Skip to main content

Network Evolution

How network elements evolved across generations — which functions were split, merged or absorbed. Grey boxes are the older generation, blue ones the successors; click any node for its glossary definition.

Editorial overview — a didactic summary of how functions succeeded each other; for the actual wiring of each generation see the curated 4G EPC and 5G Core maps.

4G→5G

split
MMEMMEAMFAMFSMFSMF
MME's mobility management moved to AMF, session management to SMF (control-plane split in the 5G Service-Based Architecture).
split
S-GWS-GWPGWPGWSMFSMFUPFUPF
S-GW/P-GW control planes merged into SMF, user planes into UPF (CUPS separation completed in 5G).
split
HSSHSSUDMUDMUDRUDRAUSFAUSF
HSS functionality split: subscription management to UDM, data storage to UDR, authentication to AUSF.
evolved
PCRFPCRFPCFPCF
PCRF evolved into PCF, exposing policy rules over the service-based interface instead of Diameter Gx.
evolved
EPCEPC5GC5GC
The monolithic point-to-point EPC evolved into the cloud-native, service-based 5G Core.
evolved
EIREIR5G-EIR5G-EIR
The EIR has checked equipment identities (IMEI) since GSM; in the 5G Core this function is provided by the 5G-EIR, queried by the AMF during registration (PEI check).

3G→4G

evolved
UTRANUTRANE-UTRANE-UTRAN
UTRAN (NodeB + RNC) evolved into the flat E-UTRAN architecture with a single node type, the eNodeB.
absorbed
RNCRNCeNBeNB
RNC functions (radio resource management, handover control) were absorbed into the eNodeB — E-UTRAN has no central controller.
split
SGSNSGSNMMEMMES-GWS-GW
SGSN's control plane (mobility, session) went to MME, its user-plane forwarding to S-GW.
split
MSCMSCMMEMMEIMSIMS
EPS has no circuit-switched domain: the MSC's call control moved to the IMS (VoLTE), while mobility management and paging went to the MME.
absorbed
VLRVLRMMEMME
The VLR's visitor registry — the serving-area context of attached subscribers — was absorbed into the MME in EPS.

2G/3G→4G

evolved
HLRHLRHSSHSS
HLR evolved into HSS, adding IMS subscriber profiles and Diameter-based interfaces to the classic MAP registry.
absorbed
AUCAUCHSSHSS
The Authentication Centre generated authentication vectors for its HLR; in EPS this function was absorbed into the HSS (and later moved on to UDM/AUSF in 5G).

2G→3G

evolved
BSCBSCRNCRNC
The GSM Base Station Controller's role — radio resource management for the access network — passed to the RNC in UMTS, which added soft handover and Iu connectivity to the core.
← Full network overview4G EPC Topology5G Core Topology