Resumo: O multicaminho é um dos fenômenos que ocorre quando o sinal proveniente do Global Navigation Satellite System (GNSS) reflete em objetos localizados nas proximidades do levantamento e chega ao receptor via múltiplos caminhos. Geralmente, o receptor GNSS recebe além do sinal direto, também o sinal refletido, o qual é atrasado em relação ao sinal direto. Conseqüentemente, as medidas de pseudodistância (PD) e fase de batimento da onda portadora são rastreadas para um sinal composto, e não para o sinal direto, causando o erro do multicaminho. Esse efeito é uma fonte de erro significativa que ainda permanece como um desafio para a pesquisa, especialmente para o posicionamento relativo estático e cinemático em aplicações de alta precisão. Diferentemente dos demais erros, o multicaminho não é atenuado quando se formam as duplas diferenças (DD) em uma linha de base curta, por ser um efeito altamente dependente do local do levantamento. Pelo contrário, os erros de multicaminho podem aumentar no processo de dupla diferenciação. Nessa pesquisa foi proposta uma metodologia, viável em termos práticos e econômicos, capaz de detectar e corrigir o efeito do multicaminho nas observações de fase da onda portadora e PD L1 e/ou L2 para aplicações estáticas e cinemáticas, quer sejam pós-processadas ou em tempo real. Essa metodologia é baseada na Análise de Multirresolução (AMR) utilizando a Transformada de Wavelets (TW). A TW é aplicada para decompor as séries temporais dos resíduos das DDs do ajustamento em componentes de freqüências baixa e alta... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: GNSS-multipath is a phenomenon that occurs when the signal from Global Navigation Satellite System (GNSS) reflects on objects surrounding the survey environment and reaches the receiver antenna through multiple paths. Usually, the GNSS receiver also collects the reflected signal, which is delayed in relation to the direct one. Consequently, the pseudorange (code) and carrier phase measurements are tracked for a composed signal, and not for the direct signal, causing a multipath error. This effect is a significant error source that still remains as a challenge for the research, especially for static and kinematic relative positioning in high-precision applications. Differently from other errors sources, multipath is not attenuated when the double differences (DD) are formed in a short baseline, because this error is highly dependent upon the surrounding environment. On the contrary, multipath errors can even increase in the double differentiation process. In this research a feasible and economic methodology, able of detecting and correcting the multipath effect from the carrier phase and pseudorange L1 and/or L2 for static and kinematic applications, post-processed or in real time. This approach is based on the Multiresolution Analysis (MRA) using the Wavelet Transform (WT)... (Complete abstract click electronic access below) / Orientador: João Francisco Galera Monico / Coorientador: Aylton Pagamisse / Banca: Hélio Magalhães de Oliveira / Banca: Silvio Rogério Correia Freitas / Banca: Messias Meneguette Junior / Banca: Paulo de Oliveira Camargo / Doutor

Les systèmes GNSS sont actuellement utilisés en aviation civile pour estimer la position et la vitesse de l'avion pendant les phases de route jusqu'aux approches de précision. Etendre l'utilisation de GNSS aux opérations de surface en environnement aéroportuaire et sous de faibles conditions de visibilité reste un challenge pour la communauté aviation civile. En effet, durant ces opérations, les mesures GNSS peuvent être affectées par des évènements singuliers tels que les multi-trajet ou les anomalies ionosphériques. Ces évènements peuvent engendrer des erreurs de position jugées inacceptables en termes de précision et d'intégrité pour assurer le guidage de l'avion. Les algorithmes de surveillance d'intégrité GNSS actuellement utilisés ne sont pas conçus pour prendre totalement en compte les effets de tels évènements. Il est essentiel de développer des algorithmes de surveillance conçus pour protéger les utilisateurs des effets de tels évènements afin de pouvoir utiliser GNSS pour le guidage de l'avion en milieu aéroportuaire et sous de faibles conditions de visibilité. Afin de concevoir de tels algorithmes de surveillance d'intégrité, il est nécessaire de développer des modèles d'erreurs de mesures GNSS et des modèles de pannes GNSS. La thèse a été principalement orientée vers la conception de modèles d'erreurs de mesures GNSS dues aux multi-trajets et vers le développement de modèles de pannes GNSS dues aux multi-trajets. Pour ce faire, un modèle d'erreurs multi-trajets GNSS sur les mesures bi-fréquence GPSL1C+GPSL5 et GalileoE1+GalileoE5a a d'abord été proposé. Ensuite, l'impact des multi-trajets sur l'erreur de position a été étudié. Pour cette étude, un algorithme de couplage serré GPS+Galileo/IRS a été considéré. Cet algorithme est basé sur un filtre de Kalman linéarisé. Une analyse théorique et quantitative a été conduite pour étudier l'impact des erreurs de mesures GNSS dues aux multi-trajets sur le biais et sur la matrice de covariance de l'erreur de position horizontale en sortie de l'algorithme de positionnement considéré. Finalement, un modèle de pannes GNSS dues aux multi-trajets a été proposé. Ce modèle décrit la signature des pannes multi-trajets, les facteurs influençant cette signature, le modèle d'occurrence des pannes multi-trajets ainsi que les conditions d'occurrence de telles pannes / GNSSs are currently used in civil aviation to provide aircraft with position and velocity estimates from en-route to precision approach operations. Extending the use of GNSS to the guidance function during airport surface operations and under zero-visibility conditions remains a challenge. Indeed, during these operations, GNSS measurements may be affected by GNSS singular events, such as multipath or ionosphere anomalies. GNSS singular events may lead to unacceptable position errors in terms of accuracy and integrity for the zero-visibility guidance function. Current GNSS integrity monitoring systems are not designed to totally account for the GNSS singular event effects. The development of GNSS integrity monitoring systems designed to properly protect users from the singular event effects is essential to use GNSS for the guidance function under zero-visibility conditions. GNSS measurement error and integrity failure models are key inputs in the design of GNSS integrity monitoring systems. In this thesis, work has been mainly focused on the development of GNSS multipath measurement errors, on the assessment of the multipath impact on the GNSS-based position error, and on the development of GNSS multipath integrity failure models. For this matter, the dual frequency GPSL1C+GPSL5 and GalileoE1+GalileoE5a multipath pseudo- range error model adapted to airport navigation has been firstly proposed. Next, the impact of multipath on the GNSS-based position error has been assessed. To do so, a double constellation GPS+Galileo/IRS tight coupling algorithm based on a linearized Kalman filter has been selected. The theoretical and quantitative analysis of the impact of the GNSS multipath ranging errors on the horizontal position bias and on the covariance matrix of the horizontal position error have been proposed. Finally, a GNSS multipath integrity failure model has been proposed. The model describes the signature of the GNSS single multipath ranging failures, the factors influencing the signature as well as the occurrence model of these failures and their conditions of occurrence.

An important aspect of upcoming fifth-generation (5G) cellular communication systems is to improve the accuracy with which user equipments can be positioned. Accurately knowing the position of a user equipment is becoming increasingly important for a wide range of applications, such as automation in industry, drones, and the internet of things. Contrary to how existing techniques for outdoor cellular positioning deal with multipath propagation, in this study the aim is to use, rather than mitigate, the multipath propagation prevalent in dense urban environments. It is investigated whether it is possible to position a user equipment using only a single transmitting base station, by exploiting position-related information in multipath components inherent in the received signal. Two algorithms are developed: one classical point-estimation algorithm using a grid search to find the cost function-minimizing position, and one Bayesian filtering algorithm using a point-mass filter. Both algorithms make use of BEZT, a set of 3D propagation models developed by Ericsson Research, to predict propagation paths. A model of the signal received by a user equipment is formulated for use in the positioning algorithms. In addition to the signal model, the algorithms also require a digital map of the propagation environment. The algorithms are evaluated first on synthetic measurements, generated using BEZT, and then on real-world measurements. For both the synthetic and real-world measurement sets, the Bayesian point-mass filter outperforms the classical algorithm. It is observed how, given synthetic measurements, the algorithms yield better estimates in non-line-of-sight regions than in regions where the user equipment has line-of-sight to the transmitting base station. Unfortunately, these results do not generalize well to the real-world measurements, where, overall, neither algorithm is able to provide reliable and robust position estimates. However, as multipath-assisted positioning, to the best of our knowledge, has not been used for outdoor cellular positioning before, there are plenty of algorithm extensions, modifications, and problem aspects left to be studied - some of which are discussed in the concluding chapters.

abstract: Autonomous vehicle control systems utilize real-time kinematic Global Navigation Satellite Systems (GNSS) receivers to provide a position within two-centimeter of truth. GNSS receivers utilize the satellite signal time of arrival estimates to solve for position; and multipath corrupts the time of arrival estimates with a time-varying bias. Time of arrival estimates are based upon accurate direct sequence spread spectrum (DSSS) code and carrier phase tracking. Current multipath mitigating GNSS solutions include fixed radiation pattern antennas and windowed delay-lock loop code phase discriminators. A new multipath mitigating code tracking algorithm is introduced that utilizes a non-symmetric correlation kernel to reject multipath. Independent parameters provide a means to trade-off code tracking discriminant gain against multipath mitigation performance. The algorithm performance is characterized in terms of multipath phase error bias, phase error estimation variance, tracking range, tracking ambiguity and implementation complexity. The algorithm is suitable for modernized GNSS signals including Binary Phase Shift Keyed (BPSK) and a variety of Binary Offset Keyed (BOC) signals. The algorithm compensates for unbalanced code sequences to ensure a code tracking bias does not result from the use of asymmetric correlation kernels. The algorithm does not require explicit knowledge of the propagation channel model. Design recommendations for selecting the algorithm parameters to mitigate precorrelation filter distortion are also provided. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

The transmitting of video content over Vehicular Ad Hoc Networks (VANETs) faces a great number of challenges caused by strict QoS (Quality of Service) requirements and highly dynamic network topology. In order to tackle these challenges, multipath forwarding schemes can be regarded as potential solutions. However, route coupling effect and the path length growth severely impair the performance of multipath schemes. In this thesis, the current research status about video streaming over VANETs as well as multipath transmissions are reviewed. With the demand to discover a more suitable solution, we propose the Location-Aware Multipath Video Streaming (LIAITHON+) protocol to address video streaming over urban VANETs. LIAITHON+ uses location information to discover relatively short paths with minimal route coupling effect. The performance results have shown it outperforms the underlying single path solution as well as the node-disjoint multipath solution. In addition, the impact of added redundancy on the multipath solution is investigated through LIAITHON+. According to the results, added redundancy has a different impact depending on the data rate.

One of the problems sensor networks face is adversaries corrupting nodes along the path to the base station. One way to reduce the effect of these attacks is multipath routing. This introduces some intrusion-tolerance in the network by way of redundancy but at the cost of a higher power consumption by the sensor nodes. Erasure coding can be applied to this scenario in which the base station can receive a subset of the total data sent and reconstruct the entire message packet at its end. This thesis uses two commonly used encodings and compares their performance with respect to power consumed for unencoded data in multipath routing. It is found that using encoding with multipath routing reduces the power consumption and at the same time enables the user to send reasonably large data sizes. The experiments in this thesis were performed on the Tiny OS platform with the simulations done in TOSSIM and the power measurements were taken in PowerTOSSIM. They were performed on the simple radio model and the lossy radio model provided by Tiny OS. The lossy radio model was simulated with distances of 10 feet, 15 feet and 20 feet between nodes. It was found that by using erasure encoding, double or triple the data size can be sent at the same power consumption rate as unencoded data. All the experiments were performed with the radio set at a normal transmit power, and later a high transmit power.

This work deals with multipath transmission in the data networks to speed up transmission over networks with limited transmission speed. Work compares the characteristics, efficiency and response to changes in individual transmission paths. Work is specifically dedicated to MPT and MPTCP mechanisms.

The possibility of polarization diversity using left and right hand circular polarization (LHCP and RHCP) in the presence of multipath propagation is examined. We show that there are differences in the received signal for LHCP and RHCP for a number of realistic scenarios. Because multipath propagation can produce different LHCP and RCHP signals, there exists the possibility for diversity improvement involving the two polarizations.

No / Satellite networks are expected to support multimedia traffic flows, offering high capacity with QoS guarantees. However, system efficiency is often impaired by packet losses due to erasure channel effects. Reconfigurable and adaptive air interfaces are possible solutions to alleviate some of these issues. On the other hand, network coding is a promising technique to improve satellite network performance. This position paper reports on potential applications of network coding to satellite networks. Surveys and preliminary numerical results are provided on network coding applications to different exemplary satellite scenarios. Specifically, the adoption of Random Linear Network Coding (RLNC) is considered in three cases, namely, multicast transmissions, handover for multihomed aircraft mobile terminals, and multipath TCP-based applications. OSI layers on which the implementation of networking coding would potentially yield benefits are also recommended.

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