Setting up 5G gNB (NG-RAN) Nodes and Interfaces
The free version of the article would be published soon on my blog site (https://www.shanjaffry.tech/).
In this article, I’ll discuss 5G gNB (NG-RAN) nodes’ setup procedures.
In a 5G RAN, we have protocol-level functionalities distributed between entities known as CU-CP, CU-UP, and DU. They combine to make up a gNB. A CU node (comprising of CU-CP, and CU-UP) ensures NG-RAN’s connectivity with 5G core (5GC). The DU node interacts with the end user (UE) through Radio Unit (RU) as shown in Figure 1 below.
There could only be ONE CU-CP in a gNB and multiple CU-UPs. Each CU-UP can then be connected to multiple DUs (not shown in the figure).
Messages between CU-CP and CU-UP are exchanged over the E1 interface. Between DU and CU-CP, the F1 interface is used (F1-U is for the user plane, and F1-C is for the control plane).
Node Hierarchy
CU-CP is the main controller for C-plane activities. For a U-plane between CU and DU, CU-UP is the controlling entity. Hence, in an imaginary/so-called hierarchical model, DU is at the lowest hierarchy of operations, CU-CP is at the highest hierarchy, and CU-UP falls in the middle (below CU-UP and above DU). (special note: It does not mean that DU has the lowest amount of work. In my opinion, DU has the…
