http://hdl.handle.net/2117/3172 Wed, 19 Jun 2013 22:38:23 GMT 2013-06-19T22:38:23Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/19586 Title: Real-time multimedia monitoring in large-scale wireless multimedia sensor networks: research challenges Authors: Cesana, Matteo; Redondi, Alessandro; Tiglao, Nestor; Grilo, Antonio; Barceló Ordinas, José María; Alaei, Mohammad; Todorova, Petia Abstract: Wireless Sensor Networks (WSNs) have enjoyed dramatic developments over the last decade. The availability of CMOS cameras and microphones enlarged the scope of WSNs paving the way to the development of Wireless Multimedia Sensor Networks (WMSN). Among the envisaged WMSN applications, Real-time Multimedia Monitoring constitutes one of the most promising. However, the resource requirements of these applications place difficult challenges in terms of network lifetime and scalability. This paper starts by identifying the main characteristics and requirements of Real-time Multimedia Monitoring applications and then highlights key research directions that may help to overcome those challenges. Wed, 19 Jun 2013 14:48:32 GMT http://hdl.handle.net/2117/19586 2013-06-19T14:48:32Z Cesana, Matteo; Redondi, Alessandro; Tiglao, Nestor; Grilo, Antonio; Barceló Ordinas, José María; Alaei, Mohammad; Todorova, Petia no CMOS camera, Monitoring applications, Network lifetime, Realtime multimedia, Research challenges, Research directions, Resource requirements, Wireless multimedia sensor network, Wireless sensor network (WSNs) Wireless Sensor Networks (WSNs) have enjoyed dramatic developments over the last decade. The availability of CMOS cameras and microphones enlarged the scope of WSNs paving the way to the development of Wireless Multimedia Sensor Networks (WMSN). Among the envisaged WMSN applications, Real-time Multimedia Monitoring constitutes one of the most promising. However, the resource requirements of these applications place difficult challenges in terms of network lifetime and scalability. This paper starts by identifying the main characteristics and requirements of Real-time Multimedia Monitoring applications and then highlights key research directions that may help to overcome those challenges. http://hdl.handle.net/2117/19486 Title: A hybrid cooperative design for energy-efficient surveillance in wireless multimedia sensor networks Authors: Alaei, Mohammad; Barceló Ordinas, José María Abstract: In Wireless Multimedia Sensor Networks (WMSNs) the lifetime of battery-operated visual nodes is limited by their energy consumption, which is proportional to the energy required for sensing, processing, and transmitting the data. Given the large amount of data generated by the visual nodes, both processing and transmitting image data are quite costly in terms of energy in comparison with other types of sensor networks. Therefore, energy efficiency is a main concern in WMSNs. In this paper an energy efficient collaborative mechanism for environment surveillance is proposed. The proposed scheme employs a mixed random deployment of acoustic and visual sensor nodes. Acoustic sensors detect and localize the occurred event/object(s) in a duty-cycled manner by sampling the received signals and then trigger the visual sensor nodes covering the objects to monitor them. Hence, visual sensors are warily scheduled to be awakened just for monitoring the object(s) detected in their domain, otherwise they save their energy. Mon, 03 Jun 2013 09:35:59 GMT http://hdl.handle.net/2117/19486 2013-06-03T09:35:59Z Alaei, Mohammad; Barceló Ordinas, José María no Wireless multimedia sensor network, Energy efficiency, Surveillance, Collaboration, Node scheduling In Wireless Multimedia Sensor Networks (WMSNs) the lifetime of battery-operated visual nodes is limited by their energy consumption, which is proportional to the energy required for sensing, processing, and transmitting the data. Given the large amount of data generated by the visual nodes, both processing and transmitting image data are quite costly in terms of energy in comparison with other types of sensor networks. Therefore, energy efficiency is a main concern in WMSNs. In this paper an energy efficient collaborative mechanism for environment surveillance is proposed. The proposed scheme employs a mixed random deployment of acoustic and visual sensor nodes. Acoustic sensors detect and localize the occurred event/object(s) in a duty-cycled manner by sampling the received signals and then trigger the visual sensor nodes covering the objects to monitor them. Hence, visual sensors are warily scheduled to be awakened just for monitoring the object(s) detected in their domain, otherwise they save their energy. http://hdl.handle.net/2117/19476 Title: A multi-tenancy model based on resource capabilities and ownership for infrastructure management Authors: Garcia Espin, Joan Antoni; Ferrer Riera, Jordi; Figuerola Fernández, Sergi; López Berga, Ester Abstract: This paper presents a multi-tenancy model based on infrastructure resource capability virtualisation. The model, namely Resources, Ownership, Roles and Actors or RORA, approaches network and IT infrastructure virtualisation seamlessly, thus enabling complex provisioning workflows for Cloud services and network services attached. Fri, 31 May 2013 13:09:00 GMT http://hdl.handle.net/2117/19476 2013-05-31T13:09:00Z Garcia Espin, Joan Antoni; Ferrer Riera, Jordi; Figuerola Fernández, Sergi; López Berga, Ester no business roles, cloud services, infrastructure provisioning, multi-tenancy, virtualisation This paper presents a multi-tenancy model based on infrastructure resource capability virtualisation. The model, namely Resources, Ownership, Roles and Actors or RORA, approaches network and IT infrastructure virtualisation seamlessly, thus enabling complex provisioning workflows for Cloud services and network services attached. http://hdl.handle.net/2117/19456 Title: Analysis of guifi.net's topology: extension of results Authors: Cerdà Alabern, Llorenç Abstract: This report extends the analysis carried out in a previous work [1] about the topology of guifi.net wireless community network. The main objective is validating the topology generator proposed in [1] for guifi.net like topologies by considering a larger number of zones. The numerical results obtained in this report are in line with those obtained before, confirming the topology generator. Additionally, new results are presented, as the link ength distribution. Description: Report de recerca del Departament d'Arquitectura de Computadors Thu, 30 May 2013 11:41:20 GMT http://hdl.handle.net/2117/19456 2013-05-30T11:41:20Z Cerdà Alabern, Llorenç no guifi.net, Wireless community networks, Graph theory, Network topology generator This report extends the analysis carried out in a previous work [1] about the topology of guifi.net wireless community network. The main objective is validating the topology generator proposed in [1] for guifi.net like topologies by considering a larger number of zones. The numerical results obtained in this report are in line with those obtained before, confirming the topology generator. Additionally, new results are presented, as the link ength distribution. http://hdl.handle.net/2117/19455 Title: Selected topics in opportunistic routing in wireless networks Authors: Darehshoorzadeh, Amir; Cerdà Alabern, Llorenç Abstract: Oportunistic Routing (OR) has been investigated in recent years as a way to increase the performance of Wireless Mesh Networks. In OR, in contrast to traditional routing, instead of pre-selecting a single specific node to be the next-hop as a forwarder for a packet, an ordered set of nodes, called candidates, is selected. When the current node transmits a packet, all the candidates that successfully receive it will coordinate with each other to determine which one will actually forward it, while the others will simply discard the packet. This book is a research approach to OR. Analytic models and simulation are used to investigate main issues in OR. These include practical ones, as the selection of candifates and theoretical ones, as the maximum performance that may be achieved using OR. Thu, 30 May 2013 10:14:22 GMT http://hdl.handle.net/2117/19455 2013-05-30T10:14:22Z Darehshoorzadeh, Amir; Cerdà Alabern, Llorenç no Oportunistic Routing (OR) has been investigated in recent years as a way to increase the performance of Wireless Mesh Networks. In OR, in contrast to traditional routing, instead of pre-selecting a single specific node to be the next-hop as a forwarder for a packet, an ordered set of nodes, called candidates, is selected. When the current node transmits a packet, all the candidates that successfully receive it will coordinate with each other to determine which one will actually forward it, while the others will simply discard the packet. This book is a research approach to OR. Analytic models and simulation are used to investigate main issues in OR. These include practical ones, as the selection of candifates and theoretical ones, as the maximum performance that may be achieved using OR. http://hdl.handle.net/2117/19446 Title: Community-Lab: Overview and invitation to the research community Authors: Navarro Moldes, Leandro; Escrich, Pau; Baig, Roger; Neumann, Axel Abstract: Community-Lab is an open, distributed infrastructure for researchers to experiment with Community Networks, that are large scale, self-organized and decentralized networks and services built and operated by citizens for citizens. The goal of Community-Lab is to advance research and empower society by understanding and removing obstacles for these networks and services. This article outlines Community-Lab’s aim, development, characteristics and infrastructure. This demonstration presents its current status of development and deployment, a sample decentralized experiment, and an invitation to the broader large-scale distributed computing research community to participate in the project through an open call. Wed, 29 May 2013 12:18:13 GMT http://hdl.handle.net/2117/19446 2013-05-29T12:18:13Z Navarro Moldes, Leandro; Escrich, Pau; Baig, Roger; Neumann, Axel no Community-Lab is an open, distributed infrastructure for researchers to experiment with Community Networks, that are large scale, self-organized and decentralized networks and services built and operated by citizens for citizens. The goal of Community-Lab is to advance research and empower society by understanding and removing obstacles for these networks and services. This article outlines Community-Lab’s aim, development, characteristics and infrastructure. This demonstration presents its current status of development and deployment, a sample decentralized experiment, and an invitation to the broader large-scale distributed computing research community to participate in the project through an open call. http://hdl.handle.net/2117/19378 Title: A summary of virtualization techniques Authors: Rodríguez Haro, Fernando; Freitag, Fèlix; Navarro Moldes, Leandro; Hernández Sánchez, Efraín; Farías Mendoza, Nicandro; Guerrero Ibáñez, Juan Antonio; González Potes, Apolinar Abstract: Nowadays, virtualization is a technology that is applied for sharing the capabilities of physical computers by splitting the resources among OSs. The concept of Virtual Machines (VMs) started back in 1964 with a IBM project called CP/CMS system. Currently, there are several virtualization techniques that can be used for supporting the execution of entire operating systems. We classify the virtualization techniques from the OS view. First, we discuss two techniques that executes modified guest OSs: operating system-level virtualization and para-virtualization. Second, we discuss two techniques that executes unmodified guest OSs: binary translation and hardware assisted. Finally, we present a summary of resource management facilities for capacity planning and consolidation of server applications. Thu, 23 May 2013 10:14:43 GMT http://hdl.handle.net/2117/19378 2013-05-23T10:14:43Z Rodríguez Haro, Fernando; Freitag, Fèlix; Navarro Moldes, Leandro; Hernández Sánchez, Efraín; Farías Mendoza, Nicandro; Guerrero Ibáñez, Juan Antonio; González Potes, Apolinar no Virtualization, Capacity planning, Hypervisor, CPU, Tools Nowadays, virtualization is a technology that is applied for sharing the capabilities of physical computers by splitting the resources among OSs. The concept of Virtual Machines (VMs) started back in 1964 with a IBM project called CP/CMS system. Currently, there are several virtualization techniques that can be used for supporting the execution of entire operating systems. We classify the virtualization techniques from the OS view. First, we discuss two techniques that executes modified guest OSs: operating system-level virtualization and para-virtualization. Second, we discuss two techniques that executes unmodified guest OSs: binary translation and hardware assisted. Finally, we present a summary of resource management facilities for capacity planning and consolidation of server applications. http://hdl.handle.net/2117/19366 Title: IT or not to be: the impact of Moodle in the education of developing countries Authors: García Almiñana, Jordi; Somé, Michel; Ayguadé Parra, Eduard; Cabré Garcia, José M.; Casany Guerrero, María José; Frigola Bourlon, Manel; Galanis, Nikolaos; García-Cervigon Gutiérrez, Manuel; Guerrero Zapata, Manel; Muñoz Gracia, María del Pilar Abstract: E-learning environments, such as Moodle, provide a technology that fosters the improvement of the educational system in developed countries, where education is traditionally performed with relatively high standards of quality. A large number of case studies and research have been conducted to demonstrate how e-learning technologies can be applied to improve both training and learning processes. However, these technologies have not been proved efficient when applied to developing countries. The challenges that must be addressed in developing countries, both technological and societal, are much more complex and the possible solution margins are more constrained than those existing in the context where these technologies have been created. In this paper we show how Moodle can be used to improve the quality of education in developing countries and, even more important, how can be used to turn the educational system more sustainable and effective in the long-term. We describe our experience in implementing a programming course in Moodle for the Higher School of Informatics at the Université Polytechnique de Bobo-Dioulasso, in Burkina Faso (West Africa), joining efforts with local professors in designing and implementing the learning system. The case example has been designed having in mind a number of contextual problems: lack of lecturers, excessive teaching hours per lecturer, massive classes, and curricula organization and stability, among others. We finally discuss how the teaching effort is reduced, the students’ knowledge and capacity improves, and the institutional academic model can be guaranteed with the proposal. For this reason, we claim that information technologies in developing countries are a cost-effective way to guarantee the objectives originally defined in the academic curricula and, therefore, deal with the problem of the education. Wed, 22 May 2013 07:16:25 GMT http://hdl.handle.net/2117/19366 2013-05-22T07:16:25Z García Almiñana, Jordi; Somé, Michel; Ayguadé Parra, Eduard; Cabré Garcia, José M.; Casany Guerrero, María José; Frigola Bourlon, Manel; Galanis, Nikolaos; García-Cervigon Gutiérrez, Manuel; Guerrero Zapata, Manel; Muñoz Gracia, María del Pilar no Moodle, e-Learning, Education in developing countries, Programming course E-learning environments, such as Moodle, provide a technology that fosters the improvement of the educational system in developed countries, where education is traditionally performed with relatively high standards of quality. A large number of case studies and research have been conducted to demonstrate how e-learning technologies can be applied to improve both training and learning processes. However, these technologies have not been proved efficient when applied to developing countries. The challenges that must be addressed in developing countries, both technological and societal, are much more complex and the possible solution margins are more constrained than those existing in the context where these technologies have been created. In this paper we show how Moodle can be used to improve the quality of education in developing countries and, even more important, how can be used to turn the educational system more sustainable and effective in the long-term. We describe our experience in implementing a programming course in Moodle for the Higher School of Informatics at the Université Polytechnique de Bobo-Dioulasso, in Burkina Faso (West Africa), joining efforts with local professors in designing and implementing the learning system. The case example has been designed having in mind a number of contextual problems: lack of lecturers, excessive teaching hours per lecturer, massive classes, and curricula organization and stability, among others. We finally discuss how the teaching effort is reduced, the students’ knowledge and capacity improves, and the institutional academic model can be guaranteed with the proposal. For this reason, we claim that information technologies in developing countries are a cost-effective way to guarantee the objectives originally defined in the academic curricula and, therefore, deal with the problem of the education. http://hdl.handle.net/2117/18788 Title: Power management in sensing subsystem of wireless multimedia sensor networks Authors: Alaei, Mohammad; Barceló Ordinas, José María Abstract: A wireless sensor network consists of sensor nodes deployed over a geographical area for monitoring physical phenomena like temperature, humidity, vibrations, seismic events, and so on. Typically, a sensor node is a tiny device that includes three basic components: a sensing subsystem for data acquisition from the physical surrounding environment, a processing subsystem for local data processing and storage, and a wireless communication subsystem for data transmission. In addition, a power source supplies the energy needed by the device to perform the programmed task. This power source often consists of a battery with a limited energy budget. In addition, it is usually impossible or inconvenient to recharge the battery, because nodes are deployed in a hostile or unpractical environment. On the other hand, the sensor network should have a lifetime long enough to fulfill the application requirements. Accordingly, energy conservation in nodes and maximization of network lifetime are commonly recognized as a key challenge in the design and implementation of WSNs. Experimental measurements have shown that generally data transmission is very expensive in terms of energy consumption, while data processing consumes significantly less (Raghunathan et al., 2002). The energy cost of transmitting a single bit of information is approximately the same as that needed for processing a thousand operations in a typical sensor node (Pottie & Kaiser, 2000). The energy consumption of the sensing subsystem depends on the specific sensor type. In some cases of scalar sensors, it is negligible with respect to the energy consumed by the processing and, above all, the communication subsystems. In other cases, the energy expenditure for data sensing may be comparable to, or even greater (in the case of multimedia sensing) than the energy needed for data transmission. In general, energy-saving techniques focus on two subsystems: the communication subsystem (i.e., energy management is taken into account in the operations of each single node, as well as in the design of networking protocols), and the sensing subsystem (i.e., techniques are used to reduce the amount or frequency of energy-expensive samples). Mon, 15 Apr 2013 10:50:13 GMT http://hdl.handle.net/2117/18788 2013-04-15T10:50:13Z Alaei, Mohammad; Barceló Ordinas, José María no Power management, Wireless multimedia sensor networks A wireless sensor network consists of sensor nodes deployed over a geographical area for monitoring physical phenomena like temperature, humidity, vibrations, seismic events, and so on. Typically, a sensor node is a tiny device that includes three basic components: a sensing subsystem for data acquisition from the physical surrounding environment, a processing subsystem for local data processing and storage, and a wireless communication subsystem for data transmission. In addition, a power source supplies the energy needed by the device to perform the programmed task. This power source often consists of a battery with a limited energy budget. In addition, it is usually impossible or inconvenient to recharge the battery, because nodes are deployed in a hostile or unpractical environment. On the other hand, the sensor network should have a lifetime long enough to fulfill the application requirements. Accordingly, energy conservation in nodes and maximization of network lifetime are commonly recognized as a key challenge in the design and implementation of WSNs. Experimental measurements have shown that generally data transmission is very expensive in terms of energy consumption, while data processing consumes significantly less (Raghunathan et al., 2002). The energy cost of transmitting a single bit of information is approximately the same as that needed for processing a thousand operations in a typical sensor node (Pottie & Kaiser, 2000). The energy consumption of the sensing subsystem depends on the specific sensor type. In some cases of scalar sensors, it is negligible with respect to the energy consumed by the processing and, above all, the communication subsystems. In other cases, the energy expenditure for data sensing may be comparable to, or even greater (in the case of multimedia sensing) than the energy needed for data transmission. In general, energy-saving techniques focus on two subsystems: the communication subsystem (i.e., energy management is taken into account in the operations of each single node, as well as in the design of networking protocols), and the sensing subsystem (i.e., techniques are used to reduce the amount or frequency of energy-expensive samples). http://hdl.handle.net/2117/18785 Title: Chains of trust in vehicular networks: a secure points of interest dissemination strategy Authors: Antolino Rivas, David; Guerrero Zapata, Manel Abstract: This article describes a scheme which to the best of our knowledge is the first one to use user signatures to share information about Points of Interest in Vehicular Ad hoc Networks. In this scheme, users rate restaurants, hotels, etc. and sign those rates with their private key. Then, they broadcast that information and other vehicles store it for future use. When another user needs a Point of Interest recommendation he queries the system for the other users stored reviews and after he visits that Points of Interest for himself, he evaluates it and his level of trust in the reviewers with rates similar to his own increases. In the end, a user will be able to request to his vehicle information on a certain Point of Interest category and itwill respond with the recommendations made by other users, prioritizing the ones in the user’s Web of Trust.poi-Sim is the tool designed to simulate this scheme. It processes a 24 h mobility trace produced by a Multi-Agent Traffic Simulator, which realistically simulates public and private traffic over regional maps of Switzerland. The result is a Chains of Trust simulation with over 260,000 nodes, which shows that the proposed scheme performs satisfactorily in a realistic scenario. Mon, 15 Apr 2013 09:56:22 GMT http://hdl.handle.net/2117/18785 2013-04-15T09:56:22Z Antolino Rivas, David; Guerrero Zapata, Manel no Chains, POI, Reputation, Security, Trust, VANETs This article describes a scheme which to the best of our knowledge is the first one to use user signatures to share information about Points of Interest in Vehicular Ad hoc Networks. In this scheme, users rate restaurants, hotels, etc. and sign those rates with their private key. Then, they broadcast that information and other vehicles store it for future use. When another user needs a Point of Interest recommendation he queries the system for the other users stored reviews and after he visits that Points of Interest for himself, he evaluates it and his level of trust in the reviewers with rates similar to his own increases. In the end, a user will be able to request to his vehicle information on a certain Point of Interest category and itwill respond with the recommendations made by other users, prioritizing the ones in the user’s Web of Trust.poi-Sim is the tool designed to simulate this scheme. It processes a 24 h mobility trace produced by a Multi-Agent Traffic Simulator, which realistically simulates public and private traffic over regional maps of Switzerland. The result is a Chains of Trust simulation with over 260,000 nodes, which shows that the proposed scheme performs satisfactorily in a realistic scenario. http://hdl.handle.net/2117/18201 Title: RSU deployment for content dissemination and downloading in intelligent transportation systems Authors: Reineri, Massimo; Casetti, Claudio; Chiasserini, Carla-Fabiana; Fiore, Marco; Trullols Cruces, Óscar; Barceló Ordinas, José María Tue, 12 Mar 2013 10:50:20 GMT http://hdl.handle.net/2117/18201 2013-03-12T10:50:20Z Reineri, Massimo; Casetti, Claudio; Chiasserini, Carla-Fabiana; Fiore, Marco; Trullols Cruces, Óscar; Barceló Ordinas, José María no http://hdl.handle.net/2117/18025 Title: Reducing energy consumption in human-centric wireless sensor networks Authors: Meseguer Pallarès, Roc; Molina Clemente, Carlos; Ochoa, Sergio; Santos, Rodrigo Abstract: Energy consumption is a main research issue in wireless sensor networks; and particularly in those where nodes collaborate to reach a goal. This article explores the energy consumption in mobile devices participating in a human-based wireless sensor network. Specifically, the paper proposes the use of a message predictor to help detect and reduce the number of unnecessary control packets delivered by the nodes as a way to keep updated the network topology. In order to evaluate this proposal, the Optimized Link State Routing protocol was modified to add a message predictor between the routing and the network layers. Eleven simulations were performed using a particular setting. The preliminary results indicate the use of the message predictor can help reduce considerably the nodes energy consumption without affecting the routing capability of the protocol. Although these results are still preliminary, they are highly encouraging. Thu, 28 Feb 2013 17:25:11 GMT http://hdl.handle.net/2117/18025 2013-02-28T17:25:11Z Meseguer Pallarès, Roc; Molina Clemente, Carlos; Ochoa, Sergio; Santos, Rodrigo no Human-centric, wireless sensor network, energy consumption, messages prediction, opportunistic network Energy consumption is a main research issue in wireless sensor networks; and particularly in those where nodes collaborate to reach a goal. This article explores the energy consumption in mobile devices participating in a human-based wireless sensor network. Specifically, the paper proposes the use of a message predictor to help detect and reduce the number of unnecessary control packets delivered by the nodes as a way to keep updated the network topology. In order to evaluate this proposal, the Optimized Link State Routing protocol was modified to add a message predictor between the routing and the network layers. Eleven simulations were performed using a particular setting. The preliminary results indicate the use of the message predictor can help reduce considerably the nodes energy consumption without affecting the routing capability of the protocol. Although these results are still preliminary, they are highly encouraging. http://hdl.handle.net/2117/18011 Title: Las comunicaciones móviles en los edificios inteligentes Authors: Reyes Muñoz, María Angélica Abstract: Este trabajo presenta una plataforma de red móvil aplicada a los entornos de edificios inteligentes. En primer lugar, los edificios inteligentes han sido definidos como “aquellos que utilizan la tecnología computacional para gestionar de manera autónoma todos los servicios que ofrece un entorno de un edificio tales como optimizar el confort del usuario, el consumo de energía y la seguridad” [Callaghan 00].Desde el punto de vista de las telecomunicaciones específicamente desde el punto de vista de las comunicaciones móviles es muy importante para los edificios inteligentes considerar la comunicación entre sistemas autónomos inteligentes, dispositivos personales inteligentes, gestión de sistemas de información, dispositivos móviles, etc. Wed, 27 Feb 2013 16:31:39 GMT http://hdl.handle.net/2117/18011 2013-02-27T16:31:39Z Reyes Muñoz, María Angélica no Edificios Inteligentes, Redes locales, Comunicaciones móviles, Gestión de red Este trabajo presenta una plataforma de red móvil aplicada a los entornos de edificios inteligentes. En primer lugar, los edificios inteligentes han sido definidos como “aquellos que utilizan la tecnología computacional para gestionar de manera autónoma todos los servicios que ofrece un entorno de un edificio tales como optimizar el confort del usuario, el consumo de energía y la seguridad” [Callaghan 00].Desde el punto de vista de las telecomunicaciones específicamente desde el punto de vista de las comunicaciones móviles es muy importante para los edificios inteligentes considerar la comunicación entre sistemas autónomos inteligentes, dispositivos personales inteligentes, gestión de sistemas de información, dispositivos móviles, etc. http://hdl.handle.net/2117/16643 Title: Should next generation wireless mesh networks consider dynamic channel access? Authors: Amiri Nezhad, Maryam; Bellalta, Boris; Guerrero Zapata, Manel; Cerdà Alabern, Llorenç Abstract: In today’s computer architectures, many scientific applications are considered to be memory bound. The memory wall, i.e. the large disparity between a processor’s speed and the required time to access off-chip memory, is a yet-to-be-solved problem that can greatly reduce performance and make us underutilise the processors capabilities. Many different approaches have been proposed to tackle this problem, such as the addition of a large cache hierarchy, multithreading or speculative data prefetching. Most of these approaches rely on the prediction of the application’s future behaviour, something that should not be necessary as this information is known by the programmer and is located in the application itself. Instead of designing hardware that attempts to guess the future, the goal should be to provide the programmer with the hardware support required to decide when the data is transferred and where is it transferred to. With this goal in mind, we introduce the Data Transfer Engine, a runtime-assisted, software prefetcher that exploits the information provided by the programmer in order to place data in the cache hierarchy close to the processor that will make use of it. The DTE can not only significantly reduce stall time due to cache misses but, more importantly, it allows us to design new computer architectures that are able to tolerate very high memory latencies. Thu, 04 Oct 2012 11:47:56 GMT http://hdl.handle.net/2117/16643 2012-10-04T11:47:56Z Amiri Nezhad, Maryam; Bellalta, Boris; Guerrero Zapata, Manel; Cerdà Alabern, Llorenç no In today’s computer architectures, many scientific applications are considered to be memory bound. The memory wall, i.e. the large disparity between a processor’s speed and the required time to access off-chip memory, is a yet-to-be-solved problem that can greatly reduce performance and make us underutilise the processors capabilities. Many different approaches have been proposed to tackle this problem, such as the addition of a large cache hierarchy, multithreading or speculative data prefetching. Most of these approaches rely on the prediction of the application’s future behaviour, something that should not be necessary as this information is known by the programmer and is located in the application itself. Instead of designing hardware that attempts to guess the future, the goal should be to provide the programmer with the hardware support required to decide when the data is transferred and where is it transferred to. With this goal in mind, we introduce the Data Transfer Engine, a runtime-assisted, software prefetcher that exploits the information provided by the programmer in order to place data in the cache hierarchy close to the processor that will make use of it. The DTE can not only significantly reduce stall time due to cache misses but, more importantly, it allows us to design new computer architectures that are able to tolerate very high memory latencies. http://hdl.handle.net/2117/16006 Title: Impact of the infrastructure in mobile opportunistic networks Authors: Trullols Cruces, Óscar; Morillo Pozo, Julián David; Barceló Ordinas, José María Abstract: Epidemic modeling has been used to analyze many disciplines such as biology, ecology and medicine. In the last years, it also has been applied to networking paradigms such as social networks, virus spreading in Internet and lastly to opportunistic networking in mobile networks. In this paper we revise some of the facts of epidemic modeling in mobile networks and use these models to analyze the impact of adding infrastructure to sparse opportunistic mobile networks. We show how the position in which infrastructure is placed takes an important impact in the dissemination delay. Description: Invited paper Sun, 10 Jun 2012 13:02:26 GMT http://hdl.handle.net/2117/16006 2012-06-10T13:02:26Z Trullols Cruces, Óscar; Morillo Pozo, Julián David; Barceló Ordinas, José María no Epidemic modeling has been used to analyze many disciplines such as biology, ecology and medicine. In the last years, it also has been applied to networking paradigms such as social networks, virus spreading in Internet and lastly to opportunistic networking in mobile networks. In this paper we revise some of the facts of epidemic modeling in mobile networks and use these models to analyze the impact of adding infrastructure to sparse opportunistic mobile networks. We show how the position in which infrastructure is placed takes an important impact in the dissemination delay.