http://hdl.handle.net/2117/5476 2013-06-19T08:39:24Z http://hdl.handle.net/2117/17447 Title: Leveraging 802.11n frame aggregation to enhance QoS and power consumption in Wi-Fi networks Authors: Camps Mur, Daniel; Gomony, M.D.; Pérez Costa, Xavier; Sallent Ribes, Sebastián Abstract: The Wi-Fi technology, driven by its tremendous success, is expanding into a wide variety of devices and applications. However, many of these new devices, like handheld devices, pose new challenges in terms of QoS and energy efficiency. In order to address these challenges, in this paper we study how the novel MAC aggregation mechanisms developed in the 802.11n standard can be used to enhance the current 802.11 QoS and power saving protocols. Our contribution is twofold. First, we present a simulation study that illustrates the interactions between 802.11n and the current 802.11 QoS and power saving protocols. This study reveals that the 802.11n MAC aggregation mechanisms perform better when combined with the power save mode included in the original 802.11 standard than with the 802.11e U-APSD protocol. Second, we design CA-DFA, an algorithm that, using only information available at layer two, adapts the amount of 802.11n aggregation used by a Wi-Fi station according to the level of congestion in the network. A detailed performance evaluation demonstrates the benefits of CA-DFA in terms of QoS, energy efficiency and network capacity with respect to state of the art alternatives. 2013-01-21T16:37:51Z http://hdl.handle.net/2117/17262 Title: Optimal mapping of virtual networks with hidden hops Authors: Botero Vega, Juan Felipe; Hesselbach Serra, Xavier; Fischer, Andreas; de Meer, Hermann Abstract: Network virtualization has emerged as a solution for the Internet inability to address the required challenges caused by the lack of coordination among Internet service providers for the deployment of new services. The allocation of resources is one of the main problems in network virtualization, mainly in the mapping of virtual nodes and links to specific substrate nodes and paths, also known as the virtual network embedding problem. This paper proposes an algorithm based on optimization theory, to map the virtual links and nodes requiring a specific demand, looking for the maximization of the spare bandwidth and spare CPU in the substrate network, taking into account the CPU demanded by the hidden hops when a virtual link is mapped. The components of the virtual networks (nodes and links) that do not ask for an specific demand are then allocated following a fairness criteria 2013-01-10T13:11:39Z http://hdl.handle.net/2117/17181 Title: On centralized schedulers for 802.11e WLANs distribution versus grouping of resources allocation Authors: Mur, D.C.; Pérez Costa, Xavier; Marchenko, V.; Sallent Ribes, Sebastián Abstract: Wireless LAN is becoming a pervasive wireless access technology that can be found in almost any mobile device such as laptops, PDAs, portable game consoles and mobile phones. Each of these groups of devices have a different set of requirements according to their intended use and applications but most of them share two main requirements: QoS support to satisfy applications’ demands and power saving functionality to achieve an operating time according to users’ expectations. IEEE 802.11e defines two centralized solutions in order to address these problems: Hybrid Coordination Channel Access (HCCA) for QoS and Scheduled Automatic Power Save Delivery (S-APSD) for power saving. The focus of our work in this paper is the analysis and evaluation of a proposed centralized scheduler that makes use of both aforementioned IEEE 802.11e QoS and power saving solutions. Our contributions are as follows: (i) Design and analytical modeling of a proposed centralized scheduler (DRA) that maximizes the minimum distance between the resource allocations with pseudopolynomial complexity, (ii) Extensive performance evaluation of the QoS and power saving benefits of the Distribution proposal (DRA) as compared to a generic Grouping one (GRA), and (iii) Evaluation of the complexity and scalability of the proposal to assess its feasibility in practice. 2012-12-20T15:40:48Z http://hdl.handle.net/2117/17176 Title: Magnetic induction for underwater wireless communication networks Authors: Domingo Aladrén, Mari Carmen Abstract: Although acoustic waves are the most versatile and widely used physical layer technology for underwater wireless communication networks (UWCNs), they are adversely affected by ambient noise, multipath propagation, and fading. The large propagation delays, low bandwidth, and high bit error rates of the underwater acoustic channel hinder communication as well. These operational limits call for complementary technologies or communication alternatives when the acoustic channel is severely degraded. Magnetic induction (MI) is a promising technique for UWCNs that is not affected by large propagation delays, multipath propagation, and fading. In this paper, the MI communication channel has been modeled. Its propagation characteristics have been compared to the electromagnetic and acoustic communication systems through theoretical analysis and numerical evaluations. The results prove the feasibility of MI communication in underwater environments. The MI waveguide technique is developed to reduce path loss. The communication range between source and destination is considerably extended to hundreds of meters in fresh water due to its superior bit error rate performance. 2012-12-20T14:03:51Z http://hdl.handle.net/2117/17166 Title: Energy efficient virtual network embedding Authors: Botero Vega, Juan Felipe; Hesselbach Serra, Xavier; Duelli, Michael; Schlosser, Daniel; Fischer, A.; de Meer, Hermann Abstract: Waste of energy due to over-provisioning and overdimensioning of network infrastructures has recently stimulated the interest on energy consumption reduction by Internet Service Providers (ISPs). By means of resource consolidation, network virtualization based architectures will enable energy saving. In this letter, we extend the well-known virtual network embedding problem (VNE) to energy awareness and propose a mixed integer program (MIP) which provides optimal energy efficient embeddings. Simulation results show the energy gains of the proposed MIP over the existing cost-based VNE approach. 2012-12-19T19:13:45Z http://hdl.handle.net/2117/17159 Title: Throughput efficiency in body sensor networks: a clean-slate approach Authors: Domingo Aladrén, Mari Carmen Abstract: In this paper, a flexible role-based architecture for Body Sensor Networks (BSNs) is introduced. The proposed non-layered context-aware architecture is application-oriented and able to incorporate future applications. Particular applications have certain requirements. Functional units (roles) instead of protocol layers are designed to perform the required tasks for applications to work properly. The role data of an application is inserted in the role headers of the container and is available for other applications with the same basic, specific or particular roles. Furthermore, the performance of Automatic Repeat Request (ARQ), Forward Error Correction (FEC) block codes and FEC convolutional codes with respect to the throughput efficiency has also been analyzed for a BSN following the proposed role-based architecture. The numerical results show that the proposed role-based architecture outperforms the traditional layered architecture with respect to the throughput efficiency for all error control schemes. FEC block codes are able to maintain a high throughput efficiency over longer distances because the hop length extension technique is applied. 2012-12-19T17:00:29Z http://hdl.handle.net/2117/15599 Title: Performance analysis of AND gates based on four-wave-mixing for application in optical-code division multiple access systems Authors: Noshad, M.; Noshad, M.; AlaviRad, S.M.; Sallent Ribes, Sebastián Abstract: In this paper, we study the performance of all optical AND gates based on the four-wave-mixing (FWM) process, for application in the receivers of the spectral phase encoded optical code division multiple access (SPE-OCDMA) systems. For the performance analysis, the spectral domain auto-correlation function of the multiple access interference signal at the output of the optical AND gate is derived and then mean and variance of the photo-detector current are calculated. For solving the Fourier transform of FWM non-linear Schrodinger equations, spectral domain Volterra series are used and the solution of these coupled equations is approximated with the first three terms of the Volterra expansion. Finally, the performance of AND gating receivers in SPE-OCDMA systems is analysed and the bit error rate in terms of the pump power and the number of active users is depicted. In addition, a compression between the performance of the time-gating receivers, base on FWM in synchronous mode and other non-linear receivers such as second harmonic generation and self-phase modulation is made. 2012-03-15T18:58:33Z http://hdl.handle.net/2117/15598 Title: Wireless ad hoc networks: an overview Authors: Remondo Bueno, David Abstract: This tutorial provides a general view on the research field of ad hoc networks. After a definition of the concept, the discussion concentrates on enabling technologies, including physical and medium access control layers, networking and transport issues. We find discussions on the adequacy of enabling technologies for wireless multihop communication, specifically in the case of the pervasive Bluetooth and IEEE 802.11. Then, a variety of dynamic routing protocols are presented and specific issues that are relevant in this context are highlighted. After a short discussion on TCP issues in this context, we look at power awareness, which is a very important issue in this scenario. Finally, we discuss proposals that aim at maintaining Service Level Agreements in isolated ad hoc networks and ad hoc networks connected to fixed networks. 2012-03-15T18:50:33Z http://hdl.handle.net/2117/15595 Title: Content distribution over IP: developments and challenges Authors: Popescu, Adrian; Kouvatsos, D; Remondo Bueno, David; Giordano, Stefano Abstract: This chapter focuses on the multimedia distribution over Internet IP under the auspices of the NoE Euro-NGI research project ”Routing in Overlay Networks (ROVER)”. The multimedia distribution is supported by several components such as services, content distribution chain, protocols and standards whilst Internet is used for content acquisition, management and delivery as well as an Internet Protocol Television (IPTV) infrastructure with QoS facilities. As the convergence between fixed and mobile services of wide and local area networks is also expected to take place in the home networking, this puts an extra burden on multimedia distribution, which requires the different types of wireless access solutions (e.g., WiMAX). In this context, the ROVER research project adopts the IP Multimedia Subsystem (IMS), which offers a wide range of multimedia services over a single IP infrastructure such as authentication and, for wireless services, roaming capabilities. The research project also considers overlay routing as an alternative solution for content distribution. 2012-03-15T18:43:47Z http://hdl.handle.net/2117/15591 Title: Enabling future internet research: the FEDERICA case Authors: Naegele-Jackson, S.; Lopez, V.; Cervelló Pastor, Cristina; Power, G.; Ponce de Leon, M.; Giraudo, L.; Bianco, A.; Szegedi, P.; Riera, J. F.; García-Espín, Joan Antoni; Hidell, M.; Sjodin, P.; Soderman, P.; Ruffini, M.; O'Mahony, D. Abstract: The Internet, undoubtedly, is the most influential technical invention of the 20th century that affects and constantly changes all aspects of our day-to-day lives nowadays. Although it is hard to predict its long-term consequences, the potential future of the Internet definitely relies on future Internet research. Prior to every development and deployment project, an extensive and comprehensive research study must be performed in order to design, model, analyze, and evaluate all impacts of the new initiative on the existing environment. Taking the ever-growing size of the Internet and the increasing complexity of novel Internet-based applications and services into account, the evaluation and validation of new ideas cannot be effectively carried out over local test beds and small experimental networks. The gap which exists between the small-scale pilots in academic and research test beds and the realsize validations and actual deployments in production networks can be bridged by using virtual infrastructures. FEDERICA is one of the facilities, based on virtualization capabilities in both network and computing resources, which creates custom-made virtual environments and makes them available for Future Internet Researchers. This article provides a comprehensive overview of the state-of-the-art research projects that have been using the virtual infrastructure slices of FEDERICA in order to validate their research concepts, even when they are disruptive to the test bed’s infrastructure, to obtain results in realistic network environments. 2012-03-15T18:36:12Z http://hdl.handle.net/2117/15589 Title: Energy-efficient wireless mesh infrastructures Authors: Al-Hazmi, Y.; de Meer, Hermann; Hummel, Karin Anna; Meyer, Harald; Meo, Michela; Remondo Bueno, David Abstract: The Internet comprises access segments with wired and wireless technologies. In the future, we can expect wireless mesh infrastructures (WMIs) to proliferate in this context. Due to the relatively low energy efficiency of wireless transmission, as compared to wired transmission, energy consumption of WMIs can represent a significant part of the energy consumption of the Internet as a whole. We explore different approaches to reduce energy consumption in WMIs, taking into account the heterogeneity of the technologies and the interaction with wired networks. Finally, we present an example scenario where the application of these methods is discussed. 2012-03-15T18:30:09Z http://hdl.handle.net/2117/15587 Title: A context-aware service architecture for the integration of body sensor networks and social networks through IP multimedia subsystem Authors: Domingo Aladrén, Mari Carmen Abstract: In this article a new context-aware architecture is proposed for the integration of body sensor networks and social networks through the IP Multimedia Subsystem. Its motivating application scenarios are described. The benefits and main research challenges for an efficient communication using the proposed architecture are outlined. 2012-03-15T18:26:18Z http://hdl.handle.net/2117/15585 Title: Securing underwater wireless communication networks Authors: Domingo Aladrén, Mari Carmen Abstract: Underwater wireless communication networks are particularly vulnerable to malicious attacks due to the high bit error rates, large and variable propagation delays, and low bandwidth of acoustic channels. The unique characteristics of the underwater acoustic communication channel, and the differences between underwater sensor networks and their ground-based counterparts require the development of efficient and reliable security mechanisms. In this article, a complete survey of security for UWCNs is presented, and the research challenges for secure communication in this environment are outlined. 2012-03-15T18:22:07Z http://hdl.handle.net/2117/15584 Title: A distributed energy-aware routing protocol for underwater wireless sensor networks Authors: Domingo Aladrén, Mari Carmen Abstract: The design of routing protocols for Underwater Wireless Sensor Networks (UWSNs) poses many challenges due to the intrinsic properties of underwater environments. In this paper we present DUCS (Distributed Underwater Clustering Scheme), a new GPSfree routing protocol that does not use flooding techniques, minimizes the proactive routing message exchange and uses data aggregation to eliminate redundant information. Besides, DUCS assumes random node mobility and compensates the high propagation delays of the underwater medium using a continually adjusted timing advance combined with guard time values to minimize data loss. The theoretical and simulation studies carried out demonstrate its effectiveness. 2012-03-15T18:16:39Z http://hdl.handle.net/2117/14226 Title: Time Shared Optical Network (TSON): a novel metro architecture for flexible multi-granular services Authors: Zervas, Georgios S.; Triay Marquès, Joan; Amaya, Norberto; Qin, Yixuan; Cervelló Pastor, Cristina; Simeonidou, Dimitra Abstract: This paper presents the Time Shared Optical Network (TSON) as metro mesh network architecture for guaranteed, statistically-multiplexed services. TSON proposes a flexible and tunable time-wavelength assignment along with one-way tree-based reservation and node architecture. It delivers guaranteed sub-wavelength and multi-granular network services without wavelength conversion, time-slice interchange and optical buffering. Simulation results demonstrate high network utilization, fast service delivery, and low end-to-end delay on a contention-free subwavelength optical transport network. In addition, implementation complexity in terms of Layer 2 aggregation, grooming and optical switching has been evaluated. 2011-12-13T09:39:46Z