Software defined 5G networks for anything as a service [Guest Editorial]

The advanced fifth generation (5G) infrastructure is expected to become the ???nervous system??? of the digital society, digital economy, and silver economy. New service paradigms such as ???immersive experience??? and ???anything as a service??? (XaaS) everywhere are envisioned as among the primary drivers for global adoption and market uptake of new 5G technology components. Above all, 5G networks will support mission-critical machine communications and massive machine type of traffic. As a result, the key performance metrics that 5G is expected to improve are in terms of, but not limited to, latency, reliability, capacity, and spectrum and network agility. This calls for a complete rethinking of all functional domains, including access stratum (AS), non-access stratum (NAS), and transport network layer (TNL), in terms of protocols and procedures. New emerging technologies, such as software defined networking (SDN), network functions virtualization (NFV), mobile edge computing (MEC), and high-performance computing (HPC), provide momentum for new design principles toward software (service) defined 5G networks, targeting a software defined air interface (SDAI) for available bands (spectrum); sliced "networks on demand" for multiple industries, especially for vertical markets (new architecture); and flexibility and spectral efficiency for mobile broadband and machine type communications (new air interface).