Mobile Agents for Mobile Tourists: A User Evaluation of Gulliver's Genie

How mobile computing applications and services may be best designed, implemented and deployed remains the subject of much research. One alternative approach to developing software for mobile users that is receiving increasing attention from the research community is that of one based on intelligent agents. Recent advances in mobile computing technology have made such an approach feasible. We present an overview of the design and implementation of an archetypical mobile computing application, namely that of an electronic tourist guide. This guide is unique in that it comprises a suite of intelligent agents that conform to the strong intentional stance. However, the focus of this paper is primarily concerned with the results of detailed user evaluations conducted on this system. Within the literature, comprehensive evaluations of mobile context-sensitive systems are sparse and therefore, this paper seeks, in part, to address this deficiency

Caching Techniques in Next Generation Cellular Networks

Content caching will be an essential feature in the next generations of cellular networks. Indeed, a network equipped with caching capabilities allows users to retrieve content with reduced access delays and consequently reduces the traffic passing through the network backhaul. However, the deployment of the caching nodes in the network is hindered by the following two challenges. First, the storage space of a cache is limited as well as expensive. So, it is not possible to store in the cache every content that can be possibly requested by the user. This calls for efficient techniques to determine the contents that must be stored in the cache. Second, efficient ways are needed to implement and control the caching node. In this thesis, we investigate caching techniques focussing to address the above-mentioned challenges, so that the overall system performance is increased. In order to tackle the challenge of the limited storage capacity, smart proactive caching strategies are needed. In the context of vehicular users served by edge nodes, we believe a caching strategy should be adapted to the mobility characteristics of the cars. In this regard, we propose a scheme called RICH (RoadsIde CacHe), which optimally caches content at the edge nodes where connected vehicles require it most. In particular, our scheme is designed to ensure in-order delivery of content chunks to end users. Unlike blind popularity decisions, the probabilistic caching used by RICH considers vehicular trajectory predictions as well as content service time by edge nodes. We evaluate our approach on realistic mobility datasets against a popularity-based edge approach called POP, and a mobility-aware caching strategy known as netPredict. In terms of content availability, our RICH edge caching scheme provides an enhancement of up to 33% and 190% when compared with netPredict and POP respectively. At the same time, the backhaul penalty bandwidth is reduced by a factor ranging between 57% and 70%. Caching node is an also a key component in Named Data Networking (NDN) that is an innovative paradigm to provide content based services in future networks. As compared to legacy networks, naming of network packets and in-network caching of content make NDN more feasible for content dissemination. However, the implementation of NDN requires drastic changes to the existing network infrastructure. One feasible approach is to use Software Defined Networking (SDN), according to which the control of the network is delegated to a centralized controller, which configures the forwarding data plane. This approach leads to large signaling overhead as well as large end-to-end (e2e) delays. In order to overcome these issues, in this work, we provide an efficient way to implement and control the NDN node. We propose to enable NDN using a stateful data plane in the SDN network. In particular, we realize the functionality of an NDN node using a stateful SDN switch attached with a local cache for content storage, and use OpenState to implement such an approach. In our solution, no involvement of the controller is required once the OpenState switch has been configured. We benchmark the performance of our solution against the traditional SDN approach considering several relevant metrics. Experimental results highlight the benefits of a stateful approach and of our implementation, which avoids signaling overhead and significantly reduces e2e delays