Abstract-Due to the tremendous enhancements in the capabilities of mobile devices in recent years and accessibility to higher bandwidth mobile internet, the use of online multimedia learning resources on mobile devices is increasingly becoming popular. Improvements in battery capacity have not matched the same advancements compared to other features of mobile devices. Limited Battery power is introducing a significant challenge in making better use of online educational multimedia resources. Online Multimedia Resources drains more battery power as a result of higher amount of wireless data transfer and therefore limiting learning opportunities on the move. Many power saving multimedia adaptation techniques have been suggested. Majority of these techniques achieve battery efficiency while reducing multimedia quality. So far, however, to the best of our knowledge no previous effort has considered the factor of learning efficacy in multimedia adaptation process. Existing adaptation techniques are susceptible to information loss as a result of quality of reduction. Such loss affects the learning content efficacy and jeopardizes the learning process. In this paper, we recommend a novel power save educational multimedia adaptation approach that considers the learning aspect of multimedia in the adaptation process. Our technique enables learning for extended duration by battery power saving without putting the learning process at risk. Efficacy of entire learning resources is managed by not allowing any part of the learning multimedia to be delivered in a quality that will negatively affect the learning outcome. We also present a framework that guides the implementation of our approach followed by description of our prototype application that uses educational multimedia metadata implemented in semantic web technologies.

As a result of tremendous enhancements in the capabilities of mobile devices and availability of higher data rate mobile internet, the use of online multimedia learning resources on mobile devices is increasingly becoming popular. Limited Battery Power of mobile devices, however, is still one big challenge in Mobile Learning. High Quality multimedia learning resources are power hungry and if used on mobile devices drain battery power rapidly limiting learning opportunities on the move. Lack of significant improvements in battery capacities has resulted in significant interest in battery power saving techniques. Existing power-saving streaming multimedia adaptation techniques tend to extend battery life by reducing quality of multimedia making them susceptible to information loss. This loss may affect the learning content efficacy and jeopardizes the learning process. To the best of our knowledge, no previous work has considered the learning content efficacy in multimedia streaming adaptation mechanism. In this paper, we present MoBELearn system, which is a prototype implementation of our proposed Content Aware Power Saving Educational Multimedia Adaptation (CAPS-EMA) approach. We demonstrate battery efficiency in educational multimedia streaming while keeping the adapted resource suitable for learning. We also describe our semantic metamodel for educational multimedia resource that support our energy efficient adaptation technique.

Vehicular Ad hoc Networks (VANETs) are special kind of Mobile Ad hoc Networks (MANETs), where vehicles communicate with each other in ad hoc formation. VANETs consist of Vehicles and Road Side Units (RSUs) that assist in the network management. Vehicles communicate with each other and RSUs, with the aim to provide infotainment and safety services on road. Security is an important consideration in VANETs as safety of humans (passengers) is an important issue. Vehicular Public Key Infrastructure (VPKI) is an adapted form of PKI used to achieve the key management and security services in VANETs. Certificate generation and revocation is one of the primary functions of VPKI. Certificate revocation is used for revoking the malicious nodes and terminate its access rights to the network. In this paper we classify revocation schemes in a novel way into centralized and decentralized manners. This paper covers a survey of different certificate revocation schemes, and provides an overview of the research in the area of certificate revocation in VANETs.

Using online multimedia content on mobile devices is a power hungry activity and drains battery power very quickly. This poses a big challenge in using mobile devices with limited battery power for learning purposes using online educational multimedia. Multimedia adaptation techniques have been developed that preserve battery power by lowering multimedia quality. These adaptation techniques do not provide users with any power-saving options and the adaptation is done automatically without involvement of users. In this paper, we propose a Learner-Battery Interaction model that suggests involving learners in the adaptation process. The idea is to provide learners with powersaving options and relevant feedback about the form of adapted multimedia in advance. This will help leaners in making informed power-saving decisions for adaptation. We implemented the model in a prototype system and conducted an evaluation in the form of a user study.

As mobile devices are getting more powerful and more affordable the use of online educational multimedia is also getting very prevalent. Limited battery power is nevertheless a major restricting factor as streaming multimedia drains battery power quickly. Many battery efficient multimedia adaptation techniques have been proposed that achieve battery efficiency by lowering presentation quality of entire multimedia. Adaptation is usually done without considering any impact on the information contents of multimedia. In this paper, based on the results of an experimental study, we argue that without considering any negative impact on information contents of multimedia the adaptation may negatively impact the learning process. Some portions of the multimedia that require a higher visual quality for conveying learning information may lose their learning effectiveness in the adapted lowered quality. We report results of our experimental study that indicate that different parts of the same learning multimedia do not have same minimum acceptable quality. This strengthens the position that powersaving adaptation techniques for educational multimedia must be developed that lower the quality of multimedia based on the needs of its individual fragments for successfully conveying learning information.