User equipment (UE)
A UE receives, from a first base station apparatus, system information and/or a registration accept message including a first frequency band supported by the first base station apparatus, first S-NSSAI corresponding to a first frequency band, a second frequency band supported by a second base station apparatus, and second S-NSSAI corresponding to a second frequency band. The UE recognizes that a registration request message and/or a PDU session establishment request message including the second S-NSSAI is not transmittable via the first base station apparatus, and in a case of reselecting a cell of the second base station apparatus, recognizes that the registration request message and/or the PDU session establishment request message including the first S-NSSAI is not transmittable via the second base station apparatus. This prevents, in a 5GS, transmission of a registration request message and/or PDU session establishment request message which is unnecessary.
1 . A core network apparatus comprising:
transmission and reception circuitry,
wherein
in a case that a requested Network Slice Selection Assistance Information (NSSAI) received from a User Equipment (UE) contains at least one Single NSSAI (S-NSSAI) that is not available in a current tracking area, in a registration procedure over 3GPP access,
the transmission and reception circuitry is configured to:
transmit (i) an NSSAI including an S-NSSAI from the requested NSSAI not available in the current tracking area but available in another tracking area in a different frequency band and (ii) first information on the different frequency band associated with the S-NSSAI;
redirect the UE to a cell in the different frequency band based on the first information; and
in a case that the first information is updated, the transmission and reception circuitry is further configured to transmit second information on another frequency band associated with the S-NSSAI.
2 . A communication control method performed by a core network apparatus, the communication control method comprising:
in a case that a requested Network Slice Selection Assistance Information (NSSAI) received from a User Equipment (UE) contains at least one Single NSSAI (S-NSSAI) that is not available in a current tracking area, in a registration procedure over 3GPP access,
transmitting (i) an NSSAI including an S-NSSAI from the requested NSSAI not available in the current tracking area but available in another tracking area in a different frequency band and (ii) first information on the different frequency band associated with the S-NSSAI;
redirecting the UE to a cell in the different frequency band based on the first information; and
in a case that the first information is updated, transmitting second information on another frequency band associated with the S-NSSAI.