Browsing by Author "Calafate, C. T."
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- 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.
- 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.
- 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.
- 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.
- Robust multipoint and multi-layered transmission of H.264/SVC with Raptor codesPublication . Monteiro, J. M.; Calafate, C. T.; Nunes, M. S.The scalable extension of the H.264 Advanced Video Coding (AVC) standard called Scalable Video Coding (SVC), or 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 video coding standard is related to point-to-multipoint video distributions in both wired and wireless communication systems, where packet losses contribute to the degradation of the user's Quality of Experience. Designed for the transmission of data over Binary Erasure Channels (BEC), Raptor codes are a Forward Error Correction (FEC) mechanism that is gaining popularity for Internet Protocol Television (IPTV) applications due to their small decoding complexity and reduced overhead. This paper evaluates the quality enhancements introduced by the integration of several H.264/SVC layers with a Raptor coding protection scheme. Our goal is to improve the distribution of video over loss prone networks in terms of rate-distortion performance by assessing several alternative packetization options and protection schemes.
- Supporting scalable video transmission in MANETs through distributed admission control mechanismsPublication . Chaparro, P. A.; Alcober, J.; Monteiro, J.; Calafate, C. T.; Cano, J. C.; Manzoni, P.Emerging multimedia applications over mobile devices are becoming very popular, especially over infrastructure wireless networks such as cellular and WLANs. However, providing this kind of services over infrastructureless networks like ad hoc networks presents many additional problems. One of these problems is how to share resources fairly among the users involved. In this article we propose a QoS framework supporting scalable video streaming in mobile ad hoc networks based on distributed admission control and video traffic awareness. Our framework promotes fairness between video flows in terms of resource consumption. It also guarantees a significant reduction of the idle times experienced by users during periods of network saturation, thus increasing the video playout time in reception for all users. Using the IEEE 802.11e MAC technology as our basis for traffic differentiation, our framework, called DACMESV (Distributed Admission Control for MANET's - Scalable Video), relies on a periodic probing process to measure the available bandwidth and the end-to-end delay on the path. DACME-SV adopts a cross-layer approach to determine the optimum number of video layers to transmit at any given time, thus avoiding network congestion and guaranteeing an acceptable video quality at the destination. Experimental results show that idle time periods are substantially decreased, while exhibiting a good overall performance in terms of throughput and delay. © 2010 IEEE.