  The 3rd generation partnership project (3GPP) has been engaged in further
advancing the evolved universal mobile telecommunications system (UMTS)
terrestrial radio access network (E-UTRAN) and UTRAN based radio access network
technologies. New radio (NR) is the 3rd generation partnership project (3GPP)
endeavor for outlining and standardization of the 5th generation (5G) advanced
radio access technology. 3GPP has released the first set of 5G NR standards,
i.e., the non-standalone 5G radio specifications. As long-term evolution (LTE)
technology is massively deployed and broadly accepted, the transition from LTE
to 5G is very critical, and it is of maximal importance that the backward
compatibility of 5G with LTE is considered. 3GPP has identified several
architecture options for 5G. This article gives an overview of the NR
architecture options, their deployment scenarios, and the key migration paths.
The LTE-NR dual connectivity (DC) is presented. This DC scenario is unique in
the sense that DC is being endowed for two different generations of 3GPP radio
access technologies. We, further, present the integration of multipath
transmission control protocol (MPTCP) with LTE-NR DC and DC-like aggregation,
i.e., 3GPP-non-3GPP interworking to bring in the advantages of MPTCP in terms
of link robustness, reliability and dynamic mapping between the traffic flows
and the available paths. Finally, we discuss the future research and
standardization directions of the next-generation networks.
