DHT-based distributed ALE engine in RFID Middleware

Following the “Internet of Things” concept, each object is associated with a unique identifier which will allow to retrieve information about it in large databases. In the process of managing a large amount of objects, and consequently a large amount of events from readers, without overloading the network, these events have to be filtered and aggregated. This is the aim of the Application Level Events (ALE) standard from EPCGlobal, which receives events from readers and sends a useful and well constructed report to the business application. The ALE may be connected to several hundreds of readers. As the number of readers may increase with the increase of the company, a bottleneck may appear with all readers events sent to the ALE. A solution for scalability is to distribute the ALE. In this research report, we propose an efficient way to solve this problem based on a Distributed Hash table (DHT). One role of the ALE is to insulate business application from technical concern so in our solution, we present a mechanism to distribute the ALE using Chord, a well-known peer-to-peer lookup system, and being transparent for business application. This solution is compliant with the EPCglobal existing standard, scalable, robust and transparent for other layers of the middleware. We show that the overhead generated by our solution is of 10% only in a nominal case

Bundling Messages to Reduce the Cost of Tree-Based Broadcast Algorithms

International audienceHierarchical broadcast strategies based on trees are scalable since they distribute the workload among processes and disseminate messages in parallel. In this work we propose an efficient best-effort broadcast algorithm that employs multiple spanning trees to propagate messages that are bundled on tree intersections. The algorithm is autonomic in the sense that it employs dynamic trees rooted at the source process and which rebuild themselves after processes crash. Experimental results obtained with simulation are presented showing the performance to the algorithm in terms of the latency and the number and sizes of messages employed

A Communication-Efficient Causal Broadcast Protocol

International audienceA causal broadcast ensures that messages are delivered to all nodes (processes) preserving causal relation of the messages. In this paper, we propose a causal broadcast protocol for distributed systems whose nodes are logically organized in a virtual hypercube-like topology called VCube. Messages are broadcast by dynamically building spanning trees rooted in the message's source node. By using multiple trees, the contention bottleneck problem of a single root spanning tree approach is avoided. Furthermore , different trees can intersect at some node. Hence, by taking advantage of both the out-of-order reception of causally related messages at a node and these paths intersections, a node can delay to one or more of its children in the tree, the forwarding of the messages whose some causal dependencies it knows that the children in question can not satisfy yet. Such a delay does not induce any overhead. Experimental evaluation conducted on top of PeerSim simulator confirms the communication effectiveness of our causal broadcast protocol in terms of latency and message traffic reduction

HI3: una aproximación integrada a la construcción de sistemas de inteligencia ambiental

[Resumen] El objetivo de la Inteligencia Ambiental (IAm) es mejorar la calidad de vida de las personas a través de la integración transparente de tecnologías en sus entornos. Dentro de la IAm, este trabajo se centra en facilitar el desarrollo de sistemas de IAm ubicuos y capaces de adaptarse dinámicamente a las características de distintos escenarios, poniendo énfasis en la adaptación a las necesidades de los usuarios y en la adaptación al entorno físico. Los entornos de IAm son altamente heterogéneos y abiertos. Esta diversidad hace que resulte muy difícil anticipar todas las condiciones en las que un sistema va a operar, complicando el desarrollo de aplicaciones capaces de adaptarse a distintos contextos. Esta tesis aborda el proceso de construcción de sistemas de IAm desde una aproximación integrada y uniforme. Para ello, se propone un modelo conceptual y una arquitectura software que faciliten el desarrollo de aplicaciones de IAm aislando al desarrollador de la heterogeneidad de tecnologías y recursos que pueden estar presentes en estos entornos. Además, también se proporciona una implementación de la arquitectura que posibilita la creación de sistemas de IAm adaptables en base a la colaboración entre componentes interoperables.[Resumo] O obxectivo da Intelixencia Ambiental (IAm) é mellorar a calidade de vida das persoas a través da integración transparente de tecnoloxías nas súas contornas. Dentro da IAm, esta tese céntrase en facilitar o desenvolvemento de sistemas de IAm ubicuos e capaces de adaptarse dinámicamente ás características de distintos escenarios, poñendo énfases na adaptación ás necesidades dos usuarios e na adaptación á contorna física. As contornas de IAm son altamente heteroxéneas e abertas. Esta diversidade fai que resulte moi difícil anticipar todas as condicións nas que un sistema vai operar, complicando o desenvolvemento de aplicacións capaces de adaptarse a distintos contextos. Esta tese aborda o proceso de construción de sistemas de IAm desde unha aproximación integrada e uniforme. Para iso, proponse un modelo conceptual e unha arquitectura software que faciliten o desenvolvemento de aplicacións de IAm illando ao desenvolvedor de software da heteroxeneidade de tecnoloxías e recursos que poden estar presentes nestas contornas. Ademais, tamén se proporciona unha implementación da arquitectura que posibilita a creación de sistemas de IAm adaptables en base á colaboración entre compoñentes interoperables.[Abstract] Ambient Intelligence (AmI) is about systems that assist people to improve their quality of life through the seamless integration of technologies in their environments. This work is focused on facilitating the development of ubiquitous AmI systems that are able to dynamically adapt to the characteristics of different scenarios, emphasizing the adaptation to the user needs and the physical environment. AmI environments are open and highly heterogeneous. This diversity makes it very difficult to anticipate all the conditions under which a system will operate, complicating the development of applications that can adapt to different contexts. This thesis deals with the construction process of AmI systems from an integrated and uniform approach. For this purpose, a conceptual model and a software architecture that facilitates the development of AmI applications, isolating the developer from the heterogeneous technologies and resources that may be present in these environments, are proposed. In addition, an implementation of the architecture that enables the creation of adaptable AmI systems based on the collaboration between interoperable components is also provided