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dc.contributor.advisorHelberg, Prof. A.S.J.
dc.contributor.authorKrüger, Schalk Willem
dc.date.accessioned2017-08-30T08:22:39Z
dc.date.available2017-08-30T08:22:39Z
dc.date.issued2017
dc.identifier.urihttp://hdl.handle.net/10394/25449
dc.descriptionMEng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2017en_US
dc.description.abstractIn this dissertation, a design is presented for a Time Difference of Arrival (TDOA) positioning system that addresses a need in the market for an inexpensive and low-power wildlife positioning system. With this system, the position of a transmitter is determined cooperatively by a group of receiver stations from the differences in the time at which a short-lived transmission reaches the receivers. This enables the use of simple, inexpensive tag devices for which the energy consumption per position estimate is less than a hundredth of a GPS-enabled tag’s energy consumption. TDOA positioning requires precisely synchronised clocks at the receivers in order to relate the arrival time at different receivers to one another, which increases the cost and complexity of the receivers. A design with novel techniques that enable the use of simple, low-cost receivers with unsynchronised, inaccurate clocks is presented in this study. Arrival time estimates from different receivers are calibrated in software with the aid of periodic transmissions from one or more beacon transmitters. Furthermore, OOK modulation is used to enable fast frequency offset recovery. A prototype implementation of the design was developed with easily reproducible receiver stations constructed from low-cost, off-the-shelf, general-purpose hardware modules. An inexpensive software defined radio device, the RTL-SDR, was used and signal processing was performed in software. Techniques for improving the precision and for reducing the computational requirements of the signal processor were devised, analysed and compared. Software was developed for performing fast real-time signal processing on an inexpensive single-board computer, the Raspberry Pi 3. Moreover, software was developed for calculating position estimates from arrival time estimates and for analysing the data. The code has been released as open-source software to allow collaboration with research groups working in similar directions and to facilitate further experimentation. A pilot field test was conducted with two receivers spaced 9 km apart. The standard deviation of the TDOA estimates was found to be 11.5 ns, which is equivalent to a precision of 3.5 m for two-dimensional position estimates. In comparison with similar positioning systems, the system presented in this dissertation has a lower power consumption and is more than an order of magnitude cheaper, while similar positioning accuracy is being achieved. The techniques and software that were developed is not limited to wildlife tracking, but can be adapted for other applications such as livestock monitoring, asset tracking and passive radar. In hierdie verhandeling word ’n verskil-in-aankomstyd (VAT) posisioneringstelsel aangebied wat ’n behoefte in die mark vir ’n goedkoop en lae-energie wildopsporingstelstel aanspreek. Met hierdie stelsel word die posisie van ’n sender gemeenskaplik deur ’n groep ontvangerstasies bepaal deur gebruik te maak van die verskil in die tyd waarteen ’n kort uitsending vanaf die sender die ontvangers bereik. Dit maak die gebruik van eenvoudige en goedkoop opsporingstoestelle moontlik waarvan die energieverbruik per posisieskatting minder as ’n honderdste van dié van ’n GPS-geaktiveerde opsporingstoestel is. VAT-posisionering vereis noukeurige sinkronisasie tussen die ontvangers sodat aankomstye by verskillende ontvangers met mekaar vergelyk kan word, wat die koste en kompleksiteit van die ontvangers verhoog. ’n Ontwerp met nuwe tegnieke wat die gebruik van eenvoudige, laekoste ontvangers met ongesinkroniseerde, onakkurate klokfrekwensies moontlik maak, word in hierdie studie voorgelê. Aankomstydskattings van verskillende ontvangers word in sagteware gekalibreer met behulp van periodiese uitsendings vanaf ten minste een bakensender. Verder word die dragolf met aan-af-sleuteling gemoduleer sodat die draerfrekwensie maklik deur die ontvangers bepaal kan word. ’n Prototipe van die stelsel is ontwikkel met ontvangerstasies wat uit goedkoop, algemeen beskikbare, veeldoelige hardewaremodules saamgestel is. ’n Goedkoop sagteware-gedefinieerde radiotoestel, die RTL-SDR, is gebruik en seinverwerking is as sagteware toegepas. Tegnieke om die noukeurigheid van die seinverwerker te verbeter en om die verwerkingsvereistes te verminder is uitgedink, geanaliseer en vergelyk. Sagteware is ontwikkel om vinnige intydse seinverwerking op ’n goedkoop enkelbordrekenaar, die Raspberry Pi 3, uit te voer. Verder is daar ook sagteware ontwikkel om posisieskattings vanaf aankomstydskattings te bereken en om data te analiseer. Die kode is as oopbronsagteware beskikbaar gestel om samewerking met navorsingsgroepe wat in soortgelyke rigtings werk, toe te laat, en om verdere eksperimentering te vergemaklik. ’n Toetslopie is uitgevoer met twee ontvangers wat 9 km uitmekaar geplaas is. Die standaardafwyking van die VAT-skattings was 11.5 ns, wat ooreenstem met ’n noukeurigheid van 3.5 m vir twee-dimensionele posisieskattings. Die stelsel wat in hierdie verhandeling voorgelê word, is goedkoper en meer energie-doeltreffend as soortgelyke stelsels, terwyl die akkuraatheid van die posisieskattings vergelykbaar is. Die tegnieke en sagteware wat ontwikkel is, is nie beperk tot wildopsporing nie, maar kan vir ander toepassings soos veemonitering, bate-opsporing en passiewe radar aangepas worden_US
dc.language.isoenen_US
dc.publisherNorth-West University (South Africa) , Potchefstroom Campusen_US
dc.subjectTDOAen_US
dc.subjectRadio trackingen_US
dc.subjectLocalisationen_US
dc.subjectWildlife trackingen_US
dc.subjectSubsample interpolationen_US
dc.subjectSynchronisationen_US
dc.subjectRTL-SDRen_US
dc.titleAn inexpensive hyperbolic positioning system for tracking wildlife using off-the-shelf hardwareen_US
dc.typeThesisen_US
dc.description.thesistypeMastersen_US


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