The present document defines the Stage 2 service description for the Evolved 3GPP Packet Switched Domain – also
known as the Evolved Packet System (EPS) in this document. The Evolved 3GPP Packet Switched Domain provides IP
connectivity using the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The specification covers both roaming and non-roaming scenarios and covers all aspects, including mobility between E- UTRAN and pre-E-UTRAN 3GPP radio access technologies, policy control and charging, and authentication. The Radio Access Network functionality is documented only to the extent necessary to describe the overall system. TS 36.300 [5] contains the overall description of the Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN). ITU-T Recommendation I.130 [3] describes a three-stage method for characterisation of telecommunication services, and ITU-T Recommendation Q.65 [4] defines Stage 2 of the method. TS 23.402 [2] is a companion specification to this specification. An Evolved Packet System architecture optimised for the support of Cellular IoT (Internet of Things) applications is also defined in this document. The Evolved Packet System also provides support for the E-UTRAN to control a Dual Connectivity radio connection that uses a combination of E-UTRA and another radio access technology (e.g. NR). TS 36.300 [5] contains the overall description for Dual Connectivity. Enhancements to support interworking of EPS with 5GS are captured in TS 23.501 [83] and TS 23.502 [84].