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Publicações

Publicações por CTM

2011

Assessment of noise impact on UWB signals in R-EAM based optical links

Autores
Pessoa, LM; Coelho, D; Oliveira, JMB; Castro, JCS; Salgado, HM;

Publicação
2011 IEEE Avionics, Fiber- Optics and Photonics Technology Conference, AVFOP 2011

Abstract
The measured characteristics of a R-EAM, acting as a base station, were used to assess the performance of a radio-over-fiber uplink for possible provision of wireless services within aircrafts. The specific case of deployment of UWB signals was analyzed. We conclude that laser RIN is a performance degradation factor that imposes a limit on the achievable SNR, especially for a zero biased modulator. A laser RIN of -160 dB/Hz would be required in order to avoid the RIN limitation. Additionally, in this case the performance becomes limited by shot noise. Although the zero bias case seems limitative, the R-EAM can be optimum biased using a small battery, which can last for several months, allowing the base-station to operate as a passive device. © 2011 IEEE.

2011

Compact Printed C-shaped Monopole Antenna with Chip Inductor

Autores
Luo, Q; Salgado, HM; Pereira, JR;

Publicação
2011 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (APSURSI)

Abstract
This paper presents one compact printed monopole antenna with one chip inductor embedded on the radiation elements. By introducing the chip inductor, the resonant frequency of the original antenna can be decreased by more than 37% while there is no significant influence on its radiation characteristics including radiation efficiency and antenna gain. Meanwhile, after adding the chip inductor, the higher mode of the original antenna can also be brought down to a lower frequency, which makes the proposed antenna resonate at the dual frequency band and simultaneously have a compact size. This antenna has a C-shaped geometry and its parameters including the location of the chip inductor are optimized by doing parametrical studies in Ansoft HFSS. The measurement and simulation results show that the proposed C-shaped monopole antenna can operate at 2.55-2.65GHz and 5.1-5.3GHz with peak gain of 2.2 and 4.7dB, respectively. Moreover, according to the simulation results, the radiation efficiency of this antenna at both bands is around 90%.

2011

Cooperative clustered architecture and resource reservation for OBS networks

Autores
Haq, IU; Salgado, HM; Castro, JCS;

Publicação
International Congress on Ultra Modern Telecommunications and Control Systems and Workshops

Abstract
Resource contention is a major concern in Optical Burst Switching networks that leads to relatively high burst loss probability. This article presents a clustered architecture for OBS networks, called Cooperative Clustered Optical Burst Switching (C2OBS) network architecture. In this architecture, the network is divided in overlapping zones/clusters with a zone/cluster head having the knowledge of available resources within the zone called Zonal Base (ZB) and maintains a short resource usage history called Short History Base (SHB). A resource reservation strategy for the proposed Cooperative Clustered OBS network architecture (C2OBS-RR) is also presented which is centralized within the zone and distributed in the overall network, for combining the benefits of both the centralized and the distributed resource reservation schemes. This novel approach uses the local state of the resource availability within the zone (ZB) so that the bursts originating at the ingress nodes in the same part of network having been assigned the same wavelength, can be assigned different time offsets. This will proactively reduce the probability of contention at the intermediate nodes within a zone and is expected to significantly reduce the overall network burst loss probability. For illustration purpose, the proposed C2OBS architecture has been applied to the European Optical Network. © 2011 HTE.

2011

Advanced delivery of sensitive multimedia content for better serving user expectations in Virtual Collaboration applications

Autores
Andrade, MT; Dogan, S; Carreras, A; Barbosa, V; Kodikara Arachchi, H; Delgado, J; Kondoz, AM;

Publicação
Multimedia Tools and Applications

Abstract
A major challenge when accessing protected multimedia content in heterogeneous usage environments is the ability to provide acceptable levels of quality of experience to all involving users. Additionally, different levels of protection should be possible to be addressed when manipulating the content towards the quality of experience maximization. This paper describes the use of a context-aware and Digital Rights Management (DRM)-enabled content adaptation platform towards meeting these challenges. The platform was conceived to deliver advanced content adaptation within different application scenarios, among which Virtual Collaboration (VC) was central. Descriptions of use cases implemented by the platform in heterogeneous VC environments are provided. Conducted experiments have highlighted the benefits to users when compared to an operation without the platform. Results of different adaptations suitable to sensed context conditions are also provided and analyzed. A brief description of the platform functionality is included together with pointers to additional information. © 2011 Springer Science+Business Media, LLC.

2011

Exploring semantic relationships across internet resources

Autores
Castro, H; Andrade, MT; Almeida, F; Chiariglione, L; Tropea, G; Melazzi, NB; Mousas, AS; Kaklamani, DI;

Publicação
Proceedings of the 2011 7th International Conference on Next Generation Web Services Practices, NWeSP 2011

Abstract
As the social character of the Web grows stronger, online multimedia resources become more tangled, exhibiting multiple and complex relationships. Often, these relationships are not easily spotted by search engines because they are not explicit. Still, when searching for content, users would certainly appreciate to receive results indicating all resources that are somehow related to their topic of interest without having to explicitly request for it. In spite of this trend, current technology for declaring and describing resources on the Internet as well as their inter-relationships is very much fragmented and the most commonly used standards, such as HTML, do not offer adequate functionality. While the goal of the MPEG-21 standard is to provide an all encompassing, universal and standard way to perform the declaration of digital resources, the work being developed in the IST CONVERGENCE project has shown that this standard, (specifically its part 3, Digital Item Identification), also has a limited ability to specify relationships between digital resources. This document presents a proposed extension to MPEG-21 Digital Item Identification, which enables it to support a uniform, semantically expressive and precise specification of the relationships between MPEG-21 digital items, rendering it a much more effective tool for a ubiquitous representation and interconnection of digital resources. © 2011 IEEE.

2011

A content-centric, publish-subscribe architecture delivering mobile context-aware health services

Autores
Gkonis, PK; Patrikakis, CZ; Anadiotis, AC; Kaklamani, DI; Andrade, MT; Detti, A; Tropea, G; Melazzi, NB;

Publicação
2011 Future Network & Mobile Summit, Warsaw, Poland, June 15-17, 2011

Abstract
The goal of this paper is to report on the design of a novel content-centric future Internet platform that can support added value services incorporating mobility, context awareness and enhanced security and privacy. We present the proposed platform together with a use case study, dealing with the provision of added-value health services, consisting in the safe and accurate management of medicine prescriptions. Both the design of the platform and the use case are the results of work performed in the context of the European Research project Convergence [1]. © 2011 IIMC.

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