Data consistency for cooperative caching in mobile environments

2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

ABMMCCS: Application based multi-level mobile cache consistency scheme

Maintaining cache consistency in mobile computing system is a critical issue due to the inheritance limitations in mobile environment such as limited network bandwidth and mobile device energy power.Most of the existing schemes maintaining mobile cache consistency support only one level of consistency that is either strict or weak which is not suitable all the time, as various mobile applications systems have different consistency requirements on their data.Also majority of the schemes restrict the using of cached data for reading only which is limits the functionality of the caching system.In this paper, a new scheme is proposed to maintain the mobile cache consistency in a single cell wireless network called Application Based Multi-Level Mobile Cache Consistency Scheme (ABMMCCS).The main idea in ABMMCCS is to be suitable to various real mobile application systems, by supporting multiple levels of consistency based on the application requirements, while savingthe mobile client energy power and reducing the consumption of the network bandwidth.The initial evaluation results show that, ABMMCCM reduces the number of uplink messages issued from the mobile client, which is assist in saving the mobile client energy and better utilizing the limited network bandwidth

A cache framework for nomadic clients of web services

This research explores the problems associated with caching of SOAP Web Service request/response pairs, and presents a domain independent framework enabling transparent caching of Web Service requests for mobile clients. The framework intercepts method calls intended for the web service and proceeds by buffering and caching of the outgoing method call and the inbound responses. This enables a mobile application to seamlessly use Web Services by masking fluctuations in network conditions. This framework addresses two main issues, firstly how to enrich the WS standards to enable caching and secondly how to maintain consistency for state dependent Web Service request/response pairs

Combining caching with a cloud hosted proxy to support mobile consumers of RESTful services

There are numerous problems to be addressed when connecting mobile clients (e.g. smartphones and tablet devices) with Web services. These devices consume Web services via wireless channels; and as a result, developers and researchers are investigating different approaches to address challenges related to network fluctuation, latency, and low bandwidth. In addition, most of these devices have limited capabilities in terms of information processing and resource storage. This research focuses on enabling mobile devices for consuming RESTful Web services efficiently. The aforementioned problems of network instability are addressed in this research by proposing and implementing a cloud centric proxy server architecture; which is based on mirroring resources. The mirroring of the Web server’s resources on the mobile device and the proposed proxy server is achieved by exploring caching techniques. Furthermore, an evaluation is done to determine what kind of components and architecture is required for supporting resource constraint mobile devices like smartphones and tablets while connecting them with RESTful systems. By linking the caching components of the mobile devices with a cloud-hosted proxy server, it becomes possible to share caches and achieve significant performance boost for mobile consumers of the RESTful Web services

Cooperative Caching in Vehicular Networks - Distributed Cache Invalidation Using Information Freshness

Recent advances in vehicular communications has led to significant opportunities to deploy variety of applications and services improving road safety and traffic efficiency to road users. In regard to traffic management services in distributed vehicular networks, this thesis work evaluates managing storage at vehicles efficiently as cache for moderate cellular transmission costs while still achieving correct routing decision. Road status information was disseminated to oncoming traffic in the form of cellular notifications using a reporting mechanism. High transmission costs due to redundant notifications published by all vehicles following a basic reporting mechanism: Default-approach was overcome by implementing caching at every vehicle. A cooperative based reporting mechanism utilizing cache: Cooperative-approach, was proposed to notify road status while avoiding redundant notifications. In order to account those significantly relevant vehicles for decision-making process which did not actually publish, correspondingly virtual cache entries were implemented. To incorporate the real-world scenario of varying vehicular rate observed on any road, virtual cache entries based on varying vehicular rate was modeled as Adaptive Cache Management mechanism. The combinations of proposed mechanisms were evaluated for cellular transmission costs and accuracy achieved for making correct routing decision. Simulation case studies comprising varying vehicular densities and different false detection rates were conducted to demonstrate the performance of these mechanisms. Additionally, the proposed mechanisms were evaluated in different decision-making algorithms for both information freshness in changing road conditions and for robustness despite false detections. The simulation results demonstrated that the combination of proposed mechanisms was capable of achieving realistic information accuracy enough to make correct routing decision despite false readings while keeping network costs significantly low. Furthermore, using QoI-based decision algorithm in high density vehicular networks, fast adaptability to frequently changing road conditions as well as quick recovery from false notifications by invalidating them with correct notifications were indicated

Investigação e implementação de estratégias de notificação de invalidação para coerência de cache em ambientes de computação móvel sem fio

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Ciência da ComputaçãoA computação móvel está se tornando um ambiente de uso comum nos dias atuais. Desta forma é importante fornecer aos seus usuários serviços com uma qualidade similar à encontrada em ambientes cabeados

Réseaux ad hoc : système d'adressage et méthodes d'accessibilité aux données

RÉSUMÉ Au cours de la dernière décennie, un nouveau type de réseaux sans fil a suscité un grand intérêt dans la communauté scientifique: ce sont les réseaux ad hoc. Ils existent sous la variante des réseaux mobiles ad hoc (MANET), et des réseaux de capteurs sans fil (RCSF). Les réseaux mobiles ad hoc sont constitués de noeuds mobiles qui communiquent les uns avec les autres sans l‘aide d‘une d'infrastructure centralisée. Les noeuds se déplacent librement et sont soumis à des déconnexions fréquentes en raison de l'instabilité des liens. Cela a pour conséquence de diminuer l'accessibilité aux données, et de modifier la façon dont les données sont partagées dans le réseau. Comparable aux réseaux MANET, un RCSF est composé d'un ensemble d'unités de traitements embarquées, appelées capteurs, communiquant via des liens sans fil et dont la fonction principale est la collecte de paramètres relatifs à l'environnement qui les entoure, telles que la température, la pression, ou la présence d'objets. Les RCSF diffèrent des MANET de par le déploiement à grande échelle des noeuds, et trouvent leur application dans diverses activités de la société, tels les processus industriels, les applications militaires de surveillance, l'observation et le suivi d'habitat, etc. Lorsqu‘un grand nombre de capteurs sont déployés avec des dispositifs d'actionnement appelés acteurs, le RCSF devient un réseau de capteurs et d‘acteurs sans fil (RCASF). Dans une telle situation, les capteurs collaborent pour la détection des phénomènes physiques et rapportent les données afférentes aux acteurs qui les traitent et initient les actions appropriées. De nombreux travaux dans les RCSF supposent l'existence d'adresses et d'infrastructures de routage pour valider leurs propositions. Cependant, l‘allocation d‘adresses et le routage des données liées aux événements détectés dans ces réseaux restent des défis entiers, en particulier à cause du nombre élevé de capteurs et des ressources limitées dont ils disposent. Dans cette thèse, nous abordons le problème de l'accessibilité aux données dans les MANET, et les mécanismes d‘adressage et de routage dans les RCSF de grande taille.----------ABSTRACT During the last decade, a new type of wireless networks has stirred up great interest within the scientific community: there are ad hoc networks. They exist as mobile ad hoc networks (MANET), and wireless sensor (WSN). The mobile ad hoc networks consist of mobile nodes that communicate with each other without using a centralized infrastructure. The nodes move freely and are subject to frequent disconnections due to links instability. This has the effect of reducing data accessibility, and change the way data are shared across the network. Similar MANET networks, a WSN consists of a set of embedded processing units called sensors that communicate with each other via wireless links. Their main function is the collection of parameters relating to the environment around them, such as temperature, pressure, motion, video, etc. WSNs differ from the MANETs due to the large scale deployment of nodes, and are expected to have many applications in various fields, such as industrial processes, military surveillance, observation and monitoring of habitat, etc. When a large number of sensors which are resource-impoverished nodes are deployed with powerful actuation devices, the WSN becomes a Wireless Sensor and Actor Network (WSAN). In such a situation, the collaborative operation of sensors enables the distributed sensing of a physical phenomenon, while actors collect and process sensor data to perform appropriate action. Numerous works in WSN assumes the existence of addresses and routing infrastructure to validate their proposals. However, assigning addresses and delivering detected events remains highly challenging, specifically due to the sheer number of nodes. In this thesis, we address the problem of data accessibility in MANET, and that of addressing and routing in large scale WSN. This involves techniques such as data caching and replication to prevent the deterioration of data accessibility. The addressing system in WSN includes a distributed address allocation scheme and a routing infrastructure for both actors and sensors. Moreover, with the birth of the multimedia sensors, the traffic may be mixed with time sensitive packets and reliability-demanding packets. For that purpose, we also address the problem of providing quality of service (QoS) in the routing infrastructure for WSN