Teses / dissertações sobre o tema "Ultra-reliable"

Abstract. Internet of things is in progress to build the smart society, and wireless networks are critical enablers for many of its use cases. In this thesis, we present some of the vital concept of diversity and multi-connectivity to achieve ultra-reliability and low latency for machine type wireless communication networks. Diversity is one of the critical factors to deal with fading channel impairments, which in term is a crucial factor to achieve targeted outage probabilities and try to reach out such requirement of five 9’s as defined by some standardization bodies. We evaluate an interference-limited network composed of multiple remote radio heads connected to the user equipment. Some of those links are allowed to cooperate, thus reducing interference, or to perform more elaborated strategies such as selection combining or maximal ratio combining. Therefore, we derive their respective closed-form analytical solutions for respective outage probabilities. We provide extensive numerical analysis and discuss the gains of cooperation and multi-connectivity enabled to be a centralized radio access network.

The 5G Core Network architecture is modeled to include instruments that can establish networks built on the same physical infrastructure but serve different service categories for communication types with varying characteristics. Relying on virtualization and cloud technologies, these instruments make the 5G system different from previous mobile communication systems, change the user profile, and allow new business models to be included in the system. The subject of this thesis includes the study of Ultra-reliable low latency communication, which is one of the fundamental service categories defined for the 5G system, and the analysis of the techniques presented in 3GPP’s Release 16, which enhance the service parameters by modifying the core network. In the theoretical part, the 5G system and URLLC are introduced with a particular focus on the user plane on the core network. In the implementation part, redundant transmission support on the N3 interface, one of the techniques presented in the technical specification, is modeled using open source software tools (Open5GS and UERANSIM) and network virtualization instruments. As a result of the tests and measurements performed on the model, it was observed that the implemented technique enhanced the system's reliability.

To enable wireless control of factories, such that sensor measurements can be sent wirelessly to an actuator, the probability to receive data correctly must be very high and the time it takes to the deliver the data from the sensor to the actuator must be very low. Earlier, these requirements have only been met by cables, but in the fifth generation mobile network this is one of the imagined use cases and work is undergoing to create a system capable of wireless control of factories. One of the problems in this scenario is when all data in a packet cannot be sent in one transmission while ensuring the very high probability of reception of the transmission. This thesis studies this problem in detail by proposing methods to cope with the problem and evaluating these methods in a simulator. The thesis shows that splitting the data into multiple segments and transmitting each at an even higher probability of reception is a good candidate, especially when there is time for a retransmission. When there is only one transmission available, a better candidate is to send the same packet twice. Even if the first packet cannot achieve the very high probability of reception, the combination of the first and second packet might be able to.
För att möjliggöra trådlös kontroll av fabriker, till exempel trådlös sändning av data uppmätt av en sensor till ett ställdon som agerar på den emottagna signalen, så måste sannolikheten att ta emot datan korrekt vara väldigt hög och tiden det tar att leverera data från sensorn till ställdonet vara mycket kort. Tidigare har endast kablar klarat av dessa krav men i den femte generationens mobila nätverk är trådlös kontroll av fabriker ett av användningsområdena och arbete pågår för att skapa ett system som klarar av det. Ett av problemen i detta användningsområde är när all data i ett paket inte kan skickas i en sändning och klara av den väldigt höga sannolikheten för mottagning. Denna uppsats studerar detta problem i detalj och föreslår metoder för att hantera problemet samt utvärderar dessa metoder i en simulator. Uppsatsen visar att delning av ett paket i flera segment och sändning av varje segment med en ännu högre sannolikhet för mottagning är en bra kandidat, speciellt när det finns tid för en omsändning. När det endast finns tid för en sändning verkar det bättre att skicka samma paket två gånger. Även om det första paketet inte kan uppnå den höga sannolikheten för mottagning så kan kanske kombinationen av det första och andra paketet göra det.

Increasing demand for implementing highly-miniaturized battery-powered ultra-low-cost systems (e.g., below 1 USD) in emerging applications such as body, urban life and environment monitoring, etc., has introduced many challenges in the chip design. Such applications require high performance occasionally, but very little energy consumption during most of the time in order to extend battery lifetime. In addition, they require real-time guarantees. The most suitable technological solution for those devices consists of using hybrid processors able to operate at: (i) high voltage to provide high performance and (ii) near-/sub-threshold (NST) voltage to provide ultra-low energy consumption. However, the most efficient SRAM memories for each voltage level differ and it is mandatory trading off different SRAM designs, especially in cache memories, which occupy most of the processor¿s area. In this Thesis, we analyze the performance/power tradeoffs involved in the design of SRAM L1 caches for reliable hybrid high and NST Vcc operation from a microarchitectural perspective. We develop new, simple, single-Vcc domain hybrid cache architectures and data management mechanisms that satisfy all stringent needs of our target market. Proposed solutions are shown to have high energy efficiency with negligible impact on average performance while maintaining strong performance guarantees as required for our target market.

L'émergence de nouveaux cas et d’applications tels que la réalité virtuelle/augmentée, l'automatisation industrielle, les véhicules autonomes, etc. en 5G fait définir au Third Generation Partnership Project (3GPP) Ultra-reliable low-latency communications (URLLC) comme un des trois services. Pour soutenir URLLC avec des exigences strictes de la fiabilité et de la latence, 3GPP Release 15 et 16 ont standardisé des fonctionnalités d’URLLC dans le spectre sous licence. Release 17 en cours agrandit des fonctionnalités d’URLLC au spectre sans licence pour cibler des nouveaux cas dans des scénarios industriels. Dans la première partie de cette thèse du Chapitre 2 au Chapitre 4, nous nous concentrons sur URLLC dans le spectre sous licence. La première étude est confrontée au problème de garantir le nombre des répétitions dans des uplink configured-grant (CG) ressources. Ensuite, nous étudions la collision entre une eMBB UL transmission d'un UE et une URLLC UL transmission d'un autre UE sur des CG ressources. Enfin, nous recherchons la DL transmission où le feedback de la DL semi-persistent scheduling transmission est abandonné à cause du conflit entre des DL/UL symboles. Dans la deuxième partie du Chapitre 5 au Chapitre 8, nous nous focalisons sur URLLC dans le spectre sans licence. Dans le spectre sans licence, un appareil demande d'accéder au canal en utilisant load based equipment (LBE) ou frame based equipment (FBE). L’incertitude d’acquérir un canal par LBE ou FBE pourrait empêcher la URLLC transmission d’atteindre l’exigence de la latence. Par conséquent, l'étude de l'impact de LBE ou FBE sur la URLLC transmission et des améliorations de LBE et de FBE sont nécessaires
The advent of new use cases and new applications such as augmented/virtual reality, industrial automation, autonomous vehicles, etc. in 5G has made the Third Generation Partnership Project (3GPP) specify Ultra-reliable low-latency communications (URLLC) as one of the service categories. To support URLLC with the strict requirements of reliability and latency, 3GPP Release 15 and Release 16 have specified the URLLC features in licensed spectrum. The ongoing 3GPP Release 17 extends the URLLC features to unlicensed spectrum to target the new use cases in the industrial scenario. In the first part of the thesis from Chapter 2 to Chapter 4, we focus on the URLLC in licensed spectrum. The first study deals with the problem of ensuring the configured number of uplink (UL) configured-grant (CG) repetitions of a transport block. Secondly, we study the collisions of an eMBB UL transmission of a user equipment (UE) and an URLLC UL transmission of another UE on the CG resources. Thirdly, the focus of this study is the downlink (DL) transmission where the feedback of the DL semi-persistent scheduling transmission is dropped due to the conflict of the DL/UL symbols. In the second part from Chapter 5 to Chapter 8, we focus on URLLC operation in unlicensed spectrum. In unlicensed spectrum, a 5G device is required to access to a channel by using load based equipment (LBE) or frame based equipment (FBE). The uncertainty of obtaining channel access through LBE or FBE can impede the achievement of the URLLC latency requirements. Therefore, the study of impact of LBE and FBE on URLLC transmission and the enhancements of LBE and FBE are needed

This dissertation is directed towards improving the performance of 5G Wireless Fronthaul Networks and Wireless Sensor Networks, as measured by reliability, fault recovery time, energy consumption, efficiency, and security of transmissions, beyond what is achievable with conventional error control technology. To achieve these ambitious goals, the research is focused on novel applications of networking techniques, such as Diversity Coding, where a feedforward network design uses forward error control across spatially diverse paths to enable reliable wireless networking with minimal delay, in a wide variety of application scenarios. These applications include Cloud-Radio Access Networks (C-RANs), which is an emerging 5G wireless network architecture, where Remote Radio Heads (RRHs) are connected to the centralized Baseband Unit (BBU) via fronthaul networks, to enable near-instantaneous recovery from link/node failures. In addition, the ability of Diversity Coding to recover from multiple simultaneous link failures is demonstrated in many network scenarios. Furthermore, the ability of Diversity Coding to enable significantly simpler and thus lower-cost routing than other types of restoration techniques is demonstrated. Achieving high throughput for broadcasting/multicasting applications, with the required level of reliability is critical for the efficient operation of 5G wireless infrastructure networks. To improve the performance of C-RAN networks, a novel technology, Diversity and Network Coding (DC-NC), which synergistically combines Diversity Coding and Network Coding, is introduced. Application of DC-NC to several 5G fronthaul networks, enables these networks to provide high throughput and near-instant recovery in the presence of link and node failures. Also, the application of DC-NC coding to enhance the performance of downlink Joint Transmission-Coordinated Multi Point (JT-CoMP) in 5G wireless fronthaul C-RANs is demonstrated. In all these scenarios, it is shown that DC-NC coding can provide efficient transmission and reduce the resource consumption in the network by about one-third for broadcasting/multicasting applications, while simultaneously enabling near-instantaneous latency in recovery from multiple link/node failures in fronthaul networks. In addition, it is shown by applying the DC-NC coding, the number of redundant links that uses to provide the required level of reliability, which is an important metric to evaluate any protection system, is reduced by about 30%-40% when compared to that of Diversity Coding. With the additional goal of further reducing of the recovery time from multiple link/node failures and maximizing the network reliability, DC-NC coding is further improved to be able to tolerate multiple, simultaneous link failures with less computational complexity and lower energy consumption. This is accomplished by modifying Triangular Network Coding (TNC) and synergistically combining TNC with Diversity Coding to create enhanced DC-NC (eDC-NC), that is applied to Fog computing-based Radio Access Networks (F-RAN) and Wireless Sensor Networks (WSN). Furthermore, it is demonstrated that the redundancy percentage for protecting against n link failures is inversely related to the number of source data streams, which illustrates the scalability of eDC-NC coding. Solutions to enable synchronized broadcasting are proposed for different situations. The ability of eDC-NC coding scheme to provide efficient and secure broadcasting for 5G wireless F-RAN fronthaul networks is also demonstrated. The security of the broadcasting data streams can be obtained more efficiently than standardized methods such as Secure Multicasting using Secret (Shared) Key Cryptography.

Abstract. In this thesis we evaluate the performance of several retransmission mechanisms with ultra-reliability constraints. First, we show that achieving a very low packet outage probability by using an open loop setup is a difficult task. Thus, we resort to retransmission schemes as a solution for achieving the required low outage probabilities for ultra reliable communication. We analyze three retransmission protocols, namely Type-1 Automatic Repeat Request (ARQ), Chase Combining Hybrid ARQ (CC-HARQ) and Incremental Redundancy (IR) HARQ. For these protocols, we develop optimal power allocation algorithms that would allow us to reach any outage probability target in the finite block-length regime. We formulate the power allocation problem as minimization of the average transmitted power under a given outage probability and maximum transmit power constraint. By utilizing the Karush-Kuhn-Tucker (KKT) conditions, we solve the optimal power allocation problem and provide closed form solutions. Next, we analyze the effect of implementing these protocols on the throughput of the system. We show that by using the proposed power allocation scheme we can minimize the loss of throughput that is caused from the retransmissions. Furthermore, we analyze the effect of the feedback delay length in our protocols.Optimaalista tehoallokointia toisto- ja rinnakkaiskoodaukseen käyttävä erittäin luotettava tiedonsiirto äärellisillä lohkonpituuksilla. Tiivistelmä. Tässä työssä arvioidaan usean uudelleenlähetysmenetelmän suorituskykyä erittäin luotettavan tietoliikenteen järjestelmäoletuksin. Aluksi osoitetaan, että hyvin alhaisen pakettilähetysten katkostodennäköisyyden saavuttaminen avoimen silmukan menetelmillä on haastava tehtävä. Niinpä työssä turvaudutaan uudelleenlähetyspohjaisiin ratkaisuihin, joilla on mahdollista päästä suuren luotettavuuden edellyttämiin hyvin alhaisiin katkostodennäköisyyksiin. Työssä analysoidaan kolmea uudelleenlähetysprotokollaa, nimittäin tyypin 1 automaattista uudelleen lähetystä (ARQ), Chase Combining -tyyppistä hybridi-ARQ -protokollaa (CC-HARQ) ja redundanssia lisäävää HARQ-protokollaa (IR-HARQ). Näille protokollille kehitetään optimaalisia tehon allokointialgoritmeja, joiden avulla päästään halutulle katkostodennäköisyystasolle äärellisillä lohkonpituuksilla. Tehon allokointiongelma muotoillaan keskimääräisen lähetystehon minimointiongelmaksi toteuttaen halutun katkostodennäköisyyden ja maksimilähetystehorajoituksen. Käyttämällä Karush-Kuhn-Tucker (KKT) -ehtoja ratkaistaan optimaalinen tehoallokointiongelma ja esitetään ratkaisut suljetussa muodossa. Seuraavaksi analysoidaan näiden protokollien järjestelmätason toteutusta läpäisykykytarkastelujen avulla. Niillä osoitetaan, että ehdotetulla tehon allokointimenetelmällä voidaan minimoida uudelleen lähetyksistä aiheutuvia suorituskykyhäviöitä. Lisäksi työssä tutkitaan takaisinkytkentäviiveen vaikutusta esitettyihin protokolliin.

L’IRM quantitative recouvre l’ensemble des méthodes permettant de mesurer des paramètres physiques accessibles en Résonance Magnétique Nucléaire. Elle offre un bénéfice par rapport à l’imagerie en pondération classiquement utilisée, notamment pour la détection, la caractérisation physiopathologique mais aussi pour le suivi thérapeutique des pathologies. Malgré ce potentiel avéré connu de longue date, ces méthodes restent peu utilisées dans la routine clinique. La raison principale est la longueur des acquisitions par rapport à l’approche classique. Les paramètres physiques que nous souhaitons étudier plus particulièrement sont le temps de relaxation longitudinal (T₁), transversal (T₂), le coefficient de diffusion apparent (ADC), et la densité de protons (DP). Malgré la possibilité d’atteindre une meilleure qualité d’images, ces cartographies in vivo sont quasiment inexistantes dans la littérature au-delà de 3T car leur implémentation nécessite de surmonter un certain nombre de limites spécifiques aux IRM ultra-haut champs (UHF). Au travers de ce projet de thèse, une méthode d’imagerie quantitative basée sur les états de configurations (QuICS) a été implémentée, pour déterminer ces paramètres quantitatifs de façon simultanée sous fortes contraintes propres aux UHF. L’approche a été optimisée dans le but d’obtenir des cartographies fiables et rapides. Le potentiel de la méthode a été démontré dans un premier temps in vitro sur un noyau tel que le sodium démontrant des propriétés complexes à cartographier. Puis dans un second temps, des acquisitions ont été réalisées sur proton, in vivo, en un temps d’acquisition compatible avec une utilisation en routine clinique à 7T. L’application d’une telle méthode d’IRM quantitative à UHF sur des populations permettra d’ouvrir de nouvelles voies d’études pour le futur
Quantitative MRI refers to methods able to measure different physical parameters accessible in Nuclear Magnetic Resonance. It offers benefits compared to weighting imaging commonly used, for the detection, the pathophysiological characterization but also for the therapeutic follow-up of pathologies for example. Despite this long-established potential, these methods remain little used in clinical routine. The main reason is the long acquisition time compared to the classical approach. The physical parameters that we will study more particularly are the longitudinal (T₁), transverse (T₂) relaxation time, the apparent diffusion coefficient (ADC), and the proton density (DP). Despite the possibility to achieve a better image quality, these in vivo mappings are virtually non-existent in the literature beyond 3T because their implementation requires overcom-ing a number of specific ultra-high-field (UHF) MRI limits. Through this thesis project, a Quantitative Imaging method using Configuration States (QuICS) was implemented under strong UHF constraints, to determine these parameters simultaneously. The technique has been optimized to obtain fast and reliable maps. The potential of the method was first demon-strated in vitro on a nucleus such as sodium, exhibiting complex properties. As a second step, acquisitions were performed in proton, in vivo, in an clinically-relevant acquisition time, compatible with a routine use at 7T for population imaging. The application of such a method of quantitative MRI to UHF will open new research possibilities for the future

Fifth Generation (5G) networks are expected to support emerging applications with diverse quality of service (QoS) requirements, such as reliability, latency, and age-of-information. In conventional wireless networks, orthogonal resources are allocated to different transmitters to guarantee QoS performance. As the density of networks or devices increases, we need to increase the frequency reuse factor. Thus, interference becomes one of the bottlenecks for ensuring the QoS requirements of a large number of devices with limited time-frequency resources. This thesis presents novel methods for improving QoS performance in interference-limited networks. Specifically, we consider three typical scenarios: Ultra-reliable and Low latency communications (URLLC), time-critical applications, and multi-tenant communications. In 5G networks, URLLC is one of the most challenging services with high reliability and low latency requirements. We define a new QoS metric, QoS violation probability, to measure the percentage of users without QoS guarantee. We propose a random packet repetition scheme that randomizes the interference power. The randomization is used to obtain diversity within the channel coherence time. The variation of interference can be exploited to reduce the QoS violation probability in interference-limited networks. Then, we optimize the number of reserved slots and the number of repetitions for each packet to minimize the QoS violation probability. We build a cascaded Random Edge Graph Neural Network (REGNN) to represent the repetition scheme and develop a model-free unsupervised learning method to train it. We analyze the QoS violation probability using stochastic geometry in a symmetric scenario and apply a model-based Exhaustive Search (ES) method to find the optimal solution. Simulation results show that in the symmetric scenario, the QoS violation probabilities achieved by the model-free learning method and the model-based ES method are nearly the same. In more general scenarios, the cascaded REGNN generalizes very well to wireless networks with different scales, network topologies, cell densities, and frequency reuse factors. It outperforms the model-based ES method in the presence of model mismatch. For time-critical applications, we investigate the timely updates of short packets in interference-limited networks. Specifically, we minimize a performance metric, Age-of-Information (AoI), by optimizing the power control policy that is scalable to the number of wireless links. To find the optimal policy, we develop a deep reinforcement learning algorithm, graph-based deterministic policy gradient (GDPG). The actor and critic of the GDPG are represented by two types of graph neural networks (GNNs). We design two structures to implement the GDPG in a centralized and distributed manner. Simulation results show that when the number of wireless links in the testing stage is different from that in the training stage, the average AoI achieved by the GDPG is around $25\%$ lower than the WMMSE (weighted minimize mean square error) algorithm in a hexagonal cellular network and $50\%$ lower in a random network. The proposed methods are scalable to the number of wireless links in the network. With fine-tuning, our proposed two GDPG structures can be generalized well to networks with different densities and topologies. Finally, we consider a multi-tenant network scenario, where multiple vertical industries or operators (acting as tenants) run their network on a single base station (BS). A new duality concept is developed to allocate precoding weights and transmit power at the BS so that the minimum isolation level from interference between tenants is maximized. A real-time multi-antenna multi-tenant BS (MBS) prototype is built by using commercial-off-the-shelf (COTS) software-defined-radio (SDR) boards. The over-the-air experiments show MBS provides a higher minimum isolation level and network capacity than other known algorithms. The research on improving the QoS for different applications in 5G and beyond is developing rapidly. Possible future directions include 1) developing a more flexible transmission scheme that repeats the packet transmission in different resource blocks, 2) optimizing the peak AoI with a constraint on the tail probability, and 3) proposing a general solution for improving the QoS or other queue state information metrics in 5G interference-limited networks.

Les futurs réseaux mobiles promettent des opportunités sans précédent pour l'innovation et des cas d'utilisation disruptifs. L'engagement des réseaux 5G et au-delà à fournir des applications critiques nécessite un réseau polyvalent, évolutif, efficace et rentable, capable d'adapter son allocation de ressources pour répondre aux exigences de services hétérogènes. Pour relever ces défis, le découpage du réseau s'est imposé comme l'un des concepts fondamentaux proposés pour améliorer l'efficacité des réseaux mobiles 5G et leur conférer la plasticité requise. L'idée est de fournir des ressources à différentes industries verticales en construisant plusieurs réseaux logiques de bout en bout sur une infrastructure virtualisée partagée. Chaque "tranche de réseau" ainsi définie est personnalisée pour fournir un service spécifique en adaptant son architecture et ses technologies d'accès radio.Précisément, des applications telles que l'automatisation industrielle ou les communications entre véhicules imposent aux réseaux cellulaires des exigences strictes en matière de latence et de fiabilité. Étant donné que le réseau mobile actuel ne peut pas répondre à ces exigences, les communications ultra-fiables et à faible temps de latence constituent un sujet de recherche essentiel qui a suscité un élan considérable de la part du monde universitaire et des alliances industrielles. Pour répondre à ces exigences, l'utilisation de la multi-connectivité, c'est-à-dire l'exploitation simultanée de plusieurs liaisons radio comme voies de communication, est une approche prometteuse.L'objectif du présent manuscrit est d'étudier des techniques d'allocation de resources exploitant la couverture redondante des utilisateurs, garantie dans de nombreux scénarios 5G. Nous examinons d'abord l'évolution des réseaux mobiles et discutons des diverses considérations relatives à l'architecture de découpage du réseau et de son impact sur la conception des méthodes d'allocation des ressources. Nous utilisons ensuite les outils de la théorie des files d'attente pour modéliser un système dans lequel un ensemble d'utilisateurs URLLC sont connectés simultanément à deux stations de base ayant la même bande passante ; nous appelons ce scénario le cas homogène. Nous introduisons des politiques d'allocation appropriées et évaluons leurs performances respectives en évaluant leur fiabilité. Ensuite, nous étendons les résultats du cas homogène à un cadre plus général où les interfaces physiques gèrent des bandes passantes différentes, que nous appelons le cas hétérogène. Enfin, nous fusionnons les éléments ci-dessus pour valider le choix des schémas d'allocation des ressources en tenant compte de l'architecture déployée
Future mobile networks envision unprecedented innovation opportunities and disruptive use cases. As a matter of fact, the 5G and beyond networks' pledge to deliver mission-critical applications mandates a versatile, scalable, efficient, and cost-effective network capable of accommodating its resource allocation to meet the services' heterogeneous requirements. To face these challenges, network slicing has emerged as one of the fundamental concepts proposed to raise the 5G mobile networks' efficiency and provide the required plasticity. The idea is to provide resources for different vertical industries by building multiple end-to-end logical networks over a shared virtualized infrastructure. Each network slice is customized to deliver a specific service and adapts its architecture and radio access technologies.Precisely, applications such as industrial automation or vehicular communications pose stringent latency and reliability requirements on cellular networks. Given that the current mobile network cannot meet these requirements, ultra-reliable low-latency communications (URLLC) embodies a vital research topic that has gathered substantial momentum from academia and industrial alliances. To reach URLLC requirements, employing multi-connectivity (MC), i.e., exploiting multiple radio links as communication paths at once, is a promising approach.Therefore, the objective of the present manuscript is to investigate dynamic scheduling techniques, exploiting redundant coverage of users, guaranteed in numerous 5G radio access network scenarios. We first review the evolution of mobile networks and discuss various considerations for network slicing architecture and its impact on resource allocation design. Then, we use tools from queuing theory to model a system in which a set of URLLC users are connected simultaneously to two base stations having the same bandwidth; we refer to this scenario as the homogenous case. We introduce suitable scheduling policies and evaluate their respective performances by assessing their reliability. Next, we extend the homogenous case's results to a more general setting where the physical interfaces manage different bandwidths, referred to as the heterogeneous case. Finally, we merge the above elements to validate the choice of resource allocation schemes considering the deployed architecture

Le sujet de cette thèse porte sur les réseaux sans fil véhiculaires et, plus précisément, sur l’utilisation de la transmission radio et de la communication par la lumière (VLC) pour améliorer la sécurité des véhicules. La thèse est motivée par les problèmes de fiabilité et d’évolutivité de la norme IEEE 802.11p. L’idée est d’évoluer vers de nouvelles techniques, et d’associer la transmission radio à la communication en VLC pour permettre une communication hybride. La première partie de la thèse concerne la mise au point de techniques d’accès radio à faible latence dans les réseaux véhiculaires. L’idée de la solution est de mélanger les techniques TDMA classiques et des mécanismes avancés de protocoles à compétition utilisant des signalements actifs. Cette solution a été spécifié, évalué et comparé à d’autres solutions de la littérature. Nous avons également introduit dans cette partie un schéma d’accès spécial pour les paquets d’urgence de haute priorité, tout en garantissant un accès fiable et à faible latence. La seconde partie de la thèse concerne la communication par lumière visible pour le contrôle de peloton. Pour cela, nous avons proposé et développé un algorithme qui sélectionne la communication radio, proposée dans la première partie, et la communication par lumière visible en se basant sur l’état du canal radio et d’alignement du peloton
The subject of this thesis is vehicle wireless networks and, more specifically, the use of radio transmission and Visible Light Communication (VLC) to improve vehicle safety. The thesis is motivated by the reliability and scalability issues of the IEEE 802.11p standard. The idea is to move towards new techniques, especially in future 803.11bd standards, and to combine radio transmission with VLC to enable hybrid communication. The first part of the thesis concerns the development of a low latency radio access technique in vehicular networks. The idea of the solution is to combine classical TDMA techniques and advanced mechanisms of competitive protocols using active signaling. This solution has been specified, evaluated, and compared to other solutions from literature. This part also introduces a special access scheme for high priority emergency packets, while ensuring reliable and low latency access. The second part of the thesis concerns visible light communication for platoon control. The idea is to develop an algorithm to select the radio communication, proposed in the first part, and visible light communication based on the radio channel conditions and platoon alignment

Les systèmes de communication sans fil à venir vont faire un usage intensif des transmissions de paquets courts. La norme 5G émergente en est un exemple parfait, pour lequel deux des trois principaux cas d'utilisation, les communications massives de type machine (mMTC) et les communications ultra fiables à faible latence (URLLC), reposent intrinsèquement sur des paquets courts. Un autre exemple est fourni par les récents réseaux d'accès de faible puissance (LPWAN) tels que Sigfox, LoRa, etc. et conçus pour prendre en charge l'IoT. L'utilisation de paquets courts au niveau de la couche physique peut modifier considérablement la conception des systèmes de communication numériques. En particulier, avec une longueur de bloc courte, la surcharge de l'en-tête ne peut plus être considérée comme négligeable. Plus important encore, les résultats asymptotiques de la théorie de l'information, qui ont été un guide essentiel et un moteur essentiel de la conception de systèmes de communication en constante amélioration jusqu'à présent, ne sont plus valables dans ce régime. Comment alors assurer une communication fiable sans augmenter la longueur du code puisque ce dernier n'est plus une option? Par extension et plus fondamentalement, comment concevoir la couche physique de paquets courts pour assurer des performances optimales avec l'utilisation la plus efficace possible des ressources disponibles? L'objectif de cette thèse est de revoir les techniques de conception de la couche physique pour la communication par paquets courts et de proposer de nouvelles directives de conception tirant parti des derniers résultats en matière de codage de canal dans le régime de longueur de bloc finie
Upcoming wireless communication systems are expected to make intensive use of short packet transmission. An epitome is the emerging 5G standard, for which two out of the three principal use cases, massive Machine Type Communications (mMTC) and Ultra Reliable Low Latency Communications (URLLC), are intrinsically based on short packets. Another example is provided by the recent Low-Power Wide Area Networks (LPWAN) designed to support the IoT such as Sigfox, LoRa, etc.The use of short packets at the physical layer may substantially change the way digital communication systems are designed. In particular, at short block length, header overhead may no longer be considered negligible. More importantly, asymptotic results from information theory which have been a central guide and a key driver to the design of ever-improving communication systems so far no longer hold in this regime. How, then, to ensure reliable communication without increasing the code length since the latter is no longer an option ? By extension and more fundamentally, how to design the physical layer of short packets to ensure optimal performance with the most efficient use of available resources at hand ? The focus of this PhD thesis is to revisit physical layer design for short-packet communication and to propose new design guidelines leveraging the latest results on channel coding in the finite blocklength regime

Low-power wireless technology is a part and parcel of our daily life, shaping the way in which we behave, interact, and more generally live. The ubiquity of cheap, tiny, battery-powered devices augmented with sensing, actuation, and wireless communication capabilities has given rise to a ``smart" society, where people, machines, and objects are seamlessly interconnected, among themselves and with the environment. Behind the scenes, low-power wireless protocols are what enables and rules all interactions, organising these embedded devices into wireless networks, and orchestrating their communications. The recent years have witnessed a persistent increase in the pervasiveness and impact of low-power wireless. After having spawned a wide spectrum of powerful applications in the consumer domain, low-power wireless solutions are extending their influence over the industrial context, where their adoption as part of feedback control loops is envisioned to revolutionise the production process, paving the way for the Fourth Industrial Revolution. However, as the scale and relevance of low-power wireless systems continue to grow, so do the challenges posed to the communication substrates, required to satisfy ever more strict requirements in terms of reliability, responsiveness, and energy consumption. Harmonising these conflicting demands is far beyond what is enabled by current network stacks and control architectures; the need to timely bridge this gap has spurred a new wave of interest in low-power wireless networking, and directly motivated our work. In this thesis, we take on this challenge with a main conceptual and technical tool: concurrent transmissions (CTX), a technique that, by enforcing nodes to transmit concurrently, has been shown to unlock unprecedented fast, reliable, and energy efficient multi-hop communications in low-power wireless networks, opening new opportunities for protocol design. We first direct our research endeavour towards industrial applications, focusing on the popular IEEE 802.15.4 narrowband PHY layer, and advance the state of the art along two different directions: interference resilience and aperiodic wireless control. We tackle radio-frequency noise by extensively analysing, for the first time, the dependability of CTX under different types, intensities, and distributions of reproducible interference patterns, and by devising techniques to push it further. Specifically, we concentrate on CRYSTAL, a recently proposed communication protocol that relies on CTX to rapidly and dependably collect aperiodic traffic. By integrating channel hopping and noise detection in the protocol operation, we provide a novel communication stack capable of supporting aperiodic transmissions with near-perfect reliability and a per-mille radio duty cycle despite harsh external interference. These results lay the ground towards the exploitation of CTX for aperiodic wireless control; we explore this research direction by co-designing the Wireless Control Bus (WCB), our second contribution. WCB is a clean-slate CTX-based communication stack tailored to event-triggered control (ETC), an aperiodic control strategy holding the capability to significantly improve the efficiency of wireless control systems, but whose real-world impact has been hampered by the lack of appropriate networking support. Operating in conjunction with ETC, WCB timely and dynamically adapts the network operation to the control demands, unlocking an order-of-magnitude reduction in energy costs w.r.t. traditional periodic approaches while retaining the same control performance, therefore unleashing and concretely demonstrating the true ETC potential for the first time. Nevertheless, low-power wireless communications are rapidly evolving, and new radios striking novel trade-offs are emerging. Among these, in the second part of the thesis we focus on ultra-wideband (UWB). By providing hitherto missing networking primitives for multi-hop dissemination and collection over UWB, we shed light on the communication potentialities opened up by the high data throughput, clock precision, and noise resilience offered by this technology. Specifically, as a third contribution, we demonstrate that CTX not only can be successfully exploited for multi-hop UWB communications but, once embodied in a full-fledged system, provide reliability and energy performance akin to narrowband. Furthermore, the higher data rate and clock resolution of UWB chips unlock up to 80% latency reduction w.r.t. narrowband CTX, along with orders-of-magnitude improvements in network-wide time synchronization. These results showcase how UWB CTX could significantly benefit a multitude of applications, notably including low-power wireless control. With WEAVER, our last contribution, we make an additional step towards this direction, by supporting the key functionality of data collection with an ultra-fast convergecast stack for UWB. Challenging the internal mechanics of CTX, WEAVER interleaves data and acknowledgements flows in a single, self-terminating network-wide flood, enabling the concurrent collection of different packets from multiple senders with unprecedented latency, reliability, and energy efficiency. Overall, this thesis pushes forward the applicability and performance of low-power wireless, by contributing techniques and protocols to enhance the dependability, timeliness, energy efficiency, and interference resilience of this technology. Our research is characterized by a strong experimental slant, where the design of the systems we propose meets the reality of testbed experiments and evaluation. Via our open-source implementations, researchers and practitioners can directly use, extend, and build upon our contributions, fostering future work and research on the topic.

Low-power wireless technology is a part and parcel of our daily life, shaping the way in which we behave, interact, and more generally live. The ubiquity of cheap, tiny, battery-powered devices augmented with sensing, actuation, and wireless communication capabilities has given rise to a ``smart" society, where people, machines, and objects are seamlessly interconnected, among themselves and with the environment. Behind the scenes, low-power wireless protocols are what enables and rules all interactions, organising these embedded devices into wireless networks, and orchestrating their communications. The recent years have witnessed a persistent increase in the pervasiveness and impact of low-power wireless. After having spawned a wide spectrum of powerful applications in the consumer domain, low-power wireless solutions are extending their influence over the industrial context, where their adoption as part of feedback control loops is envisioned to revolutionise the production process, paving the way for the Fourth Industrial Revolution. However, as the scale and relevance of low-power wireless systems continue to grow, so do the challenges posed to the communication substrates, required to satisfy ever more strict requirements in terms of reliability, responsiveness, and energy consumption. Harmonising these conflicting demands is far beyond what is enabled by current network stacks and control architectures; the need to timely bridge this gap has spurred a new wave of interest in low-power wireless networking, and directly motivated our work. In this thesis, we take on this challenge with a main conceptual and technical tool: concurrent transmissions (CTX), a technique that, by enforcing nodes to transmit concurrently, has been shown to unlock unprecedented fast, reliable, and energy efficient multi-hop communications in low-power wireless networks, opening new opportunities for protocol design. We first direct our research endeavour towards industrial applications, focusing on the popular IEEE 802.15.4 narrowband PHY layer, and advance the state of the art along two different directions: interference resilience and aperiodic wireless control. We tackle radio-frequency noise by extensively analysing, for the first time, the dependability of CTX under different types, intensities, and distributions of reproducible interference patterns, and by devising techniques to push it further. Specifically, we concentrate on CRYSTAL, a recently proposed communication protocol that relies on CTX to rapidly and dependably collect aperiodic traffic. By integrating channel hopping and noise detection in the protocol operation, we provide a novel communication stack capable of supporting aperiodic transmissions with near-perfect reliability and a per-mille radio duty cycle despite harsh external interference. These results lay the ground towards the exploitation of CTX for aperiodic wireless control; we explore this research direction by co-designing the Wireless Control Bus (WCB), our second contribution. WCB is a clean-slate CTX-based communication stack tailored to event-triggered control (ETC), an aperiodic control strategy holding the capability to significantly improve the efficiency of wireless control systems, but whose real-world impact has been hampered by the lack of appropriate networking support. Operating in conjunction with ETC, WCB timely and dynamically adapts the network operation to the control demands, unlocking an order-of-magnitude reduction in energy costs w.r.t. traditional periodic approaches while retaining the same control performance, therefore unleashing and concretely demonstrating the true ETC potential for the first time. Nevertheless, low-power wireless communications are rapidly evolving, and new radios striking novel trade-offs are emerging. Among these, in the second part of the thesis we focus on ultra-wideband (UWB). By providing hitherto missing networking primitives for multi-hop dissemination and collection over UWB, we shed light on the communication potentialities opened up by the high data throughput, clock precision, and noise resilience offered by this technology. Specifically, as a third contribution, we demonstrate that CTX not only can be successfully exploited for multi-hop UWB communications but, once embodied in a full-fledged system, provide reliability and energy performance akin to narrowband. Furthermore, the higher data rate and clock resolution of UWB chips unlock up to 80% latency reduction w.r.t. narrowband CTX, along with orders-of-magnitude improvements in network-wide time synchronization. These results showcase how UWB CTX could significantly benefit a multitude of applications, notably including low-power wireless control. With WEAVER, our last contribution, we make an additional step towards this direction, by supporting the key functionality of data collection with an ultra-fast convergecast stack for UWB. Challenging the internal mechanics of CTX, WEAVER interleaves data and acknowledgements flows in a single, self-terminating network-wide flood, enabling the concurrent collection of different packets from multiple senders with unprecedented latency, reliability, and energy efficiency. Overall, this thesis pushes forward the applicability and performance of low-power wireless, by contributing techniques and protocols to enhance the dependability, timeliness, energy efficiency, and interference resilience of this technology. Our research is characterized by a strong experimental slant, where the design of the systems we propose meets the reality of testbed experiments and evaluation. Via our open-source implementations, researchers and practitioners can directly use, extend, and build upon our contributions, fostering future work and research on the topic.

碩士
國立臺北大學
通訊工程研究所
105
In recent years, there is a fast growing demand on trac safety and transportation eciency, in particular auto-driving becomes an evident future trend. Due to the significance of vehicular safety, the tranceiving of urgent information regarding a moving car must have a very low latency and should be highly reliable. It is thus referred to as the Ultra-Reliable Communications type in the standardization. The traditional forward error correction coding (FEC) schemes such as turbo codes and low-density parity-check codes (LDPC) suer error oor eect at high signal-to-noise ratio (SNR) and hence is generally considered not suitable for Ultra-Reliable Communications. At this background, this thesis devotes to the design of low rate coding schemes for Ultra-Reliable Communications. The so-called CC-SPC coding scheme that is formed by concatenating the convolutional code with the simple parity check code is then proposed Simulation results show that the proposed low-rate CC-SPC is highly reliable in its transmission and can meet the requirement of the Ultra-Reliable Communications.

碩士
國立交通大學
網路工程研究所
106
For 5G wireless communications, the 3GPP Narrowband Internet of Thing (NB-IoT) is one of the most promising technologies, which provides multiple types of Resource Unit (RU) with a special repetition mechanism to improve scheduling flexibility, coverage, and transmission reliability. Besides, NB-IoT supports different operation modes to reuse the spectrum of LTE and GSM, making bandwidth use more efficiently. As IoT devices usually need to operate for very long time, their energy consumption becomes a critical issue. NB-IoT provides discontinuous reception operation to save devices' energy. However, how to reduce transmission energy while ensuring required reliability under these operations is still an open issue. In this paper, we study how to guarantee reliable communication and satisfy devices' quality of service (QoS) while minimizing energy consumption for IoT devices. We first model the optimization problem and prove it to be NP-complete. Then, we propose an energy-efficient, ultra-reliable, and low-complexity scheme, which consists of two phases. The first phase tries to optimize the default transmit configurations of devices which incur the lowest energy consumption and satisfy devices' QoS requirements. The second phase leverages a weighting strategy to balance the urgency and slot availability and ensure delay constraint while maintaining energy efficiency. Extensive simulation results show that our scheme can serve more devices with guaranteed QoS while saving their energy effectively.

碩士
元智大學
電機工程學系乙組
107
This thesis is to research the transceiver design of the uplink control and data channels of 5G mobile communication systems. This research focuses on the use of low complexity technology to achieve high reliability and low latency communication proposes. In this thesis, we adopt the 5G-NR physical layer specification, i.e., 3GPP 38.211, to design the transceiver of the Physical Uplink Control Channel (PUCCH) and Physical Uplink Share Channel (PUSCH). In wireless communications, the receiver involves multiple distortion factors, e.g., multipath and carrier frequency offset (CFO) effect. This thesis proposes the low complexity channel estimation/equalization and CFO estimation/compensation to overcome the above factors. Next, to analyze the performance of the proposed algorithms, the software simulation platform of PUCCH and PUSCH channels is built to use for different fading scenarios. Moreover, for SDR software radio verification, the thesis utilizes the E4438C, E4406A instruments, USRP module, and 89600 VSA to evaluate the performances of PUCCH and PUSCH transceivers. Finally, for FPGA board verification, the circuits of the 5G-NR PUSCH transceiver are designed by Simulink HDL coder, which can generate Verilog code and convert to bitstream file via Vivado software. Then, using Simulink HDL verifier software to build Xilinx FPGA circuits, the FPGA hardware circuits can perform the same results with the Simulink software circuits. It confirms the proposed hardware design being correct. To sum up, this thesis combines the theory, simulation, instruments, modules, and circuit design verifications to overcome the multipath and CFO effects and to achieve the 5G purposes of low complexity, high reliable, and low latency communications transceiver design.

碩士
國立中央大學
電機工程學系
102
Design and analysis of the flip-chip bonding package for near-ballistic uni-traveling-carrier photodiodes (NBUTC-PDs) with reliable high-power performance from dc to sub-THz (~300 GHz) frequency has been demonstrated. According to our simulation and measurement results, the geometric size of flip-chip bonding structure becomes a major limitation in speed and output power when the operating frequency is over ~100 GHz. In order to overcome this problem, the position of Au/Sn bump on bottom AlN substrate for bonding process, must be as close as possible with the active PD mesa on the InP substrate at topside. Compared with the control with a longer spacing (~90 vs. 25 m), our device not only exhibits a broader bandwidth (225 vs. 200 GHz) but also a higher saturation current (13 vs. 9 mA). With such an optimized flip-chip bonding structure for package of NBUTC-PD, a wide 3-dB bandwidth (~225 GHz), high saturation current (13 mA), and a 0.67 mW maximum output power at 260 GHz operating frequency have been achieved simultaneously.

Network connectivity is a fundamental property affecting network performance. Given the reliability of each link, network connectivity determines the probability that a message can be delivered from the source to the destination. In this thesis, we study the directed network connectivity where the message will be forwarded toward the destination hop by hop, so long as the neighbor(s) is (are) closer to the destination. Directed connectivity, closely related to directed percolation, is very complicated to calculate. The existing state-of-the-art can only calculate directed connectivity for a lattice network up-to-the size of 10 × 10. In this thesis, we devise a new approach that is simpler and more scalable and can handle general network topology and heterogeneous links. The proposed approach uses an unambiguous hop count to divide the networks into hops and gives two steps of pre-process to transform hop-count ambiguous networks into unambiguous ones, and derive the end-to-end connectivity. Then, using the Markov property to obtain the state transition probability hop by hop. Second, with tens of thousands of Low Earth Orbit (LEO) satellites covering the Earth, LEO satellite networks can provide coverage and services that are otherwise not possible using terrestrial communication systems. The regular and dense LEO satellite constellation also provides new opportunities and challenges for network protocol design. In this thesis, we apply the directed connectivity analytical model on LEO satellite backbone networks to ensure ultra-reliable and low-latency (URLL) services using LEO networks, and propose a directed percolation routing (DPR) algorithm to lower the cost of transmission without sacrificing speed. Using Starlink constellation (with 1,584 satellites) as an example, the proposed DPR can achieve a few to tens of milliseconds latency reduction for inter-continental transmissions compared to the Internet backbone, while maintaining high reliability without link-layer retransmissions. Finally, considering the link redundancy overhead and delay/reliability tradeoff, DPR can control the size of percolation. In other words, we can choose a part of links to be active links considering the reliability and cost tradeoff.
Graduate

Ultra-reliable and low latency communications (URLLC) is a novel use case of 5G. It has challenging requirements like such as low block error rates (BLERs) and stringent latency targets. Multi-connectivity, in which multiple base stations (BSs) transmit the same data to the user, is a key technique in 5G to meet the stringent reliability requirements. URLLC data is immediately transmitted by puncturing the ongoing enhanced mobile broadband (eMBB) transmission to satisfy the latency constraint. However, this results in an increase in the BLER of the eMBB users. We first propose a low complexity multi-connectivity MCS selection algorithm (MCMSA) to select the subset of co-operating BSs and the modulation and coding schemes (MCSs) they employ. The goal is to minimize the eMBB throughput loss while satisfying the URLLC constraints. We study two types of multi-connectivity: orthogonal transmission (OT) and joint transmission (JT). We derive tractable expressions to calculate the achievability, which is the probability that the URLLC reliability requirement can be satisfied by the multi-connectivity. We do so for flat fading and frequency-selective fading scenarios. Our results highlight the trade-offs between URLLC achievability, eMBB throughput loss, and channel state information (CSI) feedback overhead of OT and JT. We then consider time-varying channels, in which the CSI report from the URLLC user to the BSs about the downlink channel gains becomes partially outdated by the time the BSs transmit data. We propose a novel stochastic BLER constraint for selecting MCSs at the time of transmission. We derive expressions for the conditional probability that the BLER of an MCS at the time of transmission is less than the target given the CSI fed back. These expressions enable the selection of MCS at the time transmission and meets the URLLC error target with high probability. Our results bring out the significant impact of feedback delays on reliability even at moderate Doppler spreads.

As technology evolves, more Machine to Machine (M2M) deployments and mission critical services are expected to grow massively, generating new and diverse forms of data traffic, posing unprecedented challenges in requirements such as delay, reliability, energy consumption and scalability. This new paradigm vindicates a new set of stringent requirements that the current mobile networks do not support. A new generation of mobile networks is needed to attend to this innovative services and requirements - the The fifth generation of mobile networks (5G) networks. Specifically, achieving ultra-reliable low latency communication for machine to machine networks represents a major challenge, that requires a new approach to the design of the Physical (PHY) and Medium Access Control (MAC) layer to provide these novel services and handle the new heterogeneous environment in 5G. The current LTE Advanced (LTE-A) radio access network orthogonality and synchronization requirements are obstacles for this new 5G architecture, since devices in M2M generate bursty and sporadic traffic, and therefore should not be obliged to follow the synchronization of the LTE-A PHY layer. A non-orthogonal access scheme is required, that enables asynchronous access and that does not degrade the spectrum. This dissertation addresses the requirements of URLLC M2M traffic at the MAC layer. It proposes an extension of the M2M H-NDMA protocol for a multi base station scenario and a power control scheme to adapt the protocol to the requirements of URLLC. The system and power control schemes performance and the introduction of more base stations are analyzed in a system level simulator developed in MATLAB, which implements the MAC protocol and applies the power control algorithm. Results showed that with the increase in the number of base stations, delay can be significantly reduced and the protocol supports more devices without compromising delay or reliability bounds for Ultra-Reliable and Low Latency Communication (URLLC), while also increasing the throughput. The extension of the protocol will enable the study of different power control algorithms for more complex scenarios and access schemes that combine asynchronous and synchronous access.