Adaptive Prioritized Random Linear Coding and Scheduling for Layered Data Delivery From Multiple Servers

In this paper, we deal with the problem of jointly determining the optimal coding strategy and the scheduling decisions when receivers obtain layered data from multiple servers. The layered data is encoded by means of prioritized random linear coding (PRLC) in order to be resilient to channel loss while respecting the unequal levels of importance in the data, and data blocks are transmitted simultaneously in order to reduce decoding delays and improve the delivery performance. We formulate the optimal coding and scheduling decisions problem in our novel framework with the help of Markov decision processes (MDP), which are effective tools for modeling adapting streaming systems. Reinforcement learning approaches are then proposed to derive reduced computational complexity solutions to the adaptive coding and scheduling problems. The novel reinforcement learning approaches and the MDP solution are examined in an illustrative example for scalable video transmission . Our methods offer large performance gains over competing methods that deliver the data blocks sequentially. The experimental evaluation also shows that our novel algorithms offer continuous playback and guarantee small quality variations which is not the case for baseline solutions. Finally, our work highlights the advantages of reinforcement learning algorithms to forecast the temporal evolution of data demands and to decide the optimal coding and scheduling decisions

Network-coded NOMA with antenna selection for the support of two heterogeneous groups of users

The combination of Non-Orthogonal Multiple Access (NOMA) and Transmit Antenna Selection (TAS) techniques has recently attracted significant attention due to the low cost, low complexity and high diversity gains. Meanwhile, Random Linear Coding (RLC) is considered to be a promising technique for achieving high reliability and low latency in multicast communications. In this paper, we consider a downlink system with a multi-antenna base station and two multicast groups of single-antenna users, where one group can afford to be served opportunistically, while the other group consists of comparatively low power devices with limited processing capabilities that have strict Quality of Service (QoS) requirements. In order to boost reliability and satisfy the QoS requirements of the multicast groups, we propose a cross-layer framework including NOMAbased TAS at the physical layer and RLC at the application layer. In particular, two low complexity TAS protocols for NOMA are studied in order to exploit the diversity gain and meet the QoS requirements. In addition, RLC analysis aims to facilitate heterogeneous users, such that, sliding window based sparse RLC is employed for computational restricted users, and conventional RLC is considered for others. Theoretical expressions that characterize the performance of the proposed framework are derived and verified through simulation results

População e Enriquecimento de Ontologias através de Web Scraping

O surgir da World Wide Web providenciou aos utilizadores uma série de oportunidades no que diz respeito ao acesso a dados e informação. Este acesso tornou-se um ato banal para qualquer utilizador da Web, tanto pelo utilizador comum como por outros mais experientes, tanto para obter informações básicas, como outras informações mais complexas. Todo este avanço tecnológico permitiu que os utilizadores tivessem acesso a uma vasta quantidade de informação, dispersa pelo globo, não tendo, na maior parte das vezes, a informação qualquer tipo de ligação entre si. A necessidade de se obter informação de interesse relativamente a determinado tema, mas tendo que recorrer a diversas fontes para obter toda a informação que pretende obter e comparar, torna-se um processo moroso para o utilizador. Pretende-se que este processo de recolha de informação de páginas web seja o mais automatizado possível, dando ao utilizador a possibilidade de utilizar algoritmos e ferramentas de análise e processamento automáticas, reduzindo desta forma o tempo e esforço de realização de tarefas sobre páginas web. Este processo é denominado Web Scraping. Neste trabalho é descrita uma arquitetura de sistema de web scraping automático e configurável baseado em tecnologias existentes, nomeadamente no contexto da web semântica. Para tal o trabalho desenvolvido analisa os efeitos da aplicação do Web Scraping percorrendo os seguintes pontos: • Identificação e análise de diversas ferramentas de web scraping; • Identificação do processo desenvolvido pelo ser humano complementar às atuais ferramentas de web scraping; • Design duma arquitetura complementar às ferramentas de web scraping que dê apoio ao processo de web scraping do utilizador; • Desenvolvimento dum protótipo baseado em ferramentas e tecnologias existentes; • Realização de experiências no domínio de aplicação de páginas de super-mercados portugueses; • Analisar resultados obtidos a partir destas.The rise of the World Wide Web has provided users with a lot of opportunities with regard to access to data and information. This access has become a banal act for any user of the Web by both the common user as for more experienced users, both for basic information, and more complex information. All this technological development has enabled users to have access to a vast amount of information scattered over the globe and they do not have, in most cases, any information linked. The need to obtain information of interest for a given topic, but having to use various sources to get all the information you want to obtain and compare it becomes a time consuming process for the user. It is intended that this process of gathering information from web pages is as automated as possible, giving the user the possibility of using algorithms and analysis tools and automatic processing, thereby reducing the time and effort embodiment tasks on web pages. This process is called Web Scraping. It is described an architecture for automated web scraping and configurable system based on existing technologies, particularly in the context of semantic web. For this, the developed work analyzes the effects of applying Web Scraping covering the following points: • Identification and analysis of various tools for web scraping; • Identification of additional process developed by man to supplement current web scraping tools; • Design of a complement to the architecture of web scraping tool that gives support to the scraping web user process; • Development of a prototype based on existing tools and technologies; • Conducting experiments in the portuguese super markets domain; • Analyzing the experiments’ results