Eventos Passados
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UTM Lab meeting: Network Monitoring
Network monitoring is currently considered one of the main study areas in network management. Networks are growing very fast and users demand for new services (e.g. VoIP and VideoConference) with Quality of Service. Moreover, new business models demand for complex tariffs based on usage-based accounting or hybrid ones (mixture of event based and time based). Security is also becoming the main concern for users, regarding aspects as confidentiality, privacy or authenticity.
UTM Lab Meeting: MOSAICA P2P Distributed Content Management System
MOSAICA addresses the presentation and discovery of just about any cultural heritage and that will allow multiple groups of interest to develop innovative and creative user experience. It´s a European project and INESC is responsible for the implementation of a Peer-to-Peer(P2P) Distributed Content Management System (DCMS) that will store heritage contents with metadata associated for semantic querying. This presentation will address the decentralized storage mechanism, overall architecture of the P2P DCMS, the adopted P2P technologies (JXTA and Bittorrent), the SOAP interface implemented in each peer for integration with a larger Service Oriented Architecture (SOA), mechanisms for high availability of contents (super seeding activated through RSS feeds), integration with MOSAICA semantic layer, current implementation state and future developments.
UTM Lab Meeting: An Adaptive Cross-Layer Adaptation Framework for Media delivery over Heterogeneous Networks
Streaming applications in distributed systems are facing different problems at different layers of the Open Systems Interconnection (OSI) stack. Requirements regarding bandwidth, delay, jitter, video and terminal characteristics (temporal and space scalability) and user's preferences come together to influence the architecture of multimedia delivery services with particular quality-of-services (QoS). However the Internet architecture is only capable to support best-effort services, with varying network conditions during multimedia delivery. Currently, a multitude of protection and adaptation strategies exist at different OSI layers, however these strategies are independent of each other. To improve the perceived media quality delivered to end users over heterogeneous networks, QoS strategies should combine mechanisms at different layers, including application layer, transport layer and data link layer. In this paper, we formalize the problem of multimedia streaming application over heterogeneous networks, then discuss the challenges and finally present a putative architecture.
UTM Lab Meeting: Mixing Packets: Pros and Cons of Network Coding
By allowing intermediate nodes in mobile ad-hoc and sensor networks to perform non-trivial operations on packets, thus mixing data from multiple streams, network coding breaks with the ruling store and forward networking paradigm and opens a myriad of challenging questions. Following an overview of the theory and practice of emerging network coding protocols, we provide a taxonomy of their security vulnerabilities, which highlights the differences between attack scenarios in which network coding is particularly vulnerable and other relevant cases in which the intrinsic properties of network coding allow for stronger and more efficient security solutions than classical routing. Furthermore, we give practical examples where network coding can be combined with classical cryptography both for secure communication and secret key distribution. Throughout the talk we shall identify a number of research challenges deemed relevant towards the applicability of network coding in contemporary communication networks. Joint work with Rui Costa, Luisa Lima, Paulo Oliveira, João Paulo Vilela, and Muriel Médard (MIT).
UTM Lab Meeting: A Protocol for Event Distribution in Next-Generation Dynamic Networks
With the increasing number of devices carried by users and the emergence of more dynamic network scenarios, new solutions have to be developed to support ubiquitous communications. The need for dynamic and transparent auto-configuration and adaptation of applications, devices and networks of devices to a wide variety of events is one of the major challenges. This paper presents a protocol to be used with notification systems, to support the registration, subscription and distribution of generic events among heterogeneous and independent entities, thus addressing the requirements of future communication scenarios.
UTM Lab Meeting: Multichannel Audio Coding for Wave Field Synthesis
In this talk, I will present a non-parametric method for compressing multichannel audio data for reproduction through Wave Field Synthesis.
UTM Lab Meeting: Algorithms for DSP implementation in Coherent Optical Systems
Coherent optical communications have gained renewed interest due to the availability of high speed digital signal processing, low priced components as well as partly relaxed receiver requirements at high data rates. When the outputs of a coherent homodyne receiver are sampled at the Nyquist rate, the digitized waveform contains full information of the electric field, preserving the amplitude, phase and polarization from the optical domain to the electrical domain, enabling new potential of multi-level signaling (M-ary PSK and M-ary QAM modulation), as well as the possibility of exploring polarization multiplexing. Additionally, it enables quasi-exact compensation of linear transmission impairments such as Chromatic Dispersion (CD) and Polarization Mode Dispersion (PMD) by a linear filter. Digital Signal Processors (DSP) has been evolving as a practical solution for robust optical long-haul transmission, and it is expected that data converters will be able to satisfy the required high sampling rates in the near future. We will present the computer simulations results of algorithms for compensation of CD and PMD in a coherent optical system exploiting polarization multiplexing. The benefits of combining a phase estimation algorithm with a decision directed least-mean-square equalizer in a feedback configuration will be shown.
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