Description
The Evolved Packet Core (EPC) is the foundational core network architecture for the 3GPP 4G LTE system, introduced as a clean-slate design to support high-speed, low-latency packet data services. It represents a significant departure from the circuit-switched cores of 2G/3G, adopting an all-IP, simplified, and flat architecture. The EPC's primary function is to manage data sessions, provide connectivity between User Equipment (UE) and external packet data networks (like the internet or IMS), and handle critical control-plane and user-plane operations for mobility and security.
Architecturally, the EPC comprises several key logical nodes interconnected via standardized interfaces. The central control-plane entity is the Mobility Management Entity (MME), responsible for signaling, bearer management, authentication, and mobility tracking. The Serving Gateway (S-GW) acts as the local mobility anchor, routing and forwarding user data packets and managing handovers between eNodeBs. The Packet Data Network Gateway (P-GW) is the point of exit and entry for traffic to external networks; it performs policy enforcement, charging, and IP address allocation. For subscriber data and authentication, the Home Subscriber Server (HSS) serves as the central database. The user-plane path is streamlined: data flows from the eNodeB through the S-GW to the P-GW, minimizing latency. The control plane uses the S1-MME interface to connect the eNodeB to the MME and the S11 interface between the MME and S-GW for session management.
How the EPC works involves a coordinated sequence of procedures. When a UE attaches to the network, it initiates a procedure with the MME, which authenticates the user via the HSS. Upon successful authentication, the MME establishes a default bearer by communicating with the S-GW and P-GW, which assigns an IP address to the UE. This bearer represents a virtual pipe with specific Quality of Service (QoS) characteristics. All subsequent user data travels through this bearer path. For mobility, as a UE moves, the MME orchestrates handovers, updating the S-GW's context to seamlessly reroute the data path. The EPC also supports dedicated bearers for services requiring specific QoS, like VoIP. Its role is absolutely central: it is the intelligent hub that enables seamless mobility, ensures security, enforces operator policies, and provides the gateway to the broader internet and service platforms, making LTE's high-performance data experience possible.
Purpose & Motivation
The Evolved Packet Core was created to address the limitations of previous 3GPP core networks, which were built around a dual-domain architecture with separate circuit-switched cores for voice and packet-switched cores for data. This separation was inefficient for the burgeoning demand for mobile broadband data and converged services. The primary motivation for EPC was to support the LTE radio access network's high data rates and low latency with a simplified, cost-effective, and scalable core that used Internet Protocol (IP) for all services, including voice (via VoLTE).
Historically, the work began in 3GPP Release 8, building upon earlier packet core concepts from GPRS and UMTS. The EPC solved key problems: it eliminated the network complexity and cost of maintaining parallel circuit and packet cores, reduced latency through a flatter architecture with fewer nodal hops, and provided a future-proof foundation for all-IP services. It was designed from the outset to handle massive growth in data traffic, sophisticated QoS for different applications, and seamless mobility not just within LTE but also to and from legacy 3GPP and non-3GPP networks (like WiFi). The creation of EPC was a strategic move to enable mobile operators to compete with fixed broadband providers and support the new era of smartphones and connected devices.
Evolution Lineage
- Succeeded by: 5GC (4G→5G)
- Network evolution overview →
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (87 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the EPC was enhanced to support interworking and migration towards 5G, specifically introducing support for EPC_DC_NR (EPC-NR Dual Connectivity) and its required subscription control and UE capability handling. Key additions enabled interworking between EPC/ePDG and 5G Core Network (5GCN), including procedures for handover and PGW selection for 5GC UEs. Furthermore, the release expanded EPC management capabilities for these new functions, including updates to NRM definitions and the introduction of EPC CUPS (Control and User Plane Separation) for various solution sets.
- Network selection for EPC-level roaming to support migration TS 23.280CR0099
- TS 23.401 Subscription Control for EPC_DC_NR TS 23.401CR3225
- UE capability handling for EPC_DC_NR TS 23.401CR3257
- Subscription Control for EPC_DC_NR: handover from Gn/Gp SGSN TS 23.401CR3306
- OI#19 - 5GC-EPC interworking: PGW selection for 5GC UE for connectivity via untrusted access TS 23.402CR2980
- 5G N3A - info for handover from EPC/ePDG to 5GS TS 24.302CR0663
+ 32 more changes
In Release 16, key enhancements to the EPC included the introduction of Dedicated Bearers for Ethernet to support new service types and the formal support for Restricted Local Operator Services (RLOS), including a specific "EPS RLOS attach" procedure. The release also focused on improving interworking and mobility with the 5G Core (5GC), introducing mechanisms for EPS bearer synchronization, redirection for CIoT optimizations, and the transfer of PDN connections from non-3GPP access. Furthermore, it provided corrections and clarifications for emergency services fallback and interworking procedures involving the ePDG connected to the EPC.
- Support for Restricted Local Operator Services in EPC TS 23.401CR3491
- Dedicated Bearers for Ethernet in EPC TS 23.401CR3498
- Dedicated Bearers for Ethernet in EPC - IOPS / LIPA / SIPTO@LN aspects TS 23.401CR3508
- CIoT optimisations redirection betwee EPC and 5GC TS 24.301CR3182
- CIoT optimisations redirection betwee EPC and 5GC TS 24.501CR0988
- Dedicated Bearers for Ethernet in EPC TS 23.401CR3501
+ 10 more changes
In Release 17, key enhancements for the Evolved Packet Core (EPC) included introducing support for Multi-Access (MA) PDU Sessions with 3GPP access and enabling User Plane Integrity Protection (UP IP) for EPC-connected architectures using NR PDCP. The release also specified procedures for MUti-SIM (MUSIM) capability negotiation and improved interworking, such as handling LTE-M indications during mobility from 5GC to EPC. Furthermore, it defined mechanisms for service requests to redirect CIoT UEs to the EPC and refined interactions over the S1 interface between the E-UTRAN and the EPC.
- Support for MA PDU Session with 3GPP access in EPC TS 24.301CR3591
- MUSIM capability negotiation in EPC TS 24.301CR3559
- Support for MA PDU Session with 3GPP access in EPC TS 24.501CR3208
- Introducing support of UP IP for EPC connected architectures using NR PDCP TS 36.300CR1353
- Introducing support of UP IP for EPC connected architectures using NR PDCP TS 36.331CR4763
- Introducing support of UP IP for EPC connected architectures using NR PDCP TS 38.331CR2904
+ 9 more changes
In Release 18, the enhancements for the EPC focused on extending and refining Mission Critical Services (MCS) and Mission Critical Push-to-talk (MCPTT) over WLAN access, specifically for procedures like attach (both trusted and untrusted) and transport priority handling. The work also introduced congestion exemption mechanisms for WLAN access to the EPC and updated associated indicators. These updates ensured that critical services could operate reliably when UEs connect to the EPC via non-3GPP WLAN networks.
- MPS when access to EPC is WLAN TS 23.401CR3713
- MPS when access to EPC is WLAN TS 23.402CR2998
- MPS for WLAN EPC congestion exemptions for MCM TS 24.244CR0058
- MPS for WLAN EPC congestion exemptions TS 24.302CR0754
- MPS for WLAN EPC Transport Priority TS 24.302CR0752
- MPS for WLAN EPC attach TS 24.302CR0753
+ 7 more changes
In Release 19, the primary enhancement for the Evolved Packet Core (EPC) was the introduction of a new "Store and Forward" feature to support satellite operations. This addition required new attributes to be defined within the management specifications to enable this capability. The release also included work on security aspects of the full EPC architecture and defined UE behavior for handling specific unavailability configuration information.
- Introduction of Store and Forward feature in EPC TS 23.401CR3801
- Rel-19 CR TS 28.708 Add attributes to support Store and Forward Satellite operation for EPC TS 28.708CR0011
- Rel-19 CR TS 28.708 Add attributes to support Store and Forward Satellite operation for EPC TS 28.709CR0016
- Security related aspect of Full EPC architecture TS 23.401CR3937
- UE behaviour when the UE receives the Unavailability configuration IE without a value in EPC TS 24.301CR4324
Explore further
Broader topics and technologies where EPC plays a role.
Defining Specifications
3GPP specifications that define or reference EPC, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 22.801 vc00 | Study on Non-MTC Mobile Data Application Impacts | Rel-12 |
| TS 23.041 vj30 | Cell Broadcast Service and Public Warning System | Rel-19 |
| TS 23.139 vj00 | 3GPP-Fixed Broadband Interworking Stage 2 | Rel-19 |
| TS 23.179 vd50 | MCPTT Functional Architecture | Rel-13 |
| TS 23.180 vj10 | MC services support in IOPS mode | Rel-19 |
| TS 23.261 vj00 | IP Flow Mobility between 3GPP and WLAN | Rel-19 |
| TS 23.280 vk10 | Common Architecture for Mission Critical Services | Rel-20 |
| TS 23.281 vk10 | MCVideo Functional Architecture and Flows | Rel-20 |
| TS 23.369 vj20 | 5G System Architecture for Ambient IoT | Rel-19 |
| TS 23.379 vk00 | MCPTT Functional Architecture | Rel-20 |
| TS 23.401 vj50 | Evolved Packet System (EPS) Stage 2 Description | Rel-19 |
| TS 23.402 vj00 | EPC for Non-3GPP Access (PMIP) | Rel-19 |
| TS 23.434 vk00 | Service Enabler Architecture for Verticals | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 23.701 vc00 | WebRTC Access to IMS Architecture Study | Rel-12 |
| TR 23.758 vh00 | Study on Edge Application Architecture | Rel-17 |
| TS 23.839 vc00 | Fixed-Mobile Convergence Architecture Study | Rel-12 |
| TS 23.857 vb00 | EPC Node Failure & Restoration Study | Rel-11 |
| TS 23.882 v800 | 3GPP System Evolution Feasibility Study | Rel-8 |
| TS 23.894 va00 | IMS Local Breakout & Optimal Media Routing Study | Rel-10 |
| TS 23.896 vc00 | Policy & Charging Control for Fixed Broadband Convergence | Rel-12 |
| TS 24.139 vj00 | UE-EPC Procedures for Fixed Broadband Access | Rel-19 |
| TS 24.244 vj00 | Wireless LAN Control Plane Protocol | Rel-19 |
| TS 24.301 vj60 | NAS protocol for Evolved Packet System | Rel-19 |
| TS 24.302 vj00 | Access to EPC via non-3GPP networks; Stage 3 | Rel-19 |
| TS 24.303 vj00 | Dual-Stack MIPv6 Mobility Management | Rel-19 |
| TS 24.304 vj00 | MIPv4 FA Mode Mobility Management in EPC | Rel-19 |
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 24.801 v810 | CT1 SAE NAS Aspects for EPC | Rel-8 |
| TS 24.890 vg00 | 5G NAS Protocol for 5GS Stage 3 | Rel-16 |
| TR 24.980 vg00 | MCPTT IMS Profile for Gm Reference Point | Rel-16 |
| TS 25.322 vj00 | RLC Protocol Specification | Rel-19 |
| TR 25.912 vj00 | Evolved UTRA and UTRAN Technical Report | Rel-19 |
| TS 26.501 vj30 | 5G Media Streaming (5GMS) Architecture | Rel-19 |
| TS 26.802 vj20 | Multicast Enhancements for 5G Media Streaming | Rel-19 |
| TR 26.924 vj00 | MTSI QoS Improvement Study | Rel-19 |
| TR 26.941 vj01 | 5G Media Slicing Extensions | Rel-19 |
| TS 28.627 vj00 | SON Policy NRM IRP: Requirements | Rel-19 |
| TS 28.707 vj00 | EPC NRM IRP Requirements | Rel-19 |
| TS 28.708 vj00 | EPC NRM Integration Reference Point Information Service | Rel-19 |
| TS 28.709 vj00 | EPC NRM IRP Solution Set Definitions | Rel-19 |
| TS 28.802 vf00 | Management Study for 5G Network Architecture | Rel-15 |
| TS 29.061 vj00 | Packet Domain Interworking for PLMN | Rel-19 |
| TS 29.168 vj00 | SBc-AP Protocol Specification | Rel-19 |
| TS 29.172 vj00 | EPC LCS Protocol (ELP) specification | Rel-19 |
| TS 29.273 vj10 | AAA Protocols for Non-3GPP Access in EPS & 5GS NSWO | Rel-19 |
| TS 29.274 vj50 | GTPv2-C Control Plane Protocol Specification | Rel-19 |
| TS 29.275 vj00 | PMIPv6 Mobility & Tunnelling Protocols Stage 3 | Rel-19 |
| TS 29.279 vj00 | MIPv4 Mobility Protocol over S2a | Rel-19 |
| TS 29.507 vj40 | 5G Access & Mobility Policy Control Service | Rel-19 |
| TS 29.513 vj40 | 5G PCC Signalling Flows & QoS Mapping | Rel-19 |
| TS 29.826 vd10 | P-CSCF Restoration Enhancements for WLAN | Rel-13 |
| TS 29.866 vj00 | IMS Disaster Prevention & Restoration Enhancement | Rel-19 |
| TS 29.890 vg00 | CT3 5G System Technical Report | Rel-16 |
| TS 31.102 vj40 | USIM Application Specification | Rel-19 |
| TS 31.121 vi50 | UICC-terminal interface test specification | Rel-18 |
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.251 vj00 | PS Domain Charging Management | Rel-19 |
| TS 32.252 vc00 | 3GPP WLAN Interworking Charging | Rel-12 |
| TS 32.295 vj00 | 3GPP Charging: CDR Transfer via GTP' Protocol | Rel-19 |
| TS 32.401 vj00 | Performance Management Concept & Requirements | Rel-19 |
| TS 32.404 vj00 | Performance Management Definitions & Template | Rel-19 |
| TS 32.426 vj00 | EPC Performance Measurements Specification | Rel-19 |
| TS 32.455 vj00 | EPC Key Performance Indicators (KPIs) | Rel-19 |
| TS 32.521 vb10 | SON Policy NRM IRP Requirements | Rel-11 |
| TS 32.541 vj00 | SON Self-Healing Concepts and Requirements | Rel-19 |
| TS 32.593 vj00 | HeNB OAM&P Procedure Flows for Type 1 Interface | Rel-19 |
| TS 32.751 vb00 | EPC NRM IRP Requirements | Rel-11 |
| TS 32.752 vb01 | EPC NRM IRP Information Service | Rel-11 |
| TS 32.816 v800 | UMTS Management Reuse for E-UTRAN/EPC | Rel-8 |
| TS 32.820 v1801 | Charging Architecture Study for Evolved 3GPP | Rel-8 |
| TS 32.823 v1900 | Self-Organizing Networks Self-Healing Study | Rel-9 |
| TS 32.826 va00 | Study on Energy Savings Management in LTE/SAE Networks | Rel-10 |
| TS 33.107 vj00 | Lawful Interception Architecture & Functions | Rel-19 |
| TS 33.401 vj10 | EPS Security Architecture | Rel-19 |
| TS 33.402 vj00 | Security for non-3GPP access to EPS | Rel-19 |
| TS 36.113 vj00 | EMC Requirements for E-UTRA Base Stations | Rel-19 |
| TS 36.124 vj00 | EMC for E-UTRA User Equipment | Rel-19 |
| TS 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.302 vj00 | E-UTRA Physical Layer Services | Rel-19 |
| TS 36.304 vj00 | UE Idle Mode Procedures in E-UTRA | Rel-19 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 36.401 vj00 | E-UTRAN Overall Architecture Description | Rel-19 |
| TS 36.410 vj00 | S1 Interface: General Aspects and Principles | Rel-19 |
| TS 36.413 vj10 | S1 Application Protocol (S1AP) | Rel-19 |
| TS 36.414 vj00 | S1 Interface User Plane Transport | Rel-19 |
| TS 36.423 vj10 | X2 Application Protocol (X2AP) Specification | Rel-19 |
| TS 36.424 vj00 | X2 Interface User Plane Transport Protocols | Rel-19 |
| TS 36.440 vj00 | E-UTRAN MBMS Architecture Description | Rel-19 |
| TS 36.444 vj00 | M3AP Protocol Specification for M3 Interface | Rel-19 |
| TS 36.445 vj00 | M1 interface user plane protocol for MBMS | Rel-19 |
| TS 36.455 vj00 | LTE Positioning Protocol Annex (LPPa) | Rel-19 |
| TS 36.456 vj00 | SLm Interface Introduction | Rel-19 |
| TS 36.463 vj00 | XwAP Protocol Specification | Rel-19 |
| TS 36.876 vd00 | Study on Small Cell High Layer Aspects for LTE | Rel-13 |
| TS 36.887 vc00 | Energy Saving Enhancement for E-UTRAN Study | Rel-12 |
| TR 36.927 vj00 | Network Energy Saving for E-UTRAN | Rel-19 |
| TS 37.113 vj00 | EMC Requirements for Multi-Standard Radio Base Stations | Rel-19 |
| TS 37.483 vj10 | E1 Application Protocol (E1AP) | Rel-19 |
| TR 37.985 vj00 | Overview of V2X features in LTE and NR | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.413 vj10 | NG Application Protocol (NGAP) | Rel-19 |
| TS 38.463 vj00 | E1 Application Protocol (E1AP) | Rel-19 |
| TS 38.473 vj10 | 5G F1 Application Protocol (F1AP) | Rel-19 |
| TS 38.523 vj20 | 5G NR UE Conformance Testing: Idle/Inactive | Rel-19 |
| TR 38.848 vi00 | Technical Report on Ambient IoT | Rel-18 |
| TS 43.051 vj00 | GERAN Stage 2 Service Description | Rel-19 |
| TS 43.129 vj00 | PS Handover in GERAN A/Gb and GAN Modes | Rel-19 |
