Periodic Frequency Selective Surfaces for Reduction of Specular Scatter in Indoor Applications

This thesis investigates the use of a variety of passive frequency selective surfaces for specular scatter reduction. Motivation from this work stems from the increased interest in controlling propagation in indoor environments. Influencing the propagation environment using both passive and active structures is of current research interest due to the increased use of wireless devices inside building structures. This thesis aims to develop surfaces suitable for installation on corridor walls to work alongside existing solutions. An initial literature review of frequency selective surfaces; particularly for use inside buildings to create smart environments, suggests reducing the propagation down corridors could be beneficial in decreasing co-channel interference although no solutions have been offered. Development of the initial comb frequency selective surface (CR-FSS) enabled measurement systems and simulation models to be constructed and compared. Due to the various limitations of the CR-FSS, design modifications and evolutions are investigated to overcome issues with poor angular performance, polarisation dependant performance, and experimental manufacture. The initial challenge was to create a rotationally symmetrical surface which could reduce specular scatter from additional angles of incidence in the elevation plane. A pin reflection FSS (PR-FSS) was created, however investigation of the structure showed that it was ineffectual for TE polarisation. In a multipath environment this could be an issue which effects performance. Investigation of additional variations of the CR-FSS such as the slanted comb FSS (SC-FSS) and crenelated CR-FSS complete the analysis. A validation of a frequency selective comb structures is conducted with in-building multipath simulations. Statistical plots show that a comb structure can be used to significantly improve the signal-to-interference ratio (SIR) of co-channel transmitters at 2.4 GHz by reducing propagation down a corridor

Enhancing wireless communication system performance through modified indoor environments

This thesis reports the methods, the deployment strategies and the resulting system performance improvement of in-building environmental modification. With the increasing use of mobile computing devices such as PDAs, laptops, and the expansion of wireless local area networks (WLANs), there is growing interest in increasing productivity and efficiency through enhancing received signal power. This thesis proposes the deployment of waveguides consisting of frequency selective surfaces (FSSs) in indoor wireless environments and investigates their effect on radio wave propagation. The received power of the obstructed (OBS) path is attenuated significantly as compared with that of the line of sight (LOS) path, thereby requiring an additional link budget margin as well as increased battery power drain. In this thesis, the use of an innovative model is also presented to selectively enhance radio propagation in indoor areas under OBS conditions by reflecting the channel radio signals into areas of interest in order to avoid significant propagation loss. An FSS is a surface which exhibits reflection and/or transmission properties as a function of frequency. An FSS with a pass band frequency response was applied to an ordinary or modified wall as a wallpaper to transform the wall into a frequency selective (FS) wall (FS-WALL) or frequency selective modified wall (FS-MWALL). Measurements have shown that the innovative model prototype can enhance 2.4GHz (IEEE 802.11b/g/n) transmissions in addition to the unmodified wall, whereas other radio services, such as cellular telephony at 1.8GHz, have other routes to penetrate or escape. The FSS performance has been examined intensely by both equivalent circuit modelling, simulation, and practical measurements. Factors that influence FSS performance such as the FSS element dimensions, element conductivities, dielectric substrates adjacent to the FSS, and signal incident angles, were investigated. By keeping the elements small and densely packed, a largely angle-insensitive FSS was developed as a promising prototype for FSS wallpaper. Accordingly, the resultant can be modelled by cascading the effects of the FSS wallpaper and the ordinary wall (FSWALL) or modified wall (FS-MWALL). Good agreement between the modelled, simulated, and the measured results was observed. Finally, a small-scale indoor environment has been constructed and measured in a half-wave chamber and free space measurements in order to practically verify this approach and through the usage of the deterministic ray tracing technique. An initial investigation showing that the use of an innovative model can increase capacity in MIMO systems. This can be explained by the presence of strong multipath components which give rise to a low correlated Rayleigh Channel. This research work has linked the fields of antenna design, communication systems, and building architecture

ATS-6 engineering performance report. Volume 5: Propagation experiments

Propagation experiments at 1550 MHz to 1650 MHz are reviewed, including the Integrated L-Band Experiments system and results, and the Mobile L-Band Terminals for Satellite Communication system. Experiments at 4 GHz to 6 GHz are reported, including the Radio Frequency Interferometer Measurements system and results, and Earth station antenna evaluations. Experiments above 10 GHz are discussed, including Comsat and ATS-6 millimeter wave propagation/experiments, and communication ATS-6 version at 20 and 30 GHz

Analyse et conception de répéteurs passifs plans à rayonnement quasi-latéral pour communications «indoor» à 60GHz

The fast development of information and consumer electronics industries creates a pressing demand for high-speed indoor communications. Traditional communication protocols are unable to support such high transmission rate, and there are no radio bands available at lower frequency. As an alternative, 60GHz communications have sparked great attention, since it enables a maximum data transmission rate more than 5Gbit/s based on its wide unlicensed bandwidth. However, practical indoor environment is usually complicated (e.g. walls, corridors, stairs, etc.), thus the non-line-of-sight (NLOS) areas cannot be covered due to the significant attenuation. Considering the requirements for signal recovery in the NLOS environment, a planar passive repeater with endfire radiation and high directivity, low profile and low cost is investigated and designed in this thesis. Based on array theory, a periodic structure for the foreseen printed repeater is derived out. It involves two reflector elements (in the spacing of 2) to provide 0° and 180°reflection phases respectively. In order to construct a proper reflector element, four topologies are proposed and analyzed. In the first part of the study, DRA (Dielectric Resonator Antenna) technology is the main focus. Two different topologies are investigated and compared, including notched DRA and DRA coupled to phase-shift stub. Different modeling strategies are also studied using either a single cell, a couple of cells with opposite phases or a small array. For each topology, a preliminary 6×6 array is simulated. Optimization at the array level is emphasized through the whole thesis. In the second part, investigations are taken on a rectangular dielectric filled waveguide element. Parametric analyses are carried out and possible fabrication technologies are discussed. Once again, a preliminary 6×6 array is designed and optimized to validate the feasibility of such a structure. In the third part, a parallel-plate groove structure is analyzed. It evolves from the rectangular waveguide, and enjoys more simplification. Further work is taken to explore the arrays’ bandwidth, oblique incidence performance and maximum radiation direction. Detailed theoretical analysis based on the simulation results are demonstrated in the end. Finally, an array based on the groove elements is fabricated in the size of 200mm×200mm. Practical measurements for 60GHz communications in NLOS environment are designed to test the array’s performance. Analyses on the experiment results are given.Le développement rapide de l’industrie des systèmes sans fil suscite une demande urgente pour des communications à haut débit, notamment en environnement « indoor ». Toutefois, les protocoles traditionnels de communications sont incapables de supporter de très hauts débits et, surtout, il n'y a pas de ressources spectrales disponibles à basse fréquence. Comme une alternative, la bande des 60GHz est préconisée parce qu’elle permet un débit de plus de 5Gbit/s, grâce à son large spectre (57GHz à 64 GHz). Toutefois, en pratique, l’environnement « indoor » est complexe et, dans les situations d’absence de visibilité directe, la couverture radio est difficile à assurer à cause des fortes atténuations. Afin de remédier à ce problème, l’utilisation de répéteurs est possible. Dans cette thèse, l’intérêt est porté sur les répéteurs passifs, plus simples à installer et compatibles avec une réalisation faible coût. Le cas critique de la couverture radio d’un couloir en T est choisi comme fil conducteur, tout au long de cette étude. Les solutions préconisées visent aussi la compacité, ce qui justifie l’utilisation de réflecteurs plans. A partir de la théorie des réseaux d’antennes, une structure périodique générique pour le répéteur est proposée. Elle implique deux cellules réfléchissantes élémentaires (espacées de /2), produisant des ondes en opposition de phase. Plusieurs topologies et technologies sont ensuite envisagées et étudiées pour la mise en oeuvre. La première utilise des antennes à résonateur diélectrique (DRA). Deux topologies différentes sont étudiées et comparées, le DRA à encoche et le DRA couplé à une ligne déphaseuse en circuit ouvert. Différentes stratégies de modélisation sont également étudiées en utilisant une cellule unique, un couple de 2 cellules avec phases opposées ou un petit réseau. Pour chaque topologie, un réseau canonique de 6×6 éléments est simulé. La deuxième technologie étudiée utilise des guides d’ondes rectangulaires chargés par un matériau diélectrique et courtcircuités. Des analyses paramétriques sont effectuées et un 6 ×6 réseau est conçu et optimisé pour valider la faisabilité de la solution. Finalement, une structure en guide à plaques métalliques parallèles est analysée. Dérivant de la solution précédente, elle permet une fabrication plus simple. Pour cette dernière solution, une analyse plus complète est menée incluant des considérations sur la bande passante, les performances en incidence oblique et la direction de rayonnement maximal. Enfin, un réseau à base de cet élément rainuré est fabriquée présentant une taille de 200 mm×200 mm. Des mesures expérimentales à 60GHz sont réalisées pour tester les performances du réseau. La preuve de concept est ainsi donnée et les résultats expérimentaux sont analysés

Evaluation of Alternative Telecommunication Technologies for the Karoo Central Astronomy Advantage Area

Cite: Academy of Science of South Africa (ASSAf), (2021). Evaluation of Alternative Telecommunication Technologies for the Karoo Central Astronomy Advantage Area. [Online] Available at: DOI http://dx.doi.org/10.17159/assaf.2021/0073The National Research Foundation (NRF) requested the Academy of Science of South Africa (ASSAf), on behalf of South African Radio Astronomy Observatory (SARAO) and the Square Kilometre Array (SKA), to undertake an independent and objective evaluation of potential alternative telecommunication technologies for the areas of the Karoo Central Astronomy Advantage Areas (KCAAA). The study encompasses regulatory, public sphere, and technical dimensions to explore options for maintaining the functionality of the telescope while, at the same time, delivering appropriate connectivity solutions for local communities.The objectives of this study are as follows:1) Assess the technologies currently being, or planning to be, deployed through existing alternative communications programs managed by SARAO, including whether these technologies are comparable with market available technologies that could feasibly be deployed in the KCAAA; and2) Assessment of current and future telecommunication technologies that may act as suitable replacement and/or improvement (functional and feasible) for existing detrimental technologies, utilised in the KCAAA.This report provides a critical background into the relationship between the SKA and local communities as it relates to ICTs in the area. Based on this understanding, potential technology solutions are proposed to ensure residents of the KCAAA are still afforded valuable access to information and communication technologies (ICTs) within the parameters of affordability, desirability and feasibility.National Research Foundation (NRF

Biomedical Engineering

Biomedical engineering is currently relatively wide scientific area which has been constantly bringing innovations with an objective to support and improve all areas of medicine such as therapy, diagnostics and rehabilitation. It holds a strong position also in natural and biological sciences. In the terms of application, biomedical engineering is present at almost all technical universities where some of them are targeted for the research and development in this area. The presented book brings chosen outputs and results of research and development tasks, often supported by important world or European framework programs or grant agencies. The knowledge and findings from the area of biomaterials, bioelectronics, bioinformatics, biomedical devices and tools or computer support in the processes of diagnostics and therapy are defined in a way that they bring both basic information to a reader and also specific outputs with a possible further use in research and development

Developing a person guidance module for hospital robots

This dissertation describes the design and implementation of the Person Guidance Module (PGM) that enables the IWARD (Intelligent Robot Swarm for attendance, Recognition, Cleaning and delivery) base robot to offer route guidance service to the patients or visitors inside the hospital arena. One of the common problems encountered in huge hospital buildings today is foreigners not being able to find their way around in the hospital. Although there are a variety of guide robots currently existing on the market and offering a wide range of guidance and related activities, they do not fit into the modular concept of the IWARD project. The PGM features a robust and foolproof non-hierarchical sensor fusion approach of an active RFID, stereovision and cricket mote sensor for guiding a patient to the X-ray room, or a visitor to a patient’s ward in every possible scenario in a complex, dynamic and crowded hospital environment. Moreover, the speed of the robot can be adjusted automatically according to the pace of the follower for physical comfort using this system. Furthermore, the module performs these tasks in any unconstructed environment solely from a robot’s onboard perceptual resources in order to limit the hardware installation costs and therefore the indoor setting support. Similar comprehensive solution in one single platform has remained elusive in existing literature. The finished module can be connected to any IWARD base robot using quick-change mechanical connections and standard electrical connections. The PGM module box is equipped with a Gumstix embedded computer for all module computing which is powered up automatically once the module box is inserted into the robot. In line with the general software architecture of the IWARD project, all software modules are developed as Orca2 components and cross-complied for Gumstix’s XScale processor. To support standardized communication between different software components, Internet Communications Engine (Ice) has been used as middleware. Additionally, plug-and-play capabilities have been developed and incorporated so that swarm system is aware at all times of which robot is equipped with PGM. Finally, in several field trials in hospital environments, the person guidance module has shown its suitability for a challenging real-world application as well as the necessary user acceptance

Systèmes de communications à ondes millimétriques pour mines souterraines

Le niveau croissant d’automatisation des exploitations minières souterraines vise à en accroitre l’efficacité et s’appuiera sur la venue d’une myriade de dispositifs électroniques au sein des corridors souterrains. Dans d’autre environnements confinés, par exemple les opérations militaires dans les cavernes, ces dispositifs peuvent engendrer un avantage tactique fort important aux utilisateurs. Notre travail de recherche s’inscrit dans la perspective du développement d’un système de communications à haut débit binaire pour les applications comme la surveillance et le transfert de donnée vidéo en temps réel dans la mine. Cette étude est focalisée sur la performance du système de communications sans fil à ondes millimétriques dans une mine souterraine. La première contribution de notre étude consiste à étudier tous les problèmes reliés au déploiement de ce système dans la mine. Comme il n’existe pas de travaux qui traitent ce genre de sujet, nous avons commencé notre étude par une caractérisation du canal à ondes millimétriques dans la mine CANMET à Val-d’Or située à 500 km au nord de Montréal, Canada. Nous avons mis en oeuvre un montage expérimental de mesures basé sur un robot Velmex. Les mesures ont été effectuées dans la plage fréquentielle du standard IEEE802.15.3c, soit 57.24-59.4 GHz. Nous sommes parvenus à une caractérisation du canal de propagation à ondes millimétriques dans deux galeries de la mine, au niveau 40 et au niveau 70 m et selon plusieurs combinaisons d’antenne, directive-directive, directive-omni et omnidirective et pour deux polarisations, soit verticale-verticale et horizontale-horizontale. Dans le but de comparer les résultats, le même montage est utilisé pour effectuer des mesures dans un milieu interne, soit le laboratoire CANMET. La deuxième contribution de notre étude consiste à calculer la capacité du canal selon les scénarios des mesures. La formule classique de la capacité de Shannon est obtenue pour les canaux ayant des réponses fréquentielles plates. Cette formule ne s’applique pas directement dans notre cas à cause de la sélectivité de la réponse en fréquence du canal. Nous avons divisé la bande de fréquences en un nombre très grand de petites bandes, considérées comme des sous-canaux à réponse plate dans le domaine fréquentiel. Ensuite, nous avons distribué la puissance d’une manière optimale sur les sous-canaux plats. Les résultats obtenus sont comparés aussi avec les résultats obtenus si une distribution uniforme est adoptée à l’émission. Les résultats prouvent la pertinence de la méthode optimale dans ces type des canaux ; cette méthode donne une amélioration importante de la capacité lorsque le SNR est faible. Les deux méthodes donnent les mêmes résultats lorsque le SNR est grand. La troisième contribution de notre étude vise à utiliser les paramètres obtenus de la compagne de mesures, comme la bande de cohérence et l’étalement maximal du canal pour les différents scénarios, pour calculer les paramètres du système OFDM à ondes millimétriques. Dans le but de rendre notre travail plus pertinent, nous avons calculé la limite de Shannon en posant le débit binaire du système OFDM égal à la capacité optimale ou à la capacité uniforme du canal. Plusieurs simulations ont été faites en fonction de la distance, de la longueur du préfixe cyclique et du nombre de sous-porteuses. Nous avons utilisé un code LDPC avec un taux égal à 0.75 pour améliorer le taux d’erreur binaire et aussi s’approcher de la limite de Shannon. Les résultats obtenus montre que les systèmes OFDM avec une combinaison d’antennes directive-directive et une polarisation verticale-verticale ont une meilleure performance aux niveaux 40 m et 70 m et dans le laboratoire CANMET.The increasing level of automation in underground mining operations in order to improve their efficiency will bring a myriad of electronic devices into the mine shafts. In other confined environment situations, e.g. military operations in caverns, electronic devices can yield a significant tactical advantage. Our research is in the perspective of developing a system of high bit rate communications for applications that require high throughput such as monitoring and transfer of video data in real time in the mine. This thesis is focused on the study of the performance of a wireless communications system in the millimeter wave range in an underground mine. The contribution part of the study is to examine all issues related to the deployment of this system in the mine. As there is no work dealing with this kind of topic, we started our research by a characterization of the millimeter-wave channel in the CANMET mine in Val-d’Or, located 500 km north of Montreal, Canada. We implemented a breadboard measurement system based on a Velmex robot table. The measurements were performed in the frequency range of the standard IEEE802.15.3c or 57.24-59.4 GHz.We have obtained a characterization of the millimeter wave propagation channel in two galleries of the mine, at 40 and 70 m, according to several combinations of antennas, directive-directive, directive-omni and omni-directive and for both vertical-vertical and horizontal-horizontal polarizations. In order to compare the results, the same measuring setup was used to perform measurements in an internal environment in the CANMET laboratory. The second contribution of the thesis was to compute the channel capacity according to the measurement scenarios. The classical formula for the Shannon capacity is used for flat channels. This formula does not directly apply in this case because of the selectivity of the channel frequency response. Thus, we divided the whole frequency band into many sub-bands, in which the sub-channel can be considered frequency-flat. Then we distributed the power optimally on the flat sub-channels. The results were also compared with the results obtained if a uniform distribution was adopted. The results prove the relevance of the optimal method in these types of channels. This method gives a significant improvement of the capacity when the SNR is low. Both methods give the same results when the signal to noise ratio is high. The third contribution of this thesis focused on how to use the parameters obtained from the measurement campaign such as the coherence bandwidth and the maximum spread of the channel for the different scenarios, to calculate the parameters of the OFDM millimeter wave system. In order to make our work relevant, we calculated the Shannon limit by setting the bit rate of the OFDM system equal to the optimal capacity or to the uniform channel capacity. Many simulations were made based on the distance between the antennas, the cyclic prefix length and the number of sub-carriers. We used an LDPC code with a rate equal to 0.75 to improve the bit error rate and hence to approach the Shannon limit. The results show that the OFDM millimeter wave system with D-D combination and VV polarization has better performance at 40 m, 70 m and in the CANMET laboratory