Search results for " telecomunicazioni"
showing 10 items of 245 documents
The Risks of WiFi Flexibility: Enabling and Detecting Cheating
2013
Flexibility is an important paradigm for future WiFi networks. However, it also opens the possibility for diverse methods of cheating, which users can perform to increase their throughput. Therefore, it is important to develop the necessary tools to mitigate such efforts. In this paper we first discuss the risks of flexibility in terms of misbehaviour. We then propose an architecture to detect misbehaviour and react by punishing the cheaters. The proposed architecture utilizes advanced passive monitoring, flexible WiFi software, and appropriate reasoning to detect cheating. We validate its performance and discuss means of punishment
A game theoretic approach to MAC design for infrastructure networks
2010
Wireless network operation intrinsically assumes different forms of cooperation among the network nodes, such as sharing a common wireless medium without interfering, relaying frames belonging to other nodes, controlling the transmission power for optimizing spectrum reuse, coding cooperatively multiple frames for improving information redundancy, and so on. For this reason, Game Theory has been extensively employed to model wireless networks. In particular, we propose a game-theoretic approach for defining a generalized medium access protocol for slotted contention-based channels. Contention-based channels are largely adopted in data networks, e.g. in WiFi and WiMax networks and in some em…
Moving RTS/CTS to the frequency domain: an efficient contention scheme for 802.11ax networks
2019
In this paper, we propose a contention mechanism based on the execution of multiple contention rounds in the frequency domain (ReCHo), which is designed to offer high throughput performance and robustness with respect to imperfect carrier sensing. The main idea is using narrow tones as signalling messages for performing channel access contentions and allowing the Access Point (AP) to echo these signals, in order to extend the sensing capabilities to all the stations associated to the AP. In particular, we refer to the emerging IEEE 802.11ax standard, showing how our scheme can boost performance of random access with respect to the current version of IEEE 802.11ax OFDMA Back-Off (OBO), even …
'Good to Repeat': Making Random Access Near-Optimal with Repeated Contentions
2020
Recent advances on WLAN technology have been focused mostly on boosting network capacity by means of a more efficient and flexible physical layer. A new concept is required at MAC level to exploit fully the new capabilities of the PHY layer. In this article, we propose a contention mechanism based on Repeated Contentions (ReCo) in frequency domain. It provides a simple-to-configure, robust and short-term fair algorithm for the random contention component of the MAC protocol. The throughput efficiency of ReCo is not sensitive to the number of contending stations, so that ReCo does not require adaptive tuning of the access parameters for performance optimization. Efficiency and robustness is …
Sistema di posizionamento geo-spaziale cooperativo operante con sistemi di navigazione globale satellitare e reti di telecomunicazione wireless, rela…
2010
ARIANNA: pAth Recognition for Indoor Assisted NavigatioN with Augmented perception
2013
ARIANNA stands for pAth Recognition for Indoor Assisted Navigation with Augmented perception. It is a flexible and low cost navigation system for vi- sually impaired people. Arianna permits to navigate colored paths painted or sticked on the floor revealing their directions through vibrational feedback on commercial smartphones.
A Navigation and Augmented Reality System for Visually Impaired People
2021
In recent years, we have assisted with an impressive advance in augmented reality systems and computer vision algorithms, based on image processing and artificial intelligence. Thanks to these technologies, mainstream smartphones are able to estimate their own motion in 3D space with high accuracy. In this paper, we exploit such technologies to support the autonomous mobility of people with visual disabilities, identifying pre-defined virtual paths and providing context information, reducing the distance between the digital and real worlds. In particular, we present ARIANNA+, an extension of ARIANNA, a system explicitly designed for visually impaired people for indoor and outdoor localizati…
BusyBee: Low Rate WiFi-ZigBee Communications without Gateways
2014
Nowadays, the overcrowding of ISM bands is becoming an evident limitation for the performance and widespread us- age of 802.11 and 802.15.4 technologies. In this demo, we prove that it is possible to opportunistically exploit the inter- technology interference between 802.11 and 802.15.4 to build an unconventional low-rate communication channel and sig- nalling protocol, devised to improve the performance of each contending technology. Differently from previous solutions, inter-technology communications do not require the deploy- ment of a gateway with two network interfaces, but can be activated (when needed) directly between two heterogeneous nodes, e.g. a WiFi node and a ZigBee node. Thi…
Optical turbulence measurements and channel modeling of an indoor Free Space Optics link (Versione estesa)
2014
In this work, we propose an indoor experimental set-up able to generate several optical turbulence conditions in a Free Space Optics link. Using this set-up, we prove the effectiveness of an irradiance time-series generator based on the Gamma-Gamma model and able to predict the irradiance fluctuations at the receiver, under both weak and moderate turbulence conditions.