This thesis investigates methods to enhance the robustness of KPN's network. As reliance on telecom networks grows, improving network resilience is paramount. Two primary strategies exist: minimizing failure occurrence and mitigating failure impact. This research focuses on the latter, specifically increasing network redundancy by transforming existing ring structures into strand structures.

Current ring structures in the network avoid single points of failure (SPOFs) at the link level but fail to address node-level SPOFs, particularly at Metro Core (MC) locations. MC locations are pivotal, as they manage customer sessions and route all household network traffic. Node failures at these locations can disrupt connections for up to 100,000 households. Thus, ensuring that a single node-level failure can be compensated by another node is crucial. This requires considering both equipment and building failures, with geographically distant backup nodes necessary for the latter.

Transforming rings into strands, which inherently include two geographically separated MC locations, addresses these issues but incurs significant costs. While an exact cost estimation is beyond the scope of this research, the study approximates the length of additional cables required, totaling 206 kilometers. Including cost multipliers for tunnels, bridges, and highways, the adjusted length is equivalent to 222 'kilometers' of cable. Despite the substantial cost, node failures at the equipment level, which are more common, can be mitigated with redundant equipment at MC locations. Therefore, a cost-effective alternative might be forming strands only where rings from different access areas are already in proximity.

As digital communication networks become integral to society and the economy—driving everything from personal communication to business operations and smart city infrastructure—the capacity of these networks must continuously expand to accommodate higher data volumes. The Ericsson Mobility Report demonstrates the growing need for higher throughput and increased network capacity to meet end-user expectations. One of the viable approaches to increase network capacity is through the deployment of small cells.
In general, the related axioma is: the higher the offered bandwidth (higher radio frequencies), the shorter the radio ranges will be. Small cells provide additional capacity (preferably) by means of high-frequency bands such as 3.5 GHz and 26 GHz offloading the macro network in particular short-range hotspots. Small cells can deliver higher data rates to end users, making their deployment essential at hotspots in densely populated urban areas where additional capacity will be required. This master’s thesis evaluates Radio Access Network (RAN) architecture options for combining macro cells and small cells from both theoretical and practical perspectives.

The main finding from the Radio Access Network-related theoretical analysis is that the RAN architecture split option 7.2x recommended by the O-RAN Alliance is the optimal solution for indoor and outdoor deployment of small cells. Split option 7.2x offers significant benefits, such as minimising the impact on transport bandwidth while enhancing the virtualisation capabilities of the gNB Central Unit (CU) and Distributed Unit (DU), and enabling a cost-effective design of the Radio Unit (RU).


To gain an understanding of the practicalities involved in small cell deployment, this master thesis, through the Utrecht practical case study, examines potential locations for the installation of RUs, DUs, and CUs using a combination of expert interviews, Google Street View analysis, QGIS visualisations, and site visits. Proposed locations for RUs include three tall lamp posts and two security camera poles, while wharf cellars managed by Stedin and a macro cell base station are recommended for the installation of CUs and DUs. These recommendations are based on an analysis of power availability, transport, site accessibility and expert interviews. From the research it is concluded that small cell deployment in the Utrecht researched area is feasible, provided that specific challenging boundary conditions are met such as collaboration among MNOs and the use of existing poles.

The practical part of this thesis research also delves into the complex interplay of eight socioeconomic sectors and their roles in small cell deployment, providing insights into the trans-sector nature of this project.
The main results from this practical part of the research concern the conclusions from the Utrecht practical case study about realizing small cells:
The main results from this practical part of the research concern the conclusions from the Utrecht practical case study about realizing small cells:
1. The rollout of small cells is a complex multi-actor value case with substantially more actors to collaborate in comparison with rolling out macro cells by primarily telecom operators and municipalities (issuing licenses).
2. Municipalities are best suited to fulfil the role of orchestrator in the rollout of small cells because they can coordinate diverse stakeholders to ensure seamless integration with existing infrastructure, maintain city aesthetics and establish a direct line of communication with residents for feedback and service improvement.
Based on some representative calculations of small cell deployments in the city of Utrecht we obtained good insight into the complexity as well as cost of small cells. A few of the quantitative results are mentioned below:
•The price of a small cell is roughly around €60,000 per small cell site, including digging for transmission and power costs.
•In case the fronthaul is replaced by a wireless connection, roughly 30% of cost savings can be achieved.

This thesis titled ´Study of 5G Roaming Security´ investigates the potential network vulnerabilities of 5G roaming reference points. The 5G Non-Standalone (NSA) is already being deployed in different countries across the world. With 3G becoming obsolete, mobile communication will primarily depend on 4G and 5G-NSA. In the later stages of the 5G rollout, 5G Standalone (SA) deployment will also take place gradually. Since 5G will support various use cases such as connected vehicles, smart farming, and smart healthcare, the number of connected devices will eventually increase. This would mean more data traffic generation compared to the LTE. In such a scenario, the privacy protection of the User Plane becomes highly significant. This thesis work provides a randomization-based security solution that would make the Standalone 5G reference points more robust to interception attacks.

The goal is to implement a negotiation-based randomization solution over N9, N3, and N32 as these reference points cross the HPLMN boundary. This solution will be a part of the GTP-U header and can be easily implemented by modifying the existing signaling procedures. Random bytes will be added to the GTP-U header before the start of the payload. The idea of adding randomization bytes has been extended to include TCP-based randomization and IMS-based randomization. The TCP-based randomization also includes two different algorithms for the addition of random bytes. After analyzing the User Plane security, the vulnerability analysis of SEPP was undertaken, to understand the vulnerabilities that can be a threat to the network infrastructure. A vulnerability assessment matrix was made and high-risk vulnerabilities were highlighted along with a few precautionary steps. The implementation details and architectural changes for the implementation of GTP and TCP-based randomization are provided. The randomization is useful in masking the signature distribution of an application's packet length and can be a powerful protection mechanism against data traffic analysis attacks.

This thesis’ research concerns the time-dynamics of a complex geographical network of municipalities, i.e. the Dutch Municipality Network over the period 1830-2019. By analysing 190 years of socioeconomic statistical data and applying contemporary tooling from network science and geographic information systems (GIS), the findings from this research can provide a new approach and supportive methods for policymakers, statistical offices, researchers and businesses (to decide when and where to invest).

The thesis focuses on investigating the role of IP Multimedia Subsystem (IMS) in 5G networks. IMS already plays a very important role in enabling a wide range of real-time multimedia communication services such as basic phone calls and messaging in the LTE network. Addition of application servers on top of the IMS core can provide enhanced functionalities like presence, advanced messaging and SIP trunking. IMS guarantees quality, security and reliability of multimedia services when serving users without the installation of any application as well as flexibility over access. This sets IMS apart from other third party applications found on the internet. IMS was created with the idea of being adaptable to the evolving technology. With the implementation of the 5G network underway, a study of the impact of this new architecture on the IMS services is imminent. The thesis focuses on the study of different network elements participating in an IMS service as well as investigating IMS voice and video calls over the 5G network.
The thesis consists of two parts: The first part involves exploring the role of IMS in 5G networks. A brief overview of the evolution of mobile networks will help understand the differences between 1G/2G/3G/4G. Following this, IMS and its role in enabling multimedia services in the LTE network is explored. Next, the 5G System Architecture is explained along with components and their functions.
Next, a comparison between the elements in 4G and 5G provides a clear understanding of the technological evolution and the procedure involved. The next steps would include understanding the IMS call flow in LTE networks. This would provide a good foundation to understand how the IMS services will be provided over the 5G network. The second part of the thesis includes testing the voice and video services over Ericsson’s 5G network at their Rijen office. As a starting step, the voice and video services are tested using WebRTC. Upon succeeding in the peer-to-peer test, the next step is establishing connectivity to Ericsson’s IMS network at Kista, Sweden. This will allow the testing of IMS voice and video services over the 5G network. The results are recorded and analysed. These are in agreement with the theoretical expectations.

Narrowband Internet-of-Things (NB-IoT), recently introduced by 3GPP, is a relevant Radio Access Technology (RAT) solution for deployment within smart grids, the electricity grids of the future, due to the need to provide low-cost connectivity to a large number of smart meters installed in households. Outage Restoration and Management (ORM), a smart grid use case, involves the smart meter User Equipment (UE) sending a notification message to the utility upon the detection of a loss or restoration of power. ORM is an effective way for utilities to quickly detect, localise and restore a power outage. However, depending on the extent of the power outage, a near simultaneous network access by multiple UEs may occur, leading to resource congestion, particularly of the so-called ‘random access channel’. This may impact the reliability, i.e. the percentage of total notifications successfully delivered within a certain transfer delay target, and in turn, the accuracy of the power outage localisation. Consequently, the maximisation of the ORM reliability performance for a technology like NB-IoT becomes a challenge, given that such use cases, though relevant, were not considered in its design phase.
The main goal of this thesis is the optimisation of the NB-IoT network configuration, with a focus on packet scheduling, in order to maximise the ORM reliability performance. To this extent, a system-level simulation model is developed and implemented, incorporating realistic characteristics of energy distribution and mobile networks in four different environments (rural, suburban, urban and dense urban), the traffic characteristics of ORM and the relevant 3GPP specifications of NB-IoT. Additionally, a set of candidate time-frequency domain packet schedulers are proposed. A sensitivity analysis of key network configuration components is performed for a set of power outage scenarios i.e. network loads, the associated optimisation trade-offs are highlighted and a near-optimal network configuration is derived.
Based on the sensitivity analysis, a proposed scheduler which prioritises UEs based on a combination of the Earliest Due Date First (EDDF) and Shortest Processing Time First (SPTF) principles, and assigns each UE a single uplink subcarrier with a subcarrier spacing of 3.75 kHz, performs best amongst all the candidate schedulers. Furthermore, the achieved reliability performance is close to 100% for all the considered power outage scenarios in the rural and dense urban environments. In the suburban and urban environments, close to 100% reliability is achieved for the majority of the power outage scenarios.