Method, device, and system for core network device re-allocation in wireless network
This disclosure generally relates performing UE authentication and registration with the core network, and in particular, to supporting secure interactions between the UE and the target AMF when the UE is re-allocated to the target AMF. During a UE registration procedure, the initial AMF generate a 5G-GUTI for the UE and retrieves a candidate AMF list. The initial AMF sends the generated 5G-GUTI (or 5G-S-TMSI), the candidate AMF list, and a full registration request message to the (R)AN for storage and subsequent use. The initial AMF, once determines an AMF re-allocation is needed, instruct the UE to re-start the registration procedure with the core network, by using the generated 5G-GUTI. The (R)AN selects the target AMF, and forward the stored full registration request message to the target AMF to complete the registration.
1 . A method for performing secure re-allocation of a UE from an initial core network element to a target core network element in a communication network, performed by the initial core network element, the method comprising:
receiving, from a first network element, a first message comprising a list of candidate core network elements;
during a first registration procedure triggered by a first registration request initiated by the UE via a first registration request message, and in response to receiving the first message, generating a first UE identifier for the UE;
transmitting, to an access network element of the communication network, a second message comprising the list of candidate core network elements, a second UE identifier based on the first UE identifier, and a second registration request message, wherein the second message comprises a Reroute Non Stratum Access (NAS) message; and
transmitting, to the UE, a third message indicating that the first registration request is accepted, the third message comprising the first UE identifier, wherein the third message is different from the second message.
2 . The method of claim 1 , wherein before receiving the first message, the method further comprises:
determining that the initial core network element does not support at least one of:
a network slice subscribed by the UE; or
a network function subscribed by the UE.
3 . The method of claim 1 , wherein:
before receiving the first message, the method further comprises transmitting a Nnrf_NFDiscovery_request message to the first network element; and
the first message is received in response to the Nnrf_NFDiscovery_request message and comprises a Nnrf_NFDiscovery_response message.
4 . The method of claim 1 , wherein the first network element comprises a Network Repository Function (NRF).
5 . The method of claim 1 , wherein:
before receiving the first message, the method further comprises receiving a third registration request message from the access network element, the third registration request message being based on the first registration request message; and
transmitting, to the access network element of the communication network, the second message comprises:
in response to receiving a fourth registration request message from the UE after receiving the third registration request message, transmitting, to the access network element of the communication network, the second message comprising the list of candidate core network elements, the second UE identifier based on the first UE identifier, and the second registration request message based on the fourth registration request message; and
in response to not receiving the fourth registration request message from the UE after receiving the third registration request message, transmitting, to the access network element of the communication network, the second message comprising the list of candidate core network elements, the second UE identifier based on the first UE identifier, and the second registration request message based on the third registration request message.
6 . The method of claim 1 , wherein the first UE identifier comprises a 5G Global Unique Temporary Identifier (5G-GUTI) and the second UE identifier comprises a 5G S-Temporary Mobile Subscriber Identity (5G-S-TMSI).
7 . The method of claim 1 , further comprising:
transmitting an N2 UE context release message to the access network element, the N2 UE context release message being used to release an N2 signaling connection for the UE between the access network element and the initial core network element.
8 . The method of claim 7 , wherein the N2 UE context release message further triggers the access network element to release a radio access network connection with the UE and delete a context of the UE.
9 . The method of claim 1 , further comprising:
transmitting, to the UE, a fourth message triggering the UE to start a second registration procedure based on the first UE identifier, the second registration procedure being subsequent to the first registration procedure.
10 . The method of claim 9 , wherein the fourth message comprises one of:
a UE configuration update command; or
a de-registration request message.
11 . The method of claim 10 , wherein the UE configuration update command is indicative of requesting a UE registration.
12 . The method of claim 10 , wherein the de-registration request message is indicative of requesting a UE registration.
13 . The method of claim 9 , wherein:
the fourth message is configured to trigger the UE to transmit a fifth registration request message to the access network element for registering with the target core network element based on the first UE identifier, the fifth registration request message comprising an information element based on the first UE identifier, the first UE identifier being indicative of the target core network element.
14 . The method of claim 13 , further comprising:
in response to receiving the fifth registration request message:
selecting, by the access network element, the target core network element from the list of candidate core network elements based on one of:
the first UE identifier carried in the fifth registration request message;
the second UE identifier carried in the fifth registration request message; or
the second UE identifier carried in a fifth message transmitted from the UE to the access network element; and
transmitting, by the access network element to the target core network element, the second registration request message.
15 . The method of claim 14 , wherein transmitting, by the access network element to the target core network element, the second registration request message comprises:
transmitting, by the access network element to the target core network element, the second registration request message via an initial UE message.
16 . The method of claim 1 , wherein at least one of the initial core network element or the target core network element comprises an AMF.
17 . A device comprising a memory for storing computer instructions and a processor in communication with the memory, wherein, when the processor executes the computer instructions, the processor is configured to cause the device to:
receive, from a first network element, a first message comprising a list of candidate core network elements;
during a first registration procedure triggered by a first registration request initiated by a UE via a first registration request message, and in response to receiving the first message, generate a first UE identifier for the UE;
transmit, to an access network element, a second message comprising the list of candidate core network elements, a second UE identifier based on the first UE identifier, and a second registration request message, wherein the second message comprises a Reroute Non Stratum Access (NAS) message; and
transmit, to the UE, a third message indicating that the first registration request is accepted, the third message comprising the first UE identifier, wherein the third message is different from the second message.
18 . A non-transitory storage medium for storing computer readable instructions, the computer readable instructions, when executed by a processor, causing the processor to:
receive, from a first network element, a first message comprising a list of candidate core network elements, the first message comprising a response message to an Nnrf_NFDiscovery_Request message;
during a first registration procedure triggered by a first registration request initiated by a UE via a first registration request message, and in response to receiving the first message, generate a first UE identifier for the UE;
transmit, to an access network element, a second message comprising the list of candidate core network elements, a second UE identifier based on the first UE identifier, and a second registration request message, wherein the second message comprises a Reroute Non Stratum Access (NAS) message; and
transmit, to the UE, a third message indicating that the first registration request is accepted, the third message comprising the first UE identifier, wherein the third message is different from the second message.