11 research outputs found
A survey of measurement-based spectrum occupancy modeling for cognitive radios
Spectrum occupancy models are very useful in cognitive radio designs. They can be used to increase spectrum sensing accuracy for more reliable operation, to remove spectrum sensing for higher resource usage efficiency, or to select channels for better opportunistic access, among other applications. In this survey, various spectrum occupancy models from measurement campaigns taken around the world are investigated. These models extract different statistical properties of the spectrum occupancy from the measured data. In addition to these models, spectrum occupancy prediction is also discussed, where autoregressive and/or moving-average models are used to predict the channel status at future time instants. After comparing these different methods and models, several challenges are also summarized based on this survey
Verification and validation of UML and SysML based systems engineering design models
In this thesis, we address the issue of model-based verification and validation of systems engineering design models expressed using UML/SysML. The main objectives are to assess the design from its structural and behavioral perspectives and to enable a qualitative as well as a quantitative appraisal of its conformance with respect to its requirements and a set of desired properties. To this end, we elaborate a heretofore unattempted unified approach composed of three well-established techniques that are model-checking, static analysis, and software engineering metrics. These techniques are synergistically combined so that they yield a comprehensive and enhanced assessment. Furthermore, we propose to extend this approach with performance analysis and probabilistic assessment of SysML activity diagrams. Thus, we devise an algorithm that systematically maps these diagrams into their corresponding probabilistic models encoded using the specification language of the probabilistic symbolic model-checker PRISM. Moreover, we define a first of its kind probabilistic calculus, namely activity calculus, dedicated to capture the essence of SysML activity diagrams and its underlying operational semantics in terms of Markov decision processes. Furthermore, we propose a formal syntax and operational semantics for the input language of PRISM. Finally, we mathematically prove the soundness of our translation algorithm with respect to the devised operational semantics using a simulation preorder defined upon Markov decision processes
Facilitating Flexible Link Layer Protocols for Future Wireless Communication Systems
This dissertation addresses the problem of designing link layer protocols
which are flexible enough to accommodate the demands offuture wireless
communication systems (FWCS).We show that entire link layer protocols with
diverse requirements and responsibilities can be composed out of
reconfigurable and reusable components.We demonstrate this by designing and
implementinga novel concept termed Flexible Link Layer (FLL)
architecture.Through extensive simulations and practical experiments, we
evaluate a prototype of the suggested architecture in both
fixed-spectrumand dynamic spectrum access (DSA) networks.
FWCS are expected to overcome diverse challenges including the continual
growthin traffic volume and number of connected devices.Furthermore, they
are envisioned to support a widerange of new application requirements and
operating conditions.Technology trends, including smart homes,
communicating machines, and vehicularnetworks, will not only grow on a
scale that once was unimaginable, they will also become the predominant
communication paradigm, eventually surpassing today's human-produced
network traffic.
In order for this to become reality, today's systems have to evolve in many
ways.They have to exploit allocated resources in a more efficient and
energy-conscious manner.In addition to that, new methods for spectrum
access and resource sharingneed to be deployed.Having the diversification
of applications and network conditions in mind, flexibility at all layers
of a communication system is of paramount importance in order to meet the
desired goals.
However, traditional communication systems are often designed with specific
and distinct applications in mind. Therefore, system designers can tailor
communication systems according to fixedrequirements and operating
conditions, often resulting in highly optimized but inflexible
systems.Among the core problems of such design is the mix of data transfer
and management aspects.Such a combination of concerns clearly hinders the
reuse and extension of existing protocols.
To overcome this problem, the key idea explored in this dissertation is a
component-based design to facilitate the development of more flexible and
versatile link layer protocols.Specifically, the FLL architecture,
suggested in this dissertation, employs a generic, reconfigurable data
transfer protocol around which one or more complementary protocols, called
link layer applications, are responsible for management-related aspects of
the layer.
To demonstrate the feasibility of the proposed approach, we have designed
andimplemented a prototype of the FLL architecture on the basis ofa
reconfigurable software defined radio (SDR) testbed.Employing the SDR
prototype as well as computer simulations, thisdissertation describes
various experiments used to examine a range of link layerprotocols for both
fixed-spectrum and DSA networks.
This dissertation firstly outlines the challenges faced by FWCSand
describes DSA as a possible technology component for their construction.It
then specifies the requirements for future DSA systemsthat provide the
basis for our further considerations.We then review the background on link
layer protocols, surveyrelated work on the construction of flexible
protocol frameworks,and compare a range of actual link layer protocols and
algorithms.Based on the results of this analysis, we design, implement, and
evaluatethe FLL architecture and a selection of actual link layer
protocols.
We believe the findings of this dissertation add substantively to the
existing literature on link layer protocol design and are valuable for
theoreticians and experimentalists alike
Investigation on Nitric Oxide and Soot of Biodiesel and Conventional Diesel using a Medium Duty Diesel Engine
Biodiesel has been suggested as an alternative fuel to the petroleum diesel fuel. It beneficially reduces regulated emission gases, but increases NOx (nitric oxide and nitrogen dioxide) Thus, the increase in NOx is the barrier for potential growth of the biodiesel fuel. In general, NOx formation is dominated by flame temperature. Interestingly, soot can play a role as a heat sink as well as a heat transfer media to high temperature gases. Thus, the cooling effect of soot may change the flame temperature and therefore, NOx emissions.
In this study, emphasis is placed on the relationship between soot and NO (Nitric oxide) formation. For the experimental study, a metallic fuel additive is used since barium is known to be effective to suppress soot formation during combustion. The barium additive is applied to #2D (Number 2 diesel fuel) by volume basis: 0.1, 0.25 and 0.5 %-v, and to the palm olein oil by 0.25 %-v. All the tests are carried out in a four-cylinder medium duty diesel engine, 4045 DI diesel engine, manufactured by John Deere. For the analysis, an analytical model is used to estimate combustion temperature, NO concentration and soot emissivity.
The results show that NO concentration does not have the expected trade-off relation with soot. Rather, NO concentration is found to be more strongly affected by ambient temperature and combustion characteristics than by soot. The results of the analytical model show the reasonable NO estimation and the improvement on temperature calculation. However, the model is not able to explain the detailed changes of soot emissivity by the different fuels since the emissivity correlation is developed empirically for diesel fuel
ICTERI 2020: ІКТ в освіті, дослідженнях та промислових застосуваннях. Інтеграція, гармонізація та передача знань 2020: Матеріали 16-ї Міжнародної конференції. Том II: Семінари. Харків, Україна, 06-10 жовтня 2020 р.
This volume represents the proceedings of the Workshops co-located with the 16th International Conference on ICT in Education, Research, and Industrial Applications, held in Kharkiv, Ukraine, in October 2020. It comprises 101 contributed papers that were carefully peer-reviewed and selected from 233 submissions for the five workshops: RMSEBT, TheRMIT, ITER, 3L-Person, CoSinE, MROL. The volume is structured in six parts, each presenting the contributions for a particular workshop. The topical scope of the volume is aligned with the thematic tracks of ICTERI 2020: (I) Advances in ICT Research; (II) Information Systems: Technology and Applications; (III) Academia/Industry ICT Cooperation; and (IV) ICT in Education.Цей збірник представляє матеріали семінарів, які були проведені в рамках 16-ї Міжнародної конференції з ІКТ в освіті, наукових дослідженнях та промислових застосуваннях, що відбулася в Харкові, Україна, у жовтні 2020 року. Він містить 101 доповідь, які були ретельно рецензовані та відібрані з 233 заявок на участь у п'яти воркшопах: RMSEBT, TheRMIT, ITER, 3L-Person, CoSinE, MROL. Збірник складається з шести частин, кожна з яких представляє матеріали для певного семінару. Тематична спрямованість збірника узгоджена з тематичними напрямками ICTERI 2020: (I) Досягнення в галузі досліджень ІКТ; (II) Інформаційні системи: Технології і застосування; (ІІІ) Співпраця в галузі ІКТ між академічними і промисловими колами; і (IV) ІКТ в освіті