Patent Publication Number: US-2023156532-A1

Title: Inter access and mobility management function idle mode mobility optimization

Description:
DESCRIPTION OF THE RELATED TECHNOLOGY 
     Fifth-generation (5G) mobile and wireless networks will provide enhanced mobile broadband communications and are intended to deliver a wider range of services and applications as compared to all prior generation mobile and wireless networks. Compared to prior generations of mobile and wireless networks, the 5G architecture is service-based, meaning that wherever suitable, architecture elements are defined as network functions that offer their services to other network functions via common framework interfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the disclosure and are not, therefore, to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG.  1 A  depicts an example schematic representation of a 5G network environment in which network slicing has been implemented in accordance with some aspects of the disclosed technology; 
         FIG.  1 B  illustrates an example 5G network architecture in accordance with some aspects of the present technology; 
         FIG.  2    illustrates an example 5G network architecture including multiple Access and Mobility Management functions (AMF) in accordance with some aspects of the disclosed technology; 
         FIG.  3    illustrates an example method for avoiding user equipment (UE) context transfers by a first gNB connected to a first AMF to a second AMF when the UE in idle mode moves from the first gNB to a second gNB in accordance with some aspects of the disclosed technology; 
         FIG.  4    illustrates an example method for paging in accordance with some aspects of the disclosed technology; 
         FIG.  5    illustrates an example method for handling a service request in accordance with some aspects of the disclosed technology; 
         FIG.  6 A  is the first part of a sequence diagram depicting operations for paging and service request in accordance with some aspects of the disclosed technology; 
         FIG.  6 B  is a second part of the sequence diagram depicting operations for paging and service request in accordance with some aspects of the disclosed technology; 
         FIG.  7    illustrates an example method for handling periodic registration in accordance with some aspects of the disclosed technology; 
         FIG.  8 A  is the first part of a sequence diagram depicting operations for handling periodic registration in accordance with some aspects of the disclosed technology; 
         FIG.  8 B  is a second part of the sequence diagram depicting operations for handling periodic registration in accordance with some aspects of the disclosed technology; 
         FIG.  9 A  is the first part of a sequence diagram depicting operations for UE deregistration in accordance with some aspects of the disclosed technology; 
         FIG.  9 B  is a second part of the sequence diagram depicting operations for UE deregistration in accordance with some aspects of the disclosed technology; and 
         FIG.  10    shows an example of computing system  1000  in accordance with some aspects of the disclosed technology. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. Thus, the following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described to avoid obscuring the description. References to one or an embodiment in the present disclosure can be references to the same embodiment or any embodiment; and, such references mean at least one of the embodiments. 
     Reference to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described, which may be exhibited by some embodiments and not by others. 
     The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Alternative language and synonyms may be used for any one or more of the terms discussed herein, and no special significance should be placed upon whether or not a term is elaborated or discussed herein. In some cases, synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only and is not intended to further limit the scope and meaning of the disclosure or any example term. Likewise, the disclosure is not limited to various embodiments given in this specification. 
     Without intent to limit the scope of the disclosure, examples of instruments, apparatus, methods, and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for the convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, technical and scientific terms used herein have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control. 
     Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained using the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims or can be learned by the practice of the principles set forth herein. 
     Overview 
     In one example, a method is provided for avoiding context transfers by a first AMF connected to a first gNB to a second AMF when a user equipment (UE) in idle mode moves from the first gNB to a second gNB. The method may include provisioning the first AMF and the second AMF with the same tracking area identity (TAI), the first AMF and the second AMF being connected to a respective enterprise gNB. The method may also include configuring the 5G packet core network comprising a session management function (SMF) in communications with the first AMF and the second AMF, to avoid transferring a UE context from the first AMF to the second AMF when the user equipment (UE) in the idle mode moves from a first AMF to the second AMF, whereby the UE context remains with the first AMF. 
     In another example, a system is provided that includes a storage device (e.g., a memory configured to store data, such as virtual content data, one or more images, etc.) and one or more processors (e.g., implemented in circuitry) coupled to the memory and configured to execute instructions. The instructions are effective to cause the processor to provision the first AMF and the second AMF with the same tracking area identity (TAI). The first AMF and the second AMF are connected to a respective enterprise gNB. The instruction are effective to cause the processor to configure the 5G packet core network to avoid transfer of a UE context from the first AMF to the second AMF when the user equipment (UE) in the idle mode moves from a first AMF to the second AMF, whereby the UE context remains with the first AMF. 
     Example Embodiments 
     The disclosed technology addresses a need to optimize user equipment (UE) idle mode mobility handling in packet-core in a private 5G network, which is also referred to as a 5G packet core network. In an Enterprise private 5G network, there can be many mobility events due to reasons, such as small cell size or small footprint of AMF, among others. These mobility events lead to many signaling and processing overheads in the network. 
     In the Enterprise private 5G network with multiple AMFs, a UE in an idle mode normally performs a Mobility Registration procedure when the UE moves across AMFs. As part of the Mobility Registration procedure, the UE context from a previous AMF is transferred to a new AMF to which the UE has moved. However, the transfer of the UE context is unnecessary if the UE stays in the new AMF for a short period of time and the UE does not change to a connected mode from the idle mode. For example, if the UE in an idle mode rapidly moves across many AMFs, the transfer of the UE context can be avoided. 
     The disclosure provides a method that can be more efficient in the idle mode mobility handling in the 5G network. In particular, the disclosure provides a scheme of avoiding the transfer of UE context during idle mode mobility across many AMFs&#39;. The transfer of the UE context doesn&#39;t happen unless required. This scheme results in significant reductions in signaling and processing. 
     Descriptions of network environments and architectures for network data access and services, as illustrated in  FIGS.  1 A and  1 B  are first disclosed herein. A discussion of systems, methods, and computer-readable medium for the inter AMF idle mode mobility optimization, as shown in  FIGS.  2 - 9    will then follow. The discussion then concludes with a brief description of example devices, as illustrated in  FIG.  10   . These variations shall be described herein as the various embodiments are set forth. The disclosure now turns to  FIG.  1 A . 
       FIG.  1 A  depicts an exemplary schematic representation of a 5G network environment in which network slicing has been implemented, and in which one or more aspects of the present disclosure may operate, according to some aspects of the present disclosure. 
     As illustrated, network environment  100  is divided into four domains, each of which will be explained in greater depth below; a User Equipment (UE) domain  110 , e.g. of one or more enterprises, in which a plurality of user cellphones or other connected devices  112  reside; a Radio Access Network (RAN) domain  120 , in which a plurality of radio cells, base stations, towers, or other radio infrastructure  122  resides; a Core Network  130 , in which a plurality of Network Functions (NFs)  132 ,  134 , . . . , n reside; and a Data Network  140 , in which one or more data communication networks such as the Internet  142  reside. Additionally, the Data Network  140  can support SaaS providers configured to provide SaaSs to enterprises, e.g. to users in the UE domain  110 . 
     Core Network  130  contains a plurality of Network Functions (NFs), shown here as NF  132 , NF  134  . . . NF n. In some example embodiments, a core network  130  is a 5G core network (5GC) in accordance with one or more accepted 5GC architectures or designs. In some example embodiments, the core network  130  is an Evolved Packet Core (EPC) network, which combines aspects of the 5GC with existing 4G networks. Regardless of the particular design of core network  130 , the plurality of NFs typically executes in a control plane of the core network  130 , providing a service-based architecture in which a given NF allows any other authorized NFs to access its services. For example, a Session Management Function (SMF) controls session establishment, modification, release, etc., and in the course of doing so, provides other NFs with access to these constituent SMF services. 
     In some example embodiments, the plurality of NFs of the core network  130  can include one or more Access and Mobility Management Functions (AMF), typically used when core network  130  is a 5GC network) and Mobility Management Entities (MME), typically used when core network  130  is an EPC network), collectively referred to herein as an AMF/MME for purposes of simplicity and clarity. In some example embodiments, an AMF/MME can be common to or otherwise shared by multiple slices of the plurality of network slices  152 , and in some example embodiments an AMF/MME can be unique to a single one of the plurality of network slices  152 . 
     Similarly, the remaining NFs of the core network  130  can be shared amongst one or more network slices or provided as a unique instance specific to a single one of the plurality of network slices  152 . In addition to NFs including an AMF/MME as discussed above, the plurality of NFs of the core network  130  can include one or more of the following: User Plane Functions (UPFs); Policy Control Functions (PCFs); Authentication Server Functions (AUSFs); Unified Data Management functions (UDMs); Application Functions (AFs); Network Exposure Functions (NEFs); NF Repository Functions (NRFs); and Network Slice Selection Functions (NSSFs). Various other NFs can be provided without departing from the scope of the present disclosure, as would be appreciated by one of ordinary skill in the art. 
     Across the four domains of the 5G network environment  100 , an overall operator network domain  150  is defined. The operator network domain  150  is in some example embodiments a Public Land Mobile Network (PLMN), a private 5G network and/or a 5G enterprise network, and can be thought of as the carrier or business entity that provides cellular service to the end-users in UE domain  110 . Within the operator network domain  150 , a plurality of network slices  152  are created, defined, or otherwise provisioned to deliver the desired set of defined features and functionalities, e.g. SaaSs, for a certain use case or corresponding to other requirements or specifications. Note that network slicing for the plurality of network slices  152  is implemented in an end-to-end fashion, spanning multiple disparate technical and administrative domains, including management and orchestration planes (not shown). In other words, network slicing is performed from at least the enterprise or subscriber edge at UE domain  110 , through the Radio Access Network (RAN)  120 , through the 5G access edge and the 5G core network  130 , and to the data network  140 . Moreover, note that this network slicing may span multiple different 5G providers. 
     For example, as shown here, the plurality of network slices  152  include Slice 1, which corresponds to smartphone subscribers of the 5G provider who also operates network domain, and Slice 2, which corresponds to smartphone subscribers of a virtual 5G provider leasing capacity from the actual operator of network domain  150 . Also shown is Slice 3, which can be provided for a fleet of connected vehicles, and Slice 4, which can be provided for an IoT goods or container tracking system across a factory network or supply chain. Note that the network slices  152  are provided for purposes of illustration, and in accordance with the present disclosure, and the operator network domain  150  can implement any number of network slices as needed, and can implement these network slices for purposes, use cases, or subsets of users and user equipment in addition to those listed above. Specifically, the operator network domain  150  can implement any number of network slices for provisioning SaaSs from SaaS providers to one or more enterprises. 
     5G mobile and wireless networks will provide enhanced mobile broadband communications and are intended to deliver a wider range of services and applications as compared to all prior generation mobile and wireless networks. Compared to prior generations of mobile and wireless networks, the 5G architecture is service-based, meaning that wherever suitable, architecture elements are defined as network functions that offer their services to other network functions via common framework interfaces. To support this wide range of services and network functions across an ever-growing base of user equipment (UE), 5G networks incorporate the network slicing concept utilized in previous generation architectures. 
     Within the scope of the 5G mobile and wireless network architecture, a network slice comprises a set of defined features and functionalities that together form a complete Public Land Mobile Network (PLMN), a private 5G network and/or a 5G enterprise network for providing services to UEs. This network slicing permits for the controlled composition of the 5G network with the specific network functions and provided services that are required for a specific usage scenario. In other words, network slicing enables a 5G network operator to deploy multiple, independent 5G networks where each is customized by instantiating only those features, capabilities, and services required to satisfy a given subset of the UEs or a related business customer needs. 
     In particular, network slicing is expected to play a critical role in 5G networks because of the multitude of use cases and new services 5G is capable of supporting. Network service provisioning through network slices is typically initiated when an enterprise requests network slices when registering with AMF/MME for a 5G network. At the time of registration, the enterprise will typically ask the AMF/MME for characteristics of network slices, such as slice bandwidth, slice latency, processing power, and slice resiliency associated with the network slices. These network slice characteristics can be used in ensuring that assigned network slices are capable of actually provisioning specific services, e.g. based on requirements of the services, to the enterprise. 
     Associating SaaSs and SaaS providers with network slices used to provide the SaaSs to enterprises can facilitate efficient management of SaaS provisioning to the enterprises. Specifically, it is desirable for an enterprise/subscriber to associate already procured SaaSs and SaaS providers with network slices being used to provision the SaaSs to the enterprise. However, associating SaaSs and SaaS providers with network slices is extremely difficult to achieve without federation across enterprises, network service providers, e.g. 5G service providers, and SaaS providers. 
       FIG.  1 B  illustrates an example 5G network architecture. As addressed above, a User Equipment (UE)  112  can connect to a radio access network provided by a first gNodeB (gNB)  127 A or a second gNB  127 B. 
     The gNB  127 A can communicate over a control plane N2 interface with an access mobility function (AMF)  135 . AMF  135  can handle tasks related to network access through communication with unified data management (UDM) function  138  which accesses a user data repository (URD)  136  that can contain user data such as profile information, authentication information, etc. Collectively AMF  135  and UDM  138  can determine whether a UE should have access and any parameters on access. AMF  135  also works with SEAF  133  to handle authentication and re-authentication of the UE  112  as it moves between access networks. The SEAF and the AMF could be separated or co-located. 
     Assuming AMF  135  determines the UE  112  should have access to a user plane to provide voice or data communications, AMF  135  can select one or more service management functions (SMF)  137 . SMF  137  can configure and control one or more user plane functions (UPF)  139 . Control plane communications between the SMF  137  and the gNB  127 A (or  127 B) also need to be encrypted. SEAF  133  can provide a security key to SMF  137  for use in encrypting control plane communications between the SMF  137  and the gNB  127 A (or  127 B). 
     As noted above SMF  137  can configure and control one or more user plane functions (UPF)  139 . SMF  137  communicates with UPF  139  over an N4 Interface which is a bridge between the control plane and the user plane. SMF  137  can send PDU session management and traffic steering and policy rules to UPF  139  over the N4 interface. UPF  139  can send PDU usage and event reporting to SMF  137  over the N4 interface. 
     UPF  139  can communicate user plane data or voice over the N3 interface back to UE  112  through gNB  127 A. There can be any number of UPFs handling different user plane services. Most commonly there would be at least one UPF for data service and at least one UPF for voice service. 
     By implementing UPF at each gNB, many UPF instances are in a single deployment, which complicates the UE IP address management and user plane data forwarding. Typically, a UE IP address pool is maintained by SMF, which allocates an IP address to a UE during UE Registration/PDU (Protocol Data Unit) session establishment process. SMF then configures UPF with traffic classification rules and traffic policies for the IP address. UPF acts as a router for the subnet allocated to the UE. IGP/BGP protocols can be used to publish these routes into the network. When the traffic for the UE is received from the network, the traffic is classified and the IP payload alone is forwarded to the gNB where the UE is connected over a GTPu tunnel. Similarly, when data are received in an uplink over the GTPu tunnel, UPF appends a MAC header and routes the data to the next hop. In the context of local UPF collocated at a gNB, maintaining one UE IP address pool per gNB will not be scalable and manageable as multiple gNBs exist in a facility. Routing/Packet forwarding would have similar implications. 
       FIG.  2    illustrates an example 5G network architecture including multiple AMFs in accordance with some aspects of the disclosed technology. As shown, a 5G core network  200  includes multiple AMFs  135 A-D with an N14 interface  202  between the AMFs. For example, the N14 interface is between AMF 1  and peer AMFs, e.g., AMF 2 , AMF 3 , AMF 4 , among others. The multiple AMFs are in communication with the same SMF  137 . The multiple AMFs  135 A-D are connected to respective gNBs  127 A-D. 
     The gNBs  127 A-D connected to the AMFs  135 A-D participating in the idle mode mobility optimization can be configured with the same TAI. The same TAI configuration ensures that when the UE  112  moves from one gNB to another gNB connected to a different AMF, the UE does not perform a Mobility Registration procedure, which includes the transfer of the UE context from one AMF to another AMF. Typically, when a UE moves to a new TAI, it will perform a mobility registration which requires a context transfer to the AMF associated with the gNB. However, in the present technology, gNB 1  is connected to AMF 1  and gNB 2  is connected to AMF 2 , and both gNB 1  and gNB 2  are configured with the same TAI so the UE will not need to perform mobility registration since it will not have moved to a new TAI, although it will have moved from gNB 1  to gNB 2 . When the UE moves from gNB 1  to gNB 2  in an idle mode, there is no change detected in any TAI. Thus, the UE does not perform the Mobility Registration procedure. 
       FIG.  3    illustrates an example method  300  for avoiding UE context transfers when a user equipment (UE) in idle mode moves from the first gNB to a second gNB. Although example method  300  depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence that does not materially affect the function of method  300 . In other examples, different components of an example device or system that implements the method  300  may perform functions at substantially the same time or in a specific sequence. 
     According to some examples, method  300  includes provisioning the first AMF and the second AMF with the same tracking area identity (TAI), where the first AMF and the second AMF are connected to a respective enterprise gNB at block  310 . 
     Since the first AMF and the second AMF are assigned to the same tracking area identity (TAI), the UE does not perform a Mobility Registration Procedure when the UE in idle mode moves from AMF 1  to AMF 2  or vice versa. Since the Mobility Registration does not occur, there is no transfer of the UE context from AMF 1  to AMF 2 . Even though the UE is in connected to gNB 2 , which is which is associated with AMF 2 , the UE is still anchored at AMF 1 . Subsequently, if the UE moves back from gNB 2  to gNB 1 , there is no Mobility Registration, and there is no transfer of the UE context. Reducing these unnecessary context transfers improves the efficiency of the network. 
     According to some examples, method  300  includes configuring the 5 G packet core network to avoid transferring a UE context from the first AMF to the second AMF when the user equipment (UE) in the idle mode moves from a first AMF to the second AMF, whereby the UE context remains with the first AMF at block  320 . 
     The transfer of the UE context may happen when the UE connects to the network, e.g. when the UE exits an Idle Mode, when the UE sends a Service Request to the network due to UL data/signaling, or after receiving paging from the network. A particular AMF may use the TAI to AMF mapping to request peer-AMF nodes to send paging to their respective gNBs or RANs in the TAI. The TAI to AMF mapping may be configured locally on each AMF. The TAI to AMF mapping may also be discovered through AMF discovery using TAI. 
     When the network pages the UE, the paging goes to all gNBs serving the last registered TAI of the UE. These gNBs are connected to different AMFs, as illustrated in  FIG.  2   . The AMF uses the TAI to AMF mapping to determine the set of AMFs to which to send a paging request. 
       FIG.  4    illustrates an example method  400  for paging in accordance with some aspects of the disclosed technology. Although example method  400  depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence that does not materially affect the function of method  400 . In other examples, different components of an example device or system that implements the method  400  may perform functions at substantially the same time or in a specific sequence. 
     Method  400  illustrated in  FIG.  4    will also be discussed in the contexts of  FIGS.  6 A and  6 B , which illustrate a sequence diagram for paging and service requests. Some steps specific to the present technology illustrated in method  400  are also present in  FIGS.  6 A and  6 B . 
     As illustrated in  FIG.  6 A , UE is registered on AMF 1  and has established a Protocol Data Unit (PDU) session, and the UE is in an idle mode at  402 . The UE moves and connects to gNB 2  where the UE remains in an Idle mode and does not initiate a Mobility Registration since the UE does not detect a TAI change at  404 . 
     At  406 , the UE context does not transfer from AMF 1  to AMF 2  until needed, which will occur if the UE emerges from an Idle mode and makes a registration request. At  408 , SMF  137  receives downlink (DL) data for the UE. N1N2 If a network function (NF) intends to communicate with the UE, the NF sends a request to AMF 1 , e.g. on receiving DL data indication from UPF, and SMF  137  sends N1N2 Message Transfer to AMF 1  at  410 . According to some examples, method  400  includes receiving a paging request for the UE from a network function (NF) at block  410 . For example, AMF 1  as illustrated in  FIG.  2    may receive a request for the UE from a network function, where AMF 1  is associated with gNB 1  to which the UE was previously connected. AMF 1  receives a request for UE from some other network function. For example, SMF may send N1N2MessageTransfer signaling message to AMF 1  when SMF receives Downlink data notification from UPF. AMF 1  decides whether to send a Paging request to the UE, because the UE is in idle mode. 
     As illustrated in  FIG.  6 A , AMF 1  sends a paging message to gNB 1  at  420 . According to some examples, method  400  includes sending the paging request to gNB 1  connected to the AMF 1  at block  420 . As illustrated in  FIG.  6 A , AMF 1  sends paging requests to all other AMFs in an AMF neighboring list at  422 . The other AMFs are serving the same TAI. 
     According to some examples, method  400  includes determining at least one additional AMF mapped to the same TAI at block  430 . For example, AMF 1 , as illustrated in  FIG.  2   , may determine at least one additional AMF mapped to the same TAI. The additional AMF includes the AMF 2  which is associated with the gNB 2  to which the UE has moved. 
     As illustrated in  FIG.  6 B , AMF 2  receives a paging request from AMF 1  at  440 . According to some examples, method  400  includes sending the paging request to the at least one additional AMF, whereby the paging request is passed to gNB 2  and reaches the UE at block  440 . For example, AMF 1  as illustrated in  FIG.  2    may send the paging request to the at least one additional AMF, e.g. AMF 2 , whereby the paging request is passed to the second gNB and reaches the UE. 
     As illustrated in  FIG.  6 B , AMF 2  sends paging to gNB 2  at  442 . The N14 interface is enhanced to support messages for this purpose. The UE receives the paging from gNB 2  and sends a Paging Response by setting up a Radio Resource Control (RRC) correction with gNB 2  at  444 . 
     When a Service Request is received by a peer AMF (e.g. AMF 2 ) where the UE′ is not anchored, the peer AMF transfers the UE context from the AMF (AMF 1 ) where the UE is anchored to AMF 2 . 
       FIG.  5    illustrates an example method  500  for handling service requests in accordance with some aspects of the disclosed technology. Although example method  500  depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence that does not materially affect the function of method  500 . In other examples, different components of an example device or system that implements the method  500  may perform functions at substantially the same time or in a specific sequence. 
     Method  500  illustrated in  FIG.  5    will also be discussed in the context of  FIGS.  6 A and  6 B , which illustrates a sequence diagram for paging and service request. Some steps specific to the present technology illustrated in method  500  are also present in  FIGS.  6 A and  6 B . 
     As illustrated in  FIG.  6 B , the Service Request from the UE is received by AMF 2  which ‘does not have the UE context at  510 . Since the UE is attached to gNB 2 , the UE receives paging from gNB 2  and responds to the paging by sending the Service Request to AMF 2  at  510 . According to some examples, method  500  includes receiving a service request by the second AMF from the UE connected to the second gNB at block  510 . 
     As illustrated in  FIG.  6 B , AMF 2  uses 5G-TMSI to determine that the UE context is registered with AMF 1  at  520 . TMSI stands for Temporary Mobile Subscriber Identity, and is part of the 5G-GUTI, which is typically assigned to the UE during Initial Registration by AMF 1 . According to some examples, method  500  includes determining that the UE context is present at the first AMF at block  520 . If the UE context is present at the first AMF, the UE is registered with the first AMF or AMF 1 . 
     As illustrated in  FIG.  6 B , AMF 2  performs a 3GPP procedure “UEContextTransfer” to retrieve the UE context from AMF 1  and complete the UE registration on AMF 2  at  530 . Once the UE is registered on AMF 2 , the Service Request can be processed regularly. According to some examples, method  500  includes performing a UE Context Transfer by retrieving the UE context for the UE from the first AMF at block  530 . For example, AMF 2  illustrated in  FIG.  2    may perform a UE Context Transfer by retrieving the UE context for the UE from the first AMF. 
     As illustrated in  FIG.  6 B , AMF 2  completes the transfer of the UE context at  532 , processes a service request message at  534 , then sends a Service Accept message to the UE at  536 . 
     There is no need to transfer the UE context if UE is performing a periodic registration.  FIG.  7    illustrates an example method  700  for periodic registration in accordance with some aspects of the disclosed technology. Although example method  700  depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence that does not materially affect the function of method  700 . In other examples, different components of an example device or system that implements the method  700  may perform functions at substantially the same time or in a specific sequence. 
     Method  700  illustrated in  FIG.  7    will also be discussed in the contexts of  FIGS.  8 A and  8 B , which illustrate a sequence diagram for paging and service requests. Some steps specific to the present technology illustrated in method  700  are present in  FIG.  7   . 
     As illustrated in  FIG.  8 A , operations  402 ,  404 , and  406  are described above with respect to  FIG.  6 A . A periodic registration timer expires at  708 . The UE sends a periodic registration request to AMF 2  by setting up an RRC connection with gNB 2  at  710 . According to some examples, method  700  includes receiving a periodic registration request from the UE connected to the second gNB at block  710 . For example, AMF 2  illustrated in  FIG.  2    may receive a periodic registration request from the UE connected to the second gNB. 
     As illustrated in  FIG.  8 B , AMF 2  uses 5G Global Unique Temporary Identifier (5G-GUTI) to determine that the UE is registered with AMF 1  at  720 . The Registration Request message carries 5G-GUTI. TMSI is a part of 5G-GUTI. In the disclosure, 5G-GUTI is used interchangeably with TMSI. According to some examples, method  700  includes determining that the UE context is present at the first AMF at block  720 . For example, AMF 2  illustrated in  FIG.  2    may determine that the UE context is present at the first AMF (AMF 1 ). If the UE context is present at the first AMF, the UE is registered with the first AMF or AMF 1 . 
     As illustrated in  FIG.  8 B , AMF 2  forwards a Periodic Registration Request message (e.g. N1N2 Message Relay) to AMF 1  over an N14 interface at  730 . The N14 interface is enhanced to support this communication. According to some examples, method  700  includes forwarding the periodic registration request to the first AMF by the second AMF at block  730 . At  732 , AMF 1  processes the Periodic Registration Request and sends a Registration Accept response to the UE via AMF 2 . 
     At  740 , AMF 1  sends a Registration Request (e.g. N1N2 Message Transfer) to AMF 2 . According to some examples, method  700  includes receiving a registration Accept message from the first AMF (AMF 1 ) by the second AMF (AMF 2 ) at block  740 . 
     As illustrated in  FIG.  8 B , AMF 2  sends a Registration Accept to the UE at  750 . According to some examples, method  700  includes sending the registration accept message by the second AMF to the UE connected to the second gNB, whereby the UE context is not transferred when the UE sends the periodic registration request at block  750 . 
     Unified data management (UDM) initiates UE deregistration, e.g. due to subscription being withdrawn.  FIG.  9 A  is the first part of a sequence diagram depicting operations for UE deregistration in accordance with some aspects of the disclosed technology.  FIG.  9 B  is a second part of the sequence diagram depicting operations for UE deregistration in accordance with some aspects of the disclosed technology. 
     At  908 , UDM decides to remove the UE context. At  910 , UDM sends Deregistration Request to AMF 1 . Then, AMF 1  performs a paging procedure, including operations  420 - 444 , as described above in  FIGS.  6 A and  6 B . 
     The UE responds with a Service Request to AMF 2  at  510 . If the UE is in an AMF 2  area, AMF 2  receives a Service Request from the UE and sends a UE Context Transfer request to AMF 1  at  530 . 
     Since the UE is de-registered from the AMF 1 , AMF 1  sends a failure response ““403 Forbidden”” and provides a cause code ““UE DEREGISTERED”” at  920 . The cause code is added to the N14 interface. 
     At  536 , AMF 2  sends a Service Accept message to the UE. At  922 , AMF 1  sends a NAS message Deregistration Request (e.g. N1N2 Message Transfer) to AMF 2 . The Deregistration Request is transferred to the UE. At  924 , AMF 2  sends a Deregistration Request to the UE. At  926 , the UE responds with Deregistration Accept. Then, AMF 2  relays the Deregistration Request to AMF 1 . 
     In some aspects, configuring the 5G packet core network may include enhancing an N14 interface to support paging by the first AMF to the second AMF. To request other AMF nodes serving the same TAI to send paging to their RANs. The first AMF uses an N1N2 Message Transfer service to send paging to the second AMF (e.g. a peer AMF). The peer AMF or the second AMF sends paging to the gNB serving the same TAI. 
     The 5G packet core network may be configured by enhancing the N14 interface to relay a NAS message by the second AMF to the first AMF. To relay certain NAS messages (e.g. N1N2 Message Transfer) from one AMF to another AMF requires defining an additional service on the N14 interface. 
     The configuring the 5G packet core network may further include enhancing the N14 interface to trigger a UE Context transfer procedure by the second AMF (e.g. peer AMF 2 ) after receiving a service request from the UE. 
     The configuring the 5G packet core network may further include enhancing an N14 interface to include ““5G-TM5I”” as ““UEContextID”” in N14 messages for UE identification and define a UE Deregistered cause code. 
       FIG.  10    shows an example of computing system  1000 , which can be for example any computing device making up any of the entities illustrated in  FIG.  2   , for example, gNBs  127 A-D, or any component thereof in which the components of the system are in communication with each other using connection  1005 . Connection  1005  can be a physical connection via a bus, or a direct connection into processor  1010 , such as in a chipset architecture. Connection  1005  can also be a virtual, networked connection, or logical connection. 
     In some embodiments, computing system  1000  is a distributed system in which the functions described in this disclosure can be distributed within a data center, multiple data centers, a peer network, etc. In some embodiments, one or more of the described system components represents many such components each performing some or all of the function for which the component is described. In some embodiments, the components can be physical or virtual devices. 
     Example system  1000  includes at least one processing unit (CPU or processor)  1010  and connection  1005  that couples various system components including system memory  1015 , such as read-only memory (ROM)  1020  and random access memory (RAM)  1025  to processor  1010 . Computing system  1000  can include a cache of high-speed memory  1012  connected directly with, close to, or integrated as part of processor  1010 . 
     Processor  1010  can include any general-purpose processor and a hardware service or software service, such as services  1032 ,  1034 , and  1036  stored in storage device  1030 , configured to control processor  1010  as well as a special-purpose processor where software instructions are incorporated into the actual processor design. Processor  1010  may essentially be a completely self-contained computing system, containing multiple cores or processors, a bus, memory controller, cache, etc. A multi-core processor may be symmetric or asymmetric. 
     To enable user interaction, computing system  1000  includes an input device  1045 , which can represent any number of input mechanisms, such as a microphone for speech, a touch-sensitive screen for gesture or graphical input, keyboard, mouse, motion input, speech, etc. Computing system  1000  can also include output device  1035 , which can be one or more of many output mechanisms known to those of skill in the art. In some instances, multimodal systems can enable a user to provide multiple types of input/output to communicate with computing system  1000 . Computing system  1000  can include communications interface  740 , which can generally govern and manage the user input and system output. There is no restriction on operating on any particular hardware arrangement, and therefore the basic features here may easily be substituted for improved hardware or firmware arrangements as they are developed. 
     Storage device  1030  can be a non-volatile memory device and can be a hard disk or other types of computer-readable media which can store data that are accessible by a computer, such as magnetic cassettes, flash memory cards, solid-state memory devices, digital versatile disks, cartridges, random access memories (RAMs), read-only memory (ROM), and/or some combination of these devices. 
     The storage device  1030  can include software services, servers, services, etc., that when the code that defines such software is executed by the processor  1010 , it causes the system to perform a function. In some embodiments, a hardware service that performs a particular function can include the software component stored in a computer-readable medium in connection with the necessary hardware components, such as processor  1010 , connection  1005 , output device  1035 , etc., to carry out the function. 
     For clarity of explanation, in some instances, the present technology may be presented as including individual functional blocks including functional blocks comprising devices, device components, steps or routines in a method embodied in software, or combinations of hardware and software. 
     Any of the steps, operations, functions, or processes described herein may be performed or implemented by a combination of hardware and software services or services, alone or in combination with other devices. In some embodiments, a service can be software that resides in the memory of a client device and/or one or more servers of a content management system and perform one or more functions when a processor executes the software associated with the service. In some embodiments, a service is a program or a collection of programs that carry out a specific function. In some embodiments, a service can be considered a server. The memory can be a non-transitory computer-readable medium. 
     In some embodiments, the computer-readable storage devices, mediums, and memories can include a cable or wireless signal containing a bitstream and the like. However, when mentioned, non-transitory computer-readable storage media expressly exclude media such as energy, carrier signals, electromagnetic waves, and signals per se. 
     Methods according to the above-described examples can be implemented using computer-executable instructions that are stored or otherwise available from computer-readable media. Such instructions can comprise, for example, instructions and data which cause or otherwise configure a general-purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. Portions of computer resources used can be accessible over a network. The executable computer instructions may be, for example, binaries, intermediate format instructions such as assembly language, firmware, or source code. Examples of computer-readable media that may be used to store instructions, information used, and/or information created during methods according to described examples include magnetic or optical disks, solid-state memory devices, flash memory, USB devices provided with non-volatile memory, networked storage devices, and so on. 
     Devices implementing methods according to these disclosures can comprise hardware, firmware and/or software, and can take any of a variety of form factors. Typical examples of such form factors include servers, laptops, smartphones, small form factor personal computers, personal digital assistants, and so on. The functionality described herein also can be embodied in peripherals or add-in cards. Such functionality can also be implemented on a circuit board among different chips or different processes executing in a single device, by way of further example. 
     The instructions, media for conveying such instructions, computing resources for executing them, and other structures for supporting such computing resources are means for providing the functions described in these disclosures. 
     Although a variety of examples and other information was used to explain aspects within the scope of the appended claims, no limitation of the claims should be implied based on particular features or arrangements in such examples, as one of ordinary skill would be able to use these examples to derive a wide variety of implementations. Further and although some subject matter may have been described in language specific to examples of structural features and/or method steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to these described features or acts. For example, such functionality can be distributed differently or performed in components other than those identified herein. Rather, the described features and steps are disclosed as examples of components of systems and methods within the scope of the appended claims.