Dissertations / Theses on the topic 'Network RTK'

Sammanfattning   Förutsättning   I examensarbetet har det ingått ett verkligt ärende som handläggs av mig som MBK-ingenjör inom Lantmäteriet. Det är ett naturvårdsuppdrag från Länsstyrelsen och innefattar bl a inmätning och utstakning av gräns på ett blivande naturreservat.   Naturvårdsuppdraget Huskeberget ligger ca 5 km norr om Södra Finnskoga och sydväst om Höljes i norra Värmland. Omkrets 2,38 km. Områdets höjd är ca 550 m över havet och ligger på sydöstra sluttningen av Huskeberget.   Fix   Lantmäteriet använder idag Leica Viva CS15/GS15 mätutrustning vid inmätning av brytpunkter och gränser. I detta fall det blivande naturreservatet. Under vissa omständigheter kan det ta tid att få fix-lösning eller helt utebli. Dessa omständigheter kan bero på ett flertal faktorer bl a kraftiga jonosfärsstörningar och/eller GPRS-nätets täckningsområde för mottagning av SWEPOS nätverks-RTK tjänst.   Inriktning   Fokus har lagts på att utvärdera ett alternativ till nätverks-RTK, en sk enkelstations-RTK med uppkoppling till en tillfällig referensstation.   Närmare undersökning har gjorts på tiden för initialisering vid varje enskild inmätning som sedan jämförts i de två mätmetoderna. Tiden för själva arbetet sätts sedan i relation till resultatet från undersökningen för att ge en helhetsbild av tidsåtgång i arbetet med vardera mätmetoden.   Resultat   Efter alla brytpunkter mätts in visade det sig att i just det här området inte fanns några anmärkningsvärda problem att få fix-lösning med någon av de valda mätmetoderna. Resultatet visar därmed små skillnader i tidsjämförelser.   En oplanerad testmätning med nätverks-RTK gjordes i tät skog alldeles intill en inmätt brytpunkt utan framgång att få fix-lösning. Detta för att belysa problematiken med att få fix-lösning vid mätning i tät skog.   Rapporten innehåller en kortfattad beskrivning av delar av arbetet i Lantmäteriets handläggning av naturvårdsuppdrag.

The purpose of this report is to provide a detailed assessment and investigation into the performance of the Real-Time Kinematic (RTK) network Nordic Construction Company (NCC) established, as part of its aim to better leverage technology within its business, to ensure the high quality and efficiency its clients have come to expect of NCC. Within the course of this investigation, extended RTK and raw data survey sessions were undertaken at each of four baselines significant to NCC (5, 15, 25, and 35 kilometers) from three of NCC’s five RTK base stations. Subsequent analysis resulted in hard documentation of the network performances and of the fidelity of the implementation itself. The research also resulted in deliverables consisting of statistics, computations, as well as utilities that will aid in decision making and allow users to better integrate and utilize the RTK network confidently within projects. It was found that NCC’s RTK performed essentially as expected in each circumstance and well within theory and empirical experience in terms of expected accuracies and best practices. This was concluded by comparison to accessible works by the U.S. Army Corps of Engineers and the NAVSTAR (GPS) development team. Of which are aggregated within document EM-110-1-1003 (NAVSTAR Global Positioning System Surveying) published by the U.S. Army Corps of Engineers. It is important to outline that this manual’s extensive use as a primary work throughout this report is due to authors’ trust in the publishing sources as well as the documents robust combination and illustration of theoretical and empirical content. The manual states that performance in the range of 1-3 centimeters in the horizontal and 3-10 centimeters in the vertical should be expected under the circumstances tested herein and to a majority were achieved. Some unique observations and patterns were identified as a result of discussion with NCC and analysis of the data. Patterns in the data pointed to a number of things in regards to the time and elevation mask influence. During the morning sessions the fifteen and thirty  five kilometer baselines exhibited better performance, while conversely the five and twenty five kilometer baselines performed best in the afternoon. In regards to elevation mask, little influence was found at the five kilometer baseline length, whoever the 10° displayed the best performance at the remaining baseline lengths.

This thesis is an accuracy research of detail surveying with networkRTK. Another objective of the thesis concerns some proposed controlmethods and to estimate if they are practically useful, and if the theoreticalassumptions of accuracy levels can be adjusted to standardisedtolerances for such control methods.The control methods are “revisit with network RTK” and “separatecontrol with conventional technique”, both in plane and height. Therevisit can be processed alone, or integrated with the productionmeasurements. Conventional technique involves a totalstation or alevelling instrument. The authors consider the control methods to bepractically useful.The modification of the theoretical assumptions of accuracy levelshas been based on an extensive material of measurements, calculations,analyses and considerations. This thesis achieved a standarderror in plane of 10 mm and in height of 15 mm (without the standarderror of the geoid model), which is comparable with similarstudies carried out lately. However, the conditions in this study areconsidered to be very favourable. To achieve the accuracy in plane, atripod of some type is necessary to minimize the influence from thecentering standard errors.Our modified accuracy levels can in the future be adjusted to standardisedtolerances, but more studies at different locations andunder other conditions are then necessary.
Detta examensarbete avser en noggrannhetsundersökning av detaljmätning med nätverks-RTK. Underlagsmaterialet har bestått i förslag till kontrollmetoder och teoretiska antaganden om de noggrannhetsnivåer som kan förväntas. Underlaget har utarbetats av Clas-Göran Persson vid Lantmäteriet (Persson 2008a). Det har också ingått i uppgiften att bedöma om metoderna är användbara även för rutinmässiga kontroller vid ”vardagsmätning” samt om noggrannhetsnivåerna skulle kunna omformas till felgränser, a la HMK (Handbok till Mätningskungörelsen), för sådana metoder. Kontrollmetoderna i fält består dels av ”återbesök med nätverks- RTK”, dels av ”separat kontroll med konventionell teknik”. De avser såväl plan- som höjdläget. Återbesök kan göras som särskild åtgärd eller integrerat med pågående produktionsmätningar. Konventionell teknik innebär kontroll med antingen totalstation eller avvägningsinstrument. Författarna anser att kontrollmetoderna är praktiskt tilllämpbara; återbesök kan enkelt genomföras under pågående detaljmätningar och den separata kontrollen med konventionell teknik (totalstation) är passande i en beställarroll. Modifieringen av de antagna noggrannhetsnivåerna har baserats på ett ganska omfattande material av mätningar, beräkningar, analyser, och överväganden. I detta arbete uppnåddes ett medelfel i plan på 10 mm och ett medelfel i höjd på 15 mm (exklusive felet i geoidmodellen SWEN05_RH2000), vilket överensstämmer med liknande studier som gjorts på senare tid (Edwards et al. 2008). Dock kan de förhållanden som rådde i Gävle hösten 2008 anses ha varit mycket gynnsamma. För att uppnå plannoggrannheten krävs emellertid någon form av tvångscentrering för att minimera centreringsfelen. Höjdnoggrannheten kan komma att bli betydligt sämre under perioder av omfattande solfläcksaktivitet som återkommer regelbundet, med ett större maximum kring slutet av år 2011 (SWPC 2009). Detta medför att förväntad noggrannhet i höjd i detta arbete har lagts på en sämre nivå än vad som egentligen uppnåddes. Höjdnoggrannheten kan nog förbättras genom den nya geoidmodellen SWEN08 som lanserades i januari 2009 (Ågren 2009). Fler faktorer som kan påverka noggrannheten för nätverks-RTK är osäkerhet i definitionen av antennens elektriska centrum, avstånd till referensstationerna, lokalisering inom eller utanför SWEPOS-nätverket, etc. De modifierade noggrannhetsnivåerna kan på sikt omformas till felgränser, men då krävs fler projekt på olika platser, utspritt i tiden och under andra förhållanden.

Network RTK is a real-time technique for accurate positioning with Global Navigation Satellite Systems (GNSS). The technology means the use of correction data from a network of GNSS receivers with known positions (reference stations) to reduce the uncertainty in position for the user´s GNSS receiver (rover). However, this requires that the correction data can be transferred seamlessly to the user in real time. Commonly the corrections are transferred via mobile phones. The Swedish National Land Survey operates a nationwide Network RTK service, where users can receive correction data via GSM or mobile Internet (GPRS). Network RTK service is based on a nationwide network of permanent reference stations for GNSS, SWEPOS which is also used for other applications. The aim of the study is to examine how the delay and loss in the transmission of network corrections affect measurement with Network RTK service from SWEPOS. Three receivers of different types, Trimble, Topcon and Leica were used to receive signals (all three at the same time) via a fixed external GNSS antenna with very good receiving conditions. Special software was used to create delays and loss of correction data from correction data to the three receivers.   The results show that the threshold where delay and loss means that receivers can no longer calculate a precise position varies between brands. Leica was the most sensitive to loss of correction data, Trimble for delays, while Topcon held up well for both. A new initialization requires that data loss and delay are not too large. Position deviations due to loss and delay of correction data indicate a significant difference between radial plane deviations and height deviations, especially at high loss of correction data. Delays of 0–4 s and various losses of correction data have generally small impact on the standard uncertainty values ​​in latitude and longitude. The standard uncertainty in height is 1.5–2 times higher than it is in plane. The impact of the baseline length is not significant, a marginal increase in the standard uncertainty was seen when increasing from 10 km to 30 km.
Nätverks-RTK är en realtidsteknik för noggrann positionering med hjälp av Global Navigation Satellite Systems (GNSS). Tekniken innebär att användaren utnyttjar korrektionsdata från ett nätverk av GNSS-mottagare med kända positioner (referensstationer) för att minska osäkerheten i positionen för den egna GNSS-mottagaren (rover). Detta ställer dock krav på att korrektionsdata kan överföras problemfritt till användaren i realtid. Vanligen sker den överföringen via mobiltelefoni. Lantmäteriet driver en rikstäckande nätverks-RTK-tjänst, där användarna kan erhålla korrektionsdata via GSM eller mobilt Internet (GPRS). Nätverks-RTK-tjänsten baseras på ett rikstäckande nät av fasta referensstationer för GNSS, SWEPOS, vilket också används för andra tillämpningar.   Syftet med studien är att undersöka hur fördröjning och bortfall i överföringen av nätverkskorrektioner påverkar mätning med SWEPOS nätverks-RTK-tjänst. För det ändamålet användes tre mottagare av fabrikaten Leica, Trimble och Topcon som parallellt tog emot signaler via en fast extern GNSS-antenn under mycket goda mottagningsförhållanden. En särskild programvara användes för att skapa fördröjningar och bortfall av korrektionsdata till de tre mottagarna.   Resultaten visade att tröskelvärdet, där fördröjning och bortfall gör att mottagarna inte längre kan beräkna en noggrann position, varierade mellan fabrikaten. Leica var mest känslig för bortfall, Trimble för fördröjningar, medan Topcon stod sig bra för båda. Vid ny initialisering av fixlösning krävdes att databortfall och fördröjning inte var för stora för någon av fabrikaten. Positionsavvikelserna beroende på bortfall och fördröjning av korrektionsmeddelanden visar på en signifikant skillnad mellan radiella planavvikelser och höjdavvikelser, speciellt vid höga bortfall. Fördröjningar på 0–4 s och olika bortfall har generellt liten påverkan på standardosäkerheternas värden i latitud- och longitudled. I höjdled är genomgående standardosäkerheten 1,5–2 gånger större än vad den är i planled. Baslinjelängdens betydelse är inte så stor, en marginell ökning av standardosäkerheten kunde ses vid ökning från 10 km till 30 km.

GNSS-teknik ersätter i allt högre grad terrester mätteknik, dels på grund av sin enkelhet och dels på grund av att den är mindre kostsam än traditionella metoder. En vanlig förekommande GNSS-teknik är RTK (Real Time Kinematic) som är en teknik som beräknar en position i realtid genom bärvågsmätning. Inom RTK-mätning finns det olika tekniker att utöva; enkelstations-RTK (ERTK) och nätverks-RTK (NRTK). I studien undersöktes kvaliteten och lägesosäkerhet på höjdbestämningsdata erhållen från dessa metoder. En envägs variansanalys (ANOVA) användes för att undersöka om det fanns en signifikant skillnad mellan de genomsnittliga avvikelser som erhölls från mätmetoderna. Mätmetoderna utfördes över två punkter med känd höjd som fastställdes tidigare med ett dubbelavvägningståg. ERTK och NRTK varvades med en observationstid på 20 minuter med positioneringsintervall på 3 sekunder. Tidseparationen mellan mätningarna varade i 30 minuter och sammanlagt utfördes 5 mätserier med 400 observationer i varje serie. Grova fel eliminerades genom att kassera värden som föll utanför 3σ-gränsen. Resultaten från ERTK-mätningarna visade att punkten kunde höjdbestämmas med en lägesosäkerhet på 22 mm och en mätosäkerhet på 32 mm (2σ) för samtliga mätserier tillsammans. Internt varierade lägesosäkerheten 13–28 mm mellan serierna. NRTK mätningarna erhöll en total lägesosäkerhet på 14 mm och en mätosäkerhet på 24 mm (2σ). Från enskilda mätserier erhöll serie 3 den lägsta lägesosäkerheten på 9 mm, och serie 4 den högsta med 18 mm. Generellt visade NRTK-metoden lägre och jämnare avvikelser från referensdata än ERTK, resultatet kan dock ha blivit påverkat av basens läge i relation till ett närliggande träd. ANOVA-testet visade att det fanns en signifikant skillnad mellan mätserierna (p =0,00) per enskild metod, men skillnaden av medelavvikelserna mellan dessa metoder var inte signifikanta (p =0,115). Resultatet från denna studie är viktig med avseende på kvalitetsutvärdering av olika GNSS-metoder och kan användas som underlag för beslut om tillämpad metod för andra mätuppdrag.
A quality survey was performed on the position accuracy of two GNSS-methods (single station-RTK and network-RTK) for height determination, and a one-way analysis of variance (ANOVA) was used for statistical investigation of differences in the spread of height deviations. The GNSS-methods were applied on a reference point, which was determined prior with leveling, and measured with 20 minutes observation time and 30 minutes time separation, resulting in 5 series containing 400 observations each from respective method. The ANOVA test was performed by grouping the height deviations with respect to the measurement series, as well as the mean deviations with respect to the methods. Height determination with the ERTK method showed a total positional uncertainty of 22 mm (13-28 mm between the series) and a measurement uncertainty of 32 mm (2σ). Results obtained with NRTK showed a total positional uncertainty of 14 mm (9-14 between the series) and a total measurement uncertainty of 24 mm (2σ). The statistical tests showed that the differences between the measurement series for individual methods were significant (p = 0,000) but that the mean deviations between the methods were not (p = 0,115). NRTK obtained a lower positional uncertainty than ERTK measurements in this study, and the ANOVA test showed that there was no significant difference in the distribution of the mean deviations between the measurement methods. This study is important with regard to quality evaluation of different GNSS-methods and can be used as a basis for deciding on the applied measurement method.

Network-RTK is a method of relative measuring using GNSS that provides users in alarge area with an easy way obtaining low uncertainties in their measurements. Regularnetwork-RTK does not meet the requirements of the Swedish Transport Administration(STA) regarding its larger and/or more complex projects, leading to the concept ofproject-based network-RTK being introduced in Sweden by the STA, in collaborationwith the network-RTK service provider SWEPOS back in 2004. This concept improvesupon regular network-RTK by decreasing the uncertainties and increasing reliabilitieswithin the project area. SWEPOS has since the collaboration back in 2004 supplied theSTA with project-based network-RTK services.The market is not the same today as it was in 2004 and there are more service providersactive in Sweden. This thesis intends to find out if this new market means that there areother alternatives to SWEPOS with regards to the STA’s requirements for project-basednetwork-RTK. This is done through a technical comparison of the different serviceprovider’s measurement uncertainties and their measurement accuracies as well as acomparison of their surrounding infrastructure and the subjective user experience.Similar studies have been conducted before (Edwards et al., 2010) (Martin andMacGovern, 2012) (Saeidi, 2012), but never in Sweden nor with SWEPOS as one of theservice providers as it is only available in Sweden. Neither have they had a focus onmeasurement uncertainties and accuracies in a project-based network-RTK net. Theyhave all concluded that there were no significant differences between any of the serviceproviders compared, in both the measurement uncertainties and accuracies.For the technical part of this thesis, measurements were conducted at four sites: two atdifferent locations within the area of a former, STA project-site, one within the regularnet and the final site outside the entire net, with the amount of collected data varying forthe different sites. Five different GNSS receivers of different brands were used for themeasurements to make it as general as possible.The results show that there are slight differences in the height uncertainty, but the scopeof this thesis does not permit the full correlation study needed to determine if thesedifferences are significant. There does not seem to be any differences in the accuracies ofthe service provider. Some of the sites with less data collected show contradictoryevidence to this statement, but it is deemed that these deviations are more likely relatedto something other than the service providers, such as human interference or errors.Large differences exist in the user experience and surrounding infrastructure, an areawhere SWEPOS at the moment has a clear lead. This is believed to be due to SWEPOSprimarily being a network-RTK service provider and thus allocating more resources andpersonnel, whilst the other service providers also serve as equipment vendor andmaintainers.Combining the two comparison parts leads to the overall conclusion that with theservice providers in their current state with the requirements of the STA specified intheir current state, only SWEPOS is a viable alternative as a supplier of project-basednetwork-RTK. But this is something that could change with relative ease depending on ifthe other service providers allocate more resources.
Nätverks-RTK är en metod för relativ mätning med hjälp av GNSS som ger användare istora områden ett enkelt sätt att förbättra osäkerheterna i sina mätningar. I början av2000 talet då frågan om alternativa lösningar till stomnät på marken aktualiseradesuppfyllde inte tillgängliga nätverks-RTK-lösningar Trafikverkets (TrV) krav påmätningar när det gäller dess större och/eller mer komplexa projekt. Något som leddetill att konceptet projektbaserad nätverks-RTK infördes i Sverige av TrV i samarbetemed tjänsteleverantören SWEPOS 2004. Detta koncept förbättrar vanlig nätverks-RTKgenom att minska osäkerheterna ytterligare och öka tillförlitligheten inom ett mindreprojektområde. SWEPOS har sedan detta samarbete 2004 levererat projektbaseradenätverks-RTK tjänster till TrV.Marknaden är inte samma dag som den var 2004 och det finns fler verksammatjänsteleverantörer i Sverige. Detta examensarbete avser att ta reda på om denna nyamarknad innebär att det finns andra alternativ till SWEPOS med avseende på de kravTrV har på projektbaserad nätverks-RTK. Något som sker genom en teknisk jämförelseav de olika tjänsteleverantörernas mätosäkerheter och deras noggrannheter samt enjämförelse av deras omgivande infrastruktur och den subjektiva användarupplevelsen.Liknande studier har gjorts tidigare (Edwards et al., 2010) (Martin och MacGovern2012) (Saeidi, 2012), men aldrig i Sverige och med SWEPOS som ett avjämförelseobjekten. De har inte heller haft fokus på mätosäkerheter och noggrannheterunder projektbaserade nätverks-RTK förhållanden. De har alla haft samma slutsats: attdet inte finns några signifikanta skillnader mellan de jämförda tjänsteleverantörerna.För den tekniska jämförelsen har mätningar utförts på fyra platser: två inom ettbefintligt TrV projektområde, en i det ordinarie nätet och den sista utanför hela nätet,där den insamlade datamängden varierar för de olika platserna. Fem olika GNSSmottagareav olika märken användes för att göra mätningarna så allmänna som möjligt.Resultaten visar att det finns små osäkerhetsskillnader i höjd, men för att avgöra omdessa skillnader är signifikanta eller ej så skulle en fullständig korrelationsanalys av deolika tjänsteleverantörerna behövas, något som inte ryms inom detta arbete. Det verkarinte heller finnas några signifikanta skillnader i noggrannhet hos tjänsteleverantören.Några av platser med mindre mängd insamlad data uppvisar motsägande resultat, mendetta bedöms bero mer på andra faktorer än tjänsteleverantörer i sig, såsom mänskligpåverkan etc.Användarupplevelsen och tjänsteleverantörernas omgivande infrastruktur uppvisarstörre skillnader, där SWEPOS för tillfället har ett klart övertag. Detta tros bero påSWEPOS främst är en tjänsteleverantör av nätverks-RTK och därmed har merdedikerade resurser och personal, men de andra tjänsteleverantörerna även agerarleverantörer/försäljare av utrustning.En kombination av de två jämförelsedelarna leder till en mer generell slutsats att medalla tjänsteleverantörer i sina nuvarande tillstånd alternativt utan en eventuellomformulering av TrVs krav, är enbart SWEPOS ett alternativ som leverantör avprojektbaserad nätverks-RTK lösningar till TrV. Men detta är något som kan förändrasmed relativ snabbt beroende på om andra tjänsteleverantörerna avsätter mer resursereller om kraven formuleras om.

Real-Time Kinematic (RTK) positioning is a technique used to provide precise positioning services at centimetre accuracy level in the context of Global Navigation Satellite Systems (GNSS). While a Network-based RTK (N-RTK) system involves multiple continuously operating reference stations (CORS), the simplest form of a NRTK system is a single-base RTK. In Australia there are several NRTK services operating in different states and over 1000 single-base RTK systems to support precise positioning applications for surveying, mining, agriculture, and civil construction in regional areas. Additionally, future generation GNSS constellations, including modernised GPS, Galileo, GLONASS, and Compass, with multiple frequencies have been either developed or will become fully operational in the next decade. A trend of future development of RTK systems is to make use of various isolated operating network and single-base RTK systems and multiple GNSS constellations for extended service coverage and improved performance. Several computational challenges have been identified for future NRTK services including: • Multiple GNSS constellations and multiple frequencies • Large scale, wide area NRTK services with a network of networks • Complex computation algorithms and processes • Greater part of positioning processes shifting from user end to network centre with the ability to cope with hundreds of simultaneous users’ requests (reverse RTK) There are two major requirements for NRTK data processing based on the four challenges faced by future NRTK systems, expandable computing power and scalable data sharing/transferring capability. This research explores new approaches to address these future NRTK challenges and requirements using the Grid Computing facility, in particular for large data processing burdens and complex computation algorithms. A Grid Computing based NRTK framework is proposed in this research, which is a layered framework consisting of: 1) Client layer with the form of Grid portal; 2) Service layer; 3) Execution layer. The user’s request is passed through these layers, and scheduled to different Grid nodes in the network infrastructure. A proof-of-concept demonstration for the proposed framework is performed in a five-node Grid environment at QUT and also Grid Australia. The Networked Transport of RTCM via Internet Protocol (Ntrip) open source software is adopted to download real-time RTCM data from multiple reference stations through the Internet, followed by job scheduling and simplified RTK computing. The system performance has been analysed and the results have preliminarily demonstrated the concepts and functionality of the new NRTK framework based on Grid Computing, whilst some aspects of the performance of the system are yet to be improved in future work.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os avanços tecnológicos nos métodos de posicionamento têm possibilitado o desenvolvimento de metodologias que viabilizam a sua utilização pelo usuário numa diversidade de aplicações. Um dos métodos de posicionamento GNSS (Global Navigation Satellite System) de grande destaque é o RTK (Real Time Kinematic) utilizando o conceito de rede de estações. Esse método utiliza a infra-estrutura de uma rede de estações de referência, para disponibilizar correções ao usuário. O conceito clássico do RTK tem como princípio básico a alta correlação dos erros provocados pela ionosfera, troposfera e órbita dos satélites na estação de referência e em uma estação próxima de interesse. No entanto, com o afastamento entre o usuário e a estação base, a eficiência do método é degradada, pois a correlação dos erros é reduzida. Mas, quando se utiliza uma rede de estações de referência, pode-se realizar a modelagem dos erros na área de abrangência da rede. Esta concepção é denominada de RTK em Rede. No que concerne a rede de estações de referência GNSS, utilizou-se a rede estabelecida no oeste do estado de São Paulo (rede GNSS-SP). O software adotado para realizar o processamento em rede foi o GPSNet na versão 2.73. Outra questão levantada foi com relação aos padrões disponíveis para a transmissão dos dados ao usuário, tais como o RTCM e CMR, mostrando as evoluções e aplicações. A questão do enlace de comunicação (link) também foi abordada, mostrando os principais tipos disponíveis, mas com ênfase na telefonia móvel que foi utilizada para transmitir os dados via internet. Foram conduzidos vários experimentos...
Technological advances in positioning methods have enabled the development of methodologies that allow its use in a great variety of applications. One method of GNSS (Global Navigation Satellite System) positioning of high performance is the RTK (Real Time Kinematic) network. This method uses the infrastructure of a network of reference stations. The original concept of RTK is the high correlation of the errors caused by ionosphere, troposphere and satellite orbit at a reference station and at a nearby station of interest. However, increasing the distance between the user and the base station, the efficiency of the method is degraded, because the error correlation is reduced. But when using a network of reference stations, a better error modeling in the area of the network is possible. This concept is the so called Network RTK. Regarding the network of GNSS reference stations, in this work the established network in the western state of São Paulo (GNSS network-SP) was used. The software adopted to perform the tests in the network was that GPSNet, version 2.73. Another issue raised during the investigation was related to the available standards for transmitting data to the user, such as CMR and RTCM. The developments and applications were presented. The issue of communication link (link) has been addressed, showing the main available types, but with emphasis on mobile phone that was the technology used to transmit data via the Internet. Several experiments were conducted in different locations to examine the integrity, availability and accuracy for RTK positioning and RTK network. The experiments performed with RTK and RTK network (using the concept of VRS (Virtual Reference Station)) showed some problems, probably related to the density of the network. Among them the accuracy, the initialization time span more than expected or even... (Complete abstract click electronic access below)

The Global Positioning System (GPS) has been widely used for precise positioning applications throughout the world. However, there are still some limiting factors that affect the performance of satellite-based positioning techniques, including the ionosphere. The GPS Network-RTK (NRTK) concept has been developed in an attempt to remove the ionospheric bias from user observations within the network. This technique involves the establishment of a series of GNSS reference stations, spread over a wide geographical region. Real time data from each reference station is collected and transferred to a computing facility where the various spatial and temporal errors affecting the GNSS satellite observations are estimated. These corrections are then transmitted to users observations in the field. As part of a Victorian state government initiative to implement a cm-level real time positioning service state-wide, GPSnet is undergoing extensive infrastructure upgrades to meet high user demand. Due to the sparse (+100km) configuration of GPSnet's reference stations, the precise modelling of Victoria's ionosphere will play a key role in providing this service. This thesis aims is to develop a temporal model for the ionospheric bias within a Victorian NRTK scenario. This research has analysed the temporal variability of the ionosphere over Victoria. It is important to quantify the variability of the ionosphere as it is essential that NRTK corrections are delivered sufficiently often with a small enough latency so that they adequately model variations in the ionospheric bias. This will promote the efficient transmission of correctional data to the rover whilst still achieving cm-level accuracy. Temporal analysis of the ionosphere revealed that, during stable ionospheric conditions, Victoria's double differenced ionospheric (DDI) bias remains correlated to within +5cm out to approximately two minutes over baselines of approximately 100km. However, the data revealed that during more disturbed ionospheric conditions this may decrease to one minute. As a preliminary investigation, four global empirical ionospheric models were tested to assess their ability to estimate the DDI bias. Further, three temporal predictive modelling schemes were tested to assess their suitability for providing ionospheric corrections in a NRTK environment. The analysis took place over four seasonal periods during the previous solar maximum in 2001 and 2002. It was found that due to the global nature of their coefficients, the four global empirical models were unable to provide ionospheric corrections to a level sufficient for precise ambiguity resolution within a NRTK environment. Three temporal ionospheric predictive schemes were developed and tested. These included a moving average model, a linear model and an ARIMA (Auto-Regressive Integrated Moving Average) time series analysis. The moving average and ARIMA approaches gave similar performance and out-performed the linear modelling scheme. Both of these approaches were able to predict the DDI to +5cm within a 99% confidence interval, out to an average of approximately two minutes, on average 90% of the time when compared to the actual decorrelation rates of the ionosphere. These results suggest that the moving average scheme, could enhance the implementation of next generation NRTK systems by predicting the DDI bias to latencies that would enable cm-level positioning.

Från den 1 april 2006 har SWEPOS kompletterat den befintliga nätverks-RTK-tjänsten, som dittills levererat RTK-data för GPS, med ett alternativ där RTK-data för GPS/GLONASS levereras. En del användare har rapporterat att de upplever att GPS/GLONASS inte tillför något och även att det ibland kan ta längre tid att få fixlösning. Andra användare hävdar att de nu kan använda nätverks-RTK på platser där de tidigare inte kunde mäta och är mycket positiva till GPS/GLONASS.

Syftet med detta examensarbete var att undersöka hur tillgängligheten för satellitmätning, positionsnoggrannheten och initialiseringstiden påverkades i öppna respektive störda miljöer med GPS/GLONASS jämfört med enbart GPS vid användandet av nätverks-RTK-tjänsten. Undersökningen har utförts med tre olika fabrikat av GNSS-mottagare (Leica, Topcon och Trimble), vilket även medger att en jämförelse mellan dessa till viss utsträckning kan göras.

I studien gjordes totalt 1 440 mätningar på sex punkter med kända positioner och med olika grad av sikthinder. Fixlösning uppnåddes inte inom 180 sekunder för 206 (77 för GPS/GLONASS och 129 för GPS) av de 1 440 mätningarna.

De extra GLONASS-satelliterna tillför en klar fördel när det gäller möjligheten att mäta i störda miljöer. När det gäller initialiseringstid så är dessa kortare för GPS/GLONASS. GLONASS-satelliterna ger ingen förbättring av positionsnoggrannheten. Det är till och med så att GPS får något bättre kvalitetstal i både plan och höjd i denna studie (1-3 mm bättre). För de olika fabrikaten kan det konstateras att precision och noggrannhet är likvärdiga i både plan och höjd för alla tre märken.

On the 1st of April 2006, SWEPOS complemented the existing network RTK service with corrections for the Russian satellite system GLONASS. The service had so far only provided corrections for GPS. Some users have claimed that GPS/GLONASS do not contribute at all and also that the time for initialization sometimes can be longer. However, other users insist on that they now can use network RTK in areas that earlier were impossible and they are very favourable of GPS/GLONASS.

The purposes of this diploma work were to study and examine measurements using GPS and GPS/GLONASS in areas with different degrees of visual obstacles. Corrections were provided by SWEPOS Network RTK service and availability of satellites, accuracy of position and time for initialization were evaluated. The study has been conducted with three different brands of GNSS receivers (Leica, Topcon and Trimble), which also to some extent makes a comparison between the three brands possible.

A total number of 1 440 field measurements were made on six well-known points with different degrees of visual obstacles. A fixed solution was not accomplished within 180 seconds for 206 (77 for GPS/GLONASS and 129 for GPS) of the 1 440 measurements.

The additional GLONASS satellites provide an apparent advantage regarding the possibility to measure in disturbed environments. The time for initialization is shorter for GPS/GLONASS. The GLONASS satellites do not give any improvement in accuracy of position. On the contrary, GPS receives slightly better accuracy numbers in quality for both horizontal and vertical readings (1-3 mm better). Regarding the different brands, it was found that the precision and accuracy were similar in both plane and height for all three brands.

Orientador: João Francisco Galera Monico
Banca: Leonardo Castro de Oliveira
Banca: Mauro Issamu Ishikawa
Resumo: Os avanços tecnológicos nos métodos de posicionamento têm possibilitado o desenvolvimento de metodologias que viabilizam a sua utilização pelo usuário numa diversidade de aplicações. Um dos métodos de posicionamento GNSS (Global Navigation Satellite System) de grande destaque é o RTK (Real Time Kinematic) utilizando o conceito de rede de estações. Esse método utiliza a infra-estrutura de uma rede de estações de referência, para disponibilizar correções ao usuário. O conceito clássico do RTK tem como princípio básico a alta correlação dos erros provocados pela ionosfera, troposfera e órbita dos satélites na estação de referência e em uma estação próxima de interesse. No entanto, com o afastamento entre o usuário e a estação base, a eficiência do método é degradada, pois a correlação dos erros é reduzida. Mas, quando se utiliza uma rede de estações de referência, pode-se realizar a modelagem dos erros na área de abrangência da rede. Esta concepção é denominada de RTK em Rede. No que concerne a rede de estações de referência GNSS, utilizou-se a rede estabelecida no oeste do estado de São Paulo (rede GNSS-SP). O software adotado para realizar o processamento em rede foi o GPSNet na versão 2.73. Outra questão levantada foi com relação aos padrões disponíveis para a transmissão dos dados ao usuário, tais como o RTCM e CMR, mostrando as evoluções e aplicações. A questão do enlace de comunicação (link) também foi abordada, mostrando os principais tipos disponíveis, mas com ênfase na telefonia móvel que foi utilizada para transmitir os dados via internet. Foram conduzidos vários experimentos... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Technological advances in positioning methods have enabled the development of methodologies that allow its use in a great variety of applications. One method of GNSS (Global Navigation Satellite System) positioning of high performance is the RTK (Real Time Kinematic) network. This method uses the infrastructure of a network of reference stations. The original concept of RTK is the high correlation of the errors caused by ionosphere, troposphere and satellite orbit at a reference station and at a nearby station of interest. However, increasing the distance between the user and the base station, the efficiency of the method is degraded, because the error correlation is reduced. But when using a network of reference stations, a better error modeling in the area of the network is possible. This concept is the so called Network RTK. Regarding the network of GNSS reference stations, in this work the established network in the western state of São Paulo (GNSS network-SP) was used. The software adopted to perform the tests in the network was that GPSNet, version 2.73. Another issue raised during the investigation was related to the available standards for transmitting data to the user, such as CMR and RTCM. The developments and applications were presented. The issue of communication link (link) has been addressed, showing the main available types, but with emphasis on mobile phone that was the technology used to transmit data via the Internet. Several experiments were conducted in different locations to examine the integrity, availability and accuracy for RTK positioning and RTK network. The experiments performed with RTK and RTK network (using the concept of VRS (Virtual Reference Station)) showed some problems, probably related to the density of the network. Among them the accuracy, the initialization time span more than expected or even... (Complete abstract click electronic access below)
Mestre

Eftersom intresset och användandet av satellitbaserad positionering ökat under de senaste åren så är det av stort intresse att utveckla och förbättra de globala navigationssystemen, samt användandet av dessa. På uppdrag av Lantmäteriet i Gävle så har i denna studie en utvärdering av L2C-signalen, som är GPS andra civila signal, genomförts för att undersöka dess möjligheter till ökad tillgänglighet samt minskade mätosäkerheter, vid mätning med nätverks-RTK. Detta inkluderar även en undersökning av hur signalen kan användas i olika fabrikat av GNSS-utrustning. Fabrikaten som testats är Leica, Topcon samt Trimble, vilka kan anses täcka större delen av den svenska marknaden för RTK-utrustning.   Datainsamlingen genomfördes i Mårtsbo där sju kända punkter som ingår i ett av Lantmäteriets testnät mättes in i flera omgångar för att få flera oberoende mätningar, både med och utan L2C-signalen. Samtliga punkter ligger belägna i skogsmiljö, men är av varierande svårighetsgrad. I efterbearbetningen beräknades och jämfördes dels standardosäkerheter och avvikelser mellan de två signalinställningarna, men även medeltid med erhållen fixlösning samt initialiseringstider. Testerna av implementeringen av signalen för de tre olika fabrikaten skedde på SWEPOS-driften på Lantmäteriet i Gävle, där signalförstärkare finns monterad på taket.   Resultaten från fältmätningarna ger en antydan till förbättring av både tiden till fixlösning samt mätosäkerheter vid inkluderandet av L2C-signalen, framförallt vid de punkter som klassats som svårast. Resultatet uppfyller dock inte riktigt de på förhand höga förhoppningarna, som utlovats av GPS samt diverse litteratur, då signalen enligt dessa borde ha gett en förbättring även på de lättare punkterna. Signalen visade sig gå att använda i alla tre fabrikat som testats, dock på något olika sätt.
Since applications of satellite based positioning techniques are constantly increasing, it is important to study the development of GNSS which is improving as well. National Land Survey of Sweden (NLSS) supported this study in order to evaluate the second civil signal from GPS (L2C). The idea is to investigate how using L2C increases the accessibility and accuracy in network-RTK. This also includes an evaluation of how the signal works in different brands of positioning equipment. The equipment that has been selected for this test includes models from the three most established brands in Sweden: Leica, Topcon and Trimble. The data collection was carried out in the area of Mårtsbo where seven well known points were measured, both with and without the L2C signal, for several times. All the measured points are located in forest environments, but with different levels of visibility. In the data post processing many parameters were considered for comparing the results such as: uncertainties, differences from known coordinates, time of fixed solution and initialization time. The tests of how the signal works in the three selected receiver models were carried out at the office of NLSS where a permanent reference antenna is mounted. The result of the field study indicates some improvement regarding the measurement uncertainties and time to fixed solution when including the L2C-signal, especially on those points classified as the most problematic. However, the result does not really fulfill the predicted expectations as hoped, where much bigger advantages for the L2C signal should have been shown. The signal could be used in all the three tested GNSS-equipment, despite of slightly different methods and features.

Nätverks-RTK (Real-Time Kinematic) är en metod för positionsbestämning med Global Navigation Satellite System (GNSS) i realtid. Metoden kräver att en driftledningscentral kan kommunicera med de GNSS-mottagare som använder referensstationsnätet, för att bland annat skicka ut korrigerade GNSS-data. I Sverige erbjuder SWEPOS, ett nät av fasta referensstationer, en tjänst för nätverks-RTK-mätning, som förväntas ge en mätosäkerhet på mindre än 15 mm i plan och 25 mm i höjd (över ellipsoiden) (med täckningsfaktorn k = 1 i bägge fallen). Den teknik som idag används av SWEPOS för att utföra positionsbestämning av GNSS-mottagare är Virtuell Referensstation (VRS). VRS kräver tvåvägskommunikation eftersom mottagaren skickar in sin absoluta position till nätverks-RTK-programvaran hos driftledningscentralen, var beräkningarna av korrektionsdata sker, innan de skickas tillbaka till mottagaren. Det finns ett annat alternativ som möjliggör envägskommunikation, nämligen nätverks-RTK-meddelande. Då sänds observationsdata, i form av korrektioner, ut till mottagaren som utför positionsberäkningarna. Syftet med det här examensarbetet var att undersöka nätverks-RTK-meddelande för GNSS-mottagare av tre olika fabrikat med avseende på initialiseringstider, mätosäkerhet, avståndsberoende från närmaste masterstation, och GLONASS-satelliters deltagande i positionsbestämningen. I studien ingick även att utföra några jämförande mätningar med VRS. Undersökningarna gjordes genom upprepade nätverks-RTK-mätningar med GNSS-mottagare från Leica Geosystems, Trimble och Topcon, på tre kända punkter sydöst om Gävle. Tre mätmetoder användes, nätverks-RTK-meddelande med automatiskt nät (tvåvägskommunikation) och statiskt nät (envägskommunikation), samt VRS. De tre mätpunkterna valdes så att avståndet, till den referensstation som användes som en så kallad masterstation, varierade. Studien visade att initialiseringstiderna skiljde mellan de tre mottagarfabrikaten. En anledning till detta var att varje mottagare ominitialiserades från olika lösningslägen. Generellt var mätosäkerheten något högre för statiskt nät. Mätosäkerheten var omkring 11 mm i plan och 19 mm i höjd med det automatiska nätet, samt 13 mm respektive 22 mm i det statiska nätet. Fabrikaten emellan, låg Leica och Trimble på samma nivå, medan Topcon hade ett generellt problem för det statiska nätet, vilket det inte fanns möjlighet att närmare utreda orsaken till. Resultatet visade även att mätosäkerheten påverkas av avståndet till använd masterstation. I några fall var dessa förhållanden linjära. Vid några tillfällen användes inte GLONASS-satelliter i positionsbestämningen.
Network RTK (Real-Time Kinematic) is a method of positioning with Global Navigation Satellite System (GNSS) in real-time. The method requires that a control centre can communicate with the GNSS receiver, which is using the reference station network, for example to send out corrected GNSS data. In Sweden, SWEPOS, which is a network of permanent reference stations for GNSS, offers a service for Network RTK measurement. This is expected to give an uncertainty of less than 15 mm in plane and 25 mm in (ellipsoidal) height (with the coverage factor k = 1 in both cases). The technology currently used by SWEPOS, to perform positioning of a GNSS receiver, is Virtual Reference Station (VRS). VRS requires two-way communication because the receiver submits its navigated location to the control centre, where the calculations of correction data are made, before they are sent back to the receiver. Another alternative is Network RTK messages which make use of one-way communication. Then the observation data are transmitted to the receiver, which performs determination of its position. The purpose of this thesis was to investigate the network RTK messages with GNSS receivers from three different manufacturers with regard to time to fix ambiguities, measurement uncertainty and its dependence on the distance from the master station, and GLONASS satellites presence in the positioning. Also included in the study was the performance of comparative measurements with VRS. The investigations were conducted through repeated network RTK measurements with GNSS receivers from Leica Geosystems, Trimble and Topcon, at three known points south-east of Gävle. Three methods were used, network RTK message with automatic and static networks, and VRS. The three measurement points were chosen so that the distance to the reference station that was used as the so-called master station, varied. The study showed that the time to fix ambiguities differed between the three brands. One reason for this was that each receiver was reinitialized from different steps in the initialization process. In general, the uncertainty in the measurement was slightly higher for the static network. The uncertainty was about 11 mm in plane and 19 mm in height with the automated network, and 13 mm and 22 mm respectively in the static network. Leica and Trimble were at the same level, while Topcon had general problems for the static network, which there was no possibility to closer investigate the reason for. The results also showed that the uncertainty is influenced by the distance to used master station. In some cases, this relationship is linear. On some occasions, GLONASS satellites were not included in the positioning.

Sverige har under lång tid haft flera olika koordinatsystem, både nationella och lokala. Nu genomförs en övergång till ett gemensamt koordinatsystem som kallas SWEREF 99. I Norrtälje kommun finns stomnät som är noterade i ett flertal olika koordinatsystem, med ursprung i tidigare förrättningar. Åtskilliga av dessa har dålig orientering i kända nationella koordinatsystem men däremot god inre noggrannhet. I detta arbete väljs 12 stomnät för transformation till SWEREF 99 18 00. Detta görs genom att passpunkter mäts in med GNSS-teknik. De inmätta punkterna används sedan för att transformera stomnäten som de är noterade i. Detta gör att i framtiden kan till exempel husutsättningar i de aktuella områdena utföras med enbart GNSS-teknik. Stomnäten som väljs finns på norra delen av ön Vätö i Norrtälje kommun. GNSS-utrustningen som används för att mäta in punkterna är Leica 1203 nätverks-RTK. De valda passpunkterna mäts in vid två tillfällen med minst 45 minuters mellanrum. Vid varje tillfälle görs 10 mätningar. Sedan beräknas medelvärdet av 20 mätningar. När alla punkter väl har mätts in görs transformationer från tre olika från-system till SWEREF 99 18 00. De tre från-systemen är RT 38 2,5 gon V, RT R09 0 gon och ett lokalt 1000/1000-system. Eftersom områdena som är noterade i RT 38 är dåligt orienterade gentemot varandra ger det dålig noggrannhet att transformera hela RT 38-området på en gång. Därför delas RT 38-området in i flera transformationsområden. När transformationen gjorts kontrollmäts fastighetsgränser i ett gränsområde där gränspunkternas koordinatsystem är osäkert. Avslutningsvis kontrollmäts en Rix 95-punkt med namnet Klockarängsberget (Rix 95-punktnummer: 119741) som finns på södra delen av Vätö.
During the last century different coordination systems have been used in Sweden. Today a common coordination system (SWEREF 99) is used. In the municipality of Norrtälje, core networks are listed in different coordination systems that are generated from different earlier missions. These networks normally have poor orientation in the known coordination system; however, the internal accuracy is used to be good. In this study, some of the core networks have been selected to be converted to SWEREF 99 18 00. The conversion has been done by measuring points using the GNSS technology, the measured points were then used to transfer the core network to SWEREF 99 18 00. This means that in the future, staking out a building in the area can be performed solely by GNSS technology. The chosen core networks are located on a part of the island Vätö in the municipality of Norrtälje. The GNSS equipment used to measure the points with was the Leica 1203 RTK network. The selected points were measured on two occasions with a gap between the occasions of at least 45 minutes. Ten repeated measurements have been done on each point to increase the accuracy. The average of these twenty measurements has been used for conversion. After the measuring process, the transformation has been done from three different off-systems to SWEREF 99 18 00. The three off-systems were RT 38 2.5 gon V, RT R09 0 gon and a local 1000/1000-system. Since the areas listed in the RT 38 were poorly oriented towards each others, poor accuracy was achieved during the transformation of the entire RT 38 field at once. Therefore, the RT 38 area has been divided into a number of transformations-areas. When the transformation had been done, control measurements were made on a Rix 95-Point entitled Klockarängsberget (Rix 95-point numbers: 119 741) located on the southern part of Vätö. In addition, control measurements were made of housing estate border area, where the border points were uncertain.

Ett på marknaden nyligen introducerat GNSS-instrument är Leica GS18 T med inbyggd lutningskompensator, baserad på kombinerad GNSS- och tröghetsnavigeringsteknik (INS), som gör att mätstången med GNSS-instrumentet inte behöver centreras över den punkt som ska mätas in. Förutom att utföra snabbare mätningar möjliggör lutningskompensatortekniken inmätning av dolda punkter där konventionell GNSS-mätning normalt inte är möjlig utan mer tidskrävande indirekta metoder måste användas. Instrumentet har även avancerad GNSS-signalspårningsteknik som möjliggör mätning i svåra miljöer. På uppdrag av Lantmäteriet har som ett inledande test av Leica GS18 T lägesosäkerheten vid nätverks-RTK-mätning med lutande mätstång undersökts i tre situationer: vid mätning i olika lutningsgrader i både normal och svår mätmiljö, vid lutning mot olika väderstreck för att studera lutningsriktningens eventuella inverkan samt vid inmätning av hushörn som exempel på ett tillämpningsområde. I det senare fallet jämfördes resultatet med vad som erhålls med en indirekt metod, i detta fall dold punkt genom inbindning, som mätning med lutningskompensator möjligen skulle kunna ersätta. Analys av lägesosäkerheten baseras på beräkningar av standardosäkerhet, RMS (Root Mean Square) och medelavvikelse. Mätningarna med olika lutningsgrader på mätstången resulterade i en lägesosäkerhet på cm-nivå i plan för både normal och svår mätmiljö. Lägesosäkerheten i höjd hamnade på mm-nivå i normal mätmiljö och på cm-nivå i svår mätmiljö. Vidare pekar resultaten på att mätstångens lutningsriktning påverkar lägesosäkerheten. Orsaken till detta är dock inte klarlagd och kräver vidare undersökning. Inmätning av hushörn gav en medelavvikelse på ca 12 mm när mätstången lutades 30°. Metoden dold punkt genom inbindning gav generellt en lägre medelavvikelse, även om skillnaden är relativt liten (4 mm som lägst). En sammanfattande bedömning är att instrumentet fungerar bra vid detaljmätning, åtminstone vid positionsosäkerhetskrav på cm-nivå.
A recently introduced GNSS instrument on the market is Leica GS18 T with tilt compensation, based on GNSS/Inertial Navigation Systems (INS) integration, with no need to centre the survey pole with the GNSS instrument over the target point being measured. Besides making surveying faster, the tilt compensation technique enables measuring of hidden points where the use of conventional GNSS measuring normally is not possible without more time-consuming methods. The instrument also has advanced GNSS signal tracking which makes surveying in challenging environments possible. In this study, the Leica GS18 T has on behalf of Lantmäteriet been tested through studying the measurement uncertainty in network RTK measurement with tilted survey pole in three different situations: with the survey pole tilted in various degrees in both favourable and challenging survey environments; with tilt towards north, east, south and west to test if the tilt direction would affect the result; and for surveying of building corners as a possible field of application. In the latter case, the result was compared with what can be achieved with the conventional hidden point method using intersection of distances. The analysis of the measurement uncertainty was based on calculations of standard uncertainty, RMS (Root Mean Square) and mean deviation. The measurement uncertainty from the first part of the test was on cm-level horizontally, both in favourable and challenging survey environments, and in height on mm-level in favourable survey environment and on cm-level in challenging survey environment. Further, the results indicate that the tilt direction affects measurement uncertainty. The reason for this is not clarified and needs further investigation. The measurements of building corners resulted in a mean deviation of approximately 12 mm when the survey pole was tilted 30°. The hidden point method using intersection of distances generally resulted in lower mean deviation, even though the difference is relatively small (4 mm at best). To summarize, Leica GS18 T seems to be well suited for measuring with tilt in detailed surveying, at least if the requirements of position uncertainty is on cm-level.

Many high-accuracy regional GPS continuously operating reference (CORS) networks have been established globally. These networks are used to facilitate better positioning services, such as high accuracy real-time positioning. GPSnet is the first state-wide CORS network in Australia. In order to maximize the benefits of the expensive CORS geospatial infrastructure, the state of Victoria in collaboration with three universities (RMIT University, the University of NSW and the University of Melbourne) embarked on research into regional atmospheric error modelling for Network-based RTK (NRTK) via an Australian Research Council project in early 2005. The core of the NRTK technique is the modelling of the spatially-correlated errors. The accuracy of the regional error model is a determining factor for the performance of NRTK positioning. In this research, a number of error models are examined and comprehensively analysed. Among them, the following three models are tested: 1) the Linear Interpolation Method (LIM); 2) the Distance-Based interpolation method (DIM); and 3) the Low-order surface model (LSM). The accuracy of the three models is evaluated using three different observation sessions and a variety of network configurations of GPSnet. Results show that the LIM and DIM can be used to significantly reduce the double-differenced (DD) residuals (up to 60% improvement), and the LIM is slightly better than the DIM (most at mm level). However the DD residuals with the LSM corrections are, in some cases, not only much worse than that of the LIM and DIM but also even must greater/worse than the DD residuals without any corrections applied at all. This indicates that there are no advantages by using the LSM for the error modelling for NRTK in GPSnet, even though it is the most commonly used method by researchers. The performance difference of the LIM for different GPSnet configurations is also tested. Results show that in most cases, the performance difference mainly caused by the number of reference stations used is not significant. This implies that more redundant reference stations may not contribute much to the accuracy improvement of the LIM. However, it may mitigate the station specific errors (if any). The magnitude of the temporal variations of both the tropospheric and ionospheric effects in GPSnet observations is also investigated. Test results suggest that the frequency of generating and transmitting the tropospheric corrections should not be significantly different from that for the ionospehric corrections. Thus 1Hz frequency (i.e. once every second) is recommended for the generation and transmission for both types of the atmospheric corrections for NRTK in GPSnet. The algorithms of the NRTK software package used are examined and extensive analyses are conducted. The performance and limitation of the NRTK system in terms of network ambiguity resolution are assessed. The methodology for generating virtual reference station (VRS) observations in the system is presented. The validation of the algorithms for the generated VRS observations is undertaken. It is expected that this research is significant for both the selection of regional error models and the implementation of the NRTK technique in GPSnet or in the Victorian region.

En dold punkt är en punkt som inte kan mätas direkt utan måste mätas indirekt med hjälp av t.ex. Global Navigation Satellite System (GNSS) eller totalstation. Det finns ett flertal olika metoder med GNSS och totalstation som passar till olika inmätningssituationer för att mäta en dold punkt. Mätning av dolda punkter med totalstation inträffar ofta i industrimiljöer där rör och liknande hänger i vägen för totalstationens siktlinje till mätobjektet. GNSS med nätverks-realtids kinematisk (nätverks-RTK) mätning, en metod som ökar inom mätningsjobb, är en bra metod för att indirekt mäta dolda punkter utomhus där det antingen är dålig mottagning av satellitsignaler eller inte är möjligt att ställa upp en antenn över punkten. Syftet med denna studie är att undersöka hur bra lägesosäkerhet det går att uppnå för mätning av dold punkt med GNSS och totalstation och även jämföra de olika metoderna som testas. Fem olika metoder beskrivs för att kunna bestämma en dold punkts koordinater med totalstation. Bl.a. en med stång och prismor för mätning i plan och höjd, som även kommer användas i denna studie. Lägesosäkerheten 0,1 mm i både plan och höjd bör kunna uppnås med den metoden. Metoder som kan användas med GNSS och nätverks-RTK är t.ex. en rak linje och dess bäring, skärningen av två raka linjer och skärningen av två längdmätningar. Med nätverks-RTK kan mätningar uppnå en lägesosäkerhet på millimeter-nivå baserat på SWEPOS nätverks-RTK-tjänst. Det är även viktigt med tidskorrelation mellan mätningar om de ska göras oberoende av varandra. Resultaten av lägesosäkerheten i denna studie kan sedan jämföras med de från tidigare studier, om liknande värden kan erhållas vid mätning av dold punkt och hur mycket de skiljer sig. Metoden med totalstation som testats i denna studie är en stång med två prismor på som hålls mot den dolda punkten. Prismorna på stången mättes in med totalstationen och med hjälp av punkternas koordinater kan bäringen mellan dem räknas ut, vektorn förlängs till den dolda punkten, och sedan kan den dolda punktens koordinater räknas ut. De metoder som testats med GNSS är beräkning med en rak linje och dess bäring och beräkning med dubbla längdmätningar. För både GNSS och totalstationsmätningarna har minsta kvadratmetoden använts för att beräkna den dolda punkten och dess lägesosäkerhet. Fyra olika varianter av totalstationsmätningarna utfördes. 0,7 m fast anlagd prismastång med manuell inriktning, 1,0 m fast anlagd prismastång med manuell inriktning, 1,0 m fast anlagd prismastång med automatisk inriktning och 1,0 m handhållen prismastång med manuell inriktning. Alla varianter utfördes i två mätningsomgångar. Lägesosäkerheten vid mätningar för en dold punkt med totalstation var i denna studie 1-2 mm i plan och runt 1 mm i höjd, lägst lägesosäkerhet gav manuell inriktning (0,7 m mellan prismorna) med 0,93 mm i plan och 0,79 mm i höjd. Vilken mätningsvariant som var bäst med totalstationsmätningarna varierade mellan mätningsomgångarna, men skillnaden dem emellan var inte så stor. Det är därför svårt att säga säkert vilken variant som ger bäst lägesosäkerhet med det antalet mätningar som utfördes i denna studie. Med GNSS erhölls osäkerheter på som lägst 7,3 mm där dubbla längdmätningar med stativ gav bäst resultat. Om GNSS-mottagaren placerades på ett stativ eller hölls upp med eller utan stödpinnar förändrade inte slutresultatet så mycket, men som väntat gav stativet lägst lägesosäkerhet.
A hidden point is a point that can´t be measured directly but must be measured indirectly using, for example, Global Navigation Satellite System (GNSS) or total station. There are several different methods with GNSS and total station that fit into different survey situations to survey a hidden point. Measurement of hidden points with total stations often occurs in industrial environments where pipes and the like hang in the way of the total station's line of sight to the measuring object. GNSS with network-Real-Time Kinematic positioning (network-RTK), a method that increases in measurement jobs, is a great way to indirectly measure hidden points outdoors where either poor reception of satellite signals or the ability to set an antenna over the point is not possible. The purpose of this study is to investigate how good measurement uncertainty it is possible to obtain when measuring hidden points with GNSS and total station and also compare the different methods tested. Five different methods are described to determine the coordinates of a hidden point with a total station. Among other things, one with a bar and prisms for measurements horizontally and in height, which will also be used in this study. Position uncertainty 0.1 mm both horizontally and in height should be achievable with that method. Methods that can be used with GNSS and network RTK are for example straight line and its bearing, the intersection of two straight lines and the intersection of two length measurements. With network RTK, measurements can achieve a position uncertainty in millimeters based on SWEPOS network RTK service. It is also important for time correlation between measurements to be made independently. The results of position uncertainty in this study can then be compared to those of previous studies, if similar values can be obtained when measuring hidden points and how much they differ. The method used for total station in this study is a bar with two prisms on it held against the hidden point. The prisms on the bar were measured with the total station and the bearing between them can be calculated with the help of the coordinates of the points, the vector is extended to the hidden point and then the coordinates of the hidden point can be calculated. The methods tested with GNSS are the calculation of a straight line and its bearing and calculation with double length measurements. For both GNSS and total station measurements, the least squares method has been used to calculate the hidden point and its measurement uncertainty. Four different alternatives of the total station measurements were performed. 0.7 m fixed prism bar with manual alignment, 1.0 m fixed prism bar with manual alignment, 1.0 m fixed prism bar with automatic alignment and 1.0 m hand-held prism bar with manual alignment. All alternatives were performed in two measuring rounds. Measurement uncertainty for measurements for a hidden point with total station in this study was 1-2 mm horizontally and around 1 mm in height, the lowest measurement uncertainty gave manual alignment (0.7 m between the prisms) with 0.93 mm horizontally and 0.79 mm in height. The measuring alternative which was the best with total station measurements varied between the two measuring rounds, but the difference between them was not that large. It is therefore difficult to say which method gives the best measurement uncertainty with the number of measurements performed in this study. GNSS received uncertainties of at lowest 7.3 mm where double length measurements with tripod yielded the best results. If the GNSS receiver was placed on a tripod or held up with or without support did not change the final result that much, but as expected, the tripod provided the lowest measurement uncertainty.

Les tumeurs de vessie suivent deux voies de progression tumorale. La voie des carcinomes in situ (CIS) qui progressent pour envahir la membrane basale puis le muscle, et la voie des tumeurs papillaires de bas grade qui progressent peu mais qui récidivent fréquemment. Environ 65% des tumeurs papillaires de bas grade présentent une mutation du gène FGFR3 et récemment des protéines de fusion FGFR3-TACC3 ont été observées dans les tumeurs de vessie (dans 10% des tumeurs invasives). Le rôle oncogénique du récepteur FGFR3 muté et de FGFR3-TACC3 a été démontré in vivo et in vitro. Cependant, les voies de signalisation du récepteur FGFR3 muté ou de FGFR3-TACC3 sont à l’heure actuelle très peu caractérisées. Dans ce contexte, deux approches ont été mises en place pour caractériser ces voies de signalisation. La première s’appuie sur l’étude de la phosphorylation des protéines p38, AKT et ERK1/2 par le récepteur FGFR3 muté (S249C) ou sauvage dans la lignée cellulaire fibroblastique NIH3T3, et a permis d’identifier les protéines p38 et AKT comme activées par le récepteur FGFR3 muté et nécessaire pour induire la transformation cellulaire. L’étude de l’activation de ces deux voies de signalisation a été réalisée dans des lignées cellulaires dérivées de tumeurs de vessie exprimant le récepteur FGFR3 muté ou FGFR3-TACC3 de manière endogène et a montré que leur activation était dépendante de celle du récepteur FGFR3. De plus nous avons montré que les protéines p38 et AKT sont impliquées dans le maintien d’une boucle de rétro-contrôle positive entre FGFR3 et MYC : l’activation de FGFR3 induit une surexpression de MYC qui en retour promeut l’expression de FGFR3. La seconde approche est basée sur une étude visant à identifier les partenaires protéiques de FGFR3 par spectrométrie de masse après immunoprécipitation de celui-ci qui avait été réalisée précédemment au laboratoire. L’analyse des données a permis l’obtention d’une liste de 60 protéines identifiées comme partenaires protéiques de FGFR3 avec une grande confiance. La construction d’un réseau à partir de cette liste n’a pas été possible (trop peu d’interactions existant entre ces protéines), nous avons donc développé un algorithme (PEPPER) en collaboration avec un étudiant en bio-informatique au laboratoire, Rémy Nicolle, pour proposer un réseau de signalisation de FGFR3.Les deux approches mises en place au cours de cette thèse nous ont permis de mieux caractériser les voies de signalisation du récepteur FGFR3. L’identification d’une boucle de rétrocontrôle entre FGFR3 et MYC a permis de mieux comprendre pourquoi le récepteur FGFR3 possède des propriétés oncogéniques, et de proposer les protéines p38 et AKT comme cibles thérapeutiques potentielles pour traiter les tumeurs de vessie exprimant le récepteur FGFR3 altéré. La construction du réseau de signalisation de FGFR3 via PEPPER donne une vue d’ensemble des voies de signalisation de FGFR3 et ouvre de nouvelles pistes à étudier
Bladder cancer progression can be divided in two main pathways. The pathway of In Situ Carcinoma (CIS) which progress through an invasion of the basement membrane and then the muscle and the pathway of Ta papillary tumors which change little but recur frequently after tumor resection. Approximately 65% of Ta papillary tumors harboring a FGFR3 mutation and recently FGFR3-TACC3 fusion proteins have been observed in bladder tumors (about 10% of bladder tumors). The oncogenic role of the mutated FGFR3 receptor and of the FGFR3-TACC3 fusion protein has been demonstrated in vivo and in vitro. However signaling pathways activated by the mutated FGFR3 receptor or by the FGFR3-TACC3 fusion protein are currently poorly characterized.In this context, two approaches have been developed to characterize these signaling pathways. The first is based on the study of p38, AKT and ERK1/2 phosphorylation by the mutated receptor (S249C) or the wild type receptor in the NIH3T3 fibroblastic cell line. This study allowed identifying p38 and AKT as activated by the mutated FGFR3 receptor. Moreover, activation of p38 and AKT by the mutated receptor is critical for cell transformation. Study of the activation of these two signaling has been realized in human bladder cancer cell lines endogenously expressing the mutated FGFR3 receptor or the FGFR3-TACC3 fusion protein. Moreover, we showed that p38 and AKT are involved in the maintenance of a FGFR3/MYC feedback positive loop: FGFR3 activation induce MYC over expression which in turns promotes FGFR3 expression. The second approach is based on a study whose aim was to identify FGFR3 proteins partners by mass spectrometry after a FGFR3 immunoprecipitation, which has been previously realized in the lab. Data analyze led to the obtaining of a list of 60 proteins identified has FGFR3 protein partners with a high confidence. Construction of a FGFR3 network with this list was not possible (too little interactions existing between these proteins), so we developed an algorithm (PEPPER) in collaboration with a student in bioinformatics in the lab, Remy Nicolle, to propose a FGFR3 signaling network.The two approaches developed during this thesis allowed us to better characterize the FGFR3 signaling pathways. Identification of a FGFR3/MYC feedback loop allowed us to better understand why the altered FGFR3 has oncogenic properties and to propose p38 and AKT as news promising therapeutic targets, to treat human bladder tumors harboring the altered FGFR3 receptor. Construction of the FGFR3 signaling network with the algorithme PEPPER give an overview of the FGFR3 signaling pathways and open new tracks to explore

Today, GNSS measurements play an important role in the surveying industry, and their use is ever increasing. Many different GNSS receivers and antenna manufacturers are on the market with new ones appearing. The purpose of this study is to investigate the level of measurement uncertainty of three different GNSS receivers: Leica GS15, Sokkia GCX2 and Satlab SL300. The method in this study is based mainly on the method proposed by HMK - Geodatakvalitet 2015 (Manual in measurement and map issues – Geographic data quality 2015 [author’s translation]) by Swedish Lantmäteriet for "Evaluation of measurement uncertainty in Network RTK [author’s translation]”. Some corrections and additions are made to this method but the basis of the method is retrieved from there. Formulas are used to calculate radial deviation and limit requirements for these. Even standard deviations and radial mean deviations as well as tolerances for these are calculated. The field measurements are made on two RIX 95-points. This is done repeatedly to get up to 20 measurements. The GNSS receivers are mounted on a tripod with a tribrach that is centered over the known points. The main finding from this study is that all investigated receivers, apart from four overriding values ​​for the Leica GS15, perform better than specified by their manufacturers. However, Sokkia GCX2 and Satlab SL300 are approved with uncertainties within the calculated tolerances. The Leica GS15 instrument is very close to meeting the demands but does not reach all the way. A committed error during the performed measurements with the Satlab SL300 makes its evaluation based on 19 instead of 20 measurements. Still, calculations are performed on the collected data that resulted in low measurement uncertainties well below the manufacturer's specified uncertainty. The study was conducted during five weeks in May and June 2017.

In this thesis, we propose a new protocol named Layered TCP with RTT Compensation (LTCP-RC, for short). LTCP-RC is a simple modification to the congestion window response of the high-speed protocol, Layered TCP (LTCP). In networks characterized by large link delays and high RTTs, LTCP-RC makes the LTCP protocol more scalable. Ack-clocked schemes, similar to TCP, suffer performance problems like long convergence time and throughput degradation, when RTT experienced by the flow increases. Also, when flows with different RTTs compete, the problem of unfairness among competing flows becomes worse in the case of high-speed protocols. LTCP-RC uses an RTT Compensation technique in order to solve these problems. This thesis presents a general framework to decide the function for RTT Compensation factor and two particular design choices are analyzed in detail. The first algorithm uses a fixed function based on the minimum RTT observed by the flow. The second algorithm uses an adaptive scheme which regulates itself according to the dynamic network conditions. Evaluation of the performance of these schemes is done using analysis and ns-2 simulations. LTCP-RC exhibits significant performance improvement in terms of reduced convergence time, low drop rates, increased utilization in presence of links with channel errors and good fairness properties between the flows,. The scheme is simple to understand, easy to implement on the TCP/IP stack and does not require any additional support from the network resources. The choice of parameters can be influenced to tune the RTT unfairness of the scheme, which is not possible in TCP or other high-speed protocols. The flexible nature of the analysis framework has laid the ground work for the development of new schemes, which can improve the performance of the window based protocols in high delay and heterogeneous networks.

Mutation and over-expression of Receptor Tyrosine Kinases (RTKs) or the proteins they regulate serve as oncogenic drivers in diverse cancers. RTKs catalyze the transfer of phosphate from ATP to the hydroxyl group on tyrosine. The proximal stretch of amino acids including this post translational modification is then able to be recognized by SH2 and PTB domains. Chapter 1 details our work to better understand RTK signaling and its link to oncogenesis using protein microarrays to systematically and quantitatively measure interactions between virtually every SH2 or PTB domain encoded in the human genome and all known sites of tyrosine phosphorylation on 40 out of the 53 Receptor Tyrosine Kinases. Chapter 2 expands upon this work to study the next layer of binding among SH2 and PTB domain-containing adaptor proteins themselves. We found that adaptor proteins, like RTKs, have many high affinity bindings sites for other adaptor proteins. In addition, proteins driving oncogenesis, including both receptors and adaptor proteins, tend to be highly interconnected via a network of SH2 and PTB domain-mediated interactions. Our results suggest that network topological properties such as connectivity can be used to prioritize new drug targets in these well-studied signaling networks. Despite the extensive work presented here on experimentally determining interactions, we nevertheless are unable to keep up with the discovery of new sites of tyrosine phosphorylation by high throughput mass spectrometry as well as their mutation in cancer discovered by next generation tumor sequencing approaches. Chapter 3 introduces work in progress to build a unified predictive model of SH2 domain interactions via integration of diverse data sets of binding as well as crystal structures of domain-peptide interactions. This model will enable researchers discovering new phosphorylation events or mutations to be able to predict potential interaction partners and thereby elucidate novel functional mechanisms.
Chemistry and Chemical Biology

Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, 2019, In conjunction with the Leaders for Global Operations Program at MIT
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2019, In conjunction with the Leaders for Global Operations Program at MIT
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 100-107).
On average, an airline starts to place orders or aircraft within 3 - 10 years before the expected delivery date. During this time, there could be changes given the natural response of the airlines to continuously refine their fleet plan. This behavior implies many possible scenarios that aircraft manufacturers would like to understand and predict in order to improve their backlog management initiatives. Furthermore, demand estimation is always a powerful lever in any production system because it allows the manufacturer to be prepared to address the customer's needs. An airline's network and fleet are dependent on each other. The network is highly dependent on the capabilities of the available fleet but also, the fleet is built considering the network strategy of an airline. Giving this relationship this project aims to develop a set of predictive models based on network-related variables that allow to forecast the RPK growth of an airline in the following 7 years. Most of the available forecast for air passenger traffic focus on economic variables such as fuel price, GDP of the countries, trade index and population among others. This project wanted to explore if network variables had any relationship with future RPKs for an airline. After the analysis of historical data of more than 400 carriers from 2010 to 2017, the results show that although mild, there is an influence of these variables and we could use the resulting forecast with a solid reliability. Furthermore, the final coefficients show more influence of these variables for short-haul (less than 2500 nautical miles) and Economy markets than long-haul and Business markets. For Boeing and its current backlog size of more than 5,800 aircraft [1], the resulting models represent another tool that will aid the company in making data driven decisions regarding aircraft production, new orders to come, evaluation of current and potential customers, and other business analysis.
by Norányeli Paola Molina Realpe.
M.B.A.
S.M.
M.B.A. Massachusetts Institute of Technology, Sloan School of Management
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

This thesis examines the current implementations for the distribution of real-time GNSS data over IP networks such as the public Internet, focusing on two essential components of the system, data format and transport protocol. The provision of a suitable data format will allow users to take full advantage of the real-time GNSS data distribution system. Types of GNSS supported, message sizes, data rates, data precision levels, hardware and software support and possible future developments are investigated. An analysis is carried out on commonly known GNSS data formats, highlighting the most suitable standard for each evaluation criterion. A similar investigation is carried out on the transport protocols. An analysis is conducted on various design aspects of NTRIP and RT-IGS protocols, covering factors such as data latency, integrity, firewalls and proxy server compatibility and scalability. The analysis also covers the design aspects of the new draft Version 2 of NTRIP. The latter parts of this thesis report on the experiment results aimed at providing assessment of the current level of implementation of NTRIP. Data latency and integrity using NTRIP over the Internet are examined. Their impacts on users applications as the quality of real-time kinematic positioning is assessed. The results show that the performance of the system satisfies the rigorous requirement of the end-user application. The draft version of the new NTRIP indicates that UDP will be also supported. A similar investigation is carried out, providing the first experiment results on the new option. Tests using similar metrics, data latency and integrity, were carried out to verify the inherent differences between TCP and UDP. It was ascertained that, in most cases, UDP does offer improvement in terms of reduced latency over TCP. However this improvement is not significant enough to affect the performance of users applications tested. Compatibility tests were also carried out and the test results show that the new option experiences some compatibility issues with firewalls and wireless networks.

TCP (Transmission Control Protocol) and IP (Internet Protocol) are the most important protocols used for most of the data transmission across the Internet. Modern implementations of TCP mostly involve the concepts of Window Size and Round Trip Time (RTT) in controlling network congestion. We model simulated time series of Window Size and RTT to evaluate the characteristics and the relationship of the data over time using autoregressive moving average methods. These methods help us to forecast network performance and detect server congestion.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
PPP (Precise Point Positioning) is a positioning method by GNSS (Global Navigation Satellite Systems), based on SSR (State Space Representation) concept that can provide centimeter accuracy solutions. Real-time PPP (RT-PPP) is possible thanks to the availability of precise products, for orbits and clocks, provided by the International GNSS Service (IGS), as well as by its analysis centers such as CNES (Center National d'Etudes Spatiales). One of the remaining challenges on RT-PPP is the mitigation of atmospheric effects (troposphere and ionosphere) on GNSS signals. Thanks to recent improvements in atmospheric models, RT-PPP can be enhanced, allowing accuracy and centimeter initialization time, comparable to the current NRTK (Network Real-Time Kinematic) method. Such performance depends on topology of permanent stations networks and atmospheric conditions. The main objective of this project is to study the RT-PPP and the optimized infrastructure in terms of costs and benefits to realize the method using atmospheric corrections. Therefore, different configurations of a dense and regular GNSS network existing in France, the Orpheon network, are used. This network has about 160 sites and is owned by Geodata-Diffusion (Hexagon Geosystems). The work was divided into two main stages. Initially, ‘float PPP-RTK’ was evaluated, it corresponds to RT-PPP with improvements resulting from network corrections, although with ambiguities kept float. Further on, network corrections are applied to improve “PPP-RTK” where ambiguities are fixed to their integer values. For the float PPP-RTK, a modified version of the RTKLib 2.4.3 (beta) package is used to take into account for the network corrections. First-order ionospheric effects were eliminated by the iono-free combination and zenith tropospheric delay estimated. The corrections were applied by introducing a priori constrained tropospheric parameters. Periods with different tropospheric conditions were chosen to carry out the study. Adaptive modeling based on OFCs (Optimal Fitting Coefficients) has been developed to describe the behavior of the troposphere, using estimates of tropospheric delays for Orpheon stations. This solution allows one-way communication between the server and the user. The quality of tropospheric corrections is evaluated by comparison to external tropospheric products. The gains achieved in convergence time to 10 centimeters accuracy were statistically quantified. Network topology was assessed by reducing the number of reference stations (up to 75%) using a sparse Orpheon network configuration to perform tropospheric modeling. This did not degrade the tropospheric corrections and similar performances were obtained on the user side. In the second step, PPP-RTK is realized using the PPP-Wizard 1.3 software and CNES real-time products for orbits, clocks and phase biases of satellites. RT-IPPP (Real-Time Integer PPP) is performed with estimation of tropospheric and ionospheric delays. Ionospheric and tropospheric corrections are introduced as a priori parameters constrained to the PPP-RTK of the user. To generate ionospheric corrections, it was implemented a solution aligned with RTCM (Real-Time Maritime Services) conventions, regarding the transmission of ionospheric parameters SSR, which is a standard Inverse Distance Weighting (IDW) algorithm. The choice of the periods for this experiment was made mainly with respect to the ionospheric activity. The comparison of the atmospheric corrections with the external products and the evaluation of different network topologies (dense and sparse) were also carried out in this stage. Statistically, the standard RT-IPPP takes ~ 25 min to achieve a 10 cm horizontal accuracy, which is significantly improved by our method: 46% (convergence in 14 min) with dense network corrections and 24% (convergence in 19 min) with the sparse network. Nevertheless, vertical positioning sees its convergence time slightly increased, especially when corrections are used from a sparse network solution. However, improvements in horizontal positioning due to external SSR corrections from a (dense or sparse) network are promising and may be useful for applications that depend primarily on horizontal positioning.
O PPP (Precise Point Positioning) é um método de posicionamento pelo GNSS (Global Navigation Satellite Systems), baseado no conceito SSR (State Space Representation) o qual pode fornecer soluções de acurácia centimétrica. O PPP em tempo real (RT-PPP) é possível graças à disponibilidade de produtos precisos, para órbitas e relógios, fornecidos pelo IGS (International GNSS Service), bem como por seus centros de análise, como o CNES (Centre National d’Etudes Spatiales). Um dos desafios restantes no RT-PPP é a mitigação dos efeitos atmosféricos (troposfera e ionosfera) nos sinais GNSS. Graças às melhorias recentes nos modelos atmosféricos, o RT-PPP pode ser aprimorado, permitindo tempo de inicialização com acurácia centimétrica, comparável ao atual método NRTK (Network Real-Time Kinematic). Esse desempenho depende da topologia das redes de estações permanentes e das condições atmosféricas. O objetivo principal deste projeto é estudar o RT-PPP e a infraestrutura optimizada em termos de custos e benefícios para realizar o método usando correções atmosféricas. Portanto, são utilizadas diferentes configurações de uma rede GNSS densa e regular existente na França, a rede Orphéon. Esta rede tem cerca de 160 estações, sendo propriedade da Geodata-Diffusion (Hexagon Geosystems). O trabalho foi dividido em duas etapas principais. Inicialmente, foi avaliado o "float PPP-RTK", que corresponde ao RT-PPP com melhorias resultantes de correções de rede, embora mantendo as ambiguidades como float. Em um segundo momento, as correções de rede são aplicadas para aprimorar o "PPP-RTK", onde ambiguidades são fixadas para seus valores inteiros. Para o float PPP-RTK, uma versão modificada do software RTKLib 2.4.3 (beta) é empregada de modo a levar em consideração as correções de rede. Os efeitos ionosféricos de primeira ordem são eliminados pela combinação iono-free e atraso zenital troposférico é estimado. As correções são aplicadas introduzindo parâmetros troposféricos a priori injuncionados. Períodos com diferentes condições troposféricas foram escolhidos para realizar o estudo. Uma modelagem adaptativa baseada em OFCs (Optimal Fitting Coefficients) foi implementada para descrever o comportamento da troposfera, utilizando estimativas de atraso troposférico para estações da rede Orphéon. Tal solução permite a comunicação unidirecional entre o servidor e o usuário. A qualidade das correções troposféricas foi avaliada através de comparação com produtos externos troposféricos. Os ganhos alcançados no tempo de convergência para acurácia de 10 centímetros foram quantificados estatisticamente. A topologia de rede foi avaliada reduzindo o número de estações de referência (em até 75%) usando uma configuração da rede Orphéon esparsa para realizar a modelagem troposférica. Isso não degradou as correções troposféricas e foram obtidas performances similares para os usuários simulados. Na segunda etapa, o PPP-RTK é realizado usando o software PPP-Wizard 1.3, bem como os produtos para tempo real do CNES de órbitas, relógios e biases de fase dos satélites. O RT-IPPP (Real-Time Integer PPP) é realizado com estimativa de atrasos troposféricos e ionosféricos. As correções ionosféricas e troposféricas são introduzidas como parâmetros a priori injuncionados no PPP-RTK do usuário. Para gerar correções ionosféricas, foi implementada uma solução alinhada com as convenções RTCM (Real-Time Maritime Services), em relação à transmissão de correções ionosféricas SSR, o qual é um algoritmo baseado na ponderação pelo inverso da distância (IDW – Inverse Distance Weighting). A escolha dos períodos para este experimento foi realizada principalmente em relação à atividade ionosférica. A comparação das correções atmosféricas com produtos externos, assim como a avaliação de diferentes topologias de rede (densa e esparsa) também foram realizadas nesta etapa. Estatisticamente, o RT-IPPP padrão leva ~ 25 min para alcançar uma acurácia horizontal de 10 cm, a qual é significativamente melhorada pelo método implementado: 46% (convergência em 14 min) com correções de rede densa e 24% (convergência em 19 min) com a rede esparsa. No entanto, o posicionamento vertical vê o seu tempo de convergência ligeiramente aumentado, especialmente quando as correções são usadas a partir de uma solução de rede esparsa. No entanto, as melhorias no posicionamento horizontal com o uso das correções de SSR externas de uma rede (densa ou esparsa) são promissoras e podem ser úteis para aplicações que dependem principalmente do posicionamento horizontal.
Le PPP (Precise Point Positioning) est une méthode de positionnement par GNSS (Global Navigation Satellite Systems), basée sur le concept SSR (State Space Representation), qui peut générer solutions de précision centimétrique. Le PPP en temps réel (RT-PPP) est possible grâce à la disponibilité des produits précis, pour les orbites et horloges, fournis par l’IGS (International GNSS Service), ainsi que par ses centres d'analyse, tels que le CNES (Centre National d'Etudes Spatiales). Un des défis restants sur le RT-PPP est la mitigation des effets atmosphériques (troposphère et ionosphère) sur les signaux GNSS. Grâce aux améliorations récentes des modèles atmosphériques, le RT-PPP peut être amélioré, ce qui permet une précision et un temps d'initialisation au niveau du centimètre, comparables à la méthode NRTK (Network Real-Time Kinematic) actuelle. De telles performances dépendent de la topologie du réseau de stations GNSS permanentes et des conditions atmosphériques. L'objectif principal de ce projet est d'étudier le RT-PPP et l'infrastructure optimisée en termes de coûts et d'avantages pour réaliser la méthode en utilisant des corrections atmosphériques. Pour cela, différentes configurations d'un réseau GNSS dense et régulier existant en France, le réseau Orphéon, sont utilisées. Ce réseau compte environ 160 sites, propriété de Geodata-Diffusion (Hexagon Geosystems). Le travail est divisé en deux étapes principales. Dans un premier temps, le mode «PPP-RTK flottant» a été évalué, il correspond au RT-PPP avec des améliorations issues des corrections de réseau, mais avec les ambiguïtés flottantes. Ensuite, des corrections de réseau sont appliquées pour améliorer le mode « PPP-RTK » où les ambiguïtés sont fixées à leurs valeurs entières. Pour le PPP-RTK flottant, une version modifiée du package RTKLib 2.4.3 (beta) est utilisée pour prendre en compte les corrections réseau. Les effets ionosphériques de premier ordre ont été éliminés par la combinaison iono-free et le retard troposphérique zénithal est estimé. Les corrections ont été appliquées en introduisant des paramètres troposphériques a priori contraints. Des périodes avec différentes conditions troposphériques ont été choisies pour réaliser l'étude. Une modélisation adaptative basée sur les OFCs (Optimal Fitting Coefficients) a été mise en place pour décrire le comportement de la troposphère, en utilisant des estimations des retards troposphériques pour les stations Orphéon. Cette solution permet une communication mono-directionnelle entre le serveur et l'utilisateur. La qualité des corrections troposphériques est évaluée par comparaison avec des produits troposphériques externes. Les gains réalisés sur le temps de convergence pour obtenir un positionnement de 10 centimètres de précision ont été quantifiés statistiquement. La topologie du réseau a été évaluée, en réduisant le nombre de stations de référence (jusqu'à 75%), via une configuration de réseau Orphéon lâche pour effectuer la modélisation troposphérique. Cela n'a pas dégradé les corrections troposphériques et des performances similaires ont été obtenues du côté de l'utilisateur. Dans la deuxième étape, le PPP-RTK est réalisé grâce au logiciel PPP-Wizard 1.3 et avec les produits temps réel CNES pour les orbites, les horloges et les biais de phase des satellites. Le RT-IPPP (Real-Time Integer PPP) est réalisé avec estimation des délais troposphériques et ionosphériques. Les corrections ionosphériques et troposphériques sont introduites en tant que paramètres a priori contraints au PPP-RTK de l'utilisateur. Pour générer des corrections ionosphériques, il a été mis en place une solution alignée avec les conventions RTCM (Real-Time Maritime Services) pour la transmission des paramètres ionosphériques SSR, un algorithme standard d'interpolation à distance inversée (IDW – Inverse Distance Weighting). Le choix des périodes pour cette expérience a été fait principalement en regard de l'activité ionosphérique. La comparaison des corrections atmosphériques avec les produits externes et l'évaluation de différentes topologies de réseau (dense et lâche) ont également été effectuées dans cette étape. Statistiquement le RT-IPPP standard prend ~25 min pour atteindre une précision horizontale de 10 cm, ce que nous améliorons significativement par notre méthode : 46% (convergence en 14 min) avec le réseau dense et 24% (convergence en 19 min) avec le réseau restreint. Néanmoins le positionnement vertical voit son temps de convergence légèrement augmenté, en particulier lorsque l'on utilise des corrections à partir d'une solution de réseau lâche. Cependant, les améliorations apportées au positionnement horizontal dues aux corrections atmosphériques SSR externes provenant d’un réseau (dense ou lâche) sont prometteuses et peuvent être utiles pour les applications qui dépendent principalement du positionnement horizontal.
CNPq: 229828/2013-2

Formal Description Techniques allow for the use of automated tools during the specification and development of communication protocols. Estelle is a standardized formal description technique developed by ISO to remove ambiguities in the specification of communication protocols and services. The UBC Estelle-C compiler automates the implementation of protocols by producing an executable C implementation directly from its Estelle specification. In this thesis, we investigate the automated protocol implementation methodology using the Estelle-C compiler. First, we describe the improvements made to the compiler to support the latest version of Estelle. Then, we present and discuss the semiautomated implementations of the LAPB protocol in the CCITT X.25 Recommendation and the RTS protocol in the CCITT X.400 MHS series using this compiler. Finally, we compare the automatic and manual protocol implementations of LAPB and RTS protocols in terms of functional coverage, development time, code size, and performance measure. The results strongly indicate the overall advantages of automatic protocol implementation method over the manual approach.
Science, Faculty of
Computer Science, Department of
Graduate

The speed and accuracy of conservation planning could be improved if maps indicating areas where grassed waterways should be placed to reduce erosion could be easily created. For five central Kentucky fields, elevation data were obtained with real time kinematic (RTK) global positioning system (GPS) and from US Geological Survey (USGS) digital elevation models (DEMs). Terrain attributes were calculated from these datasets which were used as predictor variables for neural network and logistic regression analyses. Grassed waterway prediction models were developed with these analyses. The type of activation function, type of standardization procedure, number of neurons, number of preliminary runs, and number of hidden layers had little impact on the results of the neural network analysis. Logistic regression and neural network analyses produced similar erosion prediction maps. The type of flow direction algorithm used to calculate terrain attributes did not change prediction maps substantially. Grassed waterways could be predicted in most cases with the RTK data but only in some cases with the USGS data. This modeling approach was robust and could aid conservation planners in identifying suitable areas for waterways more efficiently if accurate elevation data can be acquired.

This report presents several different techniques for diverting RTP streams when using a handheld mobile device. This device is running a version of Minisip as the SIP user agent. An introduction to the SIP protocol is given to provide some background to the reader prior to focusing upon the main goal: redirecting RTP streams. A set of requirements are defined and an RTP media transfer mode is chosen based upon these requirements. The requirements are derived from a study of a Linux cellular phone’s mobile device features and capabilities. Minisip was ported to this platform and a series of tests conducted to evaluate the design decisions made. These tests show that the best method of redirecting RTP media streams is third party call control (3PCC).
Den här rapporten presenterar flera olika teknikerna för att dra RTP strömar när man använder en mobil anordning. Den här anordningen löper en version av Minisip som den SIP användare agent. En introduktion till SIP protokoll är gjord för att ge läsaren någon bakgrund på focusen ovanför det huvudsakliga målet : omdirigerande de RTP strömarna. En set av bestämd behov är definierad och en RTP media transfer sätt är vald på grund av de här behoven. Behoven är härrörda från en studie över en Linux mobiltelefon. Minisip var installerad till den här plattformen och en serie av test dirigerad för att utvärdera de gjorda designsbesluten. De här testen visar den bästa metoden för att omdirigera RTP media strömar är den tredje part kalla kontrollen (3PCC).

From its very beginnings, regional science has been open to intellectual exchange with many other scientific disciplines. This has led to cross-fertilization, but also to problems concerning the intellectual identity of regional science. After half a century of history of the field, it is time to ask the question, whether or not regional science has developed into a scientific discipline in these decades. In this paper we use cross-citation data between 464 journals in different disciplines to answer this question. With this data set we attempt to find out, how strongly regional science journals are interconnected by citations as compared to their citation links to journals in neighbouring disciplines. We find that when we consider the raw citation data, regional science becomes fragmented with its journals tied to those from economics, geography, planning, etc. When we standardize the citation information to take into account size differences between journals, however, regional science appears to form a strong and well connected dscientific discipline.
Series: SRE - Discussion Papers

Thesis (Ph.D.)--Case Western Reserve University, 2009
Title from PDF (viewed on 19 August 2009) Department of Electrical Engineering and Computer Science Includes abstract Includes bibliographical references Available online via the OhioLINK ETD Center

University of Central Florida College of Engineering Thesis
Psychological testing has shown that there is an early preattentive stage in the human visual system. At this level, simple features and properties of objects known as visual primitives are deteched spatially in parallel by groupings of cells in the visual cortex known as feature maps. In order to study this preattentive stage in a machine vision system, the biologically inspired, highly parallel architecture of the artificial neural network shows great promise. This paper describes how the unique architecture of the counterpropagation neural network was used to simulate the feature maps which detect visual primitives in the human visual system. The results of the research showed that artificial neural networks are able to reproduce the function of the feature maps with accuracy. The counterpropagation network was able to reproduce the feature maps as theorized, however, future research might investigate the abilities of other neural network algorithms in this area. Development of a method for combining the results of feature maps in a simulation of full scale early vision is also a topic for future research that would benefit from the results reported here.
M.S.;
Computer Engineering
Engineering;
Computer Engineering
63 p.
iv, 63 leaves, bound : ill. ; 28 cm.

Wireless local area networks WLAN and Voice over IP technologies enable local low cost wireless telephony, while cellular networks offer wide-area coverage. The use of dual mode WLAN-cellular terminals should allow cost savings by automatically switching from GSM to WLAN networks whenever it is feasible. However, in order to allow user mobility during a call, a handover procedure for transferring a call between the WLAN interface and the cellular network should be defined. The decision algorithm that triggers such a handover is critical to maintain voice quality and uninterrupted communication. Information or measurements collected from the network may be used to anticipate when the connection will degrade to such a point that a handover is desirable in order to allow a sufficient time span for the handover’s successful execution. It is the delay in detecting when to make a handover and the time to execute it that motivates the need for a prediction. The goal of this thesis is therefore to present a method to predict when a handover should be made based upon network conditions. We selected a number of WLAN and VoIP software tools and adapted them to perform the measurements. These tools allowed us to measure parameters of the WLAN’s physical and link layers. Packet losses and jitter measurements were used as well. We have assumed that there is ubiquitous cellular coverage so that we only have to be concerned with upward handovers (i.e, from the WLAN to the cellular network and not the reverse). Finally we have designed and evaluated a mechanism that triggers the handover based in these measurements.
WLAN, trådlöst lokalt nätverk, och IP-telefoni tillsammans gör det möjligt med billig trådlös telefoni, samtidigt som mobiltelefoninätverk erbjuder stor signal beläggning. Att använda WLAN-mobil med dubbla hårdvaruterminaler skulle ge en kostnadsreducering genom att automatisk byta från GSM till WLAN när det är möjligt. Emellertid för att kunna flytta pågående samtal mellan ett WLAN- och ett mobilt gränssnitt, måste en handovermekansim definieras. En beslutsalgoritm som utlöser sådan handover är av stor vikt för att bibehålla röstkvalitet och oavbruten kommunikation. För att tillåta ett tillräckligt tidsspann för handoverns utförande kan information tagen från nätverket användas för att förutse när kommunikationen ska degraderas till en sådan punkt att en handover är önskvärd. Förseningen i detekteringen när en handover ska ske och tiden för utförandet motiverar behovet av förutsägelse. Det här exjobbet introducerar en metod som förutsäger när handover ska börja baserade på nätverksförhållandena. Vi har valt några WLAN och VoIP-program och anpassat dem för att genomföra mätningarna. Programmen tillät oss att mäta WLANs parameter för fysiska och datalänksskikten. Pecket Loss och jitter-mätningar användes likaså. Vi antog att det fanns GSM tjänst på alla platser så att vi endast behövde göra uppg aende handover(t.ex. från WLAN till mobilt nätverk och inte tvärtom). Vi framkallade och testade en mekanism att starta handovern baserade på nätverksmätningarna.
This is the same Ian Marsh as advisor who authored the disseratation http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10572

University of Central Florida College of Engineering Thesis
This dissertation studied cognitive packet networks (CPN) which build networked learning systems that support adaptive, quality of service-driven routing of packets in wired networks and in wireless, mobile ad hoc networks.
Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering and Computer Science
160 p.
xvii, 160 leaves, bound : ill. ; 28 cm.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Ever since Henry Chesbrough coined the term in 2003, the number of studies exploring the new paradigm of open innovation (OI) has grown exponentially, with researchers investigating and exploring the application of open principles in an array of industrial and geographical contexts. Despite this growing interest from the scientific community as well as practitioners, our understanding of the implementation of open principles from an SME perspective remains, to a large extent, underdeveloped. In particular, uncovering how the SME can best exploit and manage their external network to facilitate both exploration and exploitation activities has, thus far, been largely neglected. Therefore, an exploration of the implementation and successful management of OI projects in smaller firms from a network perspective, through a systematic review and assimilation of the current body of extant studies seems a timely and necessary step, in order to form a roadmap for a future research agenda. Consequently, the aim of this paper is to shed light on the antecedents and outcomes of successful OI network management in small firms. Systematic analysis of 51 extant studies reveals that many barriers associated with implementing OI in SMEs often referred to as liability of smallness, can be overcome by the effective network management, coupled with the implementation of an open culture. Openness can also be seen to be positively related to business model flexibility and adaptability. Results though, remain unclear on the exact role of the intermediary and whether entrepreneurial capacity, trust, increased social interaction and goal alignment among the SME and their network partners, as well as network unity and conflict mitigation/resolution can be described as a driver for, or an outcome of successful open projects. Therefore, these potential relationships between openness and managerial capacity are proposed for further empirical testing and analysis. The paper concludes by presenting a map for future research, incorporating a series of propositions suggested during the analysis and consolidating these issues into a framework of suggestions for future research.
Series: Working Papers / Institut für KMU-Management

The need for security is crucial in Telephony over IP (ToIP). Secure protocols have been designed as well as specific devices to fulfill that need. This master thesis examines one of such devices called Session Border Controller (SBC), which can be compared to reverse proxies for ToIP. The idea is to apply message filters to increase security. This thesis presents the reasons of SBC existence, based on the security weaknesse sa ToIP network can show. These reasons are then used to establish a list of features which can be expected from a SBC and discuss its ideal placement in a ToIP network architecture. A test methodology for SBCs is established and used on the free software Kamailio as an illustration. Following this test, improvements of this software, regarding threats prevention and attacks detection, are presented and implemented.
Behovet av säkerhet är av avgörande betydelse i telefoni över IP (ToIP). Säkerhetsprotokoll har utformats samt särskilda enheter för att uppfylla detta behov. Detta examensarbete undersöker en av sådana enheter som kallas Session Border Controller (SBC), vilket kan jämföras med omvända proxyservrar för ToIP. Tanken är att tillämpa meddelandefilter för att öka säkerheten. Denna avhandling presenterar orsakerna till SBC existens, baserat på de säkerhets svagheter en ToIP nätverk kan visa. Dessa skäl används sedan för att upprätta en förteckning över egenskaper som kan förväntas av en SBC och diskutera dess ideal placering i en ToIP nätverksarkitektur . En testmetodik för SBC är etablerad och används på fri programvara Kamailio som en illustration. Efter detta test, förbättringar av denna programvara, om hot förebyggande och attacker upptäcka, presenteras och genomförs.

Receptor-like kinases (RLKs) make up one of the largest gene families in Arabidopsis thaliana. These genes are required for various biological processes, including response to biotic stress, cell elongation, cell proliferation, and cell fate patterning. An emerging theme in Arabidopsis and other plants is that networks of RLKs are required to regulate a specific process throughout development involving spatial and temporal regulation of transcription factors. However, there are still many RLKs (>50%) with no known function.Several RLKs regulate epidermal development by contributing to early embryonic epidermal maintenance or to epidermal differentiation. In my first analysis, I characterize the role of two related RLKs GASSHO1 (GSO1) and GSO2 in epidermal differentiation. gso1 gso2 double mutants initially form an epidermis during embryogenesis, but analysis of post-embryonic root development indicates the mis-expression of epidermal-specific genes. Three previously characterized RLKs that are involved in epidermal development are also involved in meristem maintenance. In order to decipher the RLK gene networks controlling epidermal development and meristem maintenance, it is necessary to identify additional RLKs involved in both of these processes. I further identified roles for GSO1 and GSO2 in maintaining root growth and root apical meristem (RAM) activity. A future goal will be to elucidate the networks of RLKs, including GSO1 and GSO2 in regulating epidermal and RAM development.The development of the vasculature in plants is controlled by a vascular meristem, the procambium. Oriented cell divisions from the procambium produce phloem, to the periphery, and xylem, to the center of the plant. In a reverse genetic screen to determine to roles of the remaining RLKs with unknown function, we identified the RLK XYLEM INTERMIXED WITH PHLOEM1 (XIP1) that is required for vascular development. We show XIP1 is required for regulating the differentiation of the phloem and for the organization of xylem vessel elements. Our analysis indicates that XIP1 is part of a vascular meristem network, further emphasizing the importance of social networks of RLKs regulating a specific process in development.

The rapid growth of the Internet and the proliferation of its new applications pose a serious challenge in network performance management and monitoring. The current Internet has no mechanism for providing feedback on network congestion to the end-systems at the IP layer. For applications and their end hosts, end-to-end measurements may be the only way of measuring network performance. Understanding the packet delay and loss behavior of the Internet is important for proper design of network algorithms such as routing and flow control algorithms, for the dimensioning of buffers and link capacity, and for choosing parameters in simulation and analytic studies. In this thesis, round trip time (RTT), one-way network delay and packet loss in the Internet are measured at different times of the day, using a Voice over IP (VoIP) device. The effect of clock skew on one-way network delay measurements is eliminated by a Linear Programming algorithm, implemented in MATLAB. Distributions of one-way network delay and RTT in the Internet are determined. It is observed that delay distribution has a gamma-like shape with heavy tail. It is tried to model delay distribution with gamma, lognormal and Weibull distributions. It is observed that most of the packet losses in the Internet are single packet losses. The effect of firewall on delay measurements is also observed.

Examensarbetet bakom denna rapport utgör en undersökande studie om hur transmission av mediadata i nätverk kan göras effektivare. Det kan åstadkommas genom att viss tilläggsinformation avsedd för att jämna ut datatakten adderas i det realtidsprotokoll, Real Time Protocol, som används för strömmande media. Genom att försöka skicka lika mycket data under alla konsekutiva tidsintervall i sessionen kommer datatakten vid en godtycklig tidpunkt med större sannolikhet att vara densamma som vid tidigare klockslag. En streamingserver kan tolka, hantera och skicka data vidare enligt instruktionerna i protokollets sidhuvud. Datatakten jämnas ut genom att i förtid, under tidsintervall som innehåller mindre data, skicka även senare data i strömmen. Resultatet av detta är en utjämnad datataktskurva som i sin tur leder till en jämnare användning av nätverkskapaciteten.

Arbetet inkluderar en översiktlig analys av beteendet hos strömmande media, bakgrundsteori om filkonstruktion och nätverksteknologier samt ett förslag på hur mediafiler kan modifieras för att uppfylla syftet med examensarbetet. Resultat och diskussion kan förhoppningsvis användas som underlag för en framtida implementation av en applikation ämnad att förbättra trafikflöden över nätverk.

The success of the Internet has brought significant changes to the telecommunication industry. One of the remarkable outcomes of this evolution is Voice over IP (VoIP), which enables realtime voice communications over packet switched networks for a lower cost than traditional public switched telephone networks (PSTN). Nevertheless, security and privacy vulnerabilities pose a significant challenge to hindering VoIP from being widely deployed. The main object of this thesis is to define and elaborate unexplored security and privacy risks on standardized VoIP protocols and their implementations as well as to develop suitable countermeasures. Three research questions are addressed to achieve this objective: Question 1:  What are potential unexplored threats in a SIP VoIP network with regard to availability, confidentiality and privacy by means of unwanted traffic and information disclosure? Question 2:  How far are existing security and privacy mechanisms sufficient to counteract these threats and what are their shortcomings? Question 3:  How can new countermeasures be designed for minimizing or preventing the consequences caused by these threats efficiently in practice? Part I of the thesis concentrates on the threats caused by "unwanted traffic", which includes Denial of Service (DoS) attacks and voice spam. They generate unwanted traffic to consume the resources and annoy users. Part II of this thesis explores unauthorized information disclosure in VoIP traffic. Confidential user data such as calling records, identity information, PIN code and data revealing a user's social networks might be disclosed or partially disclosed from VoIP traffic. We studied both threats and countermeasures by conducting experiments or using theoretical assessment. Part II also presents a survey research related to threats and countermeasures for anonymous VoIP communication.

University of Central Florida College of Engineering Thesis
A simulation based decision support system is developed for AT&T Microelectronics in Orlando. This sytem uses simulation modeling to capture the complex nature of semiconductor test operations. Simulation, however, is not a tool for optimizations by itself. Numerous executions of the simulation model must generally be performed to narrow in on a set of proper decision parameters. As a means of alleviating this shortcoming, artificial neural networks are used in conjunction with simulation modeling to aid management in the decision making process. The integration of simulation and neural networks in a comprehensive decision support system, in effect, learns the reverse of the simulation porocess. That is, given a set of goals defined for performance measures, the decision support sytem suggests proper values for decision parameters to achieve those goals.
M.S.;
Industrial Engineering and Mangement Systems
Engineering;
Industrial Engineering
165 p.
viii, 165 leaves, bound : ill. ; 28 cm.

Em um reator nuclear PWR a temperatura do refrigerante do circuito primário e a da água de realimentação são medidas usando RTD (Resistance Temperature Detectors), ou termômetros de resistência. Estes RTDs alimentam os sistemas de controle e segurança da usina e devem, portanto, ser muito precisos e ter bom desempenho dinâmico. O tempo de resposta dos RTDs é caracterizado por um parâmetro denominado de Constante de Tempo, definido como sendo o tempo que o sensor leva para atingir 63,2% do seu valor final após sofrer uma variação de temperatura em forma de degrau. Este valor é determinado em laboratório, porém as condições de operação de reatores nucleares são difíceis de ser reproduzidas. O método LCSR (Loop Current Step Response), ou teste de resposta a um degrau de corrente, foi desenvolvido para medir remotamente o tempo de resposta dos RTDs. A partir desse teste, a constante de tempo do sensor é calculada através de uma transformação LCSR que envolve a determinação das constantes modais do modelo de transferência de calor. Este cálculo não é simples e requer pessoal especializado. Por este motivo, utilizou-se a metodologia de Redes Neurais Artificiais para estimar a constante de tempo do RTD a partir do LCSR. Os testes LCSR foram usados como dados de entrada da RNA; os testes de Imersão Rápida foram usados para determinar a constante de tempo dos sensores, sendo estes os valores desejados de saída da rede. Esta metodologia foi aplicada inicialmente a dados teóricos, simulando dez sensores com diferentes valores de constante de tempo, resultando em um erro médio de aproximadamente 0,74 %. Dados experimentais de 3 diferentes RTDs foram usados para estimar a constante de tempo, resultando em um erro máximo de 3,34 %. Os valores de constante de tempo estimados pelas RNAs foram comparados com aqueles obtidos pelo método tradicional, obtendo-se um erro médio de 18 % o que mostra que as RNAs são capazes de estimar a constante de tempo de uma forma precisa.
In a PWR nuclear power plant, the primary coolant temperature and feedwater temperature are measured using RTDs (Resistance Temperature Detectors). These RTDs typically feed the plants control and safety systems and must, therefore, be very accurate and have good dynamic performance. The response time of RTDs is characterized by a single parameter called the Plunge Time Constant defined as the time it takes the sensor output to achieve 63.2 percent of its final value after a step change in temperature. Nuclear reactor service conditions are difficult to reproduce in the laboratory, and an in-situ test method called LCSR (Loop Current Step Response) test was developed to measure remotely the response time of RTDs. From this test, the time constant of the sensor is identified by means of the LCSR transformation that involves the dynamic response modal time constants determination using a nodal heat-transfer model. This calculation is not simple and requires specialized personnel. For this reason an Artificial Neural Network has been developed to predict the time constant of RTD from LCSR test transient. It eliminates the transformations involved in the LCSR application. A series of LCSR tests on RTDs generates the response transients of the sensors, the input data of the networks. Plunge tests are used to determine the time constants of the RTDs, the desired output of the ANN, trained using these sets of input/output data. This methodology was firstly applied to theoretical data simulating 10 RTDs with different time constant values, resulting in an average error of about 0.74 %. Experimental data from three different RTDs was used to predict time constant resulting in a maximum error of 3,34 %. The time constants values predicted from ANN were compared with those obtained from traditional way resulting in an average error of about 18 % and that shows the network is able to predict accurately the sensor time constant.

This paper looks at the effects of different forms of wholesale and retail regulation on retail competition in fixed network telephony markets. We explicitly model two asymmetries between the incumbent operator and two entrants: (i) While the incumbent has zero marginal costs, the entrant has the wholesale access charge as (positive) marginal costs; (ii) While the incumbent is setting a two-part tariff at the retail level (fixed fee and calls price), the entrant can only set a linear price for calls. We model the product of the incumbent as horizontally differentiated from the products of the entrants who are homogenous and do not have any market power. Competition from other infrastructures such as mobile telephony or cable is modelled as an "outside opportunity" for consumers. We find that entrants without market power might be subject to a margin squeeze if the wholesale access price is set at average costs and competitive pressure from other infrastructures increases. Product differentiation, however, prevents market foreclosure. We argue that a wholesale price regulation at average costs is not optimal in such a situation and discuss retail-minus and deregulation as potential alternatives. (author's abstract)
Series: Working Papers / Research Institute for Regulatory Economics

The interest for various multimedia services accessed via the Internet has been growing immensely along with the bandwidth available. A similar development has emerged in the 3G mobile network. The focus of this master thesis is on the speech/audio part of a 3G multimedia application. The purpose has been to implement a traffic generating tool that can measure QoS (Quality of Service) in 3G networks. The application is compliant to the 3G standards, i.e. it uses AMR (Adaptive Multi Rate), SIP (Session Initiation Protocol) and RTP (Real Time Transport Protocol). AMR is a speech compression algorithm with the special feature that it can compress speech into several different bitrates. SIP signalling is used so that different applications can agree on how to communicate. RTP carries the speech frames over the network, in order to provide features that are necessary for media/multimedia applications. Issues like perception of audio and QoS related parameters is also discussed, from the perspective of users and developers.