RELAY DEVICE, BASE STATION, AND WIRELESS COMMUNICATION SYSTEM

1 . A relay device comprising:

a controller configured to execute a first process when a state of RRC transitions from a first state to a second state;

a transmitter configured to transmit a first signal for transitioning the state of the RRC from the second state to a third state according to the first process; and

a receiver configured to receive a transmitted second signal in response to the first signal,

wherein the controller transitions the state of the RRC from the second state to the third state according to the second signal.

2 . The relay device according to claim 1 , wherein

the transmitter transmits a third signal when the transition to the third state is completed.

3 . The relay device according to claim 1 , wherein

the first state is an RRC inactive state, and

the second state is an RRC idle state, and

the third state is RRC connected state.

4 . The relay device according to claim 3 , wherein

the first process includes a process of notifying first information from an RRC layer to a NAS layer and a process of determining whether or not the first information corresponds to second information by the NAS layer, and

the first process includes, when the first information corresponds to the second information, a process of triggering a second process, and the second process includes a process of controlling to transmit a fourth signal that is a signal of the NAS layer from the transmitter.

5 . The relay device according to claim 4 , wherein

the first information is information corresponding to a cause of transition to the second state among a plurality of pieces of information that are causes of transition of the state of the RRC to the second state, and

the second information corresponds to at least one of the plurality of pieces of information.

6 . The relay device according to claim 5 , wherein

each of the plurality of pieces of information corresponds to a respective one of a plurality of release causes, and the plurality of release causes include at least a first cause, a second cause, and a third cause,

the second information corresponds to the first cause and the second cause,

the first process includes a process of notifying, when transition is made from the first state to the second state, the NAS layer of the first cause or the second cause as the first information from the RRC layer, and

the third cause is, when a state of RRC of a terminal transitions from the RRC inactive state to the RRC idle state in the terminal, a cause notified from the RRC layer of the terminal to the NAS layer.

7 . The relay device according to claim 5 , wherein

each of the plurality of pieces of information corresponds to a respective one of a plurality of release causes, and the plurality of release causes include at least a first cause, a second cause, and a third cause,

the second information corresponds to the first cause, the second cause, and the third cause,

the first process includes a process of notifying, when transition is made from the first state to the second state, the NAS layer of the third cause as the first information from the RRC layer, and

the third cause is, when a state of RRC of a terminal transitions from the RRC inactive state to the RRC idle state in the terminal, a cause notified from the RRC layer of the terminal to the NAS layer.

8 . The relay device according to claim 5 , wherein each of the plurality of pieces of information corresponds to respective one of a plurality of release causes, and the plurality of release causes includes at least a first cause, a second cause, a third cause, and a fourth cause,

the second information corresponds to the first cause, the second cause, and the fourth cause,

the first process includes a process of notifying, when transition is made from the first state to the second state, the NAS layer of the fourth cause as first information from the RRC layer,

the first cause, the second cause, and the third cause are similar to a cause transmitted when a state of RRC of a terminal transitions to an idle state in the terminal, and

the fourth cause is a cause used when the relay device transitions from the first state to the second state in the terminal, and is different from the first cause, the second cause, and the third cause.

9 . The relay device according to claim 1 , wherein

the first process includes a process of notifying a NAS layer from an RRC layer of transition information indicating that transition is made to the second state, and

the NAS layer includes a process of controlling to trigger a second process including a process of transmitting a fourth signal that is a signal of the NAS layer according to the transition information.

10 . A base station comprising:

a receiver configured to receive, when a state of RRC of a relay device transitions from a first state to a second state, a first signal for transitioning the state of the RRC from the second state to a third state, the first signal being transmitted from the relay device according to a first process executed by the relay device; and

a transmitter configured to transmit a second signal for causing the state of the RRC of the relay device to transition from the second state to the third state according to the first signal.

11 . A wireless communication system including a relay device that relays a signal transmitted from a base station to a terminal,

wherein the relay device comprises:

a controller configured to execute a first process when a state of RRC transitions from a first state to a second state; and

a first transmitter configured to transmit a first signal for transitioning the state of the RRC from the second state to a third state according to the first process, and

wherein the base station includes:

a receiver configured to receive the first signal; and

a second transmitter configured to transmit a second signal for causing the state of the RRC of the relay device to transition from the second state to the third state according to the first signal.