What is EPS?
EPS (Evolved Packet System) is the complete end-to-end 4G system architecture comprising the radio access network (E-UTRAN) and the core network (EPC). It represents the entire 4G LTE ecosystem — from the eNB base stations through the core network elements (MME, S-GW, P-GW, HSS) — enabling all-IP mobile broadband communication. EPS was the first fully packet-switched mobile architecture, eliminating the circuit-switched domain used in 2G/3G for voice, and introduced VoLTE for voice services over IP.
How Does EPS Work?
EPS connects UEs to data networks through a flat, all-IP architecture. On the RAN side, eNBs handle radio transmission and connect to the EPC via the S1 interface. Within the EPC, the MME (Mobility Management Entity) handles control plane signalling (attach, authentication, handover), the S-GW (Serving Gateway) routes user plane data, and the P-GW (PDN Gateway) provides IP address allocation and connectivity to external data networks. The HSS stores subscriber profiles. All user traffic — including voice (VoLTE) — is carried as IP packets through GTP tunnels. EPS also serves as the anchor for 5G NSA deployments where the EPC supports EN-DC configurations.
Use Cases
4G LTE mobile broadband services, VoLTE voice delivery, 5G NSA anchor network (EN-DC), IoT connectivity via LTE-M and NB-IoT, and enterprise mobile connectivity.
3GPP / Standards Reference
3GPP TS 23.401 (GPRS enhancements for E-UTRAN access), 3GPP TS 23.402 (Architecture enhancements for non-3GPP accesses)
Related Terms
EPC | eNB | LTE | E-UTRAN | 4G
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
