Search results for "Distributed"

The quest for bandwidth estimation techniques for large-scale distributed systems

2010

In recent years the research community has developed many techniques to estimate the end-to-end available bandwidth of an Internet path. This important metric can be potentially exploited to optimize the performance of several distributed systems and, even, to improve the effectiveness of the congestion control mechanism of TCP. Thus, it has been suggested that some existing estimation techniques could be used for this purpose. However, existing tools were not designed for large-scale deployments and were mostly validated in controlled settings, considering only one measurement running at a time. In this paper, we argue that current tools, while offering good estimates when used alone, migh…

Coexistence between IEEE802.15.4 and IEEE802.11 through cross-technology signaling

2017

When different technologies use the same frequency bands in close proximity, the resulting interference typically results in performance degradation. Coexistence methods exist, but these are often technology specific and requiring technology specific interference detection methods. To remove the root cause of the performance degradation, devices should be able to negotiate medium access even when using different technologies. To this end, this paper proposes an architecture that allows crosstechnology medium access by means of a Time Division Multiple Access (TDMA) scheme. In order to achieve cross-technology synchronization, which is required for the TDMA solution, an energy pattern beacon…

Distributed Authentication and Authorization Architecture for Multi-service, Multi-provider Networks

2007

MAC design on real 802.11 devices: From exponential to Moderated Backoff

2016

In this paper we describe how a novel backoff mechanism called Moderated Backoff (MB), recently proposed as a standard extension for 802.11 networks, has been prototyped and experimentally validated on a commercial 802.11 card before being ratified. Indeed, for performance reasons, the time critical operations of MAC protocols, such as the backoff mechanism, are implemented into the card hardware/firmware and cannot be arbitrarily changed by third parties or by manufacturers only for experimental reasons. Our validation has been possible thanks to the availability of the so called Wireless MAC Processor (WMP), a prototype of a novel wireless card architecture in which MAC protocols can be p…

Coloring-based resource allocations in ad-hoc wireless networks

2011

It is well known that CSMA/CA protocols exhibit very poor performance in case of multi-hop transmissions, because of inter-link interference due to imperfect carrier sensing. We propose to control such an interference by preallocating temporal slots in which different sets of network nodes are allowed to contend for the channel access. The approach is based on distributed coloring algorithms with limited signaling overhead that can be customized as a function of the network topology and traffic load.

Logical Consensus for Distributed Network Agreement

2008

In this paper we introduce a novel consensus mechanism where agents of a network are able to share logical values, or Booleans, representing their local opinions on e.g. the presence of an intruder or of a fire within an indoor environment. Under suitable joint conditions on agents? visibility and communication capability, we provide an algorithm generating a logical linear consensus system that is globally stable. The solution is optimal in terms of the number of messages to be exchanged and the time needed to reach a consensus. Moreover, to cope with possible sensor failure, we propose a second design approach that produces robust logical nonlinear consensus systems tolerating a maximum n…

Virtual Vehicles Manager: a Java Virtual Reality Environment for Distributed Multi Vehicles Dynamics Control and Simulation

2007

Pervasive Displays Research: What's Next?

2019

Reports on the 7th ACM International Symposium on Pervasive Displays that took place from June 6-8 in Munich, Germany.

Human-to-Human Interaction: The Killer Application of Ubiquitous Computing?

2017

Twenty-five years past the Weiser’s vision of Ubiquitous Computing, and there is not a clear understanding of what is or is not a pervasive system. Due to the loose boundaries of such paradigm, almost any kind of remotely ac-cessible networked system is classified as a pervasive system. We think that that is mainly due to the lack of killer applications that could make this vi-sion clearer. Actually, we think that the most promising killer application is already here, but we are so used to it that we do not see it, as a perfect fitting of the Weiser’s vision: the Human-to-Human Interaction mediated by com-puters.

A Platform for the Evaluation of Distributed Reputation Algorithms

2018

In distributed environments, where unknown entities cooperate to achieve complex goals, intelligent techniques for estimating agents' truthfulness are required. Distributed Reputation Management Systems (RMSs) allow to accomplish this task without the need for a central entity that may represent a bottleneck and a single point of failure. The design of a distributed RMS is a challenging task due to a multitude of factors that could impact on its performances. In order to support the researcher in evaluating the RMS robustness against security attacks since its beginning design phase, in this work we present a distributed simulation environment that allows to model both the agent's behaviors…