Critical Communications

What is the difference between 5G SA and NSA?

07 April 2022
A 5G cell tower from Nokia. Non-standalone 5G cell towers are the initial step for the 5G market but it will be 5G standalone technology that allows 5G to reach its full potential with high speeds, low latency and high bandwidth. Source: Nokia

Standalone (SA) and non-standalone (NSA) have always been controversial. In essence, it can be summed up as the issue of interests. For example, from the perspective of operators, those with a small customer base and low profitability tend to adopt NSA, because independent networking means more base station cost and core network cost investment.

However, the dispute will be settled eventually, and the game will end in equilibrium. It is an indisputable fact that 5G NSA networking is an intermediate step in the transition to 5G SA networking. No matter which operators and where they are from, they all take 5G NSA networking as a first step to open the 5G market. The 3rd Generation Partnership Project (3GPP) defines 12 networking modes that include NSA and SA.

Now that we are talking about the differences between 5G networking SA and NSA, let's take a brief look at these 12 5G networking modes.

Options of a 5G non-standalone network. Source: Matt LeeOptions of a 5G non-standalone network. Source: Matt Lee

The 12 networking modes of 5G

First, we will classify several networking methods according to NSA networking and SA networking. Then we will introduce the networking characteristics of these networking methods and the classification basis of NSA and SA networking.

As shown in the figure above, 5G networking mode has been divided according to NSA and SA. Before introducing the characteristics of various networking modes and the classification basis of NSA and SA, let’s first introduce some basic concepts.

In a 5G communication system, non-independence refers to our 5G base stations and 5G core mobile network (5GC), and to our 4G base stations and 4G core network, evolved packet core (EPC). As for the understanding of the base station and the core network, think of the base station as in the wireless access part of a 5G communication system, and as the network node closest to our user terminal. The core network plays the role of gathering, forwarding, controlling and adjusting the information of multiple base stations.

So according to the above, if there is a 4G with 5G core network and a 4G with 5G base station hybrid network, it is not independent, so how is it possible that the option 4 and option 4a are independent networks?

Options of a 5G standalone network. Source: Matt LeeOptions of a 5G standalone network. Source: Matt Lee

How to determine if a 5G network is standalone

The reason is that the key to determine whether a network is non-independent or independent depends on whether the interface between the 5G base station and 5G fifth generation core transmits the data of the signaling plane (control plane). Interface can be understood as the way of information transmission between each network node. For example, X2 interface between 4G base station and 5G base station, S1 interface between 4G base station and 4G core network, XN interface between 5G base station and 5G base station, NG interface between 5G base station and 5G core network, etc. And user plane data is some useful information that we want to transmit, such as voice information, text information, picture information, video information and so on. Control plane data is mainly some signaling, which is different from user information, as user information is transmitted directly through the communication network from the sender to the receiver and signaling usually needs to be transmitted between different links of the communication network (base station, core network, etc.), each link is analyzed and processed, and forms a series of operations and controls through interaction. Its role is to ensure the user information is transmitted in an efficient and reliable way.

Here is a summary. NR independent networking needs to meet the following two conditions:

  • It is necessary to deploy with the 5G core network.
  • The 5G base station and the core network must be interconnected through the signaling plane.

Another point to note is the eLTE in the diagrams above. What is the meaning of eLTE? LTE refers to the enhanced LTE base station, because it is two different generations of mobile communication systems talking to each other after all, so there are some incompatibilities in protocol. Moreover, because the 4G core network EPC is not compatible with NR protocol, the 5G base station cannot be connected with the 4G core network on the signaling plane, while 5GC core network is designed to be compatible with 4G access, so 5GC is not only able to connect with 5G base station on the signaling plane, but also connecting with 4G base station on the signaling plane. In this case, however, 4G base stations need to be upgraded and expanded. It is generally upgraded on the software level of the base station; hardware-wise, there is not much need for change on the base station.

In addition, we will find that although both Option 5 and Option 3 series are transformation networking models. Option 3 series start from the transformation of base stations, and the core network does not change at all. And Option 5 really starts with the transformation from the core network, while the base station changed nothing at first.

[Discover more about 5G technology and suppliers at GlobalSpec]

The reason for having such differences can be analyzed from the business perspective. The current 3GPP R15 protocol mainly focuses on the enhanced Mobile Broadband (eMBB) service out of the three major application scenarios, focusing on high-speed rate. The wireless connection has the greatest impact from this speed, while the core network does not have much impact from it and is why operators start with the base station transformation. When it needs to focus on the massive Machine Type Communications (mMTC) service later, it needs to leverage network functions virtualization (NFV) and software defined Networking (SDN) technologies in the core network (bearer network) to provide network slices. For mass connection service, as the speed requirement will not be high, the core network is upgraded first.


It should be said that although there are so many network architectures, the choice of specific network architecture and evolution measures still need to be analyzed and selected in combination with the business scenarios and strategic deployment of each operator. All in all, the network architectures are still in compliance with the major direction transforming from NSA to SA.

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