Virtualized Service Orchestration in Space-Air-Ground Integrated Networks: Challenges and Future Directions

The rapid advancement of Space-Air-Ground Integrated Networks (SAGIN), underpinned by Network Functions Virtualization (NFV), is unlocking unprecedented potential for service-oriented SAGINs. The on-demand and cost-effective delivery of virtualized services is becoming a cornerstone for realizing the full vision of truly ubiquitous access to customized applications globally. Nevertheless, flexibly orchestrating these services presents a formidable challenge, primarily due to the inherent heterogeneity and high dynamics of the SAGIN environment. While a great deal of research has been dedicated to this area, existing solutions often fall short, leaving several critical issues unaddressed. In this article, we identify and dissect four key challenges by analyzing current virtualized service orchestration schemes. To illustrate their impacts, we present a series of case studies based on realistic simulations using data from operational satellite constellations. Building on this analysis, we then chart several promising future research directions aimed at enabling more stable, resilient, and intelligent service orchestration in future SAGINs.