Disclosed are: a communication technique for merging, with IoT technology, a 5G communication system for supporting a data transmission rate higher than that of a 4G system; and a system therefor. The present disclosure can be applied to intelligent services (for example, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail, security, and safety-related services, and the like) on the basis of 5G communication technology and IoT-related technology. Disclosed are a method and a device for supporting the connection of a terminal operating in an RRC inactivation mode.

A method for handling a PDU session release command for releasing an MA PDU session with a PDN connection established as user-plane resource on 3GPP access is proposed. For an MA PDU session with both EPS/4G 3GPP leg and 5GS non-3GPP leg, if UE/NW wants to release the MA PDU session, UE/NW needs to initiate two procedures. First/Second, to release the EPS 3GPP leg, UE/NW should initiate a PDN disconnect procedure/deactivate EPS bearer context procedure or a detach procedure. Second/First, to release the 5GS non-3GPP leg, UE/NW should initiate a PDU session release procedure. The UE/NW can also initiate two procedures simultaneously. It is also possible that the UE initiates one procedure and the NW initiates the other procedure.

A method for handling a PDU session release command for releasing an MA PDU session with a PDN connection established as user-plane resource on 3GPP access is proposed. For an MA PDU session with both EPS/4G 3GPP leg and 5GS non-3GPP leg, if UE/NW wants to release the MA PDU session, UE/NW needs to initiate two procedures. First/Second, to release the EPS 3GPP leg, UE/NW should initiate a PDN disconnect procedure/deactivate EPS bearer context procedure or a detach procedure. Second/First, to release the 5GS non-3GPP leg, UE/NW should initiate a PDU session release procedure. The UE/NW can also initiate two procedures simultaneously. It is also possible that the UE initiates one procedure and the NW initiates the other procedure.

A method of handling multi-access (MA) Protocol data unit (PDU) session establishment procedure for adding a 3GPP PDN leg to an MA PDU session already established with a non-3GPP leg is proposed. In one novel aspect, for a 5GS MA PDU session already established on non-3GPP access, upon receipt of an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message for establishing a PDN connection as a user-plane resource for the MA PDU session over 3GPP access, the UE sends an ACTIVATE DEFAULT EPS BEARER CONTEXT REJECT message if any value of at least one of the critical parameters, including the PDN type, ESM cause, PDN address, S-NSSAI, SSC mode (set to SSC mode 1), and APN IEs in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message does not match/sync/compatible to the corresponding stored value of the MA PDU session with a non-3GPP leg.

A method of handling multi-access (MA) Protocol data unit (PDU) session establishment procedure for adding a 3GPP PDN leg to an MA PDU session already established with a non-3GPP leg is proposed. In one novel aspect, for a 5GS MA PDU session already established on non-3GPP access, upon receipt of an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message for establishing a PDN connection as a user-plane resource for the MA PDU session over 3GPP access, the UE sends an ACTIVATE DEFAULT EPS BEARER CONTEXT REJECT message if any value of at least one of the critical parameters, including the PDN type, ESM cause, PDN address, S-NSSAI, SSC mode (set to SSC mode 1), and APN IEs in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message does not match/sync/compatible to the corresponding stored value of the MA PDU session with a non-3GPP leg.

A method of handling multi-access (MA) Protocol data unit (PDU) session establishment procedure for an MA PDU session already established with a 3GPP PDN leg is proposed. In one novel aspect, for a 5GS MA PDU session already established on 3GPP access via an EPS PDN connection, upon receipt of a PDU SESSION ESTABLISHMENT ACCEPT message over non-3GPP access, the UE performs a local release of the MA PDU session if any value of at least one of the critical MA PDU session parameters, including the PDU session type, selected SSC mode, 5GSM cause, PDU address, S-NSSAI, and DNN IEs in the PDU SESSION ESTABLISHMENT ACCEPT message is different-from/un-sync/not-matched/not-compatible-with the corresponding stored value of the MA PDU session mapped from the (default EPS bearer of the) PDN connection. The UE also performs a REGISTRATION procedure over non-3GPP access and a TAU procedure over 3GPP access.

A method of handling multi-access (MA) Protocol data unit (PDU) session establishment procedure for an MA PDU session already established with a 3GPP PDN leg is proposed. In one novel aspect, for a 5GS MA PDU session already established on 3GPP access via an EPS PDN connection, upon receipt of a PDU SESSION ESTABLISHMENT ACCEPT message over non-3GPP access, the UE performs a local release of the MA PDU session if any value of at least one of the critical MA PDU session parameters, including the PDU session type, selected SSC mode, 5GSM cause, PDU address, S-NSSAI, and DNN IEs in the PDU SESSION ESTABLISHMENT ACCEPT message is different-from/un-sync/not-matched/not-compatible-with the corresponding stored value of the MA PDU session mapped from the (default EPS bearer of the) PDN connection. The UE also performs a REGISTRATION procedure over non-3GPP access and a TAU procedure over 3GPP access.

A wireless device receives one or more messages indicating a first time alignment timer (TAT), of a cell, associated with a small data transmission (SDT) procedure in a radio resource control (RRC) inactive state, and indicating a second TAT, of the cell, associated with a random access. The wireless device transmits, during the SDT procedure, a signal via an uplink control channel of the cell based on one TAT, of the first TAT or the second TAT, being expired, and based on another TAT, of the first TAT or the second TAT, running.

A wireless device receives one or more messages indicating a first time alignment timer (TAT), of a cell, associated with a small data transmission (SDT) procedure in a radio resource control (RRC) inactive state, and indicating a second TAT, of the cell, associated with a random access. The wireless device transmits, during the SDT procedure, a signal via an uplink control channel of the cell based on one TAT, of the first TAT or the second TAT, being expired, and based on another TAT, of the first TAT or the second TAT, running.

This disclosure provides systems, devices, apparatus, and methods, including computer programs encoded on storage media, for GNSS validity reporting in NTNs. A UE may transmit, to a network entity, a report of a validity duration for GNSS tracking information. The GNSS tracking information may be associated with an NTN including the UE and the network entity. The report may include an indication of a remaining time period of the validity duration based on a threshold. The UE may switch to an RRC idle mode based on the report of the validity duration. The RRC idle mode may be switched to after an expiration of the remaining time period of the validity duration or based on an RRC release message received from the network entity.