Patent Publication Number: US-2022232506-A1

Title: NID Provisioning under UE Mobility Scenarios

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. § 119 from U.S. Provisional Application No. 63/139,827, entitled “NID Provisioning under UE Mobility Scenarios”, filed on Jan. 21, 2021, the subject matter of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate generally to wireless mobile communication network, and, more particularly, to method of Network Identifier (NID) provisioning under User Equipment (UE) mobility scenarios. 
     BACKGROUND 
     A Public Land Mobile Network (PLMN) is a network established and operated by an administration or recognized operating agency (ROA) for the specific purpose of providing land mobile communication services to the public. PLMN provides communication possibilities for mobile users. A PLMN may provide service in one or a combination of frequency bands. Access to PLMN services is achieved by means of an air interface involving radio communications between mobile phones and base stations with integrated IP network services. One PLMN may include multiple radio access networks (RAN) utilizing different radio access technologies (RAT) for accessing mobile services. A radio access network is part of a mobile communication system, which implements a radio access technology. Conceptually, RAN resides between a mobile device and provides connection with its core network (CN). Depending on the standard, mobile phones and other wireless connected devices are varyingly known as user equipment (UE), terminal equipment, mobile stations (MS), etc. Examples of different RATs include 2G GERAN (GSM) radio access network, 3G UTRAN (UMTS) radio access network, 4G E-UTRAN (LTE), 5G new radio (NR) radio access network, and other non-3GPP access RAT including WiFi. 
     As compared to PLMN, a non-public network (NPN) is a 5GS deployed network for non-public use. An NPN is either a Stand-alone Non-Public Network (SNPN), i.e., operated by an NPN operator and not relying on network functions provided by a PLMN; or a Public Network Integrated NPN (NPI-NPN), i.e., a non-public network deployed with the support of a PLMN. The combination of a PLMN ID and Network identifier (NID) identifies an SNPN. NID information refers to the entire NID value or partial NID value (e.g., the first digit of the NID value). A UE may be enabled for SNPN. The UE selects an SNPN for which it is configured with a subscriber identifier and credentials. The UE can have several sets of subscriber identifiers, credentials, and SNPN identities. 
     When a UE is moving within a PLMN or between the PLMNs, the UE triggers the mobility registration update procedure and provides a 5G Global Unique Temporary Identifier (5G-GUTI) to the target AMF of the target PLMN, to assist the target AMF to find the correct source AMF for retrieving the UE context for the subsequent procedures. However, a UE may move between different type of networks. For example, the UE may move within a PLMN, within a SNPN, between a PLMN and a SNPN, between two different PLMNs, between two different SNPNs, or between a PLMN and a SNPN. If the provided 5G-GUTI is assigned by an SNPN, the target AMF of the target network may not be able to find the correct source AMF since the derived information from the provided 5G-GUTI is not (globally) unique and may lead to find incorrect source AMF and finally the mobility registration update procedure may proceed to an un-anticipated exception condition or fail. As a result, the UE then needs to initiate an initial registration procedure. 
     The existing registration procedures need to be enhanced to resolve this issue. 
     SUMMARY 
     A method supporting enhanced network identity (NID) provisioning under User Equipment (UE) mobility scenarios between different types of networks is proposed. When a UE registers to an SNPN, the UE is assigned with a 5G-GUTI by the SNPN. The SNPN is identified by an SNPN ID==PLMN ID+NID. When the UE moves from the SNPN to another target network having a target AMF, the UE triggers a mobility registration update procedure and provides the 5G-GUTI along with NID information in a Registration Request to the target AMF. The target AMF can use the NID information along with the 5G-GUTI to find a source AMF for deriving UE context for the subsequent operations during the mobility registration update procedure. Providing NID information along with 5G-GUTI can assist the target AMF to find the source AMF efficiently, preventing a potential registration procedure failure. 
     In one embodiment, a UE registers to a stand-alone non-public network (SNPN). The SNPN is identified by a Public Land Mobile Network (PLMN) ID and a Network Identifier (NID). The UE determines that a 5G Global Unique Temporary Identifier (5G-GUTI) is assigned to the UE by the SNPN. The UE triggers a mobility registration update procedure and transmits a registration request to a target access and mobility function (AMF) of a target network. The registration request comprises the 5G-GUTI and NID information of the SNPN. The UE performs the mobility registration update procedure with the target network. 
     In another embodiment, a network entity (target AMF) receives a registration request from a User Equipment (UE) in a target network. The registration request triggers a mobility registration update procedure. The target AMF receives a 5G Global Unique Temporary Identifier (5G-GUTI) and Network Identifier (NID) information of a source network. The source network is a stand-alone non-public network (SNPN) identified by a Public Land Mobile Network (PLMN) ID and a NID. The target AMF determines a source AMF using the received 5G-GUTI and the NID information. The target AMF performs the mobility registration update procedure for the UE. The target AMF acquires UE context information from the source AMF. 
     Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows a communication system having a Public Land Mobile Network (PLMN) and a Stand-alone Non-public Network (SNPN) supporting enhanced network identifier (NID) provisioning under UE mobility in accordance with one novel aspect. 
         FIG. 2  illustrates simplified block diagrams of a user equipment and a network entity in accordance with embodiments of the current invention. 
         FIG. 3A  shows the content of a 5G Global Unique Temporary Identifier (5G-GUTI), and examples when assigned by PLMN and by SNPN. 
         FIG. 3B  shows one example of NID assignment based on different Assignment modes. 
         FIG. 4  illustrates a mobility registration update procedure where a UE moves from a source AMF to a target AMF, with enhanced NID provisioning in accordance with one novel aspect. 
         FIG. 5  is a flow chart of a method supporting enhanced NID provisioning under UE mobility scenarios between different types of networks from UE perspective in accordance with one novel aspect. 
         FIG. 6  is a flow chart of a method supporting enhanced NID provisioning under UE mobility scenarios between different types of networks from NW perspective in accordance with one novel aspect. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  schematically shows a communication system  100  having a Public Land Mobile Network (PLMN)  110  and a Stand-alone Non-public Network (SNPN)  120  supporting enhanced network identifier (NID) provisioning under UE mobility in accordance with one novel aspect. PLMN network  110  comprises control plane functionalities, user plane functionality (UPF), and application servers that provides various services by communicating with a plurality of user equipments (UEs) including UE  111 . UE  111  and its serving base station gNB  112  belong to part of a radio access network RAN  130 . RAN  130  provides radio access for UE  111  via a radio access technology (RAT), e.g. 3GPP access and non-3GPP access. An access and mobility management function (AMF) in PLMN  110  communicates with gNB  112 , and other network functions such as Session Management Function (SMF), Authentication Server Function (AUSF), etc. in PLMN  110  (not shown). 
     Similarly, SNPN network  120  comprises control plane functionalities, user plane functionality (UPF), and application servers that provides various services by communicating with a plurality of user equipments (UEs) including UE  121 . The combination of a PLMN ID and a Network identifier (NID) identifies an SNPN. UE  121  and its serving base station gNB  122  belong to part of a radio access network RAN  140 . RAN  140  provides radio access for UE  121  via a radio access technology (RAT), e.g. 3GPP access and non-3GPP access. An AMF in SNPN  120  communicates with gNB  122 , and other network functions such as SMF, AUSF etc. in SNPN  120  (not shown). UE  111 /UE  121  may be equipped with a radio frequency (RF) transceiver or multiple RF transceivers for different application services via different RATs. 
     When a UE is moving within a PLMN or between the PLMNs, the UE triggers the mobility registration update procedure and provides a 5G Global Unique Temporary Identifier (5G-GUTI) to the target AMF of the target PLMN, to assist the target AMF to find the correct source AMF for retrieving the UE context for the subsequent procedures. However, a UE may move between different type of networks. For example, the UE may move within a PLMN, within a SNPN, between a PLMN and a SNPN, between two different PLMNs, between two different SNPNs, or between a PLMN and a SNPN. If the provided 5G-GUTI is assigned by an SNPN, it may not be a globally unique number. As a result, the target AMF of the target network may not be able to find the correct source AMF, since the derived information from the provided non-unique 5G-GUTI may lead to find incorrect source AMF. Therefore, the mobility registration update procedure may proceed to an un-anticipated exception condition or fail. The UE then needs to initiate an initial registration procedure with the target AMF. 
     In accordance with one novel aspect, a method of enhanced NID provisioning method is proposed to handle different UE mobility scenarios. When a UE registers to an SNPN, the UE is assigned with a 5G-GUTI by the SNPN. The SNPN is identified by an SNPN ID==PLMN ID+NID. When the UE moves from the SNPN to another target network having a target AMF, the UE triggers a mobility registration update procedure and provides the 5G-GUTI to the target AMF. For example, UE  121  moves from SNPN  120  to PLMN  110 . Since the UE is aware of the SNPN ID when the UE registers to the SNPN, the UE knows that the 5G-GUTI assigned by the SNPN may not be globally unique. Therefore, the existing mobility registration update procedure is enhanced to allow the UE to provide the 5G-GUTI with NID information if the UE knows the 5G-GUTI is assigned by an SNPN. After receiving the 5G-GUTI and NID information provided by the UE, the target AMF can decides whether to initiate the Identity request/respond procedure based on the NID assignment mode. If NID is self-assigned value, the value of PLMN ID (of the 5G-GUTI)+NID may not be (globally) unique. Therefore, the target AMF may need to request the UE to provide UE SUCI/SUPI for the subsequent procedures. If NID is coordinated assigned value, the value of PLMN ID (of the 5G-GUTI)+NID is (globally) unique. Therefore, the target AMF can use the information along with 5G-GUTI to find the correct source AMF. In the example of  FIG. 1 , when UE  121  moves from SNPN  120  to PLMN  112 , UE  121  triggers a mobility registration update procedure and provides its 5G-GUTI with NID information to the target AMF in PLMN  110 , since UE  121  knows the 5G-GUTI is assigned by SNPN  120  and may not be unique. The NID information can assist the target AMF to find the source AMF in SNPN  120  efficiently, preventing potential failure of the mobility registration update procedure. 
       FIG. 2  illustrates simplified block diagrams of wireless devices, e.g., a UE  201  and network entity  211  in accordance with embodiments of the current invention. Network entity  211  may be a base station combined with an MME or AMF. Network entity  211  has an antenna  215 , which transmits and receives radio signals. A radio frequency RF transceiver module  214 , coupled with the antenna, receives RF signals from antenna  215 , converts them to baseband signals and sends them to processor  213 . RF transceiver  214  also converts received baseband signals from processor  213 , converts them to RF signals, and sends out to antenna  215 . Processor  213  processes the received baseband signals and invokes different functional modules to perform features in base station  211 . Memory  212  stores program instructions and data  220  to control the operations of base station  211 . In the example of  FIG. 2 , network entity  211  also includes a set of control functional modules and circuit  290 . Registration circuit  231  handles registration and mobility procedure. Session management circuit  232  handles session management functionalities. Configuration and control circuit  233  provides different parameters to configure and control UE. 
     Similarly, UE  201  has memory  202 , a processor  203 , and radio frequency (RF) transceiver module  204 . RF transceiver  204  is coupled with antenna  205 , receives RF signals from antenna  205 , converts them to baseband signals, and sends them to processor  203 . RF transceiver  204  also converts received baseband signals from processor  203 , converts them to RF signals, and sends out to antenna  205 . Processor  203  processes the received baseband signals and invokes different functional modules and circuits to perform features in UE  201 . Memory  202  stores data and program instructions  210  to be executed by the processor to control the operations of UE  201 . Suitable processors include, by way of example, a special purpose processor, a digital signal processor (DSP), a plurality of micro-processors, one or more micro-processor associated with a DSP core, a controller, a microcontroller, application specific integrated circuits (ASICs), file programmable gate array (FPGA) circuits, and other type of integrated circuits (ICs), and/or state machines. A processor in associated with software may be used to implement and configure features of UE  201 . 
     UE  201  also comprises a set of functional modules and control circuits to carry out functional tasks of UE  201 . Protocol stacks  260  comprise Non-Access-Stratum (NAS) layer to communicate with an MME or an AMF entity connecting to the core network, Radio Resource Control (RRC) layer for high layer configuration and control, Packet Data Convergence Protocol/Radio Link Control (PDCP/RLC) layer, Media Access Control (MAC) layer, and Physical (PHY) layer. System modules and circuits  270  may be implemented and configured by software, firmware, hardware, and/or combination thereof. The function modules and circuits, when executed by the processors via program instructions contained in the memory, interwork with each other to allow UE  201  to perform embodiments and functional tasks and features in the network. In one example, system modules and circuits  270  comprise registration circuit  221  that performs registration procedure with the network, a mobility handling circuit  222  that handles mobility management, a config and control circuit  223  that handles configuration and control parameters. 
       FIG. 3A  shows the content of a 5G Global Unique Temporary Identifier (5G-GUTI), and examples when assigned by PLMN and by SNPN. A temporary user identity for 5GS-based services, the 5G-GUTI, is used for identification within the signalling procedures. Upon receiving a Registration Request message of type “initial registration” or “mobility registration update” from a UE, the AMF sends a new 5G-GUTI to the UE in Registration Accept message. Upon receiving a Registration Request message of type “periodic registration update” from a UE, the AMF sends a new 5G-GUTI to the UE in Registration Accept message. Upon receiving a network triggered Service Request Message from a UE, the AMF uses a UE Configuration Update procedure to send a new 5G-GUTI to the UE. The 5G-GUTI has two main components: the Global Unique AMF Identifier (GUAMI) and the 5G-TMSI that provides an unambiguous identity of the UE within the AMF(s) identified by the GUAMI. GUAMI further comprises two network identifiers: PLMN ID and AMF ID. PLMN ID comprises a mobile country code (MCC) and a mobile network code (MNC). 
     In case of PLMN, the assigned 5G-GUTI is globally unique. When UE moves between PLMNs, UE provides 5G-GUTI in Registration Request to Target AMF. Target AMF derives the information of GUAMI from the provided 5G-GUTI for finding Source AMF which allocates the 5G-GUTI to the UE. As depicted by  310 , GUAMI (Globally Unique AMF Identifier) contains MCC (Mobile Country Code), MNC (Mobile Network Code) and AMF Identifier. MCC and MNC constitutes a PLMN ID  320  which is usually unique when assigned by PLMN. Therefore, Target AMF can use the unique GUAMI to find Source AMF for retrieving UE context. In case of SNPN, the PLMN ID of the SNPN in 5G-GUTI is unique within an SNPN, but may not be globally unique when assigned by SNPN. As depicted by  310 , since the PLMN ID  320  of SNPN ID (which consists of PLMN ID and NID) may not be globally unique (e.g., the MCC  330  may be 999 assigned by any SNPN), Target AMF may not be able to find Source AMF using the derived GUAMI from 5G-GUTI assigned by SNPN. Mobility Registration Update procedure may fail. Therefore, when UE moves from SNPN to other network, UE provides 5G-GUTI along with NID in Registration Request to Target AMF. Target AMF derives the information of GUAMI from the provided 5G-GUTI using the provided NID for finding Source AMF which allocates the 5G-GUTI to the UE. 
       FIG. 3B  shows one example of NID assignment based on different Assignment modes. As depicted in  FIG. 3B , NID  350  comprises an Assignment mode, a NID PEN, and a NID code. The NID value can be determined based on different Assignment modes as specified in TS 23.003. For example, if Assignment mode is set to 0, then it means the NID is assigned globally unique independent of the PLMN ID of the SNPN. In another example, if Assignment mode is set to 2, then it means the NID is assigned globally unique with the combination of NID and PLMN ID. Note that the NID information here refers to the entire NID value or a partial NID value (e.g., the first digit of the NID value). Providing NID information along with 5G-GUTI can assist the Target AMF to be able to find the Source AMF efficiently, preventing a potential registration procedure failure. The target AMF can use the NID information along with 5G-GUTI to find the source AMF for deriving UE context for the subsequent operations during the mobility registration update procedure. 
       FIG. 4  illustrates a mobility registration update procedure where a UE  401  moves from a source AMF  404  to a target AMF  403 , with enhanced NID provisioning in accordance with one novel aspect. In step  411 , UE  401  performs initial registration in a source network, e.g., an SNPN having a source AMF  404 . A UE needs to register with the network to get authorized to receive services, to enable mobility tracking and to enable reachability. The UE initiates the Registration procedure using one of the following Registration types: Initial Registration to the 5GS; Mobility Registration Update upon changing to a new Tracking Area (TA) outside the UE&#39;s Registration Area, or when UE needs to update its capability or protocol parameters, etc.; Periodic Registration Update (due to a predefined time period of inactivity); or Emergency Registration; or Disaster Registration; or SNPN Onboarding Registration. 
     Upon sending an initial registration request to the source AMF  404 , UE  401  is assigned by the SNPN a 5G-GUTI, which may not be a globally unique number. The source SNPN can be identified by an SNPN ID, which comprises a PLMN ID and an NID. Later on, UE  401  moves to a target network, having a target AMF  403 . The target network can be another SNPN or a PLMN. In step  421 , UE  401  triggers a mobility registration update procedure or other NAS procedure. UE  401  may determine that its 5G-GUTI may not be unique, if it is assigned by the source network that is an SNPN. In response, UE  401  provides the 5G-GUTI together with the NID information of the source network to the target network during the registration procedure or the other NAS procedure using an existing NAS message or a new NAS message. In one example, UE  401  sends a Registration Request to the target AMF  403 . The Registration Request comprises a Registration Type (e.g., Mobility Registration Update); SUCI or 5G-GUTI or PEI; Security parameters; additional GUTI; 4G Tracking Area Update; the indication that the UE is moving from EPS; PLMN with Disaster Condition. If the UE is registered with an SNPN, then the Registration Request further comprises the NID of the SNPN that assigned the 5G-GUTI. 
     In step  422 , the target AMF  403  receives the registration request, derives information of GUAMI from the received 5G-GUTI, and finds the source AMF  404  accordingly. NID information may also be provided in the registration request. If NID is a self-assigned value (i.e. which value is set to 1 as specified in TS 23.003), the value of PLMN ID (of the 5G-GUTI)+NID may not be (globally) unique. Therefore, target AMF  403  may need to request UE  401  to provide UE SUCI/SUPI for the subsequent procedures. If NID is a coordinated assigned value, the value of PLMN ID (of the 5G-GUTI)+NID is (globally) unique. Therefore, target AMF  403  can use the information along with 5G-GUTI to find the correct source AMF. Upon finding the correct source AMF  404 , in step  431 , target AMF  403  sends a request (Namf_Communication_UEContext_Request) message to source AMF  404 , requesting UE context information of UE  401 . In step  432 , source AMF  404  sends a response message (Namf_Communication_UEContext_Response) back to target AMF  403 , providing the UE context information. In step  441 , a MOBILITY REGISTRATION UPDATE procedure is performed between UE  401  and other network entities. In step  442 , target AMF  403  sends a registration accept message to UE  401  to complete the registration update. 
       FIG. 5  is a flow chart of a method supporting enhanced NID provisioning under UE mobility scenarios between different types of networks from UE perspective in accordance with one novel aspect. In step  501 , a UE registers to a stand-alone non-public network (SNPN). The SNPN is identified by a Public Land Mobile Network (PLMN) ID and a Network Identifier (NID). In step  502 , the UE determines that a 5G Global Unique Temporary Identifier (5G-GUTI) is assigned to the UE by the SNPN. In step  503 , the UE triggers a mobility registration update procedure and transmits a registration request to a target access and mobility function (AMF) of a target network. The registration request comprises the 5G-GUTI and NID information of the SNPN. In step  504 , the UE performs the mobility registration update procedure with the target network. 
       FIG. 6  is a flow chart of a method supporting enhanced NID provisioning under UE mobility scenarios between different types of networks from NW perspective in accordance with one novel aspect. In step  601 , a network entity (target AMF) receives a registration request from a User Equipment (UE) in a target network. The registration request triggers a mobility registration update procedure. In step  602 , the target AMF receives a 5G Global Unique Temporary Identifier (5G-GUTI) and Network Identifier (NID) information of a source network. The source network is a stand-alone non-public network (SNPN) identified by a Public Land Mobile Network (PLMN) ID and a NID. In step  603 , the target AMF determines a source AMF using the received 5G-GUTI and the NID information. In step  604 , the target AMF performs the mobility registration update procedure for the UE. The target AMF acquires UE context information from the source AMF. 
     Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.