on't use a regular eNB - rather, we need to use an ng-eNB, which supports the 5GC protocols. With this option, the ng-eNB is the master node and it provides access to the control plane and user plane. The secondary node is the gNB, which is connected to 5GC for the user plane only. The last NSA option is Option 4 (with 4a) and it is an evolution of Option 7. With this option, we also have 5GC as we have in Option 7. The main difference between Option 7 and Option 4 is that in Option 4, the gNB is the master node and the ng-eNB is the secondary node. Remember that the master node provides access to the control and user plane while the secondary node only pertains to the control plane: Non-standalone LTE and NR Non-standalone NR and LTE Non-standalone LTE and NR under EPC (option 3) under SGC (option 4) under SGC (option 5) Figure 9.7 - NSA options 5G Deployment Options The most important plane is the control plane because control plane signaling is a prerequisite for mobiles to attach to the network. If the mobile does not achieve control plane signaling, then there will be no user plane. Therefore, whether an MNO should opt for Option 7 or Option 4 depends on the existing 5G coverage. Remember that the master node in Option 4 is the gNB, which means gNBs are responsible for providing access to the control and user plane whereas, in Option 7, the ng-eNB is the master node responsible for the control and user plane. Therefore, there should be wide 5G coverage for an MNO to opt for Option 4. If this is not the case and the MNO has a mature 4G network, Option 7 would be a better choice. A technical comparison of NSA versus SA The following table is a technical comparison between some of the 5G NSA and SA options (https : // gsma.com/futurenetworks/wp-content/uploads/2018/04/Road-to-5G- Introduction-and-Migration_FINAL.pdf): SA (Option 2) Option 3 Option 7 Release 15 ('17.12) - 1st 3GPP 5G specification Release 15 ('18.6) Release 15 ('18.6) prioritised Sub-6 GHz and mmWave bands Sub-6 GHz and mmWave bands are 5G spect