Search results for "wifi"
showing 10 items of 30 documents
Studio di tecnologie radio per reti wifi con applicazioni a sistemi di diagnostica implementati su architetture chain e a grafo.
2011
RSS-eye: Human-assisted Indoor Localization without Radio Maps
2015
The pervasive diffusion of smartphones is boosting indoor positioning solutions and location-based services. We propose a novel methodology to perform indoor positioning of mobile users by the estimation of angles of arrival from access points whose locations are known. Angles of arrival are estimated by correlating WiFi RSSI measurements with data coming from a digital compass, which is provided by most current handsets. Our system has minimal requirements in terms of infrastructure and mobile hardware. The system neither needs calibration, nor radio maps but requires the user to perform a gesture when an estimation is needed. The resulting on-demand localization has advantages in terms of…
Analysis of the efficacy of a WiFi architecture for the management of medium voltage distribution systems
2010
The paper illustrates the interventions for improving security of a WiFi communication system applied in the automatic management of a Medium Voltage network. The management system fails if the data measured at the secondary substations can’t flow regularly. In this paper the security of the transmission as function of the action range of the radio channel, on the data sending time of the IEEE 802.11 protocol, and of the out of use of a WiFi node. Then, a modified IEEE 802.11 protocol is described, for making secure the transmission in presence of a high number of WiFI nodes. Finally, a probabilistic analysis in presented for analyzing the problem from an economical point of view.
An Improved IEEE 802.11 Protocol for Reliable Data Transmission in Power Distribution Fault Diagnosis
2010
A high level of power quality in distribution networks is obtained by means of a diagnostic software, that on-line assesses the status of the network, by elaborating the measured data. An efficient telecommunication system is thus necessary. Upon occurrence of a fault the reliability of the distribution system depends on the security of the timely protective and restorative actions on the network. In this paper, after a brief examination of the diagnostic method, the telecommunication system is examined. For this purpose, the WiFi telecommunication system has been considered the most suitable due to its economy, although it is not adequately reliable for how it is managed by the IEEE 802.11…
Cross-Technology WiFi/ZigBee Communications: Dealing With Channel Insertions and Deletions
2016
In this letter, we show how cross-technology interference can be exploited to set up a low-rate bidirectional communication channel between heterogeneous WiFi and ZigBee networks. Because of the environment noise and receivers' implementation, the cross-technology channel can be severely affected by insertions and deletions of symbols, whose effects need to be taken into account by the coding scheme and communication protocol.
Offloading through Opportunistic Networks with Dynamic Content Requests
2014
Offloading is gaining momentum as a technique to overcome the cellular capacity crunch due to the surge of mobile data traffic demand. Multiple offloading techniques are currently under investigation, from modifications inside the cellular network architecture, to integration of multiple wireless broadband infrastructures, to exploiting direct communications between mobile devices. In this paper we focus on the latter type of offloading, and specifically on offloading through opportunistic networks. As opposed to most of the literature looking at this type of offloading, in this paper we consider the case where requests for content are non-synchronised, i.e. users request content at random …
WMPS: A Positioning System for Localizing Legacy 802.11 Devices
2012
The huge success of location-aware applications calls for the quick development of a positioning system alternative to GPS for indoor localization based on existing technologies such as 802.11 wireless networks. In this paper we propose WMPS, the Wireless MAC Processor Positioning System, that is a localization system running on off-the-shelf 802.11 Access Points and based on time-of-flight ranging of users’ standard terminals. We prove through extensive experiments that propagation delays can be measured with the accuracy required by indoor applications despite the different noise components that can affect the result, like latencies of the hardware transreceivers, multi- path, ACK jitters…
Medium access in WiFi networks: strategies of selfish nodes
2009
This article provides a game theoretical analysis of the WiFi MAC protocol to understand the risks or the advantages offered by possible modifications of MAC functionalities implemented at the driver level.
A Cognitive Tuning of Contention Windows in WiFi Infrastructure Networks
2009
In WiFi networks, mobile nodes compete for accessing a shared channel by means of a random access protocol called Distributed Coordination Function (DCF). Although this protocol is in principle fair, since it should guarantee that all the stations have the same probability to transmit on the channel, it has been shown that unfair behaviors may emerge in actual networking scenarios. These phenomena are due to different reasons, including non-standard configurations of the nodes, critical network topologies, and short-term performance observations. In this paper we propose a game-theoretic approach for defining an enhanced DCF scheme suitable for WiFi intelligent nodes employing cognitive fun…
VANET prototipa realizācija ar WiFi protokolu palīdzību
2016
VANET tehnoloģija ļauj automobiļiem savā starpā komunicēt un informēt vienam otru par bīstamām situācijām uz ceļa. Veicot ES ceļu satiksmes negadījumu skaitu izpēti ir redzams, kā ir nepieciešama sistēma, kas spēj atbalstīt automobiļa vadītājus ceļā. Maģistra darba pētījuma mērķis ir izpētīt VANET tehnoloģiju, tās aktualitāti un iespējas, un izstrādājot prototipu izdarīt pētījumu, kurā pēc eksperimentu rezultātiem varēs izdarīt secinājumu, vai WiFi protokols spēj realizēt VANET tehnoloģiju nepieciešamā apjomā. Maģistra darbs sadalīts deviņās nodaļās. Darba pirmajā daļā tiek apskatīta un pētīta teorētiskā daļa, bet otrajā daļā tiek izveidots WiFi prototips un veikti eksperimenti. Maģistra da…