Radio access network node, radio terminal, core network node, and method therefor

1. A method in a target radio access network (RAN) node associated with a second network, the method comprising:

receiving, directly from a core network, core network context information about a handover of a radio terminal from a first network to the second network;

controlling communication of the radio terminal based on the core network context information; and

transferring, in response to receiving the core network context information, a handover signaling message on a direct interface between the target RAN node and a source RAN node associated with the first network,

wherein the core network context information includes slice information relating to a network slice, the network slice being included in the core network, and the radio terminal being configured to be connected to the network slice.

2. The method according to claim 1 , wherein the first network is a bearer-based network and the second network is a bearer-less network,

wherein the core network context information further includes flow information relating to at least one session to be established in the second network in order to transfer at least one packet flow of the radio terminal,

wherein said transferring comprises sending to the source RAN node, on the direct interface, the handover signaling message containing a transparent container,

wherein the transparent container contains at least one of:

a predetermined parameter included in the flow information; and

radio resource configuration information generated based on the flow information, and

wherein the transparent container is to be forwarded to the radio terminal by the source RAN node.

3. The method according to claim 2 , wherein the flow information includes a flow identifier and a flow QoS parameter in respect of each packet flow of the radio terminal.

4. The method according to claim 1 , wherein said transferring comprises sending to the source RAN node, on the direct interface, the handover signaling message containing a transparent container,

wherein the transparent container contains at least one of:

a predetermined parameter included in the slice information; and

radio resource configuration information generated based on the slice information, and

wherein the transparent container is to be forwarded to the radio terminal by the source RAN node.

5. The method according to claim 4 , wherein the slice information includes: (a) identification information of the network slice selected for the radio terminal; (b) type information of the network slice selected for the radio terminal; or (c) identification information of a network node or a network function associated with the network slice selected for the radio terminal; or any combination thereof.

6. The method according to claim 4 , wherein the slice information includes at least one of a mobility class and a session class that are supported by the network slice selected for the radio terminal.

7. The method according to claim 4 , further comprising determining, based on the slice information, whether to accept a bearer or flow of the radio terminal on a per-bearer or per-flow basis.

8. The method according to claim 4 , further comprising determining, based on the slice information, whether it is possible to accept each network slice.

9. The method according to claim 1 , wherein the core network context information further includes security related information including Non-Access Stratum (NAS) security configuration information and a security parameter used by the target RAN node to derive an Access Stratum (AS) security key,

wherein said transferring comprises sending to the source RAN node, on the direct interface, the handover signaling message containing a transparent container, and

wherein the transparent container contains the NAS security configuration information.

10. A method in a source radio access network (RAN) node associated with a first network, the method comprising:

receiving a measurement report from a radio terminal;

determining a handover of the radio terminal from the first network to a second network;

requesting, upon determining the handover, a core network to transmit core network context information, and receive the core network context information from the core network; and

sending a handover request message containing the core network context information to a target RAN node on a direct interface between the source RAN node and the target RAN node in order to start the handover,

wherein the core network context information includes at least one of flow information, slice information, and security-related information,

wherein the slice information relates to a network slice, the network slice being included in the second network, and the radio terminal being configured to be connected to the network slice,

wherein the flow information relates to at least one session to be established in the second network in order to transfer at least one packet flow of the radio terminal, and

wherein the security-related information includes Non-Access Stratum (NAS) security configuration information.

11. The method according to claim 10 , wherein the first network is a bearer-based network and the second networks is a bearer-less network,

wherein the core network context information includes the flow information,

wherein the method further comprises:

receiving from the target RAN node, on the direct interface, a handover request acknowledge message containing a transparent container; and

transmitting, to the radio terminal, a mobility command message containing the transparent container and indicating the handover to the second network, and

wherein the transparent container contains at least one of:

a predetermined parameter included in the flow information; and

radio resource configuration information generated by the target RAN node based on the flow information.

12. The method according to claim 11 , wherein the flow information includes a flow identifier and a flow QoS parameter in respect of each packet flow of the radio terminal.

13. The method according to claim 10 , wherein the core network context information includes the slice information,

wherein the method further comprises:

receiving from the target RAN node, on the direct interface, a handover request acknowledge message containing a transparent container; and

transmitting, to the radio terminal, a mobility command message containing the transparent container and indicating the handover to the second network, and

wherein the transparent container contains at least one of:

a predetermined parameter included in the slice information; and

radio resource configuration information generated by the target RAN node based on the slice information.

14. The method according to claim 12 , wherein the slice information includes: (a) identification information of the network slice selected for the radio terminal; (b) type information of the network slice selected for the radio terminal; or (c) identification information of a network node or a network function associated with the network slice selected for the radio terminal; or any combination thereof.

15. The method according to claim 13 , wherein the slice information includes at least one of a mobility class and a session class that are supported by the network slice selected for the radio terminal.

16. The method according to claim 10 , wherein the core network context information includes the security-related information including the Non-Access Stratum (NAS) security configuration information and a security parameter used by the target RAN node to derive an Access Stratum (AS) security key,

wherein the method further comprises:

receiving from the target RAN node, on the direct interface, a handover request acknowledge message containing a transparent container; and

transmitting, to the radio terminal, a mobility command message containing the transparent container and indicating a handover to the second network, and

wherein the transparent container contains the NAS security configuration information.

17. The method according to claim 10 , wherein the core network context information includes the slice information.