In this study, a review of research literature has been carried out to investigate Hybrid Time and wavelength Division Multiplexing techniques with respect to reach, split ratio, and speed of the network. This was done to overcome challenges presented by Passive Optical Networks, such as the reach and the high split ratio. A comparison of different methods clarifies that Hybrid PassiveOptical Networks have a high power-budget that ensure efficient signal transmission. The Optisys software has been used to analyze the performance of the different techniques.

L'objectif général de cette thèse était de proposer une solution de localisation en intérieur à la fois simple et capable de surmonter les défis de la propagation dans les environnements en intérieur. Pour ce faire, un système de localisation basé sur la méthode des signatures et adoptant le temps d'arrivée du signal de l'émetteur au récepteur comme signature, a été proposé. Le système présente deux architectures différentes, une première orientée privée utilisant la méthode d'accès multiple à répartition par code et une deuxième centralisée basée sur la méthode d'accès multiple à répartition dans le temps. Le système calcule la position de l'objet d'intérêt par la méthode de noyau. Une comparaison expérimentale entre le système à architecture orientée privée et un système de localisation sonore déjà existant et basé sur la méthode de trilatération, a permis de confirmer les résultats trouvés dans le cas de la localisation par ondes radiofréquences. Cependant, nos expérimentations étaient les premières à montrer l'effet de la réverbération sur les approches de la localisation acoustique. Dans un second lieu, un système de localisation basé sur la technique de retournement temporel, permettant une localisation simultanée de sources avec différentes précisions, a été testé par simulations en faisant varier le nombre de sources. Ce système a été ensuite validé par expérimentations. Dans la dernière partie de notre étude, nous nous sommes intéressés à la réduction de l'audibilité du signal utile à la localisation par recours à la psycho-acoustique. Un filtre défini à partir du seuil d'audition absolu a été appliqué au signal de localisation. Nos résultats ont montré une amélioration de la précision de localisation comparé au système de localisation sans modèle psycho-acoustique et ce grâce à l'utilisation d'un filtre adapté au modèle psycho-acoustique à la réception. Par ailleurs, l'écoute du signal après application du modèle psycho-acoustique a montré une réduction significative de son audibilité comparée à celle du signal original. / The objective of this PhD is to propose a location solution that should be simple and robust to multipath that characterizes the indoor environments. First, a location system that exploits the time domain of channel parameters has been proposed. The system adopts the time of arrival of the path of maximum amplitude as a signature and estimates the target position through nonparametric kernel regression. The system was evaluated in experiments for two main configurations: a privacy-oriented configuration with code-division multiple-access operation and a centralized configuration with time-division multiple-access operation. A comparison between our privacy-oriented system and another acoustic location system based on code-division multiple-access operation and lateration method confirms the results found in radiofrequency-based localization. However, our experiments are the first to demonstrate the detrimental effect that reverberation has on acoustic localization approaches. Second, a location system based on time reversal technique and able to localize simultaneously sources with different location precisions has been tested through simulations for different values of the number of sources. The system has then been validated by experiments. Finally, we have been interested in reducing the audibility of the localization signal through psycho-acoustics. A filter, set from the absolute threshold of hearing, is then applied to the signal. Our results showed an improvement in precision, when compared to the location system without psychoacoustic model, thanks to the use of matched filter at the receiver. Moreover, we have noticed a significant reduction in the audibility of the filtered signal compared to that of the original signal.

A wireless sensor network (WSN) is a collection of sensor nodes distributed over a geographical region to obtain the environmental data. It can have different types of applications ranging from low data rate event driven and monitoring applications to high data rate real time industry and military applications. Energy efficiency and reliability are the two major design issues which should be handled efficiently at all the layers of communication protocol stack, due to resource constraint sensor nodes and erroneous nature of wireless channel respectively. Media access control (MAC) is the protocol which deals with the problem of packet collision due to simultaneous transmissions by more than one neighboring sensor nodes. Time Division Multiple Access based (TDMA-based) and contention-based are the two major types of MAC protocols used in WSNs. In general, the TDMA-based channel access mechanisms perform better than the contention-based channel access mechanisms, in terms of channel utilization, reliability and power consumption, specially for high data rate applications in wireless sensor networks (WSNs). TDMA-based channel access employs a predefined schedule so that the nodes can transmit at their allotted time slots. Based on the frequency of scheduling requirement, the existing distributed TDMA-scheduling techniques can be classified as either static or dynamic. The primary purpose of static TDMA-scheduling algorithms is to improve the channel utilization by generating a schedule of smaller length. But, they usually take longer time to generate such a schedule, and hence, are not suitable for WSNs, in which the network topology changes dynamically. On the other hand, dynamic TDMA-scheduling algorithms generate a schedule quickly, but they are not efficient in terms of generated schedule length. We suggest a new approach to TDMA-scheduling for WSNs, that can bridge the gap between these two extreme types of TDMA-scheduling techniques, by providing the flexibility to trade-off between the schedule length and the time required to generate the schedule, as per the requirements of the underlying applications and channel conditions. The suggested TDMA-scheduling works in two phases. In the first phase, we generate a valid TDMA schedule quickly, which need not have to be very efficient in terms of schedule length. In the second phase, we iteratively reduce the schedule length in a manner, such that the process of schedule length reduction can be terminated after the execution of an arbitrary number of iterations, and still be left with a valid schedule. This step provides the flexibility to trade-off the schedule length with the time required to generate the schedule. In the first phase of above TDMA-scheduling approach, we propose two randomized, distributed and parallel TDMA-scheduling algorithms viz., Distributed TDMA Slot Scheduling (DTSS) and Randomized and Distributed TDMA (RD-TDMA) scheduling algorithm. Both the algorithms are based on graph coloring approach, which generate a TDMA schedule quickly with a fixed schedule length ( Colouring), where is the maximum degree of any node in the graph to be colored. The two algorithms differ in the channel access mechanism used by them to transmit control messages, and in the generated schedule for different modes of communication, i.e., unicast, multicast and broadcast. The novelty of the proposed algorithms lies in the methods, by which an uncolored node detects that the slot picked by it is different from the slots picked by all the neighboring nodes, and the selection of probabilities with which the available slots can be picked up. Furthermore, to achieve faster convergence we introduce the idea of dynamic slot-probability update as per which the nodes update their slot-probability by considering the current slot-probability of their neighboring nodes. Under the second phase of the proposed TDMA-scheduling approach, we provide two randomized and distributed schedule compaction algorithms, viz., Distributed Schedule Compaction (DSC) and Distributed Schedule Length Reduction (DSLR) algorithm, as the mechanism to trade-off the scheduling time with the generated schedule length. These algorithms start with a valid TDMA schedule and progressively compress it in each round of execution. Additionally, Furthermore, the execution of these algorithms can be stopped after an arbitrary number of rounds as per the requirements of underlying applications. Even though TDMA-based MAC protocols avoid packet loss due to collision, due to erroneous nature of wireless medium, they alone are not sufficient to ensure the reliable transmission in WSNs. Automatic Repeat reQuest (ARQ) is the technique commonly used to provide error control for unicast data transmission. Unfortunately, ARQ mechanisms cannot be used for reliable multicast/broadcast transmission in WSNs. To solve this issue, we propose a virtual token-based channel access and feedback protocol (VTCAF) for link level reliable multicasting in single-hop wireless networks. The VTCAF protocol introduces a virtual (implicit) token passing mechanism based on carrier sensing to avoid the collision between feedback messages. The delay performance is improved in VTCAF protocol by reducing the number of feedback messages. Besides, the VTCAF protocol is parametric in nature and can easily trade-off reliability with the delay as per the requirements of the underlying applications. Finally, by integrating all the works, viz., TDMA-scheduling algorithms (DTSS/RD-TDMA), schedule compaction algorithms and link layer feedback mechanism for reliable multicast/ broadcast, we propose a TDMA-based energy aware and reliable MAC protocol, named TEA-MAC for multi-hop WSNs. Similar to VTCAF, TEA-MAC protocol uses the combination of ACK-based and NACK-based approaches to ensure reliable communication. But, instead of using virtual token-based channel access, it uses contention-based channel access for NACK transmission. All the algorithms and protocols proposed in this thesis are distributed, parallel and fault tolerant against packet losses to support scalability, faster execution and robustness respectively. The simulations have been performed using Castalia network simulator to evaluate the performance of proposed algorithms/protocols and also to compare their performance with the existing algorithms/protocols. We have also performed theoretical analysis of these algorithms/protocols to evaluate their performance. Additionally, we have shown the correctness of proposed algorithms/protocols by providing the necessary proofs, whenever it was required. The simulation results together with theoretical analysis show that, in addition to the advantage of trading the runtime with schedule length, the proposed TDMA scheduling approach achieves better runtime and schedule length performance than existing algorithms. Additionally, the TEA-MAC protocol is able to considerably improve the reliability and delay performance of multicast communication in WSNs.

The master thesis deals with G.fast and G.mgfast transmission technologies, including their parameters. The work deals with the principle of vector DMT modulation and the possibility of time duplex TDD and full-duplex FDX in two-way communication used in these technologies. The following is a description of the line using the KHM model, which is suitable for simulations in the transmission band using G.fast and G.mgfast technologies. Subsequently, the disturbing effects of crosstalk at the near end of NEXT and the far end of FEXT and their elimination with these technologies are discussing. Part of the work explains supporting calculations to determine the SNR and bit allocation to calculate the baud rate. The work describes the methods of compensation of crosstalk FEXT and NEXT, which affect the resulting baud rate. The work also includes an application for simulation of transmission speed as a function of distance for G.fast and G.mgfast technologies, allowing changing input parameters and adjusting the transmission bandwidth based on G.9700 and G.9701 standards. Also, in work, an application is created to display the compensation of the influence of the transmitted signal crosstalk FEXT and NEXT, which allow the import of measured crosstalk between individual participants. The issue of influencing crosstalk for accurate measurements in the laboratory is also discussing. An application in the MATLAB environment is creating to display the measured characteristics.

[ES] La constante necesidad de un mayor rendimiento para cumplir con la gran demanda de potencia de cómputo de las nuevas aplicaciones, (ej. sistemas de conducción autónoma), obliga a la industria a apostar por la tecnología basada en Sistemas en Chip con Procesadores Multinúcleo (MPSoCs) en sus sistemas embebidos de seguridad-crítica. Los sistemas MPSoCs generalmente incluyen una red en el chip (NoC) para interconectar los núcleos de procesamiento entre ellos, con la memoria y con el resto de recursos compartidos. Desafortunadamente, el uso de las NoCs dificulta alcanzar la predecibilidad en el tiempo, ya que pueden aparecer conflictos en muchos puntos y de forma distribuida a nivel de red. Para afrontar este problema, en esta tesis se propone un nuevo paradigma de diseño para NoCs de tiempo real donde los conflictos en la red son eliminados por diseño. Este nuevo paradigma parte del Grafo de Dependencia de Canales (CDG) para evitar los conflictos de red de forma determinista. Nuestra solución es capaz de inyectar mensajes de forma natural usando un periodo TDM igual al límite teórico óptimo sin la necesidad de usar un proceso offline exigente computacionalmente. La red se ha integrado en un sistema multinúcleo basado en tiles y adaptado a su jerarquía de memoria. Como segunda contribución principal, proponemos un nuevo planificador dinámico y distribuido capaz de alcanzar un rendimiento pico muy cercanos a las NoC basadas en un diseño wormhole sin comprometer sus garantías de tiempo real. El planificador se basa en nuestro diseño de red para explotar sus propiedades clave. Los resultados de nuestra NoC muestran que nuestro diseño garantiza la predecibilidad en el tiempo evitando interferencias en la red entre múltiples aplicaciones ejecutándose concurrentemente. La red siempre garantiza el rendimiento y también mejora el rendimiento respecto al de las redes wormhole en una red 4 x 4 en un factor de 3,7x cuando se inyecta trafico para generar interferencias. En una red 8 x 8 las diferencias son incluso mayores. Además, la red obtiene un ahorro de área total del 10,79% frente a una implementación básica de una red wormhole. El planificador propuesto alcanza una mejora de rendimiento de 6,9x y 14,4x frente la versión básica de la red DCFNoC para redes en forma de malla de 16 y 64 nodos, respectivamente. Cuando lo comparamos frente a un conmutador estándar wormhole se preserva un rendimiento de red del 95% al mismo tiempo que preserva la estricta predecibilidad en el tiempo. Este logro abre la puerta a nuevos diseños de NoCs de alto rendimiento con predecibilidad en el tiempo. Como contribución final, construimos una taxonomía de NoCs basadas en TDM con propiedades de tiempo real. Con esta taxonomía realizamos un análisis exhaustivo para estudiar y comparar desde tiempos de respuesta, a implementaciones con bajo coste, pasando por soluciones de compromiso para diseños de NoCs de tiempo real. Como resultado, obtenemos nuevos diseños de NoCs basadas en TDM. / [CA] La constant necessitat d'un major rendiment per a complir amb la gran demanda de potència de còmput de les noves aplicacions, (ex. sistemes de conducció autònoma), obliga la indústria a apostar per la tecnologia basada en Sistemes en Xip amb Processadors Multinucli (MPSoCs) en els seus sistemes embeguts de seguretat-crítica. Els sistemes MPSoCs generalment inclouen una xarxa en el xip (NoC) per a interconnectar els nuclis de processament entre ells, amb la memòria i amb la resta de recursos compartits. Desafortunadament, l'ús de les NoCs dificulta aconseguir la predictibilitat en el temps, ja que poden aparéixer conflictes en molts punts i de forma distribuïda a nivell de xarxa. Per a afrontar aquest problema, en aquesta tesi es proposa un nou paradigma de disseny per a NoCs de temps real on els conflictes en la xarxa són eliminats per disseny. Aquest nou paradigma parteix del Graf de Dependència de Canals (CDG) per a evitar els conflictes de xarxa de manera determinista. La nostra solució és capaç d'injectar missatges de mra natural fent ús d'un període TDM igual al límit teòric òptim sense la necessitat de fer ús d'un procés offline exigent computacionalment. La xarxa s'ha integrat en un sistema multinucli basat en tiles i adaptat a la seua jerarquia de memòria. Com a segona contribució principal, proposem un nou planificador dinàmic i distribuït capaç d'aconseguir un rendiment pic molt pròxims a les NoC basades en un disseny wormhole sense comprometre les seues garanties de temps real. El planificador es basa en el nostre disseny de xarxa per a explotar les seues propietats clau. Els resultats de la nostra NoC mostren que el nostre disseny garanteix la predictibilitat en el temps evitant interferències en la xarxa entre múltiples aplicacions executant-se concurrentment. La xarxa sempre garanteix el rendiment i també millora el rendiment respecte al de les xarxes wormhole en una xarxa 4 x 4 en un factor de 3,7x quan s'injecta trafic per a generar interferències. En una xarxa 8 x 8 les diferències són fins i tot majors. A més, la xarxa obté un estalvi d'àrea total del 10,79% front una implementació bàsica d'una xarxa wormhole. El planificador proposat aconsegueix una millora de rendiment de 6,9x i 14,4x front la versió bàsica de la xarxa DCFNoC per a xarxes en forma de malla de 16 i 64 nodes, respectivament. Quan ho comparem amb un commutador estàndard wormhole es preserva un rendiment de xarxa del 95% al mateix temps que preserva la estricta predictibilitat en el temps. Aquest assoliment obri la porta a nous dissenys de NoCs d'alt rendiment amb predictibilitat en el temps. Com a contribució final, construïm una taxonomia de NoCs basades en TDM amb propietats de temps real. Amb aquesta taxonomia realitzem una anàlisi exhaustiu per a estudiar i comparar des de temps de resposta, a implementacions amb baix cost, passant per solucions de compromís per a dissenys de NoCs de temps real. Com a resultat, obtenim nous dissenys de NoCs basades en TDM. / [EN] The ever need for higher performance to cope with the high computational power demands of new applications (e.g autonomous driving systems), forces industry to support technology based on multi-processors system on chip (MPSoCs) in their safety-critical embedded systems. MPSoCs usually include a network-on-chip (NoC) to interconnect the cores between them and, with memory and the rest of shared resources. Unfortunately, the inclusion of NoCs difficults achieving time predictability as network-level conflicts may occur in many points in a distributed manner. To overcome this problem, this thesis proposes a new time-predictable NoC design paradigm where conflicts within the network are eliminated by design. This new paradigm builds on top of the Channel Dependency Graph (CDG) in order to deterministically avoid network conflicts. Our solution is able to naturally inject messages using a TDM period equal to the optimal theoretical bound without the need of using a computationally demanding offline process. The network is integrated in a tile-based manycore system and adapted to its memory hierarchy. As a second main contribution, we propose a novel distributed dynamic scheduler that is able to achieve peak performance close to a wormhole-based NoC design without compromising its real-time guarantees. The scheduler builds on top of our NoC design to exploit its key properties. The results of our NoC show that our design guarantees time predictability avoiding network interference among multiple running applications. The network always guarantees performance and also improves wormhole performance in a 4 x 4 setting by a factor of 3.7x when interference traffic is injected. For a 8 x 8 network differences are even larger. In addition, the network obtains a total area saving of 10.79% over a standard wormhole implementation. The proposed scheduler achieves an overall throughput improvement of 6.9x and 14.4x over a baseline conflict-free NoC for 16 and 64-node meshes, respectively. When compared against a standard wormhole router 95% of its network throughput is preserved while strict timing predictability is kept. This achievement opens the door to new high performance time predictable NoC designs. As a final contribution, we build a taxonomy of TDM-based NoCs with real-time properties. With this taxonomy we perform a comprehensive analysis to study and compare from response time specific, to low resource implementation cost, through trade-off solutions for real-time NoCs designs. As a result, we derive new TDM-based NoC designs. / Picornell Sanjuan, T. (2021). Conflict-Free Networks on Chip for Real Time Systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/177347 / TESIS