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Development of a satellite communications software system and scheduling strategyGilmore, John Sebastian 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Stellenbosch University and the Katholieke Universiteit Leuven has a joint undertaking
to develop a satellite communications payload. The goals of the project are:
to undertake research and expand knowledge in the area of dynamically configurable
antenna beam forming, to prove the viability of this research for space purposes and
to demonstrate the feasibility of the development in a practical application.
The practical application is low Earth orbit satellite communication system for
applications in remote monitoring. Sensor data will be uploaded to the satellite,
stored and forwarded to a central processing ground station as the satellite passes
over these ground stations. The system will utilise many low-cost ground sensor
stations to collect data and distribute it to high-end ground stations for processing.
Applications of remote monitoring systems are maritime- and climate change
monitoring- and tracking. Climate change monitoring allows inter alia, for the monitoring
of the effects and causes of global warming.
The Katholieke Universiteit Leuven is developing a steerable antenna to be
mounted on the satellite. Stellenbosch University is developing the communications
payload to steer and use the antenna. The development of the communications
protocol stack is part of the project. The focus of this work is to implement the
application layer protocol, which handles all file level communications and also implements
the communications strategy.
The application layer protocol is called the Satellite Communications Software
System (SCSS). It handles all high level requests from ground stations, including
requests to store data, download data, download log files and upload configuration
information. The design is based on a client-server model, with a Station Server
and Station Handler. The Station Server schedules ground stations for communication
and creates a Station Handler for each ground station to handle all ground
station requests. During the design, all file formats were defined for efficient ground
station-satellite communications and system administration. All valid ground station
requests and handler responses were also defined.
It was also found that the system may be made more efficient by scheduling
ground stations for communications, rather than polling each ground station until
one responds. To be able to schedule ground station communications, the times
when ground stations will come into view of the satellite have to be predicted. This
is done by calculating the positions of the Satellite and ground stations as functions
of time. A simple orbit propagator was developed to predict the satellite distance
and to ease testing and integration with the communications system. The times
when a ground station will be within range of the satellite were then predicted and a
scheduling algorithm developed to minimise the number of ground stations not able to communicate.
All systems were implemented and tested. The SCSS executing on the Satellite
was developed and tested on the satellite on-board computer. Embedded implementations
possess strict resource limitations, which were taken into account during the
development process. The SCSS is a multi-threaded system that makes use of thread
cancellation to improve responsiveness. / AFRIKAANSE OPSOMMING: Die Universiteit van Stellenbosch ontwerp tans ’n satelliet kommunikasieloonvrag in
samewerking met die Katolieke Universiteit van Leuven. Die doel van die projek is
om navorsing te doen oor die lewensvatbaarheid van dinamies verstelbare antenna
bundelvorming vir ruimte toepassings, asook om die haalbaarheid van hierdie navorsing
in die praktyk te demonstreer.
Die praktiese toepassing is ’n satellietkommunikasiestelsel vir afstandsmonitering,
wat in ’n Lae-Aarde wentelbaan verkeer. Soos die satelliet in sy wentelbaan beweeg,
sal sensor data na die satelliet toe gestuur, gestoor en weer aangestuur word. Die
stelsel gebruik goedkoop sensorgrondstasies om data te versamel en aan te stuur na
kragtiger grondstasies vir verwerking.
Afstandsmoniteringstelsels kan gebruik word om klimaatsverandering, sowel as
die posisie van skepe en voertuie, te monitor. Deur oa. klimaatsveranderinge te
dokumenteer, kan gevolge en oorsake van globale verhitting gemonitor word.
Die Katholieke Universiteit van Leuven is verantwoordelik vir die ontwerp en
vervaardiging van die satelliet antenna, terwyl die Universiteit van Stellenbosch verantwoordelik
is vir die ontwerp en bou van die kommunikasie loonvrag. ’n Gedeelte
van hierdie ontwikkeling sluit die ontwerp en implementasie van al die protokolle van
die kommunikasieprotokolstapel in. Dit fokus op die toepassingsvlak protokol van die
protokolstapel, wat alle leêrvlak kommunikasie hanteer en die kommunikasiestrategie
implementeer.
Die toepassingsvlaksagteware word die Satellietkommunikasie sagtewarestelsel
(SKSS) genoem. Die SKSS is daarvoor verantwoordelik om alle navrae vanaf grondstasies
te hanteer. Hierdie navrae sluit die oplaai en stoor van data, die aflaai van
data, die aflaai van logs en die oplaai van konfigurasie inligting in. Die ontwerp
is op die standaard kliënt-bediener model gebasseer, met ’n stasiebediener en ’n
stasiehanteerder. Die stasiebediener skeduleer die tye wanneer grondstasies toegelaat
sal word om te kommunikeer en skep stasiehanteerders om alle navrae vanaf die
stasies te hanteer. Gedurende die ontwerp is alle leêrformate gedefinieer om doeltreffende
adminstrasie van die stelsel, asook kommunikasie tussen grondstasies en die
satelliet te ondersteun. Alle geldige boodskappe tussen die satelliet en grondstasies
is ook gedefnieer.
Daar is gevind dat die doeltreffendheid van die stelsel verhoog kan word deur die
grondstasies wat wil kommunikeer te skeduleer, eerder as om alle stasies te pols totdat
een reageer. Om so ’n skedule op te stel, moet die tye wanneer grondstasies binne
bereik van die satelliet gaan wees voorspel word. Hierdie voorspelling is gedoen deur
die posisies van die satelliet en die grondstasies as funksies van tyd te voorspel. ’n
Eenvoudige satelliet posisievoorspeller is ontwikkel om toetsing en integrasie met die SKSS te vergemaklik. ’n Skeduleringsalgoritme is toe ontwikkel om die hoeveelheid
grondstasies wat nie toegelaat word om te kommunikeer nie, te minimeer.
Alle stelsels is geimplementeer en getoets. Die SKSS, wat op die satelliet loop,
is ontwikkel en getoets op die satelliet se aanboord rekenaar. Die feit dat ingebedde
stelsels oor baie min hulpbronne beskik, is in aanmerking geneem gedurende die
ontwikkeling en implementasie van die SKSS. Angesien die SKSS ’n multidraadverwerkingsstelsel
is, word daar van draadkansellasie gebruik gemaak om die stelsel se
reaksietyd te verbeter.
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Automatic oral proficiency assessment of second language speakers of South African EnglishMuller, Pieter F.de V. 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The assessment of oral proficiency forms an important part of learning a second language.
However, the manual assessment of oral proficiency is a labour intensive task requiring specific
expertise. An automatic assessment system can reduce the cost and workload associated
with this task. Although such systems are available, they are typically aimed towards assessing
students of American or British English, making them poorly suited for speakers of South
African English. Additionally, most research in this field is focussed on the assessment of
foreign language students, while we investigate the assessment of second language students.
These students can be expected to have more advanced skills in the target language than
foreign language speakers.
This thesis presents a number of scoring algorithms for the automatic assessment of
oral proficiency. Experiments were conducted on a corpus of responses recorded during an
automated oral test. These responses were rated for proficiency by a panel of raters based
on five different rating scales. Automatic scoring algorithms were subsequently applied to
the same utterances and their correlations with the human ratings determined.
In contrast to the findings of other researchers, posterior likelihood scores were found to
be ineffective as an indicator of proficiency for the corpus used in this study. Four different
segmentation based algorithms were shown to be moderately correlated with human ratings,
while scores based on the accuracy of a repeated prompt were found to be well correlated
with human assessments.
Finally, multiple linear regression was used to combine different scoring algorithms to
predict human assessments. The correlations between human ratings and these score combinations
ranged between 0.52 and 0.90. / AFRIKAANSE OPSOMMING: Die assessering van spraakvaardigheid is ’n belangrike komponent van die aanleer van ’n
tweede taal. Die praktiese uitvoer van sodanige assessering is egter ’n arbeids-intensiewe
taak wat spesifieke kundigheid vereis. Die gebruik van ’n outomatiese stelsel kan die koste
en werkslading verbonde aan die assessering van ’n groot aantal studente drasties verminder.
Hoewel sulke stelsels beskikbaar is, is dit tipies gemik op die assessering van studente wat
Amerikaanse of Britse Engels wil aanleer, en is dus nie geskik vir sprekers van Suid Afrikaanse
Engels nie. Verder is die meerderheid navorsing op hierdie gebied gefokus op die assessering
van vreemde-taal sprekers, terwyl hierdie tesis die assessering van tweede-taal sprekers ondersoek.
Dit is te wagte dat hierdie sprekers se spraakvaardighede meer gevorderd sal wees
as di´e van vreemde-taal sprekers.
Hierdie tesis behandel ’n aantal evaluasie-algoritmes vir die outomatiese assessering van
spraakvaardighede. Die eksperimente is uitgevoer op ’n stel opnames van studente se antwoorde
op ’n outomatiese spraaktoets. ’n Paneel van menslike beoordelaars het hierdie opnames
geassesseer deur gebruik te maak van vyf verskillende punteskale. Dieselfde opnames is deur
die outomatiese evaluasie-algoritmes verwerk, en die korrelasies tussen die beoordelaars se
punte en die outomatiese evaluerings is bepaal.
In kontras met die bestaande navorsing, is daar gevind dat posterieure waarskynlikheidsalgoritmes
nie ’n goeie aanduiding van spraakvaardighede gee vir ons datastel nie. Vier
algoritmes wat van segmentasies gebruik maak, is ook ondersoek. Die evaluerings van hierdie
algoritmes het redelike korrelasie getoon met die punte wat deur die beoordelaars toegeken is.
Voorts is drie algoritmes ondersoek wat daarop gemik is om die akkuraatheid van herhaalde
sinne te bepaal. Die evaluerings van hierdie algoritmes het goed gekorreleer met die punte
wat deur die beoordelaars toegeken is.
Laastens is liniˆere regressie gebruik om verskillende outomatiese evaluerings te kombineer
en sodoende beoordelaars se punte te voorspel. Die korrelasies tussen hierdie kombinasies
en die punte wat deur beoordelaars toegeken is, het gewissel tussen 0.52 en 0.90.
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Language identification using Gaussian mixture modelsNkadimeng, Calvin 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The importance of Language Identification for African languages is seeing a
dramatic increase due to the development of telecommunication infrastructure
and, as a result, an increase in volumes of data and speech traffic in public
networks. By automatically processing the raw speech data the vital assistance
given to people in distress can be speeded up, by referring their calls to a person
knowledgeable in that language.
To this effect a speech corpus was developed and various algorithms were implemented
and tested on raw telephone speech data. These algorithms entailed
data preparation, signal processing, and statistical analysis aimed at discriminating
between languages. The statistical model of Gaussian Mixture Models
(GMMs) were chosen for this research due to their ability to represent an entire
language with a single stochastic model that does not require phonetic transcription.
Language Identification for African languages using GMMs is feasible, although
there are some few challenges like proper classification and accurate
study into the relationship of langauges that need to be overcome. Other methods
that make use of phonetically transcribed data need to be explored and
tested with the new corpus for the research to be more rigorous. / AFRIKAANSE OPSOMMING: Die belang van die Taal identifiseer vir Afrika-tale is sien ’n dramatiese toename
te danke aan die ontwikkeling van telekommunikasie-infrastruktuur en as gevolg
’n toename in volumes van data en spraak verkeer in die openbaar netwerke.Deur
outomaties verwerking van die ruwe toespraak gegee die noodsaaklike hulp verleen
aan mense in nood kan word vinniger-up ”, deur te verwys hul oproepe na
’n persoon ingelichte in daardie taal.
Tot hierdie effek van ’n toespraak corpus het ontwikkel en die verskillende algoritmes
is gemplementeer en getoets op die ruwe telefoon toespraak gegee.Hierdie
algoritmes behels die data voorbereiding, seinverwerking, en statistiese analise
wat gerig is op onderskei tussen tale.Die statistiese model van Gauss Mengsel
Modelle (GGM) was gekies is vir hierdie navorsing as gevolg van hul vermo
te verteenwoordig ’n hele taal met’ n enkele stogastiese model wat nodig nie
fonetiese tanscription nie.
Taal identifiseer vir die Afrikatale gebruik GGM haalbaar is, alhoewel daar
enkele paar uitdagings soos behoorlike klassifikasie en akkurate ondersoek na die
verhouding van TALE wat moet oorkom moet word.Ander metodes wat gebruik
maak van foneties getranskribeerde data nodig om ondersoek te word en getoets
word met die nuwe corpus vir die ondersoek te word strenger.
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Development of a Monte Carlo ad hoc routing protocol for connectivity improvementPerold, Philippus Rudolf 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / Please refer to full text for abstract.
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Data-driven augmentation of pronunciation dictionariesLoots, Linsen 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis investigates various data-driven techniques by which pronunciation dictionaries
can be automatically augmented. First, well-established grapheme-to-phoneme (G2P) conversion
techniques are evaluated for Standard South African English (SSAE), British English
(RP) and American English (GenAm) by means of four appropriate dictionaries: SAEDICT,
BEEP, CMUDICT and PRONLEX.
Next, the decision tree algorithm is extended to allow the conversion of pronunciations
between different accents by means of phoneme-to-phoneme (P2P) and grapheme-andphoneme-
to-phoneme (GP2P) conversion. P2P conversion uses the phonemes of the source
accent as input to the decision trees. GP2P conversion further incorporates the graphemes
into the decision tree input. Both P2P and GP2P conversion are evaluated using the four
dictionaries. It is found that, when the pronunciation is needed for a word not present
in the target accent, it is substantially more accurate to modify an existing pronunciation
from a different accent, than to derive it from the word’s spelling using G2P conversion.
When converting between accents, GP2P conversion provides a significant further increase
in performance above P2P.
Finally, experiments are performed to determine how large a training dictionary is required
in a target accent for G2P, P2P and GP2P conversion. It is found that GP2P
conversion requires less training data than P2P and substantially less than G2P conversion.
Furthermore, it is found that very little training data is needed for GP2P to perform at almost
maximum accuracy. The bulk of the accuracy is achieved within the initial 500 words,
and after 3000 words there is almost no further improvement.
Some specific approaches to compiling the best training set are also considered. By means
of an iterative greedy algorithm an optimal ranking of words to be included in the training
set is discovered. Using this set is shown to lead to substantially better GP2P performance
for the same training set size in comparison with alternative approaches such as the use of
phonetically rich words or random selections. A mere 25 words of training data from this
optimal set already achieve an accuracy within 1% of that of the full training dictionary. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek verskeie data-gedrewe tegnieke waarmee uitspraakwoordeboeke outomaties
aangevul kan word. Eerstens word gevestigde grafeem-na-foneem (G2P) omskakelingstegnieke
ge¨evalueer vir Standaard Suid-Afrikaanse Engels (SSAE), Britse Engels (RP)
en Amerikaanse Engels (GenAm) deur middel van vier geskikte woordeboeke: SAEDICT,
BEEP, CMUDICT en PRONLEX.
Voorts word die beslissingsboomalgoritme uitgebrei om die omskakeling van uitsprake
tussen verskillende aksente moontlik te maak, deur middel van foneem-na-foneem (P2P) en
grafeem-en-foneem-na-foneem (GP2P) omskakeling. P2P omskakeling gebruik die foneme
van die bronaksent as inset vir die beslissingsbome. GP2P omskakeling inkorporeer verder
die grafeme by die inset. Beide P2P en GP2P omskakeling word evalueer deur middel van
die vier woordeboeke. Daar word bevind dat wanneer die uitspraak benodig word vir ’n
woord wat nie in die teikenaksent teenwoordig is nie, dit bepaald meer akkuraat is om ’n
bestaande uitspraak van ’n ander aksent aan te pas, as om dit af te lei vanuit die woord se
spelling met G2P omskakeling. Wanneer daar tussen aksente omgeskakel word, gee GP2P
omskakeling ’n verdere beduidende verbetering in akkuraatheid bo P2P.
Laastens word eksperimente uitgevoer om die grootte te bepaal van die afrigtingswoordeboek
wat benodig word in ’n teikenaksent vir G2P, P2P en GP2P omskakeling. Daar
word bevind dat GP2P omskakeling minder afrigtingsdata as P2P en substansieel minder as
G2P benodig. Verder word dit bevind dat baie min afrigtingsdata benodig word vir GP2P
om teen bykans maksimum akkuraatheid te funksioneer. Die oorwig van die akkuraatheid
word binne die eerste 500 woorde bereik, en n´a 3000 woorde is daar amper geen verdere
verbetering nie.
’n Aantal spesifieke benaderings word ook oorweeg om die beste afrigtingstel saam te stel.
Deur middel van ’n iteratiewe, gulsige algoritme word ’n optimale rangskikking van woorde
bepaal vir insluiting by die afrigtingstel. Daar word getoon dat deur hierdie stel te gebruik,
substansieel beter GP2P gedrag verkry word vir dieselfde grootte afrigtingstel in vergelyking
met alternatiewe benaderings soos die gebruik van foneties-ryke woorde of lukrake seleksies.
’n Skamele 25 woorde uit hierdie optimale stel gee reeds ’n akkuraatheid binne 1% van di´e
van die volle afrigtingswoordeboek.
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GaN microwave power FET nonlinear modelling techniquesBrooks, Clive Raymond 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The main focus of this thesis is to document the formulation, extraction and validation of
nonlinear models for the on-wafer gallium nitride (GaN) high-electron mobility (HEMT) devices
manufactured at the Interuniversity Microelectronics Centre (IMEC) in Leuven, Belgium. GaN
semiconductor technology is fast emerging and it is expected that these devices will play an
important role in RF and microwave power amplifier applications. One of the main advantages
of the new GaN semiconductor technology is that it combines a very wide band-gap with high
electron mobility, which amounts to higher levels of gain at very high frequencies. HEMT
devices based on GaN, is a fairly new technology and not many nonlinear models have been
proposed in literature. This thesis details the design of hardware and software used in the
development of the nonlinear models. An intermodulation distortion (IMD) measurement setup
was developed to measure the second and higher-order derivative of the nonlinear drain current.
The derivatives are extracted directly from measurements and are required to improve the
nonlinear model IMD predictions. Nonlinear model extraction software was developed to
automate the modelling process, which was fundamental in the nonlinear model investigation.
The models are implemented in Agilent’s Advanced Design System (ADS) and it is shown that
the models are capable of accurately predicting the measured S-parameters, large-signal singletone
and two-tone behaviour of the GaN devices. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie tesis is om die formulering, ontrekking en validasie van nie-lineêre
modelle vir onverpakte gallium nitraat (GaN) hoë-elektronmobilisering transistors (HEMTs) te
dokumenteer. Die transistors is vervaaardig by die Interuniversity Microelectronics Centre
(IMEC) in Leuven, België. GaN-halfgeleier tegnologie is besig om vinnig veld te wen en daar
word voorspel dat hierdie transistors ʼn belangrike rol gaan speel in RF en mikrogolf kragversterker
toepassings. Een van die hoof voordele van die nuwe GaN-halfgeleier tegnologie is
dat dit 'n baie wyd band-gaping het met hoë-elektronmobilisering, wat lei tot hoë aanwins by
mikrogolf frekwensies. GaN HEMTs is 'n redelik nuwe tegnologie en nie baie nie-lineêre
modelle is al voorgestel in literatuur nie. Hierdie tesis ondersoek die ontwerp van die hardeware
en sagteware soos gebruik in die ontwikkeling van nie-lineêre modelle. 'n Intermodulasie
distorsie-opstelling (IMD-opstelling) is ontwikkel vir die meting van die tweede en hoër orde
afgeleides van die nie-lineêre stroom. Die afgeleides is direk uit die metings onttrek en moet die
nie-lineêre IMD-voorspellings te verbeter. Nie-lineêre onttrekking sagteware is ontwikkel om die
modellerings proses te outomatiseer. Die modelle word geïmplementeer in Agilent se Advanced
Design System (ADS) en bewys dat die modelle in staat is om akkurate afgemete S-parameters,
grootsein enkeltoon en tweetoon gedrag van die GaN-transistors te kan voorspel.
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Stall prevention control of fixed-wing unmanned aerial vehiclesBasson, Matthys Michaelse 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis presents the development of a stall prevention flight control subsystem,
which can easily be integrated into existing flight control architectures of fixed-wing
unmanned aerial vehicles (UAV’s). This research forms an important part of faulttolerant
flight control systems and will ensure that the aircraft continues to operate
safely within its linear aerodynamic region.
The focus of this thesis was the stall detection and prevention problem. After a thorough
literature study on the topic of stall, a model based stall prevention control algorithm
with feedback from an angle of attack sensor was developed. This algorithm
takes into account the slew rate and saturation limits of the aircraft’s servos and is
able to predict when the current flight condition will result in stall. The primary concern
was stall during wings-level flight and involved the prevention of stall by utilising
only the elevator control surface. A model predictive slew rate control algorithm was
developed to override and dynamically limit the elevator command to ensure that the
angle of attack does not exceed a predefined limit. The stall prevention control system
was designed to operate as a switching control scheme, to minimise any restrictions
imposed on the existing flight control system.
Finally, software in the loop simulations were conducted using a nonlinear aircraft
model and realistic sensor noise, to verify the theoretical results obtained during
the development of this stall prevention control strategy. A worst-case performance
analysis was also conducted to investigate the robustness of the control algorithms
against model uncertainties. / AFRIKAANSE OPSOMMING: Hierdie tesis handel oor die ontwikkeling van ’n staak voorkomings-vlugbeheer substelsel
wat maklik geïntegreer kan word in bestaande vlugbeheer argitektuur van
onbemande vaste-vlerk lugvaartuie. Hierdie tesis vorm ’n belangrike deel van fouttolerante
vlugbeheertegnieke en sal verseker dat die vliegtuig slegs binne sy lineêre
aerodinamiese werksgebied bly.
Die fokus van hierdie tesis is die staak opsporing en voorkomings probleem. Na afloop
van ’n deeglike literatuurstudie oor die onderwerp van staak, is ’n model gebaseerde
staak voorkomings-beheertegniek ontwikkel, wat terugvoer van ’n invalshoek sensor
ontvang. Hierdie algoritme neem die sleur tempo en defleksie limiete van die vliegtuig
se servos in ag en is in staat om staak te voorspel. Die primêre oorweging was
staak tydens simmetriese vlugte en behels slegs die voorkoming van staak deur gebruik
te maak van die hei beheer oppervlak. ’n Model voorspellings sleur tempo
beheeralgoritme is ontwikkel om die hei-roer dinamies te beperk sodat die invalshoek
nie ’n sekere vooraf bepaalde limiet oorskry nie. Die staak voorkomings beheerstelsel
is ontwerp om te funksioneer as ’n skakel beheer skema om die beperkings op die
bestaande vlugbeheerstelsel te minimaliseer.
Laastens was sagteware-in-die-lus simulasies gebruik om die teoretiese resultate, wat
verkry is tydens die ontwikkeling van hierdie staak voorkomings beheer-strategie, te
kontroleer. Om die robuusthied van hierdie beheeralgoritmes teen model onsekerhede
te ondersoek, is ’n ergste-geval prestasie analise ook uitgevoer.
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Volumetric data throughput optimisation by dynamic FEC bearing frame length adaptationChristelis, Christian 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The telecommunications link between a LEO satellite and a rural ground station
with a non-tracking antenna, has a strongly varying link quality and
a short communications window. The satellite acts as a store-and-forward
node between ground stations. The TC-SDLP and an FTP protocol form a
shallow protocol stack, which excludes unneeded protocol functionality and
the resulting overhead. Coding gain, introduced by BCH FEC in the TCSDLP,
allows for link quality improvement.
The core of this thesis is an improvement of the TC-SDLP to maximise effective
payload data throughput, or goodput. This improvement was achieved
by creating an optimal segment length selection metric based on the BER.
Since the BER is not determinable from within the TC-SDLP, the metric was
twice determined; once based on the FER and finally based on time delays.
The work includes an extensive background study, which consists of space
standardisation, orbital physics, error detection and correction, space datalink
protocols, data throughput and culminating in the protocol stack design.
The project specific link budget calculation is presented. The optimal
segment length policy was mathematically determined.
Asimulation model of the TC-SDLP was used as a proof of concept for the
effective throughput and give a performance benchmark. Finally a TC-SDLP
implementation offers a real world performance demonstration. / AFRIKAANSE OPSOMMING: Die telekommunikasie skakel tussen ’n lae aardomwenteling (LEO) sateliet
en ’n plattelandse grondstasie met ’n nie-volg antenna, het ’n skakelkwaliteit
wat in ’n groot mate varieer en ’n kort kommunikasievenster. Die sateliet tree
op as ’n stoor- en- aanstuur node tussen grondstasies. Die TC-SDLP en ’n leêr
oordrag protokol (FTP) vorm ’n vlak protokol stapel, wat onnodige protokol
funksionaliteit en die gevolglike opkoste uitsluit. Kode aanwins, wat deur
die BCH FEC in die TC-SDLP, aangebring word, verbeter die skakelkwaliteit.
Die kern van hierdie tesis is ’n verbetering van die TC-SDLP om sodoende
die ware deurvoer van nuttige vragdata te maksimimeer. Hierdie verbetering
is bereik deur die skep van ’n optimale segmentlengte-seleksie metode
gebaseer of die bit fout tempo (BER).
Aangesien die BER nie bepaal kan word vanuit die TC-SDLP nie, is die
maatstaf twee keer bepaal; die eerste keer is die bepaling gebaseer op die
raamwerk fout tempo (FER) en die finale bepaling op tyd vertragings.
Die tesis sluit ’n omvattende agtergrondstudie in, wat bestaan uit ruimte
standardisering, wentelbaan fisika, die opspoor en regstel van foute, ruimte
inligtingskakel protokol en deurstuur van data wat uitloop op die protokol
ontwerp. Daar word aangedui hoe die berekening van die begroting vir die
skakel van toepassing op die spesifieke projek, gedoen is. ’n Wiskundige
analise van die optimale segmentlengte s ook gedoen.
’n Simulasie model van die TC-SDLP is gebruik as ’n bewys van die konsep
vir die ware deurset en gee ’n prestasie maatstaf. Laastens bied die TCSDLP
implementering ’n ware wereld prestasie demonstrasie.
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The development and implementation of a localised position location strategySchonken, Willem Petrus Francois 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Location and tracking of personnel and assets is a lucrative enterprise that has seen much expansion in
the last decade or two. This expansion is coupled with the rise in popularity of GPS-based technologies.
It has become common practice for businesses to track and manage vehicle fleets with GPS enabled
devices. We use GPS to navigate while driving our cars, to keep track of our loved ones and we even
have GPS receivers in our cell phones.
Unfortunately, GPS technology has a few limitations. It can only be used in areas with a clear view of the
sky, as line-of-sight must be maintained with at least four satellites at all times. This precludes the use of
GPS indoors or in heavily built-up areas. GPS receivers are also still quite expensive.
This thesis developed and implemented a strategy for Localised Position Location. Several possible
solutions were investigated. Spread Spectrum was selected as the best method to develop into a
working example. The characteristics of Spread Spectrum signals and Pseudo-Noise Codes were
investigated in some detail, which led to the proposal of several simulation models. These simulations
suggested that a simple configuration consisting of a transmitter, sliding correlator, bandpass filter and
RF power detector can effectively track a stationary target.
A transmitter was designed and implemented and was then used in a simplified measurement to
corroborate the predictions made by earlier simulations. With results looking positive it was decided to
continue with the design and implementation of a receiver. A complete transmitter/receiver system
allowed for extensive measurements to be made. The physical measurements agreed with simulated
predictions, confirming that the proposed position location strategy is effective. / AFRIKAANSE OPSOMMING: Die toenemende gewildheid en toeganklikheid van GPS-gebaseerde opsporingstegnologie het gelei tot
‘n geweldige toename in die verkope van toerusting om die beweging van besigheidsbates te monitor en
bestuur. Selfs op die persoonlike ontspanningsmark vind GPS-tegnologie toenemend aanklank met
vervaardigers van selfone en voertuignavigasietoerusting.
GPS-gebaseerde opsporingstegnologie het egter beperkinge, omdat dit te alle tye direkte oogkontak
moet behou met minstens vier satelliete. Gevolglik kan GPS-gebaseerde opsporingstegnologie nie
binnenshuis of in erg beboude gebiede gebruik word nie. GPS ontvangers is ook redelik duur.
Hierdie thesis het `n strategie vir Gelokaliseerde Posisie Bepaling ontwikkel en geïmplementeer.
Ondersoek is ingestel na `n verskeidenheid van moontlike oplossings. Strek Spektrum is gekies as die
beste metode om verder in `n werkende voorbeeld te ontwikkel. Die eienskappe van Strek Spektrum
seine en Pseudo-Ruis Kodes is in detail bestudeer, wat gelei het na die opstelling van `n aantal simulasie
modelle. Hierdie modelle dui aan dat `n eenvoudige opstelling, bestaande uit `n sender, glykorellator,
banddeurlaat filter en `n RF drywingsmeter doeltreffend aangewend kan word om `n stilstaande teiken
te monitor.
`n Sender, wat in `n vereenvoudigde meetopstelling gebruik kon word om van die voorspellings wat
vroeër gemaak is te staaf, is hierna ontwerp en gebou. Met positiewe resultate is daar besluit om voort
te gaan met die ontwerp en bou van `n ontvanger. Met `n volledige sender/onvanger stelsel was dit
moontlik om uitgebreide meetings te neem. Die fisiese meetings stem ooreen met die simulasies se
voorspellings, wat dien as bevestiging dat die voorgestelde strategie vir posisie bepaling doeltreffend
aangewend kan word.
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A CAD tool for the prediction of VLSI interconnect reliability.Frost, David Frank. January 1988 (has links)
This thesis proposes a new approach to the design of reliable VLSI interconnects,
based on predictive failure models embedded in a software tool
for reliability analysis.
A method for predicting the failure rate of complex integrated circuit interconnects
subject to electromigration, is presented. This method is based
on the principle of fracturing an interconnect pattern into a number of statistically
independent conductor segments. Five commonly-occurring segment
types are identified: straight runs, steps resulting from a discontinuity
in the wafer surface, contact windows, vias and bonding pads. The relationship
between median time-to-failure (Mtf) of each segment and physical
dimensions, temperature and current density are determined. This model
includes the effect of time-varying current density. The standard deviation
of lifetime is also determined as a function of dimensions. A· minimum
order statistical method is used to compute the failure rate of the interconnect
system. This method, which is applicable to current densities below
106 AI cm2 , combines mask layout and simulation data from the design data
base with process data to calculate failure rates.
A suite of software tools called Reliant (RELIability Analyzer for iNTerconnects)
which implements the algorithms described above, is presented.
Reliant fractures a conductor pattern into segments and extracts electrical
equivalent circuits for each segment. The equivalent circuits are used
in conjunction with a modified version of the SPICE circuit simulator to
determine the currents in all segments and to compute reliability. An interface
to a data base query system provides the capability to access reliability
data interactively. The performance of Reliant is evaluated, based on two
CMOS standard cell layouts. Test structures for the calibration of the
reliability models are provided.
Reliant is suitable for the analysis of leaf cells containing a few hundred
transistors. For MOS VLSI circuits, an alternative approach based on the
use of an event-driven switch-level simulator is presented. / Thesis (Ph.D.)-University of Natal, Durban, 1988.
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