Domenico Verde’s thesis, submitted for the completion of a master’s degree in computer engineering in March 2023, focuses on 5G, which stands as the latest innovation in cellular mobile networks. Despite various conspiracies opposing the introduction of 5G networks, multiple studies clearly show how such a change can bring significant economic benefits across various sectors, while also providing users with a better user experience compared to currently existing networks. A fifth-generation network is essentially built upon innovative computer concepts such as Network Functions Virtualization and Software Defined Networking. Furthermore, a fifth-generation network can serve as the enabling support for new technologies based on Artificial Intelligence and/or Machine Learning, as well as for the realization of the Internet-of-Things.
Starting from 2020, several Italian telecommunications operators have begun launching 5G coverage services and various devices compatible with this technology. However, all the anticipated benefits and innovations of a 5G network are not currently implemented in these commercial products. One of the most peculiar features of a fifth-generation network is the functionality of Access Traffic Steering, Splitting, and Switching (ATSSS). This functionality allows users to connect to the network not only using the radio interface (cell), but also, for example, through a WiFi access point (public or private), and to use both connected channels for transmitting and receiving calls, SMS, or internet data.
The primary objective of this work is to optimize, through the creation of an appropriate simulation testbed, the performance of a satellite link in a 5G network for ATSSS. In the first theoretical part of the thesis, the architecture of a 5G network and the main procedures allowing access to the services offered by the network, both through standard radio access (3GPP) and non-standard access (Non-3GPP, such as WiFi or satellite), are described. In the second experimental part, the work done to create a simulation testbed for ATSSS is described.
For the emulation of a 3GPP access, existing open-source software (Free5GC and UERANSIM) was properly configured within virtual machines managed through the KVM/QEMU hypervisor. For the emulation of a Non-3GPP access, however, given the absence of existing technologies, it was necessary to implement a dedicated UE capable of supporting the main procedures to allow a user to access the network (registration, authentication, and PDU session establishment). The UE, developed using the Go programming language, was then subjected to a careful validation phase and proved to be perfectly compatible with the Free5GC core network emulation software. Subsequently, a satellite network was appropriately inserted between the UE and the Core Network, emulated using a pre-installed version of the open-source software Opensand.
Finally, for the realization of the testbed for ATSSS, the implementation of the Multi-Path TCP protocol present in the Linux Kernel 5.15 was used. In this last part, an analysis of performance in terms of latency, jitter, losses, and throughput was also included, both in the case of using a satellite Non-3GPP access network and in the case of using a terrestrial Non-3GPP access network. The work concludes by observing that it is possible to integrate a satellite channel as a Non3GPP access network in a 5G network, but it is only possible to fully exploit its advantages by properly configuring the buffers used in transmission and reception. Additionally, the MP-TCP protocol can be used for the realization of ATSSS in two alternative configurations: in the case of using the satellite link as a backup channel, the entire system assumes greater reliability and therefore greater resistance to network component failures; in the case of using the satellite channel simultaneously with the 3GPP channel in transmission or reception, the overall system throughput is maximized compared to using only the standard 3GPP access.