Mantra: 3GPP has defined 5G Phase 1 in Release 15 and has been working on 5G Phase 2 in Release 16.
Explanation: To accelerate time-to-market, 3GPP adopted divide-and-conquer approach and has worked on 5G specification in phases. 5G Phase 1 has been fully defined in Release 15 with support for NSA NR with the EPC (e.g., Option 3x architecture) and SA NR with the 5GC (e.g., Option 2 architecture), Network Slicing, flexible NR air interface, and so on. 5G Phase 2 focuses on more complex features such as URLLC enhancements, NR-Unlicensed, and Integrated Access and Backhaul.