Neves F.,University of Trás os Montes e Alto Douro |
Neves F.,Polytechnic Institute of Leiria |
Neves F.,Telecommunications Institute of Portugal |
Cardeal S.,University of Trás os Montes e Alto Douro |
And 5 more authors.
EUROCON 2011 - International Conference on Computer as a Tool - Joint with Conftele 2011 | Year: 2011
This paper presents a no-reference model for monitoring the voice quality experienced by users in VoIP services. The proposed model is based on the E-Model, which is adapted from Recommendation ITU-T G.107 for this purpose. A calibration function was determined for relevant codecs under different packet loss conditions. Extensive field testing was carried out to validate the proposed model at PT Inovação Labs (Portugal). The results show that the mean opinion score (MOS) obtained from the proposed model match class C2 of conformance tests defined in ITU-T Recommendation P.564. The QoE model described in this paper was implemented in a VoIP QoE probe and is currently fully operational at Portugal Telecom. © 2011 IEEE.
Vochin M.,Polytechnic University of Bucharest |
Borcoci E.,Polytechnic University of Bucharest |
Carneiro G.,Institute Engineering
UPB Scientific Bulletin, Series C: Electrical Engineering | Year: 2015
ALICANTE is a FP7 research project proposing an architecture in which, the CAN layer offers enhanced content-aware connectivity services to the upper layers for the efficient transport of media services. ALICANTE integrates, in an efficient way, and in the same tree, three separate transport mechanisms for multicast traffic IP multicast, inter-domain tunnelling, and peer-to-peer-with QoS and dynamic adaptation support, which is something unique, not found in related solutions. It also allows independent domains to collaborate in forming a single inter-domain tree, for incremental deployment. While it uses legacy QoS technologies, such as core IP/MPLS/Diffserv in the core routers, it proposes a new edge router, called MANE (Media Aware Network Element), CAN capable. This paper evaluates a modular MANE implementation solution used to implement flow classification, MPLS encapsulation and decapsulation, separation between VCANs, and QoS enforcement with Linux TC (traffic control) mechanism. Based on data plane performance measurements, it is shown that the implementation imposes minor overheads over existing routing infrastructure and scalability is achievable.
Camanho P.P.,University of Porto |
Ercin G.H.,Institute Engineering |
Catalanotti G.,University of Porto |
Mahdi S.,Airbus |
Composites Part A: Applied Science and Manufacturing | Year: 2012
A new model based on finite fracture mechanics is proposed to predict the open-hole tensile strength of composite laminates. Failure is predicted when both stress-based and energy-based criteria are satisfied. The material properties required by the model are the ply elastic properties, and the laminate unnotched strength and fracture toughness. No empirical adjusting parameters are required. Using experimental data obtained in quasi-isotropic carbon-epoxy laminates it is concluded that the model predictions are very accurate, resulting in improvements over the traditional strength prediction methods. It also is shown that the proposed finite fracture mechanics model can be used to predict the brittleness of different combinations of materials and geometries. © 2012 Elsevier Ltd. All rights reserved.