The evolution and deployment of fifth-generation (5G) and beyond (B5G) infrastructure will require a tremendous effort to specify the design, standards, and manufacturing. 5G is vital to modern technological evolution, including industry 4.0, automotive, entertainment, and health care. The ambitious and challenging 5G project is classified into three categories, which provide an essential supporting platform for applications associated with: Enhanced mobile broadband (eMBB) Ultra-reliable low-latency communication (URLLC) Massive machine-type communication (mMTC) The demand for URLLC grows, particularly for applications like autonomous guided vehicles (AGVs), unmanned aerial vehicles (UAVs), and factory automation, and has a strict requirement of low latency of 1 ms and high reliability of 99.999%. To meet the needs of communication-sensitive and computation-intensive applications with different quality-of-service (QoS) requirements, this evolution focuses on ultra-dense edge networks with multi-access edge computing (MEC) facilities. MEC emerges as a solution, placing resourceful servers closer to users. However, the dynamic nature of processing and interaction patterns necessitates effective network control, which is challenging due to stringent requirements on both communication and computation. In this context, we introduce a novel approach to optimally manage task offloading, considering the intricacies of heterogeneous computing and communication services. Unlike existing methods, our methodology incorporates the number of admitted service migrations and QoS upper and lower bounds as binding constraints. The comprehensive model encompasses agent positions, MEC servers, QoS requirements, edge network communication, and server computing capabilities. Formulated as a mixed-integer linear program (MILP), it provides an optimal schedule for service migrations and bandwidth allocation, addressing the challenges posed by computation-intensive and communication-sensitive applications. Moreover, tailoring to an indoor robotics environment, we explore optimization-based approaches seeking an optimal system-level architecture while considering QoS guarantees. Optimization tools, e.g., ARCHEX, prove their ability to capture cyber-physical systems (CPS) requirements and generate correct-by-construction architectural solutions. We propose an extension in ARCHEX by incorporating dynamic properties, i.e., robot trajectories, time dimension, application-specific QoS constraints, and finally, integrating the optimization tool with a discrete-event network simulator (OMNeT++). This extension automates the generation of configuration files and facilitates result analysis, ensuring a comprehensive evaluation. This part of the work focuses on the dynamism of robots, server-to-service mapping, and the integration of automated simulation. The proposed extension is validated by optimizing and analyzing various indoor robotics scenarios, emphasizing critical performance parameters such as overall throughput and end-to-end delay (E2E). This integrated approach addresses the complex interplay of computation and communication resources, providing a solution for dynamic mobility, traffic, and application patterns in edge server environments.

<p dir="ltr"> The general design goal of low latency communication systems is to minimize the end-to-end delay while attaining the predefined reliability and throughput requirements. The burgeoning demand for low latency communications motivates a renewed research interest of the tradeoff between delay, throughput, and reliability. In this dissertation research, we consider slotted-based systems and explore the potential advantages of the so-called sequential codes in low latency network communications.</p><p dir="ltr"> The first part of this dissertation analyzes the exact error probability of random linear streaming codes (RLSCs) in the large field size regime over the stochastic independently and identically distributed (i.i.d.) symbol erasure channels (SECs). A closed-form expression of the error probability <i>p</i>_<em>e</em> of large-field-size RLSCs is derived under, simultaneously, the finite memory length α and decoding deadline Δ constraints. The result is then used to examine the intricate tradeoff between memory length (complexity), decoding deadline (delay), code rate (throughput), and error probability (reliability). Numerical evaluation shows that under the same code rate and error probability requirements, the end-to-end delay of RLSCs is 40-48% of that of the optimal block codes (i.e., MDS codes). This implies that switching from block codes to streaming codes not only eliminates the queueing delay completely (which accounts for the initial 50% of the delay reduction) but also improves the reliability (which accounts for the additional 2-10% delay reduction).</p><p dir="ltr"> The second part of this dissertation focuses on the asymptotics of the error probability of RLSCs in the same system model of the first part. Two important scenarios are analyzed: (i) tradeoff between Δ and <i>p</i>_<em>e</em> under infinite α; and (ii) tradeoff between α and <i>p</i>_<em>e</em> under infinite Δ. In the first scenario, the asymptote of <i>p</i>_<em>e</em>(Δ) is shown to be <i>ρ</i>Δ^-1.5<i>e</i>^-^<em>η</em>^Δ. The asymptotic power term Δ^-1.5 of RLSCs is a strict improvement over the Δ^-0.5 term of random linear block codes. A pair of upper and lower bound on the asymptotic constant <i>ρ</i> is also derived, which are tight (i.e., identical) for one specific class of SECs. In the second scenario, a refine approximation is proposed by computing the parameters in a multiterm asymptotic form, which closely matches the exact error probability even for small memory length (≈ 20). The results of the asymptotics can be further exploited to find the <i>c</i>-optimal memory length <i>α</i>_<em>c</em>^*(Δ), which is defined as the minimal memory length α needed for the resulting <i>p</i>_<em>e</em> to be within a factor of <i>c</i>>1 of the best possible <i>p</i>_<em>e</em>^<em>*</em>_{<em> </em>}for any Δ, an important piece of information for practical implementation.</p><p dir="ltr"> Finally, we characterize the channel dispersions of RLSCs and MDS block codes, respectively. New techniques are developed to quantify the channel dispersion of sequential (non-block-based) coding, the first in the literature. The channel dispersion expressions are then used to compare the levels of error protection between RLSCs and MDS block codes. The results show that if and only if the target error probability <i>p</i>_<em>e</em> is smaller than a threshold (≈ 0.1774), RLSCs offer strictly stronger error protection than MDS block codes, which is on top of the already significant 50% latency savings of RLSCs that eliminate the queueing delay completely.</p>

[ES] Las redes móviles de quinta generación (5G) destacan por su robustez, superando las prestaciones ofrecidas por sus predecesoras. Estas redes, comúnmente denominadas 5G, posibilitan mejoras significativas en los indicadores clave de rendimiento (KPIs, por sus siglas en inglés) con el propósito de respaldar casos de uso y servicios avanzados. Estos KPIs se clasifican en tres escenarios fundamentales: Banda Ancha Móvil Mejorada (eMBB, por sus siglas en inglés), Comunicaciones Ultra Fiables y de Baja Latencia (uRLLC, por sus siglas en inglés) y Comunicaciones Masivas entre Máquinas (mMTC, por sus siglas en inglés). El escenario eMBB se orienta primordialmente hacia servicios que demandan elevadas tasas de transmisión y recepción para garantizar una experiencia de usuario mejorada. En contraste, uRLLC aborda situaciones que requieren estrictos estándares de baja latencia y alta confiabilidad en la red, como es el caso de aplicaciones en tiempo real, donde la pronta respuesta de la red es indispensable. Por su parte, el escenario mMTC se refiere a aplicaciones y servicios que solicitan el respaldo de la red para la conectividad masiva de dispositivos por kilómetro cuadrado, además de una eficiencia energética mejorada. Entre los servicios y aplicaciones más destacados, se encuentran aquellos basados en comunicaciones vehiculares mediante la red celular, conocidos en el estándar como comunicaciones V2X. En términos generales, la comunicación V2X engloba el intercambio de paquetes entre vehículos y diversos elementos de la red. Cuando estas comunicaciones se efectúan mediante estándares basados en redes móviles, ya sea en LTE o NR, la interfaz radio de 5G, se denominan C-V2X. En este contexto, las comunicaciones Vehículo a Vehículo (V2V) posibilitan el intercambio de paquetes entre vehículos, mientras que las comunicaciones de Vehículos con Infraestructuras (V2I) facilitan el intercambio entre vehículos e infraestructuras de red. Por su parte, las comunicaciones de Vehículos con Peatones (V2P) comprenden la transferencia de paquetes entre vehículos y dispositivos portados por peatones, y las comunicaciones Vehículo a Red (V2N) permiten el intercambio de tráfico V2X entre vehículos y la red. Cada tipo de comunicación posibilita la implementación de diversos servicios, desde funciones básicas hasta aplicaciones avanzadas que exigen potenciales requerimientos por parte de la red. En esta Tesis Doctoral, se llevó a cabo una revisión exhaustiva del estándar para comunicaciones V2X LTE y NR V2X, destacando particularmente los modos de comunicación descentralizados, como se mencionó anteriormente. Posteriormente, se realizó una campaña de simulaciones a nivel de sistema para configurar escenarios V2X conforme a las especificaciones del 3GPP. Los resultados obtenidos permitieron evidenciar que las prestaciones del modo 4 en LTE son adecuadas para servicios básicos que no requieren un alto throughput, bajas latencias o estrictos criterios de fiabilidad en la red. En contraste, mediante el modo 2 de NR V2X, se observó un rendimiento mejorado, lo que permite la adaptación a servicios V2X avanzados. Asimismo, se demostró que altas numerologías contribuyen a un mejor comportamiento del sistema al proporcionar una mayor diversidad de recursos, reduciendo la probabilidad de que dos vehículos utilicen los mismos recursos para sus transmisiones en el modo descentralizado. Además, se comprobó que en NR V2X es crucial una combinación adecuada de numerologías, anchos de banda de canal y tamaño de los subcanales sidelink, según los servicios V2X a implementar. Finalmente, se analizó la incorporación de tecnologías de múltiples accesos radio (multi-RAT) con el fin de respaldar servicios avanzados y mejorar la interoperabilidad mediante el uso de tecnologías de acceso basadas en LTE y NR, especialmente en escenarios con múltiples operadores de red móvil (MNOs), interfaces de conexión y modos de comunicación. / [CA] Les xarxes mòbils de cinquena generació (5G) destaquen per la seva robustesa, superant les característiques que ofereixen els seus predecessors. Aquestes xarxes, comunament anomenades 5G, permeten millores significatives en els indicadors de rendiment clau (KPI) per donar suport a casos i serveis d'ús avançats. Aquests KPI es classifiquen en tres escenaris fonamentals: banda ampla mòbil millorada (eMBB), comunicacions de baixa latència i fiabilitat (uRLLC) i comunicacions massives entre màquines (mMTC). L'escenari eMBB s'orienta principalment a serveis que exigeixen altes taxes de transmissió i recepció per garantir una millor experiència d'usuari. En canvi, uRLLC aborda situacions que requereixen estàndards estrictes de baixa latència i alta fiabilitat de la xarxa. Aquesta necessitat es manifesta, per exemple, en aplicacions en temps real on la resposta ràpida a la xarxa és un factor indispensable. Pel que fa a l'escenari mMTC, es refereix a aplicacions i serveis que sol·liciten suport de xarxa per a una connectivitat massiva de dispositius per quilòmetre quadrat, a més d'una millora de l'eficiència energètica. Entre els serveis i aplicacions esmentats, destaquen els basats en comunicacions vehiculars a través de la xarxa cel·lular, coneguts segons la norma com a comunicacions V2X. En termes generals, la comunicació V2X engloba l'intercanvi de paquets entre vehicles i diversos elements de xarxa. Quan aquestes comunicacions es realitzen utilitzant estàndards basats en xarxes mòbils, ja sigui en Evolució a llarg termini (LTE) o Nova Ràdio (NR), s'anomenen C-V2X. En aquest context, les comunicacions Vehicle-to-Vehicle (V2V) permeten l'intercanvi de paquets entre vehicles, mentre que les comunicacions Vehicle-to-Infraestructura (V2I) faciliten l'intercanvi entre vehicles i infraestructures de xarxa. Per la seva banda, les comunicacions Vehicle-to-Pedestrian (V2P) inclouen la transferència de paquets entre vehicles i dispositius transportats per vianants, i les comunicacions Vehicle a Xarxa (V2N) permeten l'intercanvi de trànsit V2X entre vehicles i la xarxa. Cada tipus de comunicació permet la implementació de diversos serveis, des de funcions bàsiques fins a aplicacions avançades que requereixen possibles requisits de la xarxa. En aquesta tesi, es va dur a terme una revisió exhaustiva de les directrius estàndard per a les comunicacions V2X LTE i NR V2X, destacant especialment els modes de comunicació descentralitzats, com s'ha esmentat anteriorment. Posteriorment, es va dur a terme una campanya de simulació a nivell de sistema per configurar escenaris V2X segons les especificacions del Projecte d'Associació de Tercera Generació (3GPP). Els resultats obtinguts van mostrar que el rendiment del mode 4 en LTE és adequat per a serveis bàsics que no requereixen un alt rendiment, latències baixes o criteris estrictes de fiabilitat de la xarxa. En canvi, es va observar un rendiment millorat mitjançant el mode 2 NR V2X, permetent l'adaptació a serveis V2X avançats. A més, s'ha demostrat que les numerologies altes contribueixen a un millor rendiment, proporcionant una major diversitat de recursos i reduint la probabilitat que dos vehicles utilitzin els mateixos recursos per a les seves transmissions en mode descentralitzat. A més, es va trobar que a NR V2X una combinació adequada de numerologies, amplades de banda del canal i mida dels subcanals SL és crucial, depenent dels serveis V2X a implementar. Finalment, es va analitzar la incorporació de múltiples tecnologies d'accés a la ràdio (multi-RAT) per donar suport a serveis avançats i millorar la interoperabilitat mitjançant l'ús de tecnologies d'accés basades en LTE i NR, especialment en escenaris amb múltiples operadors de xarxa mòbil (MNO), diferents interfícies de connexió i modes de comunicació. / [EN] Fifth-generation mobile networks, commonly referred to as Fifth Generation (5G), are known for their robustness and surpassing the performance of their predecessors. They enable significant improvements in Key Performance Indicators (KPIs) to support advanced use cases and services. These KPIs are classified into three fundamental scenarios: Enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communications (uRLLC), and massive Machine Type Communications (mMTC). The eMBB scenario focuses on services that require high transmission and reception rates to improve the user experience. In contrast, uRLLC addresses situations that demand strict low latency and high-reliability standards in the network. This need is particularly evident in real-time applications where prompt network response is essential. The mMTC scenario pertains to applications and services that require network support for massive device connectivity per square kilometer and enhanced energy efficiency. In particular, services and applications based on vehicular communications via the cellular network, referred to as Vehicle-to-everything (V2X) communications in the standard, are prominent. V2X communication refers to the communication between vehicles and infrastructures. When using mobile network standards such as Long Term Evolution (LTE) or New Radio (NR), it is referred to as Cellular-based V2X (C-V2X). Vehicle-to-Vehicle (V2V) communication enables packet exchange between vehicles, while Vehicle-to-Infrastructure (V2I) facilitates the exchange between vehicles and network infrastructures. Vehicle-to-Pedestrian (V2P) and Vehicle-to-Network (V2N) are two other types of communication that enable the transfer of packets between vehicles and devices carried by pedestrians and the exchange of V2X traffic between vehicles and the network, respectively. These types of communication enable the implementation of various services, from basic functions to advanced applications with potential network requirements. This thesis provides a comprehensive review of the standard guidelines for V2X LTE and NR V2X communications, with a particular focus on the decentralized communication modes mentioned above. Following this, system-level simulations were conducted to configure V2X scenarios according to 3GPP specifications. The results indicate that LTE mode 4 is sufficient for essential services that do not require high throughput, low latencies, or strict network reliability criteria. On the other hand, NR V2X mode 2 showed improved performance, allowing adaptation to advanced V2X services. High numerologies have been shown to contribute to better performance by providing greater resource diversity and reducing the probability that two vehicles use the same resources for their transmissions in decentralized mode. Additionally, it was found that in NR V2X, an adequate combination of numerologies, channel bandwidths, and sidelink subchannel sizes is crucial, depending on the V2X services to be implemented. Finally, the incorporation of multiple Radio Access Technologies (multi-RAT) was analyzed to support advanced services and improve interoperability through the use of LTE and NR-based access technologies, especially in scenarios with multiple Mobile Network Operators (MNOs), connection interfaces, and communication modes. / González Malla, EE. (2024). Performance Evaluation of 3GPP Standards for C-V2X Communications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/214051