Actas da 10ª Conferência sobre Redes de Computadores

Universidade do MinhoCCTCCentro AlgoritmiCisco SystemsIEEE Portugal Sectio

Towards Seamless Mobility: An IEEE 802.21 Practical Approach

In the recent years, mobile devices such as cell phones, notebook or ultra mobile computers and videogame consoles are experiencing an impressive evolution in terms of hardware and software possibilities. Elements such a wideband Internet connection allows a broad range of possibilities for creative developers. Many of these possibilities can include applications requiring continuity of service when the user moves form a coverage area to another. Nowadays, mobile devices are equipped with one or more radio interfaces such as GSM, UMTS, WiMax or Wi‐ Fi. Many of these technologies are ready to allow transparent roaming within their own coverage areas, but they are not ready to handle a service transfer between different technologies. In order to find a solution to this issue, the IEEE has developed a standard known as Media Independent Handover (MIH) Services with the aim of easing seamless mobility between these technologies. The present work has been centered in developing a system capable to enable a service of mobility under the terms specified in the stated standard. The development of a platform aiming to provide service continuity is mandatory, being a cross‐layer solution based in elements from link and network layers supplying a transparent roaming mechanism from user’s point of view. Two applications have been implemented in C/C++ language under a Linux environment. One application is designed to work within a mobile device, and the other one in the network access point. The mobile device basically consists in a notebook equipped with two Wi‐Fi interfaces, which is not a common feature in commercial devices, allowing seamless communication transfers aided by the application. Network access points are computers equipped with a Wi‐Fi interface and configured to provide Internet wireless access and services of mobility. In order to test the operation, a test‐bed has been implemented. It consists on a pair of access points connected through a network and placed within partially overlapped coverage areas, and a mobile device, all of them properly set. The mobile detects the networks that are compatible and gets attached to the one that provides better conditions for the demanded service. When the service degrades up to certain level, the mobile transfers the communication to the other access point, which offers better service conditions. Finally, in order to check if the changes have been done properly, the duration of the required actions has been measured, as well as the data that can have been lost or buffered meanwhile. The result is a MIH‐alike system working in a proper way. The discovery and selection of a destination network is correct and is done before the old connection gets too degraded, providing seamless mobility. The measured latencies and packet losses are affordable in terms of MIH protocol, but require future work improvements in terms of network protocols that have not been considered under the scope of this work

An empirical investigation of the adoption and usage of electronic data interchange in the hotel industry

This dissertation examines the application of Electronic Data Interchange (EDI) adoption and use in the hotel industry. EDI is a type of interorganizational information system that facilitates the exchange of business documents in structured, machine processable form. The research model links EDI adoption to four usages: purchasing, accounting, financing and strategic. Based on relevant literature, six theories were selected from which, nineteen hypotheses were proposed for the relationships between EDI adoption and usage; The data were collected through a self-administered questionnaire that was mailed out to 1200 hotel manager with the title of purchasing managers, controllers, and management information systems managers. The managers had the option of mailing in the questionnaire or go to the following Web Site: http://www.unlv.edu/faculty/ramdeen/EDIsurvey.htm and fill out the questionnaire then submit. The usable responses were 287 (23.92 rate); The hypotheses were tested using multiple regression analysis. The analysis supports the following hypothesis: (1) EDI purchasing and financing usage is positively related to property size, (2) trading status is positively related to purchasing use, (3) business presence/feedback and quality is positively related to strategic use, (4) uncertainty is positively related to purchases and strategic use, (5) analyzability is positively related to strategic use, and (6) interdependence is positively related to purchase and strategic use; EDI is one of the many ways hotels may exchange information. This study shows that EDI can be use by hotels for purchasing, financing and strategic purposes. For hotels to improve their internal usages of EDI two conditions must be accomplish. First, hotels must improve the information flow between their trading partners. Second, the information flow must be sufficient to stimulate intraorganizational usages. It is anticipated that the role of EDI in hotels will continue to grow in the future. Presently, EDI in hotels are more confine to purchasing (purchase or purchase order processing), and strategic use (long-term procurement contracts and linkages to electronic funds). In the future, EDI could become an important tool for hotels to use in conducting business in both an interorganizational and intraorganizational way; Research on EDI is still in a growth stage. By identifying and testing relevant intraorganizational variables, this study offers insights to practitioners managing internal activities within hotels that are currently using or planning to use EDI. Further, the dissertation provides avenues for future research aimed at understanding the applications of EDI technology and its administrative capabilities that could benefit both practitioners and academics

An Introduction to Database Systems

This textbook introduces the basic concepts of database systems. These concepts are presented through numerous examples in modeling and design. The material in this book is geared to an introductory course in database systems offered at the junior or senior level of Computer Science. It could also be used in a first year graduate course in database systems, focusing on a selection of the advanced topics in the latter chapters

Projecting Self and Other Through Akogare (Desire) Among Japanese University Students: The English Language and the Internationalization of Higher Education in a Changing Japan.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017

Anales del XIII Congreso Argentino de Ciencias de la Computación (CACIC)

Contenido: Arquitecturas de computadoras Sistemas embebidos Arquitecturas orientadas a servicios (SOA) Redes de comunicaciones Redes heterogéneas Redes de Avanzada Redes inalámbricas Redes móviles Redes activas Administración y monitoreo de redes y servicios Calidad de Servicio (QoS, SLAs) Seguridad informática y autenticación, privacidad Infraestructura para firma digital y certificados digitales Análisis y detección de vulnerabilidades Sistemas operativos Sistemas P2P Middleware Infraestructura para grid Servicios de integración (Web Services o .Net)Red de Universidades con Carreras en Informática (RedUNCI