3GPP 23.501 v20.2.0 — the document's own text
4.2.18.0 General
Taught in 3. The shape of the 5G core (The 5G system architecture, in depth).
In order to support the Energy Efficiency and Energy Saving feature, the 5G System Architecture is extended as shown in Figure 4.2.18.1-1 and Figure 4.2.18.1-2.