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Modeling of multipath fading channels for network simulationRajkumar Samuel, 15 May 2009 (has links)
Development of accurate physical layer models is very important for generating
realistic network simulation results. Significant effort has been put into setting up
physical layer models for wireless channels that emulate the impact of the channel on
the higher layers of the network. Setting up the models is especially difficult for a
frequency selective channel. In this thesis the use of non-linear functions to convert
the frequency selective channel to an equivalent flat fading channel is examined. The
analytical expressions for the statistics of the equivalent flat fading process that are
needed to set up the physical layer models are derived. These results are used to set
up the physical layer model for the frequency selective channel. Extensive simulations
are performed to verify the accuracy of the model against a detailed physical layer
implementation. The statistics of the model and the actual channel are seen to match,
validating the method of setting up the models.
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A New Simulation of Multi-State Fading ChannelsMendu, Arjun 18 August 2003 (has links)
No description available.
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PARAMETER CHARACTERIZATION ON A TELEMETRY CHANNEL INCLUDING THE EFFECTS OF THE SPECULAR RAYDye, Ricky G., Horne, Lyman D. 11 1900 (has links)
International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The aeronautical channel model is a good candidate for modeling the effects of
multipath interference of telemetry signals on test ranges. The aeronautical fading
channel model is parameterized by the signal to noise ratio, the Doppler shift and time
delay between the specular and direct components, the specular to direct power ratio,
the direct to diffuse power ratio, and the bandwidth of the multipath fading process.
Segments of weighting signal data measured during a test at Tyndall AFB provide
data which can be used to determine typical values of the above parameters in a
variety of telemetering environments. In this paper, the set of parameters which most
closely model the actual telemetry channel using the Tyndall data is determined.
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Implementation of Fading Channel SimulatorWu, Yang-Ying 28 August 2003 (has links)
A Rayleigh/Rician fading channel based on Jakes¡¦ model is implemented by FPGA hardware in this thesis. Parameters, including vehicular speed, carrier frequency, quantization bits and internal clock rate, are carefully chosen according to the fading statistics. Verification of this fading channel hardware is carried out on Altera FPGA board with functional and time sequential test. Finally, performance of a differential PSK modem via fading and noisy channel is simulated and emulated in both software and hardware methods.
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The Efficacy of Different Stimulus Fading Procedures to Teach Verbal Operants to an Older Adult with AphasiaRitchie, Hannah 01 August 2015 (has links)
Aphasia can severely impact an individual’s ability to communicate. However, existing research on interventions is limited. The current study compared different stimulus fading procedures with an older adult diagnosed with aphasia. A multielement within a multiple baseline design across behaviors was used to measure the efficacy of each approach. Results showed that the time delay procedure was more efficient at fading prompts when teaching intraverbals.
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Optimal weighted partial decision combining for fading channel diversityKot, Alan Douglas January 1987 (has links)
A diversity combining scheme is examined that utilizes a demodulator's hard decisions in conjunction with knowledge of each decision's reliability. A maximum-likelihood bit decision is made, based on these partial decisions from the demodulator
and on measurements of the state of the fading channel. The technique is sub-optimal since hard decisions are processed, but it may find application in low cost receiver design. The technique is optimal in the sense that a minimum probability of bit error is achieved, given a set of partial decisions and knowledge of their reliability.
Performance analysis for the case of non-coherent frequency shift keying on a slow Rayleigh fading channel with additive white Gaussian noise includes the derivation of a tight upper bound on the probability of bit error, and estimates of the asymptotic performance relative to standard diversity schemes such as majority-voting, selection diversity, square-law, and maximal ratio combining. These results are supported by simulation results for bit and packet error rates in an example system. With five independent bit repeats and a BER of 10⁻³, the receiver is about 3 dB more efficient than majority-voting, and about 1 dB more efficient than selection diversity. The gain in efficiency, relative to the standard partial decision combination schemes, increases with the number of repeats.
The degradation in performance in a practical receiver implementation is addressed,
and it is demonstrated that near ideal performance may be obtained with only a few reliability weights quantized to a small number of levels. Furthermore, this performance is maintained over a wide range of average signal to noise ratio without having to adapt the reliability weights. When the reliability estimate is corrupted by additive white Gaussian noise, it is demonstrated that simple low- pass filtering of the signal strength estimate is sufficient to obtain near ideal performance.
The performance is degraded in the presence of cochannel interference, but for a moderate level of interference the performance is demonstrated to be superior to majority-voting or selection diversity.
Other results include a method to estimate the optimal quantization thresholds, and a method to obtain the probability of error of selection diversity receivers employing signal to noise ratio measurement quantization. The selection diversity analysis is applicable to the more general case of Rician fading. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
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ADAPTIVE MODULATION FOR COGNITIVE RADIOSharma, Gaurav 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / While investigating methods for more efficiently allocating the available spectrum researchers noticed that in many geographical locations, there are broad bands of frequencies that are lightly utilized. Such inefficiencies are inevitable with fixed spectral allocation rules. Cognitive Radios actively measure the spectral utilization and adapt their modulation, frequencies, bandwidths, power, etc. to take advantage of these lightly used “spectral holes” or “white spaces”. Much of the research work in cognitive radios has not taken into account some of the challenges faced in the telemetry community-including multipaths and a guaranteed quality of service. This paper highlights how some mathematical models of adaptive modulation discussed extensively in many research papers and textbooks can be used in Cognitive Radios as well.
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Performance analysis of multi-carrier code division multiple access system in multipath fading channelsSaid, Nezar Ali January 1998 (has links)
No description available.
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Iterative Equalization for SOQPSK in Multipath FadingLei, Qiang, Rice, Michael 10 1900 (has links)
ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / This paper investigates the application of iterative equalization techniques to overcome multipath fading for shaped offset QPSK (SOQPSK) in aeronautical telemetry. Two iterative equalization techniques for turbo encoded SOQPSK are presented. The first is the optimal-MAP turbo equalizer for OQPSK. The second equalizer is the adaptive decision feedback equalizer. Simulation shows that in the presence of frequency selective multipath typically encountered in aeronautical telemetry, both of these equalizers exhibit impressive performance.
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Red colour development and loss in pear fruitSteyn, Willem J. (Willem Jacobus) 03 1900 (has links)
Thesis (PhD (Agric))--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Downgrading of fruit due to insufficient red colour has limited the profitability of
lucrative blushed pear cultivars (Pyrus communis L.). In 'Rosemarie', poor fruit colour
has been ascribed to pre-harvest red colour loss during periods of high temperature.
The regulation of colour development in pears has not been studied and, in addition,
little is known about anthocyanin degradation in attached fruit.
Changes in colour were recorded and phenylalanine ammonia-lyase (PAL) and
UDPGalactose: flavonoid-3-0-glycosyltransferase (UFGT) activities assessed in
response to cold fronts and during fruit development in order to establish the
regulation of colour development in red and blushed pear cultivars. Best red colour
was generally attained a month or more before harvest whereafter red colour faded
towards harvest. Unlike in some other fruits, UFGT activity apparently did not limit
colour development whereas fading of red colour towards harvest might relate to
decreasing PAL activity. 'Rosemarie' colour fluctuated considerably, increasing with
cold fronts and decreasing during intermittent warmer periods, while red colour was
more stable in other cultivars. PAL and UFGT activities in 'Rosemarie' increased in
response to low temperatures, but were unaffected in 'Bon Rouge'. We concluded
that anthocyanin synthesis in 'Rosemarie' requires low temperatures while colour
development in 'Bon Rouge' and probably also other cultivars is primarily regulated
by endogenous factors.
Detached pome fruit were used to study temperature and light effects on anthocyanin
degradation and fruit colour and to assess the modifying effect of anthocyanin
concentration on colour loss. Anthocyanin degradation and red colour loss increased
linearly between 10°C and 30°C. Irradiation further increased the rate of degradation
and colour loss. The rate of colour loss depended on anthocyanin concentration,
being much faster in fruit with high compared to fruit with low pigment levels. This
was ascribed to the exponential relationship between anthocyanin concentration and
hue at high pigment levels and the linear relationship at lower pigment levels.
Anthocyanin degradation and pre-harvest red colour loss in 'Rosemarie' was
quantitatively confirmed and corresponded with a warm period during fruit
development. Based on these data, we attributed the susceptibility of 'Rosemarie' to pre-harvest colour loss to low anthocyanin concentrations in its peel that allow the
visualisation of net anthocyanin degradation at high temperatures.
Overhead evaporative cooling (EG) as measure to improve red colour in blushed
pears was evaluated. 'Rosemarie' fruit that received pulsed EG applications from two
weeks before harvest at air temperatures exceeding 28°G were redder than control
fruit at harvest. EG had no effect on 'Forelle' colour. Though EG could be used to
improve 'Rosemarie' fruit colour in warm production areas, its effect was relatively
small compared to colour change in response to temperature.
Lastly, we assessed the photoprotective function of anthocyanin in pear peel.
Photoinhibition was evident in exposed faces of pears under natural conditions. The
extent of photoinhibition increased with decreasing redness of peel and was
maintained after photoinhibitory treatment. Although anthocyanin was apparently able
to afford photoprotection at 40oG, we argued against this as a general function. There
were indications that photoprotection was associated, but not necessarily due to light
attenuation by anthocyanin. / AFRIKAANSE OPSOMMING: Afgradering van vrugte vanweë onvoldoende rooi kleur beperk die winsgewendheid
van blospeercultivars (Pyrus communis L.). In die geval van 'Rosemarie' word swak
kleur toegeskryf aan vooroes rooikleurverlies gedurende warm periodes. Die
regulering van kleurontwikkelling in pere is nog nie ondersoek nie terwyl min bekend
is oor antosianiendegradasie aan die boom.
Om die regulering van kleurontwikkelling in rooi- en blospeercultivars vas te stel, is
veranderinge in kleur en in die aktiwiteit van fenielalanien ammonia-liase (FAL) en
UDPGalaktose: flavonoied-3-o-glikosieltransferase (UFGT) gemeet gedurende
vrugontwikkelling en in reaksie op koue fronte. Pere was op hul rooiste 'n maand of
langer voor oes. Hierna het rooi kleur afgeneem tot met oes. Anders as in sommige
ander vrugsoorte het UFGT aktiwiteit nie kleurontwikkeling beperk nie. Die afname in
rooi kleur tot met oes mag egter verband hou met 'n gelyktydige afname in FAL
aktiwiteit. 'Rosemarie' kleur het aansienlik gefluktueer in reaksie op temperatuur.
Rooi kleur het toegeneem met koue fronte en afgeneem in die warmer periodes
tussen fronte. Rooi kleur was meer stabiel en klaarblyklik minder afhanlik van lae
temperature in ander peercultivars. Die noodsaaklikheid van lae temperature vir
kleurontwikkelling in 'Rosemarie' is bevestig deur 'n toename in ensiemaktiwiteit in
reaksie op koue fronte. Lae temperature het geen effek gehad op ensiemaktiwiteit in
'Bon Rouge' nie.
Appels en pere is gebruik om die effek van temperatuur en lig op
antosianiendegradasie en vrugkleur te ondersoek. Die modifiserende effek van
antosianienkonsentrasie op kleurverlies is ook ondersoek. Antosianiendegradasie en
rooi kleurverlies het lineêr toegeneem tussen 10° en 30°C. Beligting het degradasie
en kleurverlies verder versnel. Die tempo van kleurverlies was afhanklik van
antosianienkonsentrasie. Kleurverlies was aansienlik vinniger in vrugte met hoë
pigmentvlakke, in vergelyking met vrugte met lae pigmentvlakke vanweë die
eksponensiële verwantskap tussen antosianienkonsentrasie en
kleurskakeringswaardes (hue values) by hoë pigmentvlakke en die lineêre
verwantskap by lae pigmentvlakke. Antosianiendegradasie en vooroes
rooikleurverlies in 'Rosemarie' is kwantitatief bevestig en het saamgeval met 'n warm periode tydens vrugontwikkelling. Gebaseer op hierdie data is die gevoeligheid van
'Rosemarie' vir vooroes rooikleurverlies toegeskryf aan lae antosianienkonsentrasies
wat die sigbaarheid van netto antosianiendegradasie by hoë temperature verhoog.
Die gebruik van oorhoofse evaporatiewe verkoeling (EG) om rooi kleur van blospere
te verbeter is ge-evalueer. 'Rosemarie' vrugte wat evaporatief verkoel is bo 28°G
vanaf twee weke voor oes, was rooier as kontrole vrugte by oes. 'Forelle' kleur het
nie gereageer op EG nie. Die effek van EG op vrugkleur was relatief klein in
vergelyking met die effek van temperatuur. AI kan EG 'Rosemarie' kleur verbeter in
warm produksiestreke sou dit meer effektief wees om 'Rosemarie' se verbouing te
beperk tot koeler klimaatstreke.
Laastens is die vermoë van antosianien om peerskil teen fotoinhibisie te beskerm
ondersoek. Fotoinhibisie was aanwesig in vrugskil wat direk blootgestel was aan
sonlig in die boord. Die omvang van fotoinhibisie het toegeneem met 'n afname in
rooi pigmentasie van vrugskil. Die verband tussen skilkleur en fotoinhibisie was
steeds aanwesig na blootstelling aan ligstres by 10° en 400G. Ons het egter
geredeneer teen 'n algemene funksie vir antosianien in fotobeskerming by hoë
temperature. Verder was daar aanduidings dat, alhoewel geassossieer met rooi
skilkleur, beskerming teen ligstres nie noodwendig te wyte was aan antosianien nie.
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