Fidel Liberal

Fidel Liberal
Universidad del País Vasco / Euskal Herriko Unibertsitatea | UPV/EHU · Department of Communications Engineering

Dr,

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119
Publications
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926
Citations
Additional affiliations
July 2009 - July 2009
University of Plymouth
February 2002 - present

Publications

Publications (119)
Article
Network Function Virtualization (NFV) introduces a new network architecture framework that evolves network functions, traditionally deployed over dedicated equipment, to software implementations that run on general-purpose hardware. One of the main challenges for deploying NFV is the optimal resource placement of demanded network services in the NF...
Article
Full-text available
This paper analyzes the impact of the evolution of mobile broadband networks from 4G architectures towards 5G on Mission Critical Push-to-Talk (MCPTT) key performance indicators (KPIs). This article focuses on how the deployment of MCPTT over these architectures affects the service quality. We carry out a comprehensive analysis of the call flows an...
Article
Full-text available
IP multimedia subsystem (IMS) is becoming the prevailing candidate for managing future mobile multimedia communications, including critical communications such as public safety, emergency professionals and corporate networks. IMS security and privacy has gained much attention in the few last years. The review of recent IMS security activities stres...
Chapter
In the race towards 5G, NFV (Network Functions Virtualization) arises as one of the enabler technologies. The intelligent orchestration of the network becomes a key element to achieve the demanded network slicing for an efficient allocation of the available shared virtualised resources. In this paper we propose an intelligent orchestration process...
Article
The evolution of 5G suggests that communication networks become sufficiently flexible to handle a wide variety of network services from various domains. The virtualization of small cells as envisaged by 5G, allows enhanced mobile edge computing capabilities, thus enabling network service deployment and management near the end user. This paper prese...
Article
Full-text available
The principle of Cloud Radio Access Network (C-RAN) is the split of traditional base stations into Radio Remote Units (RRU) as low-cost wireless access points, and Base Band Units (BBU) in a centralized location. This new RAN paradigm accepts several choices for a functional split of the protocol stack, with different latency requirements to the fr...
Article
Full-text available
There is a growing interest in adapting Mission Critical Public-Safety Communications from traditional private radio technologies towards 5G. The need for resiliency and strong delay requirements have resulted in Mobile Edge Computing (MEC) emerging as a key technology to improve the deployment of Public Safety applications over the mobile network....
Chapter
In this paper, we discuss the main use cases and scenarios we consider in the context of 5G ESSENCE project [1]. The first use case investigates edge network acceleration at a stadium. The second use case is focused on end-to-end slicing for mission critical applications. The third scenario considers in-flight communications and entertainment syste...
Conference Paper
A recently proposed congestion control algorithm (CCA) called BBR (Bottleneck Bandwidth and Round-trip propagation time) has shown a lot of promise in avoiding the bufferbloat and low-buffer inefficiency problems that have plagued loss-based CCAs. Nevertheless, deployment of a new alternative algorithm requires a thorough evaluation of the effect o...
Article
TCP BBR (Bottleneck Bandwidth and Round-trip propagation time) is a new TCP variant developed at Google, and which, as of this year, is fully deployed in Googles internal WANs and used by services such as Google.com and YouTube. In contrast to other commonly used TCP variants, TCP BBR is not loss-based but model-based: It builds a model of the netw...
Chapter
Mobile internet usage has significantly raised over the last decade and it is expected to grow to almost 4 billion users by 2020. Even after the great effort dedicated to the improvement of the performance, there still exist unresolved questions and problems regarding the interaction between TCP and mobile broadband technologies such as LTE. This c...
Chapter
Full-text available
The explosive growth of the Internet has fundamentally changed the global society. The emergence of concepts like service-oriented architecture (SOA), Software as a Service (SaaS), Platform as a Service (PaaS), Infrastructure as a Service (IaaS), Network as a Service (NaaS) and Cloud Computing in general has catalyzed the migration from the informa...
Chapter
Network Performance (NP)- and more recently Quality of Service/Experience/anything (QoS/QoE/QoX)-based network management techniques focus on the maximization of associated Key Performance Indicators (KPIs). Such mechanisms are usually constrained by certain thresholds of other system design parameters. e.g., typically, cost. When applied to the cu...
Conference Paper
Full-text available
Resumen Tradicionalmente han existido dos familias de tecnología separadas para proporcionar comunicaciones inalámbricas de área amplia: redes celulares comerciales y sistemas de seguridad pública dedicados, generalmente basados en redes privadas de radio (PMR), y orientados fundamentalmente a la voz. Las redes de seguridad pública proporcionan com...
Conference Paper
Full-text available
The increasing awareness in quality of service (QoS), has brought QoS measuring in Mobile Broadband (MBB) networks to become a key issue. This paper provides with an evaluation of the most significant standardized Internet access measurement methods such as TCP-based and model-based approaches over a controlled testbed and MBB monitoring infrastruc...
Conference Paper
Full-text available
Mobile wireless networks constitute an indispensable part of the global Internet, and with TCP the dominating transport protocol on the Internet, it is vital that TCP works equally well over these networks as over wired ones. This paper identifies the performance dependencies by analyzing the responsiveness of TCP NewReno and TCP CUBIC when subject...
Article
Full-text available
5G envisages a "hyper-connected society" where an enormous number of diverse entities could communicate with each other anywhere and at any time, some of which will demand extremely challenging performance requirements such as sub-millisecond latency, and higher data rates. Cloud-enabled radio access networks where intelligence is placed at the edg...
Article
Full-text available
In the context of cloud-enabled 5G radio access networks with network function virtualization capabilities, we focus on the virtual network function placement problem for a multitenant cluster of small cells that provide mobile edge computing services. Under an emerging distributed network architecture and hardware infrastructure, we employ cloud-e...
Article
Taking a look over current mobile implementations, the overhead introduced by the uplink signaling can be prevented reducing the rate of Channel Quality Information reports sent from the mobile users to the channel-aware schedulers located at base stations. In this context, the main goal of the present work is to handle the problem of scheduling tr...
Conference Paper
Full-text available
This paper analyze techniques to implement QoS/QoE on multi-tenant 5G networks. Describes the ar- chitecture of the next generation mobile network based on cloud-enabled small cell deployments and also proposes an hybrid-cloud solution coexisting with centralized cloud RAN(C-RAN), in order to achieve a gradual implementation of the technology. In t...
Conference Paper
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-enable...
Article
Full-text available
This paper proposes a novel video quality assessment method aimed for the next generation (5G) mobile networks, following the small cell deployment architecture. The proposed method is based on a novel usage of the structural similarity (SSIM) index, as a Reduced Reference metric and is suitable for implementation as a Virtual Network Function (VNF...
Article
In the context of ultra-dense heterogeneous networks in 5G, we focus on the load balancing problem of elastic traffic in a single macrocell that is supported by a number of small cells. Each small cell is modeled by a single-class processor sharing queue, whereas the macrocell is modelled by a multiclass processor sharing queue. We assume that the...
Article
Nowadays, citizens are getting used to new ways of agile communications supporting media-enriched and context-aware information. However, the adoption of these evolved technologies in emergency communications between citizens and public authorities faces a series of barriers, including the lack of harmonized and interoperable solutions. Different i...
Conference Paper
Full-text available
The Cloud Enabled Small Cell (CESC) concept proposed in EU funded project SESAME has emerged as a promising solution to form a multi-tenant, multi-service architecture at the network edge according to 5G needs. It allows several operators/service providers to engage in a sharing model of both radio access capacity and Mobile Edge Computing (MEC) ca...
Article
Full-text available
5G envisages a "hyper-connected society" where trillions of diverse entities could communicate with each other anywhere and at any time, some of which will demand extremely challenging performance requirements such as sub-millisecond low latency. Mobile Edge Computing (MEC) concept where application computing resources are deployed at the edge of t...
Conference Paper
The proper execution of performance tests is of utmost importance for the analysis and evaluation of Internet-related technologies, protocols and deployment strategies. There are plenty of tools available for experimenters ranging from simulation tools, emulation equipment, to small and large scale experimentation testbeds. Each of these performanc...
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Hurrengo belaunaldiko sareen kudeaketak eskakizun erronkariei aurre egin behar izango die NFV(Network Function Virtualization), MEC (Mobile Edge Computing) eta SDN (Software Defined Radio) bezalako teknologia gaitzaileen aplikazioaren bitartez. Horrelako kudeaketa egoera konplexuan, adimen artifizialaren erabilpena ziklo kognitibo gisa erreminta ez...
Conference Paper
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 d...
Article
Many years of research have been dedicated toward the definition of sophisticated quality of service (QoS) measurement tools and methods. Nonetheless, the results given to end users by most commonly used online speed measurement tools are still far from being accurate. Among other factors, the reliability of the measurement methods is affected by d...
Article
Full-text available
A reduced-reference video quality assessment (VQA) method was proposed by using structural similarity (SSIM) index as a tool to extract features from both the original and the target video sequences, using a reference video pattern. The method is suitable for monitoring the video quality in real time and across the service provision chain. The perf...
Conference Paper
Nowadays, more than two billion people uses the mobile internet, and it is expected to rise to almost 4 billion by 2020. Still, there is a gap in the understanding of how TCP and its many variants work over LTE. To this end, this paper evaluates the extent to which five common TCP variants, CUBIC, NewReno, Westwood+, Illinois, and CAIA Delay Gradie...
Article
Full-text available
Current trends in broadband mobile networks are addressed towards the placement of different capabilities at the edge of the mobile network in a centralised way. On one hand, the split of the eNB between baseband processing units and remote radio headers makes it possible to process some of the protocols in centralised premises, likely with virtual...
Conference Paper
After several years of research towards sophisticated QoS measurement tools and methods, the results given to end users by most commonly used on-line speed measurement tools are still far from being precise. In order to define a reliable Internet speed measurement methodology for end users, the impact that the static and dynamic constraints of netw...
Conference Paper
The evolution of Internet access technologies, together with the wide diversity of customer devices, has led to a complex scenario where measuring basic metrics with accuracy has become a rather complicated task. Although nowadays there are a lot of tools to assess the rate of Internet speed, most of them share neither the methodology nor the infra...
Conference Paper
Full-text available
The primary goal of Network Function Virtualization (NFV) is the migration of physical network functions to software versions running on virtual machines (VM) in cloud computing environments. Rapid developments in virtualization technologies have made high-speed network connections and line rate packet processing viable in virtualized infrastructur...
Article
Full-text available
This article presents a novel architecture for optimizing HTTP-based multimedia delivery in multi-user mobile networks. This proposal combines the usual client-driven dynamic adaptation scheme DASH-3GPP with network-assisted adaptation capabilities, in order to maximize the overall quality of experience. The foundation of this combined adaptation s...
Conference Paper
Full-text available
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,...
Article
Lan honetan sakon aztertu dira erabiltzaileek hautemandako kalitatearen maximizazioa helburu duen sare-baliabideen planifikaziorako scheduling algoritmoak, beti ere sare-baliabideen esleipenean kalitate subjektiboaren maximizaziorako planifikazioaren garrantzia eta beharra buruan izanda. Ikerketak bereziki erreparatu dio matematika arloan ekarpen h...
Article
Full-text available
A video quality assessment mechanism for next-generation (5G) mobile networks uses the small cell deployment architecture to implement a virtual network function to enable in-service monitoring of delivered video quality.
Conference Paper
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 m...
Article
Full-text available
IP multimedia subsystem (IMS) is becoming the prevailing candidate for managing future mobile multimedia communications, including critical communications such as public safety, emergency professionals and corporate networks. IMS security and privacy has gained much attention in the few last years. The review of recent IMS security activities stres...
Article
Most multimedia applications implement some kind of packet losses analysis mechanism to trigger self-adaptation actions. However, error recovery mechanisms such as ARQ variants avoid packet losses at IP level. Then, there appears an impact into the delay that may indeed result on application-level losses due to samples arriving later than the sched...
Article
In this paper we study how to design a scheduling strategy aimed at minimizing the average holding cost for flows with general size distribution when the feasible transmission rate of each user varies randomly over time. We employ a Whittle-index-based approach in order to achieve an opportunistic and non-anticipating size-aware scheduling index ru...
Conference Paper
In this paper we study how to design an opportunistic scheduler when flow sizes have a general service time distribution with the objective of minimizing the expected holding cost. We allow the channel condition to have two states which in particular covers the important special case of ON/OFF channels. We formulate the problem as a multi-armed res...
Article
Full-text available
This paper deals with the resource allocation problem aimed at maximizing users’ perception of quality in wireless channels with time-varying capacity. First of all, we model the subjective quality-aware scheduling problem in the framework of Markovian decision processes. Then, given that the obtaining of the optimal solution of this model is unac...
Article
The characterization of human interaction at different levels has been a matter of interest in many disciplines. So far, social networking through the Internet has been the main source to infer human beings’ relations. Nevertheless, due to the irruption of wearable devices with wireless communication capabilities, initiatives that use them to measu...
Conference Paper
This paper deals with the performance evaluation of deploying an IMS-based media plane interoperability framework. The 3GPP standards describe two possible operating modes based on either a reactive or a proactive approach. We show that both approaches entail some advantages and drawbacks in terms of signaling overhead and call setup times at diffe...
Conference Paper
Nowadays, the Critical Communications networks are experiencing the transformation that will lay the foundations for next decades of emergency communications. Although different forums claim for the benefits of different technological solutions, this evolution seems to be driven towards the adoption of commercial radio technologies and mass market...
Conference Paper
This paper analyzes the scenario where multiple users are trying to transmit the same or related content to a common destination through a shared radio access network. A specific aspect of this study is that all users work for a common objective, as it would be the transmission of critical emergency-related media contents to a central operator. We...
Article
This paper deals with the analysis of mobile multimedia services, with special focus on current media resolutions for mobile handsets. Since variable network conditions entail variable quality levels, nowadays several applications implement some kind of dynamic service adaptation in order to mitigate these effects. This paper analyzes the service p...
Article
This paper highlights the challenges to be taken into consideration when Bluetooth is used as a radio technology to capture proximity traces between people. Our study analyzes the limitations of Bluetooth-based trace acquisition initiatives carried out until now in terms of granularity and reliability. We then propose an optimal configuration for t...
Article
The evolution of smart vehicles has widened the application opportunities for vehicular ad hoc networks. In this context, the routing issue is still one of the main challenges regarding to the performance of the network. Although there are multiple ad hoc routing proposals, the traditional general-purpose approaches do not fit the distinctive prope...
Conference Paper
Full-text available
Currently, the critical communications sector is aware of the need for evolving the portfolio of service capabilities to support advanced multimedia communications in their daily emergency operations. However, there is a discussion about the evolving the private communication networks or adopting commercial network technologies, which have evolved...
Conference Paper
The great technological evolution achieved in the field of public communication networks in comparison to the slower pace of the critical communications sector has raised discussions regarding the next evolutionary steps of PMR technologies and the integration of mission critical aspects into public wideband networks. This paper analyses a converge...
Conference Paper
Emergency telecommunication systems play an important role in people’s daily life, supporting communication for the public and first responders during emergency related incidents. Nonetheless, the majority of existing emergency communications are limited to traditional voice and text message services due to the data bandwidth constraint of current...
Conference Paper
Full-text available
This paper presents a novel open-source implementation of a call center, which is compatible with the IP Multimedia Subsystem (IMS) platform, supporting call forwarding and dispatching services, along with video call and chat with file transfer. The proposed solution is called Call Center for IMS (CC4IMS) and following a requirement analysis, the p...
Article
This paper deals with the subjective quality maximization problem when scheduling multimedia traffic flows in a shared channel. In order to quantify such user satisfaction a utility function dependent on flow transfer delay is used. In this context, we formulate the Quality of Experience aware resource allocation optimization problem as a Markov De...
Article
A major issue in the application of ad hoc networking to Wireless Networked Robotics is the choice of the routing protocol that performs better in a given scenario. However, far too little attention has been paid to routing issues involving enhanced robotic nodes. In view of the lack of a significant and comprehensive analysis, this research work c...
Article
Full-text available
Scalable video coding allows an efficient provision of video services at different quality levels with different energy demands. According to the specific type of service and network scenario, end users and/or operators may decide to choose among different energy versus quality combinations. In order to deal with the resulting trade-off, in this pa...
Chapter
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 th...
Article
Full-text available
This paper deals with the problem of scheduling mobile Internet traffic over a single cell wireless downlink data channel. On the one hand, we compare the performance of different size-based or/and channel-aware scheduling disciplines in mean delay terms, concluding that an approach that combines both size- and channel-awareness is the best alterna...
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