Method and apparatus for cellular internet of things (CIoT) data transfer over a control plane in a wireless communication system

1. A method of control plane messaging between a first entity and a second entity in a network in which control plane messages are sent in a control plane protocol, the method comprising:

sending from a user equipment (UE) to a core access and mobility management function (AMF), a control plane service request message;

starting a T3517 timer and entering a service request initiated state;

changing a mode of the UE from an idle mode to a connected mode; and

initiating transfer of user data, to the AMF, via a control plane, wherein said user data comprises cellular internet-of-things (CIoT) user data in a CIoT user data container, stored within a payload.

2. The method of claim 1 , further comprising:

including one or more protocol data unit (PDU) session identifications and one or more release assistance indications in the payload;

indicating a payload container type in a payload container type information element (IE) of the payload, wherein the payload container type is a CIoT user data container type;

indicating the payload container type to a user data container of the payload; and

sending an uplink non-access stratum transport message to the AMF.

3. The method of claim 1 , wherein the control plane service request message is sent from the UE to the AMF in response to either:

the UE being in the connected mode over 3GPP access and the UE receiving a paging request from the AMF,

the UE being in the connected mode over 3GPP access and receiving a notification from the AMF with an access type indicating non-3GPP access,

the UE being in the idle mode over 3GPP access and having uplink signalling pending,

the UE being in the idle mode over 3GPP access and having uplink user data pending,

the UE being in the connected mode, or in the connected mode with a radio resource control (RRC) inactive indication, and having user data pending due to no user-plane resources being established for one or more protocol data unit (PDU) sessions used for user data transport,

the UE being in the idle mode over non-3GPP access and receiving an indication from lower layers of the non-3GPP access, wherein an access stratum connection is established between the UE and the AMF,

the UE being in the idle mode over 3GPP access and receiving a notification from the AMF with access type indicating 3GPP access when the UE is in the connected mode over non-3GPP access, or

the UE being in the idle mode, in the connected mode over 3GPP access, or in the connected mode with the RRC inactive indication, and in response to receiving a request for emergency services fallback from one or more upper layers of the 3GPP access.

4. The method of claim 3 , wherein the control plane service request message is sent from the UE to the AMF in response to the UE being in the idle mode, in the connected mode over 3GPP access, or in the connected mode with the RRC inactive indication, and in response to receiving the request for emergency services fallback from the one or more upper layers of the 3GPP access, wherein the method further comprises:

performing emergency services fallback.

5. The method of claim 1 , wherein the control plane service request message is sent from the UE to the AMF in response to the UE being in the connected mode over 3GPP access or in the connected mode with a radio resource control (RRC) inactive indication, and in response to the UE receiving a fallback indication from one or more lower layers of the 3GPP access, or when the UE has a pending NAS procedure other than a registration procedure, a service request procedure, or a de-registration procedure.

6. A method of control plane messaging between entities in a network in which control plane messages are sent according to a control plane protocol, the method comprising:

receiving, from a user equipment (UE) or a session management function (SMF), at a core access and mobility management function (AMF), a control plane service request message; in an instance in which the AMF determines, based upon the control plane service request message, that the UE satisfies one or more conditions, sending, by the AMF, to the UE or the SMF, a service accept message; and

receiving, at the AMF, from the UE or the SMF, user data via a control plane, wherein said user data comprises cellular internet-of-things (CIoT) user data in a CIoT user data container, stored within a payload.

7. The method of claim 6 , further comprising:

initiating, based upon the control plane service request message and the user data, an authentication and key agreement procedure or an extensible authentication protocol.

8. The method of claim 6 , wherein the payload further comprises one or more protocol data unit (PDU) session identifications and one or more release assistance indications in the payload, wherein a payload container type is indicated in a payload container type information element (IE) of the payload as being a CIoT user data container type, and wherein the payload container type is indicated to a user data container of the payload, the method further comprising:

receiving, from the UE, an uplink non-access stratum transport message.

9. The method of claim 8 , further comprising:

identifying a PDU session routing context for the UE and the PDU session identification; and

forwarding the PDU session routing context of a payload container IE towards a session management function (SMF) identified by the PDU session routing context.

10. The method of claim 9 , further comprising:

in an instance in which a release assistance indication IE is included in the uplink non-access stratum transport message received from the UE, a downlink data expected (DDX) field of the release assistance indication IE indicates that no further uplink and no further downlink data transmission subsequent to the uplink data transmission is expected, and there is no downlink signalling or downlink data for the UE, initiating release of a connection and mobility management (N1) interface on a non-access stratum signaling connection.

11. An apparatus comprising at least one processor and at least one memory storing computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to:

send, to a core access and mobility management function (AMF), a control plane service request message;

start a T3517 timer and enter a service request initiated state;

change a mode of the apparatus from an idle mode to a connected mode; and

initiate transfer of user data, to the AMF, via a control plane, wherein said user data comprises cellular internet-of-things (CIoT) user data in a CIoT user data container, stored within a payload.

12. The apparatus of claim 11 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to:

include one or more protocol data unit (PDU) session identifications and one or more release assistance indications in the payload;

indicate a payload container type in a payload container type information element (IE) of the payload, wherein the payload container type is a CIoT user data container type;

indicate the payload container type to a user data container of the payload; and

send an uplink non-access stratum transport message to the AMF.

13. An apparatus comprising at least one processor and at least one memory storing computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to:

receive, from a user equipment (UE) or a session management function (SMF), at the apparatus, a control plane service request message;

in an instance in which the apparatus determines, based upon the control plane service request message, that the UE satisfies one or more conditions, send, to the UE or the SMF, a service accept message; and

receive, at the AMF, from the UE or the SMF, user data via a control plane, wherein said user data comprises cellular internet-of-things (CIoT) user data in a CIoT user data container, stored within a payload.

14. The apparatus of claim 13 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to:

initiate, based upon the control plane service request message and the user data, an authentication and key agreement procedure or an extensible authentication protocol.

15. A computer program product comprising a non-transitory computer-readable storage medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to:

send, from a user equipment (UE), to a core access and mobility management function, a control plane service request message;

start a T3517 timer and enter a service request initiated state;

change a mode of the UE from an idle mode to a connected mode; and

initiate transfer of user data, to the AMF, via a control plane, wherein said user data comprises cellular internet-of-things (CIoT) user data in a CIoT user data container, stored within a payload.

16. A computer program product comprising a non-transitory computer-readable storage medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to:

receive, from a user equipment (UE) or a session management function (SMF), at a core access and mobility management function (AMF), a control plane service request message;

in an instance in which the AMF determines, based upon the control plane service request message, that the UE satisfies one or more conditions, cause the AMF to send, to the UE or the SMF, a service accept message; and

receive, at the AMF, from the UE or the SMF, user data via a control plane, wherein said user data comprises cellular internet-of-things (CIoT) user data in a CIoT user data container, stored within a payload.