## 6 Conclusions  
The virtualization of the structure of a satellite-borne base station system and the transformation of hardware products to firmware and software applications have made the structure of the satellite infrastructure simple and cost-effective, and the service provision more dynamic and efficient, enabling satellite network operators to achieve rapid demand fulfillment, flexible resource scheduling, effective cost control, significant performance  
Figure 8: Comparison of average single migration costs.  
Figure 7: Comparison of resource usage of migration destination nodes.  
improvements and green network intensification. This paper proposes an architecture for a horizontal shared virtual network that converges computing, communication, and storage. Through the constructed verification environment and comparison between a traditional satellite base station system and the virtualization satellite-borne base station in terms of deployment time and reconfiguration time, it was shown that the virtualization architecture had big advantages in flexibility and reconfigurability of the satellite-borne base station system.  
This paper also proposes a VNF multi-domain resource-aware migration algorithm based on the collaboration of migration precomputation and real-time computation, which senses the resource occupation of overloaded nodes by the RAIL algorithm and selects VNFs to migrate out. Based on the resource requirements of the VNF and the end-to-end performance constraints of the SFC, TOPSIS was used for multi-objective decision-making to achieve better network balancing. This algorithm realized the rapid deployment of a digital satellite-borne base station system network and improved the stability of the system in the satellite environment.  
The simulation results demonstrate that the VNF multi-domain resource-aware migration algorithm using migration precomputation in conjunction with real-time computation can improve system stability while minimizing migration overhead, select the best migration destination nodes, reduce the overall number of system migrations, and improve the stability of the system.  
After an architecture of a horizontal shared virtual network has been designed and also the problem of VNF migration time under this architecture is fixed, it will be possible to deploy network functions on an LEO satellite as we wish. So, future work on how to deploy the network function appropriately to maximize the performance of the system should be conducted. For example, the questions of to optimize the design and deploy the network function (NF) on an LEO satellite according to the LEO satellite dynamics and communication requirements to achieve the goal of reducing signaling transmission time should be solved. This will enable finding the most appropriate service function chain (SFC) for users in an LEO satellite constellation. Based on the architecture to improve the performance of the LEO satellite system, other system indicators also can be optimized, except for the signal transmission time.  
Conceptualization, Y.S. and X.Z. Formal Analysis, Y.S. and P.W. Supervision, X.Z. and H.Z. All authors have read and agreed to the published version of the manuscript. This work was supported in part by Natural Science Foundation of China (92067101, 92067201) and in part by the Key R&D plan of Jiangsu Province (BE2021013-3). Not applicable. Not applicable. Not applicable. Not applicable. Not applicable. Not applicable.  
The authors declare no conflict of interest.