8 options for 5G networking

Some people say that the road to 5G evolution is as complicated as a labyrinth.

Different from the past, there are 8 types of 5G networking options, except that option 1 is 4G architecture, options 6 and 8 are abandoned by the industry, and there are also options 2, 3, 4, 5 and 5. Options, where options 3, 4, and 7 also include different sub-options.

Our task today is to make clear of these options.

  simply put  

Simply put, the 5G networking includes the following solutions:

• Option 1, independent networking (SA), that is, the LTE base station is connected to the 4G core network, and the current 4G network networking architecture.

• Option 2, Independent Networking (SA), that is, the 5G NR base station is connected to the 5G core network.

• Option 3, Non-Independent Networking (NSA), ie dual connectivity 4G core network for LTE and 5G NR base stations.

• Option 4, Non-Independent Networking (NSA), which is a 5G NR and LTE base station dual connectivity 5G core network.

• Option 5, Independent Networking (SA), that is, the LTE base station is connected to the 5G core network.

• Option 7, non-independent networking (NSA), ie dual connectivity 5G core network for LTE and 5G NR base stations.

It sounds a bit like a tongue twister, or a picture to illustrate it.



Here you have to mention the double connection (DC).

The dual connectivity technology was first proposed in the 3GPP R12 version, which is the 4G era. The basic principle is to connect a mobile phone to two (or more) nodes (base stations) in the radio access network, one of which is the master node, responsible for The control plane of the wireless access is responsible for processing signaling or control messages; and the other node (or nodes) is the secondary node, which is only responsible for the user plane, that is, responsible for carrying data traffic.

R12 is to introduce dual connectivity technology? Mainly to improve network speed, balance network load, and avoid switching interruptions to ensure robust mobility.

In the 5G era, the principle of LTE/NR dual connectivity is basically the same as the LTE/LTE dual connectivity principle of R12, either the LTE base station (eNB) is the primary node, the 5G base station (gNB) is the secondary node, or the 5G base station (gNB) is the primary. The node, the LTE base station (eNB) is a secondary node.

After a brief introduction, let's take a look at each networking option.
 
The 3GPP Release 15 NSA NR standard completed in December 2017 is based on the Option 3 series.

In the option 3 series, the terminal is connected to 5G NR and 4G LTE at the same time, the control plane is anchored to 4G, and the 4G core network is used.

On the control side, the Option 3 series relies entirely on existing 4G systems. But there is a difference in the anchor point of the user plane, which is why the option 3 series has three sub-options of 3, 3a and 3x.

What is the difference between options 3, 3a and 3x?


The characteristics of option 3 are as follows:

• The control plane and user plane of the 5G base station are both anchored to the 4G base station.

• The 5G base station does not directly communicate with the 4G core network, it connects to the 4G core network through the 4G base station.

• Mobile terminals that transmit 4G and 5G data traffic after being split at the 4G base station.

• The Xx interface between the 4G base station and the 5G base station needs to support both the control plane and 5G data traffic, as well as support flow control and meet the delay requirements.

Obviously, the biggest problem with the Option 3 architecture is the -4G base station is under great pressure

Since the 4G and 5G data traffic is shunted (or aggregated) to the 4G base station, this means that the 4G base station needs to process 4G+5G traffic at the same time. The peak rate of 5G is several times that of 4G, and the original 4G base station is not the 5G high rate. Design, therefore, 4G base stations will inevitably encounter processing capacity bottlenecks.

The solution is to upgrade the hardware of the 4G base station.

But upgrading 4G base stations is costly, and operators must be unwilling. Therefore, 3GPP has introduced two options - options 3a and 3x.


The difference between option 3a and option 3 is that the 4G base station is no longer allowed to be flooded. The 4G and 5G data traffic is no longer split and aggregated through the 4G base station, but the user planes are directly connected to the 4G core network, and only the control plane is anchored to the 4G base station. .

Although option 3a reduces the burden on the 4G base station, it does not cost a lot of money to upgrade the hardware of the 4G base station, but there are new disadvantages.

First, the 4G base station and the 5G base station are directly connected to the 4G core network on the user plane, and there is no X2 interface interconnection between the two, which means that the two will each independently carry 4G and 5G, and no load sharing, such as possible 4G base station. It only carries VoLTE voice traffic, while the 5G base station only carries Internet traffic.

At the same time, when the mobile phone "switches" from the 5G base station to the 4G base station, the core network needs to perform S1 (the interface between the base station and the core network) Path Switch, so there is a little "switching" delay.


Option 3x can be thought of as a combination of option 3 and option a.

In option 3x, the control plane is still anchored to 4G, but in the user plane 5G base station is connected to the 4G core network, the user data traffic is split and aggregated at the 5G base station, either directly to the terminal or through the X2 interface. Forwarded to the 4G base station and then transmitted to the terminal.

The option 3x architecture is future-oriented. It solves the performance bottleneck problem of the 4G base station under the option 3 architecture. It does not need to upgrade the original 4G base station hardware, and solves the problem of 4G and 5G base stations in the option 3a architecture.

For some low-speed data streams, such as VoLTE, it can also be directly transmitted from the 4G core network to the 4G base station.

So far, most operators have opted for option 3x.
 


Option 2 is a separate networking between the 5G base station and the 5G core network, and the 5G core network and the access network are "packaged" into the 5G era at one time.

In a non-independent networking, 5G and 4G communicate with each other at the access network level, and the interconnection is more complicated. In the Option 2 independent networking, the 5G network is independent of the 4G network, and the 5G and 4G are only interconnected at the core network level, and the interconnection is simple.


▲ Under the option 2 architecture, 4G network and 5G network are interconnected at the core network level.

But the problem is that, unlike the option 3 series, which relies on the mature network and ecological scale advantages of 4G, once the operator chooses to build the network from option 2, it means that a large-scale investment in building an independent 5G network is needed. Under the current situation that the use cases have not yet broken out, this requires operators to balance 4G asset protection and 5G network construction investment.
 



Option 7 series includes three sub-options of 7, 7a and 7x. Similar to option 3, it can be regarded as an upgraded version of option 3 series, except that option 3 series is connected to 4G core network, while option 7 series is connected to 5G core network. Both NR and LTE migrated to the new 5G core network.
 

Option 4 series includes two sub-options of 4 and 4a. In the option 4 series, the 4G base station and the 5G base station share the 5G core network, the 5G base station is the master station, and the 4G base station is the slave station.

Option 4 series requires a fully covered 5G network, so operators deploying 5G with less than 1 GHz band prefer this deployment.
 
Option 5 connects the 4G base station to the 5G core network, similar to option 7, but without a dual connection to the NR.

Operators who choose option 5 value the cloud's native capabilities of the 5G core network. For example, the UK operator Three plans to migrate the 4G core network to the 5G core network in advance to help some enterprise private networks access their 5G core network early. Provide flexible network slicing services, and hope to provide cloud gaming services to consumers as soon as possible.