De nos jours, la montée en débit observée dans les réseaux mobiles est une problématique. A long terme, la densification des réseaux radios mobiles s'avérera inefficace. En plus de cela cette densification entraînera une baisse de rentabilité des réseaux d'accès mobiles et augmentera la complexité au niveau de la gestion des fréquences mobile qui accroîtra inéluctablement le risque de la présence des interférences. Pour pallier ce manque de rentabilité et pour faciliter le déploiement de certaines techniques d'optimisation et d'amélioration de l'interface air comme le « Coordinated MultiPoint » (CoMP), les acteurs des télécommunications proposent une nouvelle architecture innovante désignée par les termes Mobile Cloud ou « Centralized or Cloud Radio Access Network » (C-RAN). Le C-RAN consiste à déporter l'entité de traitement des données numérisées appelée « Base Band Unit » (BBU) du site d'antenne vers un local plus sécurisé nommé « Central Oce (CO) ». L'entité de traitement radio dénommée « Remote Radio Head (RRH) »est toujours localisée sur le site d'antenne. Cette délocalisation crée un nouveau segment réseau appelé « fronthaul ». Le fronthaul est un segment réseau très gourmand en bande passante par conséquent la fibre est désignée comme le support idéal pour assurer la communication bidirectionnelle entre la RRH et la BBU. Dans notre thèse, nous avons étudié les solutions de déploiement du fronthaul. Etant donné que l'interface fronthaul utilise de grands débits pour la transmission de données numérisées, elle est soumise à un phénomène physique nommé gigue qui a tendance à dégrader les performances de transmission. Les effets et l'impact de la gigue sur l'interface fronthaul et sur l'interface air ont été aussi étudiés. / In Europe, the competition between the mobile operators is so strong that the profitability of the mobile network has decreased. The cost to implement, to operate and to upgrade the mobile network is increasing while the revenues generated by the latter are not sufficient. Therefore, the operators should find the way to reduce the CAPEX and the OPEX. To keep competitive, the operators have begun to think about a novel RAN architecture. This new architecture is called Centralized or Cloud Radio Access Network. The traditional antenna site consists of the Radio Remote Head (RRH) which performs the radio processing, and the Base Band Unit (BBU) which carries out the digital processing. The principle of C-RAN consists to move the BBU from antenna site towards the local secured belonging to an operator called Central Office (CO). The move of BBU from antenna site to CO leads to the appearance of a new network segment called fronthaul. During this thesis, the different solutions to the deployment of fronthaul are studied and also the effects and the impacts of jitter on the fronthaul interface.

Current mobile network architecture is facing a big challenge as the traffic demands have been increasing dramatically these years. Explosive mobile data demands are driving a significant growth in energy consumption in mobile networks, as well as the cost and carbon footprints [1]. In 2010, China Mobile Research Institute proposed Cloud Radio Access Network (C-RAN) [2], which has been regarded as one of the most promising architecture to solve the challenge of operators. In C-RAN, the baseband units (BBU) are decoupled from the remote radio units (RRH) and centralized in one or more locations. The feasibility of combination of implementing the very tight radio coordination schemes and sharing baseband processing and cooling system resources proves to be the two main advantages of C-RAN compared to traditional RAN. More importantly, mobile operators can quickly deploy RRHs to expand and make upgrades to their networks. Therefore, the C-RAN has been advocated by both operators and equipment vendors as a means to achieve the significant performance gains required for 5G [3]. However, one of the biggest barriers has shown up in the deployment of C-RAN as the novel architecture imposes very high capacity requirement on the transport network between the RRHs and BBUs, which is been called fronthaul network. With the implementation of 5G wireless system using advanced multi-antenna transmission (MIMO), the capacity requirement would go further up, as well as the power consumption. One solution has been proposed to solve the problem is to have the baseband functions divided, partially staying with RRHs and other functions would be centralized in BBU pool. Different splitting solutions has been proposed in [4] [5] and [6]. In this thesis work, we choose four different splitting solutions to build four CRAN architecture models. Under one specific case scenario with the fixed number of LTE base stations, we calculate the transport capacity requirement for fronthaul and adopt three different fronthaul technology. The power consumption is calculated by adding up the power utilized by RRHs, fronthaul network and baseband processing. By comparing the numerical results, split 1 and 2 shows the best results while split 2 is more practical for dense cell area, since split 1 requires large fronthaul capacity. The fronthaul transport technology can be decided according to different density of base stations. TWDM-PON shows better energy performance as fronthaul network when the capacity requirement is high, compared to EPON. However, for larger number of BSs, mm-Wave fronthaul is a better solution in terms of energy efficiency, fiber saving and flexibility.

The increasing traffic demand from the use of 3G/4G, streaming, and other broadband wireless services exposes existing bottlenecks in the communications infrastructure and the coordination between the wireless network and its wired counterpart. While wireless systems are constantly evolving to newer generations and higher capacities, their supporting wired networks urgently require advancements in both architecture design and enabling technologies. New optical access systems specifically tailored for the unique natures of various wireless standards are investigated. This dissertation presents the design and experimental verification of high-capacity optical-wireless communication systems using advanced electrical and optical technologies. Technologies such as high level modulation and multiple-input and multiple-output (MIMO) to increase the spectral efficiency is approaching the Shannon limit. New frequency bands with larger bandwidth are to be explored; for example, millimetre wave (mm-wave) spectrum range (30-300 GHz), especially the license-free spectrum located in 60 GHz. Although fiber-optic systems excel in the high-bandwidth core network, as bandwidth demand increases, more and more progress has been made towards the usage of fiber in the last mile. Radio-over-Fiber (RoF) technology has been proposed as a cost-effective optical access solution to support high-speed wireless communications, especially at the mm-wave band. Signal processing and coordination are centralized at the central office (CO), making the system economical and simple to build, operate, and maintain. Moreover, RoF systems are capable of delivering radio signals with different frequencies and protocols simultaneously. Therefore, the advantage of integrated fiber wireless systems leads to the first research topic of this dissertation: multi-band multi-service RoF systems. With an emphasis on the uniformity of the RoF platform that accommodates both legacy wireless services and advanced mm-wave services, the first part of the dissertation presents two schemes - analog all-band RoF and band-mapped 60-GHz RoF - to cover distinct application scenarios. In the all-band RoF access architecture, lower RF signals, such as Wi-Fi and cellular signals, and 60-GHz signal are transmitted at their original carrier frequencies for both indoor and outdoor coverages. On the other hand, the band-mapped mm-wave RoF scheme, fully utilizing the wide 7-GHz bandwidth at 60 GHz, delivers multiple converged high-speed services only through 60-GHz wireless link, which is especially suited for in-building broadband wireless access. The experimental verification of an all-band RoF system featuring relaxed component requirement is introduced, followed by a real-time multi-service demonstration in the proposed band-mapped 60-GHz RoF system. This dissertation also presents the design, analysis, and experimental demonstration of next-generation high-capacity cellular networks to keep up with the ever-growing bandwidth demand and performance requirements. New mobile backhaul (MBH) architectures based on orthogonal frequency division multiple access (OFDMA) are proposed along with a simple and low-latency clock distribution and recovery scheme. The transmission of OFDMA signals in the dense wavelength division multiplexing (DWDM) network with flexible clock rates and DSP-free clock recovery is implemented. Also, a spectrally-efficient, low-complexity clock distribution and recovery scheme for OFDMA-based MBH in coherent ultra-dense WDM (UDWDM) system is demonstrated. Finally, mobile fronthaul (MFH) architectures based on subcarrier multiplexing (SCM) technology, which significantly reduces the requirements on both the number of wavelengths per cell site and the optical bandwidth of the optical transceivers, are systematically investigated. Additionally, two upstream schemes, tailored for the uplink (UL), are introduced to maintain low complexity, and more importantly, to achieve high spectral efficiency by wavelength sharing. Therefore, Internet-access-oriented optical-wireless systems using Wi-Fi and other emerging mm-wave technologies are developed along with the optical fronthaul and backhaul for cellular networks in this dissertation. Moreover, with the proposed techniques, heterogeneous networks can be seamlessly provided even with different services, radio nodes, and performance requirements.

Le réseau d'accès radio centralisé (C-RAN) peut fortement augmenter la capacité des réseaux mobiles. Cependant, la faisabilité de C-RAN est limitée par le débit considérable engendré sur les liaisons de transport, appelées également fronthaul. L'objectif de cette thèse est d'améliorer les performances de C-RAN tout en considérant les limitations du débit sur le frontaul, l'allocation de ressources et l'ordonnancement des utilisateurs.Nous étudions d'abord les séparations fonctionnelles possibles entre les têtes radios distantes (RRH) et les unités de traitement en bande de base (BBU) sur la liaison montante pour réduire le débit de transmission sur le fronthaul : certaines fonctions de couche basse sont déplacées du BBU vers les RRH. Nous fournissons une analyse quantitative des améliorations de performances ainsi obtenues.Nous nous concentrons ensuite sur la transmission coordonnée Multi-point (CoMP) sur le lien descendant. CoMP peut améliorer l'efficacité spectrale mais nécessite une coordination inter-cellule, ce qui est possible uniquement si une capacité fronthaul élevée est disponible. Nous comparons des stratégies de transmission avec et sans coordination inter-cellule. Les résultats de simulation montrent que CoMP doit être préféré pour les utilisateurs situés en bordure de cellule et lorsque la capacité du fronthaul est élevée. Nous en déduisons une stratégie hybride pour laquelle Les utilisateurs sont divisés en deux sous-ensembles en fonction de la puissance du signal. Les utilisateurs situés dans les zones centrales sont servis par un seul RRH avec une coordination simple et ceux en bordure de cellule sont servis en mode CoMP. Cette stratégie hybride constitue un bon compromis entre les débits offerts aux utilisateurs et les débits sur le fronthaul. / Centralized/Cloud Radio Access Network (C-RAN) is a promising mobile network architecture, which can potentially increase the capacity of mobile networks while reducing operators¿ cost and energy consumption. However, the feasibility of C-RAN is limited by the large bit rate requirement in the fronthaul. The objective of this thesis is to improve C-RAN performance while considering fronthaul throughput reduction, fronthaul capacity allocation and users scheduling.We first investigate new functional split architectures between Remote Radio Heads (RRHs) and Baseband Units (BBU) on the uplink to reduce the transmission throughput in fronthaul. Some low layer functions are moved from the BBU to RRHs and a quantitative analysis is provided to illustrate the performance gains. We then focus on Coordinated Multi-point (CoMP) transmissions on the downlink. CoMP can improve spectral efficiency but needs tight coordination between different cells, which is facilitated by C-RAN only if high fronthaul capacity is available. We compare different transmission strategies without and with multi-cell coordination. Simulation results show that CoMP should be preferred for users located in cell edge areas and when fronthaul capacity is high. We propose a hybrid transmission strategy where users are divided into two parts based on statistical Channel State Informations (CSIs). The users located in cell center areas are served by one transmission point with simple coordinated scheduling and those located in cell edge areas are served with CoMP joint transmission. This proposed hybrid transmission strategy offers a good trade-off between users¿ transmission rates and fronthaul capacity cost.

De nos jours, l’architecture du réseau mobile est en pleine évolution pour assurer la montée en débit entre les Centraux (CO) (réseaux coeurs) et différents terminaux comme les mobiles, ordinateurs, tablettes afin de satisfaire les utilisateurs. Pour faire face à ces défis du futur, le réseau C-RAN (Cloud ou Centralized-RAN) est connu comme une solution de la 5G. Dans le contexte C-RAN, toutes les BBUs (Base Band Units) sont centralisées dans le CO, seules les RRH (Remote Radio Head) restent situées à la tête de la station de base (BS). Un nouveau segment entre les BBUs et RRHs apparait nommé « fronthaul ». Il est basé sur des transmissions D-ROF (digital radio-overfiber) et transporte le signal radio numérique à un débit binaire élevé en utilisant le protocole CPRI (Common Public Radio Interface). En prenant en compte le CAPEX et l’OPEX, le projet ANR LAMPION a proposé la technologie RSOA (Reflective Semiconductor Optical Amplifier) auto alimenté afin de rendre la solution plus flexible et s’affranchir d’émetteurs/récepteurs colorés dans le cadre de transmission WDM-PON (Wavelength Division Multiplexing Passive Optical Network). Néanmoins, il est nécessaire d’ajouter un FEC (forward error corrector) dans la transmission pour assurer la qualité de service. Donc l’objectif de cette thèse est de trouver le FEC le plus adéquat à appliquer dans le contexte C-RAN. Nos travaux se sont focalisés sur l’utilisation de codes LDPC, choisis après comparaisons des performances avec les autres types de codes. Nous avons précisé les paramètres (rendement du code, taille de la matrice, cycle, etc.) nécessaires pour les codes LDPC afin d'obtenir les meilleures performances. Les algorithmes LDPC à décisions dures ont été choisis après considération du compromis entre complexités de circuit et performance. Parmi ces algorithmes à décision dures, le GDBF (gradient descent bit-flipping) était la meilleure solution. La prise en compte d’un CAN 2-Bit dans le canal nous a amené à proposer une variante : le BWGDBF (Balanced weighted GDBF). Des optimisations ont également été faites en regard de la convergence de l'algorithme et de la latence. Enfin, nous avons réussi à implémenter notre propre algorithme sur le FPGA Spartan 6 xc6slx16. Plusieurs méthodes ont été proposées pour atteindre une latence de 5 μs souhaitée dans le contexte C-RAN. Cette thèse a été soutenue par le projet ANR LAMPION (Lambada-based Access and Metropolitan Passive Optical networks). / Nowadays, the architecture of the mobile network is in full evolution to ensure the increase in terms of bit rate between the Central (CO) (core networks) and various terminals such as mobiles, computers, tablets in order to satisfy the users. To address these challenges of the future, the C-RAN (Cloud or Centralized-RAN) network is known as a 5G solution. In the C-RAN context, all BBUs (Base Band Units) are centralized in the CO, only the RRH (Remote Radio Head) remain at the head of the base station (BS). A new segment between BBUs and RRHs appears called "fronthaul". It is based on D-ROF (digital radio-overfiber) transmissions and carries the digital radio signal at a high bit rate using the Common Public Radio Interface (CPRI) protocol. Taking into account CAPEX and OPEX, the ANR LAMPION project has proposed the Self-seeded Reflective Semiconductor Optical Amplifier (RSOA) technology in order to make the solution more flexible and overcome the need for colored transmitters / receivers in the context of PON-WDM (Wavelength Division Multiplexing Passive Optical Network). Nevertheless, it is necessary to add a FEC (forward error corrector) in the transmission to ensure the quality of service. So the objective of this thesis is to find the most suitable FEC to apply in the C-RAN context. Our work has focused on the use of LDPC codes, chosen after performance comparisons with other types of codes. We have specified the parameters (code performance, matrix size, cycle, etc.) required for LDPC codes to obtain the best performance. Hard-decision LDPC algorithms were chosen after considering the tradeoff between circuit complexities and performance. Among these hard-decision algorithms, the GDBF (gradient descent bit-flipping) was the best solution. Taking into account a CAN 2-Bit in the channel led us to propose a variant: the BWGDBF (Balanced weighted GDBF). Optimizations have also been made with respect to the convergence of the algorithm and latency. Finally, we managed to implement our own algorithm on the Spartan FPGA 6 xc6slx16. Several methods have been proposed to achieve a latency of 5 μs desired in the C-RAN context. This thesis was supported by the project ANR LAMPION (Lambada-based Access and Metropolitan Passive Optical Networks).

Le Cloud RAN a été préconisé pour la 5G. Cependant, sa mise en place rencontre des difficultés notamment sur l'intégration du fronthaul, ce dernier généralement basé sur l’interface CPRI représente le segment situé entre la Digital Unit et la Radio Unit. Vu les contraintes de débit, de latence et de gigue sur cette interface, le multiplexage en longueur est la solution adéquate pour son transport. En revanche, les technologies radio recommandées pour la 5G augmenteront considérablement les débits CPRI, ce qui rend l’utilisation du WDM bas coût très difficile. Cette thèse traite quatre sujets principaux : L'introduction d'un canal de contrôle dans le CPRI permettrait la supervision de l'infrastructure WDM et l'accordabilité en longueurs d'onde des transceivers. L’impact de l’intégration de ce canal de contrôle dans le fronthaul est étudié dans le chapitre II. La radio analogique sur fibre peut améliorer de manière significative l'efficacité spectrale du fronthaul, permettant potentiellement le transport des interfaces 5G. Une étude approfondie sur le gain réel apporté par cette solution est rapportée dans le chapitre III. La compression du CPRI basée sur la quantification uniforme et non uniforme est également une solution pour améliorer l'efficacité spectrale du CPRI. Le chapitre IV démontre expérimentalement les taux de compression réalisables. Enfin, les nouveaux splits fonctionnels sont considérés comme une solution prometteuse pour la 5G. Deux nouvelles interfaces ont été identifiées pour les splits couche haute et couche basse. Une étude théorique et expérimentale de ces nouvelles interfaces est présentée dans le chapitre V. / Cloud Radio Access Network (RAN) was identified as a key enabler for 5G. Its deployment is however meeting multiple challenges notably in the fronthaul integration, the latter being the segment located between the Digital Unit and the Radio Unit generally based on CPRI. Giving its bit-rate, latency and jitter constrains, Wavelength Division Multiplexing (WDM) is the most adequate solution for its transport. However, the radio technologies recommended for 5G will drastically increase the CPRI bit-rate making its transport very challenging with low-cost WDM. This thesis deals with four main topics : The introduction of a control channel in the CPRI enables offering the WDM infrastructure monitoring and the wavelength tunability in the transceivers. The study of this control channel integration in the fronthaul link is reported in the second chapter as well as an investigation on the wireless transmission of CPRI. The use of Analog Radio over Fiber (A-RoF) can significantly improve the fronthaul spectral efficiency compared to CPRI-based fronthaul enabling, potentially, the transport of 5G interfaces. A thorough investigation on the actual gain brought by this solution is stated in the third chapter. CPRI compression based on uniform and non-uniform quantization is also a solution to enhance the CPRI spectral efficiency. The fourth chapter describes this solution and experimentally shows the achievable compression rates. Finally, establishing a new functional split in the radio equipment was considered as a promising solution for 5G. Two new interfaces have been identified for high and low layer functional splits. A theoretical and experimental study of these new interfaces is reported in the fifth chapter.

Dans les réseaux mobiles du future, un déploiement plus dense des points d’accés radio est prévu pour satisfaire la demande accrue de débit, mais les terminaux utilisateurs peuvent être affectés par une interférence inter-cellulaire plus forte. Par chance, la centralisation des traitements de signal en bande de base dans l’achitecture Cloud RAN (C-RAN) offre la possibilité de la coordination et du traitement conjoint de plusieurs cellules. Pour réellement permettre de déployer ces techniques, une étude bout-à-bout du CRAN est nécessaire selon plusieurs aspects, notamment l’architecture fonctionnelle, la stratégie de coordination, l’implémentation du traitement de signal multiutilisateur et les optimisations possibles pour un fonctionnement plus efficace.Dans cette thèse, nous proposons en premier une architecture qui définit le placement des fonctions du traitement en bande de base entre les unités distribuées et le serveur central. Le but de ce design est de permettre la réalisation des fonctions multi-utilisateurs en transmettant avec la moins de débit possible sur les liens de fronthaul reliant les différentes entités. Dans un second temps, nous présentons comment il est possible de coordiner les différentes cellules servies par le C-RAN en utilisant le concept de réseaux définis par logiciels adapté pour les réseaux d’accès radio. Nous avons mis en place un prototype démontrant la faisabilité de la méthode de contrôle proposée. Finalement, nous étudions l’allocation adaptative du débit sur les liens de fronthaul transportant les symboles numériques quantifiés des utilisateurs en besoin de traitement multi-cellulaire sur la voie montante pour exploiter l’interférence entre eux. Nous proposons un modèle d’optimisation qui inclut le coût des transmissions fronthaul pour maximiser ainsi le gain obtenu par l’opérateur du réseau où la communication multiutilisateur a lieu. Nous réalisons l’optimisation pour différents modèles de coût et en utilisants deux types de données: d’abord les estimations de canal supposées parfaites et disponibles en temps réel, puis seulement les statistiques du canal. Nous montrons que la méthode d’optimisation proposée permet d’exploiter plus efficacement les liens de fronthaul dans l’architecture précedemment définie. / In future mobile networks denser deployment of radio access points is planned to satisfy demand of higher throughput, but an increased number of mobile users can suffer from inter-cell interference. Fortunately, the centralization of base-band processing offered by Cloud Radio Access Network (C-RAN) architecture enables coordination and joint physical layer processing between cells. To make practical deployment of these techniques possible, we have to study C-RAN in an end-to-end view regarding several aspects: the functional architecture of a deployment, the multi-cell coordination strategy, the implementation of multi-user signal processing and possibilities for optimization to increase operational efficiency.In this thesis, first, we propose an architecture defining the placement of base-band processing functions between the distributed remote units and the central processing unit. The aim of this design is to enable multi-cell processing both on the uplink and the downlink while requiring low data rate between the involved entities. Secondly, we study how low latency coordination can be realized inside the central unit using software defined networking adapted to radio access networks. Our demonstration through a real-time prototype deployment shows the feasibility of the proposed control framework. Finally, we investigate adaptive allocation of fronthaul rate that is used for transferring quantized base-band symbols for users participating in uplink multi-cell reception in order to exploit interference between them. We propose an optimization model that includes the cost of fronthaul tranmissions and aims to maximize the gain of network operators from multi-user transmissions in C-RAN. We solve the optimization problem for different fronthaul pricing models, in a scenario where real-time and accurate channel estimates are available and in another where only channel statistics are exploited. Using our method - fitting in the architecture that we have defined - cost efficiency of fronthaul usage can be significantly improved.

In recent years, several studies and simulations have been made on changing the current Radio Access Network (RAN) architecture into a more centralized access network where the base band processing is done in a central oce (CO) instead of out by the antenna site. This new architecture is denoted as the mobile fronthaul and is planned to be in use for the coming 5G network. The studies that have been made so far suggest that the new architecture can reduce cost, power usage and latency which are important factors regarding environmental, economical and data transmission issues. Furthermore, the new architecture allows a smarter distribution of data for each sector covered by the antennas, reducing redundant data transmission and thus increases the data eciency. The disadvantage or challenge however is that some of the optical components will be transferred from the currently controlled environment in the CO to an uncontrolled outdoor environment at the antenna site, which may generate risks as these components may be sensitive to especially changes in temperature. In this master thesis, the optical performance of four di erent passive lter setups, using a thin lm lter (TFF), an arrayed waveguide grating (AWG) and an interleaver, has been studied and compared in order to nd the most suitable lter setup for the mobile fronthaul. These optical parameters include insertion loss, isolation, crosstalk, 3 dB passband, center wavelength drift and also bit error-rate (BER) which have all been measured over a temperature interval of -40-85oC. Moreover, the measurement results have been compared with results from simulations done with VPItransmissionmaker. From the measurement results, the TFF had a better optical performance and reliability compared to the AWG mainly due to a higher isolation and a lower BER penalty of 0.2 dB compared to 0.5-1.5 dB for the AWG. Considering data capacity and economical aspects for a more realistic mobile fronthaul scenario with 80 channels using dense wavelength division multiplexing (DWDM) however, the AWG connected to the interleaver is more benecial without risking negative a ects on trac performance. / Under senare år har flera studier och simulationer utförts med syfte att ändra arkitekturen på dagens radioaccess-nätverk till ett mer centraliserat nätverk där basbandsprocesseringen sker i en central nod istället för ute vid antennen och radiomasterna. Denna nya arkitektur kallas mobile fronthaul och planeras att realiseras till 5G-nätet. De studier som har gjorts hittills indikerar på att den nya arkitekturen kan minska ekonomiska kostnader, elanvändningen och latens vilka är viktiga faktorer som bland annat rör miljö-, ekonomi och kapacitetrelaterade områden. Dessutom kan data fördelas på ett smartare sätt över alla delområden som antennerna täcker vilket minskar redundant datatrafik och därmed ökar den effektiva mängden data som skickas ut. Problemet eller utmaningen är att vissa optiska komponenter behöver flyttas från en nuvarande kontrollerad miljö till en okontrollerad utemiljö vid radiomasterna vilket kan medföra risker då dessa komponenter främst kan vara väldigt temperaturkänsliga. Inom detta examensarbete har optisk prestanda studerats, analyserats och jämförts mellan fyra olika filterkonstellationer bestående av ett tunnfilmsfilter, ett AWG-filter och en interleaver med syfte att finna vilken konstellation som passar bäst för mobile fronthaularkitekturen. De optiska parametrarna består av insertionsförluster, isolation, överhörningsinterferens, 3 dB-passband, centervåglängdsdrift samt bitfelsgrad vilka alla har blivit undersökta över ett temperaturintervall på -40-85oC. Utöver detta så har mätresultaten jämförts med simulationer gjorda med VPItransmissionmaker. Utifrån mätresultaten kunde det konstateras att tunnfilmfiltret hade bättre optiska egenskaper och även högre trovärdighet jämfört med AWG-filtret främst på grund av en högre isolation och lägre bitfelsgradsstraff på 0.2 dB jämfört med 0.5-1.5 dB för AWG-filtret. Om en endast avväger datakapacitet och ekonomiska aspekter för ett mer realistiskt scenario för mobile fronthaul med 80 DWDM-kanaler så är AWG-filtret tillsammans med interleavern mer foördelaktig att välja utan att riskera några negativa påverkningar på trafikprestandan.

Cellular networks have significantly transformed the way we communicate and access data and the data rates have only been increasing for the last 30 years. 5G is the current generation of cellular networks and enables faster data rates and lower latency. One of the cellular network architectures used to enable 5g is centralized radio access networks (C-RAN). C-RAN centralizes all the baseband units (BBU) into one or a few locations in contrast to traditional architectures where BBUs are separated. This centralization causes more demand on the fronthaul to transfer larger amounts of data. To mitigate this demand on the fronthaul, functional splits were developed to distribute the baseband functions dependent on the need. This thesis focuses on simulating several functional splits in C-RAN with packetized fronthaul. The objective is to study the impact the functional split options have on the network by investigating key metrics such as fronthaul link throughput, utilization, and, buffer usage. The thesis includes the development of a digital twin (DT) of C-RAN deployments. This digital twin is implemented in Python using the SimPy library to enable discrete event simulation. The DT was then used to simulate each split option over low, medium, and high traffic loads. The network that was simulated includes one BBU, fronthual link, one switch, and three remote radio units with 64 antennas. The fronthaul link is 1 km long and has a transfer rate of 100 Gbps. The results show that various functional split options have a significant impact on the network’s overall performance. This impact is mostly dependent on the split option choice and not on the load for this configuration. Overall, this thesis contributes to the understanding of functional splits in centralized radio access networks with packetized fronthaul. / Mobilnäten har förändrat hur vi kommunicerar och får tillgång till data, och datahastigheterna har bara ökat under de senaste 30 åren. 5G är den nuvarande generationen av mobilnät och möjliggör snabbare datahastigheter och lägre latens. En av de mobilnät arkitekturer som används för att möjliggöra 5g är centraliserade radioaccessnät (C-RAN). C-RAN centraliserar alla basbandsenheter (BBU) till en eller ett mindre antal platser i motsats till traditionella arkitekturer där BBU är separerade. Denna centralisering leder till att fronthaul länken belastas mer för att överföra större data mängder. För att minska denna belastning på fronthaul länken kan funktionella uppdelningar användas för att distribuera basbandsfunktionerna beroende på behov. Det här arbetet fokuserar på att simulera flera funktionella uppdelningar i centraliserade radio radioaccessnätvärk med paketerad fronthaul. Syftet är att studera vilken påvärkan de funktionella uppdelnings alternativen har på nätverket genom att undersöka och mäta värden som genomströmning, utnyttjande av fronthaul kabel och buffertanvändning i fronthaulen. I arbetet inkluderar utvecklingen av en digital tvilling (DT) av C-RAN. Denna digitala tvilling implementeras i Python med hjälp av SimPy-biblioteket för att möjliggöra discrete event simulation"vilket betyder simulering av diskreta händelser. DT användes sedan för att simulera varje uppdelnings alternativ över låg, medelhög och hög trafikbelastning. Nätverket som simulerades inkluderar en badeband unit (BBH), en fronthual länk, en switch och tre remote radio unit (RRU) med 64 antenner. Fronthaul länken är 1 km lång och har en överföringshastighet på 100 Gbps. Resultaten visar att olika uppdelningar har en betydande påvärkan på nätverkets övergripande prestanda. Denna påverkan beror främst på valet av delningsalternativet och inte av belastningen för denna konfiguration.svis så bidrar detta arbete till förståelsen av funktionella delningar i centraliserade radioaccessnät radioaccessnät med paketerad fronthaul i olika trafikbelastningar.

In centralized radio access network (C-RAN) architecture, the base-band unit (BBU) is connected to one or more remote radio units (RRUs) via a fronthaul (FH) interface. Upgrading base station antennas in C-RAN to support massive multiple-input multiple-output (MIMO) technology can improve network spectral efficiency and largely boost the capacity of the 5G system. Those great benefits also introduce new challenges to the FH interface since the required FH capacity increases proportionally to the number of transceiver units (TXRUs) for traditional receiver processing at the BBU. To reduce the FH link load, different base-band splitting options between RRUs and BBU are considered in practical C-RAN networks. In this project, we investigate three beamforming algorithms (MRC, DFT and Enhanced) which are expected to reduce the number of streams on FH link, and evaluate their performance for single-user MIMO in different mobility scenarios via system-level simulations. The results show that we successfully reach the goal of reducing the number of streams to one-fourth the number of TXRUs meanwhile maintaining relatively good performance. Additionally, we observe that the Enhanced algorithm performs the best in majority of scenarios. / I en centraliserad nätverksarkitektur för radioåtkomst är basbandsenheten ansluten till en eller flera fjärrradionheter via ett fronthaul-gränssnitt. Genom att uppgradera basstationsantennerna i C-RAN för att stödja massiv multipel input-multipel output-teknik kan man förbättra nätverkets spektraleffektivitet och till stor del öka kapaciteten i 5G-systemet. Dessa stora fördelar medför också nya utmaningar för FH-gränssnittet eftersom den nödvändiga FH-kapaciteten ökar proportionellt mot antalet sändare för traditionell mottagarbearbetning vid BBU. För att minska belastningen på FH-länken övervägs olika alternativ för uppdelning av basbandet mellan RRUs och BBU i praktiska C-RAN-nät. I det här projektet undersöker vi tre strålformningsalgoritmer (MRC, DFT och Enhanced) som förväntas minska antalet strömmar på FH-länken och utvärderar deras prestanda för single-user MIMO i olika mobilitetsscenarier med hjälp av simuleringar på systemnivå. Resultaten visar att vi lyckas uppnå målet att minska antalet strömmar till en fjärdedel av antalet TXRU:s samtidigt som vi behåller en relativt god prestanda. Dessutom kan vi konstatera att den förbättrade algoritmen presterar bäst i de flesta scenarier.