Content-aware power saving multimedia adaptation for mobile learning

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

Energy-Aware Streaming Multimedia Adaptation: An Educational Perspective

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 power-saving 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 informatio

Educational multimedia adaptation for power-saving in mobile learning

Limited-battery power is a major constraint in mobile learning. It is important to adopt battery power-saving mechanisms in mobile learning applications in order to extend the duration of learning activities. This thesis explores issues related to power-saving in mobile learning. Streaming of online educational multimedia on mobile devices is a power hungry activity due to large amount of wireless data transfer. A number of power-saving multimedia adaptation techniques for streaming multimedia have been developed in the past. Most of these existing approaches achieve power-saving by uniformly lowering the presentation quality of an entire multimedia stream. These generic techniques will typically lower the visual quality of an entire multimedia stream uniformly, without considering its impact on perceived loss of visual information at different points of the multimedia stream.In this thesis, through a user study we suggest that reducing the quality of educational multimedia beyond a certain level - for power-saving adaptation - can cause perceived loss of visual information in quality-sensitive portions of a multimedia. This could have a negative impact on perceived learning effects and leave the resource unsuitable for learning. The results of the study suggest that different parts of a learning multimedia may have different lowest acceptable presentation quality requirements for avoiding perceived loss of visual information. The participants of the study were able to comprehend visual information in one fragment at a lower visual quality but could not comprehend visual information of some other fragments at the same quality level. To address this problem, we proposed a Content-Aware Power Saving Educational Multimedia Adaptation (CAPS-EMA) approach that suggests a way of delivering each portion of a multimedia in a lowest acceptable quality based on the visual contents of each fragment. We demonstrate an implementation of this approach using a prototype system called MoBELearn. The results of our evaluation studies suggest that the way CAPS-EMA adapts multimedia resources is acceptable to users in power-saving situations. CAPS-EMA requires some authoring processes in order to identify fragments and lowest acceptable quality constraints. An expert evaluation described the activities involved in the authoring process as easy to understand and performPower-saving multimedia adaptation mostly results in some compromises in terms of visual quality and information content. Existing techniques offer users little control over the adaptation process and they are obliged to accept the consequences of the adaptation. We propose a Learner Battery Interaction (LBI) mechanism that suggests offering users power-saving options and relevant feedback about the expected compromises for each power-saving option. This would enable users to make informed choices about power-saving. We evaluated the concept of LBI through a user study. The results of the study suggest a positive perceived usefulness of the system and that mobile learning applications may benefit from the idea.In the end, we propose a search mechanism for online adaptive learning resources that would help find a personalised learning resource that would fulfil the information needs of a learner in a battery-efficient way. This proposed mechanism is based on the concept of discovery of online open adaptive learning resources. For this purpose, we proposed an ontology model to describe adaptive learning resources, in terms of its adaptive features: learning and presentation features. This model could be used as a basis for implementing the proposed concept of the discovery of versions of adaptive learning resources in order to enable learners to engage in learning activities in a battery-efficient way by searching for online learning resources

Learner-Battery Interaction in Energy-Aware Learning Multimedia Systems

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 power-saving options and relevant feedback about the form of adapted multimedia in advance. This will help learners 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

Certificate revocation in vehicular ad hoc networks techniques and protocols: a survey

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 Public Key Infrastructure (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 their 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