Patent Publication Number: US-11382145-B2

Title: Systems and methods to support group communications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Patent Application Ser. No. 62/714,903, entitled “SYSTEMS AND METHODS TO SUPPORT GROUP COMMUNICATIONS” filed Aug. 6, 2018, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally pertains to the field of Communications Networks, and particular embodiments or aspects relate to data transmission from a single data source to multiple electronic devices by using multiple unicast transmission, or multicast transmission, or broadcast transmission, or any combinations thereof. 
     BACKGROUND 
     An Electronic Device (ED), for example a User Equipment (UE), may have data connections to receive unicast, multicast or broadcast data. In current 5G systems, one Access Management Function (AMF) instance is selected to support individual UEs for unicast data session, also known as PDU (Protocol Data Unit) Session. This is described in 3GPP Technical Specifications 23.501 and 23.502. However, congestion can occur as the use of unicast sessions send the same data to multiple UEs increases the network resource usage. Accordingly, it is desirable for improved solutions to transmit the same data to multiple UEs which has more flexibility to handle increasing demands. 
     This background information is intended to provide information that may be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention. 
     SUMMARY 
     It is an object of the present invention to obviate or mitigate at least one disadvantage of the prior art. 
     An aspect of the disclosure provides a method for managing a group communications (GC) session. The method is performed by an Access Management Function (AMF) and includes: receiving a GC session establishment request from a session management function (SMF); transmitting to an access node, the GC session establishment request; receiving a GC session establishment response from the access node, transmitting the GC session management response to the session management function; and communicating with the access node over a service based interface to cause the access node to support a group communication session with a first UE. In some embodiments, the AMF is selected by the session management function (SMF). In some embodiments, the method includes selecting a data management function and transmitting a GC session information request to the to the data management function, and receiving a GC session information response from the data management function with the GC session information response comprising parameters of the GC session. In some embodiments, the method includes selecting a policy control function (PCF) and transmitting a GC session policy request to the policy control function (PCF), and receiving a GC session policy response from the policy control function where the GC session policy response comprising an access and mobility management policy for the GC session. In some embodiments, the AMF selects the session management function (SMF). In some embodiments, the method includes discovering the access node associated with the first UE. In some embodiments, the method includes transmitting a GC serving function registration request to the data repository function, and receiving a GC serving function registration response from the data repository function where the GC serving function registration response includes information associating a UE group and a network resource and the UE group includes the first UE. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a broadcast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a multicast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the plurality of UEs is defined by a group identifier. 
     An aspect of the disclosure provides a method for managing a group communications (GC) session. The method includes transmitting, by an Access Management Function (AMF), a discover access management function request to a network discovery function to identify a first unicast AMF. The first unicast AMF is configured to manage access and mobility for a first UE associated with an access node. The method also includes receiving, by the AMF, a GC session announcement request, sent by a session management function, transmitting, by the AMF, the GC session announcement request to the first unicast AMF, receiving, by the AMF, a GC session announcement response sent by the first unicast AMF, transmitting the GC session announcement response to the session management function, receiving, by the AMF, a GC session announcement notification sent by first unicast AMF, transmitting, by the AMF, the GC session announcement notification to the session management function, and communicating, by the AMF, with the access node over a service based interface to cause the access node to support a group communication session with the first UE. The AMF acts as a proxy for communications between the first unicast AMF and the session management function. In some embodiments, transmitting by the AMF to the first unicast AMF and receiving from the first unicast AMF by the AMF is done over the service based interface. In some embodiments, the AMF acts as a proxy for communications between a plurality of unicast access management functions (AMFs) and the session management function (SMF) and the first unicast AMF is one of the plurality of access management functions (AMFs). In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a broadcast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a multicast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the plurality of UEs is defined by a group identifier. 
     An aspect of the disclosure provides an electronic device including a network interface, a processor, and a non-transient memory for storing instructions. When executed by the processor, the instructions cause an access mobility function (AMF) of the electronic device to transmit a discover access management function request to a network discovery function to identify a first unicast AMF. The first unicast AMF is configured to manage access and mobility for a first UE associated with access node. When executed by the processor, the instructions cause the AMF to Receive from a session management function, a GC session announcement request. Transmit the GC session announcement request to the first unicast AMF. Receive from the first unicast AMF, a GC session announcement response. Transmit the GC session announcement response to the session management function. Receive from the first unicast AMF, a GC session announcement notification. Transmit the GC session announcement notification to the session management function. Communicate with the access node over a service based interface to cause the access node to support a group communication session with the first UE. The AMF acts as a proxy for communications between the first unicast AMF and the session management function. In some embodiments, transmitting from the AMF to the first unicast AMF and receiving from the first unicast AMF by the AMF is done over the service based interface. In some embodiments, the AMF acts as a proxy for communications between a plurality of unicast access management functions and the session management function, the first unicast AMF being one of the plurality of access management functions. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a broadcast communication or a multicast communication to the plurality of UEs. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
         FIG. 1  is a block diagram of an electronic device within a computing and communications environment that may be used for implementing devices and methods in accordance with representative embodiments of the present invention; 
         FIG. 2  is a block diagram illustrating a service-based view of a system architecture of a 5G Core Network with two Access Management Functions. The first AMF, AMF- 1 , is used for supporting unicast communication (or also known as PDU Session) and the second AMF, AMF- 2 , is used for supporting GC Session; 
         FIG. 3  is a block diagram illustrating a service-based view of a system architecture of a 5G Core Network with two AMFs, wherein the AMF- 2  communicates with the UE over AMF- 1 ; 
         FIGS. 4A and 4B  illustrates an embodiment of an GC Session establishment in the CN and (R)AN; 
         FIG. 5  illustrates an embodiment of an AMF- 1  GC Session announcement; 
         FIG. 6  illustrates an embodiment of an AMF- 2  GC Session announcement; 
         FIG. 7A, 7B, and 7C  illustrates an embodiment of an GC Session establishment in the CN and (R)AN; 
         FIG. 8  illustrates an embodiment of an GC Session Announcement; 
         FIG. 9  is a block diagram illustrating a service-based view of a system architecture of a 5G Core Network with two AMFs that are able to communicate with the UE. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION 
     In the following description, features of example embodiments of the present invention are described. For convenience of description, these embodiments make use of features and terminology known from communication system specifications, such as 4G and 5G networks, as defined by the Third Generation Partnership Project (3GPP). However, it shall be understood that the present invention is not limited to such networks. 
     In this specification, the term group communication (GC) Session will be used. A GC Session can include: multiple unicast sessions; one or more multicast sessions; one or more broadcast sessions; a combination of one or more unicast sessions and one or more broadcast sessions; a combination of one or more unicast sessions and one or more multicast sessions; a combination of one or more broadcast sessions and one or more multicast session, a combination of one or more unicast sessions, one or more broadcast sessions and one or more multicast sessions. A unicast session is a data session in which data is sent from a single data source to a single UE. The unicast session may also be called PDU Session. A multicast session is a data session in which data is sent from a single source to a group of authorized UEs. A broadcast session is a data session in which, data is sent from a single source to any UE that is authorized to receive the data. In some cases, the authorization for a UE to receive data of a broadcast session may be not required. 
     An aspect of the invention is directed to a core network (CN) control function (also referred to herein as a core network (CN) control plane function) within a wireless communication network for supporting GC Sessions. Such a CN control function interacts with other CN control functions, such as a Network Exposure Function (NEF), a Session Management Function (SMF) and an Access Management Function (AMF). There can be multiples of these functions. For example there can be multiple AMFs within a CN, with each AMF being associated with one or more UEs. Referring to one of these AMFs as a first AMF, the first AMF is configured to manage access and mobility for UEs including an example UE referred to as the first UE. Embodiments will be discussed in which the AMF has a defined interface (referred to as an N1 interface) for communicating with the UEs for which it is associated, and a defined interface (referred to as an N2 interface) for communicating with radio access nodes of the Radio Access Network (RAN) or non 3GPP access nodes of any Access Network, such as non-3GPP fixed or wireless access networks. In case of non-3GPP access network, an Inter-Working Function (IWF) may be required to provide signalling support between the AMF and non 3GPP access nodes. The CN control function, after receiving one or more messages from a CN of the wireless communication network, communicates with an access node of an access network, such a radio access node of a radio access network, over a control plane interface to cause the access node to support a GC Session with a plurality of UEs, including the first UE. In some embodiments the control plane interface is the N2 interface. 
     In an embodiment, the CN control function is a second AMF function that operates separately from the first AMF. It is noted that while existing networks utilize multiple AMFs, each UE may be served by a single AMF. Accordingly, it is noted that in embodiments in which the CN control function is a second AMF function that operates separately from the first AMF, both the first AMF and the second AMF can be associated with a particular UE, with the first AMF handling conventional AMF functionality for the particular UE, such as to support access and mobility management and unicast PDU Sessions of the UE, and the second AMF handling connection and mobility management for GC Sessions. 
     In another embodiment, the CN control function can be implemented in the first AMF. The CN control function can be implemented, for example, by configuring the first AMF with the functionality of the CN control function for handling connection and mobility management for GC Sessions. 
     It is noted that the CN control function can be co-located with the first AMF (e.g., both instantiated within the same network element), but still operate as separate network functions. 
     Further embodiments will be discussed using examples in which the first AMF is referred to as AMF- 1 , and the CN control function is referred to as AMF- 2 . 
     In an embodiment, the AMF- 2  does not have a logical connection, such as N1 interface, to the UE; the AFM- 2  has a logical connection to the access node, such as N2 interface or a similar N2 interface with additional messages to support GC Sessions. 
     In an embodiment, the AMF- 2  has a logical connection, such as N1 interface or similar with additional messages for supporting group communication; and the AMF- 2  has a logical interface, such as N2 interface with additional messages to support a GC Session. 
     In an embodiment, the AMF- 1  and AMF- 2  are two instances of the same AMF set. The AMF set may have a logical function to receive messages from other control plane network functions, such as session management (SM) messages from the SMF, and forward the messages received from other CN control plane functions to either the AMF- 1  or AMF- 2  according to information included in the message. 
     In the following, the CN control plane function, such as AMF- 2 , may have N1 and N2 interfaces to communicate with the UE and access node, respectively for illustrating inventive ideas. In general, the CN control plane function may have a control interface to communicate with the UE, a control interface to interact with access nodes, one or more interfaces to communicate with other CN control plane functions such as the service-based interface using design principles specified in 3GPP TS 23.501 and TS 23.502. 
     In an embodiment, the SW can select the AMF- 2  to support and handle connection and mobility management for the GC Session. 
     In an embodiment, the AMF- 2  can select SW to support GC Session. 
     In several embodiments, new functionalities may be added to the SW, which is to be specified in 3GPP TS 23.501 and TS 23.502 to handle GC Sessions. 
     In an embodiment, the new functionalities to handle group communication may be implemented in a separate CN control plane function, for example group communication SMF (GC-SMF). 
     In several embodiments, a GC Session provides data connections for a plurality of UEs to receive the same data. The data transmitted over the data connections could be one or more PDUs, or one or more data files consisting of multiple packets. In the GC Session, the Core Network (CN) establishes multiple user plane (UP) connections from a User Plane Function (UPF) to multiple (Radio) Access Network ((R)AN) nodes. Each (R)AN node may establish one or more radio channels to send group communication data to one or more UEs served by the (R)AN node. The radio channel could be a unicast radio channel, which could be implemented by data radio bearer (DRB) in 3GPP RAN, of a UE wherein the transmission parameters, including modulation and coding scheme (MCS) and precoding matrix, are selected to match the UE&#39;s radio channel propagation. The radio channel could be a multicast radio channel, wherein the transmission parameters, such as MCS and precoding matrix, are selected to support multiple radio channels of multiple UEs. The radio channel could be a broadcast radio channel, where the transmission parameters are selected to support some or any UEs currently served by the (R)AN node. 
     Those skilled in the art will appreciate that the term Group Communication (GC) session has the same meaning as GC Session. 
       FIG. 1  is a block diagram of an electronic device (ED)  102  illustrated within a computing and communications environment  100  that may be used for implementing the devices and methods disclosed herein. In some embodiments, the ED  102  may be an element of communications network infrastructure, such as an such as a radio access node (otherwise referred to as a base station) (for example a NodeB, an enhanced Node B (eNodeB), a next generation eNodeB (ng-eNodeB or ng-eNB), a next generation NodeB (sometimes referred to as a gNodeB or gNB)), a home subscriber server (HSS), a gateway (GW) such as a packet gateway (PGW) or a serving gateway (SGW) or communications network infrastructure serving as a core network (CN) that includes various functions within an evolved packet core (EPC) network. In other embodiments, the ED  102  may be a device that connects to network infrastructure over a radio interface, such as a mobile phone, smart phone or other such device that may be classified as a User Equipment (UE), referred to as UE  202  hereinafter. In some embodiments, ED  102  may be a Machine Type Communications (MTC) device (also referred to as a machine-to-machine (m2m) communication device), or another such device that may be categorized as a UE  202  despite not providing a direct service to a user. In some references, an ED  102  may also be referred to as a mobile device (MD), a term intended to reflect devices that connect to mobile network, regardless of whether the device itself is designed for, or capable of, mobility. Specific devices may utilize all of the components shown or only a subset of the components, and levels of integration may vary from device to device. Furthermore, a device may contain multiple instances of a component, such as multiple processors, memories, transmitters, receivers, etc. The ED  102  typically includes a processor  106 , such as a Central Processing Unit (CPU), and may further include specialized processors such as a Graphics Processing Unit (GPU) or other such processor, a memory  108 , a network interface  110  and a bus  112  to connect the components of ED  102 . ED  102  may optionally also include components such as a mass storage device  114 , a video adapter  116 , and an I/O interface  118  (shown in dashed lines). 
     The memory  108  may comprise any type of non-transitory system memory, readable by the processor  106 , such as static random-access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), or a combination thereof. In specific embodiments, the memory  108  may include more than one type of memory, such as ROM for use at boot-up, and DRAM for program and data storage for use while executing programs. The bus  112  may be any combination of any type of several bus architectures including a memory bus or memory controller, a peripheral bus, or a video bus. 
     The ED  102  may also include one or more network interfaces  110 , which may include at least one of a wired network interface and a wireless network interface. As illustrated in  FIG. 1 , network interface  110  may include a wired network interface to connect to a network  120 , and also may include a radio access network interface  122  for connecting to other devices over a radio link. When ED  102  is an element of communications network infrastructure, the radio access network interface  122  may be omitted from such elements that include core network control plane functions acting as elements of the core network (CN) other than those at the radio edge (e.g. an eNB). When ED  102  is infrastructure at the radio edge of a network, both wired and wireless network interfaces may be included. When ED  102  is a wirelessly connected device, such as a User Equipment (UE), radio access network interface  122  may be present and it may be supplemented by other wireless interfaces such as WiFi network interfaces. The network interfaces  110  allow the electronic device  102  to communicate with remote entities such as those connected to network  120 . 
     The mass storage  114  may comprise any type of non-transitory storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible over the bus  112 . The mass storage  114  may comprise, for example, any combination of a solid-state drive, hard disk drive, a magnetic disk drive, or an optical disk drive. In some embodiments, mass storage  114  may be remote to the electronic device  102  and accessible through use of a network interface such as interface  110 . In the illustrated embodiment, mass storage  114  is distinct from memory  108  where it is included, and may generally perform storage tasks compatible with higher latency, but may generally provide lesser or no volatility. In some embodiments, mass storage  114  may be integrated with a memory  108  to form a heterogeneous memory. 
     The optional video adapter  116  and the I/O interface  118  (shown in dashed lines) provide interfaces to couple the electronic device  102  to external input and output devices. Examples of input and output devices include a display  124  coupled to the video adapter  116  and an I/O device  126  such as a touch-screen coupled to the I/O interface  118 . Other devices may be coupled to the electronic device  102 , and additional or fewer interfaces may be utilized. For example, a serial interface such as Universal Serial Bus (USB) (not shown) may be used to provide an interface for an external device. Those skilled in the art will appreciate that in embodiments in which ED  102  is part of a data center, I/O interface  118  and Video Adapter  116  may be virtualized and provided through network interface  110 . 
     In some embodiments, ED  102  may be a standalone device, while in other embodiments ED  102  may be resident within a data center. A data center, as will be understood in the art, is a collection of computing resources (typically in the form of servers) that can be used as a collective computing and storage resource. Within a data center, a plurality of servers can be connected together to provide a computing resource pool upon which virtualized entities can be instantiated. Data centers can be interconnected with each other to form networks consisting of pools computing and storage resources connected to each by connectivity resources. The connectivity resources may take the form of physical connections such as Ethernet or optical communication links, and may include wireless communication channels as well. If two different data centers are connected by a plurality of different communication channels, the links can be combined together using any of a number of techniques including the formation of link aggregation groups (LAGs). It should be understood that any or all of the computing, storage and connectivity resources (along with other resources within the network) can be divided between different sub-networks, in some cases in the form of a resource slice. If the resources across a number of connected data centers or other collection of nodes are sliced, different network slices can be created. 
     A first embodiment will now be discussed wherein one UE may be served by two AMF functions. The first AMF, AMF- 1 , serves existing functionalities including UE access and mobility management. The AMF- 2  serves GC Session. In this first embodiment, the AMF- 2  does not have N1 connection to the UE, the AMF- 2  has N2 connections only to support GC Session. 
       FIG. 2  illustrates a service-based architecture  300  for a 5G or Next Generation Core Network (5GCN/NGCN/NCN). This illustration depicts logical connections between nodes and functions, and its illustrated connections should not be interpreted as direct physical connections. UE  202  forms a radio access network connection with a (Radio) Access Network ((R)AN) node  302  of a radio access network (RAN) (which may, for example, be an gNodeB (gNB)), which is connected to a User Plane (UP) Function (UPF)  304  such as a UP Gateway over a network interface providing a defined interface such as an N3 interface. The UPF  304  provides a logical connection to a Data Network (DN)  306  over a network interface such as an N6 interface. The radio access network connection between the UE  102  and the (R)AN node  302  may be referred to as a Data Radio Bearer (DRB). 
     Further details can be found in U.S. Patent Application Ser. No. 62/590,210 entitled “Multicast and Broadcast Services”, filed Nov. 22, 2017, which is hereby incorporated by reference in its entirety. 
     DN  306  may be a data network used to provide an operator service, or it may be outside the scope of the standardization of the Third Generation Partnership Project (3GPP), such as the Internet, a network used to provide third party service, and in some embodiments DN  306  may represent an Edge Computing network or resource, such as a Mobile Edge Computing (MEC) network. 
     UE  202  also connects to a first Access and Mobility Management Function (AMF- 1 )  308  through a logical N1 connection (although the physical path of the connection is not direct). The AMF- 1   308  is responsible for authentication and authorization of access requests, as well as mobility management functions. In a service based view, the AMF- 1   308  can communicate with other core network (CN) control plane (CP) functions  326  through a service based interface denoted as Namf. 
     The Session Management Function (SMF)  310  is a network function that is responsible for the allocation and management of IP addresses that are assigned to an UE  202  as well as the selection of a UPF  304  (or a particular instance of a UPF  304 ) for user plane traffic associated with a particular data session of UE  202 , such as PDU Session. The SMF  310  can communicate with other core network functions, in a service based view, through a service based interface denoted as Nsmf. The SMF  310  may also connect to a UPF  304  through a logical interface such as network interface N4. 
     The Authentication Server Function (AUSF)  312  provides authentication services to other network functions over a service based Nausf interface. 
     A Network Exposure Function (NEF)  314  can be deployed in the 5GCN/NGCN/NCN to allow servers, functions and other entities such as those outside a 3GPP network domain to have exposure to services and capabilities within the network. In one such example, an NEF  314  can act much like a proxy between an Application Function (AF) and/or Application Server (AS) outside the 5GCN/NGCN/NCN and network functions such as the Policy Control Function (PCF)  316 , the SMF  310 , the UDM  320 , the AMF- 1   308  and the AMF- 2   350 , so that the external the AF and/or AS can provide information that may be of use in the setup of the parameters associated with a data session. The NEF  314  can communicate with other network functions through a service based Nnef network interface. The NEF  314  may also have an interface to non-3GPP functions. 
     A Network Repository Function (NRF)  318  provides network service discovery functionality. The NRF  318  may be specific to the Public Land Mobility Network (PLMN) or network operator, with which the NRF  318  is associated. The service discovery functionality can allow network functions and UEs  202  connected to the 5GCN/NGCN/NCN to determine where and how to access existing network functions, and may present the service based interface Nnrf. 
     The PCF  316  communicates with other network functions over a service based Npcf interface, and can be used to provide policy and rules to other network functions, including those within the control plane. Enforcement and application of the policies and rules is not necessarily the responsibility of the PCF  316 , and is instead typically the responsibility of the functions to which the PCF  316  transmits the policy. In one such example the PCF  316  may transmit policy associated with session management to the SMF  310 . This may be used to allow for a unified policy framework with which network behavior can be governed. 
     A Unified Data Management Function (UDM)  320  can present a service based Nudm interface to communicate with other network functions, and can provide data storage facilities to other network functions. Unified data storage can allow for a consolidated view of network information that can be used to ensure that the most relevant information can be made available to different network functions from a single resource. This can make implementation of other network functions easier, as the other network functions do not need to determine where a particular type of data is stored in the network. 
     The Network Slice Selection Function (NSSF)  365  allows selecting the set of Network Slice instances serving the UE  202 , determining the Allowed NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs, determining the Configured NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs, determining the AMF Set to be used to serve the UE  202 , or, based on configuration, a list of candidate AMF(s), possibly by querying the NRF  318 . 
     The PCF  316  may be associated with the UDM  320  because it may be involved with requesting and providing subscription policy information to the Unified Data Repository (UDR)  321 , but it should be understood that typically the PCF  316  and the UDM  320  are independent functions. 
     The PCF  316  may have a direct interface to the UDR  321 . The UDM  320  is typically responsible for functionality such as the processing of credentials, location management and subscription management. 
     The Application Function (AF)  322  represents the non-data plane (also referred to as the non-user plane) functionality of an application deployed within a network operator domain and within a 3GPP compliant network. The AF  322  interacts with other core network functions through a service based Naf interface, and may access network capability exposure information, as well as provide application information for use in decisions such as traffic routing. The AF  322  can also interact with functions such as the PCF  316  to provide application specific input into policy and policy enforcement decisions. It should be understood that in many situations the AF  322  does not provide network services to other network functions, and instead is often viewed as a consumer or user of services provided by other network functions. An application outside the 3GPP network, can perform many of the same functions as the AF  322  through the use of NEF  314 . 
     The UE  202  communicates with network functions that are in the CN User Plane (UP)  324 , and the CN Control Plane (CP)  326 . The UPF  304  is a part of the CN UP  324  (DN  306  being outside the 5GCN). The (R)AN node  302  may be considered as a part of a User Plane, but because it is not strictly a part of the CN, it is not considered to be a part of the CN UP  324 . The AMF- 1   308 , SMF  310 , AUSF  312 , NEF  314 , NRF  318 , PCF  316 , and UDM  320  are functions that reside within the CN CP  326 , and are often referred to as CN Control Plane Functions. AF 322 may communicate with other functions within CN CP  326  (either directly or indirectly through the NEF  314 ), but is typically not considered to be a part of the CN CP  326 . 
     Those skilled in the art will appreciate that there may be a plurality of UPFs connected in series between the (R)AN node  302  and the DN  306 , and multiple data sessions to different DNs can be accommodated through the use of multiple UPFs in parallel. 
     In the architecture illustrated by  FIG. 2 , the AMF- 1   308  is selected when UE  202  performs the UE Registration procedure. 
     In one embodiment of the service-based architecture  300  illustrated in  FIG. 2 , UE  202  is simultaneously connected to both unicast and GC Sessions, and the AMF- 2   350 - 1  has no N1 connection to UE  202 . Accordingly the AMF- 2   350 - 1  does not send messages to UE  202  directly. The AMF- 2   350 - 1  supports CN functions to establish and manage the GC Session. AMF- 1   308  supports CN functions in order to exchange messages between UE  202  and CN functions. The AMF- 2   350 - 1  may support all functionality of AMF- 1   308 . In addition, the AMF- 2   350 - 1  may support functionality related to GC Session operations, including establishing, modifying, and releasing one or more GC Sessions. The SMF  310  may send control plane messages related to GC session for UE  202  via the AMF- 1   308 ; and the SMF  310  may send control plane messages to the (R)AN node  302  via the AMF- 2   350 - 1 . 
     In another embodiment of the service-based architecture  400  illustrated in  FIG. 3 , the AMF- 2   350 - 2  has no connection to the UE  202  but is capable of communicating with AMF- 1   308  through a logical interface, such as network interface N14. The SMF  310 - 2  sends N1 session management (SM) messages related to GC Session to the AMF- 2   350 - 2  and the AMF- 2   350 - 2  forwards the SM messages from SMF  310 - 2  to AMF- 1   308  through the service based interface Namf, which is also referred to as N14 reference point. The AMF- 1   308  supports CN functions to exchange messages between UE  202  and the AMF- 2   350 - 2 . The AMF- 2   350 - 2  supports message exchanges between the AMF- 1   308  and the SMF  310 - 2 . In the service-based architecture shown in  FIG. 3 , the MSF  310 - 2  has some or all the functionalities of the SMF  310 - 1  shown in the service-based architecture of  FIG. 2 , with additional functionality described above. Similarly, the AMF- 2   350 - 2  has some or all the functionalities of the AMF- 2   350 - 1  shown in the service-based architecture of  FIG. 2 , with additional functionality described above. Hereinafter, the MSF  310 - 1  and MSF  310 - 2  are generally referred to as MSF  310 , and collectively as SMFs  310 , and AMF- 2   350 - 1  and AMF- 2   350 - 2  are generally referred to as AMF  350 , and collectively as AMFs  350 . 
     In another embodiment of the service-based architecture  300  illustrated by  FIG. 2 , when UE  202  has simultaneous unicast and GC Sessions, the functionality of the core network control function (the AMF- 2   350 ) may be incorporated within the AMF- 1   308  and such an enhanced the AMF- 1   308  may serve all the UEs  202  that join the GC Session in its service area. 
     When two different AMF functions are selected, the AMF- 1   308  supports the unicast PDU session functions and the AMF- 2   350  supports GC Session functions. The AMF- 1   308  is also used to transfer messages between UE  202  and core network functions related to GC Session. 
     In some embodiments, AMF- 1   308  may receive GC Session related configuration messages from SMF  310  that are to be sent to UE  202 . This means that the SMF  310  may send the same information related to GC Sessions to multiple AMFs, when UEs joining GC Session are served by different AMFs. In some embodiments, the AMF- 1   308  may also receive GC Session messages from UE  202 . In some embodiments, the AMF- 1   308  may forward the GC Session messages received from UE  202  to a CN function, such as the MSF  310 , AMF- 2   350 , PCF  316 , NEF  314 , AF  322 , Network Data Analytics Function (NWDAF)  319 , and to a Network Management Function (NMF) (not shown) such as Operation, Administration, and Maintenance (OAM) system (not shown). The NWDAF  319  is a control plane function. The NWDAF  319  can collect network data and run data analytics algorithm to provide operational statistics, predictions, and recommendations to other network functions and OAM system, which is part of network management function (NMF). In some embodiments, the AMF- 1   308  may also create and send GC Session messages to UE  202 . 
     In some embodiments, the AMF- 2   350  may receive GC Session messages that are to be sent to the (R)AN node  302  from the CN functions such as MSF  310 , PCF  316 , NWDAF  319 . In some embodiments, the AMF- 2   350  may create and send messages related to GC Session to the (R)AN. In some embodiments, the AMF- 2   350  may receive GC Session messages from the (R)AN node  302  which the AMF- 2   350  forwards to CN functions such as MSF  310 , PCF  316 , NEF  314 , NWDAF  319 , and to the OAM system of the NMF. 
       FIG. 4A  illustrates an embodiment of GC Session establishment in the CN and the (R)AN node  302 . The following are the steps of  FIG. 4A . 
     Step  1 : AF  322  may send a GC Session establishment request message  502  to NEF  314 . The GC Session establishment request message  502  may include GC session information including any combination of the following information: AF Transaction ID, AF-Service-ID, External Group ID and/or Internal Group ID of UEs that receive the GC data, a list of UE IDs (such as External UE ID, or GPSI (Generic Public Subscription Identifier)), GC Session location information (or Group communication service area) (such as any combinations of one or multiple Geographical Zone IDs, one or multiple identifiers of (R)AN nodes (such as any combinations of (R)AN IDs, (R)AN IP addresses, list of cell identifiers (Cell IDs) of each (R)AN nodes), one or multiple tracking areas, one or multiple SMF service areas, one or multiple AMF service areas, one or multiple registration areas, or an indication of the whole PLMN, number of data flows, name or identifier of each data flow, QoS requirements of each data flows and/or QoS requirements of the GC Session, such as any combinations of maximum flow data rate, maximum data rate of GC session, average data rate of flow(s) and/or of GC session, packet delay budget or each flow and/or of GC session, expected or maximum data volume in a certain period of time of each flow and/or of GC session, Network Slice Information such as any combinations of S-NSSAI, DNN, Application identifier, type of data such as IP data, unstructured data, or Ethernet data, how the group communication data will be sent to the network (for example over NEF control plane or UPF user plane), AS information. The AF  322  may include a message, may be called AF-to-UE message, for the UE  202  such that the CN may transparently send to the UE  202  when the CN, such as the MSF  310 , sends GC Session announcement messages to the UE  202 . This step could be implemented by a new service of the NEF  314 , such as, Nnef_GCSession_Create_Request that are discussed in further detailed below. 
     The AS information may be one or more of following information: type of data (IP data, Ethernet data, unstructured data), IP packet description or Ethernet packet description. The IP packet description may include one or more of following information: IP version (IPv4 or IPv6), source IP Addresses or IP Prefixes, source UDP or TCP port number, Type of Service (TOS) (IPv4)/Traffic class (IPv6) and Mask, Flow Label (IPv6), Security parameter index. 
     The Ethernet packet description may include Source MAC address, Ethertype as defined in IEEE 802.3, Customer-VLAN tag (C-TAG) and/or Service-VLAN tag (S-TAG) VID fields as defined in IEEE 802.1Q, Customer-VLAN tag (C-TAG) and/or Service-VLAN tag (S-TAG) PCP/DEI fields as defined in IEEE 802.1Q, IP Packet Filter Set, in the case that Ethertype indicates IPv4/IPv6 payload. 
     Step  2 : The NEF  314  may perform SMF selection  504  by any one or more of the following methods: 
     (1) pre-configured SMF information wherein SMF selection  504  is based on GC Session information stored in the NEF 314. For example, the NEF  314  may have a mapping between GC Location information to SMF ID, or External Group ID to SMF ID, or Network Slice information to SMF ID, Application Type and/or Application ID to SMF ID, or any combination of GC information to SMF ID. 
     (2) The NEF  314  may request NRF  318  function to get SMF  310  information by using, for example a service of NRF  318 . The NEF  314  may send the one or more of following information to NRF  318  for SMF selection  504 : Network Slice Information (S-NSSAI), DNN, Internal Group ID, NF type indicating SMF function that can support GC Session management, AF-Service-Identifier (or AF Identifier), Application Identifier, Application Type (e.g. V2X application, IoT application, Video streaming application, TV broadcasting application). NRF  318  returns the SMF profiles, which may include Address information such as SMF ID, and/or SMF FQDN, and/or SMF IP Address(es), and/or SMF Endpoint Address(es). The NEF  314  may have a mapping between External Group ID and Internal Group ID and provides the NRF  319  with Internal Group ID or External Group ID. 
     (3) The NEF  314  may request the UDM  320  or the UDR  321  to obtain the GC Session binding information. The GC Session binding information provides a mapping between AF-Service-Identifier ID (or AF Identifier, or External Group ID) and/or network slice information (e.g. S-NSSAI) and/or DNN with SMF Address information. The UDM  320  may have SMF function information or SMF instance information that is preconfigured to serve specific AF(s)&#39; GC Sessions. 
     Step  3 : The NEF  314  may send a GC Session establishment request message  506  to the selected MSF  310 , including the information received from the AF  322 . In case the group communication data is sent to NEF  314 , NEF  314  may include an uplink tunnel end point identifier (TEID) for the UPF  304  to send the message to NEF  314  for acknowledgement of successfully received data or request for retransmission of missing packets. The uplink TEID of the NEF  314  may be sent to the SMF  310  in a separate message. The GC Session establishment request may be implemented using SMF service request Nsmf_PDUSession_Create and modified as discussed below when detailed examples of operations is discussed. In some embodiments, NEF  314  includes an indication requested PDU type of GC Session such as “GC Session Type”. 
     Note that in some embodiments, the AF  322  may be configured to send GC Session Establishment Request directly to a preconfigured the MSF  310 . The AF  322  may include the same information as described in Step  1 . Hence, in this embodiment, Steps  2  and  3  can be omitted. 
     Step  4 : The SMF  310  may generate a group TMGI (Temporary Mobile Group Identity) for the UE  202  that joined the GC Session. One internal-group ID of a UE group may have multiple TMGIs, each TMGI may be used to represent different GC Session. The SMF  310  may also generate a GC Session ID. The TMGI may be also be used as GC Session ID. The SMF  310  may select a UDM  320  to get the information related to GC Session. The SMF  310  may use local information stored within SMF  310  to select a UDM  320  to serve GC Session. The SMF  310  may access NRF  318  to discover a UDM  320  by sending Nnrf_NFDiscovery_Request message. The SMF  310  may provide NRF  318  with any combination of the following to select a UDM  320 : AF-Service-Identifier, Application information including Application ID, type of application (e.g. video multicast or broadcast, voice multicast or broadcast, V2X data multicast or broadcast), UE Group Information (e.g. External Group ID and/or Internal Group ID, and/or TMGI), network slice information (e.g. S-NSSAI), and DNN. After selecting a UDM  320 , the SMF  310  may send a message, such as a GC Session information request message  508 , to the UDM  320  to get GC Session related information. The GC Session information request message  508  may include some or all of the session information contained in the received GC Session establishment request message described in step  3 . The GC Session information request message  508  may be implemented using the Nudm SDM Get service of UDM  320 . The SMF  310  may request UDM  320  to provide AMF- 1   308  information. The SMF  310  discovers AMF- 1   308  by sending a request, for example Discover AMF- 1  Request, to UDM  320 . For example, SMF  310  may use the UDM Nudm_UECM_Get service. The SMF  310  may provide any combination of the following to the UDM  320 : UE information including any combination of UE ID (e.g. SUPI (Subscription Permanent Identifier), or GPSI, Temporary Mobile Station Identifier (TMSI)), Internal Group ID, TMGI, and NF type (is AMF function type), and Access Type (e.g. 5G (R)AN, WiFi, 3GPP, non-3GPP). The SMF  310  may also implicitly register itself with the UDM  320  as a serving SMF function for the GC Session. Alternatively, the SMF  310  may explicitly register itself with the UDM  320  as a serving SMF function of the GC Session using Nudm_UECM_Registration service and with modification that will be discussed under detailed examples of operations below. The SMF  310  may provide GC Session ID and/or TMGI, AF-Service-Identifier, Internal Group ID, network slice information (e.g. S-NSSAI), and DNN. 
     In the Discover AMF- 1  Request, the SMF  310  may include an indication, whether the SMF  310  wants to discover the serving AMF- 1   308  of each UE  202 , or only the list of AMF-1s  308  that serve the UEs  202 . 
     Step  5   a:  Following receipt of the GC Session information request message  508  from MSF  310 , the UDM  320  may send a request, for example a GC Session information request message  510 , to UDR  321  to get GC Session related information. The GC Session information request message  510  may include the AF-Service-Identifier ID, External Group ID, network slice information (such as S-NSSAI), and DNN. If the UDM  320  has the mapping between External Group ID and UE Group ID (e.g. Internal-Group ID), the UDM  320  may also include the Internal-Group ID. UDM  320  may create a TMGI, if it is not created by the SMF, and also sends this information to UDR  321 . The GC Session information request illustrated by step  5   a  may be implemented using the UDR  321  Nudr_DM_Query service to request GC Session management subscription data. The UDM  320  may include an AF-Service-Identifier, or Internal Group Identifier in this GC Session information request. 
     Step  5   b:  Following receipt of the GC Session information request message  510  from UDM  320 , UDR  321  sends a GC Session information response message  512  to UDM  320 . The GC Session information response message  510  may include UE Group ID (e.g. Internal-Group ID), list of UE IDs of UEs (such as SUPI, or GPSI) in the UE Group, Location Information of GC Session (e.g. Addresses of RAN nodes (otherwise referred to as RAN node addresses) and/or Cell ID(s) of the each RAN nodes, Geographic Zone ID(s)), and Network Function information if available (e.g. serving AMF ID or AMF Address, UPF ID(s) or UPF Address(es), NEF ID or NEF Address). The GC Session information response message  512  may be implemented using the UDR Nudr DM Query response. 
     Step  6 : The UDM  320  sends a message, e.g. GC Session Information Response message  514 , to the SMF  310  which includes information received from UDR  321  as described in step  5   b  or the information that already available in the UDM  320  so that the UDM  320  does not need to perform step  5   a  or does not need to obtain from the UDR  321 . The UDM  320  may also send any combination of the following information to MSF  310 : Internal-Group ID (if the UDM stores the Internal-Group ID) and/or the TMGI (if the UDM created group TMGI), list of UE IDs (such as GPSI or SUPI), Subscription information related to UE Group (e.g. Maximum bit rate of GC Session, Maximum traffic volume in a certain period), Network Slice Information (e.g. S-NSSAI) that may be used by the SMF  310  to select one or multiple UPF  304  to serve GC Session. The GC Session Information Response message  514  described in step  6  may be implemented by using UDR service response Nudm SDM Get. If the SMF  310  sent a Discovery AMF- 1  message in step  4 , the UDM  320  sends Discovery AMF- 1  Response to SMF  310  to inform SMF  310  of the AMF information (such as AMF ID, or FQDN, or AMF Address). The UDM  320  may use the Nudm_UECM Get response service to send a Discovery AMF- 1  Response message. The UDM  320  may either send the list of AMF ID(s) (or AMF Address(es) or FQDN(s)), or the list of mapping between UE and AMF, depending the Discovery AMF- 1  Request of the SMF  310  in step  4 . Some SMF and AMF instances may be configured to serve certain geographic areas called service area, and/or UE(s), and/or UE group(s), and/or application(s), and/or network slice instance(s), and/or DNN, and/or group communication service. The SMF  310  may use the UE location information provided by the UDM  320 , and stored in the AMF- 1   308 , to select the appropriate AMF- 2   350 . For example, SMF  310  may request AMF- 1   308  to provide the location of the UE  202  using AMF- 1   308  service Namf Location ProvidePositioninglnfo. 
     Step  7 : The SMF  310  may perform PCF selection 516 according to some criteria. The additional information to perform PCF selection 516 may be AF-Service-Identifier which is used to identify AF  322  and/or AS 402. 
     Step  8 : SMF  310  may have local policy control and charging (PCC) rules for the GC Session. The PCC rules may include similar information that may be provided by the PCF  316 . The SMF  310  may send a message (e.g. GC Session Policy Request message  518 ) to the selected PCF  316  to get the GC Session policies. The GC Session Policy Request message  518  may include any combination of following information: an UE Group ID (e.g. Internal-Group ID and/or TMGI), AF-Service-Identifier, Network Slice Information (e.g. S-NSSAI), DNN, name(s) or identifier(s) of data flows of GC session, Application ID, Application Type. The GC Session policy request message described in step  8  may be implemented by using a Npcf_SMPolicyControl_Create Request to establish a session with the PCF  316  and get the default PCC Rules for the GC Session. 
     In step  8 , SMF  310  may also send GC Session policy request message  518  to UDM  320  to get GC Session information such as subscribed QoS parameters, including any combinations of 5 QI, ARP, maximum flow bit rate of flow(s) and/or of GC session, and expected or maximum GC traffic volume of individual data flow(s) and/or GC session over a certain period of time. The maximum GC flow bit rate is the limit of the bit rate measured over an averaging window that the Application Server may send to the Core Network over UPF  304  or NEF  314 . UDM  320  may request the GC Session information stored in UDR  321  be sent to MSF  310 . 
     Step  9   a:  In order to make policy decision, the PCF  316  may send a message, e.g. GC Session Information Request message  520 , to UDR  321  to get GC Session related information. The GC Session Information Request message  520  may be implemented using the Nudr UDM Query service in order to receive the GC Session information. The GC Session Information Request message  520  may also include any combination of Internal-Group ID, AF-Service-Identifier, name(s) or identifier(s) of data flows, Application Type, Application ID, Policy Data, GC Session policy control. PCF  316  may request notifications from UDR  321  about changes in the subscription information by invoking Nudr DM Subscribe. Information provided during invocation of Nudr DM Subscribe includes: Internal-Group ID, AF-Service-Identifier, Policy Data, Notification Target Address (Notification Correlation Id), Event Reporting Information (continuous reporting), GC Session policy control. This message may also include an Internal-Group ID, AF-Service-Identifier, network slice information (e.g. S-NSSAI), DNN, received in Step  8 . 
     Step  9   a  is optional and is used if PCF  316  doesn&#39;t have enough information to make its policy decision. 
     Step  9   b:  Following receipt of the GC Session information request message  520  from PCF  316 , UDR  321  may send a message, e.g. GC Session Information Response message  522 , to PCF  316 . The GC Session Information Response message  522  may contain information on GC subscription information such as: QoS requirements, charging information, and Access Type (e.g. 5G RAT or 4G RAT), UE subscription information. QoS requirements in this message may include resource type (e.g. Guaranteed Bit Rate (GBR), delay critical GBR, or non-GBR), maximum flow bit rate of individual data flow(s) and/or GC session, guaranteed flow bit rate of individual data flow(s) and/or GC session, packet delay budget, expected or maximum GC traffic volume in certain period of time. UE subscription information in this message may include Service Level Agreement, QoS policy, charging policy, traffic routing policy (Access type(s)). The GC Session Information Response message  522  may be implemented by using Nudr UDM Query response service. 
     Step  10 : The PCF  316  may send a message, e.g. GC Session Policy Response message  524 , to MSF  310 . The GC Session Policy Response message  524  may include Policy and Charging Control rules for the GC Session such as policy and charging policy (PCC) information. The GC Session Policy Response message  524  may be implemented by using Npcf_SMPolicyControl_Create response service. The PCC may include QoS control, which refers to the authorization and enforcement of the maximum QoS that is authorized for a GC Session and/or service data flows in the GC Session. 
     The authorized QoS for a GC Session and/or a service data flow template may include a 5G QoS Identifier (5 QI). For 5 QI of GBR type, the authorized QoS for each service data flow of GC Session may include any combination the ARP (allocation and retention priority), MBR (Maximum flow bit rate), GFBR (guaranteed flow bit rate) and may include a request for notification when authorized GFBR cannot be fulfilled or can be fulfilled again. For 5 QI of non-GBR type, the authorized QoS may include the ARP and the Reflective QoS indication; if no ARP is included a default ARP applies for the service data flow template. The authorized QoS for a service data flow template may also refer to QoS characteristics. 
     QoS control also refers to the authorization and enforcement of the GC Session AMBR and default 5 QI/ARP combination. The PCF  316  may provide the authorized GC Session AMBR and the default 5 QI and ARP combination as part of the GC Session information for the GC Session to the MSF  310 . The authorized GC Session AMBR and authorized default 5 QI/ARP values takes precedence over other values locally configured or received at the MSF  310 . 
     Step  11   a:  The SMF  310  may send a GC Session establishment request message  526  to UPF  304 . The GC Session establishment request message  526  may include any combination of the following information:
         GC UP Information: the RAN information (IP Addresses of RAN  302  nodes, and UL TE ID if SMF can provide), DL Tunnel Endpoint ID (TEID) of each (R)AN  302  node or a common DL TEID used by all (R)AN  302  nodes if the SMF  310  assigns the DL TEID, error correction protocol for the UP tunnel connection between (R)AN  302  node and UPF  304  or between the (R)AN  302  node and the NEF  314  that RAN  302  may use;   N6 interface information, which is one or more of following information: IP Address or IP Prefix and Port number that the UPF  304  may use to communicate with the Application Server (AS)  402 , packet flow description for the UPF  304  to detect packets belonging to the GC Session, transport protocol between the UPF  304  and the AS  402  in case the AS  402  sends the downlink group communication packets or files to the UPF  304 ;   UP information for connection between the UPF  304  and the NEF  314  in case the AF  322  sends DL GC packets or files to the NEF  314 ;   QoS policy, which is one or more of following information for each service data flow of GC Session: Resource Type, Maximum flow bit rate, guaranteed flow bit rate, packet delay budget for the UPF, expected or maximum group communication traffic volume in a certain period of time; and/or QoS policy for GC Session, which is one or more of following information: Resource Type, AMBR, default ARP, guaranteed bit rate, packet delay budget for the UPF, expected or maximum group communication traffic volume in a certain period of time;   Charging policy: The charging could be based on connection time, packet counting, traffic volume counting or any combinations of the charging method. The charging policy may include the indication to instruct the UPF  304  how to process the packets when the charging reaches the limit, such as the limit of connection time, and/or the limit of the number of packets, and/or the limit of traffic volume. In one embodiment, the charging policy may instruct the UPF  304  to drop the packets when the limit reaches, or to buffer the packets, or to keep sending the packets to the (R)AN  302  node(s). The UPF  304  may notify the SMF  310  when the limit is reached.       

     Step  11   b:  Following receipt of the GC Session establishment request message from SMF  310 , the UPF  304  establishes resources to serve GC Session. The UPF  304  sends a GC Session establishment response message  528  to MSF  310 . If the UPF  304  is in charge of generating TEID, the GC Session establishment response message  528  may include the UL TEID for the (R)AN node  302  to send acknowledgement message for successful packets or file receipt or request the UPF  304  or the NEF  314  to retransmit missing packets. 
     Step  11  may be performed before step  12  or after as described further below. 
     Step  12 : The SMF  310  may perform AMF- 2  selection  530  and the selected AMF- 2   350  sends SM messages to the RAN node  302  nodes using one of the following methods: (1) AMF information that is pre-configured in MSF  310 ; (2) SMF  310  may obtain the AMF information from UDM  320  in step  4 ; (3) SMF  310  may request NRF  318  get the AMF address. In method (3), the SMF  310  may provide the NRF  318  with any combination of following information: application information (e.g. AF-Service-Identifier, and/or Application ID, and/or Application Type), Network Slice Information (e.g. S-NSSAI), Geographic location of group communication service that provided by the AF in step  1  (e.g. Geographic Zone ID(s), or (R)AN Addresses), UE information (e.g. UE IDs (such as SUPI), UE location). NRF  318  uses this information to select the AMF- 2   350 . 
     Step  13 : The SMF  310  may send a GC Session establishment request message  532  to the AMF- 2   350 ,  355 . The GC Session establishment request message  532  may be implemented by using the AMF- 2  service Namf_Communication N1N2MessageTransfer Request. The GC Session establishment request message  532  may include any combination of:
         SMF ID;   Network Slice Information (such as S-NSSAI);   An identifier to identify the group communication, such as GC Session ID and/or TMGI; and   RAN information, such as Geographic Zone ID(s), or list of Address(es) or ID(s) of RAN  302  nodes to join the GC Session, and list of Cell IDs of each RAN  302  node.   UPF information: UPF Address and UL TEID. The UL TEID may be used by RAN node  302  to communicate with the UPF  304 , such as to request UPF  304  resend missing packets or to acknowledge the successful reception of packets or files;   UE Information: Internal Group ID, TMGI, List of UE IDs (such as SUPI, GPSI, or 5G Globally Unique Temporary Identifier (5G GUTI)), or any UEs in case of broadcast session;   QoS Profile for GC Session, which may include QoS Profiles for Service data flows. Each service data flow of GC Session may have a separate QoS Profile. The QoS Profile for each service data flow may have one or more information:
           a 5G QoS Identifier (5 QI),   an Allocation and Retention Priority (ARP).   For each GBR QoS Flow, the QoS profile shall also include the QoS parameters:
               Guaranteed Flow Bit Rate (GFBR) in downlink (DL); and   Maximum Flow Bit Rate (MFBR) in DL; and   In the case of a GBR QoS Flow only, the QoS parameters may also include:   Notification control.   Maximum Packet Loss Rate   
               
           The QoS Profile for the GC Session may include any combination of QoS Profile(s) of Service Data Flow(s), GC Session-AMBR, default ARP for GC Session, Default 5 QI, guaranteed bit rate of GC Session, packet delay budget of GC Session, expected or maximum GC traffic volume in a certain period of time. In case there is only one service data flow, the QoS Profile of GC Session may not have QoS Profile of service data flow.   Error Correction protocol in the interface connecting (R)AN node  302  and UPF  304 . The (R)AN node  302  uses this tunnel to request retransmission of missing PDU packets;       

     In step  13 , the SMF  310  may send information to the AMF- 2   350 . The AMF- 2   350  may create multiple N2 mobility management (MM) message from the information receive from SMF  310 . The AMF- 2   350  may then send each N2 MM message to each (R)AN node  302 . Alternatively, SMF  310  may send multiple N2 SM messages, each message has one (R)AN ID (or Address, FQDN) for one (R)AN node  302 . The AMF- 2   350  later will forward each N2 SM message to the (R)AN node  302 . 
     In step  13 , the SMF  310  may send Geographic Zone ID(s) to the AMF- 2   350 . The AMF- 2   350  may have locally stored information to map the Geographic Zone ID to the (R)AN address(es). Alternatively, the AMF- 2   350  may send a request to the UDM  320  to get the mapping between Geographic Zone ID to the (R)AN address(es) and may also include the list of Cell ID(s) of each (R)AN node that join the GC Session. Alternatively, if the SMF  310  provides a list of UE IDs (such as SUPI, or GPSI), the AMF- 2   350  may use a service Nudm SDM Get of UDM  320  to get the last known location of the UE  202 . The UE location may be represented by, for example, the (R)AN ID or cell ID of (R)AN node  302 , and may be stored in the UDR. The UDM  310  may use a service Nudr_DM_Query to get the last known location of UE  202 . 
       FIG. 4B  illustrates an embodiment of an GC Session establishment in the CN and (R)AN. The following are the steps of  FIG. 4B  and the steps relate to the architectures shown in  FIG. 2  and  FIG. 3 . 
     Step  14   a:  the AMF- 2   350  may create an N2 control channel between the AMF- 2   350  and each (R)AN node  302  that is included in step  13 . This N2 control channel is used to exchange control signaling including the internal Group ID and/or GC Session ID, and/or TMGI. The AMF- 2   350  may forward the GC Session establishment request message  536  to (R)AN node  302 . The AMF- 2   350  may request (R)AN node  302  establish a control channel between the AMF- 2   350  and (R)AN node  302  to exchange signaling information. 
     Step  14   b:  If the resource type is a Guaranteed Bit Rate (GBR), RAN node  302  may respond to the GC Session Establishment Request message  536  from the AMF- 2   350  by reserving radio resources for the GC Session according to the QoS Profile of GC Session. Each (R)AN node  302  then sends a GC Session establishment response message  538  to the AMF- 2 . The GC session establishment response message  538  may include DL TEID in case (R)AN node  302  is in charge of assigning DL TEID.
         If the AMF- 2   350  sent N2 MM message to carry GC Session establishment request message  536  in step  14   a,  (R)AN node  302  sends an N2 MM response message in step  14   b  to carry GC Session establishment response message  538 .   If SMF  310  sent N2 SM message to carry GC Session establishment request message  536  in step  14   a,  the (R)AN node  302  sends an N2 SM response message in step  14   b  to carry GC Session establishment response message  538 .       

     If the (R)AN node  302  does not have resource for GC Session using a multicast and/or broadcast radio channel, the (R)AN node  302  may indicate in the GC session establishment response message  538  the unavailability of the multicast and/or broadcast radio channel. The (R)AN node  302  may use unicast radio channel (such as DRB) to send GC data to the UEs  202 . The (R)AN node  302  may include (R)AN information (such as TEID(s) of N3 interface, each corresponds to the unicast radio channel(s) and (R)AN address) in the GC session establishment response message  538  in step  14   b.  Alternatively, the (R)AN node  302  may include only one common TEID for the N3 interface for the UPF  304  to send GC data to the (R)AN node  302 ; the (R)AN node  302  may distribute the GC data received from the N3 interface and distributes over multiple unicast radio bearers to multiple UEs. 
     Step  15 : The AMF- 2   350  sends a GC Session establishment response message  540  to the MSF  310 . The AMF- 2   350  may use Nsmf_PDUSession_UpdateSMContext_Request with additional information elements to deliver the GC session establishment response message  538  received from (R)AN node 302. If the DL TED is included in the GC Session establishment response message  538  received from (R)AN node  302 , the SMF  310  sends a GC Session establishment or modification request message  52  to UPF  304  to provide the DL TEID. 
     Step  16   a:  If step  11   a  has not been performed, the SMF  310  may send a GC Session establishment request message (illustrated as GC Session establishment (or modification) message  542  in  FIG. 4B ) to UPF  304 . If step  11   a  has been performed, the SMF  310  may send a GC Session modification request message (illustrated as GC Session establishment (or modification) message  542  in  FIG. 4B ) to the UPF  304 . The GC Session establishment message or the GC Session establishment modification message may include any combination of the information as described for GC Session establishment request message  532  in step  11   a.  If the (R)AN provided the DL TEID(s) in GS Session establishment response message  538 , the SMF  310  also sends in GC Session establishment or modification request message  542  the DL N3 tunnel information, which include (R)AN Address(es) or (R)AN ID(s), or (R)AN FQDN(s), and corresponding DL TEID(s) of (R)AN node(s). 
     Step  16   b:  Following receipt of the GC Session establishment or modification request message  542  from MSF  310 , the UPF  304  establishes or modifies resources to serve the GC Session. The UPF  304  may send a GC Session establishment or modification response message  544  to the MSF  310 . 
     Step  17   a:  SMF  310  may send a GC session registration request message  546  to the PCF  316  to initiate a GC Session registration process with the PCF  316  to activate a mapping between GC Session ID and UE Group ID (e.g. Internal Group ID, TMGI), or a mapping between the IP Address/Prefix that was assigned to the UPF  304  in step  11   a  and/or step  16   a.  This mapping is used for the PCF  316  to update dynamic policy control for SMF  310  to control the GC Session policies. The GC Session registration request message  546  may be implemented using Npcf_SMPolicyControl_Update_Request service of PCF  316  with modification discussed under detailed examples of operations below. 
     Step  17   b:  The PCF  316  may send a GC Session registration response message  548  to SMF  310  to confirm the reception of the GC session registration request message  546  in step  17   a.  The GC Session registration response message  548  may be implemented using the PCF  316  service Npcf_SMPolicyControl_Update Response with modification discussed under detailed examples of operations below. 
     Step  18   a:  The SMF  310  may also send a GC severing function registration request message  550  to initiate a registration process with UDM  320  to register itself as a serving SMF function for the GC Session ID. This registration may be performed if not done in Step  4 . The SMF  310  may use Nudm_UECM_Registration Request service with modification discussed under detailed examples of operations below. The SMF  310  may include one or more of following parameters in its Nudm_UECM_Registration Request: SMF ID, Internal Group ID, TMGI, GC Session ID, List of UE IDs (such as SUPI, GPSI). The UDM  320  use the provided information for later communication if the UDM  320  wants to update GC Session data to the MSF  310 . 
     Step  18   b:  The UDM  320  may send a GC serving function registration response message  552  to SMF  310  that is similar to the GC Session Information Response message  514  sent in step  6 . In some embodiments, the Nudm_UECM_Registration Response service with modification discussed under detailed examples of operations below may be used to send the GC serving function registration response message  552 . 
     Step  19   a:  The AMF- 2   350  may send a GC service function registration request message  554  to UDM  320  to initiate a registration process with UDM  320  to register itself as a serving AMF function for the GC Session. The AMF- 2   350  may use Nudm_UECM_Registration Request service with modification discussed below when detailed examples of operations are discussed. The AMF- 2   350  may include one or more of following parameters in its Nudm_UECM_Registration Request: AMF ID (or AMF IP address), Internal Group ID, TMGI, GC Session ID, List of UE IDs (such as SUPI, GPSI), GC Session Location(s) that the AMF- 2   350  serves UEs. 
     Step  19   b:  UDM  320  may send a GC serving registration response message  556  to the AMF- 2   350 . In some embodiments, the Nudm_UECM_Registration Response service with modification discussed under detailed examples of operations below may be used to send the GC serving registration response message  556 . 
     Step  20   a:  The SMF  310  may confirm the completion of GC Session establishment process by sending GC Session Establishment Response message  558  to the network function that sent the GC Session establishment request message  508  in Step  3 . In case the NEF  314  is used for the AF  322  or AS  402  to send GC data to the UEs  202 , the NEF  314  may send the GC session establishment request based on the GC Session request from the AF  322 , the SMF  310  may include AF-Service-ID, AF Transaction ID, Internal Group ID, GC Session ID and/or TMGI, UPF information such as UPF Address(es) and DL TEID for the NEF to send DL packets to the UPF(s), UPF information for the AS  402  to send DL GC data to the UPF  304 .
         If GC Session carries IP traffic: the UPF information may include any combination of IP version (IPv4 or IPv6), source IP Addresses or IP Prefixes, source UDP or TCP port number, Type of Service (TOS) (IPv4)/Traffic class (IPv6) and Mask, Flow Label (IPv6), Security parameter index. The Ethernet packet description may include Source MAC address,   If GC Session carries Ethernet traffic: the UPF information may include any combination of Ethertype as defined in IEEE 802.3, Customer-VLAN tag (C-TAG) and/or Service-VLAN tag (S-TAG) VID fields as defined in IEEE 802.1Q, Customer-VLAN tag (C-TAG) and/or Service-VLAN tag (S-TAG) PCP/DEI fields as defined in IEEE 802.1Q, IP Packet Filter Set, in the case that Ethertype indicates IPv4/IPv6 payload.       

     In some embodiments, the Nsmf PDUSession Create Response service of the SMF  310  and modified as discussed under detailed examples of operations below may be used to send the GC Session Establishment Response message  558 . 
     Step  20   b:  If the SMF  310  provided Internal Group ID in step  20   a,  the NEF  314  may map Internal Group ID to External Group ID. The NEF  314  may then confirm the completion of the GC Session establishment process by sending a GC Session establishment response message  560  to AF  322  that sent the GC Session establishment request message  502  in Step  1 . The NEF  314  may include any combination of following information: AF-Service-ID, AF Transaction ID, External Group ID, GC Session ID and/or TMGI, UPF or NEF information, such as IP Address(es) UDP port number, data transmission protocol (e.g. HTTP) in this message. In some embodiments, the NEF service Nnef PDUSession Create Response (or in other words Nnef GCSession Create Response) as described under detailed examples of operations. The AF  322  uses the UPF  304  (or NEF  314 ) information to send GC data towards the UEs  202  may be used to send the GC Session establishment response message  560 . The AF  322  may subscribe explicitly or implicitly to the event exposure service of NEF  314  for notifications related to the GC Session. The AF  322  may provide the NEF  314  with one or more of following information; AF Transaction ID, External Group ID, GC Session ID, TMGI, the set of Event IDs, e.g. GC Session Status, which indicates whether UEs  202  have received GC Session announcement as well as the reason (cause) if UE  102  has not received GC Session announcement. The NEF  314  may subscribe to event exposure service of SMF  310  related to the GC Session. NEF  314  may provide Internal Group ID, the set of Event IDs, e.g. GC Session Status, which indicates whether UEs  202  have received GC Session announcement and the reason (cause) if UE  202  has not received GC Session announcement. 
     Note that the GC Session announcement procedure is described in a separate procedure later. This procedure could be performed a time, for example after the SMF  310  received the message  506 , or after the SMF  310  received message  540 . 
     An alternative method in steps  13 ,  14   a,    14   b,  and  15 , for SMF  310  to configure SM Session Context in (R)AN node  302  is as follows. Step  13 : The SMF  310  sends an N11 GC Session Establishment Request message to the AMF- 2   350 . The N11 GC Session Establishment Request message may contain similar information that are described in step  13 , for example the list of (R)AN Addresses, QoS information, UPF information (e.g. Address of UPF, and UL TEID for each (R)AN node), DL TEID of GC Session, UE Group ID (e.g. Internal-Group ID, and/or TMGI), UE information (such as UE IDs, like SUPI or GPSI), GC Session ID which could be represented by TMGI, Network Slice Information (e.g. S-NSSAI). Step  14   a:  The AMF- 2   350  may discover the locations of UEs  202 , such as the serving (R)AN information, such as (R)AN IDs, or (R)AN addresses. Step  14   b:  The AMF- 2   350  may create an N2 control channel between the AMF- 2   350  and each (R)AN node  302  that is included in step  13  to exchange control signal for the UE Group ID, and/or for GC Session ID. The AMF- 2   350  may create multiple N2 MM GC Session Establishment Request messages, each of N2 MM GC Session Establishment is sent to one (R)AN node  302 . The N2 MM GC Session establishment request messages may include any combination of the information received in Step  13 . Step  14   c:  If it is a Guaranteed Bit Rate (GBR) resource type, the (R)AN may reserve radio resources for the GC Session according to the QoS Profile of GC Session. Step  15 : Each of (R)AN nodes  302  then may send an N2 MM GC Session establishment response message to the AMF- 2   350 . The GC 
     Session establishment response message may include DL TEID in case the (R)AN  702  is in charge of assigning DL TED. If the (R)AN  702  assigned a multicast data radio bearer or a broadcast radio bearer for the GC Sessions, the DL TED may be the TEID of one DL tunnel. Otherwise, the (R)AN  702  may assign multiple DL TEID, each DL TED for one N3 interface for one UE so that the UPF may send use multiple unicast transmissions for GC Session. The AMF- 2   350  may collect all the N2 MM GC Session establishment response message, and may forward GC Session information received in step  14   b to the MSF  310 .    
       FIG. 5  illustrates an embodiment of an AMF- 1   308  GC session announcement. The following are the steps of  FIG. 5 . The steps described are for the architecture illustrated in  FIG. 2 . 
     AMF- 1   308  is the AMF that serves unicast PDU Session(s) of UEs  202 . Either step  21  or  22  may be used for SMF  310  to discover AMF- 1   308 . There can be multiple AMF- 1 s  308 , each AMF- 1   308  may serve one or multiple UE  202 s that are targeted to receive group communication data. 
     Step  21   a:  The SMF  310  may discover AMF- 1   308  by sending a request, for example Discover AMF- 1  Request message  605 , to UDM  320 . For example, the SMF  310  may use the UDM service Nudm_UECM Get. SMF  310  may provide any combination of following information to UDM  320 : UE information (such as UE ID (e.g. SUPI), Internal Group ID, TMGI), and NF type (is AMF function type), and Access Type (e.g. 5G (R)AN, WiFi, 3GPP, non-3GPP). 
     Step  21   b:  The UDM  320  may send a Discovery AMF- 1  Response message  610  to SMF  310  to provide the AMF ID or AMF Address, or AMF FQDN. UDM  320  may use Nudm_UECM Get response service to send Discovery AMF- 1  Response message  610 . 
     Step  22   a:  The SMF  310  discovers AMF- 1   308  by sending a request, for example Discover AMF- 1  Request message  615 , to the PCF  316 . The SMF  310  may provide one or more of following to PCF  316 : UE information (such as UE ID (e.g. SUPI, GPSI, TMSI), Internal Group ID, TMGI), and NF type (is AMF function type), and Access Type (e.g. 5G (R)AN, WiFi, 3GPP, non-3GPP). 
     Step  22   b:  The PCF  316  may send a Discovery AMF- 1  Response message  620  to SMF  310  to provide the AMF ID or AMF Address, or AMF FQDN. 
     Step  23   a:  The SMF  310  may send GC Session Announcement Request message  625  to AMF- 1   308 . In some embodiments, the SMF  310  may use service Namf_Communication_N1N2 Message Transfer and modified as discussed under detailed examples of operations below to send the GC Session Announcement Request message  625  to AMF- 1   308 . The GC Session Announcement Request message  625  may include any combinations of the following information:
         GC Session Information:   GC Session ID: The GC Session Identifier that created by the SMF  310  in step  4 . The GC Session ID may be also a TMGI created by the SMF  310  in step  4 , or by the UDM  320  sent to the SMF  310  in message  514 .   TMGI   ARP: paging priority   Internal Group ID: The internal group ID of UE  104 s that may receive the GC data.   GC service area (or GC location information): The area of GC Session, may be indicated by the list of (R)AN nodes IDs (or (R)AN IP Address, or (R)AN FQDNs) and list of cell IDs of each (R)AN node  302 , tracking area ID, Registration area ID, service area of SMF  310 , geographic zone ID(s). If UE  202  is currently outside the Group communication service area, the AMF- 1   308  may not need to send the GC Session Announcement message to UE  202 .   N1 SM message: The N1 SM message to be sent to UE  202 . N1 SM message in a Message Container to the UE  202  via AMF- 1   308 .       

     The N1 SM message may contain any combination of the following information:
         GC Session ID   TMGI   Time to start GC Session   Amount of data UE  202  may expect to receive   Security information: The group communication data may be protected by some measures, such as encryption at the data source. AF  322  may send the security information (e.g. including decryption key(s)) to NEF  314  in step  1  of  FIG. 4A ; The AF  322  may send security information of GC Session to the NEF  314 . The NEF  314  may forward the security information to SMF  310  in step  3  of  FIG. 4A .   QoS Information: may include QoS Rule; or some QoS parameters of the QoS Rule for each data flow and/or QoS Rule for GC Session, such as Maximum Bit Rate in the downlink, Resource Type (e.g. GBR, non-GBR, delay critical GBR), Guaranteed Flow Bit Rate (GFBR), Maximum Flow Bit Rate (MFBR), GC Session-Aggregate Maximum Bit Rate (Session-AMBR).   A data container that transparently carries an AF-to-UE message sent from the AF  322  to the UEs  202 .       

     The SMF  310  may subscribe to Event Exposure service of the AMF- 1   308  to receive UE  202  Reachability Status notification. SMF  310  receives this UE  202  reachability information by sending a Namf_EventExposure_Subscribe message to the AMF- 1   308  in step  3 . Alternatively, the SMF  310  may be implicitly subscribed to receive to receive UE Reachability Status notification over the Event Exposure service of the AMF- 1   308 . 
     Step  23   b:  The AMF- 1   308  may send GC Session Announcement Response message  630  to the SMF  310  to acknowledge reception of message from SMF  310  in step  3   a  described above. AMF- 1   308  may use Namf_Communication_N1N2 Message Transfer response service to transfer the GC Session Announcement Response message  630  to the MSF  310 . Namf_Communication_N1N2 Message Transfer response service is discussed under detailed examples of operations below. AMF- 1   308  may store the information receive from SMF  310  in the UE Context such as GC Session ID, an GC Session indication for GC Session ID, Internal Group ID, Group communication service area. 
     Step  24 : the AMF- 1   308  interacts  635  with (R)AN node  302  to send GC Session Announcement to UE  202 .
         If the UE  202  is in CM-CONNECTED state in the access associated with the GC Session, the AMF- 1   308  sends the N1 SM message to the UE  202 .   If the UE  202  is in CM-IDLE state in 3GPP access, the AMF- 1   308  may decide to notify the UE  305  through 3GPP (R)AN even when the UE  202  is in CM-CONNECTED state for non-3GPP access, the AMF- 1   308  may send a Paging message to (R)AN node(s)  302  via 3GPP access.   If the UE  202  is simultaneously registered over 3GPP and non-3GPP accesses in the same PLMN, the UE  202  is in CM-IDLE state in both 3GPP access and non-3GPP access, the AMF- 1   308  sends a Paging message with associated access “non-3GPP” to NG-RAN node(s) via 3GPP access.   If the UE  202  is in RM-REGISTERED state and CM-IDLE and reachable in 3GPP access, the AMF- 1   308  sends a Paging message (NAS ID for paging, Registration Area list, Paging DRX length, Paging Priority indication, access associated to the GC Session) to (R)AN node(s)  302  belonging to the Registration Area(s) in which the UE  202  is registered, then the (R)AN node  302  pages the UE  202 .   If the UE  202  is in CM-CONNECTED and RRC-inactive state, the paging strategies may be configured in the (R)AN node  302  for different combinations of Paging Policy Indication, ARP and 5 QI.       

     If the UE  202  is simultaneously registered over 3GPP and non-3GPP accesses in the same PLMN, and the UE  202  is in CM-CONNECTED state in 3GPP access and the GC Session is associated with non-3GPP access, the AMF- 1   308  sends a NAS Notification message containing the non-3GPP Access Type to the UE  202  over 3GPP access and sets a Notification timer. Step  5  is omitted. 
     If the UE  202  is simultaneously registered over 3GPP and non-3GPP accesses in the same PLMN, and the UE  202  is in CM-CONNECTED state for non-3GPP access and in CM-IDLE for 3GPP access, and if the GC Session is associated with 3GPP access network, and based on local policy the AMF- 1   308  decides to notify the UE  202  through non-3GPP access, the AMF- 1   308  may send the N1 SM message to the UE  202  over non-3GPP access network. 
     The (R)AN node  302  may send a message over a radio resource control (RRC) channel to inform UEs  202  of the radio resource parameters to be used for the GC Session. The radio resource parameters may include any combination of the following: data radio bearer (DRB) information, security key(s) to decrypt the data encrypted by the (R)AN node, information to identify the GC Session (e.g. TMGI, GC Session ID). 
     Step  25 : The AMF- 1   308  may send a GC Session Announcement Notify message  640  to SMF  310  to inform SMF  310  whether the GC Session Announcement has been successfully delivered to UE  202  or not. In some embodiments, the AMF service Namf_EventExposure_Notify is modified as discussed under detailed examples of operations below may be used to send the GC Session Announcement Notify message  640 . The AMF- 1   308  may also notify whether the UE  202  is outside GC Session service area. 
     Step  26   a:  The SMF  310  may collect all notification messages from one or more AMF- 1 s  308  for all UE  202 s that are targeted to receive group communication data. The SMF  310  may send a GC Session Status Notification message  645  towards AF  322 , via NEF  314 . In some embodiments, the SMF  310  may collect all notification messages from one or more AMF- 1 s  308  for all UE  202 s that are targeted to receive group communication data using Nsmf_EventExposure_Notify service of the MSF  310 . The SMF  310  may include the list of UE IDs (such as GPSI, External UE IDs, SUCI, 5G GUTI, SUPI) that may join or may not join the GC Session and the reason (or cause) and also the Internal Group ID and/or TMGI. The reason could be UE  202  is outside of the region that has the GC Session, UE  202  is not reachable, UE  202  is de-registered, UE  202  ID is not valid. 
     Step  26   b:  The NEF  314  may forward the GC Session Status Notification message  645  receive from the SMF  310  in step  26 a to AF  322 . NEF  314  may use the Nnef_EventExposure_Notify service and modified as discussed under detailed examples of operations below to deliver the GC Session Status Notification  650  to AF  322 . NEF  314  may replace some types of UE  202  ID, for example SUCI, 5G GUTI, SUPI to GPSI. NEF  314  may replace Internal Group ID with External Group ID. 
     An alternative to Step  21  is wherein the SMF  310  may discover AMF- 1   308  in step  22 . 
       FIG. 6  illustrates an embodiment of the GC session announcement. The following are the steps of  FIG. 6 . 
     Stage  1 : The CN establishes a GC Session in the CN and (R)AN as described with respect to  FIG. 4A  and  FIG. 4B  above. In this stage, the SMF  310  does not require message exchanges with AMF- 1   308 . The AF  322  may subscribe to event exposure service of the NEF  314  for notifications related to the GC Session. The AF  322  may provide External Group ID, the set of Event IDs, e.g. GC Session Status, which indicates whether UEs  202  have received GC Session announcement and reason (cause) if the UEs  202  have not received GC Session announcement. The NEF  314  may subscribe to event exposure service of the MSF  310 , related to the GC Session. The SMF  310  may provide Internal Group ID, the set of Event IDs, e.g. GC Session Status, which indicates whether UEs  202  have received GC Session announcement and reason (cause) if the UEs  202  have not received GC Session announcement. 
     In  FIG. 4A , during GC Session Establishment Request  532 , if the SMF  310  does not provide the list of (R)AN Address(es), the AMF- 2   350  may discover the location of UE  202 , such as the serving (R)AN node  302  information, such as (R)AN IDs, or (R)AN addresses by first discovering the serving AMF- 1   308 , which uses the same method described above with respect to  FIG. 5  (e.g. the SMF  310  sends a Discover AMF- 1  Request message  605  to the UDM  320  and receives a Discover AMF- 1  Response message  610  from the UDM  320 , or the SMF  310  sends a Discover AMF- 1  Request message  615  to the PCF  316  and receives a Discover AMF- 1  Response message  620  from the PCF  316  as shown in FIG. 5 ). After discovering AMF- 1   308 , the AMF- 2   350  may send a message, such as UE  202  serving RAN information request to the AMF- 1   308 . The AMF- 2   350  may provide one or more of following to AMF- 1   308 : Internal Group ID, TMGI, UE ID (such as SUPI, GPSI, TMSI). 
     The AMF- 1   308  may send a message, such as UE  202  serving RAN information response to the AMF- 2   350 , to inform the AMF- 2   350  of the serving (R)AN node&#39;s  302  information.
         If the AMF- 2   350  provided the Internal Group ID, the AMF- 1   308  searches UE Context of UEs  202  having the Internal Group ID for (R)AN Address (such as (R)AN ID, or (R)AN IP Address, or (R)AN FQDN). The AMF- 1   308  sends the list of (R)AN Address(es) that are serving UEs of Internal Group ID to the AMF- 2   350 . The list of (R)AN address(es) may include an indication to show which (R)AN node is serving which UEs.   If the AMF- 2   350  provided the list of UE ID, AMF- 1   308  searches UE Context of UEs  202  to find the serving (R)AN Address. The AMF- 1   308  sends the list of (R)AN Address(es) that are serving UEs  202  to the AMF- 2 . The list of (R)AN address(es) may include an indication to show which (R)AN node is serving which UEs.       

     UE  202  serving RAN information request and response may be implemented using AMF service Namf Location ProvidePositioninglnfo with modifications discussed under detailed examples of operations below. If UE  202  is in RRC-Inactive state, the AMF- 1   308  may send a message to (R)AN node  302  to find the current serving (R)AN node  302  of UE  202 . 
     In GC Session Announcement stage, the GC Session announcement Request  625  is sent from the SMF  310  to the AMF- 2   350 . 
     Step  1   a:  The AMF- 2   350  was selected in Stage  1  to establish GC Session. If the AMF- 2   350  did not discover AMF- 1   308  in Stage  1 , the AMF- 2   350  discovers the AMF- 1   308  by sending a request, for example Discover AMF- 1  Request message  605 , to the UDM  320 . For example, the AMF- 2   350  may use Nudm_UECM_Get service of the UDM  320 . The AMF- 2   350  may provide one or more of following information: Internal Group ID, UE ID(s) of UE(s)  202  in the UE group, (e.g. SUPI, or GPSI) and NF type (is AMF function type), and Access Type (e.g. 5G (R)AN, WiFi, 3GPP, non-3GPP) to the UDM. 
     Step  1   b:  The UDM  320  sends Discovery AMF- 1  Response message  610  to the AMF- 2   350  to inform the UDM  320  of the AMF ID or AMF Address of AMF- 1 . The UDM  320  may use Nudm_UECM_Get response service to send Discovery AMF- 1  Response message  610 . 
     Alternative to Steps  1   a  and  1   b,  the AMF- 2   350  may discover AMF- 1   308  in steps  2   a,  and  2   b.    
     Step  2   a:  One AMF- 2   350  was selected in Stage  1  to establish GC Session. The AMF- 2   350  discovers the AMF- 1   308  by sending a request, for example Discover AMF- 1  Request message  615 , to the PCF  320 . The AMF- 2   350  may provide any combination of following information: Internal Group ID, UE ID(s) of UE group (e.g. SUPI, or GPSI) and NF type (is AMF function type), and Access Type (e.g. 5G (R)AN, WiFi, 3GPP, non-3GPP) to the PCF. 
     Step  2   b:  The PCF  316  may send Discovery AMF- 1  Response message  620  to the AMF- 2   350  to inform the AMF ID or AMF Address of AMF- 1   308 . 
     Steps  1   a,    1   b  or steps  2   b,    2   b  are shown in  FIG. 6  being perform before step  3 , however, in alternative embodiments, steps  1   a,    1   b  or steps  2   b,    2   b  may be performed after step  3 . 
     Step  3 : The SMF  310  may send GC Session announcement request message  625  to the AMF- 2   350 . In some embodiments, the SMF  310  may send a GC Session Announcement request using Namf_Communication_N1N2MessageTransfer request service of the AMF- 1   308  and modified using detailed examples of operations discussed. The GC Session announcement request message  625  may include any combinations of the following information as described in message  625  of step  23  of  FIG. 5  above: 
     The SMF  310  may subscribe to Event Exposure service of the AMF- 2   350  by sending Namf_EventExposure_Subscribe message to the AMF- 2   350  in step  3  to receive UE Reachability Status notification. Alternatively, the SMF  310  may be implicitly subscribed to receive Event Exposure service of the AMF- 2   350  to receive UE Reachability Status notification. The AMF- 2   350  may store the information received from SMF  310  in the UE Context such as GC Session ID, an GC Session indication for GC Session ID, Internal Group ID, TMGI, Group communication service area (or GC location information). 
     Step  4   a:  The AMF- 2   350  may send a GC session announcement request message  630  that includes the GC session announcement request message  625  received from the SMF  310  to AMF- 1   308 . In some embodiments, there can be multiple AMF- 1 s  308 , the AMF- 2   350  sends to each AMF- 1   308  the GC Session announcement request message  625  received from the SMF  310 . The GC session announcement request message  630  may include GC Session information and the N1 SM message. In some embodiments, AMF- 2   350  use a Namf_Communication_N1N2MessageTransfer request service of the AMF- 1   308  to deliver a GC Session announcement request message  630 . The AMF- 2   350  may not modify the message received from the MSF  310 , just forwards the message receives from the SMF  310  to the AMF- 1   308 . The AMF- 2   350  may also include the SMF ID of the SMF  310  and/or the AMF ID of the AMF- 2   350  when sending the message received from the SMF  310  to the AMF- 1   308 . Later, the AMF- 1   308  may use the provided AMF ID of the AMF- 2   350  or SMF ID of the SMF  310  to send notification message related to the GC Session to the SMF  310  and/or the AMF- 2   350 . The AMF- 2   350  may store the GC Session information received from SMF  310  in the UE Context, and/or UE Group Context, and/or GC Session context, such as GC Session ID, a GC Session indication for GC Session ID, Internal Group ID, TMGI, Group communication service area. The AMF- 2   350  may subscribe, on behalf of the SMF, to the notification service of the AMF- 1   308  related to the GC Session. In this way, the SMF  310  may receive notification messages from the AMF- 1  directly. 
     Step  4   b:  The AMF- 1   308  may send GC PDU Session Announcement Response message  635  to the AMF- 2   350  to acknowledge the reception of the GC PDU session announcement request message  630  from the AMF- 2   350  in step  4   a.  The AMF- 1   308  may use Namf_Communication_N1N2MessageTransfer response service to transfer the GC Session Announcement Response message  630  to the AMF- 2   350 . The AMF- 1   308  may store the GC Session information received from the AMF- 2   350  in the UE Context, and/or UE Group Context, and/or GC Session context, such as GC Session ID, a GC Session indication for GC Session ID, Internal Group ID, TMGI, Group communication service area. 
     Step  5 : The AMF- 2   350  may send GC Session Announcement Response message  640  to the SMF  310  to acknowledge the reception of the GC Session announcement request message  625  from the SMF  310  in step  3 . The AMF- 2   350  may use Namf_Communication_N1N2MessageTransfer response service to transfer the GC Session Announcement Response message  640  to the MSF  310 . 
     Step  6 : The AMF- 1   308  is configured to interact  645  with (R)AN node  302  to send GC Session Announcement to the UE  202 . For example, this step is the same as step  24  of  FIG. 5 , the AMF- 1   308  interacts with (R)AN node  302  to send GC Session Announcement to UE  635  of  FIG. 5 . 
     Step  7   a:  The AMF- 1   308  may send a message, such as a GC Session Announcement Notification message  650  towards the SMF  310  either directly or via the AMF- 2   350  to inform the SMF  310  whether the GC Session Announcement has been successfully delivered to the UE  202  or not. In some embodiments, the AMF- 1   308  can inform the SMF  310  whether the GC Session Announcement has been successfully delivered to the UE  202  or not by using Namf_EventExposure_Notify service of the AMF- 1   308  or by using Namf_Communication_N1_MessageNotify service of the AMF- 1   308 . The AMF- 1   308  may also notify whether the UE is outside Group communication service area, and/or error (for example UE not reachable, UE deregistered, UE in extended Discontinuous Reception (eDRX) mode, UE in power saving mode). 
     Step  7   b:  The AMF- 2   350  may forward the GC Session Announcement Notify message  655  received from the AMF- 1   308  to the SMF  310  to inform SMF  310  whether the GC Session Announcement has been successfully delivered to the UE  202  or not. In some embodiments, the AMF- 2   350  may inform SMF  310  whether the GC Session Announcement has been successfully delivered to the UE  202  or not using Namf_EventExposure_Notify service of the AMF- 2   350 . The AMF- 1   308  may also notify whether the UE  202  is outside Group communication service area. 
     Alternative to step  7   a  and  7   b,  the AMF- 1   308  may send GC Session Announcement Notification message  665  to the SMF  310  directly if the SMF ID of the SMF  310  is provided by the AMF- 2   350  in step  4   a,  or the SMF  310  was subscribed to receive the notification related to the GC Session in step  4   a.    
     In step  7   b,  the AMF- 2   350  may forward individual messages received from AMF- 1   308  to the MSF  310 . In another embodiment, the AMF- 2   350  may wait to collect all the notification messages from all the AMF- 1   308 . The AMF- 2   350  may forward all the notification messages from the AMF- 1  to the SMF. In another embodiment, the AMF- 2   350  may extract the information from the AMF- 1 (s)  308  and make an GC Session Announcement Notification message that include the extracted information received from the AMF- 1   308  and sends to the MSF  310 . 
     The GC Session Announcement Notification message  665  may include any combination of following information. The list of UE IDs (e.g. SUPI, GPSI, 5G GUTI) which have received GC Session announcement message. As well, the list of UE IDs (e.g. SUPI, GPSI, 5G GUTI) which have not received GC Session announcement message; For each UE that has not received GC Session announcement message, a cause code is included. The cause code indicates the reason the UE has not received the GC Session announcement message, such as UE is unreachable, UE is outside Group communication service area, UE in extended Discontinuous Reception (eDRX) mode, UE in power saving mode. 
     Step  8   a:  The SMF  310  may collect all notification messages from one or multiple AMF- 1   308  via the AMF- 2   350  for all UEs  202  that are targeted to receive group communication data. The SMF  310  may send a GC Session Status Notification message  660  towards the AF, either directly or via the NEF. In some embodiments, the SMF  310  may use the Nsmf_EventExposure_Notify service of the SMF  310  to collect all notification messages from one or multiple AMF- 1   308  via the AMF- 2   350  for all UEs  202  that are targeted to receive group communication data. The SMF  310  may include the list of UE IDs (such as GPSI, External UE IDs, SUCI, 5G GUTI, SUPI) that may not join the GC Session and the reason (or cause) for corresponding UE that has not joint the GC Session, Internal Group ID, AF Transaction ID, TMGI. The reason could be UE  202  is outside of region that has GC Session, the UE  202  is not reachable, the UE  202  is de-registered, the UE ID is not valid, UE in extended Discontinuous Reception (eDRX) mode, UE in power saving mode. 
     Step  8   b:  The NEF  314  may forward the GC Session Status notification message  660  receive from the SMF  310  in step  8 a to the AF  322 . The NEF  314  may use the Nnef_EventExposure_Notify service to deliver the GC Session Status Notification to the AF. The NEF  314  may replace some types of UE ID, for example SUCI, 5G GUTI, SUPI to GPSI. The NEF  314  may replace Internal Group ID by External Group ID. 
     In some embodiments, the AF  322  is configured to communicate with the MSF  310 , and the SMF  310  may directly send message  660  to the AF  322 . 
     As stated above, detailed examples of operations will now be discussed, 
     Service operation for the functions, such as AF, to send request for creating the group communication (GC) session will now be discussed using the example name Nnef_GCSession_Create (or also called Nnef_PDUSession_Create). Example inputs can include one or more of following information: a list of UE IDs (e.g. GPSI, SUPI, External UE ID), DNN, S-NSSAI, Protocol Configuration Options, Requested PDU type (GC Session, IP PDU Session, Ethernet PDU Session, Unstructured PDU Session). Optional inputs can include for GC Session: UE Information (UE IDs like GPSI, SUPI, UE Location Information like Geographic Zone ID(s) and/or list of cell IDs), Internal Group ID, or list of UE IDs (e.g. SUPI, or GPSI, or External UE ID), location information of GC Session (e.g. Geographic Zone ID(s)), QoS requirements (value of standardized 5 QI, Maximum data rate of GC session, average data rate of GC session, packet delay budget, expected or maximum data volume in a certain period of time), number of data flows in the GC session, Network Slice Information (e.g. S-NSSAI), Application ID, AF-Service-Identifier, how the group communication data will be sent to the network (over NEF control plane or UPF user plane), Information of AS (e.g. IP version (IPv4 or IPv6), source IP Addresses or IP Prefixes, source UDP or TCP port number, packet flow description (PFD), Type of Service (TOS) (IPv4)/Traffic class (IPv6) and Mask, Flow Label (IPv6), Security parameter index), AN Type, DNN Selection Mode, subscription get notified of PDU Session status change. Example outputs can include result indication, and if success in addition: QFI(s), QoS Profile(s), Session-AMBR, QoS Rule(s), H-CN Tunnel Info, Enable pause of charging indication, Selected PDU type and SSC mode. Further optional outputs can include Cause, Protocol Configuration Options, UE IP address, IPv6 Prefix allocated to the PDU Session, information needed by V-SMF in case of EPS interworking such as the PDN Connection Type, Reflective QoS Timer. Further examples of outputs can include (for Response message for GC Session): Result Indication (e.g. Successful, Reject). Further optional outputs can include (for Response message for GC Session): Cause, Protocol Configuration Options for interface with UPF or NEF (e.g. HTTP), UPF or NEF IP address, UDP port of the UPF or NEF, QoS Rule(s) that may be sent to the UEs in the application layer. 
     Service operation for creating the PDU session or GC Session will now be discussed using the example name Nsmf_PDUSession_Create service operation. Example inputs can include SUPI, V-SMF ID, DNN, S-NSSAI, Protocol Configuration Options, Requested PDU type (Group Communication Session or PDU Session like IP PDU Session, Ethernet PDU Session, Unstructured PDU Session), Requested SSC mode, PDU Session ID, V-CN Tunnel Info, addressing information allowing the H-SMF to request the V-SMF to issue further operations about the PDU Session. AF ID (or AF-Service-ID), Transaction Reference ID(s). Examples of optional inputs can include UE location information, subscription get notified of PDU Session status change, PEI, GPSI, AN type, PCF ID, DNN Selection Mode. Further examples of optional inputs can include for GC Session: UE Information (UE IDs like GPSI, SUPI, UE Location Information like Geographical Zone ID(s)), Internal Group ID, or list of UE IDs (e.g. SUPI, or GPSI, or External UE ID), location information of GC Session (e.g. Geographic Zone ID), QoS requirements (Maximum data rate, average data rate, packet delay budget, expected or maximum data volume in a certain period of time), Network Slice 
     Information (e.g. S-NSSAI), Application ID, how the group communication data will be sent to the network (over NEF control plane or UPF user plane), Information of AS (e.g. IP Addresses or IP Prefixes, UDP or TCP port number, packet flow description (PFD)), AN Type, DNN Selection Mode, subscription get notified of PDU Session status change, AF-to-UE message. Outputs may include one or more of following information NEF ID, AF ID (or AF-Service-ID), Transaction Reference ID(s), Result Indication, and if success in addition: QFI(s), QoS Profile(s), Session-AMBR, QoS Rule(s), H-CN Tunnel Info, Enable pause of charging indication, Selected PDU type and SSC mode. Further examples of outputs may include one or more of following information: Cause, Protocol Configuration Options, TMGI, UE IP address, IPv6 Prefix allocated to the PDU Session, information needed by V-SMF in case of EPS interworking such as the PDN Connection Type, Reflective QoS Timer. Further examples of outputs may include one or more of following information (for Response message for GC Session): NEF ID, AF ID (or AF-Service-ID), Transaction Reference ID(s), Result Indication (e.g. Successful, Reject). Further examples of outputs may include one or more of following information (for Response message for GC Session): Cause, TMGI, Protocol Configuration Options for interface with UPF or NEF (e.g. HTTP), UPF or NEF IP address, UDP port of the UPF or NEF, QoS Rule(s) that may be sent to the UEs in the application layer. Further optional outputs can include (for Response message for GC Session if the NEF is used for interface with AF): UPF information, such as UPF Address(es) and DL TEID for the NEF to send DL packets to the UPF(s). 
     Service operation for creating the Group Communication (GC) session will now be discussed using the example name Nsmf_GCSession_CreateSMContext. Example inputs can include AMF ID (AMF Instance ID), (R)AN Information: (R)AN Address, (R)AN ID, UE information: List of UEs, or Lists of UE IDs (e.g. SUPI, PEI) each correspond to a (R)AN node, Network slice information (e.g. S-NSSAI). Optional inputs can include PEI, UE location information, UE Time Zone, AN type, H-SMF identifier/address, Subscription for PDU Session Status Notification, indication that the SUPI has not been authenticated, PCF ID, DNN Selection Mode, UE PDN Connection Context, GPSI, UE presence in group communication service area, GUAMI(s) (if NF Type is AMF. Further example inputs may include one or more of following information: the UDM ID that is selected by the AMF, the PCF ID that is selected by the AMF, the AMF ID(s) that are currently serving UEs. Example outputs may include one or more of following information Result Indication, TMGI. Further example outputs include one or more of following information: Cause, GC Session ID, N2 SM information, N1 SM container. When the GC Session is for a UE without USIM, the AMF provides the PEI and not the SUPI as identifier of the UE. When the GC Session is for Emergency services of an unauthenticated UE with an USIM, the AMF shall provide both the SUPI and the PEI and shall provide an indication that the SUPI has not been authenticated. 
     Service operation to get subscriber data by using a service of the UDM function will now be discussed using the example name Nudm SDM Get. Example inputs can include NF ID, Subscription data type(s), Key for each Subscription data type(s). Further example optional inputs can include Data Sub Key(s). Example outputs can include the consumer NF gets the requested subscription data. Subscription data type keys are defined in Table 1, data keys are defined in Table 2, subscription data types are defined in Table 3a-f. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Subscription data types keys 
               
            
           
           
               
               
               
            
               
                 Subscription Data Types 
                 Data Key 
                 Data Sub Key 
               
               
                   
               
               
                 Access and Mobility Subscription data 
                 SUPI 
                 — 
               
               
                 SMF Selection Subscription data 
                 SUPI 
                 — 
               
               
                 UE context in SMF data 
                 SUPI 
                 S-NSSAI 
               
               
                   
                   
                 DNN 
               
               
                 SMS Management Subscription data 
                 SUPI 
                 — 
               
               
                 SMS Subscription data 
                 SUPI 
               
               
                 Session Management Subscription data 
                 SUPI 
                 S-NSSAI 
               
               
                   
                   
                 DNN 
               
               
                 Identifier translation 
                 GPSI 
                 — 
               
               
                 Slice Selection Subscription data 
                 SUPI 
                 — 
               
               
                 GC Session Subscription data 
                 AF-Service-ID 
                 Internal 
               
               
                   
                   
                 Group ID 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Data Keys 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Data Sub 
               
               
                 Data Set 
                 Data Subset 
                 Data Key 
                 Key 
               
               
                   
               
               
                 Subscription 
                 Access and Mobility 
                 SUPI 
                 — 
               
               
                 Data 
                 Subscription data 
               
               
                   
                 SMF Selection Subscription data 
                 SUPI 
                 — 
               
               
                   
                 UE context in SMF data 
                 SUPI 
                 S-NSSAI 
               
               
                   
                   
                   
                 DNN 
               
               
                   
                 SMS Management Subscription 
                 SUPI 
                 — 
               
               
                   
                 data 
               
               
                   
                 SMS Subscription data 
                 SUPI 
               
               
                   
                 Session Management 
                 SUPI 
                 S-NSSAI 
               
               
                   
                 Subscription data 
                   
                 DNN 
               
               
                   
                 Slice Selection Subscription data 
                 SUPI 
                 — 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3a 
               
             
            
               
                   
               
               
                 Subscription data types 
               
            
           
           
               
               
               
            
               
                 Subscription data type 
                 Field 
                 Description 
               
               
                   
               
               
                 Access and Mobility 
                 SUPI 
                 Key 
               
               
                 Subscription data (data needed 
                 GPSI List 
                 List of the GPSI (Generic 
               
               
                 for UE Registration and 
                   
                 Public Subscription Identifier) 
               
               
                 Mobility Management) 
                   
                 used both inside and outside 
               
               
                   
                   
                 of the 3GPP system to address 
               
               
                   
                   
                 a 3GPP subscription. 
               
               
                   
                 Internal Group ID-list 
                 List of the subscribed internal 
               
               
                   
                   
                 group(s) that the UE belongs 
               
               
                   
                   
                 to. 
               
               
                   
                 Subscribed-UE-AMBR 
                 The Maximum Aggregated 
               
               
                   
                   
                 uplink and downlink MBRs to 
               
               
                   
                   
                 be shared across all Non-GBR 
               
               
                   
                   
                 QoS Flows according to the 
               
               
                   
                   
                 subscription of the user. 
               
               
                   
                 Subscribed S-NSSAIs 
                 The Network Slices that the 
               
               
                   
                   
                 UE subscribes to. 
               
               
                   
                 Default S-NSSAIs 
                 The Subscribed S-NSSAIs 
               
               
                   
                   
                 marked as default S-NSSAI. 
               
               
                   
                 UE Usage Type 
               
               
                   
                 RAT restriction 
                 3GPP Radio Access 
               
               
                   
                   
                 Technology(ies) not allowed 
               
               
                   
                   
                 the UE to access. 
               
               
                   
                 Forbidden area 
                 Defines areas in which the UE 
               
               
                   
                   
                 is not permitted to initiate any 
               
               
                   
                   
                 communication with the 
               
               
                   
                   
                 network. 
               
               
                   
                 Service Area Restriction 
                 Indicates Allowed areas in 
               
               
                   
                   
                 which the UE is permitted to 
               
               
                   
                   
                 initiate communication with 
               
               
                   
                   
                 the network, and Non-allowed 
               
               
                   
                   
                 areas in which the UE and the 
               
               
                   
                   
                 network are not allowed to 
               
               
                   
                   
                 initiate Service Request or SM 
               
               
                   
                   
                 signalling to obtain user 
               
               
                   
                   
                 services. 
               
               
                   
                 Core Network type restriction 
                 Defines whether UE is 
               
               
                   
                   
                 allowed to connect to 5GC for 
               
               
                   
                   
                 this PLMN. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3b 
               
             
            
               
                   
               
               
                 Subscription data types continued 
               
            
           
           
               
               
               
            
               
                 Subscription data type 
                 Field 
                 Description 
               
               
                   
               
               
                 Access and Mobility 
                 RFSP Index 
                 An index to specific RRM 
               
               
                 Subscription data (data needed 
                   
                 configuration in the NG-RAN. 
               
               
                 for UE Registration and 
                 Subscribed Periodic 
                 Indicates a subscribed 
               
               
                 Mobility Management) 
                 Registration Timer 
                 Periodic Registration Timer 
               
               
                 (continued) 
                   
                 value. 
               
               
                   
                 Priority Services 
                 Indicates the user is 
               
               
                   
                   
                 subscribed to priority.service 
               
               
                   
                   
                 (MPS). 
               
               
                 Slice Selection Subscription 
                 SUPI 
                 Key 
               
               
                 data ( 
                 Subscribed S-NSSAIs 
                 The Network Slices that the 
               
               
                   
                   
                 UE subscribes to. In roaming 
               
               
                   
                   
                 case, it indicates the 
               
               
                   
                   
                 subscribed network slices 
               
               
                   
                   
                 applicable to the serving 
               
               
                   
                   
                 PLMN. 
               
               
                 UE context in AMF data 
                 SUPI 
                 Key 
               
               
                   
                 AMF 
                 Allocated AMF for the 
               
               
                   
                   
                 registered UE. Include AMF 
               
               
                   
                   
                 address and AMF NF Id. 
               
               
                   
                 Access Type 
                 3GPP or non-3GPP access 
               
               
                   
                   
                 through this AMF 
               
               
                 SMF Selection Subscription 
                 SUPI 
                 Key 
               
               
                 data 
                 Subscribed DNN list 
                 List of the subscribed DNNs 
               
               
                   
                   
                 for the UE. 
               
               
                   
                 Default DNN 
                 The default DNN if the UE 
               
               
                   
                   
                 SMF Selection Subscription 
               
               
                   
                   
                 does not provide a valid DNN. 
               
               
                   
                 LBO Roaming Information 
                 Indicates whether LBO 
               
               
                   
                   
                 roaming is allowed per DNN, 
               
               
                   
                   
                 or per (S-NSSAI, subscribed 
               
               
                   
                   
                 DNN) 
               
               
                 UE context in SMF data 
                 SUPI 
                 Key 
               
               
                   
                 PDU Session Id(s) 
                 List of PDU Session Id(s) for 
               
               
                   
                   
                 the UE 
               
            
           
           
               
               
            
               
                   
                 For each PDU Session Id: 
               
            
           
           
               
               
               
            
               
                   
                 DNN 
                 DNN for the PDU Session. 
               
               
                   
                 SMF 
                 Allocated SMF for the PDU 
               
               
                   
                   
                 Session. Includes SMF IP 
               
               
                   
                   
                 Address and SMF NF Id. 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3c 
               
             
            
               
                   
               
               
                 Subscription data types continued 
               
            
           
           
               
               
               
            
               
                 Subscription data type 
                 Field 
                 Description 
               
               
                   
               
               
                 SMS Management 
                 SUPI 
                 Key 
               
               
                 Subscription data (data needed 
                 SMS parameters 
                 Indicates SMS parameters 
               
               
                 by SMSF for SMSF 
                   
                 subscribed for SMS service 
               
               
                 Registration) 
                   
                 such as SMS teleservice, SMS 
               
               
                   
                   
                 barring list 
               
               
                 SMS Subscription data 
                 SUPI 
                 Key 
               
               
                 (data needed in AMF) 
                 SMS Supported 
                 Indicates whether the UE 
               
               
                   
                   
                 supports SMS delivery over 
               
               
                   
                   
                 NAS over 3GPP access, or 
               
               
                   
                   
                 over non-3GPP access, or over 
               
               
                   
                   
                 both the 3GPP and non-3GPP 
               
               
                   
                   
                 access. 
               
               
                   
                 SMSF address 
                 Indicates SMSF address 
               
               
                   
                   
                 subscribed for SMS service. 
               
               
                 Session Management 
                 SUPI 
                 Key 
               
            
           
           
               
               
            
               
                 Subscription data (data needed 
                 Session Management Subscription data contains one or 
               
               
                 for PDU Session 
                 more S-NSSAI level subscription data: 
               
            
           
           
               
               
               
            
               
                 Establishment) 
                 S-NSSAI 
                 Indicates the value of the S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 Subscribed DNN list 
                 List of the subscribed DNNs 
               
               
                   
                   
                 for the S-NSSAI. 
               
            
           
           
               
               
            
               
                   
                 For each DNN in S-NSSAI level subscription data: 
               
            
           
           
               
               
               
            
               
                   
                 UE Address 
                 Indicates the subscribed static 
               
               
                   
                   
                 IP address(es) for the IPv4 or 
               
               
                   
                   
                 IPv6 or IPv4v6 type PDU 
               
               
                   
                   
                 Sessions accessing the DNN, 
               
               
                   
                   
                 S-NSSAI. 
               
               
                   
                 Allowed PDU Session Types 
                 Indicates the allowed PDU 
               
               
                   
                   
                 Session Types (IPv4, IPv6, 
               
               
                   
                   
                 IPv4v6, Ethernet, and 
               
               
                   
                   
                 Unstructured) for the DNN, S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 Default PDU Session Type 
                 Indicates the default PDU 
               
               
                   
                   
                 Session Type for the DNN, S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 Allowed SSC modes 
                 Indicates the allowed SSC 
               
               
                   
                   
                 modes for the DNN, S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 Default SSC mode 
                 Indicate the default SSC mode 
               
               
                   
                   
                 for the DNN, S-NSSAI. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3d 
               
             
            
               
                   
               
               
                 Subscription data types continued 
               
            
           
           
               
               
               
            
               
                 Subscription data type 
                 Field 
                 Description 
               
               
                   
               
               
                 Session Management 
                 5GS Subscribed QoS profile 
                 The QoS Flow level QoS 
               
               
                 Subscription data (data needed 
                   
                 parameter values (5QI and 
               
               
                 for PDU Session 
                   
                 ARP) for the DNN, S-NSSAI. 
               
               
                 Establishment) (continued) 
                 Charging Characteristics 
                 It may contain information on 
               
               
                   
                   
                 how to contact the Charging 
               
               
                   
                   
                 Function. This information, 
               
               
                   
                   
                 when provided shall override 
               
               
                   
                   
                 any corresponding predefined 
               
               
                   
                   
                 information at the SMF 
               
               
                   
                 Subscribed-Session-AMBR 
                 The maximum aggregated 
               
               
                   
                   
                 uplink and downlink MBRs to 
               
               
                   
                   
                 be shared across all Non-GBR 
               
               
                   
                   
                 QoS Flows in each PDU 
               
               
                   
                   
                 Session, which are established 
               
               
                   
                   
                 for the DNN, S-NSSAI. 
               
               
                   
                 Static IP address/prefix 
                 Indicate the static IP 
               
               
                   
                   
                 address/prefix for the DNN, S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 User Plane Security Policy 
                 Indicates the security policy 
               
               
                   
                   
                 for integrity protection and 
               
               
                   
                   
                 encryption for the user plane. 
               
               
                 GC Session Management 
                 AF-Service-Identifier, or 
                 Key 
               
               
                 Subscription data (data needed 
                 Internal Group Identifier 
               
            
           
           
               
               
            
               
                 for MB Session 
                 Session Management Subscription data contains one or 
               
               
                 Establishment) 
                 more S-NSSAI level subscription data: 
               
            
           
           
               
               
               
            
               
                   
                 S-NSSAI 
                 Indicates the value of the S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 Subscribed DNN list 
                 List of the subscribed DNNs 
               
               
                   
                   
                 for the S-NSSAI. 
               
            
           
           
               
               
            
               
                   
                 For each DNN in S-NSSAI level subscription data: 
               
            
           
           
               
               
               
            
               
                   
                 UE Address 
                 Indicates the subscribed static 
               
               
                   
                   
                 IP address(es) for the IPv4 or 
               
               
                   
                   
                 IPv6 or IPv4v6 type PDU 
               
               
                   
                   
                 Sessions accessing the DNN, 
               
               
                   
                   
                 S-NSSAI. 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3e 
               
             
            
               
                   
               
               
                 Subscription data types continued 
               
            
           
           
               
               
               
            
               
                 Subscription data type 
                 Field 
                 Description 
               
               
                   
               
               
                 GC Session Management 
                 Allowed GC Session Type 
                 Indicates the allowed PDU 
               
               
                 Subscription data (data needed 
                   
                 Session Types (IPv6 GC 
               
               
                 for GC Session Establishment) 
                   
                 Session, IPv4v6 GC Session, 
               
               
                 (continued) 
                   
                 Ethernet GC Session, and 
               
               
                   
                   
                 Unstructured GC Session) for 
               
               
                   
                   
                 the DNN, S-NSSAI. 
               
               
                   
                 Default GC Session Type 
                 Indicates the default PDU 
               
               
                   
                   
                 Session Type for the DNN, S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 5GS Subscribed QoS profile 
                 The QoS Flow level QoS 
               
               
                   
                   
                 parameter values (5QI and 
               
               
                   
                   
                 ARP) for the DNN, S-NSSAI. 
               
               
                   
                 Charging Characteristics 
                 It may contain information on 
               
               
                   
                   
                 how to contact the Charging 
               
               
                   
                   
                 Function. This information, 
               
               
                   
                   
                 when provided shall override 
               
               
                   
                   
                 any corresponding predefined 
               
               
                   
                   
                 information at the SMF 
               
               
                   
                 Subscribed-Session-AMBR 
                 The maximum aggregated 
               
               
                   
                   
                 uplink and downlink MBRs to 
               
               
                   
                   
                 be shared across all Non-GBR 
               
               
                   
                   
                 QoS Flows in each PDU 
               
               
                   
                   
                 Session, which are established 
               
               
                   
                   
                 for the DNN, S-NSSAI. 
               
               
                   
                 Static IP address/prefix 
                 Indicate the static IP 
               
               
                   
                   
                 address/prefix for the DNN, S- 
               
               
                   
                   
                 NSSAI. 
               
               
                   
                 User Plane Security Policy 
                 Indicates the security policy 
               
               
                   
                   
                 for integrity protection and 
               
               
                   
                   
                 encryption for the user plane. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3f 
               
             
            
               
                   
               
               
                 Subscription data types continued 
               
            
           
           
               
               
               
            
               
                 Subscription data type 
                 Field 
                 Description 
               
               
                   
               
               
                 GC Session Management 
                 List of GPSIs 
                 Generic Public Subscription 
               
               
                 Subscription data 
                   
                 Identifier used inside and 
               
               
                 (data needed 
                   
                 outside of the 3GPP system to 
               
               
                 for GC Session 
                   
                 address a 3GPP subscription. 
               
               
                 Establishment) 
                   
                 Used as the Key for 
               
               
                 (continued) 
                   
                 translation to the 
               
               
                   
                   
                 corresponding SUPI (and 
               
               
                   
                   
                 optionally corresponding 
               
               
                   
                   
                 MSISDN). 
               
               
                   
                 List of SUPIs 
                 Corresponding SUPI for input 
               
               
                   
                   
                 GPSI 
               
               
                   
                 GC Session 
                 List of (R)AN ID(s) or List of 
               
               
                   
                 Area 
                 (R)AN IP Addresses 
               
               
                 Identifier 
                 (Optional) 
                 Corresponding GPSI 
               
               
                 translation 
                 MSISDN 
                 (MSISDN) for input GPSI 
               
               
                   
                   
                 (External Identifier). This is 
               
               
                   
                   
                 optionally provided for legacy 
               
               
                   
                   
                 SMS infrastructure not 
               
               
                   
                   
                 supporting MSISDN-less 
               
               
                   
                   
                 SMS. The presence of an 
               
               
                   
                   
                 MSISDN should be 
               
               
                   
                   
                 interpreted as an indication to 
               
               
                   
                   
                 the NEF that MSISDN shall 
               
               
                   
                   
                 be used to identify the UE 
               
               
                   
                   
                 when sending the SMS to the 
               
               
                   
                   
                 SMS-SC over T4. 
               
               
                   
               
            
           
         
       
     
     Service operation for registering UE&#39;s serving function in the UDM function will now be discussed using the example name Nudm_UECM_Registration. Example inputs can include NF ID, SUPI, PEI, NF Type, Internal Group ID, Access Type (if NF Type is AMF, SMSF), PDU Session ID (if NF Type is SMF), UE address (IP or Ethernet address for example) if NF Type is SMF. If NF Type is SMF: DNN or Indication of Emergency Services. Further example inputs can include if NF Type is SMF registering for serving GC Session: GC Session ID, TMGI, AF-Service-Identifier, Internal Group ID, List of UE IDs (such as GPSI, SUPI). Further example inputs can include if NF Type is AMF registering for serving GC Session: GC Session ID, TMGI, AF-Service-Identifier, Internal Group ID, List of UE IDs (such as GPSI, SUPI), GC Session Location(s) that the AMF- 2  serves UEs (e.g. (R)AN ID(s), Registration Area IDs). Example outputs can include Result indication. 
     Service operation for query data from the UDR function will now be discussed using the example name Nudr_DM_Query. Example inputs can include Data Set Identifier, Data Key(s). Optional inputs may include Data Subset Identifier(s), SUPI, Data Sub Key(s) (for each Data Subset), AF-Service-ID, Internal Group ID, TMGI. The SUPI is used to identify which UE the latest list of stored PSIs belongs to. AF-Service-ID, and/or Internal Group ID is/are used to identify data belong to one UE Group. Example outputs can include Requested data. 
     Service operation for creating access and mobility (AM) policy association will now be discussed using the example name Npcf_AMPolicyControl_Create. Example inputs may include one or more of following information SUPI (or PEI in case of emergency PDU Session without SUPI), or AF-Service-Identifier and/or Internal Group Identifier. Other inputs may include one or more of following information provided by the AMF, such as Access Type, Permanent Equipment Identifier, GPSI, User Location Information, UE Time Zone, Serving Network, RAT type, List of subscribed Service Area Restrictions, (V-)PCF ID (if the consumer is AMF, when receiving the PCF ID from old AMF during inter-AMF mobility), H-PCF ID (if the consumer is V-PCF, when receiving the H-PCF ID from AMF), subscribed RFSP Index, UE access selection and PDU session selection policy information including the list of PSIs and Internal Group. The outputs may include one or more of following information: the requested Access and mobility related policy information, UE access selection and PDU Session selection related policy, such as authorized Service Area Restrictions, authorized RFSP Index and URSP, and Policy Control Request Trigger. The AMF requests the PCF to apply operator policies for the UE. The AMF requests the PCF to apply operator policies for the UE; then the PCF acknowledges AMF with requested policy. 
     Service operation for creating session management (SM) SM Policy Association and provide relevant parameters about the PDU session or GC session to the PCF will now be discussed using the example name Npcf_SMPolicyControl_Update. Example inputs can include for PDU Session: PDU Session Id and SUPI (or PEI in case of emergency PDU Session without SUPI). Additional example inputs can include for GC Session, e.g. GC Session Id, Internal Group ID, TMGI. Other example inputs may include one or more information on the Policy Control Request Trigger condition that has been met such as Access Type, (new or removed) IPv4 address and/or IPv6 network prefix, User Location Information, UE Time Zone, Serving Network, RAT type, subscribed Session AMBR, or subscribed default QoS information. Further examples of optional inputs can include for GC Session: (new or removed) IPv4 address and/or IPv6 network prefix assigned to UPF or NEF for communications, e.g. over N6 interface, with the DN or Application Server; GC Session Location Information, Serving Network, RAT type, subscribed GC Session AMBR, or subscribed default QoS information. Example outputs can include success or not. Optional example outputs can include Policy information for the PDU Session. 
     Service operation for subscribing event exposure service of the AMF will now be discussed using the example name Namf_EventExposure_Subscribe. The consumer NF uses this service operation to subscribe to or modify event reporting for one UE, a group of UE(s) or any UE. A function, such as an AMF, may use this service to subscribe Event Exposure service of another AMF on behalf of another function, such as SMF. Example input may include one or more of following information: NF ID, target of the subscription: UE(s) ID (SUPI or Internal Group Identifier or indication that any UE is targeted), ((set of) Event ID(s), Notification Target Address (+Notification Correlation ID))s, Event Reporting Information. The NF ID is the ID of the function that receives the Event Exposure Notification messages. Other input information may be one or more of following input: Event Filter(s) associated with each Event ID, Subscription Correlation ID (in the case of modification of the event subscription). The output may include when the subscription is accepted: Subscription Correlation ID (required for management of this subscription). 
     The first corresponding monitoring event is reported by invoking Namf_EventExposure_Notify, if corresponding information is available. 
     The NF consumer subscribes to the event notification by invoking Namf_EventExposure to the AMF. The AMF allocates a Subscription Correlation ID for the subscription and responds to the consumer NF with the Subscription Correlation ID. UE ID identifies the UE, SUPI and/or GPSI. Event ID identifies the events that the NF consumer is interested in. The Subscription Correlation ID is unique within the AMF Set. 
     The ((set of) Event ID(s), Notification Target Address (+Notification Correlation ID)) helps the Event Receiving NF to co-relate a notification against a corresponding event subscription for the indicated Event ID. 
     In the case that the NF consumer subscribes to the AMF on behalf of other NF, the NF consumer include the Notification Target Address(+Notification Correlation ID) of other NF for the Event ID which is to be notified to other NF directly, and the Notification Target Address(+Notification Correlation ID) of itself for the Subscription Correlation ID change event. Each Notification Target Address (+Notification Correlation ID) is associated with the related (set of) Event ID(s). When the Subscription Correlation ID change due to the AMF reallocation, the notification is sent to NF consumer which triggers this subscription. 
     Event filter may include “AN type(s)” as part of the list of parameter values to match, and it indicates to subscribe the event per Access Type. 
     Event receiving NF ID identifies the NF that shall receive the event reporting. 
     When the consumer NF needs to modify an existing subscription previously created by itself in the AMF, it invokes Namf_EventExposure_Subscribe service operation which contains the Subscription Correlation ID and the new Event Filters with Event ID to the AMF. 
     Namf_EventExposure_UnSubscribe service operation 
     Service operation for unsubscribing event exposure service of the AMF will now be discussed using the example name Namf_EventExposure UnSubscribe. The NF consumer uses this service operation to unsubscribe for a specific event for one UE, group of UE(s), any UE. A function, such as an AMF, may use this service to subscribe Event Exposure service of another AMF on behalf of another function, such as SMF. The input may include Subscription Correlation ID. The output may include Operation execution result indication. 
     The NF consumer unsubscribes the event notification by invoking Namf_EventExposure_Unsubscribe (Subscription Correlation ID) to the AMF. 
     Service operation for using message transfer service of the AMF will now be discussed using the example name Namf_Communication_N1N2MessageTransfer. Example inputs may include one or more of following information: CN NF ID, Message type (N1 or N2 or both), Message Container (s) where at least one of the message containers (N1 or N2) is required. Examples of other inputs may include one or more of following information: last message indication, Session ID, AN Type, Paging Policy Indication, ARP, Group communication service area for the N2 SM information, GC Session Information, 5 QI. Input for GC Session Information:
         GC Session ID;   ARP: paging priority;   Internal Group ID: The internal group ID of UEs that may receive the group communication data;   TMGI of the UE group that may receive the group communication data.; Group communication service area (of group communication location information): The area of GC Session, may be indicated by the list of (R)AN nodes IDs (and each (R)AN node  302  may have a list of Cell IDs that join the GC Session), tracking area ID, Registration area ID, service area of the SMF, geographical zone ID. If the UE is currently outside the Group communication service area, the AMF may not need to send the GC Session Announcement message to the UE.   List of UE IDs (SUPI, 5G GUTI, GPSI) to receive the N1 SM message.   N1 SM message to be sent to the UE. The N1 SM message may contain the following information:
           GC Session ID   Time to start GC Session   Amount of data the UE may expect to receive   QoS Information: may include QoS Rule; or some QoS parameters of the QoS Rule, such as Maximum Bit Rate in the downlink, Resource Type (e.g. GBR, non-GBR, delay critical GBR), Guaranteed Flow Bit Rate (GFBR), Maximum Flow Bit Rate (MFBR), Session-Aggregate Maximum Bit Rate (Session-AMBR).   TMGI   Data container to carry a message, such as AF-to-UE message that sent from the AF to UEs.   
               

     Example outputs may include Result indication. Other outputs include one or more of following information. Redirection information. If the UE is in CM-IDLE state, the AMF initiates the network triggered service request procedure and responds to the consumer NF with a result indication, “attempting to reach UE”. Otherwise, the AMF responds to the consumer NF, with a Namf_Communication_N1N2MessageTransfer response, providing a result indication of whether the AMF was able to successfully transfer the N1 and/or the N2 message towards the UE  202  and/or the AN. A result indication of “N1/N2 transfer success” does not mean that N1 message is successfully received by the UE. It only means that the AMF is able to successfully send the N1 or N2 message towards the AN. The “GC service area for the N2 SM information”, if included is used by the AMF to determine whether the N2 SM information provided by the consumer NF can be used towards the AN based on the current location of the UE. If the location of the UE is outside the “GC service area for the N2 SM information” indicated, the AMF shall not send the N2 SM information to the AN. In case the consumer NF knows that a specific downlink N1 message is the last message to be transferred in this transaction, the consumer NF shall include the last message indication in the Namf_Communication_N1N2MessageTransfer service operation so that the AMF knows that the no more downlink N1 message need to be transferred for this transaction. If the result of the service operation fails, the AMF shall set the corresponding cause value in the result indication which can be used by the NF consumer for further action. In case the related UE is not served by AMF and the AMF knows which AMF is serving the UE, the AMF provides redirection information which can be used by the consumer NF to resend UE related message to the AMF that serves the UE. 
     Service operation to provide the previously subscribed event information to the NF Consumer which has subscribed to that event before will now be discussed using the example name Namf_EventExposure_Notify. Example inputs may include one or more of following information: AMF ID (GUAMI), Notification Correlation Information, Event ID, corresponding UE (SUPI and if available GPSI), TMGI. Other outputs may include one or more of following information: event specific parameter list. When the AMF detects a UE access and mobility event corresponding to a Subscription, it invokes Namf_EventExposure_Notify service operation to the NF consumer(s) which has subscribed to the UE mobility event before. The event is notified towards the consumers for which the Event filters (which may include “AN type(s)”) match. The Notification Target Address (+Notification Correlation ID) indicates to the NF consumer the specific event notification subscription made by the NF consumer. The event specific parameter indicates the type of mobility event and related information, e.g. Registration Area Update/new Registration Area. The event specific parameter list provides the values that matched for generating the event notification. The parameter values to match are specified during the event subscription. For example if the event type reported is “AN change”, the event specific parameter list contains the value of the new AN. For GC Session Events, the AMF may notify the subscribed NF (such as SMF):
         List of UE IDs (e.g. SUPI, GPSI) that are successfully received GC Session Announcement message. For each of UE ID, the AMF may indicate the UE location information.   List of UE IDs (e.g. SUPI, GPSI) that are not successfully received GC Session Announcement message. For each UE, a cause is included, such as UE is unreachable, the UE is de-registered, the UE ID is not valid, the UE is outside GC service area.       

     Service operation for the NEF to report the event to the consumer that has previously subscribed will now be discussed using the example name Nnef_EventExposure_Notify. Example inputs may include one or more of following information Event ID, Notification Correlation Information. For GC Session Events, the AMF may notify the subscribed AF:
         External Group ID, TMGI, List of UE IDs (e.g. GPSI, External UE ID) that have successfully received GC Session Announcement message. For each of UE ID, the NEF may indicate the UE location information.   External Group ID, TMGI, List of UE IDs (e.g. SUPI, GPSI) that have not successfully received GC Session Announcement message. For each UE, a cause is included, such as UE is unreachable, the UE is de-registered, the UE ID is not valid, The UE is outside GC service area.       

     Other inputs may include one or more of following information: event information (defined on a per Event ID basis). Example outputs can include Operation execution result indication. 
     Service operation for the AMF- 1   308  to provide UE positioning information to the consumer NF will now be discussed using the example name Namf_Location_ProvidePositioninglnfo. Example inputs may include one or more of following information: UE Identification (SUPI or PEI, or Internal Group ID, or list of UE Identifications (SUPI, or PEI)), External Client Type, TMGI. Other inputs may include one or more of following information: location QoS, Supported GAD shapes. Example outputs can include Success/Failure indication. Optional outputs can include Geodetic Location, Civic Location, List of Serving (R)AN Address ((R)AN ID or (R)AN IP Address), Position Methods Used, Failure Cause. 
       FIG. 7A  illustrates an embodiment of an GC session establishment in the CN and the (R)AN node  302 . The following are the steps of  FIG. 7A . 
     Step  1 : The AF  322  sends a GC session establishment request message  502  to the NEF  314  in a manner similar to step  1  of  FIG. 4A  described above. 
     Step  2 : The NEF  314  may perform AMF selection  802  by any one or more of the following methods:
         (1) Pre-configured AMF information for GC Sessions in the NEF  314 ;       

     (2) The NEF  314  may request the NRF function to get AMF information by using, for example a service of NEF function, such as Nnrf_NFDiscovery_Request. The NEF  314  may send Network Slice Information (S-NSSAI), DNN, UE Group information (e.g. External Group ID, Internal Group ID), NF type indicating AMF function that can support GC Session management, AF-Service-Identifier, Application Identifier, Application Type (e.g. V2X application, IoT application, Video streaming application, TV broadcasting application) to the NRF for the AMF selection. The NRF  314  returns the AMF Address information (e.g. AMF ID, and/or FQDN, and/or IP Address(es), and/or Endpoint Address(es), and the AMF profile(s)); The AMF profile may contain attributes of the AMF, such as Network Slice Information (S-NSSAI), DNN, UE Group information (e.g. External Group ID, Internal Group ID), NF type indicating AMF function that can support GC Session management, AF-Service-Identifier, Application Identifier, Application Type (e.g. V2X application, IoT application, Video streaming application, TV broadcasting application). Based on the AMF profile(s), the NEF may select an AMF function, which could be an AMF set or an AMF instance of an AMF set.
         (3) The NEF  314  requests the UDM  320  or the UDR  321  to get the GC Session binding information, which provide a mapping between AF-Service-Identifier ID (or External Group ID), and/or network slice information (e.g. S-NSSAI) and/or DNN with AMF ID. The UDM  320  may have information of AMF function or AMF instance(s) that is/are preconfigured to serve GC Sessions of the specific the AF(s)  322 .       

     Step  3 : The NEF  314  may send a GC Session Establishment Request message  805  to the selected AMF- 2   350 , which include the information received from the AF  322 . In case the group communication data will be sent to the NEF  314 , the NEF  314  may include an uplink TEID for the UPF  304  to send the GC Session Establishment Request message  805  to the NEF  314  for acknowledgement of successfully received data or request for retransmission of missing packets. The NEF  314  may map the External Group Identifier to the Internal Group Identifier and send the Internal Group Identifier to the AMF- 2   350 . The NEF  314  may map the Geographic Zone ID to the (R)AN Address or the list of (R)AN Address(es) or (R)AN ID or the list of RAN ID(s), each of (R)AN node may have the Cell ID or list of Cell ID(s) that join the GC Session. 
     Step  4 : The AMF- 2   350  may create a TMGI for the UEs  202  that will receive group communication data. The AMF- 2   350  may perform UDM selection  807  to select a UDM  320  to get the GC Session information. The AMF- 2   350  may use the local information in the AMF- 2   350  to select a UDM  320 . The AMF- 2   350  may access NRF  318  to discover a UDM  320 , by sending Nnrf NFDiscovery Request message. The AMF- 2   350  may provide NRF  318  with one or more of following information for the NRF  318  to select a UDM  320 : AF-Service-Identifier, Application information (e.g. Application ID, type of application (e.g. video multicast or broadcast, voice multicast or broadcast, V2X data multicast or broadcast), UE Group Information (e.g. External Group ID or Internal Group ID, TMGI, Group TMSI), network slice information (e.g. S-NSSAI), DNN. 
     Step  5 : After selecting a UDM  320 , the AMF- 2   350  may send a message, such as GC Session Information Request message  810 , to the UDM  320  to get information related to GC Session. The GC Session Information Request message  810  may include one or more of the session information contained in the received GC Session Establishment Request message  805  in step  3  and TMGI if the AMF assigned a TMGI for the UE group. In some embodiments, the AMF- 2   350  use the Nudm_SDM_Get service of the UDM  320  to get information related to GC Session. 
     The AMF- 2   350  may also implicitly register itself to the UDM  320  as a serving AMF- 2  function for the GC Session. Alternatively, the AMF- 2   350  may explicitly register itself to the UDM  320  as a serving the functionality of the AMF- 2   350  for the GC Session by using Nudm_UECM_Registration service with modification discussed under detailed examples of operations. The AMF- 2   350  may provide any combination of following information: GC Session ID, AF-Service-Identifier, Internal Group ID, TMGI, network slice information (e.g. S-NSSAI), DNN. 
     Step  6   a:  Following receipt of the GC Session Information Request message  810  from the AMF- 2   350 , the UDM  320  may send a request, e.g. a GC Session information request message  812 , to the UDR  321  to get the information related to GC Session. The GC Session Information Request message  810  may include any combination of following information: the AF-Service-Identifier ID, and External Group ID, network slice information (S-NSSAI), DNN, TMGI. If the UDM has the mapping between External Group ID and UE Group ID (e.g. Internal-Group ID), the UDM may also include the Internal-Group ID. The UDM  320  may create a TMGI and also sends this information to the UDR  321 . 
     The GC Session information request message  810  sent in step  6   a  may be implemented by using Nudr DM Query service of the UDR  321  to request for GC Session Management Subscription data. The UDM  320  may include AF-Service-Identifier, or Internal Group Identifier and/or TMGI (if the TMGI is available) as data key to get the GC Session Management Subscription data. 
     Step  6   b:  Following receipt of the GC Session information request message  812  from the UDM  820 , the UDR  321  sends a GC Session information response message  814  to the UDM  320 . The GC Session information response message  814  may include UE Group ID (e.g. Internal-Group ID and/or TMGI (if the TMGI is available)), list of UE IDs of UEs  202  in the UE Group, Location Information of GC Session (e.g. Addresses of RAN nodes, Geographic Zone ID(s)), and Network Function information if available (e.g. serving AMF, UPF Address(es), NEF Address). 
     The message GC Session information response message  812  sent in step  6 b may be implemented by using Nudr DM Query response of the UDR  320  Nudr_DM_Query service operation and may be further modified as described earlier. 
     Step  7 : The UDM  320  sends a message, e.g. GC Session information response  816 , to the AMF- 2   350 , which includes information received from the UDR  321  in step  5   b.  The UDM  320  may also send to the AMF- 2   350  the Internal-Group ID and/or the TMGI, one or more UEs in a list of UE IDs, Subscription information related to UE Group (e.g. Maximum bit rate of GC Session, Maximum traffic volume in a certain period), Network Slice Information (e.g. S-NSSAI), one or more SMF ID(s) or SMF address(es) if the UDM  320  is aware of SMF function that may be pre-configured or registered in the UDM  320  to serve GC Session. 
     The GC Session information response message  816  sent in step  7  may be implemented by using Nudm_SDM_Get response service of the UDR Nudm_SDM_Get service operation and is provided in this document with updates. 
     Step  8 : The AMF- 2   350  may perform PCF selection  818  to select a PCF  316  according to any suitable criteria. The additional information to select PCF  316  may be AF-Service-Identifier, which is to identify AF  322  and/or AS  402 . 
     Step  9   a:  The AMF- 2   350  may have local PCC rules for the GC Session. Otherwise, the AMF- 2   350  may send a message, e.g. GC Session Policy Request message  820 , to the selected PCF  316  to get the policies for the GC Session. The GC Session Policy Request message  820  may include an UE Group ID information (e.g. External Group ID, Internal-Group ID, TMGI), Application information (e.g. AF-Service-Identifier), Network Slice Information (e.g. S-NSSAI), DNN. 
     The GC Session Policy Request message  820  in step  9   a  may be implemented by using Npcf_SMPolicyControl_Create_Request as described in this document to establish a session with the PCF and get the default PCC Rules for the GC Session. 
     Step  9   b:  This step  822  is similar to step  9   a  described above with respect to  FIG. 4A . 
     Step  9   c:  Following receipt of the GC Session Information Request message  822  from the PCF  316 , the UDR  321  may send a message, e.g. GC Session Information Response message  824 , to the PCF. The GC Session Information Response message  824  may contain information on group communication Subscription information, such as: GC Session area information (e.g. geographical zone IDs, registration area(s), list of (R)AN nodes ID(s)), QoS requirements (resource type (e.g. GBR, delay critical GBR, or non-GBR), maximum flow data rate, guaranteed flow data rate, packet delay budget, expected or maximum group communication traffic volume in certain period of time), charging information, and Access Type (e.g. 5G RAT or 4G RAT), UE subscription information (Service Level Agreement, QoS policy, charging policy, traffic routing policy (Access type(s)), for example. 
     The GC Session Information Response message  824  sent in step  9 c may be implemented by using Nudr UDM Query response service. 
     Step  9   d:  The PCF  316  may send a message, e.g. GC Session Policy Response message  826 , to the AMF- 2   350 . The GC Session Policy Response message  826  may include all or part of information the PCF  316  received from the UDR  321 . The PCF  316  may generate Access and Mobility management policy for the AMF- 2   350  for the GC Session. For example, the PCF  316  may send the location information of the GC Session, such as the one or more of (R)AN Address(es) (such as (R)AN ID(s), or (R)AN IP address(es)), each (R)AN node may have a one or more of Cell ID(s). 
     The GC Session Policy Response message  826  sent in step  9   d  may be implemented by using Npcf_SMPolicyControl_Create response service as described in this document. 
     Step  10 : The AMF- 2   350  may perform SMF selection  828  to select and SMF  310  to establish user plane connection for the GC Session by one or more of the following methods:
         (1) SMF information is pre-configured in the AMF- 2   350 ;   (2) The AMF- 2   350  may obtain the SMF  310  information from UDM  320  in step  7  if the UDM  320  has information of SMF(s)  310  that could serve the GC Session;   (3) The AMF- 2   350  may request the NRF  318  to get the address of the SMF  310  (e.g., SMF address). In method (3), the AMF- 2   350  may provide NRF  318  with one or more of following information: application information (e.g. AF-Service-Identifier), Network Slice Information (e.g. S-NSSAI), Geographic location of group communication service (e.g. Geographic Zone ID(s), or (R)AN Address(es)), Type of Application (e.g. V2X Application, IoT Application, Local Area Network (LAN), Video Streaming, Video Broadcasting), Application ID, for NRF  318  to select an MSF  310 . The NRF  318  may provide the AMF- 2   350  a list of SMF set(s) or a list of SMF instances, and NRF  318  may provide SMF profiles. The SMF profile may contain one or more of following attributes: SMF Set ID, SMF instance ID, SMF instance address (e.g. IP address(es), FQDN), application information (e.g. AF-Service-Identifier(s), AF ID(s)), Network Slice Information (e.g. S-NSSAI), Geographic location of group communication service (e.g. Geographic Zone ID(s), or (R)AN Address(es)), Type of Application (e.g. V2X Application, IoT Application, Local Area Network (LAN), Video Streaming, Video Broadcasting), Application ID(s). Based on the information provided by the NRF  318 , the AMF- 2   350  selects an SMF set, or an SMF instance of an SMF set.       

     Some SMF instances may be configured to serve a certain area. The AMF- 2   350  may use the information of AMF- 1   308  in order to find the UE locations (e.g., locations of UEs  202 ) in order to select a MSF  310 . For example, the AMF- 2   350  may request the AMF- 1   308  to provide the UE location (e.g., location of the UE  202 ) by using Namf_Location_ProvidePositioninglnfo service of AMF- 1   308  described in this document with possible modifications. The AMF- 1   308  provides AMF- 2   350  with UE locations. 
     Step  11 : The AMF- 2   350  may send a message, e.g. GC Session Establishment Request message  830 , to the selected SMF  310  to establish GC Session. In some embodiments, the GC Session Establishment Request message  830  may be implemented by using Nsmf_GCSession_CreateSMContext_Request as described under detailed examples of operations. 
     Steps  12 : Similar to the UDM selection method described in step  4  above with respect to  FIG. 4A . 
     Step  13  of  FIG. 7B : Similar to the messages sent by the SMF  310  described in step  4  above with respect  FIG. 4A . 
     Step  14  to  28  of  FIG. 7B  and  FIG. 7C : Similar to step  5  to  20  described above with respect to  FIG. 4A  and  FIG. 4B . 
     Steps  1   a  and  14   b  of  FIG. 7B : similar to steps  5   a  and  5   b,  respectively, as described above with respect to  FIG. 4A . 
     Step  15  of  FIG. 7B : similar to step  6  described above with respect to  FIG. 4A . 
     Step  16  of  FIG. 7B : similar to step  7  described above with respect to  FIG. 4A . 
     Step  17  of  FIG. 7B : similar to step  8  described above with respect to  FIG. 4A . 
     Steps  18   a  and  18   b  of  FIG. 7B : similar to steps  9   a  and  9   b,  respectively, described above with respect to  FIG. 4A . 
     Step  19  of  FIG. 7B : similar to step  10  described above with respect to  FIG. 4A . 
     Steps  20   a  and  20   b  of  FIG. 7B : similar to steps  11   a  and  11   b,  respectively, described above with respect to  FIG. 4A . 
     Step  21  of  FIG. 7B : The SMF  310  may select an AMF- 2   350  by using the same methods as described in step  12  above with respect to  FIG. 4A . Then the SMF may send a message  858  GC Session Establishment Request to the selected AMF- 2   350 ; the information included in the message  858  is similar to the message  530  in step  12  described above with respect to  FIG. 4A . 
     Step  22   a  of  FIG. 7B : The AMF- 2   350  may perform UE location discovery  860  in order to find the (R)AN node  302  that is/are serving UE  202  by using the information provided by the SMF  310  in step  21 . The AMF- 2   350  may use the methods described in step  13  described above with respect to  FIG. 4A  to discover the (R)AN node  302  that is/are serving UE  202 . 
     Steps  22   b  and  22   c  of  FIG. 7B : similar to steps  14   a  and  14   b,  respectively, described above with respect to  FIG. 4B . 
     Step  23  of  FIG. 7C : similar to step  15  described above with respect to  FIG. 4B . 
     Steps  24   a  and  24   b  of  FIG. 7C : similar to step  16   a  and  16   b,  respectively, described above with respect to  FIG. 4B . 
     Steps  25   a  and  25   b  of  FIG. 7C : similar to step  17   a  and  17   b,  respectively, described above with respect to  FIG. 4B . 
     Steps  26   a  and  26   b  of  FIG. 7C : similar to step  18   a  and  18   b,  respectively, described above with respect to  FIG. 4B . 
     Steps  27   a  and  27   b  of  FIG. 7C : similar to step  19   a  and  19   b,  respectively, described above with respect to  FIG. 4B . 
     Steps  28   a  and  28   b  of  FIG. 7C : similar to step  20   a  and  20   b,  respectively, described above with respect to  FIG. 4B . 
       FIG. 8  illustrates an embodiment of a GC Session Announcement. Steps  29  to  34  of  FIG. 8  are similar to those described above with respect to steps  21  to  26   FIG. 5 . 
       FIG. 9  illustrates a service-based architecture wherein both AMF- 1   308  and the AMF- 2   350 - 3  have a N1 connection to UE  202 . In the embodiment illustrated by  FIG. 10 , when the UE  202  has simultaneous unicast and GC Sessions, the AMF- 2   350 - 3  may have an N1 connection to the UE  202  as shown in  FIG. 9 . The AMF- 2   350 - 3  supports CN functions to establish and manage the GC Session. The AMF- 2   350 - 3  supports CN functions to send messages related to GC Session to the UE  202  using an N1 interface. In the service-based architecture shown in  FIG. 9 , the MSF  310 - 3  has all the functional of the MSF  310 - 1  shown in the service-based architecture of  FIG. 2 , with additional functionality described above. Similarly, the AMF  850 - 3  has all the functional of the AMF  850 - 1  shown in the service-based architecture of  FIG. 2 , with additional functionality described above. 
     In these embodiments, the GC Session may include multiple data flows. Each data flow may be represented by group communication flow identifier. The MSF  310 - 3  is similar to SMF  310  described above, however, it includes additional functionality to create the group communication flow ID for each data flow. The AF  322  may request multiple data flows. The AF  322  may include information (for example IP address, UDP or TCP port number(s), upper layer protocol) to distinguish data flows in the GC Session request. The MSF  310 - 3  may establish one GC Session that carries multiple data flows. 
     When the AF  322  wants to modify the GC Session, the AF  322  may send a message to the NEF  314  that carries one or more of following information: AF Transaction ID, UE information, GC Session location information, TMGI, QoS information, group communication flow ID, QoS information. The NEF  314  may map the GC Session location information (such as Geographic Zone ID to (R)AN Address(es) or (R)AN ID(s), and may include for each (R)AN node one or more Cell IDs) 
     Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention. 
     An aspect of the disclosure provides a method for supporting operation of a wireless communication network in which a first Access Management Function (AMF) is associated with a first UE and the first AMF is configured to manage access and mobility for the first UE. Such a method includes a core network control plane function of the wireless communication network infrastructure, after receipt of one or more messages from a core network portion of the wireless communication network, communicating with an access node over a control plane interface to cause the access node to support a group communication (GC) session with a plurality of UEs, including the first UE. In some embodiments, the core network control plane function is implemented in the first AMF. In some embodiments, the core network control plane function is a second AMF function that operates separately from the first AMF. In some embodiments, the one or more messages received from the core network portion of the wireless communication network includes a single GC Session establishment request. In some embodiments, the core network portion of the wireless communication network includes a second core network control plane function to manage one or more GC Sessions, such as establishment, modification, and release of one or more GC Sessions. The second core network control plane function may be implemented in an existing Session Management Function (SMF). In the following, the functionalities of the second core network control plane function is implemented in a SMF function. The GC Session establishment request is received by the SMF. In some embodiments, the single GC session establishment request is received from an Application Function (AF) and relayed by the Network Exposure Function (NEF) to the SMF. In some embodiments, the control plane interface is an N2 interface and the core network control plane function communicates with the access node over the N2 interface without utilizing an N1 interface. In some embodiments, the method further includes the core network control plane function instructing the first AMF to send a message to the first UE. In some embodiments, the message comprises a session management message for providing the first UE with information about the GC Session. In some embodiments, the method further includes the core network control plane function interacting over control plane messaging with the core network portion of the wireless communication network to discover the first Access Management Function. In some embodiments, the method further includes the core network control plane function receiving a reply from the first AMF, and forwarding the reply to a Session Management Function (SMF). In some embodiments, the method further includes the core network control plane function interacting with the first AMF to perform UE location discovery. In some embodiments, the method further includes the core network control plane function subscribing to notification messages from multiple AMFs related to UEs which join to the GC Session. In some embodiments, the first Access Management Function is operatively coupled to the core network control plane function. In some such embodiments, the method further includes core network control plane function, after receipt of a further message from the first AMF, the further message indicative of a communication from the first UE, forwarding the further message to the core network portion of the wireless communication network. This can be for a UE requesting to subscribe to the GC Session. In some embodiments, one or more additional Access Management Functions are operative to communicate with different respective ones of the plurality of UEs. In some such embodiments, the method further includes the core network control plane function discovering the one or more additional Access Management Functions, and subsequently relaying messages between the one or more additional Access Management Functions and the core network portion of the wireless communication network. 
     Another aspect of the disclosure provides a method for supporting operation of a wireless communication network by a Session Management Function (SMF) of the wireless communication network infrastructure. The method includes determining and storing identities of a first access management function (AMF) operative to support communication with a plurality of UEs, and a core network control plane function operative to support a GC Session with the plurality of UEs. The method further includes interacting with the core network control plane function to cause the core network control plane function to communicate with an access node over a control plane interface to cause the access node to support a GC Session with the plurality of UEs. In some embodiments, the method further includes receiving a request from an AF, either directly or indirectly via an NEF, for establishment of a GC Session and selecting the second AMF for the GC Session. In some embodiments, the control plane interface is an N2 interface, the first AMF includes an N1 interface, the core network control function communicating with the access node over the N2 interface without utilizing an N1 interface. In some embodiments, the method further includes the SMF forwarding messaging relating to a unicast communication to a first AMF, and forwarding messaging relating to the establishment, configuration and operation of the GC Session to the core network control plane function. In some embodiments, the first AMF is operatively coupled to the core network control plane function, and the method further includes the SMF sending messaging relating to a unicast session for the first UE to the core network control plane function for forwarding to the first AMF by the core network control plane function. 
     Another aspect of the disclosure provides a method for establishing a communications session with a first UE. The method includes establishing, by a core network portion of a wireless communication network, a session with a second Access Management Function (AMF). Querying, by the second AMF, the core network portion, to determine a first AMF associated with the first UE and utilizing the first AMF to determine a location of the first UE. The second AMF acts as a proxy for the first AMF for managing the communication session between the core network and the first UE. 
     In another aspect of the disclosure, the first AMF transfers a message through the second AMF for relaying to the core network portion. 
     In another aspect of the disclosure, the second AMF transfers a message through the first AMF. 
     Another aspect of the disclosure includes a plurality of UEs and a plurality of AMFs. The first UE is one of the plurality of UEs. The first AMF is one of the plurality of AMFs. Each of the plurality of AMFs services one of the plurality of UEs, and the second AMF acts as a proxy for the plurality of AMFs to manage communication sessions between the core network and the plurality of UEs. 
     In another aspect of the disclosure, the communication sessions include a broadcast communication session. 
     In another aspect of the disclosure, the communication sessions include a multicast communication session. 
     In another aspect of the disclosure, the communication sessions include a unicast communication session. 
     In another aspect of the disclosure, the message is a GC Session Announcement message, and the method further includes relaying, by the second AMF to the first AMF, the message being to the first UE. 
     Another aspect of the disclosure includes, in response to the message, relaying from the first AMF through the second AMF, a confirmation message, to the core network. 
     In another aspect of the disclosure, the second AMF combines information received from the first AMF with the message before relaying the message to the core network portion. 
     In another aspect of the disclosure, the second AMF stores the message received from the first AMF until a number of further messages are received from the first AMF before relaying the message and the further messages to the core network portion. 
     In another aspect of the disclosure, communications between the first AMF and the second AMF utilize a service based interface, the first AMF supports communications between the first UE and the second AMF, and the second AMF supports communications between the first AMF and the core network portion. 
     In another aspect of the disclosure, determining a location of the first UE comprises accessing a list of RAN node addresses provided by the core network portion. 
     In another aspect of the disclosure, determining a location of the first UE comprises performing a discovery procedure to identify the first AMF. 
     In another aspect of the disclosure, the message includes the second AMF providing an internal group ID to the first AMF, the first AMF responding to the second AMF with a RAN node address serving the first UE. 
     In another aspect of the disclosure, the message includes an identifier of the core network portion or an identifier of the second AMF. 
     In another aspect of the disclosure, the message results from a notification service of the first AMF, the second AMF subscribing the notification service on behalf of the core network portion. 
     In another aspect of the disclosure, the message comprises the second AMF creating a Temporary Mobile Group Identity for the first UE. 
     An aspect of the disclosure provides a method for managing a group communications (GC) session. The method is performed by an Access Management Function (AMF) and includes: receiving a GC session establishment request from a session management function (SMF); transmitting to an access node, the GC session establishment request; receiving a GC session establishment response from the access node; transmitting the GC session management response to the session management function; communicating with the radio access node over a service based interface to cause the access node to support a group communication session with a first UE. In some embodiments, the AMF is selected by the session management function. In some embodiments, the method includes selecting a data management function and transmitting a GC session information request to the to the data management function, and receiving a GC session information response from the data management function with the GC session information response comprising parameters of the GC session. In some embodiments, the method includes selecting a policy control function and transmitting a GC session policy request to the policy control function, and receiving a GC session policy response from the policy control function where the GC session policy response comprising an access and mobility management policy for the GC session. In some embodiments, the AMF selects the session management function. In some embodiments, the method includes discovering the access node associated with the first UE. In some embodiments, the method includes transmitting a GC serving function registration request to the data repository function, and receiving a GC serving function registration response from the data repository function where the GC serving function registration response includes information associating a UE group and a network resource and the UE group includes the first UE. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a broadcast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a multicast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the plurality of UEs is defined by a group identifier. 
     An aspect of the disclosure provides a method for managing a group communications (GC) session. The method is performed by an Access Management Function (AMF) and includes transmitting a discover access management function request to a network discovery function to identify a first unicast AMF. The first unicast AMF is configured to manage access and mobility for a first UE associated with an access node. Receiving from a session management function, a GC session announcement request. Transmitting the GC session announcement request to the first unicast AMF. Receiving from the first unicast AMF, a GC session announcement response. Transmitting the GC session announcement response to the session management function. Receiving from the first unicast AMF, a GC session announcement notification. Transmitting the GC session announcement notification to the session management function. Communicating with the access node over a service based interface to cause the access node to support a group communication session with the first UE. The AMF acts as a proxy for communications between the first unicast AMF and the session management function. In some embodiments, transmitting from the AMF to the first unicast AMF and receiving from the first unicast AMF by the AMF is done over the service based interface. In some embodiments, the AMF acts as a proxy for communications between a plurality of unicast access management functions and the session management function and the first unicast AMF is one of the plurality of access management functions. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a broadcast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a multicast communication to the plurality of UEs. In some embodiments, the first UE is one of a plurality of UEs and the plurality of UEs is defined by a group identifier. 
     An aspect of the disclosure provides an access management function (AMF) including a network interface for receiving and transmitting messages, a processor, and a non-transient memory for storing instructions. When executed by the processor, the instructions cause the AMF to transmit a discover access management function request to a network discovery function to identify a first unicast AMF. The first unicast AMF is configured to manage access and mobility for a first UE associated with an access node. Receive from a session management function, a GC session announcement request. Transmit the GC session announcement request to the first unicast AMF. Receive from the first unicast AMF, a GC session announcement response. Transmit the GC session announcement response to the session management function. Receive from the first unicast AMF, a GC session announcement notification. Transmit the GC session announcement notification to the session management function. Communicate with the access node over a service based interface to cause the access node to support a group communication session with the first UE. The AMF acts as a proxy for communications between the first unicast AMF and the session management function. In some embodiments, transmitting from the AMF to the first unicast AMF and receiving from the first unicast AMF by the AMF is done over the service based interface. In some embodiments, the AMF acts as a proxy for communications between a plurality of unicast access management functions and the session management function, the first unicast AMF being one of the plurality of access management functions. In some embodiments, the first UE is one of a plurality of UEs and the GC session comprises a broadcast communication or a multicast communication to the plurality of UEs. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. 
     Through the descriptions of the preceding embodiments, the present invention may be implemented by using hardware only or by using software and a necessary universal hardware platform. Based on such understandings, the technical solution of the present invention may be embodied in the form of a software product. The software product may be stored in a non-volatile or non-transitory storage medium, which can be a compact disk read-only memory (CD-ROM), USB flash disk, or a removable hard disk. The software product includes a number of instructions that enable a computer device (personal computer, server, or network device) to execute the methods provided in the embodiments of the present invention. For example, such an execution may correspond to a simulation of the logical operations as described herein. The software product may additionally or alternatively include number of instructions that enable a computer device to execute operations for configuring or programming a digital logic apparatus in accordance with embodiments of the present invention. 
     Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.