that aim, once analysed cloud edge services management and 5G network instantiation in the OpenStack platform, we modify the provided virtual infrastructure manager so as to incorporate virtual network function placement features of the SESAME environment. As main contributions, we adapt the OpenStack application instances to 5G Network Service instantiation, and we include an energy-aware and latency-constrained placement solution.

ABSTRACT
Adding cognitive capabilities to the wireless networks makes it possible to leverage the control and management information used in the network operation to infer information about the local state and exploit it to improve the overall performance. This paper deals with the combined use of centralized and distributed cognitive cycles integrated at different planes in 5G networks: an integrated data plane, a unified control plane and a cross-layer management plane. This context-aware cognitive schema acts on the decision making modules depending on the monitored environment to prevent failures, balance the virtualized execution and get a global enhancement in the provision of mobile services. The multi-level cognitive cycle supports the interaction between the edge and the cloud blurring the line that separates two paradigms: centralized radio operation and mobile edge services.

ABSTRACT
Modern broadband mobile networks such as 4G LTE are designed to cope with stringent performance levels, i.e. considerable peak data rates and low latencies. With the wide-spreading of LTE networks all over the world, the access to Internet services through mobile connections is increasing considerably, leading to a plethora of mobile services. However, the inherent characteristics of the radio interface results in variable service performance. First, radio resources are shared among the different mobile users and thus the eNB scheduling functions determine the assigned share of resources for each user in a dynamic way. Moreover, the channel quality of each individual user fluctuates over time due to propagation and fading effects. These aspects introduce new issues in the tasks of performance evaluation and adaptive traffic management at different layers of the protocol stack. Currently, there is a gap between advanced research proposals and the actual network and service performance experienced in commercial mobile networks. Although it is generally assumed that the radio channel may introduce considerable quality fluctuations, there is little evidence of the quality dynamics experienced in live LTE networks at different temporal scales. This PhD work aims at providing some insights of these quality variations by analyzing the Channel State Information generated by UEs. Specifically, the document focuses on the downlink direction and on the effects of using spatial multiplexing techniques. From field testing, the main characteristics of the channel quality are studied at the scale of one second. Besides, LTE emulation tests allow evaluating the characteristics of the reported channel quality at the scale of milliseconds. Therefore, valuable information is captured for different layers of the protocol stack. Finally, the impact of the dynamics of these Channel State Information values into different adaptive traffic management schemes is evaluated. For a comprehensive analysis, different mobile network architectures are considered including classical LTE systems and novel proposals such as centralized radio access networks and mobile edge computing.

ABSTRACT
Sare baliabideen esleipenean kalitate subjektiboaren maximizaziorako planifikazioaren garrantziaren eta beharraren aurrean, lan honetan erabiltzaileek hautemandako kalitatearen maximizazioa helburutzat duen sare baliabideen planifikaziorako scheduling algoritmoetan sakondu da. Ikerketa hau matematika arloan ekarpen handia duten Gittins zein Whittle metodoen bidez lortutako kalitate subjektiboaren maximizaziorako scheduling indize erregela motako soluzioen azterketan zentratu da. Modu honetan, lehenik eta behin, bi diziplina horiek aurkeztu dira, Gittins-ena sinpleagoa izanik. Ondoren, bi planifikazio politika horien errendimendua erkatu da, Whittle-en soluzioak emaitza nabarmenki hobeak erakusten dituelarik. Ondorio bezala, indizearen konplexutasunaren eta eskuratu nahi den kalitate subjektiboaren zehaztasunaren arabera, Gittins-en edo Whittle-n oinarritutako proposamena aukeratuko da.

ABSTRACT
One of the most challenging problems in mobile broadband networks is how to assign the available radio resources among the different mobile users. Traditionally, research proposals are either specific to some type of traffic or deal with computationally intensive algorithms aimed at optimizing the delivery of general purpose traffic. Consequently, commercial networks do not incorporate these mechanisms due to the limited hardware resources at the mobile edge. Emerging 5G architectures introduce cloud computing principles to add flexible computational resources to Radio Access Networks. This paper makes use of the Mobile Edge Computing concepts to introduce a new element, denoted as Mobile Edge Scheduler, aimed at minimizing the mean delay of general traffic flows in the LTE downlink. This element runs close to the eNodeB element and implements a novel flow-aware and channel-aware scheduling policy in order to accommodate the transmissions to the available channel quality of end users.

ABSTRACT
This paper deals with the classical problem of radio resource management in LTE MIMO, with special focus to the specific radio channel characteristics in commercial LTE networks. First, we provide some conclusions about the Channel Quality Information traces obtained through field testing. From this analysis, we perform a series of experiments by means of an LTE emulator in order to evaluate the accuracy of different fading models used in the 3GPP. As a first outcome of the paper, we infer several fine-grain channel characteristics useful to feed further research work in the area of LTE MIMO. As a second contribution of the paper, we analyze the performance of classical schedulers (i.e., Round Robin, Best CQI and Proportional Fair) under the obtained LTE MIMO channel conditions. Specifically, we analyze the impact of the channel feedback reporting rate in scenarios with multiple greedy sources.

ABSTRACT
The main scope of the chapter is to present the overall QoE-driven IPTV architecture and the respective perceptual benchmarking of it via a subjective evaluation procedure. The chapter is organized as follows: Section 15.2 presents an overview of all the core components of the adaptive IPTV system (IMS, QoE, Perceptual Cross layer adaptation, network management, etc.). In Section 15.3, the user-centric IPTV architecture is presented, containing NQoS to PQoS mapping operations, the Multimedia Content Management System, the monitoring and adaptation modules presentation, the enhancements of the current IMS functions, and UMTS/ WiMAX technologies QoE/QoS mapping. Section 15.4 analyzes in depth the QoE model used for IPTV cross-layer adaptation. Section 15.5 concludes the benchmarking of the whole architecture, and finally Section 15.6 draws the conclusions.

ABSTRACT
This paper deals with the analysis of user perceived visual quality for mobile multimedia services. H.264/AVC is selected for low resolution video encoding, and 3G UMTS is considered for mobile data services. From subjective tests results, the combined impact of different service– and network–level parameters is inferred. As a result, different cross–layer adaptation alternatives are proposed to maximize the perceived quality level under different service conditions.

ABSTRACT
In this paper, we consider mobile multimedia services delivered over a UMTS network. In this convergent scenario, low level error recovery mechanisms of the access network entail that almost all packet losses are caused by frames arriving at the receiver later than the playout time. Our aim is to find a simplified yet realistic expression for the statistics of the end–to–end delay in order to characterize related application level losses and infer resulting Quality of Experience (QoE). We present a simple and easy to implement model based on empirically obtained parameters that quantitatively reflects the statistical properties of delay. We apply the model to estimate the behavior of application level losses and delay which are the key factors while forecasting QoE in VoIP. Obtained results prove the suitability of the model to be integrated in cross–layer adaptation mechanisms and its utility for dimensioning VoIP playout buffers is also tested.

ABSTRACT
This chapter proposes a Content-aware and Network-aware Management System (CNMS) over a converged user-environment of social networking and mobile multimedia. The proposed CNMS will focus on applying dynamic personalized multi-layer adaptation for the optimization of the Quality of Experience (QoE) level in a requested media service according to the users’ preferences, favourites provided in their social network profile, and prior experiences rated by users themselves. By user’s preference extraction, a service/content classification will be performed according to an estimation of the user’s favourites, which will be used to provide optimized media delivery across the delivery chain. Therefore, the end-user will always receive her/his favourite service, like Internet Protocol Television (IPTV), Voice over Internet Protocol (VoIP), interactive application/on-line gaming, web browsing, at requested QoE. The system will ensure optimal allocation of network resources and optimal selection of streaming scheme according to different services/content types and user preferences, and therefore enhance the ratio of price-for-value for the specific subscription and achieve an end-to-end, holistic QoE optimisation. Although QoE is perceived as subjective, it is the only measure that counts for customers of a service. Being able to estimate the user preferences in a controlled manner through the end-user’s social networks profiles, helps operators understand what may be wrong with their services and their respective QoE. The proposed multimodal management system is user-centric and applies advanced machine learning techniques in order to extract user preferences from the social network profile of the user and build up a ranking scale of the services/contents. This ranking scale will be translated to adaptation actions per service type at several instances such as before the provision of the service takes place (i.e. Time Zero), during the delivering of the service (i.e. Time T), across all the network layers and delivery-chain nodes, while ensuring throughout the process that the main focus on the QoS-adaptation of the mobile access network is maintained.

ABSTRACT
The advent and rise of broadband technologies and new applications and services have led to a complex heterogeneous scenario in which providing Quality of Service (QoS) has become a compelling issue. Furthermore, the competitive condition of the telecommunications environment has caused user’s perception of quality to become one of the most differential factors for service providers. Due to this fact, QoS must not only attend to specific technical metrics, but more important, QoS criteria should be defined to assure the level of quality to fulfil the users’ requirements. In this new context, the definition of effective user-oriented QoS management models and frameworks has become a matter of contention. This chapter aims to provide readers a comprehensive analysis of the entire significance of a user-centered approach for quality of service management. For this purpose, a review of the most important issues related to the subject is provided.

ABSTRACT
Future Internet will have to cope with yet unknown terminals and services (even users), in a number and heterogeneity never seen before. So, flexibility or adaptability will be considered as one of the most important design principles. This flexibility will demand different kinds of awareness both in the ends and in every node in the service supplying chain, while targeting users' satisfaction as the final goal of any management process. Although virtualization and “everything is a service” approaches seem to be promising foundations to guarantee this flexibility, Future Internet will be built upon real world mobile wireless network technologies, so that cross-layers issues and quality constraints will persist. Quality of Experience (QoE) could play a significant role there, since it could provide an unified metric, isolating users from low level details or complex NQoS definitions. We will also show an example of how user-aware network tuning mechanisms are able to provide similar users' QoE with lower resources consumption and therefore propose that QoE and *-awareness were considered in the Future Internet design from the very beginning.

ABSTRACT
The concept of PQoS, although in general it deals with the user satisfaction with a specific delivered/ requested service, is in practice significantly differentiated by the nature of each delivered service. This chapter reviews various existing PQoS assessment methods for video, VoIP, online games, and Web services that have been published in the literature. It then moves beyond the current PQoS assessment methods and presents novel techniques for predicting the PQoS of a multimedia service.

ABSTRACT
This chapter introduces the principal characteristics of MANETs and shows how these particularities may affect both QoS conditions and QoS management/provisioning systems, and therefore the capabilities of MANETs for properly providing multimedia services. After a deep analysis of different QoS mechanisms at different layers, the authors claim that QoS management cannot be handled only at the network layer or by applying some QoS-aware routing protocols. In fact, any end-to-end QoS provision architecture will demand QoS control mechanisms and information exchange among all the layers. A clear understanding of different proposals aimed at coping with QoS requirements at different layers will not only provide researchers with valuable information for designing better multimedia capable MANETs, but will also assist them in evaluating the need for a unified cross-layer approach in order to optimize the performance of analyzed protocols.

ABSTRACT
This paper proposes a service discovery protocol for discovering and advertising services in a proactive ad hoc network. The protocol we have defined is piggybacked into the OLSR protocol. We define a new message type into OLSR called Service Discovery Message (SDM) for both advertisement and discovery of services. The advertisement frequency and advertisement lifetime are user-controlled parameters, so that they can be modified depending on the user requirements. Each node maintains a service cache to store information about its own services, and the services each device discovers in the network. We also present simulation results of our protocol and show that the service discovery protocol defined here achieves much efficiency in discovering services, while it introduces practically no packet overhead compared to the basic OLSR protocol.