Control plane (c-plane) signaling reduction for network operators with a network sharing agreement

Abstract

A method includes receiving, by a first core network entity of a first core network, from a user equipment (UE), a registration request, where the first core network is a core network of a first operator; assigning, by the first core network entity, a long-term UE context to the UE, the long-term UE context configured to be maintained by a second core network and configured to allow the UE to switch from communicating with the first core network to communicating with the second core network without re-registering with the second core network, where the second core network is a core network of a second operator different than the first operator; and transmitting, to the UE in response to the registration request, a registration response including the long-term UE context assigned to the UE.

Description

CONTROL PLANE (C-PLANE) SIGNALING REDUCTION FOR NETWORK OPERATORS WITH A NETWORK SHARING AGREEMENTRELATED APPLICATIONS

[0001] This patent application claims the benefit of priority of United States Provisional Patent Application No.63 / 586,596 filed September 29, 2023, which is hereby incorporated by reference as if reproduced in its entirety.FIELD

[0002] Various example embodiments relate generally to wireless networks and, more particularly, to control plane (C -plane) signaling reduction for network operators with a network sharing agreement.BACKGROUND

[0003] Wireless networking provides significant advantages for user mobility. A user’s ability to remain connected to a wireless network while on the move provides advantages not only for the user, but also provides greater efficiency and productivity for society as a whole. As user and / or operator expectations for, e.g., network sharing, network energy cost, and device battery life, become more demanding, technology for wireless networking must also keep pace with such expectations. Accordingly, there is continuing interest in improving wireless networking technology.SUMMARY

[0004] As used herein, the term “entity” may refer to a distinct component of an architecture or device, a network device, a network node, a network function, or any other devices (physical or virtual) in a communication network.

[0005] In accordance with aspects of the present disclosure, a method includes receiving, by a first core network entity of a first core network, from a user equipment (UE), a registration request, where the first core network is a core network of a first operator; assigning, by the first core network entity, a long-term UE context to the UE, the long-term UE context configured to be maintained by a second core network and configured to allow the UE to switch from communicating with the first core network to communicating with the second core network without re-registering with the second core network, where the second core network is a core network of a second operator different than the first operator; and transmitting, to the UE inresponse to the registration request, a registration response including the long-term UE context assigned to the UE.

[0006] In an aspect of the method, the method further includes determining whether to provide the long-term UE context for the UE based on at least one of the following a mobility pattern of the UE, a quality of service (QoS) of the UE, an energy source of the UE, a geographical location of the UE, or a maximum number of long-term UE contexts for UEs based on a network sharing agreement between the first operator and the second operator.

[0007] In an aspect of the method, the method further includes selecting, by the first core network entity, an identifier for the long-term UE context from a pool of long-term UE context identifiers, where the pool of long-term UE context identifiers is provided based on a network sharing agreement between the first operator and the second operator.

[0008] In an aspect of the method, the long-term UE context assigned to the UE includes at least one of the following an identifier of the long-term UE context, registration update timer information, information associated with a bearer configured for the UE, information associated with a service configured for the UE, information associated with a registration area of the UE, information associated with a reachability configuration of the UE, or information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

[0009] In an aspect of the method, the first core network is part of a home network of the UE, and the second core network is part of a roaming network of the UE.

[0010] In an aspect of the method, the method further includes offloading, by the first core network entity, communications for the UE to the second core network.

[0011] In an aspect of the method, the method further includes transitioning, by the first core network entity, to an energy efficiency state.

[0012] In an aspect of the method, the method further includes receiving, by the first core network entity from the UE, an indication of a revocation of the long-term UE context by the second core network; and deleting, by the first core network entity in response to receipt of the indication of the revocation of the long-term UE context, the long-term UE context for UE.

[0013] In an aspect of the method, the method further includes assigning, by the first core network entity, a second long-term UE context to the UE, the second long-term UE context configured to be maintained by the first core network entity and configured to allow the UE to switch communication from the second core network to the first core network without reregistering with the first core network.

[0014] In an aspect of the method, the method further includes maintaining a registration update timer associated with the second long-term UE context.

[0015] In accordance with aspects of the present disclosure, a method includes receiving, by a first core network entity of a first core network, from a user equipment (UE), a long-term registration request including a long-term UE context of the UE, where the first core network is a core network of a first operator; and transmitting, by the first core network entity, to the UE in response to the long-term registration request, registration update timer information configured to be maintained by the UE and configured to allow the UE to switch from communicating with a second core network to communicating with the first core network without re-registering with the first core network, where the second core network is a core network of a second operator different than the first operator.

[0016] In an aspect of the method, the first core network is part of a roaming network of the UE, and where the second core network is part of a home network of the UE.

[0017] In an aspect of the method, at least one of the long-term UE context of the UE or the registration update timer information is provisioned based on a network sharing agreement between the first operator and the second operator.

[0018] In an aspect of the method, the long-term UE context includes at least one of the following an identifier of the long-term UE context, information associated with a bearer configured for the UE, information associated with a service configured for the UE. information associated with a registration area of the UE, information associated with a reachability configuration of the UE, information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

[0019] In an aspect of the method, the method further includes authenticating the identifier of the long-term UE context.

[0020] In an aspect of the method, the method further includes maintaining, at the first core network, the long-term UE context of the UE; and using the maintained long-term UE context for the UE when the UE switches from the second core network to the first core network.

[0021] In an aspect of the method, the method further includes revoking, by the first core network entity, the long-term UE context of the UE based on at least one of a mobility pattern of the UE or a network sharing agreement between the first operator and the second operator.

[0022] In an aspect of the method, the method further includes transmitting, by the first core network entity, to the UE, an indication that the long-term UE context of the UE is revoked.

[0023] In accordance with aspects of the present disclosure, a method includes receiving, by a user equipment (UE), a long-term UE context assigned to the UE in association with a first core network, the long-term UE context configured to enable the UE to switch from communicating with a second core network of a second operator to communicating with the first core network without re-registering with the first core network, where the first core network is a core network of a first operator, and where the second core network is a core network of a second operator different than the first operator; and switching, by the UE, communication with the second core network to communication with the first core network, where the communication with the first core network is based on the long-term UE context.

[0024] In an aspect of the method, one of the first core network or the second core network is part of a home network of the UE, and where the other one of the first core network or the second core network is part of a roaming network of the UE.

[0025] In an aspect of the method, the method further includes maintaining, by the UE, the long-term UE context associated with the first core network while the UE is in communication with the second core network.

[0026] In an aspect of the method, the long-term UE context includes at least one of the following an identifier of the long-term UE context, registration update timer information, information associated with a bearer configured for the UE, information associated with a service configured for the UE. information associated with a registration area of the UE, information associated with a reachability configuration of the UE, information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

[0027] In an aspect of the method, the method further includes transmitting, by the UE to the second core network, a registration request to register with the second core network, where the receiving the long-term UE context includes receiving, from the second core network in response to the registration request, a registration response including the long-term UE context.

[0028] In an aspect of the method, the method further includes transmitting, by the UE, to the first core network, a long-term registration request including the long-term UE context, and receiving, by the UE from the first core network in response to the long-term registration request, information associated with a registration update timer.

[0029] In an aspect of the method, the method further includes camping, by the UE on the first core network without a re-registration with the first core network based on the long-term UE context and based on the registration update timer associated with the first core network being in progress.

[0030] In an aspect of the method, the method further includes transmitting, by the UE to the first core network, a registration request to register with the first core network, where the receiving the long-term UE context includes receiving, by the UE from the first core network in response to the registration request, a registration response including the long-term UE context.

[0031] In an aspect of the method, the method further includes receiving, by the UE from the first core network, an indication that the long-term UE context associated with the first core network has been revoked; and releasing, by the UE in response to the indication that the longterm UE context associated with the first core network has been revoked, the long-term UE context.

[0032] In an aspect of the method, the method further includes transmitting, by the UE to the second core network, a notification to inform the second core network that the long-term UE context associated with the first core network has been revoked.

[0033] In an aspect of the method, the switching to the communication with the first core network is in response to an energy efficiency state transition associated with the second core network.

[0034] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Some example embodiments will now be described with reference to the accompanying drawings.

[0036] FIGS. 1A-1D are diagrams of example embodiments of various configurations of wireless communication systems, according to one illustrated aspect of the disclosure;

[0037] FIG. 2 is a diagram of an example wireless communication system, according to one illustrated aspect of the disclosure;

[0038] FIG. 3 is a diagram of example signals and operations of a network system that provisions for network sharing, according to one illustrated aspect of the present disclosure;

[0039] FIGS. 4A and 4B are diagrams showing control plane signaling (e.g., messages) sent between a UE, a home network, and a roaming network, and operations performed by the user equipment, the home network, and the roaming network, according to one illustrated aspect of the present disclosure;

[0040] FIG. 5 is a flow diagram of example operations of a UE of a subscriber of a network roaming between the network and another network, according to one illustrated aspect of the present disclosure;

[0041] FIG. 6 is a flow diagram of example operations of a UE migrating between networks, according to one illustrated aspect of the present disclosure;

[0042] FIG. 7 is a flow diagram of example operations of a network apparatus providing a long-term UE context to a UE, according to one illustrated aspect of the present disclosure;

[0043] FIG. 8 is a flow diagram of example operations of a network apparatus performing a long-term registration with a UE, according to one illustrated aspect of the present disclosure;

[0044] FIG. 9 is a flow diagram of example operations of a UE migrating between networks, according to one illustrated aspect of the present disclosure; and

[0045] FIG. 10 is a diagram of example embodiment of components of a UE or of a network apparatus, according to one illustrated aspect of the present disclosure.DETAILED DESCRIPTION

[0046] In the following description, certain specific details are set forth in order to provide a thorough understanding of disclosed aspects. However, one skilled in the relevant art will recognize that aspects may be practiced without one or more of these specific details or with other methods, components, materials, etc. In other instances, well-known structures associated with transmitters, receivers, or transceivers have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the aspects.

[0047] Reference throughout this specification to “one aspect” or “an aspect” means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. Thus, the appearances of the phrases “in one aspect” or “in an aspect” in various places throughout this specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more aspects.

[0048] The present disclosure generally relates to wireless networks implementing, such as, without limitation, Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE- Advanced, enhanced LTE (eLTE), 5G New Radio (5G NR), 5G Advance, 6G (and beyond) technologies. The term ‘eLTE’ here denotesthe LTE evolution that connects an LTE radio access network to a 5G core network. LTE is also known as evolved UMTS.

[0049] Network sharing can enable operators to maximize rollout and improve overall network quality. There are various types of network sharing frameworks and / or configurations. Two network sharing frameworks that are commonly deployed in industry are multi-operator radio access network (MORAN) and multi-operator core network (MOCN). In a MORAN framework, a radio access network (RAN) is deployed where all radio elements (e.g., antenna(s), base station(s), tower(s), site(s), and power) of the RAN shared by two or more operators, however, the radio carriers of the RAN not shared by the two or more operators. On the other hand, in a MOCN framework, two or more core networks operating separately (or independently) sharing a common core network infrastructure may share the same RAN, including the radio carriers. The MOCN framework may be efficient for network sharing as it may allow mobile operators to pool (share) their respective spectrum allocations, resulting in improved trunking efficiency.

[0050] With the expansion of deployments of wireless networks implementing 5G technology (e.g., 5G wireless networks), more network sharing scenarios can arise, for example, depending on operators’ strategies, commercial agreements among operators, and specific rules and / or legislations in certain countries. One of the challenges for operators participating in network sharing (e.g., operators which share a network) is the maintenance of interconnections (e.g., number of network interfaces) between a shared RAN (e.g., a next generation-radio access network (NG-RAN)) and respective participating operators’ core networks (e.g., the core network of each respective operator participating in network sharing), especially when there is a large number of base stations shared among the participating operators. Therefore, it may be desirable to consider other network sharing scenarios where a RAN can be shared among multiple operators without requiring each of the multiple operator’s core network to have a direct connection to the shared RAN.

[0051] Network sharing can benefit various network deployment scenarios. In one example, network sharing can enable industry to meet sustainability targets (e.g., to reduce network power consumption). For instance, when multiple operators have overlapping coverage areas, one or more of the operators can shut down part(s) of their networks in certain area(s) during certain times of the day when the amount of data traffic in the networks of the one or more operators may be low. The users of the networks of operator(s) who shut down parts of their network may be served by the remaining active network(s). In this way, anoperator may reduce the number of actively transmitting base stations during low-traffic periods, thus reducing network power consumption.

[0052] As an example, an operator may desire to switch off (or power down) part of its network during a time period with low traffic and may request its subscribers (e.g., UEs of subscribers) to use a network of another operator. To facilitate the offloading of UEs of subscribers to other network(s), the operator and the other operator(s)) may have a network sharing agreement, for example, specifying the time and / or the durations during which the offloading of UEs may occur. During the agreed sharing periods, the operator of the home network of the subscriber (e.g., home public land mobile network (HPLMN)) may then shut down its base station(s) and / or other network resources, and the UEs of the subscribers of the home network may roam to one of those other networks(s) of other operators that have entered into a network sharing agreement. When roaming, a UE may register with a roaming network (e.g., a network of another operator). The UE of a subscriber may switch back (return) to its HPLMN (e.g., at the end of a network sharing period), where the switching back (returning) to the HPLMN may include re-registering with the HPLMN. In general, when a UE switches from one network to another network (e.g., a new network), the UE has to perform a registration procedure with the newly switched network, or more specifically, with a core network of the newly switched network.

[0053] As used herein, the term “home network” may refer to a network (e.g., a UE’s HPLMN) to which a subscriber of a UE has a subscription. For instance, the UE may have a subscriber identity module (SIM) configured according to the subscription. As used herein, the term “home core network” may refer to a core network of a home network. For instance, a subscribed UE may register with the home core network to access service(s) provided by the home core network. As used herein, the term “roaming network” may refer to a network (e.g., a visiting public land mobile network (VPLMN)) operated by a roaming partner of an operator that operates a home network. As used herein, the term “roaming core network” may refer to a core network of a roaming network. For instance, a UE may register with the roaming core network to access service(s) provided by the roaming core network.

[0054] Migrating subscribers (e.g., UEs) from one network to another network during low- traffic periods allows an operator to shut down parts (e.g., base stations) of their network in order to save energy. However, the number of subscribers that are required to be migrated to a roaming core network can be substantially high (e.g., 100, 200, 500 or more). Thus, it may be desirable to optimize control plane procedures (e.g., registration procedure) for migrating subscribers between networks of different operators in a network sharing agreement. In anexample, during low-traffic periods, the majority of the UEs of subscribers may be in an idle mode. Thus, it may not be efficient for UEs of subscribers to generate control plane messages to migrate from a home network to another network and back to the home network (e.g., registration request messages), because generating such control plane messages consumes power of the UE of a subscriber and uses network resources. Additionally, the high C-plane load may limit the frequency at which the home core network migrates UEs of subscribers to another network in order to reduce the energy consumption of the home network.

[0055] Aspects of the present disclosure provides techniques for reducing control plane signaling when two or more operators are network sharing by allowing UEs (e.g., with reduced or low mobility) to migrate between core networks (e.g., a home core network of an HPLMN operator of subscribers of the UEs and a roaming core network of another PLMN operator) without re-registering every time when the UE enters one of the core networks. The home core network and the roaming core network are separate core networks. In some instances, the HPLMN operator and the other PLMN operator may have their own RANs (with partially overlapping coverage areas or non-overlapping coverage areas). In other instances, the HPLMN operator and the other PLMN operator may share the same RAN (e.g., in a MORAN configuration discussed above). In an aspect of the present disclosure, to enable a UE to dynamically migrate between a first core network (e.g., a core network of one operator) and a second core network (e.g., a core network of another operator) without re-registering with the first core network and / or the second core network, the first core network may assign, to the UE, respectively a long-term UE context for use in the first core network and / or a long-term UE context for use in the second core network.

[0056] As used herein, the term “long-term UE context” may refer to a UE context that is for storage on a long-term basis at a core network and at a UE. Storing a UE context on a longterm basis means a core network stores the UE context for a longer period than a normal period. For instance, a core network may typically store a context of a UE (having a normal registration with the core network) only while the UE is in the core network but releases or deletes the UE context once the UE leaves (or de -registers from) the core network. That is, a normal period for UE context storage is from the time when the UE is registered with the core network till the time when the UE leaves the core network. In contrast, in the present disclosure, a core network may maintain, store, preserve, or retain a long-term UE context of a UE (having a long-term registration with the core network) not only while the UE is in the core network but also after the UE switches to another core network. Similarly, a UE having a long-term registration with a core network may maintain, store, preserve, or retain a long-term UE context of the UE inassociation with the core network not only while the UE is in the core network but also after the UE has switched to another core network. Because a long-term UE context is to be maintained at a core network and / or at a UE for an extended period of time (e.g., longer than a normal period), the long-term UE context may also be referred to as an extended- term UE context.

[0057] The terms “long-term UE context information” and “long-term registration information” may refer to information associated with a long-term UE context and may be used interchangeably herein, such that a description referring to one of the terms shall be treated as though the description also referred to the other term.

[0058] According to an aspect of the present disclosure, a first core network entity of a first core network may receive, from a UE, a registration request to register with the first core network. The first core network may be a core network of a first operator. In an example, the first core network entity may be an access and mobility function (AMF) of the first core network. The first core network may assign a long-term UE context to the UE. The long-term UE context may be configured to be maintained by a second core network and configured to allow the UE to switch from communicating with the first core network to communicating with the second core network without re-registering with the second core network. The second core network may be a core network of a second operator different than the first operator. In response to the registration request, the first core network entity may transmit, to the UE, a registration response including information associated with the long-term UE context assigned to the UE. In aspects, the first core network may be part of a home network of the UE and the second core network may be part of a roaming network of the UE.

[0059] In aspects, the first core network entity may determine whether to assign the longterm UE context to the UE based on at least one of the following: a mobility pattern of the UE, a quality of service (QoS) of the UE, an energy source of the UE, a geographical location of the UE, or a network sharing agreement between the first operator and the second operator. For mobility pattern, the assignment may be based on the UE’s past history indicating that the UE is registered with the same cell of the first core network during the last certain number of transitions (e.g., 2, 3, 5, 6, 10 or more transitions) to and from the second core network. That is, the UE may have a low mobility. Alternatively, the assignment may be based on a predicted mobility pattern of the UE being a low mobility pattern. For QoS, the assignment may be based on the first core network entity determining to minimize interruption time for the UE (e.g., because the UE is a high-priority UE). Alternatively, the assignment may be based on an interruption time requirement (e.g., a high QoS subscription) of the UE. For energy source, theassignment may be based on the UE having an unlimited energy resource (e.g., when the UE is plugged in for charging, which may also serve as an indirect indicator of low mobility). For geographical location, the assignment may be based on the geographical location of the UE, e.g., being within a registration area of the home network where the network agreement may apply. In aspects, the network agreement may include a maximum or threshold number of UE contexts that may be stored on a long-term basis by the second core network and / or information (e.g., long-term UE context identifiers) to be used by UEs to request long-term registration with the second core network.

[0060] In aspects, the first core network entity may select an identifier for the long-term UE context from a pool of long-term UE context identifiers. The first core network entity may configure the long-term UE context pool based on the network sharing agreement between the first operator and the second operator.

[0061] In aspects, the long-term UE context information provided to the UE may include at least one of the following: an identifier (e.g., a long-term UE context identifier) associated with the long-term UE context, registration update timer information, information associated with a bearer (e.g., associated with protocol data unit (PDU) session(s)) configured for the UE, information associated with a service (e.g., associated with PDU session(s)) configured for the UE, information associated with a registration area of the UE (e.g., tracking area information), information associated with a reachability configuration of the UE (e.g., paging capabilities and / or parameters), information associated with a security configuration of the UE (e.g., parameters associated with encryption and / or integrity protection), or information associated with one or more capabilities of the UE.

[0062] The UE may move between the first core network and the second core network. In aspects, during an initial registration with the second core network, the UE may transmit a long-term registration request to the second core network (e.g., a core network entity, such as an AMF, of the second core network). The long-term registration request may include the longterm UE context assigned to the UE by the first core network entity. In response, the second core network may transmit, to the UE, registration update timer information. The registration update timer information may be configured to be maintained by the UE and configured to allow the UE to switch from communicating with the first core network to communicating with the second core network without re-registering with the second core network. In some instances, the registration update timer information may include an indication of a registration update timer duration (time length), which may be used by the UE to configure a periodic registration update timer (e.g., for the UE to update its mobility information to the second corenetwork). In some instances, the registration update timer information may be based on the network agreement.

[0063] In aspects, the first core network may offload the UE to the second core network. For instance, the first core network may transition into an energy efficiency state, and the offloading may be triggered by the state transition. In some instances, the UE may return to the first core network when the first core network transitions out of the energy efficiency state. In general, the UE may switch back and forth between communicating with the first core network and communicating with the second core network based on certain conditions. During each switch to communicating with the second core network, the UE (having the long-term registration with the second core network) is not required to re-register with the second core network (1) if a registration update timer configured at the UE according to the registration update timer information is running (e.g., in progress or active) and (2) if the UE is in the same registration area as when the UE last registered with the second core network. In aspects, the second core network may continue to maintain, preserve, retain, and / or store the long-term UE context associated with the UE after the UE leaves the second core network. Upon the UE reentering the second core network, the second core network may use the maintained long-term UE context to communicate with the UE. In aspects, the UE may continue to maintain, preserve, retain, and / or store the long-term UE context associated with the second core network after the UE leaves the second core network. Upon the UE re-entering the second core network, the UE may use the maintained long-term UE context to communicate with the second core network.

[0064] In aspects, a second core network entity of the second core network may determine to revoke or cancel the long-term registration of the UE based on at least one of a mobility pattern (e.g., excessive mobility) of the UE or the network sharing agreement (e.g., a violation of the agreement or an anomaly against the network agreement detected by the second core network). In an example, the second core network entity may determine that the number of active long-term UE contexts stored at the second core network is greater than the threshold number of long-term UE contexts agreed in the network sharing agreement. Upon revoking the long-term registration, the second core network entity may delete the long-term UE context of the UE. In aspects, when the UE returns to the first core network, the UE may inform the first core network entity that the long-term registration or long-term UE context has been revoked by the second core network. In response, the first core network entity may delete the long-term UE context assigned to the UE.

[0065] In aspects, the first core network entity may assign another long-term UE context (e.g., a second long-term UE context) to the UE. The second long-term UE context may be configured to be maintained by the first core network entity and configured to allow the UE of a subscriber to roam from the second network to the first network without re-registering with the first core network. The first core network entity may maintain a registration update timer associated with the second long-term UE context. Such and other aspects will be described in more detail later herein.

[0066] Aspects of the present disclosure provide various advantages. For example, assigning a low-mobility UE with long-term UE contexts in association with a roaming core network and a home core network can enable the UE to migrate between the roaming core network and the home core network without re-registration. This can significantly decrease C- plane load (e.g., signaling) in the home core network and in the roaming core network. Additionally, battery consumption at the low-mobility UE, energy consumption at the roaming core network, and / or energy consumption at the home core network can be reduced. Further, the reduced C-plane load may allow network sharing outside of low-traffic periods, for example, to provide capacity augmentation or load balancing. While the present disclosure is described in the context of optimizing C-plane traffic and / or operations in network sharing between a home network and a roaming network, the mechanisms described herein may be used for network sharing among any suitable core networks (e.g., between two roaming core networks).

[0067] The present disclosure may use the term “serving network device” to refer to a network node or network device (or a portion thereof) that serves a UE. As used herein, the terms “transmit to,” “receive from,” and “cooperate with,” (and their variations) include communications that may or may not involve communications through one or more intermediate devices or nodes. The term “acquire” (and its variations) includes acquiring in the first instance or reacquiring after the first instance. The term “connection” may mean a physical connection or a logical connection.

[0068] The present disclosure uses 5G NR as an example of a wireless network and may use smartphones and / or extended reality headsets as an example of UEs. It is intended and shall be understood that such examples are merely illustrative, and the present disclosure is applicable to other wireless networks and user equipment.

[0069] FIGS. 1A-1D are diagrams of example embodiments of various configurations of wireless communication systems, according to one illustrated aspect of the disclosure. FIG. 1A illustrates an example MORAN configuration. FIG. IB illustrates an example MOCNconfiguration. FIGS. 1C-1D illustrate example configuration where a home network operator (of a subscriber of a UE) and a roaming network operator, each having their own core networks and own RANs. In FIG. 1C, cell coverage areas of the home network operator and the roaming network operator are non-overlapping. On the other hand, in FIG. ID, cell coverage areas of the home network operator and the roaming network operator are partially overlapping.

[0070] A wireless communication system (e.g., a 5G system) may include a core network, one or more RANs, and one or more UEs. A RAN may include one or more network nodes, which may be referred to as RAN nodes. At a high level, a RAN may provide radio interfaces and manage radio resources for radio communications with one or more UEs and may communicate with a respective core network. A core network may include one or more network servers and / or network equipment and / or software implementing various network functions. At a high level, a core network may be in communication with a RAN, handle user data of UEs in communication with (served by) the RAN, and manage access and mobility of the UEs.

[0071] As used herein, the term “network apparatus” may refer to any component of a RAN or a core network in a wireless communication system. Examples of network apparatuses include, without limitation, apparatuses implementing aspects of 5G NR, among others. The present disclosure describes embodiments related to 5G NR and embodiments that involve aspects defined by 3rd Generation Partnership Project (3GPP). However, it is contemplated that embodiments relating to other wireless networking technologies are encompassed within the scope of the present disclosure.

[0072] The following description provides further details of examples of RAN nodes. In a 5G NR network, a gNodeB (also known as gNB) may include, e.g., a node that provides NR user plane and control plane protocol terminations towards the UE and that is connected via a NG interface to the 5G core (5GC), e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 3.2, which is hereby incorporated by reference herein.

[0073] A gNB supports various protocol layers, e.g., Layer 1 (LI) - physical layer, Layer 2 (L2), and Layer 3 (L3).

[0074] The layer 2 (L2) of NR is split into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Service Data Adaptation Protocol (SDAP), where, e.g.: o The physical layer offers to the MAC sublayer transport channels; o The MAC sublayer offers to the RLC sublayer logical channels; o The RLC sublayer offers to the PDCP sublayer RLC channels; o The PDCP sublayer offers to the SDAP sublayer radio bearers;o The SDAP sublayer offers to 5GC quality of service (QoS) flows; o Control channels include broadcast control channel (BCCH) and physical control channel (PCCH).

[0075] Layer 3 (L3) includes, e.g., radio resource control (RRC), e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 6, which is hereby incorporated by reference herein.

[0076] A gNB central unit (gNB-CU) includes, e.g., a logical node hosting, e.g., radio resource control (RRC), service data adaptation protocol (SDAP), and packet data convergence protocol (PDCP) protocols of the gNB or RRC and PDCP protocols of the en-gNB, that controls the operation of one or more gNB distributed units (gNB-DUs). The gNB-CU terminates the Fl interface connected with the gNB -DU. A gNB-CU may also be referred to herein as a CU, a central unit, a centralized unit, or a control unit.

[0077] A gNB Distributed Unit (gNB-DU) includes, e.g., a logical node hosting, e.g., radio link control (RLC), media access control (MAC), and physical (PHY) layers of the gNB or en- gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interface connected with the gNB-CU. A gNB-DU may also be referred to herein as DU or a distributed unit.

[0078] As used herein, the term “network node” or “RAN node” may refer to any of a gNB, a gNB-CU, or a gNB-DU, or any combination of them. A RAN (radio access network) node or network node such as, e.g., a gNB, gNB-CU, or gNB-DU, or parts thereof, may be implemented using, e.g., an apparatus with at least one processor and / or at least one memory with processor-readable instructions (“program”) configured to support and / or provision and / or process CU and / or DU related functionality and / or features, and / or at least one protocol (sub-)layer of a RAN (radio access network), e.g., layer 2 and / or layer 3. Different functional splits between the central and distributed unit are possible. An example of such an apparatus and components will be described in connection with FIG. 10 below.

[0079] The gNB-CU and gNB-DU parts may, e.g., be co-located or physically separated. The gNB-DU may even be split further, e.g., into two parts, e.g., one including processing equipment and one including an antenna. A central unit (CU) may also be called baseband unit / radio equipment controller / cloud-RAN / virtual-RAN (BBU / REC / C-RAN / V-RAN), open- RAN (O-RAN), or part thereof. A distributed unit (DU) may also be called remote radio head / remote radio unit / radio equipment / radio unit (RRH / RRU / RE / RU), or part thereof. Hereinafter, in various example embodiments of the present disclosure, a network node, which supports at least one of central unit functionality or a layer 3 protocol of a radio access network,may be, e.g., a gNB-CU. Similarly, a network node, which supports at least one of distributed unit functionality or a layer 2 protocol of the radio access network, may be, e.g., a gNB-DU.

[0080] A gNB-CU may support one or multiple gNB-DUs. A gNB-DU may support one or multiple cells and, thus, could support a serving cell for a user equipment (UE) or support a candidate cell for handover, dual connectivity, and / or carrier aggregation, among other procedures.

[0081] A UE may be or include a wireless or mobile device, an apparatus with a radio interface to interact with a RAN (radio access network), a smartphone, an in-vehicle apparatus, an Internet of Things (loT) device, or a M2M device, among other types of user equipment. Such a UE may include: at least one processor; and at least one memory including program code; where the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform certain operations, such as, e.g., RRC connection to the RAN. An example of components of a UE will be described in connection with FIG. 10. In embodiments, the UE may be configured to generate a message (e.g., including a cell ID) to be transmitted via radio towards a RAN (e.g., to reach and communicate with a serving cell). In embodiments, the UE may generate and transmit and receive RRC messages containing one or more RRC PDUs (packet data units). Persons skilled in the art will understand RRC protocol as well as other procedures a UE may perform.

[0082] In the example of a 5G NR network, a RAN provides one or more cells, which define a coverage area of the RAN. As described above, a RAN may include a gNB of a 5G NR network or may include any other apparatus configured to control radio communication and manage radio resources within a cell. As used herein, the term “resource” may refer to radio resources, such as a resource block (RB), a physical resource block (PRB), a radio frame, a subframe, a time slot, a sub-band, a frequency region, a sub-carrier, a beam, etc. In embodiments, the network node may be called a base station.

[0083] Referring to FIG. 1 A, a core network 110 of an operator A and a core network 112 of an operator B may utilize a shared RAN (e.g., including a common RAN node 120) to communicate with UEs of subscribers of respective operators in a MORAN configuration. The core networks 110 and 112 will be discussed more fully below with reference to FIG. 2. The RAN node 120 may be a gNB as discussed above. As discussed above, in a MORAN configuration, multiple operators may share the same RAN, but radio carriers of the RAN are not shared by the operators. In the illustrated example of FIG. 1 A, a subscriber of the UE 150 has a subscription to the operator A, a subscriber of the UE 152 has a subscription to the operator B, and the RAN node 120 communicates with the UE 150 of the operator A usingfrequency Fl (e.g., a radio carrier frequency) and communicates with the UE 152 of the operator B using frequency F2 (e.g., a radio carrier frequency), where Fl and F2 are different frequencies. As further shown in FIG. 1 A, the RAN node 120 may provide a coverage area 130 using the frequency Fl and a coverage area 131 using the frequency F2, where the coverage areas 130 and 131 may be independent of each other. The UE 150 and the UE 152 may be as discussed above.

[0084] Referring to FIG. IB, a core network 110 of an operator A and a core network 112 of an operator B may utilize a shared RAN (e.g., including a common RAN node 122) to communicate with UEs of subscribers of respective operators using a MOCN configuration. The RAN node 122 may be a gNB as discussed above. As discussed above, in a MOCN configuration, multiple operators may share the same RAN including radio carriers. In the illustrated example of FIG. IB, a subscriber of the UE 150 has a subscription to the operator A, a subscriber of the UE 152 has a subscription to the operator B, and the RAN node 122 communicates with the UE 150 of the operator A and the UE 152 of the operator B using the same frequency F3 (e.g., a radio carrier frequency). As further shown in FIG. 1A, the RAN node 122 may provide a coverage area 132.

[0085] Referring to FIG. 1C, a subscriber of the UE 150 may have a subscription to an operator (e.g., operator A) operating a core network 114 and a corresponding RAN (e.g., including a RAN node 124) providing a coverage area 133 (e.g., using a frequency F4). The core network 114 may be referred to as a home core network 114 of the UE 150. Further, the home core network 114 and the corresponding RAN (including the RAN node 124) may be referred to as a home network of the UE 150.

[0086] As shown by the arrow 160 in FIG. 1C, at time tl, the UE 150 may travel from the coverage area 133 to a coverage area 134 operated by a different operator (e.g., operator B), where the coverage area 134 is non-overlapping with the coverage area 133. Stated differently, the UE 150 may roam to a network of the operator B. The operator B may operate a core network 116 and a corresponding RAN (e.g., including a RAN node 126) that provides the coverage area 133 (e.g., using a frequency F5). The core network 116 may be referred to as a roaming core network 116. Further, the roaming core network 116 and the corresponding RAN (including the RAN node 126) may be referred to as a roaming network of the UE 150. The core networks 114 and 116 will be discussed more fully below with reference to FIG. 2. Each of the RAN nodes 124 and 126 may be a gNB as discussed above.

[0087] As further shown by the arrow 162 in FIG. 1C, at time t2, the subscriber of the UE 150 may roam from the roaming network back to the home network. In some scenarios, the UE150 may move back and forth between the home network and the roaming network. In an example, the UE 150 may leave its home network (e.g., in the area 133) during daytime (e.g., at time tl) and enter the roaming network (e.g., in the area 134), and may return (move back) to the home network during night-time (e.g., at time t2).

[0088] Referring to FIG. ID, the wireless communication system configuration shown in FIG. ID is substantially similar to the wireless communication system configuration of FIG. 1C. However, the home network operator A may have a coverage area 135 that is partially overlapping with a coverage area 136 of the roaming network operator B. In an example, the home network operator A may determine to shut down parts (e.g., the RAN node 124) of its network to save energy during a certain time period, and may offload the UE 150 to the roaming network (i.e., the UE 150 may be served by the RAN node 126 and the roaming core network 112 of the roaming network operator B) during that period.

[0089] FIGS. 1A-1D provide examples and are merely illustrative of configurations of wireless communication systems. Persons skilled in the art will understand that the wireless communication systems shown in FIGS. 1A-1D includes components not illustrated in FIGS. 1A-1D and will understand that other user equipment may be in communication with each respective RAN nodes.

[0090] FIG. 2 is a block diagram of an example wireless communication system. A 5G NR network may be described as an example of the wireless communication system shown in FIG. 2, and it is intended that aspects of the following description shall be applicable to other types of network systems, as well. The wireless communication system may include a user plane and a control plane as shown and described herein. At a high level, the user plane carries user traffic while the control plane carries signaling traffic.

[0091] Example functions of the user plane and control plane components are described below. The example functions of user plane and control plane components are merely illustrative, and it shall be understood that additional operations may be performed by the components described herein.

[0092] The wireless communication system includes a core network and a RAN 225. The core network may include various core network functions. For instance, the core network includes an authentication server function (AUSF) 211, an AMF 212, and a session management function (SMF) 213. The core network also includes a network slice selection function (NSSF) 214, a network exposure function (NEF) 215, a network repository function (NRF) 216, and a UDM 217, which may include UDR 224.

[0093] Additional network functions of the core network include a trusted application function (AF) 218 and a policy control function (PCF) 219.

[0094] The AUSF 211, the AMF 212, the SMF 213, the NSSF 214, the NEF 215, the NRF 216, the UDR 224, the UDM 217, AF 218, and PCF 219 are part of the control plane of the wireless communication system. The core network further includes a user plane function (UPF)226 in the user plane.

[0095] The UE 150 may be connected to a data network (DN) 227 via a radio access network node of a RAN 225, the UPF 226, and a N6 interface of the core network. The RAN 225 may include one or more components described in connection with FIGS. 1A-1D, such as one or more radio network nodes. However, the RAN 225 may not be limited to such components. The UPF 226 provides connection for data being communicated between the DN227 and the UE 150 via a radio access node of the RAN 225. The DN 227 is used to provide services from service providers, such as third party service providers, for example.

[0096] The AMF 212 is configured to perform connection and mobility management tasks. In some instances, the core network may include multiple sets of AMFs 212, where a set of AMFs 212 may serve a certain area and certain network slice(s). The AUSF 211 receives authentication requests from the AMF 212 and interacts with UDM 217 to authenticate and validate network responses for determination of successful authentication. The SMF 213 conducts PDU session management, as well as manages session context with the UPF 226.

[0097] The NSSF 214 may select a network slice instance (NSI) to serve the UE 150 and determine the network slice selection assistance information (NSSAI) for the network slice instance. The NSSF 214 may determine an AMF 212 or set of AMFs 212 that can serve the selected NSI to the UE 150. The NEF 215 secures access to network services for third parties to create specialized network services. The NRF 216 acts as a repository to store profiles of network functions to allow the network functions discover each other.

[0098] The UDM 217 generates authentication vectors for use by the AUSF 211 and AMF 212 and provides user identification handling. The UDM 217 may be connected to the UDR 224 which stores data associated with authentication, applications, or the like. The AF 218 provides application services to a user (e.g., streaming services, etc.). The PCF 219 provides policy control functionality. For example, the PCF 219 may assist in network slicing and mobility management, as well as provide quality of service (QoS) and charging functionality. In some instances, the UDM 217 and / or UDR 224 may be referred to as a network data component.

[0099] In an aspect, each of the core networks 110 and 112 of FIGS. 1A-1B and / or each of the core networks 114 and 116 of FIGS. 1C-1D may be similar to the core network discussed above. For instance, each of the core networks 110, 112, 114, and 116 may include an AUSF, an AMF, an SMF, an NSSF, an NEF, an NRF, a UDR, a UDM, an AF 218, a PCF, and a UPF similar to the AUSF 211, the AMF 212, the SMF 213, the NSSF 214, the NEF 215, the NRF 216, the UDR 224, the UDM 217, AF 218, PCF 219, and the UPF 226, respectively.

[0100] FIG. 2 is merely an example of components of a network system, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the network system may include other components not illustrated in FIG. 2. In embodiments, the network system may not include every component illustrated in FIG. 2. In embodiments, the components and connections may be implemented with different connections than those illustrated in FIG. 2. Such and other embodiments are contemplated to be within the scope of the present disclosure.

[0101] FIG. 3 is a diagram of example operations of a network system that provisions for network sharing, according to one illustrated aspect of the present disclosure. The following paragraphs will describe various signals and operations. It will be understood that a described signal may have associated operations and a described operation may have associated signals. Accordingly, a described signal may also be an operation and a described operation may also be a signal. Additionally, FIG. 3 will describe signals between and operations performed by various network components, such as those shown at the top of FIG. 3. Specifically, the components include a UE 302, a home network 304, and a roaming network 306. In an aspect, the UE 302 may correspond to the UE 150 of FIGS. 1 A-1D and each of the home network 304 and the roaming network 306 may have entities (e.g., access nodes of an access network and network functions of a core network) as discussed above with reference to FIG. 2. The network components are illustrative, and it is contemplated that other components may be involved in the signals or may perform the operations. In some examples, each of the UE 302, the home network 304, and the roaming network 306 may implement the operations using an apparatus with components as shown in FIG. 10. In some examples, the operations of the home network 304 may be implemented by a core network entity (e.g., an AMF 212) at the home network 304. Similarly, the operations of the roaming network 306 may be implemented by a core network entity (e.g., an AMF 212) at the roaming network 306. One or more of the following operations may be implemented in connection with the operations of the present disclosure, such as the examples discussed above with reference to FIG. 2.

[0102] At operation 310, the UE 302 registers with the home network 304. A user of the UE 302 may be a subscriber of the home network 304. The UE 302 may transmit, and the home network 304 may receive a registration request to register with the home network 304. In response, the home network 304 may transmit, and the UE 302 may receive a registration response (e.g., a registration acceptance message). In some instances, after completing registration with the home network 304, the UE 302 may operate in an idle mode and camp on the home network 304.

[0103] At operation 312, the UE 302 determines to camp on the roaming network 306. In some instances, the determination to camp on the roaming network 306 may be based on a detection or an indication that the home network 304 is transitioning to a certain state (e.g., an energy efficiency state during which the home network 304 may power down certain network resources associated with the home network 304 due to low traffic at the home network 304).

[0104] At operation 314, the UE 302 implicitly deregisters from the home network 304, for example, by switching to camp on the roaming network 306. In general, the implicit deregistration may be based on a de-registration timer being timed out with no communication or contact between the UE 302 and the home network 304 for the duration of the timer. In other words, if the UE 302 doesn’t provide signs of life periodically, the UE 302 may be considered de -registered by the home network 304. Alternatively, the implicit de-registration may be based on a trigger (at the UE 302) to re-register with a roaming network, e.g., since no suitable cells of the home network are available. In general, de-registration (with the home network 304) at the UE 302 and de-registration (of the UE 402) at the home network 304 can occur at different times.

[0105] At operation 316, the UE 302 registers with the roaming network 306. For instance, the UE 302 may transmit, and the roaming network 306 may receive a registration request to register with the roaming network 306. In response, the roaming network 306 may transmit, and the UE 302 may receive a registration response (e.g., a registration acceptance message). In some instances, after completing registration with the roaming network 306, the UE 302 may operate in an idle mode and camp on the roaming network 306.

[0106] At operation 318, the UE 302 determines to return to the home network 304, for example, based on the home network 304 having transitioned out of the energy efficiency state and operates in a normal state.

[0107] At operation 320, the UE 302 implicitly deregisters from the roaming network 306 by switching to camp on the home network 304. In general, the implicit de-registration may be based on a de-registration timer being timed out with no communication or contact betweenthe UE 302 and the roaming network 306 for the duration of the timer or based on a trigger (at the UE 302) to re-register with a roaming network, e.g., since no suitable cells of the home network are available. In general, de-registration (with the roaming network 306) at the UE 302 and de-registration (of the UE 402) at the roaming network 306 can occur at different times.

[0108] At operation 322, upon re-entering the home network 304, the UE 302 registers (reregisters) with the home network 304.

[0109] At each registration (e.g., at operations 310, 316, 322), the respective home network 304 or the roaming network 306 may create a UE context to store information related to the UE 302, for example, including, but not limited to, e.g., UE capability and / or information associated with bearer(s) configured for the UE, information associated with service(s) configured for the UE, information associated with a registration area of the UE (e.g., tracking area information), information associated with a reachability configuration of the UE (e.g., paging capabilities and / or parameters, such as paging subgroup identifier(s) and / or mobile initiate connection(s)), information associated with one or more capabilities of the UE, and information associated with a security configuration of the UE (e.g., parameters associated with encryption and / or integrity protection). The respective core network may store the UE context (e.g., at a memory 1050 of FIG. 10) while the UE 302 is at the respective core network but may release or delete the UE context upon the UE 302 switching to another core network. That is, the home network 304 may create and store a UE context for the UE 302 at operation 310 and upon the UE 302 switching to the roaming network 306 (leaving the home network 304), the home network 304 may release or delete the UE context. Similarly, the roaming network 306 may create and store a UE context for the UE 302 at operation 316 and upon the UE 302 switching to the home network 304 (leaving the roaming network 306), the roaming network 306 may release or delete the UE context.

[0110] As discussed above, if the offloading of the UE 302 from the home network 304 to the roaming network 306 is to conserve energy, it may be counter-productive to increase C- plane load (e.g., from registration operations), which may in turn increase battery consumption at the UE 302 and increase energy consumption and network resources at the home network 304 and the roaming network 306. Further, if explicit de-registration is performed, e.g., at operations 314 and / or 320, the C-plane load may be further increased. Furthermore, the procedure or operations 310-322 discussed above are per UE. Thus, when there is a large number of UEs for such migrations, re-registration operations with the home network 304 (upon the UE 302 switching to the home network 304) and / or re-registration operations withthe roaming network 306 (upon the UE 302 switching to the home network 304) can significantly increase the C-plane load.

[0111] The signals and operations of FIG. 3 are merely illustrative, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the signals and operations may include others not illustrated in FIG. 3. In embodiments, the signals and operations may not include every signal and operation illustrated in FIG. 3. In embodiments, the signals and operations may be implemented in a different order than that illustrated in FIG. 3. Such and other embodiments are contemplated to be within the scope of the present disclosure.

[0112] In certain scenarios, during low-traffic periods, such as night-time, the location of many UEs may not vary (e.g., a UE may be stationary when its user is asleep). Hence, during network sharing for these scenarios, a UE may likely leave its home network (e.g., in a registration area, RA#1) and enter a roaming network (e.g., in a registration area, RA#2) during daytime, leave the roaming network in RA#2, and return to the home network in RA#1 every night. If the UE’s behavior is known during the time of the roaming (e.g., for energy efficiency) by the home core network and the roaming core network, there is no need for the UE to reregister upon entering different networks (e.g., the home core network and the roaming core network).

[0113] In certain network sharing scenarios, it may be beneficial for a home core network to dynamically migrate its subscribers (e.g., UEs) from the home core network to roaming core network(s) instead of based on a static or fixed schedule.

[0114] The following will describe example operations for reducing C-plane signaling for network operators with a network sharing agreement so that a UE (e.g., the UE 150) may dynamically migrate between networks (e.g., a home core network and one or more roaming core networks) without re-registering upon entering a pre -registered network. FIGS. 4A and 4B show example signals and operations of a network system. FIGS. 5, 6, and 9 show example operations of a UE, FIG. 7 show example operations of a network apparatus (e.g., at a home core network), and FIG. 8 shows example operations of a network apparatus (e.g., at a roaming core network).

[0115] FIGS. 4A and 4B are diagrams showing control plane signaling (e.g., messages) sent between a UE 402, a home network 404, and a roaming network 406, and operations performed by the UE 402, the home network 404, and the roaming network 406, according to one illustrated aspect of the present disclosure. The home network 404 may be operated by a first operator to which a subscriber of the UE 402 has a subscription. The roaming network 406may be operated by a second operator different than the first operator. In an aspect, the UE 402 may correspond to the UE 150 of FIGS. 1A-1D, and each of the home network 404 and the roaming network 406 may have entities (e.g., access nodes of an access network and network functions of a core network) as discussed above with reference to FIG. 2. In an example, the home network 404 and the roaming network 406 may correspond respectively to the operator A network and the operator B network discussed above with reference to FIG. 1A. In an example, the home network 404 and the roaming network 406 may correspond respectively to the home network and the roaming network discussed above with reference to FIG. 1C. In an example, the home network 404 and the roaming network 406 may correspond respectively to the home network and the roaming network discussed above with reference to FIG. ID. The network entities are illustrative, and it is contemplated that other entities may be involved in the signals or may perform the operations. In some examples, each of the UE 402, the home network 404, and the roaming network 406 may comprise a core network implementing the operations using an apparatus with components as shown in FIG. 10. In some examples, the operations of the home network 404 may be implemented by a core network entity (e.g., an AMF 212) at the home network 404. Similarly, the operations of the roaming network 406 may be implemented by a core network entity (e.g., an AMF 212) at the roaming network 406. One or more of the following operations may be implemented in connection with the operations of the present disclosure, such as the examples discussed above with reference to FIGS. 2-3.

[0116] At operation 411, the home network 404 and the roaming network 406 establish a network sharing agreement (e.g., a roaming agreement for energy efficiency purposes as discussed above). The network sharing agreement may specify a maximum number of UE contexts for long-term storage at the roaming network 406. Storage of contexts has associated costs and can be a factor when dimensioning, e.g., core network resources. Hence, it may be beneficial to have the number of these long-term UE contexts agreed between operators in a network sharing agreement. Additionally or alternatively, the network sharing agreement may include information (e.g., parameters) related to the long-term UE contexts. In an example, the long-term UE context information may include a list of long-term UE context identifiers that the home network 404 may assign to UEs for long-term registration with the roaming network 406. As will be discussed more fully below, the roaming network 406 may accept a long-term registration request from a UE if the long-term registration request includes long-term UE context information that matches information agreed in the network sharing agreement. In a further example, the long-term UE context identifier may have some specific formatting scheme as agreed between the home network 404 and the roaming network 406 to preventspoofing. Additionally or alternatively, the network sharing agreement may include information associated with a registration updater timer. For instance, the network sharing agreement may specify a periodic time duration or length for which a UE may update the roaming core network with the UE mobility information.

[0117] At operation 412, the UE 402 transmits, and the home network 404 receives a registration request to register with the home network 404.

[0118] At operation 413, upon receiving the registration request, the home network 404 determines if the UE 402 is qualified for long-term registration with the roaming network 406 (e.g., for energy efficiency purposes).

[0119] In aspects, the home network 404 may determine which of its UEs is suitable for long-term registration with a roaming core network based on a variety of factors. For instance, the determination may be based on at least one of a mobility pattern of a respective UE, a QoS associated with the respective UE, an energy source of the respective UE, or a geographical location of the respective UE.

[0120] In an example, the home network 404 may determine that the UE 402 is qualified for long-term registration based on the UE 402 having a low mobility pattern. For instance, the low mobility pattern may be based on the UE 402 ’s past history indicating that the UE 402 is registered with the same cell of the home network 404 during the last certain number of transitions (e.g., 2, 3, 5, 6, 10 or more transitions) to and from the roaming network 406. Alternatively, the low mobility pattern may be based on a prediction of the UE 402 ’s mobility pattern.

[0121] In an example, the home network 404 may determine that the UE 402 is qualified for long-term registration based on a QoS of the UE 402. For instance, the home network 404 may determine to minimize interruption time for the UE 402 (e.g., based on the UE being a high-priority UE). Alternatively, the assignment may be based on an interruption time requirement (e.g., a high QoS subscription) of the UE.

[0122] In an example, the home network 404 may determine that the UE 402 is qualified for long-term registration based on the UE 402 having an unlimited energy resource (e.g., if the UE 402 is plugged in for charging).

[0123] In an example, the home network 404 may determine that the UE 402 is qualified for long-term registration based on a geographical location of the UE being within a registration area of the home network 404 in which the network agreement may apply.

[0124] In aspects, if the home network 404 determines that the UE 402 is qualified for long-term registration, the home network 404 assigns a long-term UE context to the UE 402.To that end, the home network 404 may configure and manage a pool of identifiers for longterm UE contexts based on the network sharing agreement established at operation 411. For instance, each of the long-term UE context identifiers in the pool is specified (or agreed) in the network sharing agreement. The home network 404 may select an identifier for the long-term UE context from the pool of long-term UE context identifiers (provisioned based on the network sharing agreement established at operation 411). Stated differently, the home network 404 may assign the long-term UE context to the UE 402 based on at least one of the following: a mobility pattern of the UE 402, a QoS associated with the UE 402, an energy source of the UE 402, a geographical location of the UE 402, or the network sharing agreement established at operation 411. In general, the home network 404 may manage a pool of long-term UE contexts, where each long-term UE context may include an identifier of the respective longterm UE context (e.g., the identifier as specified in the network sharing agreement) and any other UE context information.

[0125] The long-term UE context may be assigned to the UE 402 for use in the roaming network 406. That is, the long-term UE context is specific to the roaming network 406 and the UE 402. As will be discussed more fully below, the long-term UE context may be configured to be maintained by the roaming network 406 and the UE 402 and configured to allow the UE 402 to switch from the home network 404 to the roaming network 406 without re-registering with the roaming network 406.

[0126] At operation 414, the home network 404 transmits, and the UE 402 receives a registration response including information associated with the long-term UE context assigned to the UE 402. Upon receiving information associated with the long-term UE context, the UE 402 may save (store) the long-term UE context information at a memory (e.g., memory 1050 of FIG. 10) of the UE 402.

[0127] The long-term UE context information may include at least the long-term UE context identifier of the assigned long-term UE context, where the long-term UE context identifier is one of the long-term UE context identifiers agreed in the network sharing agreement. Additionally, the long-term UE context information may include registration update timer information. Additionally or alternatively, the long-term UE context information may include information associated with a bearer configured for the UE. Additionally or alternatively, the long-term UE context information may include information associated with a service configured for the UE. In an example, the information associated with the bearer and / or service may include contexts of PDU sessions and respective PDU session statuses (e.g., active or inactive). Additionally or alternatively, the long-term UE context information mayinclude information associated with a registration area of the UE (e.g., tracking area information). Additionally or alternatively, the long-term UE context information may include information associated with a reachability configuration of the UE (e.g., paging capabilities and / or parameters, such as paging subgroup identifier(s) and / or mobile initiate connection(s)). Additionally or alternatively, the long-term UE context information may include information associated with a security configuration of the UE (e.g., parameters associated with encryption and / or integrity protection). Additionally or alternatively, the long-term UE context information may include information associated with one or more capabilities of the UE.

[0128] In aspects, the home network 404 may have network sharing agreements with a plurality of roaming networks and may allow the UE 402 to roam to any one of the roaming networks. Thus, for each of the plurality of roaming networks, the home network 404 may assign a long-term UE context to the UE 402. Accordingly, the registration response at operation 414 may include an indication of the plurality of roaming networks and information associated with each long-term UE context assigned to the UE in association with a respective roaming network. In some examples, after registering with the home network 404, the UE 402 may operate in an idle mode and camp on the home network 404.

[0129] Subsequently, the home network 404 or RAN nodes (e.g., nodes or components, such as base stations at a RAN similar to the RAN 225) associated with the home network 404 may transition from a first network state to a second network state (e.g., an offloading state in which UEs are to be offloaded to another network). The network state transition may be the start of a network sharing period. The network state transition can be detected by the UE 402 or indicated to the UE 402 by the home network 404. As shown in FIG. 4 A, at operation 415 A, the UE 402 may detect that the home network 404 is transitioning to the offloading state. In an example, when the offloading state is an energy efficiency state for energy saving, the detection may be based on assistance information (previously provided to the UE 402 by the home network 404 or associated RAN nodes) indicating potential or scheduled sleep periods. Thus, the UE 402 may detect the state transition based on an absence of home network cells during that period. Alternatively, at operation 415B, the home network 404 may transmit, and the UE 402 may receive an indication that the home network 404 is transitioning to the offloading state. In an example, the home network 404 may transmit the network state transition indication via a system information block (SIB) broadcast or any other suitable signaling.

[0130] At operation 416, the home network 404 transmits, and the roaming network 406 receives an indication that the home network 404 is offloading UEs to the roaming network406. The indication may serve as a network sharing activation. In some instances, the indication of the home network 404 offloading UEs to the roaming network 406 can be optional.

[0131] As discussed above, in some examples, the offloading of the UEs may be triggered by the home network 404 transitioning to an energy efficiency state. To that end, a coverage area of the home network 404 may at least partially overlap with a coverage area of the roaming network 406 (e.g., as discussed above with reference to FIG. ID). The home network 404 may transition its cell(s) to the energy efficiency state by powering down base station(s) and / or other network resources in the respective cells. In general, upon transitioning the cell(s) to the energy efficiency state, the home network 404 may inform each roaming network that has an agreement with the home network 404 of the change of state (to the energy efficiency state). The indication can assist with UE reachability (paging) during the energy efficiency states of the home network 404.

[0132] At operation 417, upon indication from the home network 404 that the home network 404 is transitioning to the offloading state, the UE 402 implicitly deregisters from the home network 404, for example, based on a de-registration timer being timed out with no communication or contact between the UE 402 and the home network 404 for the duration of the timer or the triggering of a registration request with another network.

[0133] At operation 418, in response to the network state transition detected at operation 415A or indicated by the home network 404 at operation 415B, the UE 402 selects a roaming network for roaming. As discussed above, the registration response at operation 414 may include an indication of a list of roaming networks and information associated with each longterm UE context assigned to the UE in association with a respective roaming network. As such, the UE 402 may select a roaming network from the list of roaming networks indicated in the registration response. In the illustrated example of FIG. 4A, the UE 402 selects the roaming network 406.

[0134] After selecting the roaming network 406, the UE 402 may perform an initial registration with the roaming network 406. For example, at operation 419, the UE 402 transmits, and the roaming network 406 receives a long-term registration request including the information associated with the long-term UE context assigned to the UE 402 (by the home network 404 for use in the roaming network 406). The information associated with the longterm UE context assigned to the UE 402 may be referred to as long-term registration information.

[0135] At operation 420, the roaming network 406 verifies (or authenticates) the long-term registration information. As discussed above, the information associated with the long-termUE context may include a long-term UE context identifier. Also, the network sharing agreement may include a set of long-term UE context identifiers agreed between the home network 404 and the roaming network 406. Thus, as part of the verification or authentication, the roaming network 406 may determine whether the long-term UE context identifier received in long-term registration request matches one of the long-term UE context identifiers agreed in the network sharing agreement. If the received long-term UE context identifier matches one of the agreed long-term UE context identifiers, the verification is a pass and the roaming network 406 may accept the long-term registration request. If, however, the received long-term UE context identifier does not match any one of the agreed long-term UE context identifiers, the verification fails and the roaming network 406 may reject the long-term registration request. In the illustrated example of FIG. 4A, the verification is a pass and the long-term registration request is accepted. Upon the roaming network 406 accepting the long-term registration request, the roaming network 406 may save (store) the long-term UE context (received from the UE 402) at a memory (e.g., memory 1050 of FIG. 10) of the roaming network 406.

[0136] Thus, at operation 421, the roaming network 406 transmits, and the UE 402 receives a long-term registration response (e.g., a registration acceptance message) including registration update timer information. The registration update timer information may be configured to be maintained by the UE 402 and the roaming network 406 and configured to allow the UE 402 to switch from the home network 404 to the roaming network 406 without re-registering with the roaming network 406. The roaming network 406 may provide the UE 402 with the registration update timer information based on the verification at operation 420 is a pass. The registration update timer information may indicate information (e.g., a periodic time period) for configuring a periodic timer for the UE 402 to perform registration update with the roaming network 406. In aspects, the registration update timer information may include a periodic time period agreed in the network sharing agreement. In aspects, the roaming network 406 may assign a substantially long registration update time period (e.g., 30 minutes, 1 hours, or more than 2 hours) for registration update.

[0137] In some examples, after registering with the roaming network 406, the UE 402 may operate in an idle mode, camp on the roaming network 406, and perform registration area update according to the registration update timer information. For example, at operation 422, the UE 402 starts a registration update timer (e.g., a periodic timer) configured according to the registration update timer information received at operation 421. The UE 402 may perform registration area update, for example, according to a 3GPP registration area update procedure. For instance, the UE 402 may generally roam across cells freely within a certain registrationarea (e.g., the registration area at which the UE 402 requests the long-term registration) of the roaming network 406 without having to perform location registration for each cell. Upon an expiration of the registration update timer, the UE 402 may perform a registration area update procedure to update the roaming network 406 of its serving cell and mobility information.

[0138] At operation 423, the roaming network 406 may also start a registration update timer (e.g., a periodic timer) configured according to the same registration update timer information that is provided to the UE 402 at operation 421. In other words, the registration update timer at the roaming network 406 may be synchronized to the registration update timer at the UE 402 for registration area update operations. As such, the roaming network 406 may expect to receive a registration update from the UE 402 when its registration update timer expires. The registration update (e.g., including the UE 402’s serving cell and mobility information) may serve as an indication that the UE 402 is active and the UE 402 ’s long-term registration (with the roaming network 406) remains active or valid. If the roaming network 406 does not receive a registration area update when the registration update timer expires, the roaming network 406 may consider the long-term registration with the UE 402 is no longer valid and stop (or delete) the registration update timer. In aspects, the roaming network 406 may not implicitly detach the UE 402 as long as the registration update timer is running.

[0139] At operation 424, the UE 402 switches back to camp on the home network 404 (e.g., at a later time). The switching from the roaming network 406 to the home network 404 may be based on a state change at the home network 404 (e.g., when the home network 404 transitions out of the offloading state), where the state change ends the network sharing period.

[0140] At operation 429, the home network 404 transmits, and the roaming network 406 receives an indication of a state change at the home network 404. While FIGS. 4A-4B illustrates the home network 404 transmits the indication of the home network 404 ’s state change to the roaming network 406 after operation 424. In other instances, the home network 404 may transmit the indication of the home network 404 ’s state change to the roaming network 406 before operation 424. In some instances, the indication of the home network 404’ s state change can be optional.

[0141] As discussed above, upon the UE 402 receiving the long-term UE context from the home network 404 at operation 414, the UE 402 may store the long-term UE context at a memory of the UE 402. At operation 425, the UE 402 continues to maintain, preserve, retain, and / or store the long-term UE context associated with the roaming network 406 while camping on the home network 404. That is, when the UE 402 switches from the roaming network 406to the home network 404, the UE 402 may not release or delete the long-term UE context associated with the roaming network 406.

[0142] As discussed above, upon the roaming network 406 determining that the verification of the long-term UE context from the UE 402 is a pass at operation 420, the roaming network 406 may store the long-term UE context at a memory of the roaming network 406. At operation 426, the roaming network 406 continues to maintain, preserve, retain, and / or store the long-term UE context associated with the UE 402 while the UE 402 is at the home network 404. That is, when the UE 402 switches from the roaming network 406 to the home network 404, the roaming network 406 may not release or delete the long-term UE context of the UE 402.

[0143] At operation 427, the UE 402 determines to switch to camp on the pre-registered roaming network 406 (e.g., because the home network 404 is transitioning to the offloading state as discussed above at operations 415A and / or 415B).

[0144] At operation 428, the UE 402 camps on the pre-registered roaming network 406 without re-registering with the roaming network 406 based on the long-term UE context, a running registration update timer, and a current registration area of the UE 402 being the same as a registration area for which the long-term UE context is assigned. More specifically, the UE 402 may re-enter the roaming network 406 without re-registration if the UE 402 satisfies two conditions: (1) a registration update timer configured at the UE according to the registration update timer information is running (e.g., in progress or active); and (2) the UE 402 is in the same registration area as when the UE 402 requests for the long-term registration request at operation 419 (i.e., a current registration area of the UE 402 is the same as a registration area for which the long-term UE context is assigned and saved). Mechanisms for determining whether registration is required when the UE 402 enters a network will be discussed more fully below with reference to FIG. 5. The UE 402 may use the long-term UE context maintained at the UE 402 to communicate with the roaming network 406.

[0145] In a similar way, the roaming network 406 may use the long-term UE context maintained at the roaming network 406 to communicate with the UE 402 if the roaming network 406 determines that the registration update timer associated with the UE 402 (started operation 423) is running and the UE 402 is at the same registration area as the registration area for which the long-term UE context is saved,.

[0146] As can be seen, because each of the UE 402 and the roaming network 406 continues to maintain and store the long-term UE context after the UE 402 leaves the roaming network 406, the UE 402 and the roaming network 406 can communicate with each other using its ownstored long-term UE context upon the UE 402 re-entering the roaming network 406. Accordingly, the UE 402 is not required to re-register with the roaming network 406 to reestablish a UE context for communication with the roaming network 406.

[0147] In some scenarios, the UE 402 assigned with the long-term UE context may move out of the registration area for which the long-term UE context is assigned. In such scenarios, the UE 402 may follow 3GPP registration update procedures and perform a registration area update procedure. During this procedure, the roaming network 406 may revoke the long-term UE context for the UE 402 due to the UE 402 ’s mobility. For instance, the UE 402 may indicate that it has moved to a different registration area than the registration area at which the UE 402 last registered with the roaming network 406. Upon revoking the long-term UE context, the roaming network 406 may delete the long-term UE context and inform the UE 402 of the revocation of the long-term UE context (e.g., via a registration accept message) once the UE 402 leaves the roaming network 406. In general, the roaming network 406 may implicitly detach the UE 402 from the roaming network 406 or explicitly inform the UE 402 that the UE 402 is detached from the roaming network 406 once it leaves the roaming network 406, via the indication of the long-term UE context revocation. In other words, the UE 402 can continue to stay in the roaming network 406, but once it leaves the roaming network 406, there will be no long-term UE context stored for the UE 402 at the roaming network 406. Upon the UE 402 returning to its home network 404, the UE 402 may inform the home network 404 that the long-term UE context (assigned to the UE 402 by the home network 404) is revoked by the roaming network 406 as will be discussed more fully below with reference to FIG. 6.

[0148] In aspects, the home network 404 may assign a subset of its UEs, each with a longterm UE context, so that when those UEs return from a network sharing period, those UEs are not required to register with the home network 404 if their registration area has not changed.

[0149] As an example, the home network 404 may assign another long-term UE context (e.g., a second long-term UE context) to the UE 402 for use in the home network 404. The home network 404 may provide the second long-term UE context to the UE 402 as part of the registration response at operation 414. The second long-term UE context may be configured to be maintained by the home network 404 and the UE 402 and configured to allow the UE 402 to switch from the roaming network 406 to the home network 404 without re-registering with the home network 404.

[0150] In some examples, the home network 404 may provide the UE 402 with registration update timer information as part of the registration response at operation 414. The registration update timer information may include an indication of a periodic timer period for registrationupdate at the home network 404 similar to the registration update timer information provided by the roaming network 406. Further, each of the home network 404 and the UE 402 may continue to maintain a copy of the long-term UE context for use in the home network 404 after the UE 402 switches to register with the roaming network 406, for example, at operation 419. Further still, each of the home network 404 and the UE 402 may maintain a registration update timer in association with the second long-term UE context. The UE 402 may perform registration area update with the home network 404, for example, according to a 3GPP registration area update procedure.

[0151] Subsequently, when the UE 402 switches back to the home network 404 (e.g., at operation 424), the UE 402 is not required to re-register with the home network 404 if the UE 402 satisfies two conditions: (1) the registration update timer at the UE 402 configured in association with second long-term UE context is running (e.g., in progress or active); and (2) the UE 402 is in the same registration area as when the UE 402 was last in the home network 404 (i.e., a current registration area of the UE is the same as a registration area for which the second long-term UE context is assigned and saved). That is, the UE 402 and the home network 404 may communicate with each other, each using its own maintained long-term UE context, without requiring the UE 402 to re-register with the home network 404 when the above two conditions are satisfied. In some examples, the home network 404 may also provide an indication of whether a long-term UE context for the UE 402 is valid in the home network 404 (e.g., during a registration update procedure). In this way, if long-term UE context is valid, the UE 402 is not required to re-register with the home network 404 when the UE 402 returns to the home network 404 next time (e.g., at the end of a next network sharing period).

[0152] In aspects, the UE 402 may register different UE capabilities with different networks (e.g., different operator networks) for some reasons related to, for example, but are not limited to, a multiple-input multiple-output (MIMO) configuration, a carrier aggregation (CA) configuration, overheating issues, and / or an operator configuration. Accordingly, the information associated with the long-term UE context provided by the home network 404 to the UE 402 at operation 414 may optionally include UE capabilities. In general, UE capabilities can be included in a long-term UE context stored at the roaming network 406, the home network 404, and / or at the UE.

[0153] The signals and operations of FIGS. 4 A and 4B are merely illustrative, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the signals and operations may include others not illustrated in FIGS. 4 A and 4B. In embodiments, the signals and operations may not include every signal and operation illustratedin FIG.S 4 A and 4B. For example, in some instances, the home network 404 may dynamically inform the roaming network 406 every time when the home network 404 transitions into a state that requires offloading of UEs to the roaming network 406 (e.g., a network sharing activation) and every time when the home network 404 transitions out of that state (e.g., a network sharing deactivation). Generally, the home network 404 may inform the roaming network 406 of its needs for network sharing. In embodiments, the signals and operations may be implemented in a different order than that illustrated in FIGS. 4 A and 4B. Such and other embodiments are contemplated to be within the scope of the present disclosure.

[0154] FIG. 5 is a flow diagram of example operations of a UE of a subscriber of a network roaming between the network and another network, according to one illustrated aspect of the present disclosure. In an aspect, the UE may correspond to the UE discussed above with reference to FIGS. 1A-1D and / or the UE 402 discussed above with reference to FIGS. 4 A and 4B. In some examples, the UE may implement the operations using an apparatus with components as shown in FIG. 10. The operations of FIG. 5 may include similar mechanisms as discussed above with reference to FIGS. 4A and 4B. As illustrated, FIG. 5 includes a number of enumerated steps, but aspects of the operations in FIG. 5 may include additional steps before, after, and in between the enumerated steps. In some aspects, one or more of the enumerated steps may be omitted or performed in a different order.

[0155] At block 502, the UE registers with a home core network (e.g., a core network of the home network 404). For instance, the UE may transmit a registration request to the home core network.

[0156] At block 504, the UE receives long-term registration information per public land mobile network (PLMN) (e.g., for each of a plurality of PLMNs). In aspects, the UE may receive the per PLMN long-term registration information in a registration response from the home core network. The PLMNs may include the home core network (e.g., HPLMN) and one or more roaming core networks (e.g., VPLMNs, a core network of the roaming network 406). For instance, the long-term registration information may include at least a long-term UE context identifier and registration update timer information for each PLMN. In some instances, for each of the PLMNs, the long-term registration information may also include information associated with a bearer configuration, a service configuration, a registration area configuration, a reachability configuration of the UE, one or more capabilities of the UE, and / or a security configuration of the UE.

[0157] At block 506, the UE determines to switch to a different network. For instance, the UE determines to switch from the home core network to one of the roaming core networks, for example, similar to operation 418 of FIG. 4A.

[0158] At block 508, the UE determines whether the UE has previously registered with the network determined for the switching. If the UE has previously registered with a network, the UE may have started a registration update timer associated with that network. Accordingly, the UE may determine whether it has a running (active) registration update timer for the determined network or not as an indicator of whether the UE has previously registered with the determined network. If the UE determines that the UE has not previously registered with the determined network, the UE proceeds to block 510.

[0159] At block 510, the UE initiates a registration (e.g., an initial registration) with the determined network. For instance, the UE may transmit a long-term registration request including long-term registration information (e.g., a long-term UE context) assigned to the UE by the home core network in association with the determined network. If the long-term registration request is accepted by the determined network, the UE may receive a long-term registration acceptance response indicating a long-term registration procedure has been successfully completed. The long-term registration acceptance response also includes registration update timer information (e.g., an indication of a periodic registration update timer duration (time length)).

[0160] At block 512, upon the successful completion of the long-term registration procedure, the UE initiates (or starts) a periodic registration update timer. The UE may configure the periodic registration update timer according to the registration update timer information. The UE may update its mobility information to the roaming core network according to the registration update timer (e.g., upon an expiry of the registration update timer). The UE may also store a registration area identifier (ID) that identifies a current registration area of the UE.

[0161] Returning to block 508, if the UE determines that the UE has previously registered with the determined network (i.e., the determined network is a pre -registered network), the UE proceeds to block 514. At block 514, the UE determines whether a current registration area of the UE is the same as the registration area when the UE previously registered with the determined network. For instance, the UE may compare a registration area ID of the current registration area to the registration area ID of the previous registration area. For instance, the UE may store the previous registration area ID after the previous registration. If the UE determines that the current registration area of the UE is different than the previous registrationarea (i.e., the current registration area ID is different than the previous registration area ID), the UE proceeds to block 510 and re-registers with the determined network. If, however, the UE determines that the current registration area of the UE is the same as the previous registration area, the UE proceeds to block 516.

[0162] At block 516, the UE determines not to perform registration with the determined network based on the periodic registration timer hasn’t expired and the UE is at the same registration area. That is, the UE may re-enter the determined network without re-registering with the determined network.

[0163] While FIG. 5 is discussed in the context of the UE switching from the home core network to a roaming core network, the UE may also apply the operations 508-516 to determine whether a re-registration with the home core network is needed when the UE reenters the home core network.

[0164] FIG. 6 is a flow diagram of example operations of a UE migrating between networks, according to one illustrated aspect of the present disclosure. In an aspect, the UE may correspond to the UE discussed above with reference to FIGS. 1A-1D and / or the UE 402 discussed above with reference to FIGS. 4A and 4B. In some examples, the UE may implement the operations using an apparatus with components as shown in FIG. 10. The operations of FIG. 6 may include similar mechanisms as discussed above with reference to FIGS. 4A and 4B. As illustrated, FIG. 6 includes a number of enumerated steps, but aspects of the operations in FIG. 6 may include additional steps before, after, and in between the enumerated steps. In some aspects, one or more of the enumerated steps may be omitted or performed in a different order.

[0165] At block 602, the UE registers with a roaming core network (e.g., a core network of the roaming network 406). For instance, the UE may transmit a long-term registration request to register with the roaming core network. The long-term registration request may include a long-term UE context assigned to the UE by a home core network (e.g., a core network of the home network 404) of the UE.

[0166] At block 604, the UE receives an indication that the roaming core network revokes the long-term registration, for example, due to excessive mobility of the UE or a violation or anomaly against a network sharing agreement between the roaming core network and the home core network. In an example, the excessive mobility may be based on a registration update provided by the UE to the roaming core network. For instance, the registration update may indicate that the UE has moved to a different registration area than the registration area at which the UE last registered with the roaming core network. In an example, the roaming core networkmay detect the violation or anomaly against the network agreement based on the number of active long-term UE contexts stored at the roaming core network has reached or exceeded the threshold number of long-term UE contexts agreed in the network sharing agreement.

[0167] At block 606, the UE determines to switch to the home core network of the UE.

[0168] At block 608, the UE initiates a registration with the home core network. The UE may transmit, to the home core network, a registration request including information about the long-term registration with the roaming core network being revoked by the roaming core network. In other instances, the UE may re-enter the home core network without a reregistration and may inform the home core network of the long-term registration revocation by the roaming core network during a registration update procedure. In an example, the UE may include information associated with the revoked long-term UE context in a registration update message to the home core network. For instance, the registration update message may include a field indicating a status of the long-term UE context being revoked along with a long-term UE context identifier of the revoked long-term UE context.

[0169] FIG. 7 is a flow diagram of example operations of a network apparatus providing a long-term UE context to a UE, according to one illustrated aspect of the present disclosure. The network apparatus is at a first core network (e.g., a core network of a first operator) and may implement operations of a core network entity (e.g., AMF 212 of FIG. 2) of the first core network. In an aspect, the first core network corresponds to a core network of the home network 404 discussed above with reference to FIGS. 4A and 4B. In some examples, the network apparatus may implement the operations using an apparatus with components as shown in FIG. 10. The operations of FIG. 7 may include similar mechanisms as discussed above with reference to FIGS. 4A-4B and 5-6. As illustrated, FIG. 7 includes a number of enumerated steps, but aspects of the operations in FIG. 7 may include additional steps before, after, and in between the enumerated steps. In some aspects, one or more of the enumerated steps may be omitted or performed in a different order.

[0170] At block 702, the network apparatus (at the first core network) receives a registration request from a UE.

[0171] At block 704, the network apparatus (at the first core network) assigns a long-term UE context to the UE. The long-term UE context is configured to be maintained by a second core network and configured to allow the UE to switch from communicating with the first core network to communicating with the second core network without re-registering with the second core network. The second core network is a core network of a second operator different thanthe first operator. In aspects, the first core network may be part of a home network of the UE and the second core network may be part of a roaming network of the UE.

[0172] In aspects, the long-term UE context information provided to the UE includes at least one of the following: an identifier (e.g., a long-term UE context identifier) associated with the long-term UE context, registration update timer information, information associated with a bearer (e.g., associated with protocol data unit (PDU) session(s)) configured for the UE, information associated with a service (e.g., associated with PDU session(s)) configured for the UE, information associated with a registration area of the UE (e.g., tracking area information), information associated with a reachability configuration of the UE (e.g., paging capabilities and / or parameters), information associated with one more capabilities of the UE, or information associated with a security configuration of the UE (e.g., parameters associated with encryption and / or integrity protection).

[0173] At block 706, the network apparatus (at the first core network) transmits, to the UE in response to the registration request, a registration response including information of the longterm UE context assigned to the UE.

[0174] In aspects, the network apparatus further determines whether to assign the longterm UE context to the UE based on at least one of the following: a mobility pattern of the UE, a QoS for the UE, an energy source of the UE, a geographical location of the UE, or a network sharing agreement between the first core network and the second core network, for example, as discussed above with reference to operation 413 of FIG. 4A.

[0175] In aspects, the network apparatus further selects an identifier for the long-term UE context from a pool of long-term UE context identifiers, where the pool of long-term UE context identifiers is provided based on a network sharing agreement between the first operator and the second operator, for example, as discussed above with reference to operation 413 of FIG. 4A.

[0176] In aspects, the network apparatus further offloads at least the UE to the second core network. In aspects, the network apparatus further transitions the first core network to an energy efficiency state. For instance, the offloading the UE to the second core network may be based on the first core network transitioning to the energy efficiency state.

[0177] In aspects, the network apparatus further receives, from the UE, an indication of a revocation of the long-term UE context (e.g., sent to the UE by the second core network). In response to the indication of the revocation of the long-term UE context, the network apparatus deletes the long-term UE context assigned to that UE.

[0178] In aspects, the network apparatus (at the first core network) further assigns a second long-term UE context to the UE. The second long-term UE context is configured to be maintained by the first core network entity and configured to allow the UE to switch from communicating with the second core network to communicating with the first core network without re-registering with the first core network. In aspects, the network apparatus (at the first core network) further maintains a registration update timer associated with the second longterm UE context. For instance, the first core network may expect to receive a registration update from the UE when the registration update timer expires. The registration update (e.g., including the UE’s serving cell and mobility information) may serve as an indication that the UE is active and the second long-term UE context remains valid for use in the first core network.

[0179] FIG. 8 is a flow diagram of example operations of a network apparatus performing a long-term registration with a UE, according to one illustrated aspect of the present disclosure. The network apparatus is at a first core network (e.g., a core network of a first operator) and may implement operations of a core network entity (e.g., AMF 212 of FIG. 2) of the first core network. In an aspect, the first core network corresponds to the roaming network 406 discussed above with reference to FIGS. 4 A and 4B. The network apparatus may implement operations of a core network entity (e.g., AMF 212 of FIG. 2) of the first core network. In some examples, the network apparatus may implement the operations using an apparatus with components as shown in FIG. 10. The operations of FIG. 8 may include similar mechanisms as discussed above with reference to FIGS. 4A-4B and 5-6. As illustrated, FIG. 8 includes a number of enumerated steps, but aspects of the operations in FIG. 8 may include additional steps before, after, and in between the enumerated steps. In some aspects, one or more of the enumerated steps may be omitted or performed in a different order.

[0180] At block 802, the network apparatus (at the first core network) receives, from a UE, a long-term registration request including information of a long-term UE context of the UE.

[0181] At block 804, the network apparatus (at the first core network) of the first core network transmits, to the UE in response to the long-term registration request, registration update timer information. The registration update timer information is configured to be maintained by the UE and configured to allow the UE to switch from communicating with a second core network to communicating with the first core network without re-registering with the first core network. The second core network is a core network of a second operator different from the first operator. In an example, the long-term UE context of the UE is assigned by the second core network. In aspects, the first core network is part of a roaming network of the UE, and the second core network is part of a home network of the UE.

[0182] In aspects, at least one of the long-term UE context of the UE or the registration update timer information is provisioned based on a network sharing agreement between the first operator and the second operator.

[0183] In aspects, the long-term UE context information in the long-term registration request received at block 802 includes at least one of the following: an identifier (e.g., a longterm UE context identifier) associated with the long-term UE context, registration update timer information, information associated with a bearer (e.g., associated with protocol data unit (PDU) session(s)) configured for the UE, information associated with a service (e.g., associated with PDU session(s)) configured for the UE, information associated with a registration area of the UE (e.g., tracking area information), information associated with a reachability configuration of the UE (e.g., paging capabilities and / or parameters), information associated with one or more capabilities of the UE, or information associated with a security configuration of the UE (e.g., parameters associated with encryption and / or integrity protection).

[0184] In aspects, the network apparatus further authenticates the identifier of the longterm UE context, for example, as discussed above with reference to operation 420 of FIG. 4A.

[0185] In aspects, the network apparatus further maintains the long-term UE context of the UE at a memory (e.g., a memory 1050 of FIG. 10) and uses the maintained long-term UE context for the UE when the UE switches from communicating with the second core network to communicating with the first core network, for example, as discussed above with reference to operation 428 of FIG. 4B.

[0186] In aspects, the network apparatus further revokes the long-term UE context of the UE based on at least one of a mobility pattern (e.g., excessive mobility) of the UE or a network sharing agreement between the operator and the second operator. In aspects, the network apparatus further transmits, to the UE, an indication that the long-term UE context of the UE is revoked.

[0187] FIG. 9 is a flow diagram of example operations of a UE migrating between networks, according to one illustrated aspect of the present disclosure. In an aspect, the UE corresponds to the UE 150 discussed above with reference to FIGS. 1A-1D or the UE 402 discussed above with reference to FIGS. 4A and 4B. In some examples, the UE may implement the operations using an apparatus with components as shown in FIG. 10. The operations of FIG. 9 may include similar mechanisms as discussed above with reference to FIGS. 4A-4B and 5-6. As illustrated, FIG. 9 includes a number of enumerated steps, but aspects of the operations in FIG. 9 may include additional steps before, after, and in between the enumerated steps. Insome aspects, one or more of the enumerated steps may be omitted or performed in a different order.

[0188] At block 902, the UE receives information of a long-term UE context assigned to the UE in association with a first core network. The long-term UE context is configured to enable the UE to switch from communicating with a second core network to communicating with the first core network without re-registering with the first core network. In aspects, one of the first core network or the second core network is part of a home network of the UE, and the other one of the first core network or the second core network is part of a roaming network of the UE.

[0189] In aspects, the long-term UE context information includes at least one of the following: an identifier (e.g., a long-term UE context identifier) associated with the long-term UE context, registration update timer information, information associated with a bearer (e.g., associated with protocol data unit (PDU) session(s)) configured for the UE, information associated with a service (e.g., associated with PDU session(s)) configured for the UE, information associated with a registration area of the UE (e.g., tracking area information), information associated with a reachability configuration of the UE (e.g., paging capabilities and / or parameters), information associated with one or more capabilities of the UE, or information associated with a security configuration of the UE (e.g., parameters associated with encryption and / or integrity protection).

[0190] At block 904, the UE switches from communication with the second core network to communication with the first core network, where the communication with the first core network is based on the long-term UE context. In aspects, the switching is in response to an energy efficiency state transition associated with the second core network. In aspects, the communication with the first core network may include receiving paging information from the first core network (e.g., when the UE is camped on the first core network). In aspects, the communication with the first core network may include transmitting and / or receiving registration messages associated with a registration update procedure.

[0191] In aspects, the long-term UE context is assigned to the UE based on at least one of the following: a mobility pattern of the UE, a QoS for the UE, an energy source of the UE, a geographical location of the UE, or a network sharing agreement between the first operator and the second operator, for example, as discussed above with reference to operation 413 of FIG. 4A.

[0192] In aspects, the UE further maintains the long-term UE context associated with the first core network (e.g., at a memory 1050 of FIG. 10) while the UE is in communication withthe second core network, where the communication with the first core network is based on the maintained long-term UE context. For instance, upon the UE switching to communicating with the first core network, the UE may retrieve the maintained long-term UE context from memory and use the maintained long-term UE context for the communication with the first core network.

[0193] In aspects, the long-term UE context at 902 can be assigned to the UE by the second core network for use in the first core network. For instance, the second core network may be a home core network of the UE, and the first core network may be a roaming core network of the UE. Thus, in some instances, the UE further transmits, to the second core network, a registration request to register with the second core network, and as part of receiving the information of the long-term UE context at block 902, the UE receives, from the second core network in response to the registration request, a registration response including the information of the long-term UE context. In some instances, the UE further transmits, to the first core network, a long-term registration request including the information of the long-term UE context. In response to the long-term registration request, the UE receives, from the first core network, information associated with a registration update timer. In some instances, the UE communicates with the first core network without a re-registration with the first core network based on the long-term UE context and based on the registration update timer associated with the first core network being in progress.

[0194] In other aspects, the long-term UE context at 902 can be assigned to the UE by the first core network for use in the first core network. For instance, the first core network may be a home core network of the UE, and the second core network may be a roaming core network of the UE. Thus, in some instances, the UE further transmits, to the first core network, a registration request to register with the first core network, and as part of receiving the information of the long-term UE context at block 902, the UE further receives, from the first core network in response to the registration request, a registration response including the information of the long-term UE context. In some instances, the UE further receives, from the first core network, an indication that the long-term UE context associated with the first core network has been revoked. In response to the indication that the long-term UE context associated with the first core network has been revoked, the UE releases the long-term UE context. In some instances, the UE further transmits, to the second core network, a notification to inform the second core network that the long-term UE context associated with the first core network has been revoked.

[0195] Referring now to FIG. 10, there is shown a block diagram of example components of a UE or a network apparatus. The apparatus includes an electronic storage 1010, a processor 1020, a memory 1050, and a network interface 1040. The various components may be communicatively coupled with each other. The processor 1020 may be and may include any type of processor, such as a single-core central processing unit (CPU), a multi-core CPU, a microprocessor, a digital signal processor (DSP), a System-on-Chip (SoC), or any other type of processor. The memory 1050 may be a volatile type of memory, e.g., RAM, or a non-volatile type of memory, e.g., NAND flash memory. The memory 1050 includes processor-readable instructions that are executable by the processor 1020 to cause the apparatus to perform various operations, including those mentioned herein, such as the operations of FIGS. 3, 4A-4B, and 9.

[0196] The electronic storage 1010 may be and include any type of electronic storage used for storing data, such as hard disk drive, solid state drive, and / or optical disc, among other types of electronic storage. The electronic storage 1010 stores processor-readable instructions for causing the apparatus to perform its operations and stores data associated with such operations, such as storing data relating to 5G NR standards, among other data. The network interface 1040 may implement wireless networking technologies such as 5G NR and / or other wireless networking technologies.

[0197] The components shown in FIG. 10 are merely examples, and persons skilled in the art will understand that an apparatus includes other components not illustrated and may include multiples of any of the illustrated components. Such and other embodiments are contemplated to be within the scope of the present disclosure.

[0198] Further embodiments of the present disclosure include the following examples.

[0199] Example 1.1. A method comprising: receiving, by a first core network entity of a first core network, from a user equipment (UE), a registration request, wherein the first core network is a core network of a first operator; assigning, by the first core network entity, a long-term UE context to the UE, the longterm UE context configured to be maintained by a second core network and configured to allow the UE to switch from communicating with the first core network to communicating with the second core network without re-registering with the second core network, wherein the second core network is a core network of a second operator different than the first operator; and transmitting, to the UE in response to the registration request, a registration response including the long-term UE context assigned to the UE.

[0200] Example 1.2. The method of Example 1.1, further comprising:determining whether to provide the long-term UE context for the UE based on at least one of the following: a mobility pattern of the UE, a quality of service (QoS) of the UE, an energy source of the UE, a geographical location of the UE, or a maximum number of long-term UE contexts for UEs based on a network sharing agreement between the first operator and the second operator.

[0201] Example 1.3. The method of Example 1.1 or Example 1.2, further comprising: selecting, by the first core network entity, an identifier for the long-term UE context from a pool of long-term UE context identifiers, wherein the pool of long-term UE context identifiers is provided based on a network sharing agreement between the first operator and the second operator.

[0202] Example 1.4. The method of any one of Examples 1.1-1.3, wherein the longterm UE context assigned to the UE comprises at least one of the following: an identifier of the long-term UE context, registration update timer information, information associated with a bearer configured for the UE, information associated with a service configured for the UE, information associated with a registration area of the UE, information associated with a reachability configuration of the UE, or information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

[0203] Example 1.5. The method of any one of Examples 1.1-1.4, wherein: the first core network is part of a home network of the UE, and the second core network is part of a roaming network of the UE.

[0204] Example 1.6. The method of any one of Examples 1.1-1.5, further comprising: offloading, by the first core network entity, communications for the UE to the second core network.

[0205] Example 1.7. The method of Example 1.6, further comprising: transitioning, by the first core network entity, to an energy efficiency state.

[0206] Example 1.8. The method of any one of Examples 1.1-1.7, further comprising: receiving, by the first core network entity from the UE, an indication of a revocation of the long-term UE context by the second core network; anddeleting, by the first core network entity in response to receipt of the indication of the revocation of the long-term UE context, the long-term UE context for UE.

[0207] Example 1.9. The method of any one of Examples 1.1-1.5, further comprising: assigning, by the first core network entity, a second long-term UE context to the UE, the second long-term UE context configured to be maintained by the first core network entity and configured to allow the UE to switch communication from the second core network to the first core network without re-registering with the first core network.

[0208] Example 1.10. The method of Example 1.9, further comprising: maintaining a registration update timer associated with the second long-term UE context.

[0209] Example 2.1. A method comprising: receiving, by a first core network entity of a first core network, from a user equipment (UE), a long-term registration request including a long-term UE context of the UE, wherein the first core network is a core network of a first operator; and transmitting, by the first core network entity, to the UE in response to the long-term registration request, registration update timer information configured to be maintained by the UE and configured to allow the UE to switch from communicating with a second core network to communicating with the first core network without re-registering with the first core network, wherein the second core network is a core network of a second operator different than the first operator.

[0210] Example 2.2. The method of Example 2.1, wherein the first core network is part of a roaming network of the UE, and wherein the second core network is part of a home network of the UE.

[0211] Example 2.3. The method of Example 2.1 or Example 2.2, wherein at least one of the long-term UE context of the UE or the registration update timer information is provisioned based on a network sharing agreement between the first operator and the second operator.

[0212] Example 2.4. The method of any one of Examples 2.1-2.3, wherein the long-term UE context comprises at least one of the following: an identifier of the long-term UE context, information associated with a bearer configured for the UE, information associated with a service configured for the UE. information associated with a registration area of the UE, information associated with a reachability configuration of the UE, information associated with a security configuration of the UE, orinformation associated with one or more capabilities of the UE.

[0213] Example 2.5. The method of Example 2.4, further comprising: authenticating the identifier of the long-term UE context.

[0214] Example 2.6. The method of any one of Examples 2.1-2.5, further comprising: maintaining, at the first core network, the long-term UE context of the UE; and using the maintained long-term UE context for the UE when the UE switches from the second core network to the first core network.

[0215] Example 2.7. The method of Example 2.1-2.6, further comprising: revoking, by the first core network entity, the long-term UE context of the UE based on at least one of a mobility pattern of the UE or a network sharing agreement between the first operator and the second operator.

[0216] Example 2.8. The method of Example 2.7, further comprising: transmitting, by the first core network entity, to the UE, an indication that the long-term UE context of the UE is revoked.

[0217] Example 3.1. A method comprising: receiving, by a user equipment (UE), a long-term UE context assigned to the UE in association with a first core network, the long-term UE context configured to enable the UE to switch from communicating with a second core network of a second operator to communicating with the first core network without re-registering with the first core network, wherein the first core network is a core network of a first operator, and wherein the second core network is a core network of a second operator different than the first operator; and switching, by the UE, communication with the second core network to communication with the first core network, wherein the communication with the first core network is based on the long-term UE context.

[0218] Example 3.2. The method of Example 3.1, wherein one of the first core network or the second core network is part of a home network of the UE, and wherein the other one of the first core network or the second core network is part of a roaming network of the UE.

[0219] Example 3.3. The method of any one of Examples 3.1-3.2, further comprising: maintaining, by the UE, the long-term UE context associated with the first core network while the UE is in communication with the second core network.

[0220] Example 3.4. The method of any one of Examples 3.1-3.3, wherein the long-term UE context comprises at least one of the following: an identifier of the long-term UE context, registration update timer information,information associated with a bearer configured for the UE, information associated with a service configured for the UE. information associated with a registration area of the UE, information associated with a reachability configuration of the UE, information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

[0221] Example 3.5. The method of any one of Examples 3.1-3.4, further comprising: transmitting, by the UE to the second core network, a registration request to register with the second core network, wherein the receiving the long-term UE context comprises: receiving, from the second core network in response to the registration request, a registration response including the long-term UE context.

[0222] Example 3.6. The method of any one of Examples 3.1-3.5, further comprising: transmitting, by the UE, to the first core network, a long-term registration request including the long-term UE context, and receiving, by the UE from the first core network in response to the long-term registration request, information associated with a registration update timer.

[0223] Example 3.7. The method of any one of Example 3.6, further comprising: camping, by the UE on the first core network without a re-registration with the first core network based on the long-term UE context and based on the registration update timer associated with the first core network being in progress.

[0224] Example 3.8. The method of any one of Examples 3.1-3.4, further comprising transmitting, by the UE to the first core network, a registration request to register with the first core network, wherein the receiving the long-term UE context comprises: receiving, by the UE from the first core network in response to the registration request, a registration response including the long-term UE context.

[0225] Example 3.9. The method of any one of Examples 3.1-3.8, further comprising: receiving, by the UE from the first core network, an indication that the long-term UE context associated with the first core network has been revoked; and releasing, by the UE in response to the indication that the long-term UE context associated with the first core network has been revoked, the long-term UE context.

[0226] Example 3.10. The method of Example 3.9, further comprising:transmitting, by the UE to the second core network, a notification to inform the second core network that the long-term UE context associated with the first core network has been revoked.

[0227] Example 3.11. The method of any one of Examples 3.1-3.10, wherein the switching to the communication with the first core network is in response to an energy efficiency state transition associated with the second core network.

[0228] Example 4. An apparatus comprising: at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the apparatus at least to perform the method of any one of Examples 1.1-1.10.

[0229] Example 5. An apparatus comprising: at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the apparatus at least to perform the method of any one of Examples 2.1-2.8.

[0230] Example 6. An apparatus comprising: at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the apparatus at least to perform the method of any one of Examples 3.1- 3.11.

[0231] Example 7. A non-transitory processor-readable medium including program code, which when executed by one or more processors, causes the one or more processors at least to perform the method of any one of Examples 1.1-1.10.

[0232] Example 8. A non-transitory processor-readable medium including program code, which when executed by one or more processors, causes the one or more processors at least to perform the method of any one of Examples 2.1-2.8.

[0233] Example 9. A non-transitory processor-readable medium including program code, which when executed by one or more processors, causes the one or more processors at least to perform the method of any one of Examples 3.1-3.11.

[0234] The embodiments and aspects disclosed herein are examples of the present disclosure and may be embodied in various forms. For instance, although certain embodiments herein are described as separate embodiments, each of the embodiments herein may be combined with one or more of the other embodiments herein. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the presentdisclosure in virtually any appropriately detailed structure. Like reference numerals may refer to similar or identical elements throughout the description of the figures.

[0235] The phrases “in an aspect,” “in aspects,” “in various aspects,” “in some aspects,” or “in other aspects” may each refer to one or more of the same or different aspects in accordance with this present disclosure. The phrase “a plurality of’ may refer to two or more.

[0236] The phrases “in an embodiment,” “in embodiments,” “in various embodiments,” “in some embodiments,” or “in other embodiments” may each refer to one or more of the same or different embodiments in accordance with the present disclosure. A phrase in the form “A or B” means “(A), (B), or (A and B).” A phrase in the form “at least one of A, B, or C” means “(A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).”

[0237] Any of the herein described methods, programs, algorithms or codes may be converted to, or expressed in, a programming language or computer program. The terms “programming language” and “computer program,” as used herein, each include any language used to specify instructions to a computer, and include (but is not limited to) the following languages and their derivatives: Assembler, Basic, Batch files, BCPL, C, C+, C++, Delphi, Fortran, Java, JavaScript, machine code, operating system command languages, Pascal, Perl, PL1, Python, scripting languages, Visual Basic, metalanguages which themselves specify programs, and all first, second, third, fourth, fifth, or further generation computer languages. Also included are database and other data schemas, and any other meta-languages. No distinction is made between languages which are interpreted, compiled, or use both compiled and interpreted approaches. No distinction is made between compiled and source versions of a program. Thus, reference to a program, where the programming language could exist in more than one state (such as source, compiled, object, or linked) is a reference to any and all such states. Reference to a program may encompass the actual instructions and / or the intent of those instructions.

[0238] While aspects of the present disclosure have been shown in the drawings, it is not intended that the present disclosure be limited thereto, as it is intended that the present disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular aspects. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

CLAIMS:

1. A method of a first core network entity of a first core network, the method comprising: receiving, from a user equipment (UE), a registration request, wherein the first core network is a core network of a first operator; assigning a long-term UE context to the UE, the long-term UE context configured to be maintained by a second core network and configured to allow the UE to switch from communicating with the first core network to communicating with the second core network without re-registering with the second core network, wherein the second core network is a core network of a second operator different than the first operator; and transmitting, to the UE, in response to the registration request, a registration response including the long-term UE context assigned to the UE.

2. The method of claim 1, further comprising: determining whether to provide the long-term UE context for the UE based on at least one of the following: a mobility pattern of the UE, a quality of service (QoS) of the UE, an energy source of the UE, a geographical location of the UE, or a maximum number of long-term UE contexts for UEs based on a network sharing agreement between the first operator and the second operator.

3. The method of claim 1 or claim 2, further comprising: selecting an identifier for the long-term UE context from a pool of long-term UE context identifiers, wherein the pool of long-term UE context identifiers is provided based on a network sharing agreement between the first operator and the second operator.

4. The method of any one of claims 1-3, wherein the long-term UE context assigned to the UE comprises at least one of the following: an identifier of the long-term UE context, registration update timer information, information associated with a bearer configured for the UE,information associated with a service configured for the UE, information associated with a registration area of the UE, information associated with a reachability configuration of the UE, or information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

5. The method of any one of claims 1-4, wherein: the first core network entity is part of a home network of the UE, and the second core network is part of a roaming network of the UE.

6. The method of any one of claims 1-5, further comprising: offloading communications for the UE to the second core network.

7. The method of claim 6, further comprising: transitioning to an energy efficiency state.

8. The method of any one of claims 1-7, further comprising: receiving, from the UE, an indication of a revocation of the long-term UE context by the second core network; and deleting, in response to receipt of the indication of the revocation of the long-term UE context, the long-term UE context for UE.

9. The method of any one of claims 1-5, further comprising: assigning, a second long-term UE context to the UE, the second long-term UE context configured to be maintained by the first core network entity and configured to allow the UE to switch communication from the second core network to the first core network without reregistering with the first core network.

10. The method of claim 9, further comprising: maintaining a registration update timer associated with the second long-term UE context.

11. A method of a first core network entity of a first core network, the method comprising:receiving, from a user equipment (UE), a long-term registration request including a long-term UE context of the UE, wherein the first core network is a core network of a first operator; and transmitting, to the UE, in response to the long-term registration request, registration update timer information configured to be maintained by the UE and configured to allow the UE to switch from communicating with a second core network to communicating with the first core network without re-registering with the first core network, wherein the second core network is a core network of a second operator different than the first operator.

12. The method of claim 11, wherein the first core network is part of a roaming network of the UE, and wherein the second core network is part of a home network of the UE.

13. The method of claim 11 or claim 12, wherein at least one of the long-term UE context of the UE or the registration update timer information is provisioned based on a network sharing agreement between the first operator and the second operator.

14. The method of any one of claims 11-13, wherein the long-term UE context comprises at least one of the following: an identifier of the long-term UE context, information associated with a bearer configured for the UE, information associated with a service configured for the UE. information associated with a registration area of the UE, information associated with a reachability configuration of the UE, information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

15. The method of claim 14, further comprising: authenticating the identifier of the long-term UE context.

16. The method of any one of claims 11-15, further comprising: maintaining the long-term UE context of the UE; and using the maintained long-term UE context for the UE when the UE switches from the second core network to the first core network.

17. The method of claim 11-16, further comprising: revoking the long-term UE context of the UE based on at least one of a mobility pattern of the UE or a network sharing agreement between the first operator and the second operator.

18. The method of claim 17, further comprising: transmitting, to the UE, an indication that the long-term UE context of the UE is revoked.

19. A method of a user equipment (UE), the method comprising: receiving a long-term UE context assigned to the UE in association with a first core network, the long-term UE context configured to enable the UE to switch from communicating with a second core network of a second operator to communicating with the first core network without re-registering with the first core network, wherein the first core network is a core network of a first operator, and wherein the second core network is a core network of a second operator different than the first operator; and switching communication with the second core network to communication with the first core network, wherein the communication with the first core network is based on the long-term UE context.

20. The method of claim 19, wherein one of the first core network or the second core network is part of a home network of the UE, and wherein the other one of the first core network or the second core network is part of a roaming network of the UE.

21. The method of any one of claims 19-20, further comprising: maintaining, by the UE, the long-term UE context associated with the first core network while the UE is in communication with the second core network.

22. The method of any one of claims 19-21, wherein the long-term UE context comprises at least one of the following: an identifier of the long-term UE context, registration update timer information, information associated with a bearer configured for the UE, information associated with a service configured for the UE. information associated with a registration area of the UE,information associated with a reachability configuration of the UE, information associated with a security configuration of the UE, or information associated with one or more capabilities of the UE.

23. The method of any one of claims 19-22, further comprising: transmitting to the second core network, a registration request to register with the second core network, wherein the receiving the long-term UE context comprises: receiving, from the second core network in response to the registration request, a registration response including the long-term UE context.

24. The method of any one of claims 19-23, further comprising: transmitting to the first core network, a long-term registration request including the long-term UE context, and receiving, by the UE from the first core network in response to the long-term registration request, information associated with a registration update timer.

25. The method of any one of claim 24, further comprising: camping on the first core network without a re-registration with the first core network based on the long-term UE context and based on the registration update timer associated with the first core network being in progress.

26. The method of any one of claims 19-22, further comprising transmitting to the first core network, a registration request to register with the first core network, wherein the receiving the long-term UE context comprises: receiving from the first core network in response to the registration request, a registration response including the long-term UE context.

27. The method of any one of claims 19-26, further comprising: receiving from the first core network, an indication that the long-term UE context associated with the first core network has been revoked; and releasing, in response to the indication that the long-term UE context associated with the first core network has been revoked, the long-term UE context.

28. The method of claim 27, further comprising: transmitting, to the second core network, a notification to inform the second core network that the long-term UE context associated with the first core network has been revoked.

29. The method of any one of claims 19-28, wherein the switching to the communication with the first core network is in response to an energy efficiency state transition associated with the second core network.

30. An apparatus comprising: at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the apparatus at least to perform the method of any one of claims 1-18.

31. A user equipment comprising: at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the apparatus at least to perform the method of any one of claims 19-29.

32. A computer program comprising instructions, wherein execution of the computer program by at least one processor of an apparatus causes the apparatus to perform the method of any one of claims 1-18.

33. A computer program comprising instructions, wherein execution of the computer program by at least one processor of a user equipment causes the user equipment to perform the method of any one of claims 19-29.

34. A computer-readable medium comprising instructions, which when executed by at least one processor of an apparatus causes the apparatus to perform the method of any one of claims 1-10.

35. A computer-readable medium comprising instructions, which when executed by at least one processor of a user equipment causes the user equipment to perform the method of any one of claims 19-29.

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