ed above focus on the network aspects, the understanding of MR-DC operations would not be complete without the radio interface details, which can be found in 3GPP TS 36.331 TS 38.331. References 3GPP Technical Specification 36.300 (2019). Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 36.331 (2019). Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification. Available at: www.3gpp .org (accessed May 29, 2020). 3GPP Technical Specification 36.413 (2019). Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP). Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 36.423 (2019). Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 Application Protocol (X2AP). Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 36.424 (2019). Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 data transport. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 36.425 (2019). Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 interface user plane protocol. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 37.340 (2019). Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Stage 2. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.300 (2019). NR; Overall description; Stage-2. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.331 (2019). NR; Radio Resource Control (RRC); Protocol specification. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.423 (2019). NG-RAN; Xn Application Protocol (XnAP). Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.424 (2019). NG-RAN;