How did the network design simplify from 3G UMTS to LTE?

LTE collapsed the 3G hierarchy: the RNC disappeared, the eNodeB absorbed its functions, and the core was reorganized into a clean control plane (MME) and user plane (Serving/PDN Gateway).

* 3G vs 4G: the RNC folds into the eNodeB; core splits control/user planes. *

Side-by-side comparison:

What was gained:

• Fewer hops — user data passes through fewer boxes → lower latency
• Clean separation — control plane (signaling) and user plane (data) have dedicated elements that scale independently
• Simpler operations — fewer element types to deploy and maintain

The big picture: each generation pushed intelligence outward to the base station and simplified the core: GSM had BTS→BSC→MSC, UMTS had NodeB→RNC→SGSN/GGSN, LTE has just eNodeB→EPC. 5G continues this trend with a cloud-native core.

Go deeper:

• System Architecture Evolution (Wikipedia) — the flat all-IP redesign that removed the RNC and split control plane (MME) from user plane (S-GW/P-GW).