So far we have discussed 3GPP standards for 5G NR (New Radio) https://www.vamsitalkstech.com/5g/5g-new-radio-nr-platform-architecture/ and 5GC (Core) https://www.vamsitalkstech.com/5g/5g-core-5gc-platform-architecture/ architecture. While all of the 3GPP releases till Release 15 assume that an entirely new radio and core network will be built standalone, that is not the only reality given the preponderance of 4G networks. Thus, interoperability with existing 4G LTE networks is a key component of the 5G standard from Release 16. This adoption mode is called the 5G NSA (Non Stand Alone). This post provides a quick introduction to the 5G NR deployment option.
The 5G Non Standalone (NSA) Option
The 5G NSA provides a pathway for NR workloads to connect to a 4G core. So this implies an intermediary step to full 5G SA. The SA architecture is comprised of both a new 5G NR connected to a 5G core network without any need for 4G network elements.
Now let us discuss the 5G NR architecture. In this model as shown in the below illustration, the 5G NR works with the 4G eNB for all its control plane signaling needs. It is NSA (Non Standalone) in that it cannot connect to the LTE core network without the presence of a master LTE. 5G NSA uses a feature called dual connectivity to support higher throughputs demanded by 5G usecases as highlighted here – https://www.vamsitalkstech.com/cloud/the-three-key-use-case-areas-for-5g/
The key part of the 5G NR architecture is CUPS (Control and User Plane Separation). In CUPS, the user plane/data path is kept separate from the control path. So the SGW/PGW of the 4G world which unify both control and user plane are now separated with an interface termed “Sx”.
The NSA allows for the following benefits –
- Serves as an intermediate step in the move to a greenfield 5G architecture by allowing reuse of existing 4G equipment
- Reduces cost by orders of magnitude. Lowers both CAPEX and OPEX for operators
- NSA is extremely low in cost compared to SA.
- Faster deployments as 4G locations need to be complemented with 5G Radio, without the need for backhaul/5G base stations etc.
- From a software standpoint, it enables the gradual adoption of both SDN and Cloud Native functions into an EPC network
Conclusion
The 5G NSA provides two key usecases. First, Service Providers have the ability to leverage exting LTE infrastructure for both radio access as well as the core/EPC. Secondly, mobility, control management aspects (i.e., radio access as well as the core network, the evolved packet core [EPC]) to anchor for all mobility management and control plane-related aspects for a session. Using the NSA, the goal for operators is to begin offering 5G services to their customers at low cost.