Learning-Assisted Dynamic VNF Selection and Chaining for 6G Satellite-Ground Integrated Networks

The sixth generation (6G) mobile communication system is expected to provide global seamless network coverages, where a satellite-ground integrated network (SGIN) is seen as one of the typical 6G networking paradigms. In this paper, a dynamic virtual network function (VNF) selection and chaining (DVSC) problem in an SGIN is investigated. We aim to balance the network resource provisioning and VNF migration costs with service performance gain to maximize the long-term network profit. Specifically, we formulate the DVSC problem as a Markov decision process (MDP), by taking into consideration the heterogeneity and time-varying nature of SGINs. A novel VNF selection and chaining scheme is proposed, where a deep Q-learning (DQL) algorithm is designed to dynamically determine a set of VNF selection and chaining policies (VSCPs) based on the evolving network states (e.g., network resources, network topology, and network traffic load). Furthermore, to elaborate the level of computing resource sharing of VSCP sets, a new sharing ratio (SR) is proposed. To efficiently allocate heterogeneous network resources, the action space is built by clustering the historical records of the network load and selecting the VSCP set for each cluster in a greedy manner. Extensive simulation results are presented to demonstrate the effectiveness of the proposed framework in comparison with the state-of-the-art schemes.