Ran node, radio terminal, and methods therefor
If uplink data together with an RRC resume request message is received from a radio terminal in an RRC_INACTIVE state and a radio terminal context is not available in a first RAN node ( 1 ), the first RAN node ( 1 ) sends a second type of control message to a second RAN node ( 2 ). The second type of control message requests the radio terminal context, and is distinct from a first type of control message that is sent to the second RAN node ( 2 ) by the first RAN node ( 1 ) when an RRC resume request message not accompanied by uplink data is received. This can contribute, for example, to enabling uplink (UL) data of a radio terminal in RRC_INACTIVE to be transmitted to a core network without relocating a radio terminal context from an old RAN node to a new RAN node.
1. A first Radio Access Network (RAN) node comprising:
at least one memory; and
at least one processor coupled to the at least one memory and configured to:
if a Radio Resource Control (RRC) resume request message not accompanied by uplink data is received from a radio terminal in an RRC_INACTIVE state and a radio terminal context of the radio terminal is not available in the first RAN node, send a first type of control message requesting the radio terminal context to a second RAN node that is a last serving RAN node for the radio terminal; and
if the uplink data together with the RRC resume request message is received, by the first RAN node, from the radio terminal in the RRC_INACTIVE state and the radio terminal context is not available in the first RAN node, then:
send to the second RAN node a second type of control message that requests the radio terminal context and is distinct from the first type of control message;
receive a third control message, from the second RAN node, after sending the second type of control message; and
send the uplink data, received from the radio terminal, to the second RAN node in response to the third control message indicating that the radio terminal context will not be relocated.
2. The first RAN node according to claim 1 , wherein the second type of control message is distinguished from the first type of control message by the fact that the second type of control message includes an indication indicating directly or indirectly presence of the uplink data.
3. The first RAN node according to claim 1 , wherein the second type of control message is distinguished from the first type of control message by the fact that the second type of control message includes an indication representing a request for transport network layer (TNL) information of the second RAN node.
4. The first RAN node according to claim 1 , wherein the at least one processor is configured to:
receive a third control message from the second RAN node after sending the second type of control message; and
send the uplink data to the second RAN node in response to the third control message indicating permission for an uplink data transfer via the second RAN node.
5. The first RAN node according to claim 1 , wherein the at least one processor is configured to send the uplink data to the second RAN node in response to receiving from the second RAN node, after sending the second type of control message, a third control message indicating transport network layer (TNL) information of the second RAN node.
6. The first RAN node according to claim 1 , wherein the second type of control message is distinguished from the first type of control message by the fact that the second type of control message contains the uplink data itself.
7. The first RAN node according to claim 6 , wherein the at least one processor is configured to include, in the second type of control message, additional information needed to identify or decipher the uplink data.
8. The first RAN node according to claim 7 , wherein the additional information includes one or both of a data radio bearer identifier and a logical channel identifier.
9. The first RAN node according to claim 1 , wherein the at least one processor is configured to:
receive type information indicating a type of data activity together with the uplink data from the radio terminal; and
inform the second RAN node of the type of the data activity via the second type of control message.
10. The first RAN node according to claim 9 , wherein the type of the data activity is selected from a plurality of types, including a first type in which only transmission of the uplink data occurs, a second type in which additional uplink data transmission is expected to occur subsequent to the transmission of the uplink data, and a third type in which downlink data transmission is expected to occur after the transmission of the uplink data.
11. The first RAN node according to claim 1 , wherein the at least one processor is configured to include, in the second type of control message, transport network layer (TNL) information of the first RAN node.
12. A radio terminal comprising:
at least one memory; and
at least one processor coupled to the at least one memory and configured to:
transmit uplink data and type information indicating a type of data activity, together with a Radio Resource Control (RRC) resume request message, to a Radio Access Network (RAN) node when the radio terminal is in an RRC_INACTIVE state,
wherein the uplink data is configured to be transmitted, from the RAN node, to another RAN node, in response to the RAN node receiving a first message indicating that a radio terminal context of the radio terminal will not be relocated.
13. The radio terminal according to claim 12 , wherein the at least one processor is configured to select the type of the data activity from a plurality of types, including a first type in which only transmission of the uplink data occurs, a second type in which additional uplink data transmission is expected to occur subsequent to the uplink data, and a third type in which downlink data transmission is expected to occur after the transmission of the uplink data.
14. The radio terminal according to claim 12 , wherein the type information is included in the RRC resume request message.
15. A method performed by a first Radio Access Network (RAN) node, the method comprising:
if a Radio Resource Control (RRC) resume request message not accompanied by uplink data is received from a radio terminal in an RRC_INACTIVE state and a radio terminal context of the radio terminal is not available in the first RAN node, sending a first type of control message requesting the radio terminal context to a second RAN node that is a last serving RAN node for the radio terminal; and
if the uplink data together with the RRC resume request message is received, by the first RAN node, from the radio terminal in the RRC_INACTIVE state and the radio terminal context is not available in the first RAN node, then:
sending to the second RAN node a second type of control message that requests the radio terminal context and is distinct from the first type of control message;
receiving a third control message, from the second RAN node, after sending the second type of control message; and
sending the uplink data received from the radio terminal to the second RAN node in response to the third control message indicating that the radio terminal context will not be relocated.
16. The first RAN node according to claim 1 , wherein the uplink data is data other than forwarding address information.
17. The first RAN node according to claim 1 , wherein the uplink data comprises user data.
18. The radio terminal according to claim 12 , wherein the at least one processor is further configured to receive an RRC RELEASE message from the RAN node, and
wherein the RRC RELEASE message is included in a second message, the second message being transmitted in response to the RAN node receiving the first message.
19. The method according to claim 15 , wherein the uplink data is data other than forwarding address information.
20. The method according to claim 15 , wherein the uplink data comprises user data.