Roadmap of free5GC project:
Stage 1 (released in January 2019): migrated 4G Evolved Packet Core (EPC) into 5GC Service-Based Architecture (SBA)
Note: Stage 1 will be upgraded to support Non-standalone 5G feature
- Migrated the entities of 4G EPC, including Mobile Mobility Entity (MME), Serving Gateway (SGW) and Packet Data Network Gateway (PGW) into 5GC functions of Access and Mobility Management Function (AMF), Session Management Function (SMF) and User Plane Function (UPF).
- Migrated interfaces: S1 to N2, S1-U to N3 and SGi to N6
- Removed interfaces: S5/S8 and S11.
- Added interfaces: N4 and Service-Based Interface (SBI) N11 reference point.
- Added features: De-coupled Control Plane (CP) and User Plane (UP), Packet Forwarding Control Protocol (PFCP), Go Language (Golang) based SBI communication messages in REST on the N11 reference points.
- Partially implemented: Next Generation Application Protocol (NGAP).
- Handover procedure and application services are not supported in this stage.
- The implementation is based on nextEPC, an implementation of 4G EPC R13. That is, the MME, SGW and PGW are migrated into 5GC. However, Policy and Charging Rules Function (PCRF) and Home Subscriber Server (HSS) remain unchanged.
- Because commercial 5G User Equipment (UE) and base station (gNB) are not on the market yet, the free5GC uses 4G protocols to communicate with 4G UE and 4G base station (eNB) as shown in Fig. 1. Thus, the authentication protocol is still based on 4G. The protocols for 5G UEs and gNBs will be implemented in Stage 2 release.
Reference Architecture for Stage 1:
Fig. 1: Stage 1 architecture of free5GC
Stage 2 (released in October 2019): implementing the standalone 5GC features
- Removed interfaces: S6a and Gx.
- Supported network functions: Access and Mobility Management Function (AMF), Session Management Function (SMF), Network Repository Function (NRF), Network Slice Selection Function (NSSF), Unified Data Management (UDM), Unified Data Repository (UDR), and Authenticate Server Function (AUSF).
- Added interfaces: SBI N1 (UE - AMF), N2 (AN - AMF), N8 (Namf - Nudm), N10 (Nsmf – Nudm), N11 (Namf - Nsmf), N12 (Namf – Nausf), and N13 (Nausf – Nudm) reference points.
- Partially implementation: 5GC Orchestrator, Network Repository Function (NRF), and Network Slice Selection Function (NSSF).
- Added features: 5G Next Generation Application Protocol (NGAP), 5G Non-Access Stratum (NAS), and 5G authentication
- Features to be patched
- End of Oct: handover procedure, and paging
- End of Feb 2020: Policy Control Function (PCF) and QoS (to RAN)
- Application services are not supported in this stage.
Reference Architecture for Stage 2:
Fig. 2: Stage 2 architecture of free5GC
Stage 3 (released in April 2020): a full operational 5GC
- Support application service: IPTV
- Add features: Operation, Administration and Management (OAM) of 5GC, 5G Orchestrator.
- Add features: non-mobile access network (N3IWF) and UP Uplink Classifier (ULCL)