1,721,429 research outputs found
A new model for network traffic forecast based on user's mobility in cellular networks with highway stretches
No full textWireless communications have always faced the scarceness of bandwidth and until today the cellular division has solved this problem by making radio cells always smaller. However, as cell size is reduced, more users will probably require handoffs, and signaling can overload the system. Further, the decrease in cell dimension cannot ensure the best utilization of system resources, because user density in the cell is not constant over the time. Dynamic allocation might be the solution, but it is a complex task, basically due to complexity of the models for the mobility prediction, especially in those environments where users move very fast (e.g. highways). This last one is a typical environment where high mobility of vehicles does not allow small cell sizes and thus system capacity is intrinsically bounded.
In this paper, we deploy an analytical model for a cellular network operating in a high mobility environment. Such a model is capable of representing and forecasting wireless system evolution in terms of channel occupancy, starting from the current state of the mobile network and road traffic. This model has been defined by integrating a vehicular traffic model with a wireless cellular communication one. With such approach the dynamic behaviour of the most critical mobile terminals, those associated with vehicles, are described in a very precise and specific way with respect to mobility
An Integrated Mobility Framework for Ad-Hoc Distributed Personal Networks
No full textAdvances in wireless communications have driven an interest towards ubiquitous computing environments for nomadic users. This has led to a more user-centric vision of the network and to the concept of personal network: the user exploits his personal devices (both local and remote) and those in the surrounding environment to build dynamic ad hoc communication systems for the best experience in enjoying multimedia. In this paper, we propose a mobility framework for personal networks based on the idea of a 'personal mobile address' to bind a network address to the user rather than to a network interface, allowing the address to follow the user as he moves. We show how this mobility framework could be used for real-time interactive communications, in particular for voice-over-IP sessions managed by SIP. Moreover, we sketch a software architecture for this framework and evaluate its feasibility by means of a prototype
Piccole scuole e rapporti scuola-genitori tra legami con la tradizione e spinte all’innovazione
Full text linkThis paper is focused on parent-school relationships within small schools. Till now, even at international level, studies concerning specifically parentschool relationships are still few, while the majority of research on this theme is achieved in urban or suburban contexts. After an international literature review on school families relationships in small schools, the main results from a research realized in some small schools of the Piedmontese mountains during 2017/2018 and 2018/2019 scholastic years. Questo contributo si focalizza sui rapporti scuola genitori nelle piccole scuole. Ad ora, anche a livello internazionale, sono pochi gli studi che riguardano nello specifico i rapporti scuola genitori nelle piccole scuole, mentre la maggior parte delle ricerche sul tema è stata condotta in contesti urbani o suburbani. Dopo una rassegna sulla letteratura internazionale relativa ai rapporti scuola genitori nelle piccole scuole verranno presentati i principali risultati emersi da una ricerca realizzata nelle piccole scuole delle montagne piemontesi negli anni scolastici 2017/2018 e 2018/2019
Coupling energy efficiency and quality for consolidation of cloud workloads
No full textEfficient usage of IT equipment in Data Centers requires modulating their power-consumption according to the actual workload. The most effective strategy to this aim consists in consolidating as many applications as possible on the smallest number of servers, so that idle devices can be shut down or put in low-power states. Usually, this process is driven by computing and networking resources requested by each application (e.g., CPU and RAM) and applies a certain degree of overcommitment, assuming that such resources are not fully used continuously. However, this approach is critical with real workload patterns, which usually change over time; as a matter of fact, consolidation in real scenarios often leads to either low efficiency or violations of Quality of Service (QoS) constraints, depending on the level of overcommitment. In this paper, we investigate a novel consolidation strategy based on an enhanced system model for the Infrastructure-as-a-Service cloud paradigm, which targets a better trade-off between Energy Efficiency and Quality of Service. We explicitly target modular cloud applications, which design is split into multiple components deployed in Virtual Machine (VM)s or containers. Our consolidation strategy allows to “freeze” parts of the application which are not currently used, making them available when requested with minimal latency. This improves energy saving with respect to other approaches, especially when idle VMs are present for backup or redundancy purposes, without degrading the service level. We compare multiple heuristics available in Optaplanner to solve our consolidation problem, and investigate improvements with respect to a more traditional approach. Our evaluation includes both simulations and experimentation in a real test-bed. The comparison shows that the Late Acceptance algorithm on average finds better solutions than other alternatives and energy efficiency improves up to 40% with respect to more conventional strategies, with deterioration of QoS indexes below 1%
Piccola scuola come comunità educante
No full textStrumenti sono linee guida e schede operative per il lavoro in classe che nascono generalmente dal lavoro di co-ricerca tra le scuole e l’Indire e dalle esperienze formative su specifici metodi e tecniche di lavoro sperimentate in situazioni di isolamento e pluriclassi
Cloud Applications Consolidation through Context Information and Heuristic Optimization
No full textResource consolidation has been proposed as an effective mechanism to save energy in data centers. Several algorithms have been developed for this purpose, which use the minimal number of servers and network switches, and power off unused equipment. Consolidation algorithms usually take into account static service constraints (Central Processing Unit CPU, Random Access Memory RAM, disk, bandwidth), but do not consider dynamic context information, as CPU utilization and the specific role of each Virtual Machines (VMs) in the running application (e.g., core component, backup replica, member of a pool of workers for load balancing).In this paper, we describe and evaluate a novel heuristic based consolidation strategy that explicitly considers context information. Our approach avoids running idle VMs that are pre-provisioned for availability and redundancy purposes, hence pursuing a better linear relationship between power consumption and actual computation than other existing algorithms. We demonstrate through simulations, by comparing different heuristics, the optimal trade-off between service level and energy efficiency achieved by our approach
Comunità di pratica e formazione degli insegnanti
No full textThis paper presents a comparative analysis of four communities of practice aimed at teacher training activities. The communities were chosen on the basis of their emblematic qualities (i.e. for their emblematic development and their activities). A review of the concept of “community of practice” in teacher training as it appears in international literature is presented. An analysis of the four communities of practice will be conducted following Wenger’s categories of domain, practice and social learning (Wenger 2006). The objective of the present paper is to provide a practical example of a possible use of Wenger’s categories in communities of practice for teacher training, so that schoolmasters and teachers have a tool to analyse and compare different communities for teacher training
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