ance. In phase 1, both non-standalone and standalone operations of NR were spec- ified. Non-standalone operation was specified in the early timing of Release 15. Standalone-specific functionalities were specified in the later timing of Release 15 to keep functional commonalities between non-standalone and standalone operations as much as possible. In addition, 3GPP allows late drop of Release 15 specifications to take care of addi- tional migration network architectures such as NR-NR dual connectivity. Release 16 specification work started in mid-2018 targeting completion at the begin- ning of 2020. In Release 16, new functionalities for carried out use cases and features from Release 15 are addressed to cover all of the identified usage scenarios and require- ments, as covered in Chapter 15. Release 17 standardization work is then slated to start during 1H/2020 and to be completed by mid-2021, with 3GPP scheduled to concluded in regard to the content in December 2019. 3GPP Release 15 specifications took some time to mature after the first specifi- cations were published in December 2017. The NR non-standalone specifications 2 5G Targets and Standardization 2017 (Calendar Year) Release 15 Release 16 Rel-15 NR non- Rel-16 NR specification standalone specification Rel-15 NR standalone specification Rel-15 NR late drop specification Rel-15 LTE enhancement Rel-16 LTE enhancement specification specification 5G Phase 1 5G Phase 2 Figure 2.3 3GPP schedule related to NR access technology specification work. 5G NR NSA 5G NR SA 5G NR late completion completion Stage 3 completion for NSA Option 3 Stage 3 Rel-15 ASN.1 for Stage 3 Rel-15 ASN.1 for Non-Standalone 5G-NR family ASN.1 completion for SA completion for late drop late drop BC changes SA Option 2 NBC changes + critical CRs ASN.1_December NSA Option 3 ASN.1_June BC changes SA Option 2 SA implementation + critical CRs ASN.1_March baseline NBC changes NSA Option 3 ASN.1_September Backwards Compatible changes + some critical CRs NSA Option 3 NSA implementation ASN.1_Dece