Public Land Mobile Network Support for Standalone Non-Public Access Networks

Abstract

A user equipment (UE) registered to a Standalone Non-Public Network (SNPN) is also capable of accessing services on a Public Land Mobile Network (PLMN). The UE accesses the PLMN by transmitting a first signal to a data network; receiving a second signal from the data network in response to the first signal, where the second signal identifies the PLMN configured to be accessed by the UE via the data network; and transmitting a Session Initiation Protocol (SIP) registration request to the PLMN via the data network.

Description

[0001] Inventors: R. R. Matolia, A. P. Prabhakar, H. Pu, K. Keith, M. M. A. Tahar, M. Sadiq, N. A. Naik, V. Venkataraman Background Art

[0002] A user equipment (UE) may be connected to a Standalone Non-Public Network (SNPN). An SNPN generally refers to a non-public use deployment of 5G system with network functions that do not rely on a Public Land Mobile Network (PLMN). However, the UE may access the PLMN when connected to the SNPN. Therefore, there is a need for a mechanism configured to provide PLMN services to the UE when connected to the SNPN. Summary of the Invention

[0003] In some exemplary embodiments, a method is performed by a user equipment (UE) registered to a Standalone Non-Public Network (SNPN). The method includes: transmitting a first signal to a data network; receiving, in response to the first signal, a second signal from the data network, wherein the second signal identifies a Public Land Mobile Network (PLMN) configured to be accessed by the UE via the data network; and transmitting, via the data network, a Session Initiation Protocol (SIP) registration request to the PLMN.

[0004] In other exemplary embodiments, a user equipment (UE) having a transceiver and a processor is provided. The transceiver is configured to communicate with one or more networks. The processor is configured to perform operations including: registering to a Standalone Non-Public Network (SNPN); transmitting a first signal to a data network via the SNPN; receiving, in response to the first signal, a second signal from the data network, wherein the second signal identifies a Public Land Mobile Network (PLMN) configured to be accessed by the UE via the data network; and transmitting, via the data network, a Session Initiation Protocol (SIP) registration request to the PLMN.

[0005] In still other exemplary embodiments, a method is performed by a private branch exchange of a Standalone Non-Public Network (SNPN). The method includes: transmitting a first signal to a data network; receiving, in response to the first signal, a second signal from the data network, wherein the second signal identifies a Public Land Mobile Network (PLMN) configured to be accessed by the data network; and transmitting, via the data network, a Session Initiation Protocol (SIP) registration request to the PLMN. Brief Description of the Drawings

[0006] Figure 1 An exemplary network arrangement is shown in accordance with various exemplary embodiments.

[0007] Figure 2Illustrates an exemplary UE according to various exemplary embodiments.

[0008] Figure 3a Illustrates a signaling diagram of Session Initiation Protocol (SIP) signaling that can be used to establish a Mobile Originating (MO) call at a UE.

[0009] Figure 3b Illustrates a signaling diagram of SIP signaling that can be used to establish a Mobile Terminated (MT) call at a UE.

[0010] Figure 4 Illustrates a schematic overview of an exemplary arrangement of network functions configured to provide access to Public Land Mobile Network (PLMN) services to a UE when connected to a Standalone Non-Public Network (SNPN).

[0011] Figure 5 Illustrates a signaling diagram for providing access to a PLMN IP Multimedia Subsystem (IMS) to a UE according to various exemplary embodiments.

[0012] Figure 6 Illustrates a signaling diagram for providing access to a PLMN IMS to a UE according to various exemplary embodiments.

[0013] Figure 7 Illustrates a signaling diagram for providing access to a PLMN IMS to a UE via a Private Branch Exchange (PBX) according to various exemplary embodiments.

[0014] Figure 8 Illustrates a signaling diagram for providing access to a PLMN IMS to a UE only for emergency services according to various exemplary embodiments.

[0015] Figure 9 Illustrates a method for selecting a PLMN for an emergency call according to various exemplary embodiments. Detailed Description

[0016] The exemplary embodiments can be further understood with reference to the following description and the related drawings, in which like elements are provided with the same reference numerals. The exemplary embodiments relate to providing Public Land Mobile Network (PLMN) services to a User Equipment (UE) connected to a Standalone Non-Public Network (SNPN).

[0017] Throughout this description, the term "SNPN" generally refers to a non-public use deployment of a 5G system that does not rely on PLMN network functions. Thus, an SNPN can be configured to be utilized by a private entity and isolated from public access. Specific examples of the physical and virtual components that can be included in an SNPN will be described in detail below.

[0018] Exemplary embodiments are described with reference to a UE connected to an SNPN. A UE may represent any electronic component having hardware, software, and / or firmware that can establish a connection with a network and is configured to exchange information and data with the network. When operating in SNPN access mode, a UE may be configured to access one or more SNPNs. However, any reference to an SNPN, a UE, or SNPN access mode is provided for illustrative purposes only. Similar concepts may be referred to by different entities by different names.

[0019] A UE may be connected to both an SNPN and a PLMN simultaneously. For example, a UE may register with a PLMN via an SNPN (using the credentials of the PLMN). Thus, a UE may have access to both SNPN services and PLMN services. Exemplary embodiments are described with reference to providing Internet Protocol (IP) multimedia services and emergency services from a PLMN to a UE when connected to an SNPN. However, any reference to a UE accessing a particular type of PLMN service is provided for illustrative purposes only. Those skilled in the art will understand that the exemplary concepts described herein may be applicable to providing any type of PLMN service to a UE operating in SNPN access mode.

[0020] Figure 1 An exemplary network arrangement 100 according to various exemplary embodiments is shown. The exemplary network arrangement 100 includes a UE 110. Those skilled in the art will understand that the UE 110 may be any type of electronic component configured to communicate via a network, such as, for example, a mobile phone, a tablet computer, a desktop computer, a smart phone, a phablet, an embedded device, a wearable device, an Internet of Things (IoT) device, etc. It should also be understood that an actual network arrangement may include any number of UEs used by any number of users. Thus, for illustrative purposes, only an example with a single UE 110 is provided.

[0021] The UE 110 may be configured to communicate with one or more networks. In the example of network configuration 100, the networks with which the UE 110 may communicate wirelessly are an SNPN 112 and a PLMN 114. The SNPN 112 may be deployed by a private entity and isolated from the public network. However, as noted above, the UE 110 may access the PLMN 114 via the SNPN 112. Similarly, although outside the scope of the exemplary embodiments, a UE having credentials to access the SNPN 112 may be allowed to access the SNPN 112 via a public network (e.g., the PLMN 114).

[0022] UE 110 can wirelessly access the SNPN 112 via a 5G New Radio (NR) Radio Access Network (RAN) (5G NR RAN) 120. For example, the 5G NR RAN 120 can include one or more nodes, cells, or base stations (Node B, eNodeB, HeNB, eNBS, gNB, gNodeB, macro cell base station, micro cell base station, small cell base station, femto cell base station, etc.) configured to transmit and receive traffic from a UE equipped with an appropriate cellular chipset. However, it should be understood that the UE 110 can also access the SNPN 112 through a wired connection or using any other appropriate type of RAN. Thus, the UE 110 can include at least a 5G NR chipset to communicate with the 5G NR-RAN 120.

[0023] In the network arrangement 100, the UE 110 can be connected to the 5G NR RAN 120 via the node 120A. Those skilled in the art will understand that any relevant process can be performed for the UE 110 to connect to the 5G NR-RAN 120. For example, the UE 110 can be associated with a dedicated entity that deploys the SNPN 112. Thus, credentials can be supplied to the UE 110 to access the SNPN 112. When operating in the SNPN access mode, the UE 110 can be configured to search for and identify the nodes of the SNPN 112 (e.g., the node 120A). Upon detecting the presence of the 5G NR-RAN 120, the UE 110 can transmit the corresponding credential information to be associated with the 5G NR-RAN 120. More specifically, the UE 110 can be associated with a specific node (e.g., the node 120A of the 5G NR-RAN 120). The reference to one node and one RAN is provided for illustrative purposes only. Those skilled in the art will understand that the actual SNPN can include any appropriate number of RANs and corresponding nodes.

[0024] In addition to the 5G NR RAN 120, the SNPN 112 may further include an SNPN core network 130 and an SNPN IMS 135. The SNPN core network 130 may be regarded as an interconnected collection of components that manage the operations and traffic of a cellular network. The SNPN core network 130 also manages the traffic flowing between the cellular network and the data network 140. The SNPN IMS 135 may generally be described as an architecture for delivering multimedia services to the UE 110 using IP protocols. The SNPN IMS 135 may communicate with the SNPN core network 130 and the data network 140 to provide multimedia services to the UE 110. In some embodiments, the functionality described for the SNPN core network 130 and / or the SNPN IMS 135 may include cloud implementations, such as a collection of virtual servers or hardware servers hosting firmware. Exemplary embodiments are not limited to any particular network configuration and may be applicable to any suitable arrangement of hardware, software, and / or firmware.

[0025] The UE 110 may access network services from the PLMN 114 when connected to the SNPN 112. In some embodiments, this may include the UE 110 connecting to the PLMN 114 via the SNPN 112. For example, once registered with the SNPN core network 130, the UE 110 may utilize the SNPN 112 to perform non-3rd Generation Partnership Project (3GPP) access to the PLMN 114 via the data network 140. The UE 110 may then register with the PLMN 114 (using the credentials of the PLMN 114) and receive network services from the PLMN 114 via the SNPN 112. This functionality may be facilitated by various network functions on both the SNPN 112 side and the PLMN 114 side. The following will refer to Figure 4 the schematic overview 400 of Figures 5 to 8 and the signaling diagrams 500 - 800 of

[0026]

[0027] to describe in more detail specific examples of some of the core network functions that may be deployed by the SNPN 112 and the PLMN 114.

[0026] As described above, the data network 140 may be used to facilitate communication between the SNPN 112 and the PLMN 114. In this exemplary embodiment, the data network 140 may refer to the Internet. However, the reference to the Internet is provided for illustrative purposes only. Those skilled in the art will understand that the data network 140 may represent any suitable type of data network.

[0027] The PLMN 114 may represent a cellular network that can be deployed by a cellular provider (e.g., Verizon, AT&T, Sprint, T-Mobile, etc.) at a specific geographical location. The UE 110 is allowed to access the PLMN 114. For example, the UE 110 and / or the user of the UE may have contract and credential information (e.g., stored on a SIM card) to utilize the PLMN 114. In another example, the UE 110 may contract with a cellular provider that has an agreement with the cellular provider of the PLMN 114. Thus, in this type of scenario, a UE having a home PLMN with an agreement with the PLMN 114 may be allowed to utilize the PLMN 114. In another example, the UE 110 is allowed to utilize the PLMN 114 for emergency services. Thus, there are various different scenarios in which the UE 110 may be allowed to utilize the PLMN 114. Exemplary embodiments may be applicable to any scenario in which the UE 110 is configured to utilize the PLMN 114.

[0028] The UE 110 may directly access the PLMN 114 via the 5G NR RAN 160. For example, the 5G NR RAN 160 may include one or more nodes, cells, or base stations (Node B, eNodeB, HeNB, eNBS, gNB, gNodeB, macro base station, micro base station, small cell base station, femto base station, etc.) configured to send and receive traffic from a UE equipped with an appropriate cellular chipset. Upon detecting the presence of the 5G NR-RAN 160, the UE 110 may transmit corresponding credential information in order to associate with the 5G NR RAN 160. More specifically, the UE 110 may associate with a specific node (not shown) of the 5G NR RAN 160. However, the reference to one RAN is provided for illustrative purposes only. Those skilled in the art will understand that an actual PLMN may include any suitable number of RANs and corresponding nodes.

[0029] As described above, the UE 110 may access the PLMN 114 via the SNPN 112 or directly via the 5G NR RAN 160. However, it should be understood that the UE 110 may also access the PLMN 114 through a wired connection or using any other suitable type of RAN. Thus, the UE 110 may include at least a 5G NR chipset to communicate with the 5G NR-RAN 160.

[0030] In addition to the 5G NR RAN 160, the PLMN 114 may include a PLMN core network 150 and a PLMN IMS 155. The PLMN core network 150 may be regarded as an interconnected set of components that manage the operations and traffic of a cellular network. The PLMN core network 150 also manages the traffic flowing between the cellular network and the data network 140. Those skilled in the art will understand that in an actual network deployment, the PLMN 114 may share the core network with other PLMNs.

[0031] As described above, the UE 110 may receive network services from the PLMN 114 via the SNPN 112. This functionality may be facilitated by various network functions on both the SNPN 112 side and the PLMN 114 side. The following will refer to Figure 4 schematic overview 400 of Figures 5 to 8 and signaling diagrams 500 - 800 of

[0032] to describe in more detail specific examples of some of the core network functions that may be deployed by the SNPN 112 and the PLMN 114.

[0033] Figure 2 An exemplary UE 110 is shown in accordance with various exemplary embodiments. The UE 110 will be described with reference to Figure 1 network arrangement 100 of

[0034] The processor 205 may be configured to execute multiple engines of the UE 110. For example, the engines may include the PLMN support 235 for the SNPN access mode engine. The PLMN support 235 for the SNPN access mode engine may perform various operations related to registering with the PLMN and receiving network services from the PLMN when the UE 110 is operating in the SNPN access mode.

[0035] The above engines are merely exemplary as applications (e.g., programs) executed by the processor 205. The functions associated with the engines may also be represented as separate integrated components of the UE 110, or may be modular components coupled to the UE 110, e.g., integrated circuits with or without firmware. For example, an integrated circuit may include an input circuit for receiving signals and a processing circuit for processing the signals and other information. The engines may also be embodied as one application or multiple separate applications. Additionally, in some UEs, the functionality described for the processor 205 is divided among two or more processors such as a baseband processor and an application processor. The exemplary embodiments may be implemented in any of these or other configurations of the UE.

[0036] The memory 210 may be a hardware component configured to store data related to operations performed by the UE 110. The display device 215 may be a hardware component configured to display data to the user, while the I / O device 220 may be a hardware component that enables the user to make inputs. The display device 215 and the I / O device 220 may be separate components or may be integrated together (such as a touch screen). The transceiver 225 may be a hardware component configured to establish connections with the 5G NR RAN 120, 5G NR RAN 160. Thus, the transceiver 225 may operate at various different frequencies or channels (e.g., a set of contiguous frequencies).

[0037] The exemplary embodiments include mechanisms for providing PLMN services to the UE 110 when connected to the SNPN 112. In a first aspect, the exemplary embodiments relate to implementing a Uniform Resource Identifier (URI) format that is used to transmit a SIP invitation / receive a SIP invitation from a UE connected to the SNPN during Session Initiation Protocol (SIP) signaling. The exemplary URI format and examples for using the exemplary URI format for mobile-originated (MO) calls and mobile-terminated (MT) calls with the UE 110 in the SNPN access mode will be described in more detail below. However, the exemplary embodiments do not need to utilize the exemplary URI format described below and may utilize any suitable URI format.

[0038] Those skilled in the art will understand that SIP generally refers to a signaling protocol that can be used to establish and maintain an IP multimedia communication session between two remote endpoints. For example, SIP signaling can be used to create a communication session between UE 110 and another UE (or any other type of remote endpoint). This communication session can then be used to exchange multimedia data (e.g., voice calls, video calls, etc.).

[0039] Figure 3a A signaling diagram 300 of SIP signaling that can be used to establish an MO call at UE 110 is shown. Signaling diagram 300 includes UE 110, SNPN 112, PLMN 114, PLMN IMS 155, and another UE 302.

[0040] In 305, UE 110 registers with SNPN 112. For example, UE 110 may camp on node 120A of 5G NR RAN 120. When camping, UE 110 and SNPN 112 may participate in a signaling exchange to register UE 110 with SNPN 112 and establish an appropriate context within SNPN core network 130.

[0041] In step 310, UE 110 registers with PLMN 114. For example, once registered with SNPN 112, UE 110 can access PLMN 114 via SNPN 112 and data network 140. UE 110 and PLMN 114 may participate in a signaling exchange to register UE 110 with PLMN 114 and establish an appropriate context within PLMN core network 150. This may also include registering UE 110 with PLMN IMS 155. Thus, at this time, PLMN IMS 155 is aware that UE 110 is connected to SNPN 112 or has access to this information at least via PLMN core network 150.

[0042] In 315, UE 110 initiates an MO call. For example, in response to user input at UE 110, UE 110 may initiate SIP signaling for an MO call. In another example, UE 110 may be equipped with sensors that trigger UE 110 to automatically initiate SIP signaling for an MO call when certain conditions exist.

[0043] In 320, UE 110 transmits a SIP invitation to another UE 302. Since PLMN 114 is facilitating voice services, the SIP invitation can be routed to another UE 302 via PLMN IMS 155. The SIP invitation can utilize the following exemplary URI format: sip:device_id@ims.mnc(SNPN).mnc(PLMN).mcc(PLMN).3gppnetwork.org. The "sip:" part is conventionally used for SIP signaling. The "device_id" part can represent any suitable identifier of the MT device (e.g., username, Subscription Permanent Identifier (SUPI), International Mobile Subscriber Identity (IMSI), Temporary MSI (TMSI), IP Multimedia Private Identity (IMPI), etc.). The ".mnc(SNPN)" part refers to the Mobile Network Code (MNC) of SNPN 112. Similarly, the ".mnc(PLMN)" part refers to the MNC of PLMN 114, and the ".mcc(PLMN)" part refers to the Mobile Country Code (MCC) of PLMN 114. The ".3gppnetwork" part indicates the involvement of a 3GPP network (e.g., PLMN 114). Thus, the exemplary URI format can indicate to PLMN IMS 155 that the MO call originates from an endpoint of SNPN 112.

[0044] In 325, PLMN IMS 155 modifies the SIP invitation. For example, PLMN IMS 155 may be responsible for the mapping between SNPN 112 and PLMN 114. However, while the exemplary URI format can be used for SNPN, the exemplary URI format may not be allowed for PLMN 114. Thus, PLMN IMS 155 can modify the SIP invitation received from UE 110 from the exemplary URI format to the 3GPP standard SIP URI format so that the SIP invitation can be sent to another UE 302 via PLMN 114. Thus, PLMN IMS 155 can modify the SIP invitation from the first URI format to the second URI format based on the target endpoint (e.g., UE 305).

[0045] The following is an example of a URI according to the 3GPP standard format: sip:device_id@ims.mnc(PLMN).mcc(PLMN).3gppnetwork.org. Thus, PLMN IMS 155 can change the URI format of the SIP invitation to the 3GPP standard URI format. In this example, PLMN IMS 155 can modify the SIP invitation by removing or modifying the SNPN ID (MNC part).

[0046] In 330, the PLMN IMS 155 forwards the SIP invitation to the UE 302. Those skilled in the art will understand that other SIP signaling may occur to establish a communication session between the UE 110 and the UE 302.

[0047] Figure 3b A signaling diagram 350 of SIP signaling that can be used to establish an MT call at the UE 110 is shown. The signaling diagram 350 includes the UE 110, the SNPN 112, the PLMN 114, the PLMN IMS 155, and another UE 302.

[0048] In 355, the UE 110 registers with the SNPN 112. In 360, the UE 110 registers with the PLMN 114. 355 - 360 is substantially similar to 305 - 310 of the signaling diagram 300.

[0049] In 365, another UE 302 initiates a MO call. For example, in response to user input at the other UE 302, the UE 302 may initiate SIP signaling for the MO call.

[0050] In 370, the other UE 302 transmits a SIP invitation to the UE 110. Since the PLMN 114 is facilitating the voice call, the SIP invitation can be routed to the UE 110 via the PLMN IMS 155. This SIP invitation may utilize the 3GPP standard URI (sip:device_id@ims.mnc(PLMN).mcc(PLMN).3gppnetwork.org) because the SIP invitation originates from the UE 302 that is not connected to the SNPN 112. Thus, the PLMN IMS 155 knows the SIP invitation that originates from a UE (e.g., the other UE 302) that is not connected to the SNPN 112.

[0051] At 375, the PLMN IMS 155 modifies the SIP invitation. For example, the PLMN IMS 155 can modify the standard 3GPP URI format to an exemplary URI format: sip:device_id@ims.mnc(SNPN).mnc(PLMN).mcc(PLMN).3gppnetwork. In the example of signaling diagram 300, the PLMN IMS 155 modifies the SIP invitation by removing the SNPN ID (MNC part) from the SIP sent in the exemplary URI format to conform to the 3GPP standard format. In this example, the PLMN IMS 155 modifies the SIP invitation received in the 3GPP standard URI format by adding the SNPN ID (MNC part) to create a SIP invitation that conforms to the exemplary URI format. Thus, the PLMN IMS 155 can modify the SIP invitation from a first URI format to a second URI format based on the target endpoint (e.g., UE 110).

[0052] At 380, the PLMN IMS 155 forwards the SIP invitation to the UE 110. Those skilled in the art will understand that other SIP signaling may occur to establish a communication session between the UE 110 and the UE 302.

[0053] Signaling diagrams 300 and 350 describe modifying the SIP invitation by adding or removing the SNPN ID (MNC part) of the SIP invitation. However, the specific exemplary URI form and the way of modifying the SIP invitation are provided only for illustrative purposes. The exemplary concepts described herein, where the PLMN IMS 155 modifies the SIP invitation and then transmits the SIP invitation via the SNPN 112 or the PLMN 114, can be applied to any scenario where the SNPN implements a URI format different from the URI format utilized by the PLMN.

[0054] In a second aspect, an exemplary embodiment relates to providing PLMN services to the UE 110 when connected to the SNPN 112. To facilitate this functionality, various network functions on the SNPN 112 side and the PLMN 114 side can work together. Specific examples are described below Figures 4 to 8 using the schematic overview 400 and signaling diagrams 500 - 800. However, throughout this description, any reference to a specific communication interface or network function that performs a particular type of task on the SNPN 112 side or the PLMN 114 side is provided only for illustrative purposes. Similar concepts may be referred to by different entities by different names.

[0055] Figure 4Schematic overview 400 shows an exemplary arrangement of network functions configured to provide access to PLMN services to UE 110 when connected to SNPN 112. Schematic overview 400 will be described with reference to Figure 1 network arrangement 100 of Figure 2 and UE 110 of

[0056] Similar to network arrangement 100, schematic overview shows SNPN 112 and PLMN 114. In this example, the SNPN112 side includes UE 110, 5G NR RAN 120, SNPN Access and Mobility Management (AMF) 405, SNPN Session Management Function (SMF) 410, SNPN User Plane Function (UPF) 415, and SNPN IMS 135.

[0057] UE 110 can be connected to 5G NR RAN 120. Both UE 110 and 5G NR RAN 120 can communicate directly with AMF 405. For example, UE 110 can communicate with SNPN AMF 405 through the N1 interface, and 5G NR RAN 120 can communicate with SNPN AMF 405 through the N2 interface.

[0058] SNPN AMF 405 can perform operations related to mobility management, such as but not limited to paging, non-access stratum (NAS) management, and registration process management between UE110 and the SNPN core network 130. SNPN AMF 405 can be equipped with one or more communication interfaces (e.g., N1, N2, etc.) to communicate directly or indirectly with other internal and external network components (e.g., network functions, RAN, UE, etc.). The exemplary embodiments are not limited to the AMF performing the above operations. Those skilled in the art will understand the various different types of operations that the AMF can perform. In addition, the reference to a single SNPN AMF 405 is for illustrative purposes only, and the actual network arrangement may include any appropriate number of AMFs.

[0059] SNPN AMF 405 can also communicate directly with SNPN SMF 410. For example, SNPN AMF405 can communicate with SNPN SMF 410 through the N11 interface.

[0060] The SNPN SMF 410 can perform operations related to session management, such as but not limited to session establishment, session release, IP address allocation, policy and quality of service (QoS) implementation, etc. The SNPN SMF 410 can be equipped with one or more communication interfaces (e.g., N11, etc.) to communicate directly or indirectly with other internal and external network components (e.g., network functions, RAN, UE, etc.). Exemplary embodiments are not limited to the SMF that performs the above operations. Those skilled in the art will understand the various different types of operations that the SMF can perform. In addition, the reference to a single SNPN SMF 410 is for illustrative purposes only, and the actual network arrangement may include any appropriate number of SMFs.

[0061] The SNPN SMF 410, 5G NR RAN 120, and SNPN IMS 135 can communicate directly with the SNPN UPF 415. For example, the SNPN SMF 410 can communicate with the SNPN UPF 415 through the N4 interface, the 5G NR RAN 120 can communicate with the SNPN UPF 415 through the N3 interface, and the SNPN IMS 135 can communicate with the SNPN UPF 415 through the N6 interface.

[0062] The SNPN UPF 415 performs operations related to packet data unit (PDU) session management. For example, the SNPN UPF 415 can facilitate the connection between the UE 110 and the data network 140 (e.g., the Internet) via the N6 interface. The SNPN UPF 415 can be equipped with one or more communication interfaces (e.g., N3, N4, N6, etc.) to communicate directly or indirectly with other internal and external network components (e.g., network functions, RAN, UE, etc.). Exemplary embodiments are not limited to the UPF that performs the above operations. Those skilled in the art will understand the various different types of operations that the UPF can perform. In addition, the reference to a single SNPN UPF 415 is for illustrative purposes only, and the actual network arrangement may include any appropriate number of UPFs.

[0063] The PLMN 114 side can include a non-3GPP interworking function (N3IWF) 420, a PLMN UPF 425, and a PLMN IMS 155. The PLMN UPF 425 performs operations substantially similar to those of the SNPN UPF 415. In this example, the PLMN UPF 425 can communicate directly with the N3IWF 210 via the N3 interface and directly with the PLMN IMS 155 via the N6 interface. However, the reference to a single PLMN UPF 425 is for illustrative purposes only, and the actual network arrangement may include any appropriate number of UPFs.

[0064] The N3IWF 420 can perform operations related to providing non-3GPP access to the PLMN core network 150. For example, the N3IWF 420 can authenticate a UE attempting to access the PLMN 114 via the data network 140 without using a network based on 3GPP standards. In this example, the N3IWF 420 is connected to the data network 140 via the N6 interface. Exemplary embodiments are not limited to the N3IWF performing the above-referenced operations. Those skilled in the art will understand the various different types of operations that the N3IWF can perform. Additionally, the reference to a single N3IWF 420 is for illustrative purposes only, and an actual network arrangement may include any suitable number of N3IWFs.

[0065] As described above, the SNPN 112 can interact with the PLMN 114 via the Internet (or any other suitable type of data network). The following will refer to Figure 4 the schematic overview 400 of Figures 5 to 8 and the signaling diagrams 500 - 800 of

[0066] Figure 5 to describe in more detail specific examples of how the network functions on the SNPN 112 side and the PLMN 114 can interact with each other to provide PLMN services to the UE 110 when connected to the SNPN 112. Figure 1 the network arrangement 100 of Figure 2 the UE 110 of Figure 4 and the schematic overview 400 of

[0067] The signaling diagram 500 relates to the UE 110 establishing a persistent connection with the PLMN IMS 155 via the N3IWF 420. Once connected, the UE 110 can access the PLMN IMS 155, and for external access to the PLMN 114, the UE 110 is also reachable. Thus, the signaling diagram 500 shows how the UE 110 can establish a connection via the SNPN 112 that enables the UE 110 to receive PLMN services (e.g., IP multimedia services, emergency services, etc.).

[0068] The signaling diagram 500 includes a UE 110, an SNPN AMF 405, a data network 140, an N3IWF 420, and a PLMN IMS 155. At 505, the UE 110 transmits a registration request to the SNPN AMF 405. For example, after the UE 110 camps on the 5G NR RAN 120, the UE 110 may register with the SNPN AMF 405 to receive various services from the SNPN 112. The registration request may indicate that the UE 110 is interested in being configured to access services (such as IMS) from an internal network (SNPN) or an external public network (e.g., PLMN 114).

[0069] At 510, the SNPN AMF 405 transmits a registration acceptance message to the UE 110. The registration acceptance message may indicate to the UE 110 that the SNPN 112 supports IP multimedia services (such as voice calls, video calls, etc.) and / or emergency services only from an external public network. Once registered with the SNPN AMF 405, the UE 110 can access the data network 140. For example, in the context of the schematic overview 400, the SNPN AMF 140 may indirectly access the data network 140 via the SNPN SMF 410 and the SNPN UPF 415. However, at this time, the UE 110 is not aware of the existence of the PLMN 114.

[0070] At 515, the UE 110 may query the data network 140 for 3GPP cellular network information. For example, the UE 110 may transmit an Access Network Query Protocol (ANQP) signal to the data network 140. At 520, the UE 110 may receive a response from the data network 140. For example, in response to the ANQP query, the UE 110 may receive an ANQP response indicating that it may be able to access the PLMN 114 via the data network 140 and the N3IWF 420. This indication may include information (such as the IP address of the N3IWF420, PLMN accessible) that allows the UE 110 to signal the PLMN 114. Thus, the exemplary embodiment involves using the ANQP query concept for N3IWF access.

[0071] At 525, the UE 110 and the PLMN 114 may participate in a signaling exchange for Internet Key Exchange (IKE) authentication and registration. This may be similar to the IKE authentication and registration performed via non-3GPP access during network registration. Here, the SNPN 112 may represent a non-3GPP access network.

[0072] In signaling diagram 500, UE 110 is shown performing this signaling exchange 525 using N3IWF 420. However, those skilled in the art will understand that similar to the IKE authentication and registration process performed via non-3GPP access during network registration, the signaling exchange in 525 may also involve other network functions on the PLMN 114 side, such as AMF and Authentication Server Function (AUSF). After the IKE authentication and registration process is successfully completed, UE 110 may connect to N3IWF via SNPN 112.

[0073] In 530, UE 110 may transmit a SIP registration request to PLMN IMS 155. The SIP registration request may reach PLMN IMS 155 via the connection with N3IWF 420. Additionally, the SIP registration request may be sent using the IP address assigned to UE 110 during SNPN registration, and thus, it may not be necessary to create a new PDU session to access PLMN IMS 155.

[0074] In 535, UE 110 establishes a connection with PLMN IMS 155. For example, the registration process initiated by the SIP registration request may be successfully completed based on the signaling exchange between UE 110 and PLMN IMS155. This registration process may be similar to the registration procedure for voice via non-3GPP access. However, in this example, 530 and 535 are shown separately to emphasize that an advantage of the exemplary embodiment is that it may not be necessary to create a new PDU session to transmit the SIP registration request to PLMN IMS 155.

[0075] In the context of the schematic overview 400, SNPN UPF 415 is shown connecting the SNPN 112 network component to the data network 140. Thus, those skilled in the art will understand that since the signaling shown in 515 - 535 flows out of SNPN 112 to the data network 140 and / or PLMN 114, 515 - 535 may include user plane signaling.

[0076] As described above, once connected using signaling diagram 500, UE 110 can access PLMN IMS 155, and PLMNIMS 155 can signal UE 110. Thus, UE 110 can now receive PLMN services (e.g., IP multimedia services, emergency services, etc.) via SNPN112.

[0077] Figure 6 A signaling diagram 600 for providing access to PLMN IMS 155 to UE 110 is shown according to various exemplary embodiments. Reference will be made to Figure 1 the network arrangement 100, Figure 2UE 110 and Figure 4 A schematic overview 400 to describe signaling diagram 600.

[0078] Signaling diagram 600 involves the UE 110 establishing internal IMS access (e.g., SNPN IMS 135) and external IMS access (e.g., PLMN IMS 155). This enables the UE 110 to make calls to UEs connected to the SNPN 112 and UEs connected to the PLMN 114.

[0079] Signaling diagram 600 includes UE 110, SNPN AMF 405, SNPN IMS 135, data network 140, N3IWF 420, and PLMN IMS 155. At 605, the UE 110 transmits a registration request to the SNPN AMF 405. For example, after the UE 110 camps on the 5GNR RAN 120, the UE 110 can register with the SNPN AMF 405 to receive various services from the SNPN 112. The registration request can indicate that the UE 110 is interested in being configured to access services from the internal network and / or an external public network (e.g., PLMN 114).

[0080] At 610, the SNPN AMF 405 transmits a registration acceptance message to the UE 110. The registration acceptance message can indicate to the UE 110 that the SNPN 112 supports both: i) internal IMS and / or emergency services, and ii) external IMS and / or emergency services. This is contrary to the example shown in signaling diagram 500, where only external IMS and / or emergency services were indicated in the registration acceptance message.

[0081] At 615, the UE 110 performs a SIP registration with the SNPN IMS 135. Once registered, the UE 110 can have IMS access with other UEs within the SNPN 112.

[0082] At 620, the UE 110 can query the data network 140 for 3GPP cellular network information. For example, the UE 110 can transmit an Access Network Query Protocol (ANQP) signal to the data network 140. At 625, the UE 110 can receive a response from the data network 140. For example, in response to the ANQP query, the UE 110 can receive an ANQP response indicating that it may be able to access the PLMN 114 via the data network 140 and the N3IWF 420. This indication can include information (e.g., the IP address of the N3IWF 420) that allows the UE 110 to signal the PLMN 114.

[0083] In 630, the UE 110 and the N3IWF 420 may participate in a signaling exchange for IKE authentication and registration. This is substantially similar to 525 of signaling diagram 500. In 635, the UE 110 and the PLMN IMS 155 perform SIP registration. At this time, the UE 110 is now configured with a dual IMS registration, for example, the SNPN IMS 135 and the PLMN IMS 155.

[0084] In 640, a SIP invitation corresponding to a call is transmitted. The priority of the call may be configured for an internal network (e.g., the SNPN 112), and thus the SIP invitation may be sent to the SNPN IMS 135 for routing. In this example, the SIP invitation is addressed to an external network device, such as a UE pre-empted on the PLMN 114. In 645, the SNPN IMS 135 transmits a SIP response to the UE 110. In this example, since the call is directed towards an external network device, the SIP response may have a SIP response code of "380 Alternate Service". Conventionally, this SIP response code is used by a SIP server to indicate that the SIP server cannot or is unable to connect the call as required, but an alternate service is possible. Thus, the exemplary embodiment involves utilizing this type of SIP response to indicate to the UE 110 that the external SIP registration (e.g., 635) applies to the SIP invitation.

[0085] In 650, the UE 110 transmits a SIP invitation to the PLMN IMS 155 for routing. Thus, in response to receiving the SIP response in 645, the UE 110 transmits a new SIP request to the external network. Subsequently, the SIP invitation will be routed to the intended endpoint, such as another UE pre-empted on the PLMN 114, and a communication session may be established.

[0086] Figure 7 A signaling diagram 700 is shown for providing access to the PLMN IMS 155 to the UE 110 via a private branch exchange (PBX) 702 according to various exemplary embodiments. Reference will be made to Figure 1 the network arrangement 100 of Figure 2 the UE 110 of Figure 4 and the schematic overview 400 of

[0087] The signaling diagram 700 relates to the SNPN 112 equipped with a PBX 702. Those skilled in the art will understand that the PBX 702 generally may refer to a private telephone network. The PBX 702 can use extensions to make calls within the private telephone network or to an external public network. The PBX 702 can be integrated into the SNPN 112 using a server locally hosted by a private entity deploying the SNPN 112 or using a cloud implementation such as a set of virtual or hardware servers hosting firmware.

[0088] The signaling diagram 700 includes a UE 110, an SNPN 112, a PBX 702, a data network 140, and a PLMN IMS 155. At 705, the UE 110 registers with the SNPN 112 which may include being assigned an IP address.

[0089] At 710, the PBX 702 can query the data network 140 for 3GPP cellular network information. For example, the PBX 702 can transmit an ANQP signal to the data network 140. At 715, the PBX 702 can receive a response from the data network 140. For example, in response to the ANQP query, the PBX 702 can receive an ANQP response indicating that it may be possible to access the PLMN 114 via the data network 140 and the N3IWF 420. This indication may include information (e.g., the IP address of the N3IWF 420) that allows the UE 110 to signal the PLMN 114.

[0090] At 720, the PBX 702 and the PLMN IMS 155 can perform a SIP registration. For example, using the information received in the ANQP response, the PBX 702 can initiate a SIP registration. Thus, the exemplary embodiment involves using the ANQP query concept to enable the PBX to perform a SIP registration with an external IMS.

[0091] In this type of scenario, the UE 110 does not have a directly available link to the PLMN 114. Therefore, in order to make a call to an external network device, the UE 110 may have to go through the PBX 702.

[0092] At 725, the UE 110 transmits a call setup request to the PBX 702. This request can indicate to the PBX 702 that the UE 110 wants to establish a communication channel with another UE not within the SNPN 112. At 730, the PBX 702 can transmit a SIP invitation to the PLMN IMS 155 to establish a communication session for the UE 110. Thus, the UE 110 can receive on-demand services from the external PLMN 114 via the PBX 702.

[0093] In addition, in this type of scenario, the SIP invitation for an MT call at the UE 110 will go through the PBX 702. This is shown by the SIP invitation in 735. It should be noted that the SIP invitation 730 is for an MO call made by the UE 110, and the SIP invitation 735 is for an MT call at the UE 110. These SIP invitations are not related and are only provided to demonstrate the functionality of the PBX 702 for MO calls and MT calls.

[0094] Once the PBX 702 receives the SIP invitation 735, for the external device to reach the UE 110, the external device may also have to provide additional information, such as dual-tone multi-frequency (DTMF) associated with the UE 110 (e.g., extension). Thus, in 740, the PBX 702 receives the DTMF associated with the UE 110. In 745, the PBX 702 forwards the SIP invitation to the UE 110 based on the received DTMF.

[0095] Figure 8 A signaling diagram 800 for providing access to the PLMN IMS 155 to the UE 110 only for emergency services is shown according to various exemplary embodiments. It will be described with reference to Figure 1 the network arrangement 100, Figure 2 the UE 110, and Figure 4 the schematic overview 400.

[0096] The signaling diagram 800 pertains to providing access to the PLMN 114 for only emergency calls. The signaling diagram 800 includes the UE 110, SNPN AMF 405, SNPN IMS 135, data network 140, N3IWF 420, and PLMN IMS 155.

[0097] In 805, the UE 110 transmits a registration request to the SNPN AMF 405. For example, after the UE 110 camps on the 5G NR RAN 120, the UE 110 may register with the SNPN AMF 405 to receive various services from the SNPN 112. The registration request may indicate that the UE 110 is interested in being configured to access services from an external public network (e.g., PLMN 114).

[0098] In 810, the SNPN AMF 405 transmits a registration acceptance message to the UE 110. The registration acceptance message may indicate to the UE 110 that the SNPN 112 supports emergency services from an external public network.

[0099] In 815, the UE 110 performs a SIP registration with the SNPN IMS 135. Once registered, the UE 110 can access other UEs within the SNPN 112.

[0100] In 820, the UE 110 may query the data network 140 for 3GPP cellular network information. For example, the UE 110 may transmit an ANQP signal to the data network 140. In 825, the UE 110 may receive a response from the data network 140. For example, in response to the ANQP query, the UE 110 may receive an ANQP response indicating that it may be able to access the PLMN 114 via the data network 140 and the N3IWF 420. This indication may include information (e.g., the IP address of the N3IWF 420) that allows the UE 110 to signal the PLMN 114. At this point, the UE 110 now knows how to contact the PLMN IMS 155 for an emergency call. However, since only emergency services are supported, there is no continuous link between the UE 110 and the PLMN 114 as in the signaling diagrams 500 - 600.

[0101] In 830, the UE 110 transmits an emergency SIP invitation. Since there is no continuous link to the external PLMN 114, the emergency invitation is routed to the SNPN IMS 155. In 835, the SNPN IMS 155 transmits a SIP response to the UE 110. For example, the SIP response may have a SIP response code indicating a 380 alternative service that should use an external SIP registration for the call.

[0102] In 840, the UE 110 and the N3IWF 420 may participate in a signaling exchange for IKE authentication and registration. The UE 110 knows how to contact the N3IWF 420 based on the ANQP query and response in 820 - 825.

[0103] In 845, the UE 110 transmits a SIP SoS registration request to the PLMN IMS 155. Thus, the UE 110 is able to make an emergency call via the PLMN 114 when connected to the SNPN 112.

[0104] Figure 9 A method 900 for selecting a PLMN for an emergency call according to various exemplary embodiments is shown.

[0105] As described above, the UE 110 may access PLMN services via the SNPN 112 or via a direct connection to the currently camped PLMN. The method 900 relates to how the UE 110 in the SNPN access mode may select a PLMN for an emergency call.

[0106] In 905, an emergency call is initiated. For example, in response to user input at UE 110, UE 110 may initiate SIP signaling for an emergency call. In another example, UE 110 may be equipped with sensors that trigger UE 110 to automatically initiate SIP signaling for an emergency call when certain conditions exist. Exemplary embodiments are applicable to initiating an emergency call for any suitable reason.

[0107] In 910, UE 110 determines to register UE 110 with an external IMS. For example, as described above with reference to signaling diagrams 500 - 800, UE 110 may be registered to utilize PLMN IMS 155 when connected to SNPN 112. If UE 110 is registered to utilize an external IMS, method 900 continues to 915. In 915, UE 110 routes the emergency call to the external IMS. Subsequently, method 900 ends.

[0108] If UE 110 is not registered to utilize an external IMS, method 900 continues to 920. In 920, UE 110 determines whether one or more whitelisted PLMNs are available. For example, the operator of UE 110 may configure UE 110 to access an authorization server. Those skilled in the art will understand that an authorization server generally refers to a network component that is configured to indicate to UE 110 which PLMNs the operator of the PLMN is authorized to use. These PLMNs may be referred to as whitelisted PLMNs. Thus, since UE 110 is in SNPN access mode and there is no external IMS available via the SNPN, UE 110 may search for PLMNs to preempt.

[0109] In some embodiments, the identity of the whitelisted PLMNs may have been supplied to UE 110 before the emergency call is initiated. In other embodiments, UE 110 may query the authorization server after the emergency call is initiated. If UE 110 is not configured with any whitelisted PLMNs, method 900 continues to 925. Similarly, if UE 110 determines the identity of one or more whitelisted PLMNs, but UE 110 cannot detect any of the whitelisted PLMNs in the PLMN search, method 900 continues to 925.

[0110] In 925, the UE 110 routes an emergency call via any available PLMN. For example, when the UE 110 cannot detect a PLMN that the UE 110 is authorized by the UE's operator to utilize, the UE 110 may be in limited service. When in limited service, the UE 110 may not be allowed to access the available PLMNs for most services. However, the UE 110 may be allowed to access at least one PLMN in the PLMNs for emergency calls. Thus, in 925, the UE 110 may exhibit normal behavior of the UE while in limited service and attempt to route an emergency call via any appropriate available PLMN.

[0111] Returning to 920, if the UE 110 determines that a whitelisted PLMN is available, method 900 may proceed to 930. At this time, the UE 110 camps on the PLMN that the UE 110 is authorized by the UE's operator to utilize. Thus, in 930, the UE 110 may route an emergency call via the currently camped-on whitelisted PLMN. Subsequently, method 900 ends.

[0112] Those skilled in the art will understand that the above-described exemplary embodiments can be implemented in any suitable software configuration or hardware configuration or a combination thereof. An exemplary hardware platform for implementing the exemplary embodiments may include, for example, an Intel x86-based platform with a compatible operating system, Windows OS, Mac platform, and MAC OS, and mobile devices with operating systems such as iOS, Android, etc. In other examples, the exemplary embodiments of the above methods may be embodied as a program including lines of code stored on a non-transitory computer-readable storage medium, which, when compiled, can be executed on a processor or a microprocessor.

[0113] Although this patent application describes various combinations of various embodiments each having different features, those skilled in the art will understand that any feature of one embodiment can be combined with the features of other embodiments in any manner not negated by the disclosure or features that are not functionally or logically inconsistent with the operation of the devices of the embodiments disclosed in the present invention or the described functions.

[0114] It is well known that the use of personally identifiable information should follow privacy policies and practices that are recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of inadvertent or unauthorized access or use, and the nature of the authorized use should be clearly explained to the user.

[0115] It will be apparent to those skilled in the art that various modifications can be made to the present disclosure without departing from the essence or scope of the present disclosure. Accordingly, the present disclosure is intended to cover modifications and variations of the present disclosure, provided that these modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. A method for providing public land mobile network support, comprising: at a user equipment (UE) registered to a Standalone Non-Public Network (SNPN): transmitting a first signal to a data network; receiving a second signal from the data network in response to the first signal, wherein the second signal identifies a Public Land Mobile Network (PLMN) configured to be accessed by the UE via the data network; transmitting a Session Initiation Protocol (SIP) registration request to the PLMN via the data network using an Internet Protocol (IP) address assigned to the UE during the registration process to the SNPN; establishing a connection with the Internet Protocol (IP) Multimedia Subsystem (IMS) of the SNPN using the Internet IP address assigned to the UE; and establishing a connection with the IMS of the PLMN, wherein the UE registers to the IMS of the SNPN and the IMS of the PLMN simultaneously.

2. The method according to claim 1, wherein the first signal and the second signal comply with the Access Network Query Protocol (ANQP).

3. The method according to claim 1, wherein the first signal further identifies a Non-3rd Generation Partnership Project (3GPP) Networking Function (N3IWF) of the PLMN.

4. The method according to claim 1, further comprising: establishing a connection with the Internet Protocol (IP) Multimedia Subsystem (IMS) of the PLMN, wherein the UE is configured with voice services via the IMS of the PLMN.

5. The method according to claim 1, further comprising: transmitting a first SIP invitation to the IMS of the SNPN; receiving a SIP response from the IMS of the SNPN; and transmitting a second SIP invitation to the IMS of the PLMN based on receiving the SIP response from the IMS of the SNPN.

6. The method according to claim 5, wherein the SIP response from the IMS of the SNPN includes a 380 Alternate Service SIP response code.

7. The method according to claim 1, wherein the SIP registration request is for emergency services.

8. The method according to claim 7, further comprising: establishing a connection with the Internet Protocol (IP) Multimedia Subsystem (IMS) of the SNPN before transmitting the SIP registration request; transmitting a SIP invitation to the IMS of the SNPN; and receiving a SIP response from the IMS of the SNPN, wherein the SIP registration request is transmitted to the PLMN based on the SIP response received from the IMS of the SNPN.

9. A user equipment (UE), comprising: a transceiver configured to communicate with one or more networks; and a processor configured to perform operations, the operations including: registering to a Standalone Non-Public Network (SNPN); transmitting a first signal to a data network via the SNPN; receiving a second signal from the data network in response to the first signal, wherein the second signal identifies a Public Land Mobile Network (PLMN) configured to be accessed via the data network; Transmit a Session Initiation Protocol (SIP) registration request to the Public Land Mobile Network (PLMN) via the data network using the Internet Protocol (IP) address assigned to the UE during the registration process with the SNPN. Establish a connection with the IP Multimedia Subsystem (IMS) of the SNPN using the Internet IP address assigned to the UE; and Establish a connection with the IMS of the PLMN, wherein the UE registers with both the IMS of the SNPN and the IMS of the PLMN simultaneously.

10. The UE according to claim 9, the operation further comprises: Establish a connection with the IP Multimedia Subsystem (IMS) of the PLMN, wherein the UE is configured with voice services via the IMS of the PLMN.

11. The UE according to claim 9, the operation further comprises: Transmit a first SIP invitation to the IMS of the SNPN; Receive a SIP response from the IMS of the SNPN; and Based on receiving the SIP response from the IMS of the SNPN, transmit a second SIP invitation to the IMS of the PLMN.

12. The UE according to claim 11, wherein the SIP response from the IMS of the SNPN includes a 380 Alternate Service SIP response code.

13. The UE according to claim 9, wherein the SIP registration request is for emergency services.

14. The UE according to claim 13, the operation further comprises: Establish a connection with the IP Multimedia Subsystem (IMS) of the SNPN before transmitting the SIP registration request; Transmit a SIP invitation to the IMS of the SNPN; and Receive a SIP response from the IMS of the SNPN, wherein the SIP registration request is transmitted to the PLMN based on the SIP response received from the IMS of the SNPN.

15. A method for providing Public Land Mobile Network support, comprises: At a private branch exchange of an Independent Non-Public Network (SNPN): Transmit a first signal to the data network; In response to the first signal, receive a second signal from the data network, wherein the second signal identifies a Public Land Mobile Network (PLMN) configured to be accessed via the data network; and Transmit a Session Initiation Protocol (SIP) registration request to the PLMN via the data network; Receive a call setup request from a user equipment registered with the SNPN; and In response to the call setup request, transmit a SIP invitation to the IP Multimedia Subsystem (IMS) of the PLMN.

16. The method according to claim 15, further comprises: Receive a SIP invitation for a user equipment (UE) registered with the SNPN from the PLMN; Receive a signal associated with the UE from the PLMN; and Forward the SIP invitation to the UE based on the signal.

17. The method according to claim 16, wherein the signal is Dual-Tone Multi-Frequency (DTMF) assigned to the UE.

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