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RESUMEN: El desarrollo de las tecnologías 5G y 6G viene acompañado de cambios importantes en las redes de acceso, como consecuencia de la capacidad de virtualizar y ejecutar, sobre equipos de propósito general, las funcionalidades de las estaciones base que antes se debían realizar en equipos dedicados, complejos y de altas capacidades. Gracias a esta transformación surge el concepto de functional split. Esta virtualización, basada en Software Defined Network/Network Function Virtualization (SDN/NFV), ha permitido junto con el de Cloud/Centralizad Radio Access Network (C-RAN) una mayor cooperación de los elementos de la red, lográndose una mayor adaptación ante la aparición de nuevos servicios, con requisitos heterogéneos, y una mayor demanda. Por otro lado, se han desarrollado soluciones Software Defined Radio (SDR) que permiten desplegar estaciones bases de diferentes generaciones celulares en equipos de bajas prestaciones, facilitando el proceso de desarrollo de soluciones y su posterior validación por personal investigador y académico, ajeno a las operadoras. En este trabajo, se ha utilizado la solución SDR srsRAN (antes denominada srsLTE), adaptando su implementación para lograr la separación y aislamiento de diversas funcionalidades de red. De este modo, se consigue centralizar parte de su operación, que se ejecuta de forma virtualizada, en el propio equipo u otro. Además, se ha realizado un estudio del consumo computacional de la implementación realizada en diferentes equipos y la validación de las diferentes divisiones funcionales, llamadas splits, desarrolladas. ABSTRACT: The development of 5G and 6G technologies comes together with major changes in the access network architecture, due to the ability to virtualise and execute, in general purpose equipment, base station functionalities that previously were only deployed in specific purpose devices. This evolution gave rise to the concept of “functional split”. This virtualisation capability, leveraging Software Defined Network/Network Function Virtualisation (SDN/NFV), together with the Cloud/Centralised Radio Access Network (C-RAN), has enabled a greater cooperation between network elements, easing the adaptation of new emerging services, with heterogeneous requirements, and the greater capacity demand. On the other hand, Software Defined Radio (SDR) solutions have been developed, and they allow the deployment of base stations (belonging to different cellular technologies) in low-capability equipment. In turn, it has simplified the process of developing solutions and their subsequent validation by the research and scientific communities, outside operators. In this work, we have modified the implementation of the SDR solution srsRAN (previously named srsLTE) to achieve the separation and isolation of different network functionalities. In this way, it is possible to centralise part of its operation, which is executed in virtualised resources, at the same or another equipment. In addition, we have also studied the computational consumption of the implemented solution in different devices, and we have assessed the feasibility of various functional divisions, called “splits”. Máster en Ingeniería de Telecomunicación

Two popular Crest Factor Reduction techniques applicable to OFDM signals have been studied and implemented within this project. To provide adequate background, a brief description of OFDM communication systems is included in the first sections, and the problem of high Peak to Average Power Ratio in multi-carrier transmission schemes is presented. An overview of the most relevant Crest Factor Reduction techniques is performed, and the Clipping and Filtering and Peak Windowing algorithms are selected as implementation candidates due to their protocol agnostic nature. Several implementation architectures have been discussed, and the most computationally efficient one has been used to implement both algorithms within srsRAN, an open source, full software radio implementation of an LTE network with all of its components. In order to provide a comprehensive evaluation of the developed algorithms, an extensive measurement campaign has been designed and carried out, comprised of synthetic testing, as well as experimental physical signal measurements in a laboratory setting, and an outdoor measurement campaign. To speed up the measurement process, an automated measurement system has been designed in MATLAB, which remotely operates a signal analyser to perform spectrum and statistical power measurements, as well as IQ sample collection of the generated LTE signals. This measurement system has been used to carry out unwanted emissions tests following the LTE conformance testing procedures, which are also discussed within this document. For the outdoor measurements, an LTE single cell network has been deployed using a software radio transceiver and an LTE phone, with the aim of assessing the end to end quality of service improvements provided by the developed algorithms. The gathered results illustrate that the implemented Crest Factor Reduction techniques can provide significant network performance gains in situations with limited available transmission power. Additional gains provided by these techniques include increased efficiency in the operation of power amplification stages, and reduced network deployment costs. Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura