Radio Access and Core Functionalities in Self-deployable Mobile Networks. (Accès radio et fonctionnalités cœurs dans les réseaux mobiles auto-déployables)

Self-deployable mobile networks are a novel family of cellular networks, that can be rapidly deployed, easily installed, and operated on demand, anywhere, anytime. They target diverse use cases and provide network services when the classical network fails, is not suitable, or simply does not exist: for example, when the network saturates during crowded events, when first responders need private broadband communication in disaster-relief and mission-critical situations, or when there is no infrastructure in areas with low population density. These networks are challenging a long-standing vision of cellular networks. Indeed, classical cellular networks are the result of careful planning and deployment strategies. Their fixed and hierarchical architecture is based on a clear physical separation between the radio access network (RAN) and the core network (CN), with an over-provisioned backhaul between them. On the contrary, the rapid deployment nature of self-deployable networks short-circuits the thorough planning phase. The network needs to self-configure and self-organize. Moreover, the split between the RAN and the CN is only functional. In fact, in addition to providing typical RAN functionalities, such as radio signal processing and radio resource management, a base station can also provide those of the CN, such as session management, routing, and authentication, in addition to housing application servers, based on virtualization technologies. As a result, a base station with no backhaul connection to a traditional CN is capable of providing local services to users in its vicinity. To cover larger areas, several base stations must interconnect. With the CN functions co-located with the RAN, the links interconnecting the BSs form the backhaul network. Being setup by the BSs, potentially in an ad hoc manner, the latter may have a limited bandwidth. In this thesis, we build on the properties distinguishing self-deployable networks to revisit classical RAN problems but in the self-deployable context, and address the novel challenges created by the core network architecture. Starting with the RAN configuration, we propose an algorithm that sets a frequency and power allocation scheme. The latter outperforms conventional frequency reuse schemes in terms of the achieved user throughput, and is robust facing variations in the number of users and their distribution in the network. Once the RAN is configured, we move to the CN organization, and address both centralized and distributed CN functions placements. For the centralized placement, building on the shortages of state of the art metrics, we propose a novel centrality metric that places the functions in a way that maximizes the traffic that can be exchanged in the network. For the distributed placement, we evaluate the number of needed instances of the CN functions and their optimal placement, taking into account the impact on the backhaul bandwidth. We further highlight the advantages of distributing CN functions, from a backhaul point of view. Accordingly, we tackle the user attachment problem to determine the CN instances serving each user when the former are distributed. Finally, with the network ready to operate, and users starting to arrive, we tackle the user association problem. We propose a novel network-aware association policy adapted to the self-deployable network attributes, that outperforms a traditional RAN-based policy. It jointly accounts for the downlink, the uplink, the backhaul and the user throughput request, and mitigates both RAN and backhaul bottlenecks.