Browsing by Author "Monteiro, J. M."
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- A distributed load scheduling mechanism for micro gridsPublication . Monteiro, J. M.; Eduardo, J.; Cardoso, Pedro J. S.; Semiao, J.Several protocols have recently been defined for smart grids that enable the communication between electric devices and energy management systems. While these protocols and architectures can already be applied in different fields of micro grids, it is still not clear how the distributed resources and constraints of such electrical grids can be managed in an optimum way. In order to achieve a reduction in electricity costs and maximizing investments made in renewable sources, an optimization mechanism should be used to perform load scheduling, considering different variables such as forecasted power generation curve from renewable sources, different tariffs' rates, electric circuit constraints, user restrictions and correspondent comfort levels. Given these considerations, this work defines and evaluates a distributed micro grid resource management architecture and protocol which is able to optimize load scheduling while considering all the mentioned restrictions and parameters. The proposed architecture was implemented on a multi-agent simulator and the performed tests show that significant reductions in electricity cost can be achieved using this methodology. © 2014 IEEE.
- An efficient and robust content delivery solution for IEEE 802.11p vehicular environmentsPublication . Calafate, C. T.; Fortino, G.; Fritsch, S.; Monteiro, J. M.; Cano, J. C.; Manzoni, P.Vehicular networking is a new field that is expected to be widely adopted in the near future. One of the key applications inherent to this novel communications paradigm is content delivery to on-board users. In this paper we focus specifically on the design of a robust and efficient broadcast-based content delivery system. In order to reduce the content delivery time to a minimum, we first optimize performance by seeking the optimal packet size for content delivery. This goal is achieved by combining analytical and simulation results, and considering both static and mobile receivers at different distances from the transmitter. Moreover, we develop a full architecture that integrates the FLUTE protocol with different Forward Error Correction (FEC) schemes to achieve efficient content distribution. Through real experiments in a vehicular testbed we demonstrate that Raptor codes are the best option among the different FEC schemes available. In addition, as vehicle speed and/or distance from the broadcasting antenna increases, performance results highlight that adopting efficient FEC schemes becomes mandatory to achieve efficient and reliable data content delivery. (C) 2011 Elsevier Ltd. All rights reserved.
- Ant colony optimization routing mechanisms with bandwidth sensingPublication . Mapisse, J. M.; Cardoso, Pedro J. S.; Monteiro, J. M.The study and understanding of the social behavior of insects has contributed to the definition of some algorithms that are capable of solving several types of optimization problems. In 1997 Di Caro and Dorigo developed the first routing algorithm for wired networks, called AntNet, using an approach which was inspired in the behavior of ant colonies. At each node, AntNet, similar to others Ant Colony Optimization (ACO) based algorithms, forward ants based in the amount of pheromones present in the links and in response to the node's queue lengths. In this paper, an adaptation of the e-DANTE algorithm for discrete problems, as an IP based routing mechanism, was implemented. We also propose the inclusion of a new parameter for the computation of paths for both the AntNet and the newly proposed algorithm: the available bandwith. Those methods were tested in ns-2 using two dense network architectures and their efficiency is compared with the original AntNet and a Link-State routing algorithm, when considering the transmission of competing traffic flows between distinct nodes. © 2011 IEEE.
- Assessing the best strategy to improve the stability of scalable video transmission in MANETsPublication . Chaparro, P. A.; Alcober, J.; Monteiro, J. M.; Calafate, C. T.; Cano, J. C.; Manzoni, P.Mobile Ad Hoc Networks (MANETs) have been an important research topic for the last years, playing a crucial role within the fast growing sector of mobile communications. At the same time, video applications over mobile devices are becoming widely used by nowadays mobile clients, where the quality in the transmission of such contents will determine the success of these applications in the future. Therefore, it is mandatory to find the best strategies to guarantee a good Quality of Service (QoS) to the end-user. In this work we present a set of novel strategies to improve the performance of video transmission over MANETs. These new strategies are based on distributed admission control protocols which has proved to be helpful at achieving an efficient video transmission system. Experimental results show that, when adopting the new strategies to determine the optimal number of layers to transmit, we can achieve better results compared to other existent approaches in terms of idle time periods, fairness and delay. © 2011 IEEE.
- BitTorrent based transmission of real-time scalable video over P2P networksPublication . Rodrigues, P. L.; Monteiro, J. M.The number of software applications available on the Internet for distributing video streams in real time over P2P networks has grown quickly in the last two years. Typical this kind of distribution is made by television channel broadcasters which try to make their content globally available, using viewer's resources to support a large scale distribution of video without incurring in incremental costs. However, the lack of adaptation in video quality, combined with the lack of a standard protocol for this kind of multimedia distribution has driven content providers to basically ignore it as a solution for video delivery over the Internet. While the scalable extension of the H.264 encoding (H.264/SVC) can be used to support terminal and network heterogeneity, it is not clear how it can be integrated in a P2P overlay to form a large scale and real time distribution. In this paper, we start by defining a solution that combines the most popular P2P file-sharing protocol, the Bit Torrent, with the H.264/SVC encoding for a real-time video content delivery. Using this solution we then evaluate the effect of several parameters in the quality received by peers.
- Efficient content pushing in IEEE 802.11p vehicular environmentsPublication . Fritsch, S.; Calafate, C. T.; Monteiro, J. M.; Cano, J. C.; Manzoni, P.Vehicular networking is a new field that is expected to be widely adopted in the near future. One of the key applications inherent to this novel communications paradigm is content delivery to on-board users. In this paper we focus specifically on broadcast-based content delivery. We propose a content delivery scheme that is optimized for performance in order to improve the maximum amount of data than can be delivered, while also reducing delivery time to a minimum. With this goal our study combines both analytical and simulation results to determine the optimal packet size for content delivery so as to achieve the maximum throughput possible at different distances, and considering both static and mobile receivers. Experimental results show that our optimizations provide efficient delivery of multimedia contents for distances up to 200 meters when relying on IEEE 802.lip based broadcasting. Copyright © 2010 ACM.
- Evaluation of the H.264 scalable video coding in error prone IP networksPublication . Monteiro, J. M.; Calafate, C. T.; Nunes, M. S.The Joint Video Team, composed by the ISO/IEC Moving Picture Experts Group (MPEG) and the ITU-T Video Coding Experts Group (VCEG), has standardized a scalable extension of the H.264/AVC video coding standard called Scalable Video Coding (SVC). H.264/SVC provides scalable video streams which are composed by a base layer and one or more enhancement layers. Enhancement layers may improve the temporal, the spatial or the signal-to-noise ratio resolutions of the content represented by the lower layers. One of the applications, of this standard is related to video transmission in both wired and wireless communication systems, and it is therefore important to analyze in which way packet losses contribute to the degradation of quality, and which mechanisms could be used to improve that quality. This paper provides an analysis and evaluation of H.264/SVC in error prone environments, quantifying the degradation caused by packet losses in the decoded video. It also proposes and analyzes the consequences of QoS-based discarding of packets through different marking solutions.
- Evaluation of the human factor in the scheduling of smart appliances in smart gridsPublication . Monteiro, J. M.; Cardoso, Pedro J. S.; Serra, R.; Fernandes, L.Recently there has been an increase of interest in implementing a new set of home appliances, known as Smart Appliances that integrate Information Technologies, the Internet of Things and the ability of communicating with other devices. While Smart Appliances are characterized as an important milestone on the path to the Smart Grid, by being able to automatically schedule their loads according to a tariff or reflecting the power that is generated using renewable sources, there is not a clear understanding on the impact that the behavior of such devices will have in the comfort levels of users, when they shift their working periods to earlier, or later than, a preset time. Given these considerations, in this work we analyse the results of an assessment survey carried out to a group of Home Appliance users regarding their habits when dealing with these machines and the subjective impact in quality caused by either finishing its programs before or after the time limit set by the user. The results of this work are expected to be used as input for the evaluation of load scheduling algorithms running in energy management systems. © 2014 Springer International Publishing.
- LifeSpeeder: a web and mobile platform for events locationPublication . Cardoso, Pedro J. S.; Monteiro, J. M.; Dos Santos, J.; Baeza, N.; Tarazona, S.The use of smartphones and tablets as become almost banal in these days. Smartphones, besides serving their main purpose of making and receiving calls, come to be one of the main equipments to obtain information from the Internet, using the commonly installed browsers or through the use of dedicated applications. Furthermore, several other devices are also very frequent to the majority of the modern smartphones and tablets in the market (e.g., GPS - Global Positioning System). This devices give the current systems a very high potential of usage. One example of applicability, comes from the wish to find and navigate to events or activities which are or will soon be occurring near the user. The LifeSpeeder platform is one of the first applications in the mobile equipment market of applications which take into consideration exactly what we have just outlined, i.e., a mobile and desktop application which allows the users to locate events according with their preferences and to get help navigating to them. In this paper we briefly describe the LifeSpeeder's front and back-end. © 2014 Springer International Publishing.
- Peer-to-peer video streamingPublication . Monteiro, J. M.; Cruz, R. S.; Patrikakis, C. Z.; Papaoulakis, N. C.; Calafate, C. T.; Nunes, M. S.The Internet as a video distribution medium has seen a tremendous growth in recent years. Currently, the transmission of major live events and TV channels over the Internet can easily reach hundreds or millions of users trying to receive the same content using very distinct receiver terminals, placing both scalability and heterogeneity challenges to content and network providers. In private and well-managed Internet Protocol (IP) networks these types of distributions are supported by specially designed architectures, complemented with IP Multicast protocols and Quality of Service (QoS) solutions. However, the Best-Effort and Unicast nature of the Internet requires the introduction of a new set of protocols and related architectures to support the distribution of these contents. In the field of file and non-real time content distributions this has led to the creation and development of several Peer-to-Peer protocols that have experienced great success in recent years. This chapter presents the current research and developments in Peer-to-Peer video streaming over the Internet. A special focus is made on peer protocols, associated architectures and video coding techniques. The authors also review and describe current Peer-to-Peer streaming solutions. © 2013, IGI Global.