83 research outputs found
Precision timing in TDMA - based Wireless Sensor Network through IEEE 1588 standard
This paper proposes an energy-efficient time synchronization scheme for Wireless Sensor Networks(WSNs) based on the IEEE 1588 standard. Although a number of methods have been studied for time synchronization of WSNs, some applications require high precision time synchronization with very low power consumption. This paper presents a reduced implementation of IEEE 1588 precision time protocol (PTP) for WSNs. Within the proposed synchronization approach, a sensor node is synchronized using the timing message generated by a master node synchronized with GPS. This paper also presents experiments to evaluate the performance of the precision time synchronization of a slave-master pair of sensor nodes.Peer ReviewedPostprint (published version
Experimental analysis of WiMAX and meshed Wi-Fi quality of service
Mestrado em Engenharia Electrónica e TelecomunicaçõesA indústria das telecomunicações tem sofrido uma evolução enorme nosúltimos anos. Tanto em termos de comunicações sem fios, como em termos deligações de banda larga, assistiu-se a uma adesão massiva por parte domercado, o que se traduziu num crescimento enorme, já que a tecnologia temque estar um passo à frente da procura, de forma a suprir as carências dosconsumidores. Assim, a evolução persegue um objectivo claro: possibilidadede possuir conectividade de banda larga em qualquer lugar e instante. Nestecontexto, aparecem as tecnologias WiMAX (Worldwide Interoperability forMicrowave Access) e WI-FI em Malha como possibilidades para atingir estefim.
O tema desta dissertação incide no estudo das tecnologias de WiMAX e WI-FIem Malha, mais concretamente no estudo da Qualidade de Serviço (QoS)providenciada pelas normas IEEE 802.16 e IEEE 802.11s para serviços deVoIP e VoD.
Esta tese apresenta a arquitectura desenvolvida para a correcta integração deQoS para serviços em tempo real no acesso à banda larga sem fios depróxima geração. De seguida, apresenta testes efectuados com osequipamentos disponÃveis de WiMAX e WI-FI em Malha, de forma a mostrar ocorrecto comportamento da atribuição extremo-a-extremo de QoS nos cenáriosescolhidos com serviços em tempo real, bem como os efeitos da mobilidade natecnologia WI-FI em Malha.
ABSTRACT: The telecommunication industry has suffered a massive evolution throughoutpast years. In terms of wireless communications, as well as broadbandconnections, we’ve seen a massive adoption by the market, which conductedinto an enormous growth, since the technology must always be one step aheadof the demand, in order to be to fulfill the needs of the consumers. Therefore,the evolution pursues one clear goal: the possibility to establish a broadbandconnection anywhere and anytime. In this context, the WiMAX (WorldwideInteroperability for Microwave Access) and Meshed WI-FI technologies appearas possibilities to reach this goal.
The subject of this thesis is the study of both the WiMAX and Meshed WI-FItechnologies, and more concretely the study of the QoS provided by theIEEE802.16 and IEEE 802.11s standards to VoIP and VoD services.
This thesis presents the architecture developed to provide the correctintegration of QoS for real-media traffic in next generation broadband wirelessaccess. It presents tests carried out with the available WiMAX and Meshed WI-FI equipments, to show the correct behavior in the attribution of end-to-endQoS in selected scenarios with real-time services, as well as mobility effects onWI-FI Wireless Mesh technology
Time synchronization of a commercial seismometer through IEEE-1588
Seismometers use a GPS signal for time synchronization and the seismic data are collected, time marked and stored. The precision of the time marks is a key parameter for the location and magnitude of an earthquake.Land seismometers are implemented with an internal GPS receiver where only an external antenna is needed for time synchronization. This paper presents the implementation of the time synchronization of a land seismometer through the IEEE-1588 protocol.Time synchronization tests have been carried out and results are presented.Peer ReviewedPostprint (published version
COBS time synchronization for data adcquisition
This work presents a solution to seismometer synchronization with GPS
time stamping, in zones without signal, such as the seafloor. Due to the
needing of acquire with precision the time when seismological events occur,
in order to know magnitude and location of an earthquake.Peer Reviewe
Software Defined Radio Localization using 802.11-style Communications
This major qualifying project implements a simple indoor localization system using software defined radio. Both time of arrival and received signal strength methods are used by an array of wireless receivers to trilaterate a cooperative transmitter. The implemented system builds upon an IEEE 802.11b-like communications platform implemented in GNU Radio. Our results indicate substantial room for improvement, particularly in the acquisition of time data. This project contributes a starting point for ongoing research in indoor localization, both through our literature review and system implementation
CLOCK SYNCHRONIZATION AND TARGET LOCATION DETERMINATION IN WIRELESS NETWORKS
In a distributed system most nodes maintain a local oscillator to derive time information for synchronization with other nodes. A number of clock synchronization techniques have been presented in the literature (e.g. NTP, PTP) which rely on the exchange of messages among nodes to share timing information and to adjust
the oset or skew of the clocks. We present an approach which does not require any adjustments to the local clocks, but relies on achieving synchronization through clock mapping functions which map the time at one node to the time at another node. We further show how closed paths in a graph of nodes can be used to estimate the synchronization tolerance. Through experimental results using piecewise linear functions, we demonstrate the feasibility of this approach and show how clock synchronization of better than 100 ps can be achieved in Wi-Fi environments.
Using the techniques and relying on the hardware of SMiLE3 board, we also demonstrate the ability to measure distance with accuracy of a few inches and thereby the localization to accuracy better than one foot. Results of experiments conducted for localization are also presented
Seeing the Unseen: The REVEAL protocol to expose the wireless Man-in-the-Middle
A Man-in-the-Middle (MiM) can collect over-the-air packets whether from a
mobile or a base station, process them, possibly modify them, and forward them
to the intended receiver. This paper exhibits the REVEAL protocol that can
detect a MiM, whether it has half duplex capability, full duplex capability, or
double full duplex capability. Protocol is based on synchronizing clocks
between the mobile and the base station, with the MiM being detected if it
interferes in the synchronization process. Once synchronized, the REVEAL
protocol creates a sequence of challenge packets where the transmission times
of the packets, their durations, and their frequencies, are chosen to create
conflicts at the MiM, and make it impossible for the MiM to function. We
implement the REVEAL protocol for detecting a MiM in 4G technology. We
instantiate a MiM between the 4G/5G base station and a mobile, and exhibit the
successful detection mechanisms. With the shared source code, our work can be
reproduced using open software defined cellular networks with off-the-shelf
device
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