5G SA Options - Option 2, Option 5
5G NR Network Mode Options Defined by 3GPP
For 5G network architecture, 8 options were proposed at the 72nd general meeting of 3GPP TSG-RAN, as shown in the figure below.
8 options for 5G network architecture
These 8 options are divided into two groups: SA modes (Standalone) and NSA modes (Non-Standalone). Options 1, 2, 5, and 6 are SA modes, while options 3, 4, 7, and 8 are NSA modes. And options 3, 4, and 7 have different sub-options.
Among these options, Option 1 has already been implemented in the 4G structure, while Option 6 and 8 are only theoretical deployment scenarios without practical deployment value, and will not be considered in the standard.
Let's discuss them one by one, starting with SA modes.
SA Option 1
Option 1
The figure above shows the architecture of Option 1, which is a pure 4G networking architecture.
Notice that there are a solid line and a dashed line between the phone, 4G base station and 4G core network. The dashed line represents the control plane and the solid line represents the user plane.
Control plane: the channel to send the signaling required to manage and schedule resources.
User plane: the channel to send the user data. The user plane and the control plane are completely separate.
Option 1 has nothing to do with 5G.
SA Option 2
Option 2
The figure above shows Option 2. The architecture is very simple, that is, 5G base station is connected to 5G core network, which is the ultimate form of 5G network architecture and can support all services of 5G.
Although the architecture is simple, to build such a 5G network, a large number of new base stations and core network should be built, which is very costly.
SA Option 5
Option 5
The figure above shows Option 5. As you can see, this is actually an upgraded 4G base station connected to the 5G core network, which is essentially 4G. However, after the new 5G core network is built, the original 4G core network should be gradually phased out. So, 4G base station is bound to be needed to connect the 5G core network, and thus it is also an architecture that will appear.
However, compared with 5G base stations, the improved 4G base stations still have obvious differences in terms of peak rate, delay and capacity. As for subsequent optimization and evolution, enhanced 4G base station may not be able to support. So, the prospect for Option 5 architecture is not good either.
SA Option 6
Option 6
The Option 6 is to connect 5G base stations to the 4G core network. This option can hardly make use of the power of 5G base stations. Considering that 5G base stations are already a bigger part of investment compared to 5G core network, it’s not really a reasonable choice to trade large investment with little return. Therefore, no carrier will choose this architecture, and 3GPP does not consider standardization of it.
Advantages and disadvantages of SA modes
To sum up, there are only Option 2 and 5 for SA modes of 5G, of which option 2 is the ultimate architecture of 5G network.
The advantages of SA Option 2 are as follows:
1. Introduction of 5G base station and 5G core network in one step; independent of the existing 4G network; with the shortest evolution path to ultimate 5G network.
2. Brand new 5G base station and 5G core network can support all new functions and services introduced by 5G network.
Meanwhile, the disadvantages of SA Option 2 are as follows:
1. 5G network has relatively higher frequency than LTE, so it is difficult to achieve continuous coverage during the initial deployment, and thus there will be a lot of switching between 5G and 4G networks, which will result in poor user experience.
2. The initial deployment cost is relatively high and the existing 4G base station resources cannot be effectively utilized.
