Natalia Gómez

Quality assessment for video streaming P2P application over wireless mesh network

Wireless mesh networks (WMN) enables the expansion of communication networks and broadband services. This expansion allows the use of applications like streaming multimedia in P2P (Peer-to-Peer). P2P-TV and WMNs share similar features like self-organization and decentralization in dynamic network environments and multi-hop transmission. In this context quality measurement has become essential due to actual QoS (Quality of Service) parameters lack of user experience metrics. In order to evaluate QoE in P2P streaming over WMN, we use a Pseudo Subjective Quality Assessment (PSQA) taking the advantages of both subjective an objective approaches. The experimental testbed is implemented using PeerStreamer (P2P video streaming application) running over virtual machines, and the IEEE 802.11s NS-3 model as network layer connected through the NS-3 emulation mode.

Personalized message emission in a mobile application for supporting therapeutic adherence

Often chronic patients fail to follow all the recommendations in their treatments. This affects their health and increases the costs associated with their care. To help these patients to follow their therapy this paper proposes a recall and guide system implemented on a mobile device. The system emits custom messages according to the patients inferred mental state with the intention of persuading him to adhere to his medical prescriptions. To achieve personalization, the system uses ontologies to classify the messages and to model the user. When it is necessary to issue a reminder, the selection of the message is obtained by querying the relationships between the patients current model and the discourse ontology.

Nonintrusive method based on neural networks for video Quality of Experience assessment

The measurement and evaluation of the QoE (Quality of Experience) have become one of the main focuses in the telecommunications to provide services with the expected quality for their users. However, factors like the network parameters and codification can affect the quality of video, limiting the correlation between the objective and subjective metrics. The above increases the complexity to evaluate the real quality of video perceived by users. In this paper, a model based on artificial neural networks such as BPNNs (Backpropagation Neural Networks) and the RNNs (Random Neural Networks) is applied to evaluate the subjective quality metrics MOS (Mean Opinion Score) and the PSNR (Peak Signal Noise Ratio), SSIM (Structural Similarity Index Metric), VQM (Video Quality Metric), and QIBF (Quality Index Based Frame). The proposed model allows establishing the QoS (Quality of Service) based in the strategy Diffserv. The metrics were analyzed through Pearsons and Spearmans correlation coefficients, RMSE (Root Mean Square Error), and outliers rate. Correlation values greater than 90% were obtained for all the evaluated metrics.

Formación de líderes para la prevención del vih: percepciones y conocimientos sobre el virus en un contexto minero de Colombia

The study, based on the principles of qualitative research and social sciences, implemented and evaluated a rapid intervention for the prevention of hiv in mining contexts, which prioritized the training of community leaders. During a period of five months we trained ten leaders, who trained as well a group of 277 inhabitants, including miners and non miners. As a result we observed changes in the level of knowledge and perceptions about hiv. None of the 183 persons tested for hiv —rapid test— was reactive. We found important gaps in the knowledge about hiv combined with misconceptions about the infection in miners and non miners. We conclude that training of community leaders strengths community participation, health promotion and local capacity to prevent hiv in communities.

A Combined Sensitivity and Metabolic Flux Analysis Unravel the Importance of Amino Acid Feeding Strategies in Clavulanic Acid Biosynthesis

Metabolic flux analysis (MFA) is a computationally-dependent mathematical framework which can be used for determining the more representative variables of a biological system; MFA can be greatly improved by means of a sensitivity analysis (SA). In this work, we used a SA and a MFA to study the Streptomyces clavuligerus metabolism for clavulanic acid (CA) production. It was observed that the measured metabolic fluxes that significantly affected the cellular system were phenylalanine, isoleucine, tyrosine and lysine. According to the flux distribution at two dilution rates (D), the biosynthesis of CA was favored at low D, leading to higher values in the precursor fluxes of the tricarboxylic acid and urea cycles. Moreover, it was found that the flux of ornithine, rather than the flux of arginine, affects the biosynthesis of CA, which evidences the importance of controlling the flux of carbon through the urea cycle.

Throughput analysis of P2P video streaming on single-hop wireless networks

Video streaming services have been developed using different approaches. Peer-to-peer (P2P) streaming is a competitive technique in the distribution of video contents, thanks to its collaborative and sharing features. Nowadays, several applications distribute television contents over a P2P platform, broadcasting plenty of channels to an increasing audience. The performance of such applications over wireless networks is still an open issue, considering the highly variable environment, and the scarce resources. Most of these applications are developed to work properly over wired networks. This paper presents a performance evaluation model of the traffic behavior through an analytical representation, resembling the network interactions during a video transmission. The model, useful in determining the throughput parameter, does accurately evaluate the network performance. The analytical model is validated through the emulation mode in NS-3 simulator.

Traffic differentiation in IEEE 802.15.4 networks: An analysis over the contention window

The increasing interest in developing solutions for applications, such as industrial automation, body sensor networks, natural risks management and prevention; without the need of a wired media has encouraged the development of a low data rate and low power consumption wireless communication systems, commonly known as Wireless Sensor Networks (WSN). Although many proprietary solutions have been proposed, the standard IEEE 802.15.4 is about to become the global standard for WSN, since utilizes energy-efficient schemes to access the channel, and to transmit information at low speeds. However, this standard does not have a strategy for information differentiation, in which packets from nodes with a higher priority need to be sent sooner than packets from other nodes. Consequently, this paper evaluates, by means of numerical simulations, the assumption of an information differentiation scheme, which consists in modifying the Contention Window (CW) in the slotted IEEE 802.15.4, considering that nodes with lower CW values have higher probabilities to access the channel than nodes with higher CW values. Partial results show that this information differentiation scheme increases the channel access probability, when two or three levels of CW are implemented within the network.