A survey on probabilistic broadcast schemes for wireless ad hoc networks

Broadcast or flooding is a dissemination technique of paramount importance in wireless ad hoc networks. The broadcast scheme is widely used within routing protocols by a wide range of wireless ad hoc networks such as mobile ad hoc networks, vehicular ad hoc networks, and wireless sensor networks, and used to spread emergency messages in critical scenarios after a disaster scenario and/or an accidents. As the type broadcast scheme used plays an important role in the performance of the network, it has to be selected carefully. Though several types of broadcast schemes have been proposed, probabilistic broadcast schemes have been demonstrated to be suitable schemes for wireless ad hoc networks due to a range of benefits offered by them such as low overhead, balanced energy consumption, and robustness against failures and mobility of nodes. In the last decade, many probabilistic broadcast schemes have been proposed by researchers. In addition to reviewing the main features of the probabilistic schemes found in the literature, we also present a classification of the probabilistic schemes, an exhaustive review of the evaluation methodology including their performance metrics, types of network simulators, their comparisons, and present some examples of real implementations, in this paper

External collaboration patterns of research institutions using shared publications in the Web of Science

Purpose – During recent decades, research institutions have increased collaboration with other institutions since it is recognized as a good practice that improves their performance. However, they do not usually consider external collaborations as a strategic issue despite their benefits. The purpose of this paper consists of identifying different patterns of collaboration and internationalization of universities, with the aim of helping managers and policy makers to take decisions related to their national research policies. Design/methodology/approach – Co-authorship analysis has been used in conjunction with social network analysis to model inter-institutional collaborations as networks, extracting these collaborations from the Web of Science database. Using several structural properties of the extracted networks and applying a statistical treatment, the main profiles of collaborations and internationalization have been obtained. Findings – Obtained results distinguish three patterns of collaborations according to the intensity and scope of collaborations. The statistical treatment also provides a segmentation of universities according to their collaboration profiles. Finally, universities are represented in bi-dimensional maps using external collaborations as a measure of similarity. Research limitations/implications – Although this study is restricted to English universities, it could probably be extended at least to other countries in the European Union or even other developed countries. Practical implications – Research and institutions productivity are usually linked to the amount of received funding. The use of indicators related to internationalization of institutions can help to avoid a bias in favour of research quantity rather than quality, and towards a short-term performance rather than a long-term research capacity. Originality/value – As a difference to previous works, this paper analyses networks of collaboration from the viewpoint of institutions. More specifically, the combination of social network analysis and factor analysis is used to identify patterns of collaboration among institutions. A longitudinal study is also included to demonstrate that the obtained categorization of universities is maintained over time

ESTUDIO Y ANÁLISIS DE LAS LISTAS DE DISTRIBUCIÓN EN PROYECTOS DE SOFTWARE DE CÓDIGO ABIERTO COMO MEDIO PARA COMPARTIR CONOCIMIENTO

RESUMENEste trabajo explora el papel desempeñado por las listas de distribución en proyectos de software de código abierto como herramienta para compartir conocimiento y resolver problemas. Uno de los principales beneficios que las empresas pueden obtener del uso de software de código abierto es la colaboración informal en desarrollo de aplicaciones. La herramienta más importante para esa colaboración y coordinacion son las listas de correo, seguido por los foros de discusión asíncronos, informes de bugs y chat. Uno de los argumentos principales a la hora de decidirse por una distribución de Linux embebido es el soporte proporcionado a los desarrolladores. Pero generalmente, es difícil tomar una decisión a priori sin conocer si el soporte proporcionado será lo suficientemente bueno durante todo el futuro desarrollo del proyecto. Para ayudar en esta tarea, este trabajo se centra en analizar el comportamiento y la actividad de las listas de correo para extraer una serie de parámetros que puedan aportar información sobre la calidad y la evolución de la lista. Esta información resultaría relevante para analizar y decidir sobre la mejor distribución de Linux embebido a utilizar.ABSTRACTThis research explores the role of mailing lists in open source software projects as a tool for knowledge sharing and problem resolution. One of the benefits that firms can derive from using Open Source Software (OSS) is informal development collaboration. The primary tool for collaboration and coordination are group mailing lists, followed by asynchronous discussion forums, bug reports, and chat. One of the main arguments when deciding about an embedded Linux distribution is the support provided to developers. However, it is usually difficult to decide a priori if the provided support will be good enough for the future development of the project. Particularly, the behaviour and activity of mailing list are analyzed to extract a set of parameters that could inform about the quality and the evolution of the list. This information could be useful to decide the best embedded distribution to be implemented

Modelling incidents for dynamic bus fleet management purposes: a UK perspective

Bus operations throughout the world are increasingly being equipped with Intelligent Transport Systems such as Automatic Vehicle Location (AVL). AVL can support a variety of functions, including Dynamic Bus Fleet Management (DBFM), which has yet to be established in most bus fleets in the UK in a systematic way. To develop a fundamental understanding of the bus and traffic related incidents in bus-based public transport for DBFM purposes, a microscopic simulation model, capable of modelling these incidents, has been developed and applied to a variety of scenarios. This paper describes the design and development of the model Simulating Incidents for BUs FlEet Management (SIBUFEM), for modelling bus operations during full-day periods in which incidents of different types can occur. The paper describes the model's functionality, including the use of journey time profiles, passenger-dependent bus stop dwell times and deterministic time-dependent queuing theory. Results focus on key performance measures including, but not limited to, bus journey times, passenger waiting times and bus delays resulting from various bus and traffic incidents. SIBUFEM has been applied to a main bus corridor in Southampton, UK, with bus flows increased to produce a high-frequency service. A base case of ‘normal’ operations has been established, for comparison with results from a number of incident scenarios, using key model performance parameters of average bus journey time, bus speed and excess waiting time. Incidents range from bus breakdowns, to traffic incidents such as road-works, traffic accidents and illegal parking. In SIBUFEM, these are specified in terms of their location, duration and severity (loss of capacity). The paper concludes with a discussion on potential DBFM strategies and how the SIBUFEM can be further developed to allow these strategies to be evaluated<br/