265 research outputs found
Comparing Gausian and exact models of malicious interference in VLC systems
Visible Light Communication (VLC) is a technique for high-speed, low-cost wireless data transmission based on LED luminaries. Wireless LAN environments are a major application of VLC. In these environments, VLC is used in place of traditional systems such as Wi-Fi. Because of the physical characteristics of visible light, VLC is considered to be superior to traditional radio-based communication in terms of security. However, as in all wireless systems, the security of VLC with respect to eavesdropping, signal jamming and modification must be analyzed. This paper focuses on the aspect of jamming in VLC networks. In environments where multiple VLC transmitters are used, there is the possibility that one or more transmitters will be hostile (or "rogue"). This leads to communication disruption, and in some cases, the hijacking of the legitimate data stream. In this paper we present the theoretical system model that is used in simulations to evaluate various rogue transmission scenarios in a typical indoor environment. The typical approach used so far in jamming analysis assumes that all disruptive transmissions may be modeled as Gaussian noise, but this assumption may be too simplistic. We analyze and compare two models of VLC jamming: the simplified Gaussian and the exact model, where the full characteristics of the interfering signal are taken into account. Our aim is to determine which methodology is adequate for studying signal jamming in VLC systems
Lattice QCD Thermodynamics on the Grid
We describe how we have used simultaneously nodes of the
EGEE Grid, accumulating ca. 300 CPU-years in 2-3 months, to determine an
important property of Quantum Chromodynamics. We explain how Grid resources
were exploited efficiently and with ease, using user-level overlay based on
Ganga and DIANE tools above standard Grid software stack. Application-specific
scheduling and resource selection based on simple but powerful heuristics
allowed to improve efficiency of the processing to obtain desired scientific
results by a specified deadline. This is also a demonstration of combined use
of supercomputers, to calculate the initial state of the QCD system, and Grids,
to perform the subsequent massively distributed simulations. The QCD simulation
was performed on a lattice. Keeping the strange quark mass at
its physical value, we reduced the masses of the up and down quarks until,
under an increase of temperature, the system underwent a second-order phase
transition to a quark-gluon plasma. Then we measured the response of this
system to an increase in the quark density. We find that the transition is
smoothened rather than sharpened. If confirmed on a finer lattice, this finding
makes it unlikely for ongoing experimental searches to find a QCD critical
point at small chemical potential
The A4 project: physics data processing using the Google protocol buffer library
In this paper, we present the High Energy Physics data format, processing
toolset and analysis library a4, providing fast I/O of structured data using
the Google protocol buffer library. The overall goal of a4 is to provide
physicists with tools to work efficiently with billions of events, providing
not only high speeds, but also automatic metadata handling, a set of UNIX-like
tools to operate on a4 files, and powerful and fast histogramming capabilities.
At present, a4 is an experimental project, but it has already been used by the
authors in preparing physics publications. We give an overview of the
individual modules of a4, provide examples of use, and supply a set of basic
benchmarks. We compare a4 read performance with the common practice of storing
unstructured data in ROOT trees. For the common case of storing a variable
number of floating-point numbers per event, speedups in read speed of up to a
factor of six are observed.Comment: Proceedings of poster shown at the 2012 International Conference on
Computing in High Energy and Nuclear Physics (CHEP 2012). 19 pages, 17
figure
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