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Publications

2010

Improving P2P video streaming in wireless mesh networks

Authors
Salta, N; Morla, R; Ricardo, M;

Publication
The 9th IFIP Annual Mediterranean Ad Hoc Networking Workshop, Med-Hoc-Net 2010, Juan Les Pins, France, 23-25 June, 2010

Abstract
P2P Video Streaming has become a reliable and efficient solution for distributing video on the Internet. Similarly to regular P2P file-sharing, all the participating nodes exchange information. Wireless Mesh Networks, in turn, can be seen as a cost-effective solution to extend Internet access networks. In this paper we propose improvements to P2P Video Streaming. These improvements can provide gains in scenarios where the service is deployed over Wireless Mesh Networks and the nodes are simultaneously peers and packet forwarders. By using cross-layer interactions between application and network layers, we show that the proposed improvements reduce substantially the amount of traffic in the network. ©2010 IEEE.

2010

DEVELOPMENT OF AN WHEELED CLIMBING ROBOT FOR METALLIC SURFACES WITH PERMANENT MAGNETIC SYSTEM DYNAMIC ADJUSTMENT

Authors
Oliveira, ALC; Silva, MF; Barbosa, RS;

Publication
EMERGING TRENDS IN MOBILE ROBOTICS

Abstract
This paper presents the mechanical construction of a climbing robot with wheeled locomotion and adhesion through permanent magnets. This machine is intended to be used in the inspection of different types of ferromagnetic structures, in order to, for instance, detect weaknesses due to corrosion, particularly in fuel tanks, ship hulls, etc. The vehicle will have a semi-autonomous behaviour, allowing a remote inspection process controlled by a technician, this way reducing the risks associated with the inspection of tall structures and ATEX places. The distinguishing characteristic of this robot is its dynamic adjustment system of the permanent magnets in order to assure the machine adhesion to the surfaces, even when crossing irregular and curved surfaces.

2010

On the Expressiveness and Trade-Offs of Large Scale Tuple Stores

Authors
Vilaca, R; Cruz, F; Oliveira, R;

Publication
ON THE MOVE TO MEANINGFUL INTERNET SYSTEMS: OTM 2010, PT II

Abstract
Massive-scale distributed computing is a challenge at our doorstep. The current exponential growth of data calls for massive-scale capabilities of storage and processing. This is being acknowledged by several major Internet players embracing the cloud computing model and offering first generation distributed tuple stores. Having all started from similar requirements, these systems ended up providing a similar service: A simple tuple store interface, that allows applications to insert, query, and remove individual elements. Furthermore, while availability is commonly assumed to be sustained by the massive scale itself, data consistency and freshness is usually severely hindered. By doing so, these services focus on a specific narrow trade-off between consistency, availability, performance, scale, and migration cost, that is much less attractive to common business needs. In this paper we introduce Data Droplets, a novel tuple store that shifts the current trade-off towards the needs of common business users, providing additional consistency guarantees and higher level data processing primitives smoothing the migration path for existing applications. We present a detailed comparison between Data Droplets and existing systems regarding their data model, architecture and trade-offs. Preliminary results of the system's performance under a realistic workload are also presented.

2010

Evaluating the Adaptation of Multimedia Services Using a Constraints-Based Approach

Authors
Oliveira, JM; Carrapatoso, EM;

Publication
MOBILE MULTIMEDIA PROCESSING: FUNDAMENTALS, METHODS, AND APPLICATIONS

Abstract
This chapter presents a proposal to solve the problem of the adaptation of multimedia services in mobile contexts. The chapter combines context-awareness techniques with user interface modeling to dynamically adapt telecommunications services to user resources, in terms of terminal and network conditions. The solution is mainly characterized by the approach used for resolving the existing dependencies among user interface variables, which is based on the constraints theory. The experiments and tests carried out with these techniques demonstrate a general improvement of the adaptation of multimedia services in mobile environments, in comparison to systems that do not dynamically integrate the user context information in the adaptation process.

2010

WiMetroNet A Scalable Wireless Network for Metropolitan Transports

Authors
Ricardo, M; Carneiro, G; Fortuna, P; Abrantes, F; Dias, J;

Publication
Sixth Advanced International Conference on Telecommunications, AICT 2010, 9-15 May 2010, Barcelona, Spain

Abstract
This paper addresses Wireless Networks for Metropolitan Transports (WNMT), a class of moving or vehicle-to-infrastructure networks that may be used by public transportation systems to provide broadband access to their vehicles, stops, and passengers. We propose the WiMetroNet, a WNMT that is auto-configurable and scalable. It is based on a new Ad hoc routing protocol, the Wireless Metropolitan Routing Protocol (WMRP), which, coupled with data plane optimizations, was designed to be scalable to thousands of nodes. © 2010 IEEE.

2010

Long-Period Grating Fiber Sensor With In Situ Optical Source for Remote Sensing

Authors
Viegas, D; Carvalho, JP; Coelho, L; Santos, JL; Araujo, FM; Frazao, O;

Publication
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
A concept of long-period-based optical fiber sensors, with broadband light illumination generated just after the sensing structure, is presented in this work. This new approach allows the interrogation in transmission of the sensing head while integrated in a reflective configuration, which means the long-period grating (LPG) sensor is seen in transmission by the optical source but in reflection by the measurement system. Also, it is shown that with this illumination layout the optical power balance is more favorable when compared with the standard configurations, allowing better sensor performances, particularly when the sensing head is located far away from the photodetection and processing unit. This is demonstrated for the case of the LPG structure applied to measure strain and using ratiometric interrogation based on the readout of the optical power reflected by two fiber Bragg gratings spectrally located in each side of the LPG resonance.

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