In this chapter we shall see the deployment options of a 5G network.
On a high level the architecture has been divided into 2 types.
1. NSA – Non Stand Alone Architecture
2. Standalone Architecture.
EPC played an important role in 4g. Similarly, in 5G 5G Core Network (5GC) plays an important role.
Now, 5G development started when 4G was into deployment state. Hence it became necessary for 5G to be operated with 4G EPC also.
So a 5G network connected to only one Radio Access Technology (RAT) is a Stand Alone (SA) architecture.
5G connected with EPC/5GC is a Non Standalone Architecture (NSA).
In the above image, option 1, 2, 5 are Standalone Architecture.
Option 3, 4, 7 are Non Standalone Architecture.
Option 3 has been widely deployed initially as it sits well with EPC. Option 3 has been fully specified in 3GPP Rel 15.
Now we shall see in brief how these deployments work:
Option 1: SA LTE Connected to EPC-legacy
It is the current deployment (year 2020).
This is a SA architecture.
You have LTE + EPC
This deployment is called as EPC connected legacy.
Option 2: SA NR Connected to 5G Core
This is a Standalone Architecture.
In this option, UE will be connected to 5G RAN or gNB and connected to 5G Core.
This will allow all the 5G use-cases like eMBB, mMTC and URLLC.
Option 3: EN-DC (EUTRA-NR Dual Connectivity)
It is a non standalone architecture. Here both eNB and gNB are connected to EPC.
eNB is used for control plane.
Both eNB and gNB are used for data plane.
Option 3 has 3 different types:
• Option-3 — The user plane data is sent to the 5G NR via the LTE RAN
• Option-3a — The user plane data comes to 5G NR directly from the EPC
• Option-3x — It is a combination of 3 and 3a. The userplane data will come from both EPC and eNB to gNB
Option 4: NR-EUTRA Dual Connectivity(NE-DC)
This is also a non standalone deployment.
Here both eNB and gNB are connected to 5GC.
gNB or 5GNR will handle the control plane signal and send it to 5GC.
This option can also operate on 2 different types:
Option 4: The userplane traffic from eNB will route through gNB and goto 5GC.
Option 4a: The userplane traffic split will be made at 5GC and sent directly to eNB and gNB.
Option 5: SA LTE under 5GC
This is a standalone deployment.
In this deployment eNB is connected to 5GC.
Option 7, 7a, 7x:
In this scenario, eNB is connected to 5GC.
gNB is connected to eNB.
Option 7 has 3 different types:
• Option-7 — The user plane data is sent to the 5GC via the eNB
• Option-7a — The user plane data comes to eNB and gNB from 5GC
• Option-7x — It is a combination of 7 and 7a.
Conclusion:
Option 6 has been removed from 3GPP Rel 15.
The eNB when deployed with 5GC it will become ng-eNB as it is connected to 5GC.
Non Standalone Deployment:
Option 3: NSA LTE and NR under EPC
Option 4: NSA NR and LTE under 5GC
Option 7: NSA LTE and NR under 5GC
Standalone Deployment:
Option 1: SA LTE under EPC
Option 2: SA NR under 5GC
Option 5: SA LTE under 5GC
Migration Strategy:
1) Option 2 directly
2) Option 3 >> Option 7 >> Option 5 (LTE under 5GC)
3) Option 3 >> Option 2
4) Option 3 >> Option 4 >> Option 2
