5G Network Migration | Network Structure Overview

5G Network Structure Overview

Now we have understanding about what is 5G and what are  key 5G technologies in radio network, if you have read my previous articles.

To read about 5G Standard Evolution and Key Performance Targets click here.

To read about 5G NR Key Technologies | 5G Technologies for Radio Interface click here.

Now the question we might have as well as Mobile Network Operators  (MNOs) might have is that how to migrate the networks to support 5G?

Operators world wide are planning to deploy their 5G networks to improve the efficient use of resources and enable new services under the use cases (eMBB, URLLC, mMTC) defined by the standards.

5G core network is an instrumental part in enabling advanced services and use cases in 5G era. Even though core network plays critical role in 5G deployments as mentioned, many operators are expected to use the advantages of 5G Radio Access Network (RAN) to enable some services by deploying non-standalone 5G which utilize existing 4G core network with just upgrading software and some hardware. Therefore, most of the operators will position 5G RAN before deploying 5G core network.
There are numerous 5G deploying options are discussed during recent times. And some of them are suitable for early 5G deployments and later move to standalone 5G after deploying 5G core network.

What are 5G Main Networking Options?

Networking options can be categorized into two parts as follows.

• Standalone options (SA): Standalone options consist of one generation of Radio Access Technology (eg: 3G, 4G, 5G).
• Non-standalone options (NSA): Non-standalone options generally consist of two generations of Radio Access Technologies.
  

There are many options defined in 3GPP for 5G deployments.

Following picture from “Operator Requirements for 5G Core Connectivity Options” of GSMA published article summarizes the different options defined by the 3GPP.

Option 2 is the standalone option for 5G deployment while option 3, 4, 7 are non-standalone options. Option 3 is the most popular option, most operators consider for early deployments as it’s based on enhanced Evolved Packet Core (eEPC) which is upgraded version existing 4G core network. Let’s discuss details about these options.

Option 2

Option 2 is the target architecture which is based on 5G core network and standalone 5G NR (New Radio) and can be initially deployed in local areas for specific use cases. In this option, 5G nodes are responsible for handling both control plane and user plane traffic.

Option 3, 3a and 3x

Option 3, 3a and 3x are non-standalone deployment options of 5G. Let’s summarize the functionality, similarities and differences between option 3 sub categories

Common for Option 3 and sub categories
Utilize existing 4G core network (EPC) for both technologies.

• Control plane traffic of both technologies flows through eNodeB (4G base station). eNodeB works as the signaling anchor.

Different for Option 3 and sub categories

Option 3
4G and 5G User plane traffic split point is at eNodeB.

• 4G control plane and user plane: directly connected to EPC
• 5G control plane and user plane: connected to EPC via eNodeB

Option 3a

4G and 5G User plane traffic split point is at EPC. 

• 4G control plane and user plane: directly connected to EPC
• 5G control plane: connected to EPC via eNodeB
• 5G user plane: directly connected to EPC

Option 3x

4G and 5G User plane traffic split point is at gNB (5G base station). 

• 4G control plane: directly connected to EPC
• 4G user plane: connected to EPC via gNB
• 5G control plane: connected to EPC via eNodeB
• 5G user plane: directly connected to EPC

Option 4, 4a

Option 4 and 4a are all non-standalone deployment options of 5G. Let’s summarize the functionality, similarities and differences between option 4 sub categories

Common for Option 4 and sub categories

• Use new 5G core network (5GC) for both technologies.
• Control plane traffic of both technologies flows through gNB (5G base station). gNB works as the signaling anchor.

Different for Option 4 and sub categories

Option 4

 4G and 5G User plane traffic split point is at gNB.

• 4G control plane and user plane: connected to 5GC via gNB
• 5G control plane and user plane: directly connected to 5GC

Option 4a

4G and 5G User plane traffic split point is at 5GC.

• 4G control plane: connected to 5GC via gNodeB
• 4G user plane: directly connected to 5GC
• 5G control plane and user plane: directly connected to 5GC

Option 7, 7a and 7x

Option 7, 7a and 7x are also non-standalone deployment options of 5G. These options are much similar to the option 3, 3a and 3x except the fact that 5GC is used instead of EPC. Therefore operators can move their 5G network from option 3s to option 7s once the 5GC is deployed.

Let’s summarize the functionality, similarities and differences between option 7 sub categories

Common for Option 7 and sub categories

• Utilize new 5GC for both technologies.
• Control plane traffic of both technologies flows through eNodeB (4G base station). eNodeB works as the signaling anchor.

Different for Option 7 and sub categories

Option 7

4G and 5G User plane traffic split point is at eNodeB.

• 4G control plane and user plane: directly connected to 5GC
• 5G control plane and user plane: connected to 5GC via eNodeB

Option 7a

4G and 5G User plane traffic split point is at 5GC.

• 4G control plane and user plane: directly connected to 5GC
• 5G control plane: connected to 5GC via eNodeB
• 5G user plane: directly connected to 5GC

Option 7x

4G and 5G User plane traffic split point is at gNB (5G base station). 

• 4G control plane: directly connected to 5GC
• 4G user plane: connected to 5GC via gNB
• 5G control plane: connected to 5GC via eNodeB
• 5G user plane: directly connected to 5GC

I believe now you have basic knowledge of what is happening in each of networking options for 5G. As we can see there is a tight interworking with 4G for most of the early deployments. Operators will be most probably starting with option 3x and then moving to option 7x in their deployments. Following table summarizes the similarities and differences between deployment options.



Thanks for Reading!!!