5G CU Meaning: What is it Exactly?

The following guide will explore 5G CU meaning. While 5G produces faster mobile broadband connection speeds, it has some limitations. One of them is that the technology uses millimeter wavelengths.

This means that 5G’s wavelengths are shorter than 3G and 4G. One way carriers have overcome this is through innovative network architecture choices – particularly for base stations.

One such architecture design is the centralized unit (CU) design. 

The following guide discusses the implications of using this design and how 5G networks implement it.

Understanding The Architecture of 5G

We cannot discuss how or what the 5G CU is without discussing the 5G network design.

 A 5G network consists mainly of a gNodeB (gNB) base station. The base station can either be standalone, non-standalone or utilize a CU-DU split.

A standalone gNB can implement a centralized/central unit (CU) or distributed unit (DU). 

Today, the CU-DU is seemingly the most effective and thus common 5G base station architecture. It uses both entities (CU and DU).

Difference Between DU and CU

The distribution unit is primarily responsible for real-time scheduling functions. It determines when and which device should communicate. Additionally, it dictates which radio resources, such as frequency and time slots, are assigned to each device.

On the other end of the spectrum, the Central Unit (CU) deals with non-real-time functions. It works with the top layers of the network protocol stack, whereas the DU works with the bottom layers.

5G Telecommunications Tower

5G Telecommunications Tower

Supported Protocols 

The lower layers (DU-supported) include:

The higher layers (CU-supported) include:

gNB Locations

When separate, the distribution unit is closer to the base station site than it is to the user. While the CU (as the name implies) is positioned in a centralized location.

The DU-CU split allows us to bring the DU closer to the device (phone) user, which can be crucial in use cases like Edge computing. This paradigm brings the data source closer to the connecting device (router, tablet, or phone).

Often, 5G networks contain multiple gNBs. In most cases, each of them shares a single CU. Inversely, all the gNBs are assigned a unique DU. 

5G Vector Image

5G Vector Image

How CU and DU Are Connected

A single CU tends to control all the DUs in this architecture design. They connect through the F1 interface. 

This interface transfers control plane signaling using the F1 application protocol (F1AP). The control plane dictates how networks forward packets.

This shared hardware platform is ideal for use cases such as deploying cloud computing and Network Function Virtualization (NFV).

5G CU Meaning: Conclusion

The above guide explores the 5G CU meaning. The complexity of 5G architecture is one of the reasons it has yet to surpass the coverage of its two predecessors – 4G and 3G. 

You may find that Starlink has more far-reaching coverage than 5G. For now, 5G partially uses 4G network hardware for some of its gNB base stations. 

The rollout has been a bit sluggish because, along with network complexity, 5G’s equipment is expensive. 

Nevertheless, all stakeholders in 5G technology hope to have at least 85% of the world covered by 2028.