Dynamic viewing pattern exploitation in Peer-to-Peer Video-on-Demand

Unstructured BitTorrent-like Peer-to-Peer networks have been extensively studied as an important enabling technology for Video-on-Demand. While most studies maintain the pull-based nature of unstructured Peer-to-Peer networks, recent ones are investigating the combination of pull and push operations. The goal of the proposed push/pull protocols is to make more effcient use of the available bandwidth, however, this paper proposes a different use, the exploitation of users' viewing patterns (random seek patterns) in Video-on-Demand applications. As viewing pattern exploitation has not been given signif cant attention so far, we propose a scheme to prioritize chunk distribution based on the video's points of interest. © 2011 IEEE

Uplink allocation based on user actions for peer-to-peer Video-on-Demand

For more than a decade peer-to-peer networking technologies have met with huge success among Internet users, with peer-to-peer traffic already accounting for the largest part of the Internet's total traffic. Peer-to-peer networks have been extensively studied in recent years as an important supporting technology for state-of-the art applications, such as Live Video Streaming and Video-on-Demand. In this work the case of video-on-demand applications over BitTorrent-like unstructured peer-to-peer networks is considered. As a rule, unstructured peer-to-peer networks are pull-based, whereas push-based operation has been associated mostly with structured, tree-based p2p network topologies. While earlier studies maintained the pull-based nature of unstructured networks, recent ones have been investigating the combined use of pull and push operations, aiming at making more efficient use of the available bandwidth. Inspired by such hybrid approaches, this paper proposes a different use for push/pull protocols, uplink allocation based on user actions (i.e. random seek behavior) in video-on-demand applications. In a nutshell, this work proposes the employment of user-triggered push operations to prioritize content pre-fetching for the seemingly more popular parts for the users watching a video, thus increasing replication of such parts across the swarm. © 2014 IEEE

A class of multi-carrier CDMA access methods for wide-bandwidth wireless channels

In this article we describe and evaluate a general class of synchronous multi-carrier CDMA methods. In the proposed methods each accessing user is encoded by a Hadamard sequence and a multi-carrier (MC) encoder. The MC-encoder may provide one or many sub-carriers for each access channel while each accessing user may distribute its transmit power over all sub-carriers of its own access channel or over all sub-carriers of all access channels. Each sub-carrier then carries the transmitted symbols of all users which are distinguished by their Hadamard sequences. In the performance evaluation presented herein we have examined their tolerance to synchronization jitter. © 2005 IEEE

Seismic hazard for selected sites in Greece: A Bayes-ian estimate of seismic peak ground acceleration, Natural Hazards

Abstract. A procedure for estimating maximum values of seismic peak ground acceleration at the examined site and quantiles of its probabilistic distribution in a future time interval of a given length is considered. The input information for the method are seismic catalog and regression relation between peak seismic acceleration at a given point and magnitude and distance from the site to epicenter (seismic attenuation law). The method is based on Bayesian approach, which simply accounts for influence of uncertainties of seismic acceleration values. The main assumptions for the method are Poissonian character of seismic events flow and distribution law of Gutenberg-Richter's type. The method is applied to seismic hazard estimation in six selected sites in Greece

Probabilistic Tsunami Hazard Assessment from Incomplete and Uncertain Historical Catalogues with Application to Tsunamigenic Regions in the Pacific Ocean

The paper presents a new method for empirical assessment of tsunami recurrence parameters, namely the mean tsunami activity rate λT , the Soloviev–Imamura frequency–magnitude power law bT -value, and the coastline-characteristic, maximum possible tsunami intensity imax . The three coastline-characteristic recurrence parameters are estimated locally by maximum likelihood techniques using only tsunami event catalogues. The method provides for incompleteness of the tsunami catalogue, uncertainty in the tsunami intensity determination, and uncertainty associated with the parameters in the applied tsunami occurrence models. Aleatory and epistemic uncertainty is introduced in the tsunami models by means of the use of mixture distributions. Both the mean tsunami activity rate λT of the Poisson occurrence model, and the bT -value of the Soloviev–Imamura frequency–intensity power law are random variables. The proposed procedure was applied to estimate the probabilities of exceedance and return periods for tsunamis in the tsunamigenic regions of Japan, Kuril–Kamchatka, and South America