This disclosure discloses communication methods and apparatuses. One example method includes: obtaining slice information of a session, sending a first message to a network function repository function network element, and receiving identification information of an intermediate session management function network element from the network function repository function network element. The intermediate session management function network element is configured to manage an intermediate user plane function network element, and the intermediate user plane function network element is configured to forward service data between an access network device to which a terminal is connected and an anchor user plane function network element in response to the terminal moving out of a service area of the anchor user plane function network element and a service area of an anchor session management function network element.

A method for supporting redundant PDU session under intersystem change between 5GS and EPS is proposed. A UE maintains a PDU session that is a redundant PDU session, associated with a PDU session pair ID and/or a redundancy sequence number (RSN). When inter-system change from N1 mode to S1 mode occurs, the PDU session is transferred/mapped to a PDN connection. The UE shall associate the PDU session pair ID and/or the RSN with the PDN connection corresponding to the PDU session (e.g., associate with the default EPS bearer context of the PDN connection). When inter-system change from S1 mode to N1 mode occurs, the PDN connection is transferred/mapped back to the PDU session. The UE shall associate the PDU session pair ID and/or the RSN with the PDU session corresponding to the PDN connection.

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 user equipment (UE) is configured to determine a first access attempt to access a first network service is associated with a first access category, wherein the first access category is associated with a first Unified Access Control (UAC) rule, wherein the first UAC rule has a first priority and determine a second access attempt to access a second network service is associated with a second access category, wherein the second access category is associated with a second UAC rule, wherein the second UAC rule has a second priority.

A system is provided for supporting roaming between LTE EPC network and 5G network of a first mobile network operator by 5GC network of a second network operator. The system may include the EPC network including a serving gateway in communication with a 4G base station being in the EPC network. The system may also include the 5G network of the first mobile network operator including a vSMF in communication with a 5G base station being in the 5G network of the first network operator. The system may also include the 5GC network of the second network operator including a hSMF. The vSMF is configured to receive a communication from the serving gateway to anchor mobility between the LTE EPC network and the 5G network of the first mobile network operator, and to communicate with the hSMF in the 5GC network of the second network operator using 5G roaming interfaces.

Systems and methods are provided for optimizing use of wireless communication technologies for a UE. The method can include determining that the UE has established a first wireless communication link to a first node that can use both a first and a second wireless communication protocol, then determining whether, prior to connecting to the first node, the UE was previously connected to a second node that only utilizes the first wireless communication protocol (e.g., standalone 5G). If the UE was previously connected to the second node and moved to the first node because of fallback or handover procedures, a second communication link is established between the UE and the second node without analyzing single information corresponding to the UE.

A communication method is applied to a scenario in which a terminal moves from a first preset area of a first network to a second preset area of a second network. The method includes that a first core network device in the first network determines that Evolved Packet System (EPS) fallback of the terminal is triggered, and sends first information to a second core network device in the second network. The first information includes a first identifier or first indication information. The first identifier identifies a first dedicated bearer corresponding to the terminal. The first dedicated bearer includes a voice dedicated bearer or a video dedicated bearer. The first indication information indicates that the terminal falls back to the second network using an EPS fallback procedure.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may start, at a default data subscription (DDS) of the UE, a timer associated with a non-Third Generation Partnership Project (non-3GPP) tunnel over a cellular network based at least in part on a DDS switching at the UE. The UE may determine, at the DDS, that the non-3GPP tunnel over the cellular network is available prior to an expiry of the timer. The UE may perform a handover of a non-3GPP tunnel over data connection to the DDS based at least in part on the DDS switching at the UE and the non-3GPP tunnel over the cellular network being available prior to the expiry of the timer. Numerous other aspects are described.

An example electronic device includes at least one processor, wherein the at least one processor can be configured to confirm an event associated with an emergency service while registered to a first communication system, transmit a service request, corresponding to the event, to a network on the basis of the confirmation of the event, start, on the basis of the transmission of the service request, a timer having an end time that is shorter than the end time of a T3517 timer, search for and select, on the basis of failing to receive a response corresponding to the service request until the timer ends, a cell corresponding to a PLMN of a second communication system that excludes the first communication system, perform at least one operation for registration to the second communication system on the basis of the selected cell, and perform the emergency service corresponding to the event in the second communication system on the basis of the registration to the second communication system.

A method of enhancing session continuity for system interworking is proposed. Upon a UE performs inter-system change from A/Gb mode or Iu mode to S1 mode, the UE identifies that some PDN connection(s) are not associated with a PDU session ID (PSI). In one novel aspect, the UE deactivates all EPS bearer contexts for such PDN connection(s) locally, includes the EPS bearer context status IE in a TRACKING AREA UPDATE REQUEST message of a tracking area updating (TAU) procedure upon inter-system change from A/Gb mode or Iu mode to S1 mode, and then initiates UE requested PDN connectivity procedure(s) for such PDN connection(s). Furthermore, if no EPS bearer exists after local deactivation and EMM-REGISTERED without PDN connection is not supported by the UE, then the UE initiates a re-attach procedure followed by the UE requested PDN connectivity procedure(s) for such PDN connection (s) .