US 11,943,700 B2
User device
Kenichiro Aoyagi, Tokyo (JP); Hiroshi Ishikawa, Tokyo (JP); Atsushi Minokuchi, Tokyo (JP); and Shinya Takeda, Tokyo (JP)
Assigned to NTT DOCOMO, INC., Tokyo (JP)
Appl. No. 16/960,774
Filed by NTT DOCOMO, INC., Tokyo (JP)
PCT Filed Sep. 12, 2018, PCT No. PCT/JP2018/033797
§ 371(c)(1), (2) Date Jul. 8, 2020,
PCT Pub. No. WO2019/138604, PCT Pub. Date Jul. 18, 2019.
Claims priority of application No. 2018-002998 (JP), filed on Jan. 11, 2018.
Prior Publication US 2020/0336979 A1, Oct. 22, 2020
Int. Cl. H04W 48/20 (2009.01); H04W 36/00 (2009.01); H04W 48/16 (2009.01)
CPC H04W 48/16 (2013.01) [H04W 36/0022 (2013.01); H04W 48/20 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A user device comprising:
a receiver that, in a state in which the user device is in an IDLE state as a radio connection between the user device and a first system, detects a state that access to the first system is barred in a first cell of the first system, the first system supporting IP multimedia subsystem-type communication service, and the first cell being formed by a first radio access network in the first system;
a processor that selects, without the user device leaving the IDLE state in which the user device has not established the radio connection with the first system, a second cell of a second system as a target cell for connection based on the state detected by the receiver that access to the first system is barred, the second system supporting the IP multimedia subsystem-type communication service, the second cell being formed by a second radio access network in the second system, and the second radio access network being a different type of radio access network from the first radio access network; and
a transmitter that transmits a connection request signal for the IP multimedia subsystem-type communication service to the target cell for connection.