rum Sub-6 GHz band is desirable are feasible feasible Required (with or without an CN interworking Not required Not required N26 interface between the 5GC and the EPC) Network slicing and 5G QoS Not supported Supported Supported UE impact (for 5G/LTE dual-mode) EPC-NAS 5GC/EPC-NAS 5GC/EPC-NAS Leverage of LTE Partial (reattach) LTE upgrade Required (eNBs and the EPC) Required (ng-eNBs and the 5GC) None or minor RAN interworking EN-DC NGEN-DC NR-DC (intra-RAT) MR-DC and intra-system Inter-system handover (N26 Inter-RAT data session continuity MR-DC and intra-system handover handover interface) Forward compatibility with SA or Release-16 onwards Figure 9.8 - Technical comparison between 5G NSA and SA options As can be seen from the table, Option 3 and Option 7 are the choices for the transition to Option 2. With Options 3 and 7, core network interworking is not required. However, forward compatibility with SA architectures and with Release 16 onward is low or medium for Options 3 and 7, which also makes these options temporary network architectures to pave the way to Option 2. An economic comparison of NSA versus SA The following table is an economic comparison between the 5G NSA and SA options (https : // ww.gsma.com/futurenetworks/wp-content/uploads/2018/04/Road-to-5- Introduction-and-Migration_FINAL.pdf) 4G to 5G migration strategies SA (Option 2) Option 3 Option 7 System availability '19.2Q 19.4Q '19.4Q Required time for deployment Short Medium Deployment cost (NR) Medium Cost for LTE system upgrade Acquisition cost for 5G Medium (mmWave bands Medium (mmWave bands High (sub-6 GHz band is required spectrum can be used for SN cells) can be used for SN cells) for coverage cell) Migration cost to SA Medium Support of new 5G services Not supported Supported Supported Overall service quality (initial Medium deployment) High (sub-6 GHz + mmWave), NR coverage quality Medium (sub-6 GHz or mmWave) Voice service for 5G UE CSFB and VoLTE CSFB and VoLTE VoLTE and VoNR Figure 9.9 - Economic comparison between 5G NSA and SA op