User equipment context identifier for interaction between a radio access network and network functions of a core network

Abstract

A method implemented by a network function (NF) of a core network is provided that includes accessing a NF user equipment (UE) context associated with a UE at the NF. The NF UE context includes a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, and the RAN UE identifier includes an access node set identifier, an access node identifier, and an identifier of a RAN UE context associated with the UE. The method includes determining the access node in the access node set based on the access node set identifier and the access node identifier and the method includes initiating a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also includes the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

Description

TECHNOLOGICAL FIELD

[0001] The present disclosure relates generally to telecommunications and, in particular, to a user equipment context identifier for interaction between a radio access network and network functions of a core network. BACKGROUND

[0002] A telecommunications system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and / or other nodes by providing carriers between the various entities involved in the communications path. A telecommunications system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and / or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0003] In a wireless telecommunications system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Some wireless systems can be divided into cells, and are therefore often referred to as cellular systems.

[0004] A user can access the telecommunications system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and / or receive communications on the carrier.

[0005] The telecommunications system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and / or parameters which shall be used for the connection are also typically defined. One example of a telecommunications system is the Universal Mobile Telecommunications System (UMTS). Other examples of telecommunications systems are Long-Term Evolution (LTE), LTE Advanced and the so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3 GPP). BRIEF SUMMARY

[0006] Example implementations of the present disclosure are directed to telecommunications and, in particular, to a user equipment context identifier for interaction between a radio access network and network functions of a core network. The present disclosure includes, without limitation, the following example implementations.

[0007] Some example implementations provide an apparatus to implement an access node, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: establish a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN; assign a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the RAN-UE identifier in the RAN UE context; and provide the RAN-UE identifier to a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0008] Some example implementations provide an apparatus to implement an access node, the apparatus comprising: means for establishing a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN; means for assigning a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; means for storing the RAN-UE identifier in the RAN UE context; and means for providing the RAN-UE identifier to a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0009] Some example implementations provide a method implemented by an access node, the method comprising: establishing a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN; assigning a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; storing the RAN-UE identifier in the RAN UE context; and providing the RAN-UE identifier to a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0010] Some example implementations provide a computer-readable storage medium implemented at an access node, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: establish a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN; assign a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the RAN-UE identifier in the RAN UE context; and provide the RAN-UE identifier to a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0011] Some example implementations provide an apparatus to implement a network function (NF) of a core network, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a radio access network (RAN) - user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; assign a NF-UE identifier to the UE; store the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF; and invoke one or more services of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier.

[0012] Some example implementations provide an apparatus to implement a network function (NF) of a core network, the apparatus comprising: means for receiving a radio access network (RAN) - user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; means for assigning a NF-UE identifier to the UE; means for storing the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF; and means for invoking one or more services of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier.

[0013] Some example implementations provide a method implemented by a network function (NF) of a core network, the method comprising: receiving a radio access network (RAN) - user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; assigning a NF-UE identifier to the UE; storing the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF; and invoking one or more services of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier.

[0014] Some example implementations provide a computer-readable storage medium implemented at a network function (NF) of a core network, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a radio access network (RAN) - user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; assign a NF-UE identifier to the UE; store the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF; and invoke one or more services of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier.

[0015] Some example implementations provide an apparatus to implement a user equipment (UE), the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: initiate a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE within the RAN is established; receive an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the RAN-UE identifier in at least one UE context that is maintained independent of an RRC state of the UE.

[0016] Some example implementations provide an apparatus to implement a user equipment (UE), the apparatus comprising: means for initiating a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE within the RAN is established; means for receiving an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and means for storing the RAN-UE identifier in at least one UE context that is maintained independent of an RRC state of the UE.

[0017] Some example implementations provide a method implemented by a user equipment (UE), the method comprising: initiating a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE within the RAN is established; receiving an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and storing the RAN-UE identifier in at least one UE context that is maintained independent of an RRC state of the UE.

[0018] Some example implementations provide a computer-readable storage medium implemented at a user equipment (UE), the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: initiate a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE within the RAN is established; receive an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the RAN-UE identifier in at least one UE context that is maintained independent of an RRC state of the UE.

[0019] Some example implementations provide an apparatus to implement an access node, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a non-access stratum (NAS) service request message from a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message for a network function of a core network, the NAS service request message carried in an unsecured message that also comprises a RAN-UE identifier assigned to the UE; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; assign a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the new RAN-UE identifier in the RAN UE context; and send the NAS service request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0020] Some example implementations provide an apparatus to implement an access node, the apparatus comprising: means for receiving a non-access stratum (NAS) service request message from an user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message for a network function of a core network, the NAS service request message carried in an unsecured message that also comprises a RAN-UE identifier assigned to the UE; means for accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; means for assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; means for storing the new RAN-UE identifier in the RAN UE context; and means for sending the NAS service request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0021] Some example implementations provide a method implemented by an access node, the method comprising: receiving a non-access stratum (NAS) service request message from a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message for a network function of a core network, the NAS service request message carried in an unsecured message that also comprises a RAN-UE identifier assigned to the UE; accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; storing the new RAN-UE identifier in the RAN UE context; and sending the NAS service request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0022] Some example implementations provide a computer-readable storage medium implemented an access node, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a non-access stratum (NAS) service request message from a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message for a network function of a core network, the NAS service request message carried m an unsecured message that also comprises a RAN-UE identifier assigned to the UE; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; assign a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the new RAN-UE identifier in the RAN UE context; and send the NAS service request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0023] Some example implementations provide an apparatus to implement an user equipment (UE), the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: initiate a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; receive an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the new RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE.

[0024] Some example implementations provide an apparatus to implement an user equipment (UE), the apparatus comprising: means for initiating a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; means for receiving an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the new RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and means for storing the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE.

[0025] Some example implementations provide a method implemented by a user equipment (UE), the method comprising: initiating a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; receiving an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the new RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and storing the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE.

[0026] Some example implementations provide a computer-readable storage medium implemented an user equipment (UE), the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: initiate a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; receive an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the new RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE.

[0027] Some example implementations provide an apparatus to implement a network function (NF) of a core network, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: access a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; determine the access node in the access node set based on the access node set identifier and the access node identifier; and initiate a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0028] Some example implementations provide an apparatus to implement a network function (NF) of a core network, the apparatus comprising: means for accessing a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; means for determining the access node in the access node set based on the access node set identifier and the access node identifier; and means for initiating a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0029] Some example implementations provide a method implemented by a network function (NF) of a core network, the method comprising: accessing a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; determining the access node in the access node set based on the access node set identifier and the access node identifier; and initiating a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0030] Some example implementations provide a computer-readable storage medium implemented at a network function (NF) of a core network, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: access a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; determine the access node in the access node set based on the access node set identifier and the access node identifier; and initiate a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0031] Some example implementations provide an apparatus to implement an access node, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a non-access stratum (NAS) service request message relating to a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; store the NF-UE identifier in the RAN UE context; and process the NAS service request message.

[0032] Some example implementations provide an apparatus to implement an access node, the apparatus comprising: means for receiving a non-access stratum (NAS) service request message relating to an user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; means for accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; means for storing the NF-UE identifier in the RAN UE context; and means for processing the NAS service request message.

[0033] Some example implementations provide a method implemented by an access node, the method comprising: receiving a non-access stratum (NAS) service request message relating to a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; storing the NF-UE identifier in the RAN UE context; and processing the NAS service request message.

[0034] Some example implementations provide a computer-readable storage medium implemented at an access node, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a non-access stratum (NAS) service request message relating to a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; store the NF-UE identifier in the RAN UE context; and process the NAS service request message.

[0035] Some example implementations provide an apparatus to implement a user equipment (UE), the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN); identify a RAN-UE identifier in the RRC paging message; pass the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; receive a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and perform an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier

[0036] Some example implementations provide an apparatus to implement a user equipment (UE), the apparatus comprising: means for receiving a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN); means for identifying a RAN-UE identifier in the RRC paging message; means for passing the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; means for receiving a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and means for performing an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0037] Some example implementations provide a method implemented by a user equipment (UE), the method comprising: receiving a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN); identifying a RAN-UE identifier m the RRC paging message; passing the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; receiving a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and performing an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0038] Some example implementations provide a computer-readable storage medium to implement a user equipment (UE), the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN); identify a RAN-UE identifier in the RRC paging message; pass the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; receive a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and perform an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0039] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable unless the context of the disclosure clearly dictates otherwise.

[0040] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations. BRIEF DESCRIPTION OF THE FIGURE(S)

[0041] Having thus described example implementations of the disclosure in general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0042] FIG. 1 illustrates a telecommunications system that includes one or more public land mobile networks (PLMNs) coupled to one or more external data networks, according to some example implementations of the present disclosure;

[0043] FIG. 2 illustrates a deployment of a PLMN, according to some example implementations;

[0044] FIG. 3 illustrates an overview of a portion of a radio protocol stack architecture, according to some example implementations;

[0045] FIGS. 4A, 4B, 4C, 4D, 4E and 4F illustrate a signaling chart of a non-access stratum initial registration, according to some example implementations;

[0046] FIGS. 5Aand 5B illustrate a signaling chart of a NAS service request procedure, user equipment (UE) - initiated for packet data unit session user-plane activation, according to some example implementations;

[0047] FIGS. 6A, 6B and 7 illustrate signaling charts of a NAS service request procedure, network-initiated for signaling, according to some example implementations;

[0048] FIGS. 8A, 8B, 8C and 8D are flowcharts illustrating various steps in a method implemented by an access node, according to various example implementations;

[0049] FIGS. 9A, 9B, 9C and 9D are flowcharts illustrating various steps in a method implemented by a network function (NF) of a core network (CN), according to various example implementations;

[0050] FIGS. 10A, 10B, 10C, 10D and 10E are flowcharts illustrating various steps in a method implemented by a UE, according to various example implementations;

[0051] FIGS. 11A, 11B, 11C and HD are flowcharts illustrating various steps in a method implemented by an access node, according to various example implementations;

[0052] FIGS. 12A, 12B and 12C are flowcharts illustrating various steps in a method implemented by a UE, according to various example implementations;

[0053] FIGS. 13A, 13B, 13C and 13D are flowcharts illustrating various steps in a method implemented by a NF of a CN, according to various example implementations;

[0054] FIGS. 14A, 14B, 14C, 14D, 14E, 14F and 14G are flowcharts illustrating various steps in a method implemented by an access node, according to various example implementations;

[0055] FIGS. 15A, 15B, 15C, 15D, 15E, 15F, 15G and 15H are flowcharts illustrating various steps in a method implemented by a UE, according to various example implementations; and

[0056] FIG. 16 illustrates an apparatus according to some example implementations. DETAILED DESCRIPTION

[0057] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0058] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0059] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form. Furthermore, it should be understood that unless otherwise specified, the terms “data,” “content,” “digital content,” “information,” and similar terms may be at times used interchangeably. The term “network” may refer to a group of interconnected computers including clients and servers; and within a network, these computers may be interconnected directly or indirectly by various means including via one or more switches, routers, gateways, access points or the like.

[0060] Reference may be made herein to terms specific to a particular system, architecture or the like, but it should be understood that example implementations of the present disclosure may be equally applicable to any of a number of systems, architectures and the like. For example, reference may be made to 3GPP technologies such as Global System for Mobile Communications (GSM), UMTS, LTE, LTE Advanced, 5G NR, 5G Advanced and 6G; however, it should be understood that example implementations of the present disclosure may be equally applicable to non-3GPP technologies such as IEEE 802, Bluetooth and Bluetooth Low Energy.

[0061] Further, as used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry); (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions); or (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or a portion of a microprocessors), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0062] The above definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0063] FIG. 1 illustrates a telecommunications system 100 according to various example implementations of the present disclosure. The telecommunications system generally includes one or more telecommunications networks. As shown, for example, the system includes one or more public land mobile networks (PLMNs) 102 coupled to one or more other external data networks 104 - notably including a wide area network (WAN) such as the Internet. Each of the PLMNs includes a core network (CN) 106 backbone such as the Evolved Packet Core (EPC) of LTE, the 5G core network (5GC) or the like; and each of the core networks and the Internet are coupled to one or more radio access networks (RANs) 108, air interfaces or the like that implement one or more radio access technologies (RATs). As used herein, a “network device” refers to any suitable device at a network side of a telecommunications network. Examples of suitable network devices are described in greater detail below.

[0064] In addition, the system includes one or more radio units that may be varyingly known as user equipment (UE) 110, terminal device, terminal equipment, mobile station or the like. The UE is generally a device configured to communicate with a network device or a further UE in a telecommunications network. The UE may be a portable computer (e.g., laptop, notebook, tablet computer), mobile phone (e.g., cell phone, smartphone), wearable computer (e.g., smartwatch), or the like. In other examples, the UE may be an Internet of things (loT) device, an industrial loT (IIoT device), a vehicle equipped with a vehicle-to-everything (V2X) communication technology, or the like. In some examples, as referenced by 3GPP, the UE may be a narrowband loT (NB-IoT) device, an enhanced machine-type communication (eMTC) device, a reduced capability (RedCap) device, an ambient loT device, or the like.

[0065] In operation, these UEs 110 may be configured to connect to one or more of the RANs 108 according to their particular radio access technologies to thereby access a particular CN 106 of a PLMN 102, or to access one or more of the external data networks 104 (e.g., the Internet). The external data network may be configured to provide Internet access, operator services, 3rd party services, etc. For example, the International Telecommunication Union (ITU) has classified 5G mobile network services into three categories: enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine type communications (mMTC) or massive internet of things (MIoT).

[0066] Examples of radio access technologies include 3GPP radio access technologies such as GSM, UMTS, LTE, LTE Advanced, 5GNR, 5G Advanced, and 6G. Other examples of radio access technologies include IEEE 802 technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.15 (including 802.15.1 (WPAN / Bluetooth), 802.15.4 (Zigbee) and 802.15.6 (WBAN)), Bluetooth, Bluetooth Low Energy (BLE), ultra wideband (UWB), and the like. Generally, a radio access technology may refer to any 2G, 3G, 4G, 5G, 6G or higher generation mobile communication technology and their different versions, as well as to any other wireless radio access technology that may be arranged to interwork with such a mobile communication technology to provide access to the CN 106 of a mobile network operator (MNO).

[0067] In various examples, a RAN 108 may be configured as one or more macrocells, microcells, picocells, femtocells or the like. The RAN may generally include one or more RAN nodes that are configured to interact with UEs 110. In various examples, a RAN node may be referred to as a base station (BS), access point (AP), base transceiver station (BTS), Node B (NB), evolved NB (eNB), macro BS, NB (MNB) or eNB (MeNB), home BS, NB (HNB) or eNB (HeNB), next generation NB (gNB), enhanced gNB (en-gNB), next generation eNB (ng-eNB), or the like. The RAN may include some type of network controlling / governing entity responsible for control of the RAN nodes. The network controlling / governing entity and RAN node may be separate or integrated into a single apparatus. The network controlling / governing entity may include processing circuity configured to carry out various management functions, etc. The processing circuity may be associated with a memory, computer-readable storage medium or database for maintaining information required in the management functions.

[0068] ARAN 108 may be centralized or distributed. In various examples, components of a RAN may be interconnected by Ethernet, Gigabit Ethernet, Asynchronous Transfer Mode (ATM), optical fiber, dark fiber, passive wavelength division multiplexing (WDM), WDM passive optical network (WDM-PON), optical transport network (OTN), time sensitive networking (TSN) and / or any other data link layer network, possibly including radio links. The RAN may be connected to a CN 106 through one or more gateways, network functions or the like.

[0069] As will be appreciated, a PLMN 102 may be deployed in a number of different manners. FIG. 2 illustrates a deployment 200 of a PLMN, such as a 4G LTE, 5G or 6G deployment, according to some example implementations. As shown, the deployment includes a CN 106, and RAN 108 with one or more RAN nodes 202 configured to interact with UEs 110. In a 4G LTE deployment, the EPC is the CN, and the evolved UMTS terrestrial radio access network (E-UTRAN) is the RAN; and the E-UTRAN includes one or more eNBs (RAN nodes) configured to connect UEs to the E-UTRAN to thereby access the EPC. Similarly, in a 5G deployment, the 5GC is the CN 106, and the next generation (NG) radio access network (NG-RAN) is the RAN 108; and the NG-RAN includes one or more gNBs (RAN nodes) configured to connect UEs 110 to the NG-RAN to thereby access the 5GC. The term ‘gNB’ in 5G may correspond to the eNB in 4G LTE.

[0070] Some deployments of 4G LTE and 5G in particular are considered standalone (SA) deployments. Other deployments combine 4G LTE and 5G technologies, and are referred to as non-standalone (NSA) deployments. In some deployments, the E-UTRAN includes one or more ng-eNBs that are configured to communicate with the 5GC, and that may also be configured to communicate with one or more gNBs. Similarly, in another deployment, the NG-RAN may include one or more en-gNBs that are configured to communicate with the EPC, and that may also be configured to communicate with one or more eNBs. In various instances, a single UE 110, a dual-mode or multimode UE, may support multiple (two or more) RANs—thereby being configured to connect to multiple RANs, such as 4G LTE and 5G.

[0071] Although only one RAN node 202 is shown in FIG. 2, the deployment may comprise multiple RAN nodes, and at least some of the RAN nodes may be connected to one another by a network interface, such as an Xn interface. The network interface between RAN nodes may support the exchange of signaling messages formatted according to an application layer protocol, such as the Xn application protocol (XnAP) for the Xn interface. Similarly, the RAN nodes may be connected to the CN 106 by a network interface, referred to as the NG interface in 5G NR, which is a network interface between the RAN node and an access and mobility management function (AMF) of the 5GC. The NG interface supports the exchange of signaling messages formatted according to the NG application protocol (NGAP). The NGAP supports a number of procedures, such as to establish, maintain or release the RAN part of a communication session between a UE 110 and external data network 104 (referred to in 5G NR as a packet data unit (PDU) session), perform handover of a UE, and the like.

[0072] The deployment 200 may also be equipped with a number of network functions (NFs) 204. A NF may refer to an operational and / or a physical entity located within or outside of the CN 106. A NF may be a specific network node or element, or a specific function or set of functions carried out by one or more entities, such as virtualized network elements (VNFs). One physical node may be configured to perform plural NFs. A NF can be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., on a cloud infrastructure.

[0073] One example of a suitable NF is a mobility management (MM) NF 206 that is responsible for mobility management of the UE 110. Two other NFs are shown as NFx 208, which may be responsible for a number of functions, such as session management (SM), interworking, data management or storage, authentication or a combination of one or more of these functions. In the context of a 3 GPP 5G service based architecture (SBA), the 5GC (CN 106) may include a number of NFs, such as an access and mobility management function (AMF) that is responsible for mobility management of the UE. Other CN NFs in the 5GC include one or more of a session management function (SMF), a network slice selection function (NSSF). a network exposure function (NEF), a network repository function (NRF), a unified data management (UDM), an authentication server function (AUSF), a policy control function (PCF), a short message service function (SMSF), a location management function (LMF), a service key management function (SKMF), a security anchor function (SEAF), an application function (AF), or the like.

[0074] FIG. 3 illustrates an overview of a portion of a radio protocol stack 300 architecture, between a UE 110 and RAN node 202, according to some example implementations. As shown, the radio protocol stack has two different stacks depending on the type of data that is processed by the stack. User data goes through a user plane (UP) stack 302, signaling messages go through a control plane (CP) stack 304. Both UP and CP stacks are made up of a common structure including a Layer 1 (LI) with a physical layer (PHY) 306, and a layer 2 (L2) with sublayers including medium access control (MAC) 308, radio link control (RLC) 310, and packet data convergence protocol (PDCP) 312. A layer 3 (L3) sits on top of PHY / MAC / RLC / PDCP, and includes sublayers that are different between the CP and UP. In the UP, L3 includes a sublayer referred to as service data adaptation protocol (SDAP) 314 that is connected to the user plane function (UPF) in the CN 106. In the CP, L3 includes two sublayers referred to as radio resource control (RRC) 316 and non-access stratum (NAS) 318, and the NAS layer connects to the CN.

[0075] Generally, each layer of the radio protocol stack 300 performs a specific data communications task, a service to and for the layer that precedes it. For example, the RLC 310 provides its services to the PDCP 312. Similarly, the PDCP provides its services to the SDAP 314 (in the UP 302) or the RRC 316 (in the CP 304). The main services or functions of the PDCP include for example: header compression and decompression, transfer of user data, ciphering and deciphering, and timer-based service data unit (SDU) discard.

[0076] The process of layers of the radio protocol stack 300 performing specific data communication tasks can be likened to placing a letter in a series of envelopes before it is sent through the postal system. Each succeeding envelope adds another layer of processing or overhead information necessary to process the transaction. Together, all the envelopes help make sure the letter gets to the right address and that the message received is identical to the message sent. Once the entire package is received at its destination, the envelopes are opened one by one until the letter itself emerges exactly as written.

[0077] A data flow between a source and destination, such as the UE 110 and RAN node 202, is from top to bottom in the source, across the communications line, and then from bottom to top in the destination. Each time, user data passes downward from one layer to the next layer in the source more processing information is added. When that information is removed and processed by the peer layer in the destination, it causes various tasks (error correction, flow control, etc.) to be performed.

[0078] Returning to FIG. 2, in some deployments such as the deployment 200, operations of the RAN node 202 may be distributed or functionally split into components comprising one or more remote radio head (RRHs) or radio units (RUs), and a baseband unit (BBU); and in some architectures, the BBU may be split into a distributed unit (DU) 210 and a central / centralized unit (CU) 212, such as a server, host or node. In some architectures, the RRH / RU and DU may be collocated. It is also possible that node operations may be distributed among a plurality of servers, hosts or nodes.

[0079] It should also be understood that the distribution of work between CN 106 operations and RAN node 202 operations may vary depending on implementation. Thus, a 5G network architecture may be based on a so-called CU-DU split. One gNB-CU (central node) may control one or more gNB-DUs. The gNB-CU may control a plurality of spatially separated gNB-DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some example implementations, however, the gNB-DUs (also called DU) may comprise, for example, the RLC 310, MAC 308 and PHY 306 layers, whereas the gNB-CU (also called a CU) may comprise the layers above the RLC layer, such as the PDCP 312 layer, RRC, and an internet protocol (IP) layer. Other functional splits are also possible. It is considered that skilled person is familiar with the OSI model and the functionalities within each layer.

[0080] In some example implementations, the server or CU 212 may generate a virtual network through which the server communicates with the radio node. In general, virtual networking may involve a process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Such virtual network may provide flexible distribution of operations between the server and the radio head / node. In practice, any digital signal processing task may be performed in either the CU or the DU 210, and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

[0081] In telecommunications, context information (or at times more simply “context”) refers to information or parameters associated with an entity or element. In this regard, UE context generally includes context information associated with a UE 110, which may be used to establish, maintain and optimize communication sessions or transactions with the UE. The UE context may include, for example, UE identity and capabilities, whether or not the UE has an established RRC connection, PDU session context, security key(s) / context(s) between the UE and RAN 108, identities of peer node connections for the UE, mobility restriction lists, and the like.

[0082] In 3GPP, a number of RAN UE context identifiers are currently defined for use on specific interfaces and in specific UE connection states within the RAN 108. For example, the inactive radio network temporary identifier (I-RNTI) is defined for use when a UE 110 is in RRC inactive state and across the XnAP and RRC interfaces, and the bits that makeup the I-RNTI are not fully defined. As another example, the RAN UE NGAP identifier (ID) is defined for use across the N2 NGAP interface. The NGAP ID is specific to NGAP association between the RAN and AMF. These RAN UE context identifiers are not defined for use to support RAN resiliency in which a UE may identify its RAN UE context to the RAN in order for the RAN to locate its RAN UE context. The current RAN UE context identifiers are also not defined for use to support interactions between the RAN and other CN NFs.

[0083] Example implementations of the present disclosure therefore provide a RAN UE identifier (referred to at times as a “RAN-UE ID”) for a RAN UE context that is encoded to include information that supports RAN resiliency, and that supports interaction between the RAN 108 and NFs 204 of the CN 106. In particular, for example, the RAN-UE ID may include an identifier of a RAN set (a set of RAN nodes), an identifier of a RAN node 202 in the RAN set via which a RAN UE context can be accessed, and an identifier of the RAN UE context within the RAN set (the identifier of the RAN UE context being unique to the RAN UE context within the RAN set).

[0084] In some more particular, examples, the format of the RAN-UE ID may be defined as follows: RAN-UE ID = RAN Set ID + RAN Node ID + RAND UE ID The RAN set ID identifies a set of RAN node IDs that are homogenous and support common functionality and share access to RAN UE context information identified by the RAND UE ID. A RAN set may serve a specific geographic area / region. The RAN node ID identifies an instance (or optionally multiple instances) of a RAN node 202 within a RAN set. An instance of a RAN node ID could, for example, be an gNB ID. And the RAND UE ID is a unique RANDom number within a RAN set ID that identifies a RAN UE context within the RAN set.

[0085] A RAN node 202 is responsible for assigning a RAN-UE ID to UE(s) it is serving, and the RAN node identifier (ID) included in the RAN-UE ID may identify the serving RAN node. The serving RAN node may also be responsible for providing and updating the RAN-UE UEs 110 and peer entities (e g., RAN nodes 202, NFs 204). The peer entities may obtain a RAN-UE ID directly from interaction with the serving RAN node or indirectly via other peer entities. When possible, the RAN-UE ID is exchanged encrypted. In cases where this is not possible, such as when a UE sends a service request with its RAN-UE ID in the clear, the serving RAN node may update the RAN-UE ID and provide it encrypted to the UE at the next earliest opportunity.

[0086] A RAN UE context, identified by a RAN-UE ID, may be maintained within a specific RAN set irrespective of the RRC state of the UE 110 (idle, inactive or connected). In this regard, the RAN UE context may be stored in a shared storage for the RAN set, such as in a database that stores commonly for the whole RAN set or a RAN node 202 that stores context for all the RAN nodes in the RAN set. The RAN-UE ID may also enable interconnected RAN sets to identify and share the RAN UE context, such as using the Xn or service based interface (SBI) interfaces. This may enable a reduction in the amount of data that needs to be transferred from CN 106 to RAN 108 as well as potential efficiencies in signaling latency.

[0087] In various examples, the RAN 108 may directly interface with multiple NFs 204 when the RAN exposes services as a producer which can be consumed by any authorized NF. Similarly, as an authorized consumer, the RAN may consume services of NFs, that act as producers, to which RAN directly interfaces. In these and other similar examples, the RAN-UE ID may be used by NFs that have direct communication with the RAN. The NFs that have not yet established direct communication with the serving RAN node may receive a RAN-UE ID indirectly via a designated one of the NFs (e.g., MM NF 206) that has established direct communication with the serving RAN node.

[0088] The NFs 204 and other peer entities may use the RAN-UE ID to communicate with the RAN node 202 serving the UE 110 for UE-related transactions. Peer entities may subscribe to events concerning UE status, change in UE context (e.g., quality of service (QoS) parameters). Using the RAN-UE ID, peer entities may make requests to the RAN 108 for a specific UE such as, for example, the connection status of the UE (idle, inactive, connected), request the transfer of a downlink NAS message to the UE, update RAN UE context parameters (e.g., UE aggregate maximum bit rate (AMBR)), or the like. Similarly, the serving RAN node may communicate with peer entities about a RAN UE context, identified by the RAN-UE ID, to provide updates for example about UE connection status, ability to support certain QoS requirements, NAS non-delivery notifications, and the like.

[0089] The RAN-UE ID of example implementations may be used by peer entities to obtain services from the RAN 108 for a specific UE 110 in a number of different manners. Peer entities may use the RAN set identifier (RAN set ID) in the RAN-UE ID to identify which RAN set the RAN UE context is stored in, and the RAN node identifier (RAN node ID) to identify a RAN node within the RAN set ID via which the RAN UE context may be accessed. In this regard, peer entities may be configured with information about the mapping of RAN set ID / RAN node ID to a specific RAN node instance address (e.g., IP / fully qualified domain name (FQDN)). Additionally or alternatively, peer entities may dynamically discover mapping information from a central repository, such as an NRF used in 5G. In some of these examples, RAN node instances may register their respective RAN node profiles to the NRF indicating its RAN set ID, RAN node ID value(s) and RAN node instance address(es).Then when a peer entity queries the NRF for a specific RAN set / RAN node ID value, the NRF may return the address of the RAN node instance (or instances) supporting that RAN set / RAN node ID value. If multiple RAN node instances are returned, the peer entity may select one based on own predefined selection rules / policies.

[0090] After determining the RAN node 202 in the RAN set based on the RAN-UE ID, the peer entity may communicate the RAN-UE ID to the RAN node to enable the RAN node to identify the RAN UE context based on the RAN UE context ID (e.g., RAND UE ID) within the RAN-UE ID. In cases in which the RAN node identified by the RAN node ID is not accessible, the RAN set ID may be used as an input query parameter to discover other RAN node ID’s in the RAN set, one of which may be selected and used to access the RAN UE context in the RAN set ID.

[0091] A peer entity may assign a (temporary) identifier to the UE 110 to identify UE context at the peer entity, and that identifier may be included with the RAN-UE ID. In the case of a peer NF 204, for example, this identifier may be referred to as a NF-UE identifier (or NF-UE ID). In a more specific example, this identifier may be a globally unique temporary identity (GUTI) or its shortened serving temporary mobile subscriber identity (S-TMSI) form. In an even more specific example for a UE identifier assigned by an NF of a particular type “XX,” the identifier may be an XX GUTI or XX-S-TMSI, such as a MM GUTI or MM-S-TMSI when assigned by the MM NF 206, or a SM GUTI or SM-S-TMSI when assigned by the SM NF. The serving RAN node 202 may cache / store the UE identifiers assigned by and received from peer entities to the RAN UE context, and these UE identifiers may also identify UE context at the respective peer entities. Similarly, the peer entities may cache / store the RAN-UE ID to their respective UE context. In the case of a NF, this UE context may be referred to as a NF UE context.

[0092] As indicated, the RAN UE context identified by a RAN-UE ID may be maintained independent of the RRC state of the UE 110 (idle, inactive or connected). In this regard, a UE transitioning from an idle state to a connected state may send its RAN-UE ID to a target RAN node 202 to enable the target RAN node retrieve the UE’s RAN UE context from the shared storage location for the RAN set. Similarly, during handover of the UE in the connected state, a target RAN node may use the RAN-UE ID to retrieve the RAN UE context from shared storage location without going to the serving RAN node. When the UE is in the idle state, if allowed, certain parameters in the RAN UE context may be read and / or updated.

[0093] In some more particular example implementations, a UE 110 may obtain its RAN-UE ID when the UE establishes an RRC connection and successfully registers with a CN 106. The serving RAN node 202 may generate and send the RAN-UE ID to the UE in an RRC information element (IE) via RRC signaling, such as via an RRC reconfiguration message. The UE RRC layer 316 may store the RAN-UE ID in the RRC UE context, and use the RAN-UE ID as an identifier of RRC context information, such as RRC security context information, and other information relevant at the RRC layer, which may be maintained even in the RRC idle mode. The RRC layer may also provide the RAN-UE ID to the UE NAS layer 318 at which the RAN-UE ID is stored in the NAS UE context. In some examples, the RAN node provides the RAN-UE ID to the UE encrypted, such as after access stratum (AS) / RRC security has been established, to protect UE privacy.

[0094] One or more NFs 204 of the CN 106 may discover the RAN-UE ID m a number of different manners. In the CN, the MM NF 206 (same as or similar to the AMF in 5G NR) may maintain information about successfully registered UEs 110 in the CN, their RRC state (connected, inactive or idle), and associated RAN-UE ID. The NFs other than the MM NF, shown as NFx 208, may explicitly request that the MM NF provide the RAN-UE ID for a UE when the UE is in an RRC connected or RRC inactive state.

[0095] When a UE 110 is in the RRC idle state, the MM NF 206 may trigger paging of the UE to cause the UE to (re)establish an RRC connection, and return the associated RAN-UE ID to the NFx 208 if the UE successfully (re)establishes an RRC connection. In another example, the MM NF may inform the NFx that the UE is in the RRC idle state, and subscribe the NFs to receive a notification when the UE enters the RRC connected state. In yet another example, the NFx may subscribe with the MM NF to receive notifications when the UE transitions between RRC connected, RRC inactive and RRC idle states, and receive the associated RAN-UE ID.

[0096] Multiple different NFs 204 (e g., MM NF 206, SM NF, SMSF, LMF) may use the RAN-UE ID to request services from RAN 108 related to a specific UE 110. The NF may use the RAN set ID and RAN node ID information to identify the address (e g., IP address / FQDN) of the serving RAN node 202. The NF may then send a service request to the serving RAN node that includes, among other information, the RAN-UE ID and the NF’s UE ID (e.g., SM-S-TMSI). Based on the identifier of the RAN UE context (e.g.. RAND UE ID) from the RAN-UE ID, the serving RAN node may identify the RAN UE context within the RAN set and execute the requested RAN service. The serving RAN node may also store the received NF-UE ID to its RAN UE context.

[0097] Similar to discovery of the RAN-UE ID, a NF 204 may also take into consideration the UE RRC state (connected, inactive or idle) before invoking a RAN service request using the RAN-UE ID. For example some RAN services may only be allowed when the UE 110 is in RRC connected / inactive state (e.g., delivery of NAS message to UE) and some RAN services may be allowed when the UE is in RRC idle state (e.g., update of UE parameters in RAN e.g. UE AMBR). In some examples in which the UE 110 is indicated as being in RRC idle, the NF may use the RAN set ID to discover the RAN nodes and their respective address(es) in the RAN set. The NF may then select the address of one of the RAN nodes to perform paging via any of the RAN nodes within the RAN set.

[0098] The serving RAN node 202 may use the RAN-UE ID as its UE context identifier towards multiple different NFs 204, and provide the RAN-UE ID when communicating with the NFs. The serving RAN node may trigger direct communication with a NF for which the serving RAN node may or may not already have a NF-UE ID for that NF. In the case of an initial registration where the UE 110 does not provide a MM NF-UE ID (e g., MM-S-TMSI), the serving RAN node may discover and select the MM NF 206 (based on various criteria) and provide the RAN-UE ID to the selected MM NF. In response, the MM NF may provide its MM NF-UE ID to the serving RAN node. The serving RAN node may store the MM NF-UE ID to its own RAN UE context and use the MM NF-UE ID in subsequent UE associated direct communication with the MM NF.

[0099] In other cases, the serving RAN node 202 may wait to learn the NF-UE ID of a NF 204 before the serving RAN node initiates UE-associated direct communication with the NF. In some examples, a NFx 208 (e.g., SMSF) may discover a RAN-UE ID from the MM NF 206. The NFx may request that a serving RAN node forward a NAS message (e.g., NAS security mode command (SMC)) to the UE 110, and provide its NF- UE ID (e.g., SMS-S-TMSI) as part of the request. The serving RAN node may store the NF-UE ID to its own RAN UE context. If RAN 108 is unable to deliver the NAS message to the UE, the serving RAN node may use the NF’s UE ID to send a NAS nondelivery notification to the NF.

[0100] As suggested above, a serving RAN node 202 uses the RAN-UE ID and the NF-UE ID to communicate directly with NF(s) 204 about specific UE services in the RAN 108. For example, a serving RAN node may use the RAN-UE ID and MM NF-UE ID (e.g., MM-S-TMSI) to inform the MM NF 206 about changes in the UE’s RRC state. Similarly, a serving RAN node may use the RAN-UE ID and SM NF-UE ID (e.g., SM-S-TMSI) to notify a SM NF about changes to its capabilities to support requested QoS requirements. In another example, a serving RAN node may notify a NF that delivery of a NAS message to a UE IIO has failed.

[0101] A UE 110 may store its RAN-UE ID and use the .RAN-UE ID to manage context with RRC / NAS connections. As indicated above, the UE may obtain its RAN-UE ID when the UE establishes an RRC connection and successfully registers with the CN 106. When the UE transitions to the RRC idle state and then back to an RRC connected state, the UE may provide its RAN-UE ID to a new serving RAN node instance. In particular, for example, the UE 110 may provide its RAN-UE ID to the new serving RAN node instance in an RRC IE within an RRC message, such as an RRC setup complete message.

[0102] From the RAN set ID and RAN node ID in the RAN-UE ID, the new serving RAN node 202 may determine the new serving RAN node belongs to the same RAN set as indicated in the RAN-UE ID; and if so, the new serving RAN node may access the RAN-UE context using the identifier of the RAN UE context (e.g., RAND UE ID) from the RAN-UE ID. It is also possible the RAN set ID and RAN node ID m the RAN-UE ID may point to the current serving RAN set and RAN node as well, such as when the 'UE 110 transitions to RRC idle and back to RRC connected without changing RAN node or RAN set.

[0103] If the new seiwing RAN node 202 is in a different RAN set to that of the RAN set indicated in the RAN-UE ID, and if inter-RAN set communication is possible as indicated above, the new serving RAN node may retrieve the RAN UE context from the former RAN set by using the RAN set ID from the RAN-UE ID to discover and select a RAN node instance to query using the RAND-UE ID. When the RAN-UE ID is sent in an unsecured RRC message, such as an RRC setup complete message, the RAN-UE ID is not encrypted and could be used to identify the UE. The new serving RAN node instance may therefore also update the or otherwise assign a new RAN-UE identifier, which may be provided back to the UE encrypted. The new serving RAN node instance may also provide the new RAN-UE identifier to the NFs 204.

[0104] If the new serving RAN node cannot locate the RAN UE context indicated by RAN-UE ID, the new serving RAN node may establish a new RAN UE context, assign new a RAN-UE ID to the new RAN UE context, and provide the new RAN-UE ID to the UE 110 and NFs 204.

[0105] As indicated above, a MM NF 206 may trigger paging of a UE 110 m the RRC idle state to cause the UE to (re)establish an RRC connection. In some examples, the RAN-UE ID may be included in a paging message sent via the RAN 108 to the UE. A UE that has stored a RAN-UE ID in its RRC UE context may listen for the presence of its RAN-UE ID in received paging messages When a UE’s RAN-UE ID is detected in a paging message, the UE RRC layer 316 may pass the RAN-UE ID, along with any other relevant parameters from the paging message, to the UE NAS layer 318. In response, the UE NAS layer may request that the UE RRC layer (re)establish an RRC connection, and pass the RAN-UE ID to the UE RRC layer, along with any additional relevant parameters, such as NAS messages), NAS temporary identifiers (XX-S-TMSI), or the like. The UE RRC layer may use the RRC-UE ID received from the UE NAS layer to identify the RRC UE context, and apply any relevant RRC UE context information from the RRC UE context, during an RRC connection procedure to (re)establishment of the RRC connection, towards the RAN. The UE RRC layer may include the RAN-UE ID (and other parameters received from the UE NAS layer) m relevant RRC messages sent to the RAN, such as described above.

[0106] The RRC connection procedure performed by the UE 110 may be an RRC connection setup procedure (RRC connect) or an RRC connection reestablishment procedure (RRC re-connect). In some examples, the UE may determine the type of RRC connection procedure to perform, such as based on the RRC UE context identified by the RAN-UE ID. In this regard, the UE (e.g., UE RRC layer 316) may determine the RRC UE context excludes a security context, and perform an RRC connection setup procedure; or the UE may determine the RRC UE context includes a security context, and perform an RRC connection reestablishment procedure to which the security context is applied.

[0107] In some examples, the UE 1.1.0 may determine the type of RRC connection procedure further based on a time duration of the UE in the RRC idle state, which may relate to a time that the RAN UE context identified by the RAN-UE ID is maintained by the RAN set. Tn some of these examples, the UE (eg., UE RRC layer 316) may determine the time duration of the UE in the RRC idle state exceeds a threshold duration, and perform an RRC connection setup procedure. In another example, the UE may determine the RRC UE context includes a security context, and that the time duration of the UE in the RRC idle state does not exceed a threshold duration, and perform an RRC connection reestablishment procedure to which the security context is applied.

[0108] In some further examples, the UE 110 may determine the type of RRC connection procedure further based on tracking area codes (TAC) broadcast by the RAN 108. In some of these examples, the UE (eg., UE RRC layer 316) in the RRC idle state may determine the UE has moved into area associated with another, different TAC, and perform an RRC connection setup procedure. In another example, the UE may determine the UE remains within the area of the same TAC, or that the UE has otherwise not moved into an area associated with a different TAC., and that the RRC UE context includes a security context, perform an RRC connection reestablishment procedure to which the security context is applied. In yet another example, the UE may determine the LTE remains within the area of the same TAC, the RRC UE context includes a security' context, and that the time duration of the UE in the RRC idle state does not exceed a threshold duration, and perform an RRC connection reestablishment procedure to which the security context is applied.

[0109] In some examples, the UE 110 may be configured to store a specific RRC-UE ID that identifies an AS / RRC context for RRC connections with the RAN 108, in addition to or m lieu of the RAN-UE ID. In some of these examples, the RRC-UE ID (also referred to as an RRC ID or an AS context ID) may be limited to RRC connections, while the RAN-UE ID may be applied end-to-end. The RAN-UE ID may therefore be used in paging messages without reallocating the MM NF-UE ID (e.g., MM-S-TMSI), although a new RAN-UE ID may be assigned. The RAN-UE ID may also enable the RAN to locate the storage location of RAN UE context, as described above.

[0110] In some examples including both the RAN-UE ID and the RRC-UE ID, the RAN-UE ID may be used between the RAN 108 and NFs 204, while the RRC-UE ID is used between the Uli 110 and the RAN. The UE may store the RRC-UE ID to identify its AS / RRC context with the RAN, and the NFs may store the RAN-UE ID to identify the RAN UE. context The RAN (e.g., RAN node set, serving RAN node 202), then, may receive both the RRC-UE ID and the RAN-UE ID, and maintain a mapping between the RRC-UE ID and the RAN-UE ID.

[0111] To further illustrate the RAN-UE ID, FIGS. 4A-4F illustrate a signaling chart 400 of a NAS initial registration, according to some example implementations. As shown at step 401 of FIG. 4A, a UE IIO initiates an NAS registration procedure during setup of an RRC connection with a selected RAN node 202 of a RAN set. The initial NAS message is carried in an RRC setup complete message that provides NAS type information (NASType = MM) that indicates a type of NF 204 for initial registration (MM NF 206).

[0112] The selected RAN node 202 at step 402 assigns a .RAN-UE ID to the UE 110 and establishes a RAN UE context to which the RAN-UE ID and other UE related context information is stored. The RAN-UE ID identifies the RAN UE context in the RAN set. The RAN node uses NAS message (Msg) == MM to discover and select the MM 206 (MM NF == NF1), and sends the MM NF an initial UE message that includes the RAN-UE ID of the UE.

[0113] On receipt of the initial UE message, the MM NF 206 at step 403 assigns a NF-UE identifier MM-GUT1 (from which its shorten version MM-S-TMSI is derived), and stores the MM-S-TMSI along with the received RAN-UE ID to the UE’s context in the MM NF. The MM NF uses MM-S-TMSI as the MM UE context identifier, and stores the RAN-UE ID as the RAN UE context identifier. As part of an authentication and key agreement (AKA) procedure, the MM NF may also interface with a SKMF 420 (or SEAF) and AUSF / UDM 422 for assignment of an initialization key set identifier (KSI), which is provided to UE 110.

[0114] When sending a UE-associated request to the RAN 108, the MM NF 206 at step 404 uses the RAN set ID and RAN node ID derived from the RAN-UE ID to identify the serving RAN node 202. The MM NF may discover the serving RAN node address information (e.g., IP address / FQDN) by querying its local cache or an NRF using the RAN set ID and RAN node ID as input query parameters. The MM NF may send the request including the RAN-UE ID and the MM-S-TMSI to the discovered RAN node address of the serving RAN node.

[0115] On receipt of the request from MM NF 206, the serving RAN node 202 at step 405 may use the RAN-UE ID to discover the RAN set ID, RAN node ID and the RAN UE context ID (e.g., RAND UE ID). The serving RAN node may check the RAN set ID and RAN node ID to ensure the request is valid for the current serving RAN set and RAN node, and use the RAN UE context ID to identify the UE’s ILAN UE context within the current serving RAN set. Once validated, the serving RAN node may store the received MM-S-TMSI to the RAN UE context and tag or otherwise associate the MM-S-TMSI with NAS type information that indicates the NAS type ::: MM (mobility management). The serving RAN node processes the request and sends a message to the UE 110, such as an RRC downlink information transfer carrying a MM NAS message.

[0116] The UE 110 provides the NAS type ::: AIM to its RRC layer 316; and in response, the UE sends an RRC message transporting a N AS message and including the NAS type information MM. On receipt of the RRC message from the UE, the serving RAN node 202 at step 406 uses the NAS type information MM to identify the NF-UE identifier of the UE in the CN 106, which in this case is the MM-S-TMSI. The serving RAN node discovers the address of the serving NF 204 from the MM-S-TMSI to identify the serving MM NF 206, and sends a request to the MM NF that includes both the RAN-UE ID and the MM-S-TMSI.

[0117] The MM NF 206 uses the RAN-UE ID to discover from which RAN node 202 and which RAN UE context this message was sent, and the MM NF uses the MM-S-TMSI to identify the UE’s context with the .MM NF. Subsequent exchanges of messages between the serving RAN node and MM NF may now include both the RAN-UE ID and MM-S-'TMSI identifiers to identify the UE’s RAN context and the UE’s MM context respectively.

[0118] As also shown in FIG. 4A, a first KSI (aKSI-1) and protection key (Kp-1) may be assigned and provided to UE 110. The SKMF 420 may store an association between the MM-S-TMSI and aKSI-1 association. As shown in FIG. 4B, the MM NF 206 (NF1) may store aKSI-l / Kp-1 in its NAS security' context, and trigger a NAS SMC with the UE 110 using aKSI-1 integrity protected. The UE may use aKSI-1 to identify Kp-1 and validate security, and associate aKSI-1 / Kp-1 associated with NAS type := MM in its UE context. The UE may then send a full NAS initial registration request in a NAS SMC complete message, which the MM NF may receive and security validate using aKSK-l / Kp-1.

[0119] As shown in FIG. 4C, the MM NF 206 (NF1) provides information, such as security parameters, mobility restrictions, and the like, to the serving RAN node 202, which establishes a secured RRC connection with the UE 110 using an RRC security command / complete procedure. After the secured RRC connection is established, the serving RAN node at step 407 provides the RAN-UE ID to the UE in a secured RRC message, such as in an RRC reconfiguration message. Then at step 408, the UE’s RRC layer 316 may store the RAN-UE ID in its RRC UE context, and pass the RAN-UE ID to the UE’s NAS layer 318 which may store the RAN-UE ID in its NAS context for subsequent use. Other information such as the MM-GUTI and aKSI-1 may also be stored to the N AS context in the UE 110.

[0120] As shown in FIG. 4D, the MM NF 206 (NF1) may discovers and select one or more NFx 208, such as the SMSF (NF2) and PCF (NF3), and establishes a policy association. The NFs assign respective NF-UE identifiers of the UE, and provide the NF-UE identifiers to the MM NF. In this regard, the SMSF may provide a SMSF-S-TMSI, and the PCF may provide a UEP-S-TMSI. The MM NF may send a NAS registration accept message secured using aKSI-1 security context. The MM NF may also send one or more NFx notifications.

[0121] As shown m FIG. 4E, the MM NF 206 / SKMF 420 at steps 409a, 409b may-assign and notify each selected NFx 208 (e.g., SMSF, PCF) of the security information (aKSK-x / Kp-x) and RAN-UE ID, and the NFx may trigger N AS SMC with UE 110 to establish NAS security. As shown in FIG. 4F, each NFx at steps 410a, 410b may update its respective NF UE context information to include and store the RAN-UE ID. The NFx send a request to the serving RAN node 202 for transport of a NAS message, in this case a NAS SMC, to the UE identified by the RAN-UE ID. The NFx provides its NF-UE identifier (e g., SMS-S-TMSI, UEP-S-TMSI) and NAS type information (e.g., SMS, UEP) to the serving RAN node in the request. The NFx may use a process the same as or similar to the MM NF to discover and send the message to the address of the serving RAN node.

[0122] The serving RAN node 202 at. steps 411a, 411b may use the received RAN-UE ID to validate the RAN set ID and RAN node ID are correct, and the serving RAN node may use the RAN UE context ID (e.g., RAND UE ID) to identify the UE context in RAN 108. For each request, once validation is successfully completed, the serving RAN node may store the NF-UE identifier (e.g., SMS-S-TMSI, UEP-S-TMSI) and NAS type information (e.g., SMS, UEP) pair, and forward the NAS message to the UE 110. The UE may process the NAS message and store the NF-UE identifier and NAS type information to its NAS UE context at the UE NAS layer 318.

[0123] On receipt of an RRC message carrying a NAS message from the UE 110, the serving RAN node 202 at steps 412a, 412b uses the NAS type information (e.g., SMS, UEP) to identify the NF-UE identifier (e.g., SMS-S-TMSI, UEP-S-TMSI) of the UE in the CN 106, discover the address of the serving NFs 204 (e.g., SMSF, PCF). The serving RAN node may then send a message to each NF that includes the RAN-UE ID and the respective NF-UE identifier. Subsequent exchanges of messages between the serving RAN node and these NFs may include the RAN-UE ID and the respective NF-UE identifier.

[0124] FIGS. 5A and 5B illustrate a signaling chart 500 of a NAS sendee request procedure, UE-initiated for PDU session user-plane activation, according to some example impiememations. In some examples, it may be assumed that the UE 110 is in an idle state, and registered to the CN 106, and that the UE holds a RAN-UE ID (for a RAN UE context) issued by the previous serving RAN node 202. It may also be assumed that the UE has an established PDU session in the SM NF 510 (a NFx 208), and holds a SM. NF-UE identifier SM-GUTI (from which the SM-S-TMSI is derived) issued by SM NF. A secure NAS connection may have also been established between the UE and SM NF by the security context aKSI-1. The UE may also hold other NF-UE identifiers (e.g.. MM-S-TMSI) and security context identifiers (e.g., aKSI-2) for other types of established NAS connections.

[0125] As shown in FIG. 5A, a UE 110 at. step 501 issues a NAS sendee request, composed as an initial NAS message, for the activation of the user plane of an already established PDU session. The NAS service request may be carried in an RRC setup complete message to a selected saving RAN node 202. The RRC setup complete message may also include the RAN-UE ID, SM-S-TMSI and SM parameters, provided by the NAS layer 318 to the RRC layer 316 of the UE.

[0126] The new serving RAN node 202 at step 502 uses the RAN-UE ID to retrieve the UE’s RAN UE context stored in the RAN 108. The RAN set ID may be obtained from the RAN-UE ID and checked against the new serving RA N set. ID. If both are the same, the new serving RAN node may use the RAN UE context. ID (e.g., RAND UE ID) from the RAN-UE ID to retrieve the UE’s context.

[0127] If the RAN set ID’s are different, the new sewing RAN node 202 uses the RAN set ID from the RAN-UE ID to identify the old RAN nodes (and addresses) in the old RAN set. The new serving RAN node may select one of those discovered old RAN nodes and send a request, to the selected old RAN node, along with the UE’s context ID (e.g., RAND UE ID), requesting the UE’s RAN UE context information. The new serving RAN node may discover the serving RAN node address information (e.g., IP address / FQDN) by querying its local cache or an NRF using the RAN set ID from the RAN-UE ID as an input query' parameter. The selected old RAN node may, on successful validation of the request, return the RAN UE context information to the new sew ing RAN node and delete the RAN UE context. The new sewing RAN node may store the UE context in the new ILAN set. 101281 As the RAN-UE ID may have been exposed in the RRC setup complete message that is not encrypted, the serving RAN node 202 may assign the UE 110 a new RAN-UE ID, indicated as RAN-UE ID*, regardless of whether the serving RAN set ID differs from the previous serving RAN set ID. The new RAN-UE ID* may be provided encrypted to the UE later in the procedure to maintain protection for the identity of the UE. The new sewing RAN 108 may store the new RAN-UE ID* to the RAN UE context. The new sewing RAN node may now hold the RAN UE context information that includes the RAN-UE ID*, the old RAN-UE ID and NF-UE identifiers and associated NAS type information (e.g., SM: SM-S-TMSI, MM: MM-S-TMSI).

[0129] The new serving RAN node 202 at step 503 obtains the UE’s mobility management NAS type (MM) and NF-UE identifier (MM-S-TMSI) from the RAN UE, context, and uses this information to discover and select the serving MM NF 206. The RAN node may discover the serving MM NF address information (e.g., IP address / FQDN) by querying its local cache or an NRF using information from the NAS type and NF-UE identifiers as input query parameters. The new serving RAN node may subsequently notify the MM NF that the UE 110 is in an RRC connected state and that the UE’s RAN-UE ID has been updated to RAN-UE ID*. The MM NF may update its UE context to reflect the new RAN-UE ID* and RRC connected state.

[0130] The new serving R.AN node 202 at step 504 may use the session management NAS type (SM) and NF-UE identifier (SM-S-TMSI) received in the RRC setup complete message to discover and select the serving SM NF 510 in which the PDU session(s) is established. The RAN node may discover the serving SM NF address information (e.g., IP address / FQDN) by querying its local cache or an NRF using information from the NAS type and NF-UE identifiers as input query parameters. The new serving RAN node may subsequently forward the initial NAS message, containing the NAS service request, and the updated RAN-UE ID* to the selected SM NF.

[0131] As shown in FIG. 5B, the SM NF 510 performs SM-UPF procedures. The SM. NF at step 505 updates its UE context information with the RAN-UE ID* and trigger user plane resource procedures with UPF(s) to process the re-establishment of the user plane resources of the requested PDU session(s) in the CN 106. The SM NF may use the security context identifier (aKSI-1) received in the initial NAS message to validate the NAS service request. The SM NF may subsequently request that the serving RAN node 202 establish user plane resources for the allowed PDU session(s) in the RAN 108. The SM NF may use the RAN-UE ID* to identify the serving RAN node address, either from local cache or using an NRF. The SM. NF may send to the serving RAN node the RAN-UE ID* and the user plane resource request, which may piggyback a NAS service request accept message. The RAN-UE ID* and SM-S-TMSI may be used in communication between the RAN node and the SM NF.

[0132] The serving RAN node 202 at step 506 may use the received RAN-UE ID* to identify the UE’s context and cany out user plane resource allocation as per the request from SM NF 510. The serving RAN node may establish a secure RRC connection with the UE 110 using the RRC SMC procedure using as inputs the security parameters stored in the UE context (e.g., UE capabilities, next hop (NH) / next control channel (NCC) pair or security key KgNB), as well as the RAN nodes own security parameters such as prioritized integrity / ciphering algorithms.

[0133] After the secure RRC connection is established, the serving RAN node 202 may send an RRC reconfiguration request, piggybacking the NAS service request accept from the SM NF 510 and the new user plane resource configurations. The message may also include the RAN-UE ID* to inform the UE of the new RAN-UE ID* value. The UE RRC layer 316 may pass both the RAN-UE ID* and the NAS service request accept to the NAS layer 318. The UE NAS layer may update the stored RAN-UE ID with RAN-UE ID*. The UE may use the security context identifier (aKSI-1) received in the NAS service request accept message to validate the NAS message.

[0134] The UE 110 at step 507 returns an RRC reconfiguration complete response to the serving RAN node 202, which may in turn send a response to the SM NF 510 indicating the outcome of the user plane resource request. The RAN-UE ID* and SM-S-TMSI may be used in communication between the serving RAN node and the SM NF. The SM NF may trigger user plane resource procedures with UPF(s) to update on outcome of request with RAN. If number of user plane established is less than requested (but not zero), the SM NF may trigger a PDU session modification procedure with UE.

[0135] FIGS. 6A, 6B and 7 illustrate signaling charts 600, 700 of a NAS sendee request procedure, network-initiated by a SMSF 610 to send a mobile terminated (MT) SMS message to the UE, according to some example implementations. In some examples, it may be assumed that the UE 110 is registered to the registered to the CN 106. It may also be assumed that the UE holds a RAN-UE ID assigned by the previous serving RAN node 202, and that the UE holds NAS types and NF-UE identifiers. Also, the SMSF is unaware whether the UE is in idle or inactive / connected state, and unaware of the latest RAN-UE II) of the UE.

[0136] As shown in FIG. 6A, in a scenario A in which the UE 110 is in the idle state, the SMSF 610 at. step 601 initiates a MT SMS delivery by requesting that the MM NF 206 provide the RAN-UE ID of the UE 110 when it is in an inactive or connected state. The SMSF may also subscribe to the MM NF to receive UE MT reachability notifications. If the UE 110 is in idle state, the MM NF 206 at step 602 pages the UE using the MM-S-TMSI. In some examples, the paging message includes one or more of the RAN-UE ID, the MM-S-TMSI, or the SMS-S-TMSI.

[0137] The UE 110 at step 603 sets up an RRC connection and provides its RAN-UE ID, MM and MM-S-TMSI to the serving RAN node 202. The serving RAN node at step 604 uses the RAN-UE ID to retrieve the UE’s RAN UE context from the previous serving RAN set (which may be the same or different from the current serving RAN set), as described above with respect to the UE-initiated NAS service request.

[0138] Regardless of whether the serving RAN set ID differs from the previous serving RAN set ID, the serving RAN node 202 may assign the UE 110 a new RAN-UE ID* (later provided encrypted to the UE). The serving RAN node may at step 605 send a notification to the MM NF 206 (identified from the MM and MM-S-TMSi' identifiers received from the UE) containing the updated RAN-UE ID* and an indication the UE is in the RRC connected state.

[0139] The MM NF 206 at step 606 responds to the SMSF request by providing the RAN-UE ID* and an indication the UE 110 is in the RRC connected state. And the SMSF 610 may update its UE context with RAN-UE ID*.

[0140] As shown in FIG. 6B, in a scenario B in which the LIE 110 is in the inactive / connected state, similar to scenario A, the SMSF 610 initiates a MT SMS delivery at step 601’ by requesting that the MM NF 206 provide the RAN-UE ID of the UE IIO when it is in an inactive or connected state. The MM NF 206 at step 602’ responds to the SMSF 610 request by providing the RAN-UE ID* and an indication the UE 110 is in the RRC inactive / connected state. And the SMSF updates its UE context with RAN-UE ID*.

[0141] In a scenario C in which the SMSF 610 has subscribed to UE MT reachability notifications, the MM NF 206 at step 601” notifies the SMSF by providing the RAN-UE ID* and an indication the UE 110 is in the RRC inactive / connected state. The SMSF updates its UE context with RAN-UE ID*.

[0142] In the signaling chan 700 in FIG. 7, it may be assumed that the SMSF 610 has received a response / notification from the MM NF 206 that indicates the UE 110 is connected state, and that its RAN UE context in RAN is RAN-UE ID*. The SMSF at step 701 uses the RAN-UE ID* to discover the UE’s serving RAN node ID and uses local cache or the services of an NRF to provide the RAN node ID address information (e.g., IP address / FQDN). SMSF then sends a message to the serving RAN node 202 requesting the delivery of a NAS message, containing a SMS deliver message, to the UE. The NAS message may be secured using the NAS security context identified by aKSL-2. The SMSF may include the RAN-UE ID*, SMS and SMS-S-TMSI parameters in the message sent to the serving RAN node, and the serving RAN node may store to the RAN UE context, identified by RAN-UE ID*, the SMS and SMS-S-TMSI information,

[0143] The serving RAN node 202 at step 702 triggers establishment of a secure RRC connection with the UE 110 if one is not already established. The serving RAN node may establish a secure RRC connection with the UE using the RRC SMC procedure using as inputs the security parameters stored in the UE context (e.g., UE capabilities, NH / NCC pair or KgNB) as well as the serving RAN node’s own security parameters such as prioritized integrity / ciphering algorithms.

[0144] After the RRC connection is secured, the serving RAN node 202 at. step 703 includes the RAN-UE ID* and NAS message (SMS deliver) in an RRC message, and sends the RRC message to the UE 110.

[0145] The UE 110 at step 704 passes the RAN-UE ID* and NAS message to its NAS layer 318. The UE may store the RAN-UE ID to its NAS context and uses the aKSI-2 security context identifier to validate the received NAS message (SMS deliver). The UE may send a NAS message (control plane acknowledge - CP Ack) to the SMSF to acknowledge the successful receipt of the SMS deliver message. The UE may also provide its RRC layer 316 with the NAS type SMS.

[0146] The serving RAN node 202 at step 705 may use the NAS type SMS in the received RRC message to identify (from the RAN UE context), the NF-UE identifier assigned by the SMSF (SMS-S-TMSI). From this information, the serving RAN node may discover the SMSF’s address information (e.g., IP address / FQDN) by using a local cache or the services of an NRF. The serving RAN node includes the RAN-UE ID*, SMS-S-TMSI and the NAS Message (CP Ack) in the message sent to the SMSF.

[0147] In some examples, it may be the case that the serving RAN node 202 fails to deliver the NAS message to the UE 110. If the serving RAN node recei ves a request to deliver a. NAS message to the UE, and the RAN node is unable to complete the request, the RAN node may at step 701’ send a NAS non-delivery notification to the SMSF 610 that originated the request. The serving RAN node may use the NF-UE identifier received in the request (SMS-S-TMSI) to determine the SMSF’s address information (e.g., IP address / FQDN) by using a local cache or the services of an NRF. The serving RAN node may include the RAN-UE ID* and SMS-S-TMSI in the NAS non-delivery' notification message sent to the SMSF,

[0148] FIGS. 8A - 8D are flowcharts illustrating various steps in a method 800 implemented by an access node (a RAN node), according to various example implementations. The method includes establishing a RAN UE context associated with a UE served by the access node of an access node set within a RAN, as shown at block 802 of FIG. 8 A. The method includes assigning a RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, as shown at block 804. The method includes storing the RAN-UE identifier in the RAN UE context, as shown at block 806. And the method includes providing the RAN-UE identifier to a CN to enable NFs of the CN to invoke services of the RAN for the UE based on the RAN-UE identifier, as shown at block 808.

[0149] In some examples, the method 800 further includes receiving a NAS message for the UE from a NF of the NFs, where the NAS message is carried in a transport request message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF, as shown at block 810 of FIG. 8B. In some of these examples, the method also includes accessing the RAN UE context based on the RAN-UE identifier, as shown at block 812. The method includes storing the NF-UE identifier in the RAN UE context, and sending the NAS message to the UE, as shown at blocks 814 and 816.

[0150] In some examples, the NF-UE identifier stored in the RAN UE context is associated with NAS type information that indicates a type of the NF.

[0151] In some examples, the NFs comprise a NF, and a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context. In some of these examples, the method 800 further includes receiving a NAS message for the NF from the UE, where the NAS message is carried in an information transfer message that comprises NAS type information that indicates a type of the NF, as shown at block 818 of FIG. 8C. The method includes identifying the NF-UE identifier stored in the RAN UE context based on the NAS type information, as shown at block 820. And the method includes sending the NAS message to the NF, the NAS message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier, as shown at block 822.

[0152] In some examples, the RAN UE identifier is assigned at block 804 during a registration procedure of the UE with the CN, wherein the registration procedure is initiated during setup of a radio resource control (RRC) connection with the UE. In some of these examples, the method further includes performing a security activation procedure with the UE to activate security for RRC messages between the UE and the access node, as shown at block 824 of FIG. 8D. Also in some of these examples, the RAN-UE identifier is provided to the UE in a secured RRC message, as shown at block 826.

[0153] FIGS. 9A - 9D are flowcharts illustrating various steps in a method 900 implemented by a NF of a CN, according to various example implementations. The method includes receiving a RAN-UE identifier assigned to a UE served by an access node (a RAN node) of an access node set within a RAN, where the RAN-UE identifier comprises an access node set identifier, an access node identifier, and an identifier of the RAN UE context, as shown at block 902 of FIG. 9A. The method includes assigning a NF-UE identifier to the UE, as shown at block 904. The method includes storing the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF, as shown at block 906. And the method includes invoking one or more services of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier, as shown at block 908.

[0154] In some examples, invoking the one or more services at block 908 includes determining the access node in the access node set based on the access node set identifier and the access node identifier, as shown at block 910 of FIG. 9B. In some of these examples, invoking the one or more services also includes sending a NAS message for the UE to the access node as determined, where the NAS message is carried in a transport request message that also comprises the RAN-UE identifier and the NF-UE identifier, as shown at block 912.

[0155] In some examples, the method 900 further includes receiving a NAS message from the UE, where the NAS message is carried in an information transfer message from the access node that also comprises the RAN-UE identifier and the NF-UE identifier, as shown at block 914 of FIG. 9C. In some of these examples, the method also includes determining the access node and RAN UE context based on the RAN-UE identifier, as shown at block 916. And the method includes identifying the NF UE context based on the NF-UE identifier, as shown at block 918.

[0156] In some examples, the method 900 further includes discovering other NFs of the CN, as shown at block 920 of FIG. 9D. In somd of these examples, the method also includes providing the RAN-UE identifier to the other NFs to enable the other NFs to invoke services of the RAN for the UE based on the RAN-UE identifier, as shown at block 922.

[0157] FIGS. 10A - 10E are flowcharts illustrating various steps in a method 1000 implemented by a UE, according to various example implementations. The method includes initiating a registration procedure with a CN, during setup of a radio resource control (RRC) connection with an access node (a RAN node) of an access node set within a RAN, and in which a RAN UE context associated with the UE within the RAN is established, as shown at block 1002 of FIG. 10A. The method includes receiving an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, as shown at block 1004. The RAN-UE identifier is also provided to NFs of the CN to enable the NFs invoke services of the RAN for the UE based on the RAN-UE identifier. And the method includes storing the RAN-UE identifier in at least one UE context that is maintained independent of an RRC state of the UE, as shown at block 1006.

[0158] In some examples, the method 1000 further includes performing a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, as shown at block 1008 of FIG. 10B. In some of these examples, the RRC message that comprises the RAN-UE identifier is a secured RRC message.

[0159] In some examples, storing the RAN-UE identifier at block 1006 includes the RAN-UE identifier in an RRC UE context at an RRC layer, as shown storing at block 1010 of FIG. 10C. In some of these examples, storing the RAN-UE identifier also includes passing the RAN-UE identifier from the RRC layer to a NAS layer at which the RAN-UE identifier is stored in a NAS UE context, as shown at block 1012.

[0160] In some examples, the NFs comprise a NF, and a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context. In some of these examples, the method 1000 further includes sending a NAS message for the NF to the access node, where the NAS message carried in an information transfer message that comprises NAS type information that indicates a type of the NF, and based on which the NF-UE identifier stored in the RAN UE context is identifiable, as shown at block 1014 of FIG. 10D.

[0161] In some examples, the method 1000 further includes sending the RAN-UE identifier to the RAN to enable access to the RAN UE context based on the RAN-UE identifier independent of the RRC state of the UE, as shown at block 1016 of FIG. 10E.

[0162] In some examples, the RAN-UE identifier is sent to the RAN at block 1016 by the UE in an RRC idle state; and in some of these examples, the RAN-UE identifier is sent during setup or reestablishment of an RRC connection with the RAN.

[0163] FIGS. 11A - 1 ID are flowcharts illustrating various steps in a method 1100 implemented by an access node (a RAN node), according to various example implementations. The method includes receiving a NAS service request message from a UE served by the access node of an access node set within a RAN, as shown at block 1102 of FIG. 11 A. The NAS service request message is for a NF of a CN, and the NAS service request message is carried in an unsecured message that also comprises a RAN-UE identifier assigned to the UE. The method includes accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier, as shown at block 1104. The method includes assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, as shown at block 1106. The method includes storing the new RAN-UE identifier in the RAN UE context, as shown at block 1108. And the method includes sending the NAS service request message to the NF, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier, as shown at block 1110

[0164] In some examples, the CN includes a MM NF, and a NF-UE identifier assigned to the UE by the MM NF is stored in the RAN UE context. In some of these examples, the method 1100 further includes identifying at the NF-UE identifier stored in the RAN UE context, as shown block 1112 of FIG. 1 IB. The method also includes determining the MM NF based on the NF-UE identifier, as shown at block 1114. And the method includes sending a notification message to the MM NF that comprises the new RAN-UE identifier and the NF-UE identifier, as shown at block 1116.

[0165] In some examples, the NF is a SM NF, and the NAS service request message is for activation of a user plane for an established one or more packet data unit sessions of the UE in the SM NF. In some of these examples, the NAS service request message comprises a NF-UE identifier assigned to the UE by the SM NF, and the NAS message is carried in the notification message that also comprises the NF-UE identifier.

[0166] In some examples, the method 1100 further includes receiving a NAS service request accept message for the UE, where the NAS service request accept message is carried in a resource request message from the SM NF, as shown at block 1118 of FIG. 1 IC. In some of these examples, the method includes allocating user plane resources for the one or more packet data unit sessions based on the resource request message, as shown at block 1120.

[0167] In some examples, the method 1100 further includes sending the NAS service request accept message to the UE, where the NAS service request accept message is carried in a message that also comprises the new RAN-UE identifier, as shown at block 1122 of FIG. 11D.

[0168] FIGS. 12A - 12C are flowcharts illustrating various steps in a method 1200 implemented by a UE, according to various example implementations. The method includes initiating a NAS service request procedure towards a NF of a CN by sending a NAS service request message to an access node (a RAN node) of an access node set within a RAN, as shown at block 1202 of FIG. 12A. The NAS service request message is sent during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE. The method includes receiving an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, as shown at block 1204. The new RAN-UE identifier comprises an access node set identifier, an access node identifier, and an identifier of the RAN UE context. The new RAN-UE identifier is also provided to NFs of a CN to enable the NFs invoke services of the RAN for the UE based on the RAN-UE identifier. And the method includes storing the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE, as shown at block 1206.

[0169] In some examples, the NAS service request procedure is for activation of a user plane of an established one or more packet data unit sessions of the UE in a SM NF of the CN. In some of these examples, the NAS service request message comprises a NF-UE identifier assigned to the UE by the SM NF.

[0170] In some examples, the method 1200 further includes performing a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, as shown at block 1208 of FIG. 12B. In some of these examples, the RRC message that comprises the new RAN-UE identifier is a secured RRC message.

[0171] In some examples, storing the RAN-UE identifier at block 1206 includes storing the new RAN-UE identifier in an RRC UE context at an RRC layer, as shown at block 1210 of FIG. 12C. In some of these examples, storing the RAN-UE identifier also includes assing the new RAN-UE identifier from the RRC layer to a NAS layer at which the new RAN-UE identifier is stored in a NAS UE context, as shown at block 1212.

[0172] FIGS. 13A - 13D are flowcharts illustrating various steps in a method 1300 implemented by a NF of a CN, according to various example implementations. The method includes accessing a NF UE context associated with a UE at the NF, the NF UE context comprising a RAN - UE identifier assigned to the UE served by an access node (a RAN node) of an access node set within a RAN, as shown at block 1302 of FIG. 13 A. The RAN-UE identifier comprises an access node set identifier, an access node identifier, and an identifier of a RAN UE context associated with the UE within the RAN. The method includes determining the access node in the access node set based on the access node set identifier and the access node identifier, as shown at block 1304. And the method includes initiating a NAS service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF, as shown at block 1306.

[0173] In some examples, the method 1300 further includes sending a reachability request message relating to the UE to a MM NF of the CN, as shown at block 1308 of FIG. 13B. In some of these examples, the method also includes receiving a reachability response message from the MM NF, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state, as shown at block 1310.

[0174] In some examples, the NF has a subscription to reachability notifications relating to the UE. In some of these examples, the method 1300 further includes receiving a reachability notification message from a MM NF based on the subscription, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state, as shown at block 1312 of FIG. 13C.

[0175] In some examples, the method 1300 further includes receiving a NAS service request response message from the access node, as shown at block 1314 of FIG. 13D. In some of these examples, the NAS service request response message is carried in a transport message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0176] FIGS. 14AI4G are flowcharts illustrating various steps in a method 1400 implemented by an access node (a RAN node), according to various example implementations. The method includes receiving a NAS service request message relating to a UE served by the access node of an access node set within a RAN, as shown at block 1402 of FIG. 14A. The NAS service request message is received from a NF of a CN, and the NAS service request message is carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF. The method includes accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier, as shown at block 1404. The method includes storing the NF-UE identifier in the RAN UE context, as shown at block 1406. And the method includes processing the NAS service request message, as shown at block 1408.

[0177] In some examples, the method 1400 further includes forwarding a paging message comprising the NF-UE identifier to the UE in a radio resource control (RRC) idle state to trigger establishment of an RRC connection, as shown at block 1410 of FIG. 14B. In some of these examples, the method also includes performing a radio resource control (RRC) connection setup procedure with the UE during which the RAN-UE identifier is received from the UE, as shown at block 1412. Also in some of these examples, the method includes accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier, as shown at block 1414.

[0178] In some examples, the RAN-UE identifier is received from the UE in an unsecured RRC message. In some of these examples, the method 1400 further includes assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, as shown at block 1416 of FIG. 14C. And the method includes storing the new RAN-UE identifier in the RAN UE context, as shown at block 1418.

[0179] In some examples, processing the NAS service request message at block 1408 includes sending the NAS service request message to the UE, where the NAS service request message carried in an information transfer message that also comprises the RAN-UE identifier, as shown at block 1420 of FIG. 14D.

[0180] In some examples, the method 1400 further includes performing a security activation procedure with the UE to activate security for radio resource control (RRC) messages between the UE and the access node, as shown at block 1422 of FIG. 14E. In some of these examples, the information transfer message in which the NAS service request message is carried, and that also comprises the RAN-UE identifier, is a secured RRC message.

[0181] In some examples, the method 1400 further includes receiving a NAS service request accept message for the NF from the UE, where the NAS service request accept message is carried in an information transfer message that comprises NAS type information that indicates a type of the NF, as shown at block 1424 of FIG. 14F. In some of these examples, the method includes identifying the NF-UE identifier stored in the RAN UE context based on the NAS type information, as shown at block 1426. Also m some of these examples, the the method includes sending the NAS service request accept message to the NF, the NAS service request accept message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier, as shown at block 1428.

[0182] In some examples, processing the NAS service request message at block 1408 includes making a determination that the access node is unable to send the NAS service request message to the UE, as shown at block 1430 of FIG. 14G.. In some of these examples, based on the determination, processing the NAS service request message also includes sending a non-delivery notification message to the NF, the non-delivery notification message comprising the RAN-UE identifier and the NF-UE identifier, as shown at block 1432.

[0183] FIGS. 15A - 15H are flowcharts illustrating various steps in a method 1500 implemented by a UE, according to various example implementations. The method includes receiving a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node (a RAN node) of a RAN, as shown at block 1502 of FIG. 15 A. The method includes identifying a RAN-UE identifier in the RRC paging message, as shown at block 1504. The method includes passing the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a NAS layer, as shown at block 1506. The method includes receiving a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters, as shown at block 1508. And the method includes performing an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier, as shown at block 1510.

[0184] In some examples, the request from the NAS layer includes the RAN-UE identifier, and the method 1500 further includes accessing an RRC UE context at the RRC layer based on the RAN-UE identifier, as shown at block 1512 of FIG. 15B. In some of these examples, the RRC connection procedure is performed at block 1510 based on the RRC UE context.

[0185] In some examples, the method 1500 further includes determining the RRC UE context excludes a security context, as shown at block 1514 of FIG. 15C. In some of these examples, the RRC connection procedure that is performed at block 1510 is an RRC connection setup procedure.

[0186] In some examples, the method 1500 further includes determining the RRC UE context includes a security context, and In some of these examples, the RRC connection procedure that is performed at block 1510 is an RRC connection reestablishment procedure to which the security context is applied, as shown at block 1516 of FIG. 15D.

[0187] In some examples, the RRC connection procedure is performed at block 1510 further based on a time duration of the UE in the RRC idle state.

[0188] In some examples, the method 1500 further includes determining the time duration of the UE in the RRC idle state exceeds a threshold duration, as shown at block 1516 of FIG. 15E. In some of these examples, the RRC connection procedure that is performed at block 1510 is an RRC connection setup procedure.

[0189] In some examples, the method further includes determining the RRC UE context includes a security context, and the time duration of the UE in the RRC idle state does not exceed a threshold duration, as shown at block 1518 of FIG. 15F. In some of these examples, the RRC connection procedure that is performed at block 1510 is an RRC connection reestablishment procedure to which the security context is applied.

[0190] In some examples, the method 1500 further includes determining the UE has moved mto a different tracking area code broadcast by the RAN. as shown at block 1520 of FIG. 15G. In some of these examples, the RRC connection procedure that is performed at block 1510 is an RRC connection setup procedure.

[0191] In some examples, the method further includes determining the UE has not moved into a different tracking area code broadcast by the RAN, that the RRC UE context includes a security context, and the time duration of the UE in the RRC idle state does not exceed a threshold duration, as shown at block 1522 of FIG. I5H. In some of these examples, the RRC connection procedure that is performed at block 1510 is an RRC connection reestablishment procedure to which the security context is applied.

[0192] According to example implementations of the present disclosure, a telecommunications system 100 or PLMN 102, and its components such as a UE 110, CN 106, RAN 108, RAN node 202, NFs 204, MM NF 206, NFx 208, DU 210 and / or CU 212, may be implemented by various means. Means for implementing the system and its components may include hardware, firmware, software, or combinations thereof. In some examples, one or more apparatuses may be configured to function as or otherwise implement the system and its components shown and described herein. In examples involving more than one apparatus, the respective apparatuses may be connected to or otherwise in communication with one another m a number of different manners, such as directly or indirectly via a wired or wireless network or the like.

[0193] According to some example implementations, at least some of the methods 800, 900, 1000, 1100, 1200, 1300, 1400 and 1500 described with respect to FIGS. 8A-8D, 9A-9D, lOA-iOE, HA-UD, 12A-12C, 13A-13D, 14A-14G, I5A-15H may be carried out by one or more apparatuses comprising means for performing functions corresponding steps of the methods. Examples of a suitable apparatus may include a gNB (e.g., gNB-DU, gNB-CU), ng-eNB, NF or any suitable apparatus, such as a server, host or node. Other examples of a suitable apparatus may include a user equipment, user device, user terminal or the like.

[0194] FIG. 16 illustrates an apparatus 1600 in which means for performing various functions includes hardware, alone or under direction of one or more computer programs from a computer-readable storage medium or other memory, such as computer memory, according to some example implementations of the present disclosure. Generally, an apparatus of example implementations of the present disclosure may comprise, include or be embodied in one or more fixed or portable electronic devices. Examples of suitable electronic devices include a wearable computer, mobile phone, portable computer, desktop computer, workstation computer, server (server computer) or the like. The apparatus may include one or more of each of a number of components such as, for example, processing circuitry 1602 connected to computer-readable storage medium or other memory 1604.

[0195] The processing circuitry 1602 may be composed of one or more processors alone or in combination with one or more computer-readable storage media. The processing circuitry is generally any piece of computer hardware that is capable of processing information such as, for example, data, computer programs and / or other suitable electronic information. The processing circuitry is composed of a collection of electronic circuits some of which may be packaged as an integrated circuit or multiple interconnected integrated circuits (an integrated circuit at times more commonly referred to as a “chip”). The processing circuitry may be configured to execute computer programs, which may be stored onboard the processing circuitry or otherwise stored in the memory 1604 (of the same or another apparatus).

[0196] The processing circuitry 1602 may be a number of processors, a multi-core processor or some other type of processor, depending on the particular implementation. Further, the processing circuitry may be implemented using a number of heterogeneous processor systems in which a main processor is present with one or more secondary processors on a single chip. As another illustrative example, the processing circuitry may be a symmetric multi-processor system containing multiple processors of the same type. In yet another example, the processing circuitry may be embodied as or otherwise include one or more ASICs, FPGAs or the like. Thus, although the processing circuitry may be capable of executing a computer program to perform one or more functions, the processing circuitry of various examples may be capable of performing one or more functions without the aid of a computer program. In either instance, the processing circuitry may be appropriately programmed to perform functions or operations according to example implementations of the present disclosure.

[0197] The memory 1604 is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs, instructions 1606 (e.g., computer-readable program code) and / or other suitable information either on a temporary basis and / or a permanent basis. The memory may include volatile and / or nonvolatile memory, and may be fixed or removable. Examples of suitable memory include recording media, random access memory (RAM), read-only memory (ROM), a hard drive, a flash memory, a thumb drive, a removable computer diskette, an optical disk or some combination thereof.

[0198] The memory 1604 is a non-transitory device capable of storing information. One example of a suitable memory is a computer-readable storage medium, which is distinguishable from a computer-readable transmission medium capable of carrying information from one location to another. Examples of suitable computer-readable transmission media comprise electronic carrier signals, telecommunications signals, software distribution packages, or some combination thereof. As used herein, the term “non-transitory” is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM versus ROM). A computer-readable medium as described herein generally refers to a computer-readable storage medium or computer-readable transmission medium. A computer-readable medium is any entity or device capable in which information, such as one or more computer programs or portions thereof, may be stored and carried.

[0199] In addition to the memory 1604 (e.g., computer-readable storage medium), the processing circuitry 1602 may also be connected to one or more interfaces for displaying, transmitting and / or receiving information. The interfaces may include a communications interface 1608 and / or one or more user interfaces. The communications interface may be configured to transmit and / or receive information, such as to and / or from other apparatus(es), network(s) or the like. The communications interface may be configured to transmit and / or receive information by physical (wired) and / or wireless communications links. Examples of suitable communication interfaces include a network interface controller (NIC), wireless NIC (WNIC) or the like.

[0200] The user interfaces may include a display 1610 and / or one or more user input interfaces 1612. The display may be configured to present or otherwise display information to a user, suitable examples of which include a liquid crystal display (LCD), light-emitting diode (LED) display, organic LED (OLED) display, active-matrix OLED (AMOLED) or the like. The user input interfaces may be wired or wireless, and may be configured to receive information from a user into the apparatus, such as for processing, storage and / or display. Suitable examples of user input interfaces include a microphone, image or video capture device, keyboard or keypad, joystick, touch-sensitive surface (separate from or integrated into a touchscreen), biometric sensor or the like. The user interfaces may further include one or more interfaces for communicating with peripherals such as printers, scanners or the like.

[0201] Execution of the instructions 1606 by the processing circuitry 1602, or storage of the instructions in the memory 1604, supports combinations of operations for implementing example implementations of the present disclosure. In this manner, an apparatus 1600 may comprise at least one processing circuitry and at least one memory coupled to the at least one processing circuitry, where the at least one processing circuitry is configured to execute instructions stored in the at least one memory. It will also be understood that one or more functions, and combinations of functions, may be implemented by special purpose hardware-based computer systems and / or processing circuitry which perform the specified functions, or combinations of special purpose hardware and program code instructions.

[0202] Some example implementations of the present disclosure may also be carried out in the form of a computer process defined by one or more computer programs or portions thereof. Example implementations of the present disclosure may be carried out by executing at least one portion of a computer program comprising instructions. The computer program may be in source code form, object code form, or in some intermediate form. The computer program may be stored in a computer-readable medium that is readable by a computer, processing circuitry or other suitable apparatus. As indicated above, for example, the computer program may be stored in a memory, such as a computer-readable storage medium. Additionally or alternatively, for example, the computer program may be stored in a computer-readable transmission medium. The coding of software for carrying out example implementations of the present disclosure is well within the scope of a person of ordinary skill in the art.

[0203] As will be appreciated, any suitable instructions may be loaded onto a computer, a processing circuitry or other programmable apparatus from a memory or a computer-readable medium (e.g., computer-readable storage medium, computer-readable transmission medium) to produce a particular machine, such that the particular machine becomes a means for implementing the functions specified herein. The instructions may also be stored in a computer-readable medium that can direct a computer, a processing circuitry or other programmable apparatus to function in a particular manner to thereby generate a particular machine or particular article of manufacture. In some examples, the instructions stored in the computer-readable medium may produce an article of manufacture, where the article of manufacture becomes a means for implementing functions described herein. The instructions may be retrieved from a computer-readable medium and loaded into a computer, processing circuitry or other programmable apparatus to configure the computer, processing circuitry or other programmable apparatus to execute operations to be performed on or by the computer, processing circuitry or other programmable apparatus.

[0204] Retrieval, loading and execution of instructions comprising program code instructions may be performed sequentially such that one instruction is retrieved, loaded and executed at a time. In some example implementations, retrieval, loading and / or execution may be performed in parallel such that multiple instructions are retrieved, loaded, and / or executed together. Execution of the program code instructions may produce a computer-implemented process such that the instructions executed by the computer, processing circuitry or other programmable apparatus provide operations for implementing functions described herein.

[0205] As explained above and reiterated below, the present disclosure includes, without limitation, the following example implementations.

[0206] Clause 1. An apparatus to implement an access node, the apparatus comprising, at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: establish a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN; assign a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the RAN-UE identifier in the ILAN UE context; and provide the RAN-UE identifier to a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0207] Clause 2. The apparatus of clause 1, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: receive a non-access stratum (N AS) message for the UE from a network function (NF) of the network functions, the NAS message carried in a transport request message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF, access the RAN UE context based on the RAN-UE identifier; store the NF-UE- identifier in the RAN UE context; and send the NAS message to the UE.

[0208] Clause 3. The apparatus of clause 2, wherein the NF-UE identifier stored in the RAN UE context is associated with NAS type information that indicates a type of the NF.

[0209] Clause 4. The apparatus of any of clauses I to 3, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the at least one processing circuitry' is configured to execute the instructions to cause the apparatus to further at least: receive a non-access stratum (NAS) message for the NF from the UE, the NAS message carried in an information transfer message that comprises NAS type information that indicates a type of the NF; identify the NF-UE identifier stored in the RAN UE context based on the NAS type information; and send the NAS message to the NF. the NAS message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0210] Clause 5. The apparatus of any of clauses 1 to 4, wherein the RAN UE identifier is assigned during a registration procedure of the UE with the core network, wherein the registration procedure is initiated during setup of a radio resource control (RRC) connection with the UE, and the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: perform a security' activation procedure with the UE to activate security for RRC messages between the UE and the access node; and provide trie RAN-UE identifier to the UE in a secured RRC message.

[0211] Clause 6. An apparatus to implement an access node, the apparatus comprising: means for establishing a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN; means for assigning a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; means for storing the RAN-UE identifier in the RAN UE context, and means for providing the RAN-UE identifier io a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0212] Clause 7, The apparatus of clause 6, wherein the apparatus further comprises: means for receiving a non-access stratum (NAS) message for the UE from a network function (NF) of the network functions, the NAS message carried in a transport request message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF, means for accessing the RAN UE context based on the RAN-UE identifier, means for storing the NF-UE identifier in the RAN UE context; and means for sending the NAS message to the UE.

[0213] Clause 8. The apparatus of clause 7, wherein the NF-UE identifier stored in the RAN UE context is associated with NAS type information that indicates a type of the NF.

[0214] Clause 9. The apparatus of any of clauses 6 to 8, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the apparatus further comprises: means for receiving a non-access stratum (NAS) message for the NF from the UE, the NAS message carried in an information transfer message that comprises NAS type information that indicates a type of the NF, means for identifying the NF-UE identifier stored m the RAN UE context based on the NAS type information; and means for sending the NAS message to the NF, the N AS message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0215] Clause 10. The apparatus of any of clauses 6 to 9, wherein the RAN UE identifier is assigned during a registration procedure of the UE with the core network, wherein the registration procedure is initiated during setup of a radio resource control (RRC) connection with the UE, and the apparatus further comprises: means for performing a security activation procedure with the UE to activate security for RRC messages between the UE and the access node; and means for providing the RAN-UE identifier to the UE in a secured RRC message.

[0216] Clause 11. A method implemented by an access node, the method comprising: establishing a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN, assigning a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; storing the RAN-UE identifier in the RAN UE context, and providing the RAN-UE identifier to a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0217] Clause 12. The method of clause 11, wherein the method further comprises: receiving a non-access stratum (NAS) message for the UE from a network function (NF) of the network functions, the NAS message carried in a transport request message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF; accessing the RAN UE context based on the RAN-UE identifier; storing the NF-UE identifier in the RAN UE context, and sending the NAS message to the UE.

[0218] Clause 13. The method of clause 12, wherein the NF-UE identifier stored in the RAN UE context is associated with NAS type information that indicates a type of the NF.

[0219] Clause 14. The method of any of clauses 11 to 13, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the method further comprises: receiving a non-access stratum (NAS) message for the NF from the UE, the NAS message carried in an information transfer message that comprises NAS type information that indicates a type of the NF; identifying the NF-UE identifier stored in the RAN UE context based on the NAS type information; and sending the NAS message to the NF, the NAS message carried m a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0220] Clause 15. The method of any of clauses 11 to 14, wherein the RAN UE identifier is assigned during a registration procedure of the UE with the core network, wherein the registration procedure is initiated during setup of a radio resource control (R.RC) connection with the U'E, and the method further comprises: performing a security activation procedure with the UE to activate security for RRC messages between the UE and the access node; and providing the RAN-UE identifier to the UE in a secured RRC message.

[0221] Clause 16. A computer-readable storage medium implemented at an access node, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: establish a radio access network (RAN) user equipment (UE) context associated with a UE served by the access node of an access node set within a RAN, assign a RAN-UE identifier to the UE, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the RAN-UE identifier in the RAN UE context, and provide the RAN-UE identifier to a core network to enable network functions of the core network to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0222] Clause 17. The computer-readable storage medium of clause 16, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: receive a non-access stratum (NAS) message for the UE from a network, function (NF) of the network functions, the NAS message carried in a transport request message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF; access the RAN UE context based on the RAN-UE identifier; store the NF-UE identifier in the RAN UE context, and send the NAS message to the UE.

[0223] Clause 18. The computer-readable storage medium of clause 17, wherein the NF-UE identifier stored in the RAN UE context is associated with NAS type information that indicates a type of the NF.

[0224] Clause 19. The computer-readable storage medium of any of clauses 16 to 18, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: receive a non-access stratum (NAS) message for the NF from the UE, the NAS message earned in an information transfer message that comprises NAS type information that indicates a type of the NF; identify the NF-UE identifier stored in the RAN UE context based on the NAS type information; and send the NAS message to the NF, the NAS message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0225] Clause 20. The computer-readable storage medium of any of clauses 16 to 19, wherein the RAN UE identifier is assigned during a registration procedure of the UE with the core network, wherein the registration procedure is initiated during setup of a radio resource control (RRC) connection with the UE, and the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: perform a security activation procedure with the UE to activate security for RRC messages between the UE and the access node; and provide the RAN-UE identifier to the UE in a secured RRC message.

[0226] Clause 21. An apparatus comprising means for performing the method of any of clauses 11 to 15.

[0227] Clause 22. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 11 to 15.

[0228] Clause 23. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses II to 15.

[0229] Clause 24. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 11 to 15.

[0230] Clause 25. An apparatus to implement a network function (NF) of a core network, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a radio access network (RAN) - user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; assign a NF-UE identifier to the UE; store the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE. at the NF; and invoke one or more services of the RAN for the UE based on the RAN-UE. identifier and the NF-UE identifier.

[0231] Clause 26. The apparatus of clause 25, wherein the apparatus caused to invoke the one or more services comprises the apparatus caused to: determine the access node in the access node set based on the access node set identifier and the access node identifier; and send a non-access stratum (NAS) message for the UE to the access node as determined, the NAS message carried in a transport request message that also comprises the R.AN-UE identifier and the NF-UE identifier.

[0232] Clause 27. The apparatus of clause 25 or clause 26, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: receive a non-access stratum (NAS) message from the UE, the NAS message carried in an information transfer message from the access node that also comprises the RAN-UE identifier and the NF-UE identifier, determine the access node and RAN UE context based on the RAN-UE identifier; and identify the NF UE context based on the NF-UE identifier.

[0233] Clause 28. The apparatus of tiny of clauses 25 to 27, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: discover other NFs of the core network; and provide the RAN-UE identifier to the other NFs to enable the other NFs to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0234] Clause 29. An apparatus to implement a network function (NF) of a core network, the apparatus comprising: means for receiving a radio access network (RAN) -user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; means for assigning a NF-UE identifier to the UE; means for storing the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF; and means for invoking one or more services of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier.

[0235] Clause 30. The apparatus of clause 29, wherein the means for invoking the one or more services comprises: means for determining the access node in the access node set based on the access node set identifier and the access node identifier; and means for sending a non-access stratum (NAS) message for the UE to the access node as determined, the NAS message carried in a transport request message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0236] Clause 31. The apparatus of clause 29 or clause 30, wherein the apparatus further comprises: means for receiving a non-access stratum (NAS) message from the UE, the NAS message carried in an information transfer message from the access node that also comprises the RAN-UE identifier and the NF-UE identifier, means for determining the access node and RAN UE context based on the R / XN-UE identifier; and means for identifying the NF UE context based on the NF-UE identifier.

[0237] Clause 32. The apparatus of any of clauses 29 to 31, wherein the apparatus further comprises' means for discovering other NFs of the core network; and means for providing the RAN-UE identifier to the other NFs to enable the other NFs to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0238] Clause 33. A method implemented by a network function (NF) of a core network, the method comprising: receiving a radio access network (RAN) - user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; assigning a NF-UE identifier to the UE; storing the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF; and invoking one or more sendees of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier.

[0239] Clause 34. The method of clause 33, wherein invoking the one or more services comprises: determining the access node in the access node set based on the access node set identifier and the access node identifier; and sending a non-access stratum (NAS) message for the UE to the access node as determined, the NAS message earned in a transport request message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0240] Clause 35. The method of clause 33 or clause 34, wherein the method further comprises: receiving a non-access stratum (NA.S) message from the UE, the NAS message carried in an information transfer message from the access node that also comprises the RAN-UE identifier and the NF-UE identifier; determining the access node and RAN UE context based on the RAN-UE identifier; and identifying the NF UE context based on the NF-UE. identifier.

[0241] Clause 36. The method of any of clauses 33 to 35, wherein the method further comprises: discovering other NFs of the core network; and providing the RA.N-UE identifier to the other NFs to enable the other NFs to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0242] Clause 37. A computer-readable storage medium implemented at a network function (NF) of a core network, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a radio access network (RAN) - user equipment (UE) identifier assigned to a UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; assign a NF-UE identifier to the UE; store the RAN-UE identifier and the NF-UE identifier in a NF UE context associated with the UE at the NF; and in voke one or more services of the RAN for the UE based on the RAN-UE identifier and the NF-UE identifier.

[0243] Clause 38. The computer-readable storage medium of clause 37, wherein the apparatus caused to invoke the one or more services comprises the apparatus caused to: determine the access node in the access node set based on the access node set identifier and the access node identifier; and send a non-access stratum (NAS) message for the UE to the access node as determined, the NAS message earned in a transport request message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0244] Clause 39. The computer-readable storage medium of clause 37 or clause 38, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: receive a non-access stratum (NAS) message from the UE. the NAS message carried in an information transfer message from the access node that also comprises the RAN-UE identifier and the NF-UE identifier; determine the access node and RAN UE context based on the RAN-UE identifier; and identify the NF UE, context based on the NF-UE identifier.

[0245] Clause 40. The computer-readable storage medium of any of clauses 37 to 39, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: discover other NFs of the core network; and provide the RAN-UE identifier to the other NFs to enable the other NFs to invoke services of the RAN for the UE based on the RAN-UE identifier.

[0246] Clause 41. An apparatus comprising means for performing the method of any of clauses 33 to 36.

[0247] Clause 42. A computer-readable medium comprising instructions that, m response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 33 to 36, [024S] Clause 43. ,A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 33 to 36.

[0249] Clause 44. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 33 to 36.

[0250] Clause 45. An apparatus to implement a user equipment (UE), the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: initiate a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE within the RAN is established; receive an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the RAN-UE. identifier in at least one UE context that is maintained independent of an RRC state of the UE.

[0251] Clause 46. The apparatus of clause 45, wherein the at least one processing circuity is configured to execute the instructions to cause the apparatus to further perform a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, and wherein the RRC message that comprises the RAN-UE identifier is a secured RRC message.

[0252] Clause 47. The apparatus of clause 45 or clause 46, wherein the apparatus caused to store the RAN-UE identifier comprises the apparatus caused to: store the RAN-UE identifier in an RRC UE context at an RRC layer; and pass the RAN-UE identifier from the RRC layer to a non-access stratum (NAS) layer at which the RAN-UE identifier is stored in a NAS UE context.

[0253] Clause 48. The apparatus of any of clauses 45 to 47, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: send a non-access stratum (NAS) message for the NF to the access node, the NAS message carried in an information transfer message that comprises NAS type information that indicates a type of the NF, and based on which the NF-UE identifier stored in the RAN UE context is identifiable.

[0254] Clause 49. The apparatus of any of clauses 45 to 48, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further send the RAN-UE identifier to the RAN to enable access to the RAN UE context based on the RAN-UE identifier independent of the RRC state of the UE.

[0255] Clause 50. The apparatus of clause 49, wherein the RAN-UE identifier is sent to the RAN by the UE in an RRC idle state, and wherein the RAN-UE identifier is sent during setup or reestablishment of an RRC connection with the RAN.

[0256] Clause 51. An apparatus to implement a user equipment (UE), the apparatus comprising: means for initiating a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE within the RAN is established; means for receiving an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and means for storing the RAN-UE identifier in at least one UE context that is maintained independent of an RRC state of the UE.

[0257] Clause 52. The apparatus of clause 51, wherein the apparatus further comprises means for performing a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, and wherein the RRC message that comprises the RAN-UE identifier is a secured RRC message

[0258] Clause 53. The apparatus of clause 51 or clause 52, wherein the means for storing the RAN-UE identifier comprises: means for storing the RAN-UE identifier in an RRC UE context at an RRC layer, and means for passing the RAN-UE identifier from the RRC layer to a non-access stratum (NAS) layer at which the RAN-UE identifier is stored in a NAS UE context.

[0259] Clause 54. The apparatus of any of clauses 51 to 53, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the apparatus further comprises: means for sending a non-access stratum (NAS) message for the NF to the access node, the NAS message carried in an information transfer message that comprises NAS type information that indicates a type of the NF, and based on which the NF-UE identifier stored in the RAN UE context is identifiable.

[0260] Clause 55. The apparatus of any of clauses 51 to 54, wherein the apparatus further comprises means for sending the RAN-UE identifier to the RAN to enable access to the RAN UE context based on the RAN-UE identifier independent of the RRC state of the UE,

[0261] Clause 56. The apparatus of clause 55, wherein the RAN-UE identifier is sent to the RAN by the UE. in an RRC idle state, and wherein the RAN-UE identifier is sent during setup or reestablishment of an RRC connection with the RAN.

[0262] Clause 57. .A method implemented by a user equipment (UE), the method comprising: initiating a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE withm the RAN is established; receiving an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the R.AN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and storing the RAN-UE identifier in at least one UE context that is maintained independent of an RRC] state of the UE.

[0263] Clause 58. The method of clause 57, wherein the method further comprises performing a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, and wherein the RRC message that comprises the RAN-UE identifier is a secured RRC message.

[0264] Clause 59. The method of clause 5 7 or clause 58, wherein storing the RAN-UE identifier comprises: storing the RAN-UE identifier in an RRC UE context at an RRC layer; and passing the RAN-UE identifier from the RRC layer to a non-access stratum (NAS) layer at which the RAN-UE identifier is stored in a NAS UE context.

[0265] Clause 60. The method of any of clauses 57 to 59, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the method further comprises: sending a non-access stratum (NAS) message for the NF to the access node, the NAS message carried in an information transfer message that comprises NAS type information that indicates a type of the NF, and based on which the NF-UE identifier stored in the RAN UE context is identifiable.

[0266] Clause 61. The method of any of clauses 57 to 60, wherein the method further comprises sending the RAN-UE identifier to the RAN to enable access to the RAN UE context based on the RAN-UE identifier independent of the RRC state of the LIE.

[0267] Clause 62. The method of clause 61, wherein the RAN-UE identifier is sent to the RAN by the UE in an RRC idle state, and wherein the RAN-UE identifier is sent during setup or reestablishment of an RRC connection with the RAN.

[0268] Clause 63. A computer-readable storage medium implemented at a user equipment (UE), the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: initiate a registration procedure with a core network, during setup of a radio resource control (RRC) connection with an access node of an access node set within a radio access network (RAN), and in which a RAN UE context associated with the UE within the RAN is established; receive an RRC message from the access node that comprises a RAN-UE identifier assigned to the UE by the access node, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the RAN-UE identifier also provided to network functions of the core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the RAN-UE identifier in at least one UE context that is maintained independent of an RRC state of the UE.

[0269] Clause 64. The computer-readable storage medium of clause 63, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further perform a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, and wherein the RRC message that comprises the RAN-UE identifier is a secured RRC message.

[0270] Clause 65. The computer-readable storage medium of clause 63 or clause 64, wherein the apparatus caused to store the RAN-UE identifier comprises the apparatus caused to: store the RAN-UE identifier in an RRC UE context at an RRC layer; and pass the RAN-UE identifier from the RRC layer to a non-access stratum (NAS) layer at which the RAN-UE identifier is stored in a NAS UE context.

[0271] Clause 66. The computer-readable storage medium of any of clauses 63 to 65, wherein the network functions comprise a network function (NF), wherein a NF-UE identifier assigned to the UE by the NF is stored in the RAN UE context, and wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: send a non-access stratum (NAS) message for the NF to the access node, the NAS message earned in an information transfer message that comprises NAS type information that indicates a type of the NF, and based on which the NF-UE identifier stored in the RAN UE context is identifiable.

[0272] Clause 67. The computer-readable storage medium of any of clauses 63 to 66, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further send the RAN-UE identifier to the RAN to enable access to the RAN UE con text based on the RAN-UE identifier independent of the RRC state of the UE.

[0273] Clause 68. The computer-readable storage medium of clause 67, wherein the RAN-UE identifier is sent to the RAN by the UE in an RRC idle state, and wherein the RAN-UE identifier is sent during setup or reestablishment of an RRC connection with the RAN.

[0274] Clause 69. An apparatus comprising means for performing the method of any of clauses 57 to 62.

[0275] Clause 70. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 57 to 62.

[0276] Clause 71. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 57 to 62.

[0277] Clause 72. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 57 to 62.

[0278] Clause 73. An apparatus to implement an access node, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a non-access stratum (NAS) service request message from a user equipment (UE) served by the access node of an access node set within a radio access network (RAN ), the NAS service request message for a network function of a core network, the NAS service request message carried in an unsecured message that also comprises a RAN-UE identifier assigned to the UE; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier, assign a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the new RAN-UE identifier in the RAN UE context; and send the NAS service request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0279] Clause 74. The apparatus of clause 73, wherein the core network includes a mobility management network function (NF), wherein a NF-UE identifier assigned to the UE by the mobility management NF is stored in the RAN UE context, and wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: identify the NF-UE identifier stored in the RAN UE context; determine the mobility management NF based on the NF-UE identifier; and send a notification message to the mobility management NF that comprises the new RAN-UE identifier and the NF-UE identifier.

[0280] Clause 75. The apparatus of clause 73 or clause 74, wherein the NF is a session management NF, and the NAS service request message is for activation of a user plane for an established one or more packet data, unit sessions of the UE m the session management NF, and wherein the NAS service request message comprises a NF-UE identifier assigned to the UE by the session management NF, and the NAS message is carried in the notification message that also comprises the NF-UE identifier.

[0281] Clause 76. The apparatus of clause 75, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: receive a NAS service request accept message for the UE, the NAS service request accept message earned in a resource request message from the session management NF; and allocate user plane resources for the one or more packet data unit sessions based on the resource request message.

[0282] Clause 77 The apparatus of clause 76, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further send the NAS service request accept message to the UE, the NAS service request accept message carried in a message that also comprises the new RAN-UE identifier.

[0283] Clause 78. An apparatus to implement an access node, the apparatus comprising: means for receiving a non-access stratum (NAS) service request message from an user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message for a network function of a core network, the NAS service request message carried in an unsecured message that also comprises a RAN-UE identifier assigned to the UE; means for accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier, means for assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; means for storing the new RAN-UE identifier in the RAN UE context; and means for sending the N AS sendee request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0284] Clause 79. The apparatus of clause 78, wherein the core network includes a mobility management network function (NF), wherein a NF-UE identifier assigned to the UE by the mobility management NF is stored in the RAN UE context, and wherein the apparatus further comprises: means for identifying the NF-UE identifier stored in the RAN UE context; means for determining the mobility’ management NF based on the NF-UE identifier; and means for sending a notification message to the mobility management NF that comprises the new RAN-UE identifier and the NF-UE identifier.

[0285] Clause 80. The apparatus of clause 78 or clause 79, wherein the NF is a session management NF, and the NAS service request message is for activation of an user plane for an established one or more packet data unit sessions of the UE in the session management NF, and wherein the NAS service request message comprises a NF-UE identifier assigned to the UE by the session management NF, and the NAS message is carried in the notification message that also comprises the NF-UE identifier.

[0286] Clause 81. The apparatus of clause 80, wherein the apparatus further comprises: means for receiving a NAS service request accept message for the UE, the NAS service request accept message carried in a resource request message from the session management NF; and means for allocating user plane resources for the one or more packet data unit sessions based on the resource request message.

[0287] Clause 82. The apparatus of clause 81, wherein the apparatus further comprises means for sending the NAS service request accept message to the UE, the NAS service request accept message earned in a message that also comprises the new RAN-UE identifier.

[0288] Clause 83. A method implemented by an access node, the method comprising: receiving a non-access stratum (NAS) service request message from a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message for a network function of a core network, the NAS service request message earned in an unsecured message that also comprises a RAN-UE identifier assigned to the UE; accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; storing the new RAN-UE identifier in the RAN UE context; and sending the NAS service request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0289] Clause 84. The method of clause 83, wherein the core network includes a mobility management network function (NF), wherein a NF-UE identifier assigned to the UE by the mobility management NF is stored in the RAN UE context, and wherein the method further comprises: identifying the NF-UE identifier stored in the RAN UE context; determining the mobility management NF based on the NF-UE identifier; and sending a notification message to the mobility management NF that comprises the new RAN-UE identifier and the NF-UE identifier.

[0290] Clause 85. The method of clause 83 or clause 84, wherein the NF is a session management NF, and the NAS service request message is for activation of a user plane for an established one or more packet data unit sessions of the UE in the session management NF, and wherein the N AS service request message comprises a NF-UE identifier assigned to the UE by the session management NF, and the NAS message is carried in the notification message that also comprises the NF-UE identifier.

[0291] Clause 86. The method of clause 85, wherein the method further comprises: receiving a NAS service request accept message for the UE, the NAS sendee request accept message carried in a resource request message from the session management NF; and allocating user plane resources for the one or more packet data unit sessions based on the resource request message.

[0292] Clause 87. The method of clause 86, wherein the method further comprises sending the NAS sendee request accept message to the UE, the NAS sendee request accept message earned in a message that also comprises the new RAN-UE identifier.

[0293] Clause 88. A computer-readable storage medium implemented an access node, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a non-access stratum (NAS) service request message from a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message for a network function of a core network, the NAS service request message carried in an unsecured message that also comprises a RAN-UE identifier assigned to the UE; access a RAN UE context associated with the UE within the RAN’ based on the RAN-UE identifier; assign a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; store the new RAN-UE identifier in the RAN UE context; and send the NAS service request message to the network function, the NAS service request message carried in a notification message that also comprises the new RAN-UE identifier.

[0294] Clause 89. The computer-readable storage medium of clause 88, wherein the core network includes a mobility management network function (NF), wherein a NF-UE identifier assigned io the UE by the mobility management NF is stored in the RAN UE context, and wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: identify the NF-UE identifier stored in the RAN UE context; determine the mobility management NF based on the NF-UE identifier; and send a notification message to the mobility management NF that comprises the new RAN-UE identifier and the NF-UE identifier.

[0295] Clause 90. The computer-readable storage medium of clause 88 or clause 89, wherein the NF is a session management NF, and the NAS service request message is for activation of a user plane for an established one or more packet data unit sessions of the UE in the session management NF, and wherein the NAS service request message comprises a NF-UE identifier assigned to the UE by the session management NF, and the NAS message is carried in the notification message that also comprises the NF-UE identifier.

[0296] Clause 91. The computer-readable storage medium of clause 90, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: receive a NAS service request accept message for the UE, the NAS service request accept message carried in a resource request message from the session management NF, and allocate user plane resources for the one or more packet data unit sessions based on the resource request message.

[0297] Clause 92. The computer-readable storage medium of clause 91, wherein the computer-readable storage medium has further instructions stored therein that, m response to execution by the at least one processing circuitry, causes the apparatus to further send tire NAS service request accept message to the UE, the NAS sendee request accept message carried in a message that also comprises the new RAN-UE identifier.

[9298] Clause 93. An apparatus comprising means for performing the method of any of clauses 83 to 87.

[0299] Clause 94. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 83 to 87.

[0300] Clause 95. A computer-readable storage medium comprising instructions that in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 83 to 87.

[0301] Clause 96. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 83 to 87.

[0302] Clause 97. An apparatus to implement an user equipment (UE), the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: initiate a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; receive an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RA.N-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the new' RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE.

[0303] Clause 98. The apparatus of clause 97, wherein the NAS service request procedure is for activation of a user plane of an established one or more packet data unit sessions of the UE in a session management network function (NF) of the core network, and the NAS service request message comprises a NF-UE identifier assigned to the UE by the session management NF.

[0304] Clause 99. The apparatus of clause 97 or clause 98, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further perform a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, and wherein the RRC message that comprises the new RAN-UE identifier is a secured RRC message.

[0305] Clause 100. The apparatus of any of clauses 97 to 99, wherein the apparatus caused to store the RAN-UE identifier comprises the apparatus caused to: store the new RAN-UE identifier in an RRC UE context at an RRC layer; and pass the new RAN-UE identifier from the RRC layer to a non-access stratum (NAS) layer at which the new RAN-UE identifier is stored in a NAS UE context.

[0306] Clause 101. An apparatus to implement an user equipment (UE), the apparatus comprising: means for initiating a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; means for receiving an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the new RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and means for storing the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE,

[0307] Clause 102. The apparatus of clause 101 or clause 101, wherein the NAS service request procedure is for activation of an user plane of an established one or more packet data unit sessions of the UE in a session management network function (NF) of the core network, and the NAS service request message comprises a NF-UE identifier assigned to the UE by the session management NF.

[0308] Clause 103. The apparatus of clause 101 or clause 102, wherein the apparatus further comprises means for performing a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, and wherein the RRC message that comprises the new RAN-UE identifier is a secured RRC message.

[0309] Clause 104. The apparatus of clause 101 or clause 103, wherein the means for storing the RAN-UE identifier comprises: means for storing the new RAN-UE identifier in an RRC UE. context at an RRC layer; and means for passing the new RAN-UE identifier from the RRC layer to a. non-access stratum (NAS) layer at which the new RAN-UE identifier is stored in a NAS UE context.

[0310] Clause 105. A method implemented by a user equipment (UE), the method comprising: initiating a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; receiving an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an iden tifier of the RAN UE contex t, the new RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and storing the new RAN-UE identifier to enable access to the RAN UE context based on the new RAN-UE identifier independent of an RRC state of the UE.

[0311] Clause 106. The method of clause 105 or clause 105, wherein the NAS service request procedure is for activation of a user plane of an established one or more packet data unit sessions of the UE in a session management network function (NF) of the core network, and the NAS service request message comprises a NF-UE identifier assigned to the UE by the session management NF.

[0312] Clause 107. The method of clause 105 or clause 106, wherein the method further comprises performing a security activation procedure with the access node to activate security for RRC messages between the UE. and the access node, and wherein the RRC message that comprises the new RAN-UE identifier is a secured RRC message.

[0313] Clause 108. The method of clause 105 or clause 107, wherein storing the RAN-UE identifier comprises: storing the new RAN-UE identifier in an RRC UE context at an RRC layer; and passing the new RAN-UE identifier from the RRC layer to a non-access stratum (NAS) layer at which the new RAN-UE identifier is stored in a NAS UE context.

[0314] Clause 109. A computer-readable storage medium implemented an user equipment (UE), the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: initiate a non-access stratum (NAS) service request procedure towards a network function of a core network by sending a NAS service request message to an access node of an access node set within a radio access network (RAN), during setup of a radio resource control (RRC) connection with the access node, the NAS service request message carried in an unsecured RRC message that also comprises a RAN-UE identifier assigned to the UE; receive an RRC message from the access node that comprises a new RAN-UE identifier assigned to the UE by the access node, the new RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context, the new RAN-UE identifier also provided to network functions of a core network to enable the network functions invoke services of the RAN for the UE based on the RAN-UE identifier; and store the new RAN-UE identifier to enable access to the RAN UE context based on the new' RAN-UE identifier independent of an RRC state of the UE.

[0315] Clause 110. The computer-readable storage medium of clause 109 or clause 109, wherein the NAS service request procedure is for activation of a user plane of an established one or more packet data unit sessions of the UE tn a session management network function (NF) of the core network, and the NAS service request message comprises a NF-UE identifier assigned to the UE by the session management NF.

[0316] Clause 111. The computer-readable storage medium of clause 109 or clause 110, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further perform a security activation procedure with the access node to activate security for RRC messages between the UE and the access node, and wherein the RRC message that comprises the new RAN-UE identifier is a secured RRC message.

[0317] Clause 112. The computer-readable storage medium of clause 109 or clause 111, wherein the apparatus caused to store the RAN-UE identifier comprises the apparatus caused to: store the new RAN-UE identifier in an RRC UE context at an RRC layer; and pass the new RAN-UE. identifier from the RRC layer to a non-access stratum (NAS) layer at which the new RAN-UE identifier is stored in a NAS UE context.

[0318] Clause 113. An apparatus comprising means for performing the method of any of clauses 105 to 108.

[0319] Clause 114. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 105 to 108.

[0320] Clause 115. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 105 to 108.

[0321] Clause 116. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 105 to 108.

[0322] Clause 117. An apparatus to implement a network function (NF) of a core network, the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: access a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; determine the access node in the access node set based on the access node set identifier and the access node identifier; and initiate a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0323] Clause 118. The apparatus of clause 117 or clause 117, wherein the at least one processing circuitry' is configured to execute the instructions to cause the apparatus to further at least: send a reachability request message relating to the UE to a mobility management network function of the core network; and receive a reachability response message from the mobility management network function, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

[0324] Clause 119. The apparatus of clause 117 or clause 118, wherein the network function has a subscription to reachability notifications relating to the UE, and the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: receive a reachability notification message from a mobility management network function based on the subscription, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

[0325] Clause 120. The apparatus of clause 117 or clause 119, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further receive a NAS service request response message from the access node, the NAS service request response message carried in a transport message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0326] Clause 121. An apparatus to implement a network function (NF) of a core network, the apparatus comprising: means for accessing a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; means for determining the access node in the access node set based on the access node set identifier and the access node identifier; and means for initiating a non-access stratum (NAS) service request procedure towards the UE by sending a NAS sendee request message for the UE, to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0327] Clause 122. The apparatus of clause 121 or clause 121, wherein the apparatus further comprises: means for sending a reachability request message relating to the UE to a mobility management network function of the core network; and means for receiving a reachability response message from the mobility management network function, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

[0328] Clause 123. The apparatus of clause 121 or clause 122, wherein the network function has a subscription to reachability notifications relating to the UE, and the apparatus further comprises: means for receiving a reachability notification message from a mobility management network function based on the subscription, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

[0329] Clause 124. The apparatus of clause 121 or clause 123, wherein the apparatus further comprises means for receiving a NAS service request response message from the access node, the NAS service request response message carried in a transport message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0330] Clause 125. A method implemented by a network function (NF) of a core network, the method comprising: accessing a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; determining the access node in the access node set based on the access node set identifier and the access node identifier; and initiating a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0331] Clause 126. The method of clause 125 or clause 125, wherein the method further comprises: sending a reachability request message relating to the UE to a mobility management network function of the core network; and receiving a reachability response message from the mobility management network function, the reachability response message comprising the RAN-UE identifier and indicating the UE is m a connected state.

[0332] Clause 127. The method of clause 125 or clause 126, wherein the network function has a subscription to reachability notifications relating to the UE, and the method further comprises: receiving a reachability notification message from a mobility management network function based on the subscription, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

[0333] Clause 128. The method of clause 125 or clause 127, wherein the method further comprises receiving a NAS service request response message from the access node, the NAS service request response message carried in a transport message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0334] Clause 129. A computer-readable storage medium implemented at a network function (NF) of a core network, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least-one processing circuitry, causes an apparatus to at least: access a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set 'within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN; determine the access node in the access node set based on the access node set identifier and the access node identifier, and initiate a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

[0335] Clause 130. The computer-readable storage medium of clause 129 or clause 129, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: send a reachability request message relating to the UE to a mobility management network function of the core network, and receive a reachability response message from the mobility management network function, the reachability response message comprising the RAN-UE identifier and indicating the UE. is in a connected state.

[0336] Clause 131. The computer-readable storage medium of clause 129 or clause 130, wherein the network function has a subscription to reachability notifications relating to the UE., and the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: receive a reachability notification message from a mobility management network function based on the subscription, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

[0337] Clause 132. The computer-readable storage medium of clause 129 or clause 131, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further receive a NAS service request response message from the access node, the NAS service request response message carried in a transport message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0338] Clause 133. An apparatus comprising means for performing the method of any of clauses 125 to 128.

[0339] Clause 134. A computer-readable medium comprising instructions that, m response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 125 to 128.

[0340] Clause 135. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 125 to 128.

[0341] Clause 136. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 125 to 128.

[0342] Clause 137. An apparatus to implement an access node, the apparatus comprising: at least one memory' configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a non-access stratum (NAS) service request message relating to a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; store the NF-UE identifier in the RAN UE context; and process the NAS service request message.

[0343] Clause 138. The apparatus of clause 137 or clause 137, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: forward a paging message comprising the NF-UE identifier to the UE in a radio resource control (RRC) idle state to trigger establishment of an RRC connection; perform a radio resource control (RRC) connection setup procedure with the UE during which the RAN-UE identifier is received from the UE; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0344] Clause 139. The apparatus of clause 138 or clause 138, wherein the RAN-UE identifier is received from the UE in an unsecured RRC message, and the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: assign a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; and store the new RAN-UE identifier in the RAN UE context.

[0345] Clause 140. The apparatus of clause 137 or clause 139, wherein the apparatus caused to process the NAS service request message comprises the apparatus caused to send the NAS service request message to the UE, the NAS service request message carried in an information transfer message that also comprises the RAN-UE identifier.

[0346] Clause 141. The apparatus of clause 140 or clause 140, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further perform a security activation procedure with the UE to activate security for radio resource control (RRC) messages between the UE and the access node, and wherein the information transfer message in which the NAS service request message is carried, and that also comprises the RAN-UE identifier, is a secured RRC message.

[0347] Clause 142. The apparatus of clause 140 or clause 141, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: receive a NAS service request accept message for the NF from the UE, the NAS service request accept message carried in an information transfer message that comprises NAS type information that indicates a type of the NF; identify the NF-UE identifier stored in the RAN LIE context based on the NAS type information; and send the NAS service request accept message to the NF, the NAS service request accept message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier. [034S] Clause 143. The apparatus of clause 137 or clause 142, wherein the apparatus caused to process the NAS service request message comprises the apparatus caused to: make a determination that the access node is unable to send the NAS service request message to the UE; and based on the determination, send a non-delivery notification message to the NF, the non-delivery notification message comprising the RAN-UE identifier and the NF-UE identifier.

[0349] Clause 144. An apparatus to implement an access node, the apparatus comprising: means for receiving a non-access stratum (NAS) service request message relating to an user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; means for accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; means for storing the NF-UE identifier m the RAN UE context; and means for processing the NAS service request message.

[0350] Clause 145. The apparatus of clause 144 or clause 144, wherein the apparatus further comprises: means for forwarding a paging message comprising the NF-UE identifier to the UE in a radio resource control (RRC) idle state to trigger establishment of an RRC connection; means for performing a radio resource control (RRC) connection setup procedure with the UE during which the RAN-UE identifier is received from, the UE; means for accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0351] Clause 146. The apparatus of clause 145 or clause 145, wherein the RAN-UE identifier is received from the UE in an unsecured RRC message, and the apparatus further comprises: means for assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN LIE context; and means for storing the new RAN-UE identifier in the RAN UE context.

[0352] Clause 147. The apparatus of clause 144 or clause 146, wherein the means for processing the NAS service request message comprises means for sending the NAS service request message to the UE, the NAS service request message carried in an information transfer message that also comprises the RAN-UE identifier.

[0353] Clause 148. The apparatus of clause 147 or clause 147, wherein the apparatus further comprises means for performing a security activation procedure with the UE to activate security for radio resource control (RRC) messages between the UE and the access node, and wherein the information transfer message in which the NAS service request message is carried, and that also comprises the RAN-UE identifier, is a secured RRC message.

[0354] Clause 149. The apparatus of clause 147 or clause 148, wherein the apparatus further comprises: means for receiving a NAS service request accept message for the NF from the UE, the NAS service request accept message carried in an information transfer message that comprises NAS type information that indicates a type of the NF; means for identifying the NF-UE identifier stored in the RAN UE context based on the NAS type information, and means for sending the N AS service request accept message to the NF, the NAS service request accept message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0355] Clause 150. The apparatus of clause 144 or clause 149, wherein the means for processing the NAS sendee request message comprises: means for making a determination that the access node is unable to send the NAS service request message to the UE; and based on the determination, means for sending a non-delivery notification message to the NF, the non-delivery notification message comprising the RAN-UE identifier and the NF-UE identifier.

[0356] Clause 151. A method implemented by an access node, the method comprising: receiving a non-access stratum (NAS) service request message relating to a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; storing the NF-UE identifier in the RAN UE context, and processing the NAS service request message.

[0357] Clause 152. The method of clause 151 or clause 151, wherein the method further comprises: forwarding a paging message comprising the NF-UE identifier to the UE in a radio resource control (RRC) idle state to trigger establishment of an RRC connection: performing a radio resource control (RRC?) connection setup procedure with the UE during which the RAN-UE identifier is received from the UE; accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier. [035S] Clause 153. The method of clause 152 or clause 152, wherein the RAN-UE identifier is received from the UE in an unsecured RRC message, and the method further comprises: assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; and storing the new RAN-UE identifier in the RAN UE context.

[0359] Clause 154. The method of clause 151 or clause 153, wherein processing the NAS service request message comprises sending the NAS service request message to the UE, the NAS sendee request message carried in an information transfer message that also comprises the RAN-UE identifier.

[0360] Clause 155. The method of clause 154 or clause 154, wherein the method further comprises performing a security activation procedure with the UE to activate security for radio resource control (RRC) messages between the UE and the access node, and wherein the information transfer message in which the NAS sendee request message is carried, and that also comprises the RAN-UE identifier, is a secured RRC message.

[0361] Clause 156. The method of clause 154 or clause 155, wherein the method further comprises: receiving a NAS service request accept message for the NF from the UE, the NAS service request accept message earned in an information transfer message that comprises N AS type information that indicates a type of the NF; identifying the NF-UE identifier stored in the RAN UE context based on the NAS type information, and sending the NAS service request accept message to the NF, the NAS service request accept message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0362] Clause 157. The method of clause 151 or clause 156, wherein processing the NAS service request message comprises: making a determination that the access node is unable to send the NAS service request, message to the UE; and based on the determination, sending a non-delivery notification message to the NF, the non-delivery notification message comprising the RAN-UE identifier and the NF-UE identifier.

[0363] Clause 158. A computer-readable storage medium implemented at an access node, the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a non-access stratum (NAS) service request message relating to a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier; store the NF-UE identifier in the RAN UE context; and process the NAS service request message.

[0364] Clause 159. The computer-readable storage medium of clause 158 or clause 158, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: forward a paging message comprising the NF-UE identifier to the UE in a radio resource control (RRC) idle state to trigger establishment of an RRC connection; perform a radio resource control (RRC) connection setup procedure with the UE during which the RAN-UE identifier is received from the UE; access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0365] Clause 160. The computer-readable storage medium of clause 159 or clause 159, wherein the RAN-LIE identifier is received from the UE in an unsecured RRC message, and the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: assign a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; and store the new RAN-UE identifier in the RAN UE context.

[0366] Clause 161. The computer-readable storage medium of clause 158 or clause 160, wherein the apparatus caused to process the NAS service request message comprises the apparatus caused to send the NAS service request message to the UE, the NAS service request message carried in an information transfer message that also comprises the RAN-UE identifier.

[0367] Clause 162. The computer-readable storage medium of clause 161 or clause 161, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further perform a security activation procedure with the UE to activate security for radio resource control (RRC) messages between the UE and the access node, and wherein the information transfer message in which the NAS service request message is carried, and that also comprises the RAN-UE identifier, is a secured RRC message.

[0368] Clause 163. The computer-readable storage medium of clause 161 or clause 162, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further at least: receive a NAS service request accept message for the NF from the UE, the NAS service request accept message carried in an information transfer message that comprises NAS type information that indicates a type of the NF; identify the NF-UE identifier stored in the RAN UE context based on the NAS type information; and send the NAS service request accept message to the NF, the NAS service request accept message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

[0369] Clause 164. The computer-readable storage medium of clause 158 or clause 163, wherein the apparatus caused to process the NAS service request message comprises the apparatus caused to: make a determination that the access node is unable to send the NAS service request message to the UE; and based on the determination, send a nondelivery notification message to the NF, the non-delivery notification message comprising the RAN-UE identifier and the NF-UE identifier.

[0370] Clause 165. An apparatus comprising means for performing the method of any of clauses 151 to 157.

[0371] Clause 166. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 151 to 157.

[0372] Clause 167. A computer-readable storage medium comprising instructions that, m response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 151 to 157.

[0373] Clause 168. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 151 to 157.

[0374] Clause 169. An apparatus to implement a user equipment (UE), the apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN), identify a RAN-UE identifier in the RRC paging message; pass the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; receive a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and perform an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier

[0375] Clause 170. The apparatus of clause 169 or clause 169, wherein the request from the NAS layer includes the RAN-UE identifier, and the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further access an RRC UE context at the RRC layer based on the RAN-UE identifier, and wherein the RRC connection procedure is performed based on the RRC UE context.

[0376] Clause 171. The apparatus of clause 170 or clause 170, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further determine the RRC UE context excludes a security context, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

[0377] Clause 172. The apparatus of clause 170 or clause 171, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further determine the RRC UE context includes a security context, and wherein the RRC connection procedure that is performed is an RRC. connection reestablishment procedure to which the security context is applied.

[0378] Clause 173. The apparatus of clause 170 or clause 172, wherein the RRC connection procedure is performed further based on a time durati on of the UE in the RRC idle state.

[0379] Clause 174. The apparatus of clause 173 or clause 173, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further determine the time duration of the UE in the RRC idle state exceeds a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

[0380] Clause 175. The apparatus of clause 173 or clause 174, wherein, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further determine the RRC UE context includes a security context, and the time duration of the UE in the RRC idle state does not exceed a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

[0381] Clause 176. An apparatus to implement a user equipment (UE), the apparatus comprising: means for receiving a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN); means for identifying a RAN-UE identifier in the RRC paging message; means for passing the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; means for receiving a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and means for performing an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0382] Clause 177. The apparatus of clause 176 or clause 176, wherein the request from the NAS layer includes the RAN-UE identifier, and the apparatus further comprises means for accessing an RRC UE context at the RRC layer based on the RAN-UE identifier, and wherein the RRC connection procedure is performed based on the RRC UE context.

[0383] Clause 178. The apparatus of clause 177 or clause 177, wherein the apparatus further comprises means for determining the RRC UE context excludes a security-context, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

[0384] Clause 179. The apparatus of clause 177 or clause 178, wherein the apparatus further comprises means for determining the RRC UE context includes a security- context, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

[0385] Clause 180. The apparatus of clause 177 or clause 179, wherein the RRC connection procedure is performed further based on a time duration of the UE in the RRC idle state.

[0386] Clause 181. The apparatus of clause 180 or clause 180, wherein the apparatus further comprises means for determining the time duration of the UE in the RRC idle state exceeds a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

[0387] Clause 182. The apparatus of clause 180 or clause 181, wherein, wherein the apparatus further comprises means for determining the RRC UE context includes a security context, and the time duration of the UE, in the RRC idle state does not exceed a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

[0388] Clause 183. A method implemented by a user equipment (UE.), the method comprising: receiving a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN); identifying a RAN-UE identifier in the RRC paging message, passing the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; receiving a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and performing an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0389] Clause 184. The method of clause 183 or clause 183, wherein the request from the NAS bver includes the RAN-UE identifier, and the method further comprises accessing an RRC UE context at the RRC layer based on the RAN-UE identifier, and wherein the RRC connection procedure is performed based on the RRC UE context.

[0390] Clause 185. The method of clause 184 or clause 184, wherein the method further comprises determining the RRC UE context excludes a security context, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

[0391] Clause 186. The method of clause 184 or clause 185, wherein the method further comprises determining the RRC UE context includes a security context, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security’ context is applied.

[0392] Clause 187. The method of clause 184 or clause 186, wherein the RRC connection procedure is performed further based on a time duration of the UE in the RRC idle state.

[0393] Clause 188. The method of clause 187 or clause 187, wherein the method further comprises determining the time duration of the UE in the RRC idle state exceeds a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

[0394] Clause 189. The method of clause 187 or clause 188, wherein, wherein the method further comprises determining the RRC UE context includes a security context, and the time duration of the UE in the RRC idle state does not exceed a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

[0395] Clause 190. A computer-readable storage medium to implement a user equipment (UE), the computer-readable storage medium being non-transitory and having instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN); identify a RAN-UE identifier in the RRC paging message; pass the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer; receive a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; and perform an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

[0396] Clause 191. The computer-readable storage medium of clause 190 or clause 190, wherein the request from the NAS layer includes the RAN-UE identifier, and the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry’, causes the apparatus to further access an RRC UE context at the RRC layer based on the RAN-UE identifier, and wherein the RRC connection procedure is performed based on the RRC UE context.

[0397] Clause 192. The computer-readable storage medium of clause 191 or clause 191, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further determine the RRC UE context excludes a security context, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure. [039S] Clause 193. The computer-readable storage medium of clause 191 or clause 192, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further determine the RRC UE context includes a security context, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

[0399] Clause 194. The computer-readable storage medium of clause 191 or clause 193, wherein the RRC connection procedure is performed further based on a time duration of the UE m the RRC idle state.

[0400] Clause 195. The computer-readable storage medium of clause 194 or clause 194, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further determine the time duration of the UE in the RRC idle state exceeds a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure

[0401] Clause 196. The computer-readable storage medium of clause 194 or clause 195, wherein, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further determine the RRC UE context includes a security context, and the time duration of the UE in the RRC idle state does not exceed a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

[9402] Clause 197. An apparatus comprising means for performing the method of any of clauses 183 to 189.

[0403] Clause 198. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 1 83 to 189.

[0404] Clause 199. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry', causes an apparatus to perform the method of any of clauses 183 to 189.

[0405] Clause 200. A computer program comprising instructions that, in response to execution by at least one processing circuitry', causes an apparatus to perform the method of any of clauses 183 to 189.

[0406] Many modifications and other implementations of the disclosure set forth herein will come to mind to one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated figures describe example implementations in the context of certain example combinations of elements and / or functions, it should be appreciated that different combinations of elements and / or functions may be provided by alternative implementations without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method implemented by a network function (NF) of a core network, the method comprising:accessing a NF user equipment (UE) context associated with a UE at the NF, the NF UE context comprising a radio access network (RAN) - UE identifier assigned to the UE served by an access node of an access node set within a RAN, the RAN-UE identifier comprising an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of a RAN UE context associated with the UE within the RAN;determining the access node m the access node set based on the access node set identifier and the access node identifier; andinitiating a non-access stratum (NAS) service request procedure towards the UE by sending a NAS service request message for the UE to the access node, carried in a transport message that also comprises the RAN-UE identifier and a NF-UE identifier assigned to the UE by the NF.

2. The method of claim 1, wherein the method further comprises:sending a reachability request message relating to the UE to a mobility management network function of the core network; andreceiving a reachability response message from the mobility management network function, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

3. The method of claim 1 or claim 2, wherein the network function has a subscription to reachability notifications relating to the UE, and the method further comprises:receiving a reachability notification message from a mobility management network function based on the subscription, the reachability response message comprising the RAN-UE identifier and indicating the UE is in a connected state.

4. The method of any of claims 1 to 3, wherein the method further comprises receiving a NAS service request response message from the access node, the NAS service request response message carried m a transport message that also comprises the RAN-UE identifier and the NF-UE identifier.

5. An apparatus comprising means for performing the method of any of claims 1 to 4.

6. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of claims 1 to 4.

7. A method implemented by an access node, the method comprising:receiving a non-access stratum (NAS) service request message relating to a user equipment (UE) served by the access node of an access node set within a radio access network (RAN), the NAS service request message received from a network function (NF) of a core network, the NAS service request message carried in a message that also comprises a RAN-UE identifier and a NF-UE identifier assigned to the UE by respectively the access node and the NF;accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier;storing the NF-UE identifier in the RAN UE context; andprocessing the NAS service request message.

8. The method of claim 7, wherein the method further comprises:forwarding a paging message comprising the NF-UE identifier to the UE in a radio resource control (RRC) idle state to trigger establishment of an RRC connection;performing a radio resource control (RRC) connection setup procedure with the UE during which the RAN-UE identifier is received from the UE;accessing a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

9. The method of claim 8, wherein the RAN-UE identifier is received from the UE in an unsecured RRC message, and the method further comprises:assigning a new RAN-UE identifier to the UE that comprises an access node set identifier that identifies the access node set, an access node identifier that identifies the access node, and an identifier of the RAN UE context; andstoring the new RAN-UE identifier in the RAN UE context.

10. The method of any of claims 7 to 9, wherein processing the NAS service request message comprises sending the NAS service request message to the UE, the NAS service request message carried in an information transfer message that also comprises the RAN-UE identifier.

11. The method of claim 10, wherein the method further comprises performing a security activation procedure with the UE to activate security for radio resource control (RRC) messages between the UE and the access node, andwherein the information transfer message in which the NAS service request message is carried, and that also comprises the RAN-UE identifier, is a secured RRC message.

12. The method of claim 10 or claim 11, wherein the method further comprises: receiving a NAS service request accept message for the NF from the UE, the NAS service request accept message carried in an information transfer message that comprises NAS type information that indicates a type of the NF;identifying the NF-UE identifier stored in the RAN UE context based on the NAS type information; andsending the NAS service request accept message to the NF, the NAS service request accept message carried in a notification message that also comprises the RAN-UE identifier and the NF-UE identifier.

13. The method of any of claims 7 to 12, wherein processing the NAS service request message comprises:making a determination that the access node is unable to send the NAS service request message to the UE; and based on the determination,sending a non-delivery notification message to the NF, the non-delivery notification message comprising the RAN-UE identifier and the NF-UE identifier.

14. An apparatus comprising means for performing the method of any of claims 7 to 13.

15. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of claims 7 to 13.

16. A method implemented by a user equipment (UE), the method comprising: receiving a radio resource control (RRC) paging message at the UE in an RRC idle state, the RRC paging message received from an access node of a radio access network (RAN);identifying a RAN-UE identifier in the RRC paging message;passing the RAN-UE identifier and one or more paging parameters from the RRC paging message from an RRC layer to a non-access stratum (NAS) layer;receiving a request from the NAS layer to establish an RRC connection with the access node based on the RAN-UE identifier and the one or more parameters; andperforming an RRC connection procedure with the access node during which the RAN-UE identifier is sent to the access node to enable the access node to access a RAN UE context associated with the UE within the RAN based on the RAN-UE identifier.

17. The method of claim 16, wherein the request from the NAS layer includes the RAN-UE identifier, and the method further comprises accessing an RRC UE context at the RRC layer based on the RAN-UE identifier, andwherein the RRC connection procedure is performed based on the RRC UE context.

18. The method of claim 17, wherein the method further comprises determining the RRC UE context excludes a security context, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

19. The method of claim 17 or claim 18, wherein the method further comprises determining the RRC UE context includes a security context, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

20. The method of any of claims 17 to 19, wherein the RRC connection procedure is performed further based on a time duration of the UE in the RRC idle state.

21. The method of claim 20, wherein the method further comprises determining the time duration of the UE in the RRC idle state exceeds a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection setup procedure.

22. The method of claim 20 or claim 21, wherein the method further comprises determining the RRC UE context includes a security context, and the time duration of the UE in the RRC idle state does not exceed a threshold duration, and wherein the RRC connection procedure that is performed is an RRC connection reestablishment procedure to which the security context is applied.

23. An apparatus comprising means for performing the method of any of claims 16 to 22.

24. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of claims 16 to 22.

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