Institutional Repositories: Features, Architecture, Design and Implementation Technologies

Europe is the leading continent in terms of active adoption and use of Digital Libraries – particularly Institutional Repositories (IRs). Africa has not done poorly in this area with a steady increase from 19 repositories in 2008 to 46 in January, 2011 but there is need to raise awareness and channel efforts towards making IRs easily accessible to Africans through ubiquitous channels such as hand-helds and mobile devices. This paper reviews the features, architecture, design and implementation technologies of IRs. In addition, it highlights viable research areas that can be pursued by African researchers in the field of Digital Libraries. It also encourages research efforts to focus on areas that will be beneficial to Africa

Cooperative Data Backup for Mobile Devices

Les dispositifs informatiques mobiles tels que les ordinateurs portables, assistants personnels et téléphones portables sont de plus en plus utilisés. Cependant, bien qu'ils soient utilisés dans des contextes où ils sont sujets à des endommagements, à la perte, voire au vol, peu de mécanismes permettent d'éviter la perte des données qui y sont stockées. Dans cette thèse, nous proposons un service de sauvegarde de données coopératif pour répondre à ce problème. Cette approche tire parti de communications spontanées entre de tels dispositifs, chaque dispositif stockant une partie des données des dispositifs rencontrés. Une étude analytique des gains de cette approche en termes de sûreté de fonctionnement est proposée. Nous étudions également des mécanismes de stockage réparti adaptés. Les problèmes de coopération entre individus mutuellement suspicieux sont également abordés. Enfin, nous décrivons notre mise en oeuvre du service de sauvegarde coopérative. ABSTRACT : Mobile devices such as laptops, PDAs and cell phones are increasingly relied on but are used in contexts that put them at risk of physical damage, loss or theft. However, few mechanisms are available to reduce the risk of losing the data stored on these devices. In this dissertation, we try to address this concern by designing a cooperative backup service for mobile devices. The service leverages encounters and spontaneous interactions among participating devices, such that each device stores data on behalf of other devices. We first provide an analytical evaluation of the dependability gains of the proposed service. Distributed storage mechanisms are explored and evaluated. Security concerns arising from thecooperation among mutually suspicious principals are identified, and core mechanisms are proposed to allow them to be addressed. Finally, we present our prototype implementation of the cooperative backup servic

Framework for Content Distribution over Wireless LANs

Wireless LAN (also called as Wi-Fi) is dominantly considered as the most pervasive technology for Intent access. Due to the low-cost of chipsets and support for high data rates, Wi-Fi has become a universal solution for ever-increasing application space which includes, video streaming, content delivery, emergency communication, vehicular communication and Internet-of-Things (IoT). Wireless LAN technology is defined by the IEEE 802.11 standard. The 802.11 standard has been amended several times over the last two decades, to incorporate the requirement of future applications. The 802.11 based Wi-Fi networks are infrastructure networks in which devices communicate through an access point. However, in 2010, Wi-Fi Alliance has released a specification to standardize direct communication in Wi-Fi networks. The technology is called Wi-Fi Direct. Wi-Fi Direct after 9 years of its release is still used for very basic services (connectivity, file transfer etc.), despite the potential to support a wide range of applications. The reason behind the limited inception of Wi-Fi Direct is some inherent shortcomings that limit its performance in dense networks. These include the issues related to topology design, such as non-optimal group formation, Group Owner selection problem, clustering in dense networks and coping with device mobility in dynamic networks. Furthermore, Wi-Fi networks also face challenges to meet the growing number of Wi Fi users. The next generation of Wi-Fi networks is characterized as ultra-dense networks where the topology changes frequently which directly affects the network performance. The dynamic nature of such networks challenges the operators to design and make optimum planifications. In this dissertation, we propose solutions to the aforementioned problems. We contributed to the existing Wi-Fi Direct technology by enhancing the group formation process. The proposed group formation scheme is backwards-compatible and incorporates role selection based on the device's capabilities to improve network performance. Optimum clustering scheme using mixed integer programming is proposed to design efficient topologies in fixed dense networks, which improves network throughput and reduces packet loss ratio. A novel architecture using Unmanned Aeriel Vehicles (UAVs) in Wi-Fi Direct networks is proposed for dynamic networks. In ultra-dense, highly dynamic topologies, we propose cognitive networks using machine-learning algorithms to predict the network changes ahead of time and self-configuring the network

Competitive Evolutionary Dynamics of Cloud Service Offerings in Korea: A Path-Dependency Perspective

Cloud service for personal users has become more popular world-wide since Apple Inc. launched iCloud storage service in October, 2011. However, such cloud storage service was not new because many global telecom companies, usually called telcos, as well as many portals had already offered similar Internet-based online storage services at that time. As of now, there can be seen hundreds of diverse cloud storage and computing services for both personal and enterprise users in the global market. During last several years, Korean cloud service market has been led by three major telcos, who have launched more advanced and more diversified services competing with each other. Some questions may arise: What makes that happen and what kind of market dynamics affects on the evolution of cloud service offerings? This paper tries to answer these questions by categorizing and analysing 84 cloud services offered by three major telcos in Korea during last three years. As a research framework, Pessemier’s new product classification scheme was employed and precedence relationships among differently positioned service categories were analyzed to figure out the competitive evolutionary dynamics of the market. From the empirical study, path dependency was observed and resource-based view of the market competition was validated. Also, it was found that a player’s next move in service offering to a better position in Pessemier’s product space is quite closely related with the competitive position as well as the company-owned competitive resources like technology competency and company-wide service scope

A novel MAC Protocol for Cognitive Radio Networks

In Partial Fulfilment of the Requirements for the Degree Doctor of Philosophy from the University of BedfordshireThe scarcity of bandwidth in the radio spectrum has become more vital since the demand for wireless applications has increased. Most of the spectrum bands have been allocated although many studies have shown that these bands are significantly underutilized most of the time. The problem of unavailability of spectrum bands and the inefficiency in their utilization have been smartly addressed by the cognitive radio (CR) technology which is an opportunistic network that senses the environment, observes the network changes, and then uses knowledge gained from the prior interaction with the network to make intelligent decisions by dynamically adapting transmission characteristics. In this thesis, recent research and survey about the advances in theory and applications of cognitive radio technology has been reviewed. The thesis starts with the essential background on cognitive radio techniques and systems and discusses those characteristics of CR technology, such as standards, applications and challenges that all can help make software radio more personal. It then presents advanced level material by extensively reviewing the work done so far in the area of cognitive radio networks and more specifically in medium access control (MAC) protocol of CR. The list of references will be useful to both researchers and practitioners in this area. Also, it can be adopted as a graduate-level textbook for an advanced course on wireless communication networks. The development of new technologies such as Wi-Fi, cellular phones, Bluetooth, TV broadcasts and satellite has created immense demand for radio spectrum which is a limited natural resource ranging from 30KHz to 300GHz. For every wireless application, some portion of the radio spectrum needs to be purchased, and the Federal Communication Commission (FCC) allocates the spectrum for some fee for such services. This static allocation of the radio spectrum has led to various problems such as saturation in some bands, scarcity, and lack of radio resources to new wireless applications. Most of the frequencies in the radio spectrum have been allocated although many studies have shown that the allocated bands are not being used efficiently. The CR technology is one of the effective solutions to the shortage of spectrum and the inefficiency of its utilization. In this thesis, a detailed investigation on issues related to the protocol design for cognitive radio networks with particular emphasis on the MAC layer is presented. A novel Dynamic and Decentralized and Hybrid MAC (DDH-MAC) protocol that lies between the CR MAC protocol families of globally available common control channel (GCCC) and local control channel (non-GCCC). First, a multi-access channel MAC protocol, which integrates the best features of both GCCC and non-GCCC, is proposed. Second, an enhancement to the protocol is proposed by enabling it to access more than one control channel at the same time. The cognitive users/secondary users (SUs) always have access to one control channel and they can identify and exploit the vacant channels by dynamically switching across the different control channels. Third, rapid and efficient exchange of CR control information has been proposed to reduce delays due to the opportunistic nature of CR. We have calculated the pre-transmission time for CR and investigate how this time can have a significant effect on nodes holding a delay sensitive data. Fourth, an analytical model, including a Markov chain model, has been proposed. This analytical model will rigorously analyse the performance of our proposed DDH-MAC protocol in terms of aggregate throughput, access delay, and spectrum opportunities in both the saturated and non-saturated networks. Fifth, we develop a simulation model for the DDH-MAC protocol using OPNET Modeler and investigate its performance for queuing delays, bit error rates, backoff slots and throughput. It could be observed from both the numerical and simulation results that when compared with existing CR MAC protocols our proposed MAC protocol can significantly improve the spectrum utilization efficiency of wireless networks. Finally, we optimize the performance of our proposed MAC protocol by incorporating multi-level security and making it energy efficient

Resilient architecture (preliminary version)

The main objectives of WP2 are to define a resilient architecture and to develop a range of middleware solutions (i.e. algorithms, protocols, services) for resilience to be applied in the design of highly available, reliable and trustworthy networking solutions. This is the first deliverable within this work package, a preliminary version of the resilient architecture. The deliverable builds on previous results from WP1, the definition of a set of applications and use cases, and provides a perspective of the middleware services that are considered fundamental to address the dependability requirements of those applications. Then it also describes the architectural organisation of these services, according to a number of factors like their purpose, their function within the communication stack or their criticality/specificity for resilience. WP2 proposes an architecture that differentiates between two classes of services, a class including timeliness and trustworthiness oracles, and a class of so called complex services. The resulting architecture is referred to as a "hybrid architecture". The hybrid architecture is motivated and discussed in this document. The services considered within each of the service classes of the hybrid architecture are described. This sets the background for the work to be carried on in the scope of tasks 2.2 and 2.3 of the work package. Finally, the deliverable also considers high-level interfacing aspects, by providing a discussion about the possibility of using existing Service Availability Forum standard interfaces within HIDENETS, in particular discussing possibly necessary extensions to those interfaces in order to accommodate specific HIDENETS services suited for ad-hoc domain

A Design Rationale for Pervasive Computing - User Experience, Contextual Change, and Technical Requirements

The vision of pervasive computing promises a shift from information technology per se to what can be accomplished by using it, thereby fundamentally changing the relationship between people and information technology. In order to realize this vision, a large number of issues concerning user experience, contextual change, and technical requirements should be addressed. We provide a design rationale for pervasive computing that encompasses these issues, in which we argue that a prominent aspect of user experience is to provide user control, primarily founded in human values. As one of the more significant aspects of the user experience, we provide an extended discussion about privacy. With contextual change, we address the fundamental change in previously established relationships between the practices of individuals, social institutions, and physical environments that pervasive computing entails. Finally, issues of technical requirements refer to technology neutrality and openness--factors that we argue are fundamental for realizing pervasive computing. We describe a number of empirical and technical studies, the results of which have helped to verify aspects of the design rationale as well as shaping new aspects of it. The empirical studies include an ethnographic-inspired study focusing on information technology support for everyday activities, a study based on structured interviews concerning relationships between contexts of use and everyday planning activities, and a focus group study of laypeople’s interpretations of the concept of privacy in relation to information technology. The first technical study concerns the model of personal service environments as a means for addressing a number of challenges concerning user experience, contextual change, and technical requirements. Two other technical studies relate to a model for device-independent service development and the wearable server as a means to address issues of continuous usage experience and technology neutrality respectively