6.4 Relationship between MM and SM states for an UE
23.2213GPPArchitectural requirementsRelease 17TS
When a UE is attached to PS service, it may have, but need not have, some EPS Bearer/PDP context established with GERAN or UTRAN Access. With E-UTRAN access a PS attached UE has at least one EPS Bearer context established.
If the UE has no EPS Bearer/PDP context established (SM-Inactive), no radio access bearer are established for PS service. The UE is in RRC connected mode, only if the state is CS-CONNECTED state or PS-CONNECTED state (i.e. only a PS signalling connection is established).
If the UE has at least one EPS Bearer/PDP context established (SM-Active), the UE can be in PS-CONNECTED state or in PS-IDLE state.
NOTE: The EPS Bearer/PDP context status is not modified by the release of the RRC connection, except if the release of the connection is due to an RRC failure which do not permit to maintain the negotiated QoS (e.g. a real time connection).