On the Optimal Deployment of Virtual Network Functions in Non-Terrestrial Segments

In the upcoming Sixth-Generation (6G) of mobile communication systems, space network entities will cooperate with conventional terrestrial networks to provide three-dimensional wireless connectivity around the World. By considering the resulting massive amount of data to be managed into non-terrestrial segments, it will be necessary to dynamically configure functionalities across space network entities. Preliminary contributions in this context focus on quasi-static scenarios, while ignoring the challenging issues (i.e., intermittent visibility, dynamic network configuration, and communication delays) introduced by satellites’ movement and communication protocols enabling the integration of terrestrial and non-terrestrial networks. To bridge this gap, this work presents a network architecture with novel orchestration capabilities of services into non-terrestrial segments. In the proposed approach, the interaction between terrestrial and non-terrestrial entities and the cloud has been detailed across service request, configuration, and provisioning phases. Then, starting from a system model describing the network configuration and the resulting deployment delays of services, an optimization problem has been formulated to dynamically allocate Virtual Network Functions (VNFs) among LEO CubeSats over a looking-ahead horizon, based on service requests, computational capabilities of the involved CubeSats, visibility matrices, and expected deployment delay bounds. Finally, the proposed optimization problem has been solved through three heuristic strategies. Computer simulations have been carried out to demonstrate the ability of the developed strategies to achieve results close to the optimal solution and to ensure better performance against a benchmark scheme.

I. Introduction

While the Fifth-Generation (5G) of mobile communication systems are being deployed in many parts of the World, recent research interests are moving towards the Sixth-Generation (6G) of mobile networks [1]. At the time of this writing, there already exists a common consensus that 6G networks will target the very ambitious goal to realize a Ubiquitous Intelligent Mobile Society, based on scalable and effective fruition of connectivity and computing services on demand, and wherever needed [2]. To this end, Non-Terrestrial Network (NTN) entities will cooperate with conventional terrestrial networks to provide three-dimensional wireless connectivity, also covering deserts, forests, and oceans [3], [4].