A Fault-Tolerant Mobile Computing Model Based On Scalable Replica

The most frequent challenge faced by mobile user is stay connected with online data, while disconnected or poorly connected store the replica of critical data. Nomadic users require replication to store copies of critical data on their mobile machines. Existing replication services do not provide all classes of mobile users with the capabilities they require, which include: the ability for direct synchronization between any two replicas, support for large numbers of replicas, and detailed control over what files reside on their local (mobile) replica. Existing peer-to-peer solutions would enable direct communication, but suffers from dramatic scaling problems in the number of replicas, limiting the number of overall users and impacting performance. Roam is a replication system designed to satisfy the requirements of the mobile user. Roam is based on the Ward Model, replication architecture for mobile environments. Using the Ward Model and new distributed algorithms, Roam provides a scalable replication solution for the mobile user. We describe the motivation, design, and implementation of Roam and report its performance. Replication is extremely important in mobile environments because nomadic users require local copies of important data

DataStations: ubiquitous transient storage for mobile users

technical reportIn this paper, we describe DataStations, an architecture that provides ubiquitous transient storage to arbitrary mobile applications. Mobile users can utilize a nearby DataStation as a proxy cache for their remote home file servers, as a file server to meet transient storage needs, and as a platform to share data and collaborate with other users over the wide area. A user can roam among DataStations, creating, updating and sharing files via a native file interface using a uniform file name space throughout. Our architecture provides transparent migration of file ownership and responsibility among DataStations and a user?s home file server. This design not only ensures file permanence, but also allows DataStations to reclaim their resources autonomously, allowing the system to incrementally scale to a large number of DataStations and users. The unique aspects of our DataStation design are its decentralized but uniform name space, its locality-aware peer replication mechanism, and its highly flexible consistency framework that lets users select the appropriate consistency mechanism on a per-file replica basis. Our evaluation demonstrates that DataStations can support low-latency access to remote files as well as ad-hoc data sharing and collaboration by mobile users, without compromising consistency or data safety

Mediation of Lazy Update Propagation in a Replicated Database over a Decentralized P2P Architecture

While replicating data over a decentralized Peer-to- Peer (P2P) network, transactions broadcasting updates arising from different peers run simultaneously so that a destination peer replica can be updated concurrently, that always causes transaction and data conflicts. Moreover, during data migration, connectivity interruption and network overload corrupt running transactions so that destination peers can experience duplicated data or improper data or missing data, hence replicas remain inconsistent. Different methodological approaches have been combined to solve these problems: the audit log technique to capture the changes made to data; the algorithmic method to design and analyse algorithms and the statistical method to analyse the performance of new algorithms and to design prediction models of the execution time based on other parameters. A Graphical User Interface software as prototype, have been designed with C #, to implement these new algorithms to obtain a database synchronizer-mediator. A stream of experiments, showed that the new algorithms were effective. So, the hypothesis according to which 201C;The execution time of replication and reconciliation transactions totally depends on independent factors.201D; has been confirmed

AN ATTEMPT TO DEFINE CONTEXT AWARENESS IN MOBILE E-HEALTH ENVIRONMENTS

Nurses, doctors, physiotherapists, psychologists and other professionals or specialists come together to provide care to home residing patients, making continuous assessment, diagnosis and treatment possible beyond the walls of hospitals. Such teams of professionals are focused on each individual patient, and are virtual, i.e. they make decisions without being together physically, dynamically, i.e. professionals come and go as needed, and collaborate, as they combine their knowledge to provide effective care. Our system, coined DITIS, is a web based system that enables the effective management and collaboration of virtual healthcare teams and accessing medical information in a secure manner from a variety of mobile devices from anytime and anyplace, adapting the information according to various parameters like, user role, access right, device capabilities and wireless medium. This paper introduces the DITIS system, and identifies the needs and challenges of co-ordinated teams of multidisciplinary healthcare professionals (HCPs) functioning in a context awareness environment under the wireless environment. Pilo

Definition, implementation and validation of energy code smells: an exploratory study on an embedded system

Optimizing software in terms of energy efficiency is one of the challenges that both research and industry will have to face in the next few years.We consider energy efficiency as a software product quality characteristic, to be improved through the refactoring of appropriate code pattern: the aim of this work is identifying those code patterns, hereby defined as Energy Code Smells, that might increase the impact of software over power consumption. For our purposes, we perform an experiment consisting in the execution of several code patterns on an embedded system. These code patterns are executed in two versions: the first one contains a code issue that could negatively impact power consumption, the other one is refactored removing the issue. We measure the power consumption of the embedded device during the execution of each code pattern. We also track the execution time to investigate whether Energy Code Smells are also Performance Smells. Our results show that some Energy Code Smells actually have an impact over power consumption in the magnitude order of micro Watts. Moreover, those Smells did not introduce a performance decreas

File Tracking For Mobile Devices

Since 2010, the smart device has become an integral part of people’s daily lives. The popularity of smart devices has increased dramatically. However, as the number of devices owned by an individual user increases, so does the risk of data leakage and loss. This problem has started to draw attention because the data contained on smart devices tends to be personal or sensitive in nature. Many people have so much data on their devices that they have no idea as to what they are missing when a device is lost. Although there are already some solutions for data recovery, a data backup system on a remote server, these solutions are not accessible in the non-Internet environment. Development of a data recovery system that is accessible in the non-Internet environment is essential because of the constraints of mobile devices, such as unreliable network. This research proposes an architecture that allows the data recovery in both Internet (cloud) and Non-Internet (local) network by using different connection technologies. A data tracking mechanism has also been designed to monitor data flow among multiple devices, such as the cloud server, mobile devices, and tablets. Additionally, a synchronization system has been developed to ensure the consistency of tracking information. By designing and implementing this architecture, the two problems regarding to the data: "what is where" and "who has what" are resolved