Percorrer por autor "Neves, Filipe"
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- ArQoS®: System to monitor QoS/QoE in VoIPPublication . S. Cardeal; Neves, Filipe; Soares, S.; Tavares, F.; Assunção, PedroThe evolution of telecommunications technology from circuit to packet switching, in which the Internet is the great paradigm, offers nowadays more flexibility in services and higher efficiency in the transport infrastructure that was not experienced before. As consequence, several new services have emerged. Among them, Voice over IP (VoIP) is, indubitably, one of the most popular, mainly because it allows anyone to make low cost voice calls, making it a very attractive service. This is perhaps one of the main factors responsible for the fast development of VoIP technology. However, IP networks were not designed for services with real time requirements and factors like delay, jitter, codec distortions and packet loss lead to degradations that directly influence de VoIP user experience. The quality experienced by these users is highly dependent on network conditions and also on the subjective experience perceived by them. Thus, new challenges have brought with this evolution of telecommunications networks. In order to meet the assigned Service Level Agreement (SLA's), service providers around the world need to monitor and guarantee the agreed Quality of Service (QoS) to its customers. Consequently, an emergent way to measure QoS arises in the field of the telecommunications sector: the Quality of Experience (QoE) assessment and monitor that takes into account that subjective experience. Thus, a new challenging need arises: the development of systems and methods for assessing quality of experience, such that, network operators and service providers can actually know how users evaluate the quality of the service provided to them. In this paper, a system for assessing QoS/QoE is described: the ArQoS®. This is an integrated system provided by Portugal Telecom Inovação (PTIn) which implements QoE assessment methods to assess the networks performance and their telecommunications services. Beyond the existing methods already supported by the system, a novel QoE monitor for VoIP services was recently integrated as a result of fundamental research carried out at PTIn Labs. The ArQoS® is a probing system based on different types of probes, actually comprising two systems operating in two different modes: the active system (intrusive mode) and the passive system (non-intrusive mode).
- Energy Efficiency and Sustainability in an Aquaponic Greenhouse Supported by IoTPublication . Galvão, João; Santos, Pedro; Aires, Luis; Ribeiro, Vânia; Neves, FilipeThe increasing demand for agricultural crops and the necessity to reduce environmental impacts from traditional agriculture have led to the emergence of sustainable production systems such as hydroponics and aquaponics. These soil and pesticide-free systems require less water and fertilizers but need electrical energy and controlled greenhouse environmental conditions to be highly productive. This work presents a monitoring and management system for environmental parameters inside an aquaponic greenhouse, that allows the manager to assess in real-time the working status of the aquaponic system, helping in the detection of critical conditions that require a quick decision. This system was developed to measure, through IoT sensors network, the temperature and the relative humidity of the air, the temperature, pH and the electrical conductivity of the water that contains the dissolved nutrients that feed the growth of the plants. It is possible to visualize the measured parameters via the Internet, on a dashboard, in a mobile application and store these variables in a database. To further increase the sustainability of the aquaponic greenhouse, the electricity consumed during its activity will be produced locally by photovoltaic technology. The technologies proposed in this work may promote the emergence of small models of greenhouses, implemented by communities and populations, reducing production energy costs and transportation resources.
- Optimal voice packet classification for enhanced VoIP over priority-enabled networksPublication . Neves, Filipe; Soares, Salviano; Assunção, PedroThis paper proposes a method for optimal classification of voice packets to enhance the quality of voice communications over priority-enabled networks when poor transmission conditions occur. Either high or low priority is assigned to each packet according to the relevance of its payload (voice segment) for the voice intelligibility. Then, in case of constrained networking conditions, by discarding first the voice packets of lower importance, the network always delivers those segments that most contribute to the perceptual quality. The proposed method is based on a dynamic programming optimisation algorithm that finds the optimal subset of m high priority voice segments in each utterance of size n > m. Such optimal subset minimizes the reconstruction distortion over all possible subsets with the same size m (i.e., the distortion incurred by a utterance reconstructed from only m segments). The simulation results show that the proposed method consistently achieves higher mean opinion scores (MOS) in comparison with non-selective packet drop under the same random network loss conditions, yielding better quality of experience (QoE) for the same packet loss rates (PLR). The priority classification algorithm is independent from error concealment methods and distortion metrics used in the optimisation process, which allows generalisation for diverse communication networks and applications.
- Quality model for monitoring QoE in VoIP servicesPublication . Neves, Filipe; Cardeal, Simão; Soares, Salviano; Assunção, Pedro; Tavares, FilipeThis 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.