1,720,995 research outputs found
Mobility management in next generation networks
Full text linkLa definizione che l’ITU-T fornisce delle “Next Generation Network” (NGN) include la possibilità di poter utilizzare differenti tecnologie di accessi a banda larga e di supportare la mobilità. Inoltre le reti NGN hanno la necessità di integrare le diverse tecnologie di accesso alla rete IP in maniera del tutto trasparente. In questa tesi dapprima si definiscono i requisiti che una soluzione per la gestione della mobilità nei sistemi di comunicazione real-time dovrebbe avere. Successivamente si analizzano le soluzioni per la gestione della mobilità presenti in letteratura. A partire da quest’analisi nasce MMUSE (Mobility Management Using Extension) una soluzione per la gestione della mobilità a livello applicativo basata sul protocollo SIP in grado di soddisfare la maggior parte dei requisiti richiesti ad un sistema di gestione della mobilità fra reti eterogenee. Tale soluzione è stata inoltre implementata, per testare sul campo le sue capacità e la sua interoperabilità con diversi terminali e Server SIP. Inoltre, al fine di valutarne le prestazioni è stata effettuata una campagna di misure nel mondo reale utilizzando alcune reti di accesso commerciali (sia 3G che WiFi). Infine, si propone una metodologia per la valutazione delle prestazioni delle differenti soluzioni di gestione della mobilità precedentemente illustrate. Tale metodologia si compone di un semplice modello analitico applicabile sia ad un caso ideale (senza perdite) che un caso reale con un predefinito tasso di perdita dei pacchetti. Il modello è stato applicato a tre soluzioni MMUSE, MIPv4 e SIP re-INVITE.The ITU-T definition of Next Generation Networks includes the ability to make use of multiple broadband transport technologies and to support generalized mobility. Next Generation Networks will need to integrate several IP-based access technologies in a seamless way. In this Thesis, we first describe the requirements of a Mobility Management scheme for multimedia real-time communication services; then, we report a survey of the Mobility Management schemes proposed in the recent literature to perform vertical handovers between heterogeneous networks. Based on this analysis, we propose an application-layer solution for Mobility Management called MMUSE (Mobility Management Using SIP Extension), which is based on the SIP protocol, and satisfies the most important requirements demanded for a proper implementation of vertical handovers. We also implemented our proposed solution, testing it on the field and proving its overall feasibility and its interoperability with different terminals and SIP servers.
In our work we also report measurements results which analyze the performance of the solution in a real world environment, using commercial access networks (WiFi, 3G)
Finally we discuss a methodology for performance evaluation of the solutions for vertical handovers previously described. The performance evaluation is based on simple analytical models and covers both the ideal case (no packet loss) and the real case where there is a given packet loss rate. The methodology is applied to a comparison among three solutions, namely MIPv4, classical SIP mobility management using re-INVITE messages and the proposed MMUSE SIP based solution
UPMT: Universal Per-application Mobility management using Tunnels
Full text linkIn this paper we describe an application level Mobility Management mechanism for IP networks, called UPMT (Universal Per-Application Mobility management using Tunnels). The mechanism is able to provide Vertical Handovers over heterogeneous IP based access networks on a per-application basis, i.e. it is possible to independently route different applications over different access networks and take separate handover decisions for each application. UPMT is able to support legacy applications, does not require any support from the access networks nor any change to the TCP/IP stacks in the Mobile Hosts (MH), is able to run on NATed access networks that provide private IP addresses to MH and is fully transparent to Correspondent Hosts. UPMT relies on tunneling the IP packets from the MH to an Anchor Node on IP/UDP tunnels. UPMT provide the MH and the applications with a “virtual” NAT service across many different physical access network. The paper provide the specification of the tunneling architecture and of the mobility management signaling, based on SIP protocol. The Open Source implementation of UPMT for Linux OS is ongoing and its status is presented
SMILE-JS, a SIP-based middleware for J2ME devices
Full text linkIn this paper we report our two years experience in designing and implementing a new middleware solution for distributed mobile applications exploiting the Session Initiation Protocol (SIP) and the JavaScript Object Notation (JSON). The proposed solution has been designed to port the Simple Middleware Independent LayEr (SMILE) framework to mobile devices running the limited version of Java 2 Micro Edition (J2ME CLDC). It provides J2ME developers with the very same abstraction layer offered by the SMILE API under the J2SE environment, allowing seamless interoperability between SMILE peers running on desktop computers/servers and peers running on mobile devices. The solution will be denoted as SMILE-JS, where JS stands for JSON over SIP. We first describe the SMILE framework, explaining its APIs for communication, addressing, lifecycle management and service discovery. Afterwards we explain how truly peer to peer communication among mobile devices has been achieved using SIP, and which additions we implemented to turn the open source MjSIP framework into the first SIP-based middleware for J2ME CLDC enabled devices
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Author Correction: A Microfluidic Platform to design Multimodal PEG - crosslinked Hyaluronic Acid Nanoparticles (PEG-cHANPs) for diagnostic applications (Scientific Reports, (2020), 10, 1, (6028), 10.1038/s41598-020-63234-x)
No full textAn amendment to this paper has been published and can be accessed via a link at the top of the paper
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