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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Approches tensorielles pour les systèmes de communication MIMO avec relais / Tensor-based MIMO relaying communication systems

Ronchini Ximenes, Leandro 25 March 2015 (has links)
Dans les communications coopératives, deux ou plusieurs terminaux de transmissionsont combinés pour accroître la diversité et/ou la puissance des signaux arrivant à un récepteur. Récemment, l'analyse tensorielle s'est avérée une approche efficace pour l'estimation de canaux dans les systèmes coopératifs. Cependant, parmi les quelques travaux consacrés à cette tâche, l'utilisation de la décomposition tensorielle PARAFAC pour modéliser les signaux reçus ne permet pas l'estimation conjointe des symboles et des canaux de communication. Afin d'éviter l'utilisation de séquences de symboles pilotes, l'objectif de cette thèse est de fournir de nouvelles approches tensorielles, en termes de systèmes de transmission et de récepteurs semi-aveugles, pour des systèmes de communication MIMO avec relai mono-directionnels, à deux sauts. Deux systèmes de transmission sont proposés en utilisant un codage spatio-temporel du type Khatri-Rao et deux stratégies de traitement Amplify-and-Forward (AF) au relai. Pour ces systèmes, appelés PT2-AF et NP-AF, les signaux reçus au niveau de la destination satisfont respectivement des modèles tensoriels du type PARATUCK2 et nested PARAFAC. En exploitant les propriétés d'unicité de ces modèles tensoriels établies dans la thèse, plusieurs récepteurs semi-aveugles sont dérivés. Certains de ces récepteurs sont du type ALS, tandis que d'autres sont des solutions non itératives basées sur des factorisations de produits de Khatri-Rao. Des résultats de simulation sont présentés pour illustrer les performances des récepteurs proposés qui sont comparés à des estimateurs supervisés. / In cooperative communication systems, two or more transmitting terminals arecombined to increase the diversity and/or the power of the signals arriving at aparticular receiver. Recently, the so-called tensor analysis has been an efficient approach for channel estimation in systems with cooperative diversity. However, among the few works devoted to this task, the utilization of the PARAFAC tensor decomposition for modeling the received signals did not allow the development of techniques for joint symbol and channel estimation. Aiming to avoid the use of pilot-based sequences, the objective of this thesis is to provide new tensor-based strategies, including transmission systems and semi-blind receivers, for one-way two-hop relaying systems. Based on a Khatri-Rao space-time coding at the source and two different Amplify-and-Forward (AF) relaying strategies, two transmission systems are proposed. For these systems, named PT2-AF and NP-AF, the received signals at the destination node follow respectively a PARATUCK2 and a nested PARAFAC tensor model. Exploiting uniqueness properties of these tensor models which are established in the thesis, several semi-blind receivers are derived. Some of these receivers are of iterative form using an ALS algorithm, whereas some other ones are close-form solutions associated with Khatri-Rao factorizations. Some simulation results are finally presented to illustrate the performance of the proposed receivers which are compared to some state-of-the-art supervised techniques.
232

Conception et réalisation, par fabrication additive, de matériaux cellulaires architecturés / Design and realization, by additive manufacturing, of architectural cellular materials

Heisel, Cyprien 16 May 2019 (has links)
La démarche « matériaux numériques », développée au CEA Le Ripaut, consiste à optimiser numériquement une structure, à l’aide de codes de calcul permettant de réaliser des expériences numériques, afin de répondre le plus précisément possible à un cahier des charges. La mise en œuvre de ces structures optimisées, aux formes pouvant être complexes, n’est parfois pas réalisable avec les procédés de fabrication actuels. Cependant, la progression rapide de l’impression 3D semble maintenant pouvoir concrétiser cette démarche. Le but de cette thèse est d’étudier cette faisabilité de fabrication, à travers une application concrète : l’optimisation des récepteurs volumétriques des Centrales Solaires Thermodynamiques (CST).Actuellement, la conception de ces récepteurs en Carbure de Silicium (SiC) est restreinte par les techniques existantes de fabrication, et leurs morphologies se limitent donc principalement à des mousses ou des canaux parallèles. Or, ce type de structure ne permet pas d’exploiter tout le caractère 3D proposé par les récepteurs, en raison notamment d’une absorption trop hétérogène du rayonnement solaire dans le volume. Dans ce travail de thèse, afin de rechercher la répartition de l’absorption la plus homogène possible dans l’ensemble du volume, de nombreuses structures aux formes variées sont générées virtuellement. Une simulation de l’éclairement solaire reçu est réalisée sur l’ensemble de ces structures, grâce à un code de calcul développé spécialement pour cette application, permettant ainsi d’en retenir trois répondants au mieux aux critères du cahier des charges. Ces structures potentiellement optimisées ont ensuite été fabriquées en SiC par impression 3D, par un procédé de projection de liant sur lit de poudre. Elles ont été ensuite testées sur un banc d’essai expérimental du laboratoire PROMES, reproduisant les conditions d’une CST. Les résultats ont montrés que ces structures, aux formes totalement différentes de mousses ou de canaux parallèles, sont capables de produire au maximum de l’air à 860°C en sortie de récepteur, et avec des rendements énergétiques proches de 0,65. Enfin, un code de calcul thermique couplé conducto-radiatif, amélioré durant ce travail, a permis d’analyser ces résultats expérimentaux et servira pour les futurs travaux d’optimisation de la géométrie d’un récepteur. / The "numerical materials" approach, developed at CEA Le Ripaut, consists to numerically optimize a structure, by using calculation codes that allow to realize numerical experiments, in order to answer, as precisely as possible, to a set of specifications. The manufacturing of these optimized structures, whose shapes can be complex, is sometimes not feasible with current manufacturing processes. However, the rapid progress of 3D printing now seems to be able to concretize this approach. The aim of this thesis is to study this manufacturing feasibility, through a concrete application: the optimization of the volumetric receivers of Concentrated Solar Power Plants (CSP). Currently, the design of these silicon carbide (SiC) receptors is restricted by the existing manufacturing techniques, and their morphologies are therefore mainly limited to foams or parallel channels. However, this type of structure does not allow to exploit all the 3D character proposed by the receivers, due in particular to a heterogeneous absorption of solar radiation in the volume. In this work, in order to find the distribution of the most homogeneous absorption possible in the whole volume, many structures with various shapes are generated virtually. A simulation of the solar irradiance received is carried out on all these structures, thanks to a calculation code developed especially for this application, thus allowing to choose three of them, respondents at best to the criteria of the specifications. These potentially optimized structures were then manufactured in SiC by 3D printing, by a binder jetting process. They were then tested on an experimental test bench of the PROMES laboratory, reproducing the conditions of a CSP. Results showed that these structures, where their shapes are totally different from foams or parallel channels, are able to produce a maximum air temperature of 860°C at the output of the receiver, and with efficiencies close to 0.65. Finally, a conducto-radiative coupled thermal computational code, improved during this work, made it possible to analyze these experimental results and will be used for the future work of optimization of the geometry of a receiver.
233

Millimeter-Wave Super-Regenerative Receivers for Wireless Communication and Radar

Ghaleb, Hatem 29 November 2022 (has links)
Today’s world is becoming increasingly automated and interconnected with billions of smart devices coming online, leading to a steep rise in energy consumption from small microelectronics. This coincides with an urgent push to transform global energy production to green energies, causing disruptions and energy shortages, and making the case for efficient energy use ever more pressing. Two major areas where high growth is expected are the fields of wireless communication and radar sensors. Millimeter-wave frequency bands are planned for fifth-generation (5G) and sixth-generation (6G) cellular communication standards, as well as automotive frequency-modulated continuous wave (FMCW) radar systems for driving assistance and automation. Fast silicon-based technologies enable these advances by operating at high maximum frequencies, such as the silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technologies. However, even the fastest transistors suffer from low and energy expensive gains at millimeter-wave frequencies. Rather than incremental improvements in circuit efficiency using conventional approaches, a disruptive revolution for green microelectronics could be enabled by exploring the low-power benefits of the super-regenerative receiver for some applications. The super-regenerative receiver uses a regenerative oscillator circuit to increase the gain by positive feedback, through coupling energy from the output back into the input. Careful bias and control of the circuit enables a very large gain from a small number of transistors and a very low energy dissipation. Thus, the super-regenerative oscillator could be used to replace amplifier circuits in high data rate wireless communication systems, or as active reflectors to increase the range of FMCW radar systems, greatly reducing the power consumption. The work in this thesis presents fundamental scientific research into the topic of energy-efficient millimeter-wave super-regenerative receivers for use in civilian wireless communication and radar applications. This research work covers the theory, analysis, and simulations, all the way up to the proof of concept, hardware realization, and experimental characterization. Analysis and modeling of regenerative oscillator circuits is presented and used to improve the understanding of the circuit operation, as well as design goals according to the specific application needs. Integrated circuits are investigated and characterized as a proof of concept for a high data rate wireless communication system operating between 140–220 GHz, and an automotive radar system operating at 60 GHz. Amplitude and phase regeneration capabilities for complex modulation are investigated, and principles for spectrum characterization are derived. The circuits are designed and fabricated in a 130 nm SiGe HBT technology, combining bipolar and complementary metal-oxide semiconductor (BiCMOS) transistors. To prove the feasibility of the research concepts, the work achieves a wireless communication link at 16 Gbit/s over 20 cm distance with quadrature amplitude modulation (QAM), which is a world record for the highest data rate ever reported in super-regenerative circuits. This was powered by a super-regenerative oscillator circuit operating at 180 GHz and providing 58 dB of gain. Energy efficiency is also considerably high, drawing 8.8 mW of dc power consumption, which corresponds to a highly efficient 0.6 pJ/bit. Packaging and module integration innovations were implemented for the system experiments, and additional broadband circuits were investigated to generate custom quench waveforms to further enhance the data rate. For radar active reflectors, a regenerative gain of 80 dB is achieved at 60 GHz from a single circuit, which is the best in its frequency range, despite a low dc power consumption of 25 mW.
234

Measured and Modeled Time and Angle Dispersion Characteristics of the 1.8 GHz Peer-to-Peer Radio Channel

Patwari, Neal 08 May 1999 (has links)
In an extensive outdoor propagation study, low antenna heights of 1.7 m are used at both the transmitter and the receiver to measure over 3500 wideband power-delay profiles (PDPs) of the channel for a peer-to-peer communications system. Rural and urban areas are studied in 22 different transmitter-receiver links. The results are used to characterize the narrowband path loss, mean delay, root-mean-square (RMS) delay spread, and timing jitter of the peer-to-peer wideband channel. Small-scale fading characteristics are measured in detail by measuring and analyzing 160 PDPs within each local area. This thesis shows the measurement setup for the calculation of fading rate variance and angular spread and reports the first known attempt to calculate angular spread from track power measurements. New analysis presented in this thesis shows the effect of measurement error in the calculation of angular spread. The expected characteristics of angular spread are derived using two different angle-of-arrival (AOA) models from the literature. Measurement results show initial validation of Durgin's angular spread theory. A new measurement-based algorithm for simulating wideband fading processes is developed and implemented. This simulation technique shows promise in the simulation of high-bit rate peer-to-peer radio communication systems. / Master of Science
235

Enhancing design and performance analysis of satellite EB/CV-QKD/FSO systems

Nguyen, T.V., Le, H.T., Pham, H.T.T., Mai, Vuong, Dang, N.T. 11 August 2024 (has links)
Yes / Satellite QKD/FSO systems, which facilitate quantum key distribution (QKD) over free-space optical (FSO) links between satellites and ground stations, present a promising pathway toward achieving global security in upcoming sixth-generation (6G) wireless communications. Our study focuses on a superior type of these systems, the satellite EB/CV-QKD/FSO, which utilizes the continuous-variable (CV) method for quantum state representation and the entanglement-based (EB) scheme for QKD implementation. We propose the use of optical phase-shift keying (QPSK) signaling and dual-threshold/heterodyne detection (DT/HD) receivers to bolster the reliability and feasibility of satellite EB/CV-QKD/FSO systems. Closed-form expressions for key system performance metrics are derived using improved channel modeling. Numerical results are presented to showcase the effects of channel impairments on the system performance. We also provide recommendations for optimal system setup parameters, aiming to enhance performance. / Ministry of Information and Communications (Vietnam) (Grant Number: DT.26/23). Asia Pacific Network Information Centre (APNIC) Foundation under the Switch! Project
236

Gobuddy - Android mobile application

Nellaiappan, Kalaivani 01 January 2011 (has links)
The purpose of this application is to serve the end user of an Android Smart phone, with reliable, instantaneous and location based information on places of interest such as restaurants, gas stations, hotels, movie theaters, and the like by using the phones' built-in GPS. The basic information includes viewing the map and address of the place of interest and getting the directions to a particular place in addition to having some extra features. Contains computer source code.
237

Διερεύνηση των τεχνικών παραμέτρων για την μεγιστοποίηση της ποιότητας των παρεχομένων υπηρεσιών στα συστήματα MIMO

Φραγκιαδάκης, Αλέξανδρος 01 February 2013 (has links)
Στην παρούσα διπλωματική εργασία μελετάμε τα πλεονεκτήματα που επιφέρει η χρήση πολλαπλών κεραιών στον πομπό και στον δέκτη, κατά την μετάδοση, με στόχο την βελτίωση των παρεχομένων υπηρεσιών στο χρήστη. Στο Κεφάλαιο 1, γίνεται μια ιστορική αναδρομή των ασύρματων επικοινωνιών καθώς των σύγχρονων ασύρματων τεχνολογιών και κεραιών που χρησιμοποιούνται. Στη συνέχεια γίνεται μια αναφορά στις έννοιες του διαφορισμού, του κέρδους διάταξης και της χωρικής πολυπλεξίας οι οποίες συνδέονται άρρηκτα με τα συστήματα MIMO. Στο Κεφάλαιο 2, αναφερόμαστε σε όλα εκείνα τα χαρακτηριστικά που περιγράφουν το ασύρματο κανάλι και εξάγουμε την γραμμική σχέση εισόδου-εξόδου του ασύρματου καναλιού. Στην συνέχεια γίνεται μια ανάλυση των στοχαστικών μοντέλων περιγραφής του ασύρματου διαύλου διαλείψεων και πιο συγκεκριμένα των μοντέλων Rayleigh και Rice. Στο Κεφάλαιο 3 εξετάζουμε την αξιοπιστία διαφόρων τύπων κεραιοσυστημάτων, ως προς τον ρυθμό των ρυθμό των λανθασμένων συμβόλων στον δέκτη. Πιο συγκεκριμένα εξετάζεται η τεχνική Maximal Ratio Combining για τα συστήματα SIMO καθώς και του σχήματος Alamouti για τα συστήματα ΜISO. Συνεχίζοντας στα MIMO συστήματα αναλύουμε τις μεθόδους ισοστάθμισης για την ανάκτηση των δεδομένων, και πιο συγκεκριμένα τις τεχνικές Zero Forcing, Minimum Mean Square Error,V-Blast και καθώς και την βέλτιστη τεχνική Maximum Likelihood. Στο τελευταίο μέρος της εργασίας αναλύουμε τα πλεονεκτήματα των MIMO συστημάτων, ως προς την χωρητικότητα που προσφέρουν, σε στοχαστικά κανάλια διαλείψεων.Στη συνέχεια, γίνεται αναφορά στην μέθοδο SVD και στην αναπαράσταση του MIMO καναλιού από έναν αριθμό ανεξάρτητων SISO διαύλων. Κλείνοντας αναφέρουμε την μέθοδο βέλτιστης κατανομής ισχύος στις κεραίες του πομπού Water-filling, και στην περαιτέρω αύξηση της χωρητικότητας του διαύλου που προσφέρει. / In this diploma thesis we are investigating the benefits of using Multiple Input and Multiple Output antennas in information transmission, with final goal to improve Quality of Service. The first Chapter, includes a historical background of the wireless communications but also is a reference to the modern wireless and antenna technologies. Moreover, we introduce the definition of new concepts, such as diversity and array gain and also spatial multiplexing, which are closely connected with MIMO technology. In the second chapter, we introduce the characteristics which they are describe the wireless channel, while simultaneously we mention the linear input-output relationship of the wireless channel. Additionally, we analyze the stochastic wireless channel models, namely the Rayleigh and the Rician fading models. In the third chapter, we investigate the reliability of different types of antenna topologies, regarding the pace of the invalid symbols in the transmitter. More specifically, we examine the Maximal Ratio Combining and Alamouti technique, for SIMO and MISO systems respectively. The next step is to analyze the equalization methods, which are used in MIMO antennas, and more specifically are, Zero Forcing, Minimum Mean Square Error and V-Blast receivers, but also the optimal Maximum Likelihood equalizer. In the last part of this Thesis, we investigate the benefits of MIMO systems regarding the Capacity, in random channels. Also, a reference to the SVD method has been made,which we use to analyze the MIMO channel, in a number of parallel SISO channels. Lastly, we use the water-filling method to allocate, with the optimal way, the given power in the transmit antennas, a fact that leads to even greater Capacity gain.
238

VCO Banda Larga Integrado para Receptor a Cinco Portas

Brito Filho, Francisco de Assis 03 September 2009 (has links)
Made available in DSpace on 2014-12-17T14:55:40Z (GMT). No. of bitstreams: 1 FranciscoAB.pdf: 846082 bytes, checksum: d9718796dd9ac807f8f053e7d371d2bb (MD5) Previous issue date: 2009-09-03 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / This work presents an wideband ring VCO for cognitive radio five-port based receivers. A three-stage differential topology using transmission gate was adopted in order to maintain wide and linear tuning range and a low phase-noise. Monte-Carlo analysis were performed for phase-shift response of individual stages, which is an important figure of merit in five-port works. It was observed a fairly linear correlation between control voltage and oscillation frequency in the range between 200 MHz and 1800 MHz. The VCO was preliminarily designed for IBM 130nm CMOS technology / Este trabalho apresenta um VCO anel banda-larga para ser utilizado em receptores para R?dio Cognitivo baseados no correlator a cinco portas. Uma arquitetura diferencial de tr?s est?gios com porta de transmiss?o ? utilizada como forma de manter uma sintonia linear em larga faixa de frequ?ncias, bem como, um baixo ru?do de fase. An?lises de Monte-Carlo foram feita para avaliar as varia??es de fase em cada est?gio, o que constitui uma figura de m?rito importante em receptores baseados no correlator de cinco portas. Observou-se correspond?ncia razoavelmente linear entre tens?o de controle e freq??ncia de oscila??o na faixa compreendida entre 200 MHz e 1800 MHz. O VCO foi preliminarmente projetado para tecnologia CMOS IBM de 130 nan?metros
239

從金門後浦堂會議事錄看教會懲戒—一個教會史料的探究 / Church Discipline in the Registers of the Consistory of Au-Po, Quemoy - An Approach of Church History

陳子仁, Chen, Tzu-Ren Unknown Date (has links)
素來教會史的研究論述,多半是以「授方」—「宣教者」的角度,對所掌握的史料進行耙梳、權衡、取捨與評論,因而勾勒呈現的圖像從重心、成就到進展、變化皆以授方為依歸與主軸。我嘗試以相對(而非相斥,且可有力補足授方觀點)的「受方」—「受教者」的角度與史料,討論在基督宗教信仰實踐至關重要的議題:從保存完整的後浦堂會議事錄來探究關於「教會懲戒」的議題。 本論文作為一種呈現「受方」觀點(相對於「授方」觀點)的論述,同時也是一種地區教會史的建構嘗試。在進入論題核心的同時,注重教義與宗教傳統層面的梳理之外,也探求當地信徒如何承受、消化、進而發展重要的信仰質素、價值與行動。對於宗教教義層面,我梳理希伯來經文(或稱舊約)與新約裡關於教會與懲戒的相關經文,確定教會懲戒在信仰經典裡的脈絡、意義、作法與要求,並兼論及兩約之間(主要以死海古卷裡的昆蘭社群規條為本)的相關文獻。宗教傳統層面我從天主教的教會法典開始,依序檢視、比較與後浦堂會的發展相關的美國歸正教會、加拿大長老會(做為英國長老會的替代)與台灣基督長老教會等相關法規的處理模式。 另一方面,配合後浦堂會之形成、發展所處的歷史脈絡與其留下的完整議事記錄,我掌握了後浦堂會所有的教會懲戒記錄,呈現教會懲戒在後浦堂會發展歷程中在頻率、項目分配與消長等方面的實際情形,並將各懲戒事項之宗教教義與傳統論據與在現實中的法律、文化的相關處置作對照,凸顯受方面對真實的信仰—文化衝突時的取捨歷程。 我在論文研究過程中發現,後浦堂會議事錄裡的教會懲戒記錄最頻繁的施行高峰,恰恰是後浦堂會本身所處閩南大會的教勢發展大脈絡的最優進期(1903 至1912 年)。這一方面證明教會懲戒的正確施行,必當在教會處於信仰深深內化且質素高、內部彼此愛的關係豐厚與處理問題能力強的情態,另一方面也印證後浦教會在創立早期的確在上述各個方面有早熟而令人印象深刻的展現。自1866 年以降新教的金門島域福音工作,亟待方家更細緻綿密的史料整理與刻畫,更希望教會界願意開放議事錄等資料供學界進行嚴謹之學術研究與保存,以裨益地區教會史之建構。 / There are two specific approaches in the research of church history. One is the approach of the Givers / Preachers, focusing on 5 Ws (Who When Where What How) issues of the evangelization process, dealing with historical figures and events, and analyzing interactive relations in between these two factors mainly caused by or related to the side of the Gospel Conveyers. The other is the approach of the Receivers / Converts, an approach that the researchers will also use the 5Ws, concentrate on the converts instead of focusing on the conveyers. This approach is more and more common these days especially for the Chinese scholars. This thesis is not only an examination from the receivers’ point of view of how new Christian converts carried out the missionaries’ message by proceeding the actual practices of church discipline toward local converts in their cultural-religious context, but also an attempt of tracing the history of the Quemoy / Kinmen Churches. First of all, in the doctrinal-traditional aspect I have surveyed the biblical context (the Hebrew Scriptures or the Old Testament, and the New Testament) , related non-biblical sources, with the Church Laws like the Canon Law (the Roman Catholic Church), the Book of Church Order (the Reformed Church in America), the Book of Forms (The Presbyterian Church in Canada) , Bylaws (the Presbyterian Church in Taiwan) about church discipline and other cultural sources dealing with the secular treatments to these subjects. Secondly in the practical aspect, I have abstracted related Minutes of church discipline from the consistorial records of Au-Po congregation (between 1900 and 2000 C.E.), and found the period that church discipline being processed most frequently, was the time during 1903-1912: the most fruitful and powerful period of Christian Churches in China. However, the impressive manner shown in these records could be an illustration of the depth of the internalized messages for Protestant believers in Quemoy.
240

Estimativa das observáveis GPS da portadora L2 por meio de Redes Neurais Artificiais a partir de dados obtidos em dispositivos móveis / Estimation of the GPS L2 observables by use of Artificial Neural Networks from data obtained in mobile devices

Negri, Cassio Vinícius Carletti 19 December 2018 (has links)
Ao longo dos anos, o posicionamento por satélites artificiais através da geotecnologia Global Navigation Satellite System (GNSS) e, principalmente, por meio do sistema americano Global Positioning System (GPS), ganhou importante espaço na área de Geomática. A qualidade das soluções está diretamente relacionada, entre outros fatores, ao tipo de receptor utilizado no trabalho: dispositivos mais caros (geodésicos), capazes de gerar as portadoras L1 e L2 ou L1, L2 e L5, produzem os melhores resultados; por outro lado, receptores topográficos que rastreiam apenas a frequência L1 são mais baratos, mas tornam o processamento dos dados dependente de um modelo ionosférico para reduzir parcialmente os efeitos dessa origem. Visando melhorar as soluções de posicionamento com dispositivos de baixo custo e evitar despesas adicionais do usuário que, eventualmente, necessitaria de utilizar aparelhos mais onerosos, este trabalho tem como objetivo principal propor a implementação de uma Rede Neural Artificial (RNA) para estimar as observações da portadora L2 do sistema GPS com base nas observáveis da L1, buscando-se também aprimorar o método de predição destes dados elaborado em outras pesquisas. Para tanto, selecionou-se um modelo de rede através da técnica de Validação Cruzada (CV), estimaram-se as observações a partir das rastreadas tanto em um receptor geodésico como em um smartphone Android, e comparou-se a acurácia das soluções que foram processadas com e sem as observáveis artificiais criadas pela RNA. A técnica CV demonstrou que uma Multilayer Perceptron (MLP) de quatro camadas escondidas e outra de uma camada intermediária são as configurações mais apropriadas para estimação das observáveis do código e da fase da portadora L2, respectivamente. O tempo de aprendizagem em todos os experimentos não ultrapassou poucos segundos e o processamento dos arquivos RINEX de dupla frequência, criados neste trabalho, revelou melhorias significativas das soluções de posicionamento na maioria dos testes, reduzindo os desvios planos e espaciais em torno de 40 a 50% em relação aos resultados atingidos com apenas os dados originais da portadora L1, sendo que em alguns experimentos foi possível realizar a combinação iono-free (L3) e em outros atender a normativa de georreferenciamento de imóveis rurais do Instituto Nacional de Colonização e Reforma Agrária (INCRA). Os resultados apontam, portanto, que a proposta metodológica da presente investigação atua de forma bastante promissora e como uma alternativa ao uso de receptores mais caros. / Over the years, positioning by artificial satellites through the Global Navigation Satellite System (GNSS) and, mainly, through the American Global Positioning System (GPS), has become increasingly important in Geomatics. The quality of the solutions is directly related, among other factors, to the receiver type used in the work: more expensive (geodetic) devices, capable of generating the carriers L1 and L2 or L1, L2 and L5, produce the best results; conversely, topographic receivers which only trace the L1 frequency are cheaper, but make data processing dependent on an ionospheric model to partially reduce the effects of that source. In order to improve the positioning solutions with low cost devices and avoid additional financial costs to the user who would ultimately need to use more expensive devices, the main objective of this work is to propose the implementation of an Artificial Neural Network (ANN) to estimate the GPS L2 observations from the L1 observables, aiming also to improve the prediction method elaborated in other research. This was done by using the Cross-Validation (CV) technique to select a network model. The observations were estimated from observables tracked on both a geodetic receiver and an Android smartphone, and we compared the accuracy of the solutions that were processed with and without the artificial observations created by the ANN. The CV technique demonstrated that a Multilayer Perceptron (MLP) of four hidden layers and another of an intermediate layer are the most appropriate configurations for the estimation of the L2 code and phase observables, respectively. The learning time in all the tests did not exceed a few seconds and the processing of the dual frequency RINEX files, which were created in this work, revealed significant improvements in the positioning solutions in all the experiments. The plane and spatial deviations were reduced by around 40% to 50% in relation to the results obtained with only the original L1 carrier data. In some tests it was possible to perform the iono-free combination (L3) and in others to meet the georeferencing regulations for rural properties of the National Institute of Colonization and Agrarian Reform (INCRA). The results indicate, therefore, that the methodological proposal of the present investigation acts in a very promising way and as an alternative to the use of more expensive receivers.

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