mber baseline Backwards Compatible changes NSA Option 3 + some CRs ASN.1_March Figure 2.4 Release 15 NR specification stability. of the first version of ASN.1 was completed in March 2018, and it experienced non-backward-compatible (NBC) changes until September 2018 as indicated in Figure 2.4. For the December 2018 version, the protocol remained backward compat- ible (and is maintained backward compatible in 2019 as well). The December 2018 version required some corrections to reflect some important items like finalization of the user equipment (UE) capabilities in terms of which features the UEs are required to support and which they are not. This requires the functionality from December 2018 to be taken into account in the commercial implementations. December 2018 is thus the References required baseline for commercial non-standalone NR implementations for ensuring interoperability in an environment with UEs from multiple vendors. For standalone NR, the March 2019 version was still experiencing several critical changes (even if the ASN.1 remained backward compatible), and thus the March 2019 version is the first version that is suitable baseline for commercial standalone 5G implementations. The standalone ASN.1 has remained backwards compatible since March 2019. The late drop started formally backward compatibility from June 2019 onward, with the commercial baseline yet to be established (when no longer critical corrections are needed) after June 2019. The late drop covers especially 5G-5G dual connectivity as well as additional dual connectivity architecture options between LTE and 5G, as described in Chapter 5. References 1 Recommendation ITU-R M.2083-0 (2015). IMT Vision - Framework and overall objectives of the future development of IMT for 2020 and beyond. September 2015. 2 ITU-R Working Party 5D web-page (2019). IMT-2020 submission and evaluation process. https://www.itu.int/en/ITU-R/study-groups/rsg5/rwp5d/imt-2020/Pages/ submission-eval.aspx. 3 Report ITU-R M.2410-0 (2017). Minimum requirements related t