Development of path loss model for 802.11n in large conference rooms

In this paper, a path loss (PL) model for 802.11n in large conference rooms is determined, based on PL measurements. The PL can be described accurately by a one-slope model with one standard deviation. PL exponents varying from 1.2 to 1.7 are found. Based on this PL model, the effect of frequency (2.4 vs 5 GHz), configuration (SISO vs MIMO (spatial diversity)), bandwidth (20 vs 40 MHz) and transmit power on number of access points, total power consumption and possible (physical) throughputs is investigated. According to the determined PL model, a higher range (by tuning the transmit power) requires less access points, as well as a lower total power consumption, due to a PL exponent lower than 2

Performance loss due to multipath propagation for IEEE 802.11 systems

In this work, we developed an analytical estimation of the performance loss due to multipath propagation for a narrowband OFDM system. The propagation characteristics required for this loss estimation, are experimentally determined by virtual SIMO measurements in a large conference room where repeated reception problems were reported for an IEEE 802.11 system, as well as in 2 other large conference rooms for comparison. The resulting losses due to multipath are calculated for IEEE 802.11a/n and related to the propagation characteristics

Measurement of atmospheric neutrino oscillations with IceCube

We present the first statistically significant detection of neutrino oscillations in the high-energy regime (>20 GeV) from an analysis of IceCube Neutrino Observatory data collected in 2010 and 2011. This measurement is made possible by the low-energy threshold of the DeepCore detector (~20 GeV) and benefits from the use of the IceCube detector as a veto against cosmic-ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20-100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV-10 TeV) was extracted from IceCube data to constrain systematic uncertainties. The disappearance of low-energy upward-going muon neutrinos was observed, and the nonoscillation hypothesis is rejected with more than 5σ significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters |Δm(32)(2)|=(2.3(-0.5)(+0.6))×10(-3) eV(2) and sin(2)(2θ(23))>0.93, and maximum mixing is favored.M. G. Aartsen ... G. C. Hill ... et al. (IceCube Collaboration

Measurement of the cosmic ray energy spectrum with IceTop-73

We report on the measurement of the all-particle cosmic ray energy spectrum with the IceTop air shower array in the energy range from 1.58 PeV to 1.26 EeV. The IceTop air shower array is the surface component of the IceCube Neutrino Observatory at the geographical South Pole. The analysis was performed using only information from IceTop. The data used in this work were taken from June 1, 2010 to May 13, 2011. During that period the IceTop array consisted of 73 stations, compared to 81 in its final configuration. The measured spectrum exhibits a clear deviation from a single power law above the knee around 4 PeV and below 1 EeV. We observe spectral hardening around 18 PeV and steepening around 130 PeV.M. G. Aartsen ... G. C. Hill ... et al. (IceCube Collaboration

Supernova neutrino detection with IceCube

The IceCube Neutrino Observatory, situated at the geographic South Pole, was completed in December 2010. A lattice of 5160 photomultiplier tubes monitors one cubic kilometer of deep Antarctic ice in order to detect neutrinos via Cherenkov photons emitted by charged by-products of their interaction in matter. We report on IceCube's response to MeV neutrinos generated by core-collapse supernova explosions of nearby massive stars. This unique telescope was designed to detect energies greater than 100GeV. Due to subfreezing ice temperatures, the photomultipliers' dark noise rates are particularly low. Therefore IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photo- multiplier rates on top of the dark noise. In the case of a supernova at the galactic center, IceCube's sensitivity matches that of a background free megaton-scale supernova search experiment and decreases to 20 and 6 standard deviations for star explosions at the galactic edge (30 kpc) and the Large Magellanic Cloud (50 kpc), respectively. © Società Italiana di Fisica.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Improvements for IceCube's Supernova Search System

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HitSpooling: an improvement for the supernova neutrino detection system in icecube

The IceCube Neutrino Observatory consists of a lattice of 5160 photomultiplier tubes (PMTs)which monitor one cubic kilometer of deep Antarctic ice at the geographic South Pole.IceCube was primarily designed to detect neutrinos of energies greater than O(100 GeV).Due to subfreezing ice temperatures, the photomultipliers' dark noise rates are particularlylow which enables IceCube to search for neutrinos from galactic supernovae by detectingbursts of MeV neutrinos emitted during the core collapse and for several seconds following.For that purpose, a dedicated online supernova DAQ system records the total number of hitsin the detector, without any further information from the PMTs, and generates supernovacandidate triggers in case of a significant detector rate enhancement. A new feature to thestandard DAQ, called HitSpooling, was implemented in IceCube during this thesis. TheHitSpooling system is implemented in the standard DAQ system and buffers the completeraw data stream of the photomultipliers for several hours or days. By reading out time periodsof HitSpool data around supernova candidate triggers, generated by the online supernovaDAQ system, we overcome the limitations of the latter and have access to the entire informationof the detector in case of a supernova. Furthermore, HitSpool data is a powerfulsource for studying and understanding the noise behavior of the detector as well as backgroundprocesses coming from atmospheric muons. The idea of HitSpooling was developed in thescope of this thesis and is the basis of the work at hand. The developed interface between thestandard DAQ and the supernova DAQ system is presented. The correlated dark noise componentin optical modules of IceCube is quantified for the first time and possible explanationsare discussed. The possibility of identifying triggering and subthreshold atmospheric muonsin HitSpool data and subtracting them from a possible supernova signal is analyzed. Furthermore,the conversion from HitSpool data to supernova DAQ type data was developedwhich allows for a comparison of both data types with respect to lightcurves and significancesof selected supernova candidate triggers.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe