Flexible and Programmable 5G Transport Networks

University dissertation from KTH Royal Institute of Technology

Abstract: The advent of 5th generation of mobile networks (5G) will not only require the upgrade of the radio access segment of the network, but will also introduce some new challenges for the transport network. Different strategies can be employed by the network providers to address these challenges with the aim to achieve an efficient utilization of network resources, and to keep the network power consumption and cost to a similar level as today’s networks. The most feasible option to achieve these goals is to introduce intelligence in the transport infrastructure by designing a flexible and programmable transport network. This can be achieved thanks to the ability to jointly orchestrate radio and transport domains that will allow network providers to allocate the resources dynamically, according to variation of traffic demand.Network function virtualization (NFV) and dynamic resource sharing (DRS) are two possible techniques for realizing a flexible transport network. NFV allows to dynamically push network functions to different locations in the network, while DRS allows for sharing transport resources in a flexible manner. Both of these strategies can be realized by employing a programmable control framework based on software defined networking (SDN), which has implications on both the network data and control planes. For this reason, it is crucial to investigate both the data and the control plane aspects of these strategies. However, this thesis specifically focuses on the data plane aspects of NFV and the control plane aspects of DRS.Considering the network caching as a specific example of network function, the data plane aspects of NFV are studied in terms of different architectural options for cache placement in order to see which options are the most efficient in terms of network power consumption and cost. The results presented in this thesis show that it is not very efficient to place a small-sized cache for each small group of users in their close proximity. Instead, placing large-sized caches further down in the network for a large group of users is a more efficient approach.The control plane aspects of DRS are analyzed in terms of which provisioning strategy should be used for sharing a limited amount of transport resources. The analysis is presented for both a single-tenant case (i.e., where the role of service and network provider is played by the same entity), and a multi-tenant case (i.e., where a network provider manages the resources assigned to different service providers in an intelligent way).For the single-tenant case, this thesis proposes a DRS strategy for a centralized radio access network with optical transport. In this scenario, the transport resources are dynamically shared among different radio base stations (RBSs) according to the temporal and spatial variations of wireless traffic requirements of the RBSs. The simulation and emulation results presented in this thesis show that this scheme results in a saving of up to 31.4% of transport resources as compared to a conventional overprovisioning approach.For the multi-tenant case, this thesis proposes a strategy where the network resources are dynamically shared among different types of clients, by taking into account the temporal variation in service requirements of the clients. The results obtained after solving mixed integer linear programming (MILP) formulations for the proposed scheme show that it performs much better than the conventional static slicing approach (i.e., without sharing of resources), which translates into significant cost savings for the network providers.In summary, this thesis analyses different aspects of NFV and DRS which are considered to be quite promising solutions for addressing the 5G transport challenges. It demonstrates that by introducing flexibility and programmability in the transport infrastructure through these schemes, the network resources can be utilized more efficiently which can enable the network providers to lower their costs significantly.