1,720,999 research outputs found
VET, an Epidemic Transport Protocol for Retrieving Multimedia Contents in Vehicular Networks
No full textDesign and evaluation of a collaborative system for content diffusion and retrieval in vehicular networks
No full textThe availability of infotainment contents to be accessed while driving constitutes an added value to both drivers and passengers, improving their travel experience. These contents can be already on-board, diffused through broadcast networks (e.g., FM radio) or delivered on demand by servers as data streams. Vehicular ad-hoc networks (VANET) allow envisaging a new way to access contents based on epidemic data dissemination, tearing down the costs for both the user and the content publisher, and increasing system scalability. In this paper, we present the design and the evaluation of a collaborative system for content diffusion and retrieval among traveling vehicles. This system relies on multicast epidemic dissemination of messages and exploits vehicles mobility and their local storage capabilities. In order to assess its performance, several simulations have been carried out, using real-world maps and realistic mobility models, and varying intrinsic system parameters. Experimental results suggest that the system is feasible, produces reliable results, almost independent of the mobility scenario, and can be used as a peer-to-peer download accelerator for improving client-server acces
Epidemic information diffusion in realistic vehicular network mobility scenarios
No full textEpidemic or gossip-based algorithms have been proposed for data dissemination in vehicular networks. Due to the unfeasibility of deploying large size vehicular networks, the performance evaluation of these algorithms is usually based on simulations. However, most literature works present experimental results based on hyper-simplified and non-realistic mobility scenarios or do not adequately describe the simulation setup. In this paper, we investigate the impact that road-network and vehicle density have on the performance of epidemic dissemination and the correlation between these factors and other simulation parameters, such as percentage of equipped vehicles, message expiration time, scheduling algorithm for data retransmission and number of circulating messages. We argue that, given the high sensitivity of this kind of approach to mobility scenarios, it would be useful to define a set of them to be used as a reference for evaluating different systems. Furthermore, from our simulations, we can state that, although epidemic diffusion does not guarantee data distribution to all network nodes, its simplicity and lack of infrastructure make it suitable for distributing real-time traffic or viability data in most mobility scenarios
JThreadSpy: a Tool for Improving the Effectiveness of Concurrent System Teaching and Learning
No full textJThreadSpy: Teaching Multithreading Programming by Analyzing Execution Traces
No full textMultithreading introduces a degree of complexity that is often difficult to grasp by beginners both because of many false assumptions made about the scheduling process and because it is not possible to adopt a trial and error strategy aimed at figuring out what exactly happens during the execution, as a consequence of the intrinsic non determinism of threaded execution. This article describes JThreadSpy, a tool for dynamic instrumentation of Java programs, aimed at registering execution traces of each thread and displaying them with a selectable level of detail. JThreadSpy relies on the ASM framework to dynamically instrument methods during class loading, in order to insert suitable method calls that produce an execution trace that is later used to display an annotated UML sequence diagram, highlighting different threads and synchronization constructs. JThreadSpy proved to be a valuable tool for students engaged in an object-oriented programming course at Politecnico di Torino. By graphically analysing execution flows, students could understand, in an easier way, the non-determinism introduced by the scheduler, the effects of synchronization constructs, the impact of multicore processor architectures, as well as identify critical sections, deadlocks and other anomalies of concurrent program
Integrating a Location-Based Mobile Game in the Museum Visit: Evaluating Visitors’ Behaviour and Learning
No full textLocation-based systems currently represent a suitable solution to enhance cultural experiences inside museums, as they can
satisfy visitors’ needs through the provision of contextualized contents and services. In this framework, a promising approach to
captivate the attention of teenagers—a hard to please target audience—is represented by mobile serious games, such as playful
activities aiming to primarily fulfil educational purposes. The use of a mobile digital tool during the visit definitely discloses
new opportunities for contextual learning scenarios; however, so far, only a few studies have analysed the impact of different
communication approaches on visitors’ degree of exploration and acquisition of knowledge. This work aims to enrich this field
of research, presenting the conceptual framework; the design principles; and the evaluation results of “Gossip at palace,” a
location-based mobile game integrating a storytelling approach. The game was developed for an Italian historical residence
to communicate its 18th-century history to teenagers, capitalizing on narrative and game mechanics to foster young visitors’
motivations to explore the museum and facilitate their meaning-making process. Following a mixed-methods perspective, the
article firstly describes to what extent the components of the application were appreciated by teenagers as well as by other
visitor segments. Secondly, it provides an insight on the effectiveness of the game in facilitating the acquisition of historical
knowledge by participants, enriched by considerations on the methods to be adopted when evaluating mobile learning in informal
educational settings. Thirdly, players’ degree of use of the digital game throughout the visit is compared to analogous patterns
registered for people using a multimedia mobile guide in the same venue. On the one hand, the study pointed out that the game
facilitated a wider exploration of the museum; on the other, it highlighted that players mainly gained a superficial knowledge of
the proposed content
Mobile Communication and Localization Device
No full textThe invention relates to a mobile communication and localization device (1) cooperating with a plurality of mobile network devices (10-80) and comprising: a processing unit (2); a data structure containing a plurality of entries, each entry containing information about a corresponding mobile network device (10-80) and a corresponding time stamp; a unit (4) for sending data packets at respective transmission instants, each data packet containing position data indicating the position of corresponding mobile network devices (10-80); a unit (4) for receiving data packets sent by sender mobile devices (10-80) belonging to the plurality of mobile network devices (10-80); and a unit (190-310) for determining the relative position of corresponding mobile network devices (10-80) based on position data contained in the data packets
Experiencing indoor navigation on mobile devices
Full text linkRecently, indoor navigation on mobile devices has received attention from both startups and large vendors, since it has many relevant practical and commercial applications. User positioning and navigation using GPS signals is becoming more and more popular, mainly due to the increasing availability of acceptable quality sensors into low-cost consumer devices as smartphones. However, indoor GPS-navigation is highly unreliable because of the poor communication with satellites and the lack of detailed maps. In this paper we discuss the technologies allowing the indoor computation of accurate location and orientation data, as well as other issues and challenges that indoor navigation apps should cope with. In particular, we present and make explicit reference to a system for indoor navigation (running on a smartphone), which has been designed by the Authors, including the main problems that have been tackled during its implementation
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