Patent Publication Number: US-2022225438-A1

Title: Session and mobility management method using nas protocols

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 of International Application No. PCT/KR2020/005801 filed on Apr. 29, 2020, which claims priority to Korean Patent Application No. 10-2019-0051861 filed on May 2, 2019 and Korean Patent Application No. 10-2019-0057732 filed on May 16, 2019, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     The disclosure relates to a method for managing a session in a next-generation 5G communication environment, and more particularly to a method of processing and managing session reactivation in a situation where mobility occurs through NAS messages, or an apparatus for performing this function. 
     2. Description of Related Art 
     To meet the ever increasing demand for wireless data traffic since the commercialization of 4G communication systems, efforts have been made to develop improved 5G or pre-5G communication systems. As such, 5G or pre-5G communication systems are also called “beyond 4G network system” or “post Long Term Evolution (LTE) system”. To achieve high data rates, 5G communication systems are being considered for implementation in the extremely high frequency (mmWave) band (e.g., 60 GHz band). To decrease path loss of radio waves and increase the transmission distance in the mmWave band, various technologies including beamforming, massive multiple-input multiple-output (massive MIMO), full dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large scale antennas are considered for 5G communication systems. To improve system networks in 5G communication systems, technology development is under way regarding evolved small cells, advanced small cells, cloud radio access networks (cloud RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving networks, cooperative communication, coordinated multi-points (CoMP), interference cancellation, and the like. Additionally, advanced coding and modulation (ACM) schemes such as hybrid frequency shift keying and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC), and advanced access technologies such as filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) are also under development for 5G systems. 
     Meanwhile, the Internet is evolving from a human centered network where humans create and consume information into the Internet of Things (IoT) where distributed elements such as things exchange and process information. There has also emerged the Internet of Everything (IoE) technology that combines IoT technology with big data processing technology through connection with cloud servers. To realize IoT, technology elements related to sensing, wired/wireless communication and network infrastructure, service interfacing, and security are needed, and technologies interconnecting things such as sensor networks, machine-to-machine (M2M) or machine type communication (MTC) are under research in recent years. In IoT environments, it is possible to provide intelligent Internet technology services, which collect and analyze data created by interconnected things to add new values to human life. Through convergence and combination between existing information technologies and various industries, IoT technology may be applied to various areas such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, health-care, smart consumer electronics, and advanced medical services. 
     Accordingly, various attempts are being made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks and machine-to-machine (M2M) or machine type communication (MTC) are being realized by use of 5G communication technologies including beamforming, MIMO, and array antennas. Application of cloud RANs as a big data processing technique described above may be an instance of convergence of 5G technology and IoT technology. 
     With the recent development of next-generation 5G communication systems, a session and mobility management method using NAS protocols is required. 
     With 5G mobile communication, the AMF being a management entity that manages the mobility of a terminal, and the SMF being an entity that manages sessions have been separated. Accordingly, as the entities that manage the mobility management and the session are separated, unlike the operation method managed collectively by the MME in the existing 4G LTE communication, the communication method and the communication management method between the terminal and the network entities have been changed. 
     With 5G communication, for non-3GPP access, mobility management is performed first by use of the N3IWF and through the AMF, and session management is performed through the SMF. In addition, mobility management is performed through the AMF, and security-related information, which is an important element in mobility management, is also dealt with. 
     On the other hand, in 4G, the MME is in charge of mobility management and session management, and is responsible for managing this. In addition to these 5G communication schemes, there are entities for 4G and 5G communication in 5G communication, and some 4G communication entities can be used to perform 5G communication even when the architecture configuration is of a non-standalone architecture. 
     Accordingly, the disclosure proposes a method that, in response to a mobility occurrence when communication is performed using non-access stratum (NAS) protocols in 5G communication, performs session activation, mobility management, and session management by using the NAS protocols, and proposes a method for improving communication performance by making mobility and session management efficient. 
     SUMMARY 
     According to an embodiment of the disclosure for achieving the above-mentioned objective, a method performed by a terminal in a wireless communication system may include: transmitting data based on a multi-access (MA) protocol data unit (PDU) session using both a 3rd generation partnership project (3GPP) access network and a non-3GPP access network; in case that user-plane resources of the MA PDU session for at least one of the 3GPP access network or the non-3GPP access network are released, transmitting a service request message including uplink data status information indicating that uplink data corresponding to an identity (ID) of the MA PDU session is pending to an entity performing an access and mobility management function (AMF) over a released access network; and receiving a service accept message including PDU session reactivation result information indicating a result of reestablishment of the user-plane resources of the MA PDU session from the entity. 
     Additionally, according to an embodiment of the disclosure, a method performed by an entity performing an access and mobility management function (AMF) in a wireless communication system may include: in case that user-plane resources of a multi-access (MA) protocol data unit (PDU) session for 3rd generation partnership project (3GPP) access are released, receiving a service request message including uplink data status information indicating that uplink data corresponding to the MA PDU session is pending from a terminal over the 3GPP access; and transmitting a service accept message including PDU session reactivation result information indicating a result of reestablishment of the user-plane resources of the MA PDU session to the terminal. 
     Additionally, according to an embodiment of the disclosure, a terminal in a wireless communication system may include: a transceiver; and a controller configured to control the transceiver to transmit data based on a multi-access (MA) protocol data unit (PDU) session using both a 3rd generation partnership project (3GPP) access network and a non-3GPP access network, control the transceiver to transmit, in case that user-plane resources of the MA PDU session for at least one of the 3GPP access network or the non-3GPP access network are released, a service request message including uplink data status information indicating that uplink data corresponding to an identity (ID) of the MA PDU session is pending to an entity performing an access and mobility management function (AMF) over a released access network, and control the transceiver to receive a service accept message including PDU session reactivation result information indicating a result of reestablishment of the user-plane resources of the MA PDU session from the entity. 
     In addition, according to an embodiment of the disclosure, an entity performing an access and mobility management function (AMF) in a wireless communication system may include: a transceiver; and a controller configured to control the transceiver to receive, in case that user-plane resources of a multi-access (MA) protocol data unit (PDU) session for 3rd generation partnership project (3GPP) access are released, a service request message including uplink data status information indicating that uplink data corresponding to the MA PDU session is pending from a terminal over the 3GPP access, and control the transceiver to transmit a service accept message including PDU session reactivation result information indicating a result of reestablishment of the user-plane resources of the MA PDU session to the terminal. 
     Through the disclosure, for 5G communication in 5G communication environments, the NAS protocols are used to manage mobility and activate a session if the session is deactivated to thereby improve communication performance, so that it is possible to efficiently perform communication. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a terminal-network environment for performing communication with improved performance by managing mobility and activating a session by using NAS protocols in a 5G network according to an embodiment of the disclosure. 
         FIG. 2  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
         FIG. 3  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
         FIG. 4  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
         FIG. 5  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
         FIG. 6  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
         FIG. 7  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
         FIG. 8  is a diagram illustrating the structure of a terminal according to an embodiment of the disclosure. 
         FIG. 9  is a diagram illustrating the structure of a network entity according to an embodiment of the present disclosure. 
         FIG. 10  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments of the disclosure will be described in detail with reference to the accompanying drawings. Here, it should be noted that the same components in the accompanying drawings are indicated by the same symbols as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the disclosure will be omitted. 
     In the description of embodiments of the present specification, descriptions of technical details well known in the art and not directly related to the disclosure may be omitted. This is to more clearly convey the gist of the disclosure without obscurities by omitting unnecessary descriptions. 
     Likewise, in the drawings, some elements are exaggerated, omitted, or only outlined in brief. Also, the size of each element does not necessarily reflect the actual size. The same reference symbols are used throughout the drawings to refer to the same or corresponding parts. In each figure, the same or corresponding elements are assigned the same reference numerals. 
     Advantages and features of the disclosure and methods for achieving them will be apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments disclosed below but may be implemented in various different ways, and the embodiments are provided only to complete the disclosure and to fully inform the scope of the disclosure to those skilled in the art to which the disclosure pertains. The same reference symbols are used throughout the specification to refer to the same parts. 
     Those terms used in the following description for identifying an access node, indicating a network entity, indicating a message, indicating an interface between network entities, and indicating various identification information are taken as illustration for ease of description. Accordingly, the disclosure is not limited by the terms to be described later, and other terms referring to objects having an equivalent technical meaning may be used. 
     For convenience of description, the disclosure uses terms and names defined in the standards for 5G and LTE systems. However, the disclosure is not limited by the above terms and names, and can be equally applied to systems conforming to other standards. 
     That is, in the detailed description of the embodiments of the disclosure, the communication standards set by 3GPP will be focused, but it should be understood by those skilled in the art that the subject matter of the disclosure is applicable to other communication systems having similar technical backgrounds without significant modifications departing from the scope of the disclosure. 
     First Embodiment 
       FIG. 1  illustrates an example of a terminal-network environment for performing communication with improved performance by managing mobility and activating a session by using NAS protocols in a 5G network according to an embodiment of the disclosure. 
     In an embodiment of the disclosure, assuming a 5G network, it is considered that the user plane function (UPF), the session management function (SMF), the access and mobility management function (AMF), the 5G radio access network (5G RAN), the user data management (UDM), and the policy control function (PCF) constitute a network system. Meanwhile, for authentication of these entities, it is also considered that the authentication server function (AUSF), and the authentication, authorization and accounting (AAA) exist in the system. 
     On the other hand, the N3 interworking function (N3IWF) exists for the case where the terminal communicates through non-3GPP access, and, when communicating through non-3GPP access, session control is performed in the terminal, non-3GPP access, N3IWF, and SMF for session management, and mobility control occurs in the terminal, non-3GPP access, N3IWF, and AMF for mobility management. 
     In 5G, the mobility management and session management entity is separated into the AMF and SMF. On the other hand, for 5G communication, not only a standalone deployment structure where communication is performed using only 5G communication entities but also a non-standalone deployment structure using 4G and 5G entities is being considered. 
     Although the communication network on which the disclosure is based is assumed to be 5G and 4G LTE networks, it can be applied if the same concept is applied to other systems within a range that can be understood by a person of ordinary skill in the art. 
     (Method 1) 
       FIG. 2  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     At step  201 , the UE has established a PDU session with the UPF to communicate. Here, the PDU session has been established through the 5G RAN; that is, data communication is being performed through the UE, 5G RAN and UPF. 
     At step  203 , the terminal has established a PDU session with the UPF to communicate. In this case, the PDU session has been established through non-3GPP access, for example, WiFi, trusted WiFi, or non-trusted WiFi; that is, data communication is being performed through the UE, non-3GPP access and UPF. 
     At step  205 , the UE transmits a service request to the AMF. Here, the UE may transmit a service request to the AMF through 3GPP access. In another embodiment, the UE may transmit a service request to the AMF through non-3GPP access. In this case, the status of the multi-access PDU session may be informed to the AMF through a multi-access PDU session status information element. 
     This multi-access PDU session status information element is configured as shown in Table 1. In addition, the multi-access PDU session status information can be coded and interpreted as shown in Table 2. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session status |E| 
                 octet 1 
               
               
                 Length of multi access PDU session status contents  
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 PSI(x) shall be coded as follows. 
               
               
                 PSI(0): 
               
               
                 Bit 1 of octet 3 is spare and shall be coded as zero 
               
               
                 PSI(1) - PSI(15): 
               
               
                 0 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION INACTIVE 
               
               
                 1 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION ACTIVE 
               
               
                 All bits in octet 5 to 34 are spare and shall be coded as zero, if the respective octets is included in the information 
               
               
                 element 
               
               
                   
               
            
           
         
       
     
     In addition, this multi-access PDU session status information element is an information element included in the service request message as shown in Table 3. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 IEI 
                 Information Element 
                 Type/Reference 
                 Presence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol discriminator 
                 Extended protocol discriminator 9.2 
                 M 
                 V 
                 1 
               
               
                   
                 Security header type 
                 Security header type 9.3 
                 M 
                 V 
                 1/2 
               
               
                   
                 Spare half octet 
                 Spare half octet 9.5 
                 M 
                 V 
                 1/2 
               
               
                   
                 Service request message identity 
                 Message type 9.7 
                 M 
                 V 
                 1 
               
               
                   
                 ngKSI 
                 NAS key set identifier 9.11.3.32 
                 M 
                 V 
                 1/2 
               
               
                   
                 Service type 
                 Service type 9.11.3.50 
                 M 
                 V 
                 1/2 
               
               
                   
                 5G-S-TMSI 
                 5GS mobile identity 9.11.3.4 
                 M 
                 LV-E 
                 9 
               
               
                 40 
                 Uplink data status 
                 Uplink data status 9.11.3.57 
                 O 
                 TLV 
                 4-34 
               
               
                 50 
                 PDU session status 
                 PDU session status 9.11.3.44 
                 O 
                 TLV 
                 4-34 
               
               
                 25 
                 Allowed PDU session status 
                 Allowed PDU session status 9.11.3.13 
                 O 
                 TLV 
                 4-34 
               
               
                 71 
                 NAS message container 
                 NAS message container 9.11.3.33 
                 O 
                 TLV-E 
                 4-n 
               
               
                   
                 Multi access PDU session status 
                 Multi access PDU session status 
                 O 
                 TLV 
                 4-34 
               
               
                   
               
            
           
         
       
     
     At step  207 , the AMF transmits a PDU session update request message to the SMF. 
     At step  209 , the SMF transmits a PDU session update response message to the AMF. 
     At step  211 , the AMF transmits a service accept message to the UE as shown in Table 4. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 IEI 
                 Information Element 
                 Type/Reference 
                 Presence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol discriminator 
                 Extended protocol discriminator 9.2 
                 M 
                 V 
                 1 
               
               
                   
                 Security header type 
                 Security header type 9.3 
                 M 
                 V 
                 1/2 
               
               
                   
                 Spare half octet 
                 Spare half octet 9.5 
                 M 
                 V 
                 1/2 
               
               
                   
                 Service accept message identity 
                 Message type 9.7 
                 M 
                 V 
                 1 
               
               
                 50 
                 PDU session status 
                 PDU session status 9.11.3.44 
                 O 
                 TLV 
                 4-34 
               
               
                 26 
                 PDU session reactivation result 
                 PDU session reactivation result 9.11.3.42 
                 O 
                 TLV 
                 4-34 
               
               
                 72 
                 PDU session reactivation result error cause  
                 PDU session reactivation result error cause 9.11.3.43 
                 O 
                 TLV-E 
                 5-515 
               
               
                 78 
                 EAP message 
                 EAP message 9.11.2.2 
                 O 
                 TLV-E 
                 7-1503 
               
               
                   
                 Multi access PDU session reactivation result 
                 Multi access PDU session reactivation result 
                 O 
                 TLV-E 
                 4-34 
               
               
                   
                 Multi access PDU session reactivation result error  
                 Multi access PDU session reactivation result error  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 cause 
                 cause 
               
               
                   
               
            
           
         
       
     
     Here, a multi-access PDU session reactivation result may be transmitted to inform information about the result of the multi-access PDU session activation requested in the service request. This information may be transmitted by being included in the multi-access PDU session reactivation result information element as shown in Table 5 included in the service accept message at step  211 . The information element in Table 5 is coded and interpreted as in Table 6. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactvaton result |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
             
            
               
                 PSI(x) shall be coded as follows. 
               
               
                 PSI(0): 
               
               
                 Bit 1 of octet 3 is spare and shall be coded as zero 
               
               
                 PSI(1) - PSI(15): 
               
               
                 0 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION INACTIVE 
               
               
                 1 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION ACTIVE 
               
               
                 All bits in octet 5 to 34 are spare and shall be coded as zero, if the respective octets is included in the information 
               
               
                 element 
               
               
                   
               
            
           
         
       
     
     Additionally, at this time, to inform information about an error occurrence together with the result of the multi-access PDU session activation requested in the service request, information about the error is included in the multi-access PDU session reactivation result error cause information element as shown in Table 7 and transmitted. This multi-access PDU session reactivation result error cause information element is transmitted by being included in the service accept message at step  211 . Coding and interpretation for Table 7 are shown in Table 8. That is, it is possible to notify various causes (reasons) given in the 5GMM cause information element, such as insufficient resource for a PDU session, insufficient resource for a specific DNN or slice, or insufficient resource for a specific slice. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 7 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result error cause |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result error cause 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                 octet 3 
               
            
           
           
               
               
            
               
                 PDU session ID 
                 octet 4 
               
               
                 cause value 
                 octet 5 
               
               
                 . . . 
                   
               
               
                 PDU session ID 
                 octet 514* 
               
               
                 cause value 
                 octet 515* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 8 
               
               
                   
                   
               
             
            
               
                   
                   
                 PDU session is coded same as PDU session ID IE 
               
               
                   
                   
                 The cause value coded same as second octet of 5GMM cause  
               
               
                   
                   
                 information element 
               
               
                   
                   
               
            
           
         
       
     
     Alternatively, as another embodiment, there may be a method in which the AMF informs the UE of the result of multiple access PDU session reactivation by utilizing the existing PDU session reactivation result IE (information element). When using the existing PDU session reactivation result IE (information element), an information element notifying the UE that the AMF supports a multiple access PDU session or multiple access PDU session reactivation may be added. 
     The configuration of such multiple access PDU session or multiple access PDU session reactivation supporting indication IE (information element) is shown in Table 9 below, and the interpretation and coding thereof are shown in Table 9-1. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 9 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Multiple access PD session 
                 0 
                 0 
                 0 
                 Multiple Multiple access 
                 octet 1 
               
               
                 supporting indication |E| 
                 Spare 
                 Spare 
                 Spare 
                 PDU session supporting 
                   
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 9-1 
               
               
                   
               
             
            
               
                   
                 Multiple access PDU session supporting Indication (octet 1) 
               
               
                   
                 Bit 
               
               
                   
                 1 
               
               
                   
                 0 Multiple access PDU session is not supported 
               
               
                   
                 1 Multiple access PDU session is supported. 
               
               
                   
                 Bits 2, 3 and 4 are spare and shall be coded as zero. 
               
               
                   
               
            
           
         
       
     
     In addition, information about the access type that indicates the access at which reactivation has occurred or an error or problem has occurred may be added. 
     (Method 2) 
       FIG. 3  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     At step  301 , the UE has established a PDU session with the UPF to communicate. Here, the PDU session has been established through the 5G RAN; that is, data communication is being performed through the UE, 5G RAN and UPF. 
     At step  303 , the UE has established a PDU session with the UPF to communicate. In this case, the PDU session has been established through non-3GPP access, for example, WiFi, trusted WiFi, or non-trusted WiFi; that is, data communication is being performed through the UE, non-3GPP access and UPF. 
     At step  305 , the UE transmits a service request to the AMF. Here, the UE may transmit a service request to the AMF through non-3GPP access. In this case, the status of the multi-access PDU session may be informed to the AMF through a multi-access PDU session status information element. 
       FIG. 3  illustrates a case of executing a service request through non-3GPP access, and illustrates a case where the session can be recovered when the service request is sent through non-3GPP access but the access situation has changed from before. That is, for example, when 70% of the flow has been sent through 3GPP and 30% has been sent through non-3GPP before the service request, and when 80% of the flow is sent through 3GPP and 20% is sent through non-3GPP after the service request, such information may be notified by using this method. 
     In another embodiment, when an attempt to reactivate the session through a service request over non-3GPP access has failed due to a failure of RRC connection reestablishment, it is also possible to transfer all of the flow that has been transmitted over non-3GPP access to 3GPP access. In such a case, that is, when non-3GPP access is not recovered, all flows for these PDU sessions are transferred to 3GPP access to continue communication. 
     This multi-access PDU session status information element is configured as shown in Table 11. And, multi-access PDU session status information can be coded and interpreted as shown in Table 12. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 11 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session status |E| 
                 octet 1 
               
               
                 Length of multi access PDU session status contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 12 
               
               
                   
                   
               
             
            
               
                   
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                   
                 PSI(0): 
               
               
                   
                   
                 Bit 1 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 0 
                 indicates that the 5GSM state of the correspoinding  
               
            
           
           
               
               
               
            
               
                   
                   
                 multi access PDU session is multi access PDU 
               
               
                   
                   
                 SESSION INACTIVE 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 1 
                 indicates that the 5GSM state of the correspoinding  
               
            
           
           
               
               
               
            
               
                   
                   
                 multi access PDU session is multi access PDU 
               
               
                   
                   
                 SESSION ACTIVE 
               
               
                   
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                   
                 if the respective octet is included in the information element. 
               
               
                   
                   
               
            
           
         
       
     
     In addition, this multi-access PDU session status information element is an information element included in the service request message as shown in Table 13. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 13 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 Type 
                 Type 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service request  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                   
                 ngKSI 
                 NAS key set  
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 identifier 
                   
                   
                   
               
               
                   
                   
                 9.11.3.32 
                   
                   
                   
               
               
                   
                 Service type 
                 Service type 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.11.3.50 
                   
                   
                   
               
               
                   
                 5G-S-TMSI 
                 5GS mobile  
                 M 
                 LV-E 
                 9 
               
               
                   
                   
                 identity 9.11.3.4 
                   
                   
                   
               
               
                 40 
                 Uplink data status 
                 Uplink data status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.57 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 status 9.11.3.44 
                   
                   
                   
               
               
                 25 
                 Allowed PDU  
                 Allowed PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status  
                   
                   
                   
               
               
                   
                   
                 9.11.3.13 
                   
                   
                   
               
               
                 71 
                 NAS message  
                 NAS message  
                 O 
                 TLV-E 
                 4-n 
               
               
                   
                 container 
                 container 9.11.3.33 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status 
               
               
                   
               
            
           
         
       
     
     At step  307 , the AMF transmits a PDU session update request message to the SMF. 
     At step  309 , the SMF transmits a PDU session update response message to the AMF. 
     At step  311 , the AMF transmits a service accept message to the UE as shown in Table 14. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 14 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended prtocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 type 9.3 
                   
                   
                   
               
               
                   
                 Spare halt octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5. 
                   
                   
                   
               
               
                   
                 Service accept  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU Session status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.44 
                   
                   
                   
               
               
                 26 
                 PDU session  
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 reactivation result 
                 reactivation  
                   
                   
                   
               
               
                   
                   
                 result 9.11.3.42 
                   
                   
                   
               
               
                 72 
                 PDU session  
                 PDU session  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 reactivation result  
                 reactivation  
                   
                   
                   
               
               
                   
                 error cause 
                 result error cause 
                   
                   
                   
               
               
                   
                   
                 9.11.3.43 
                   
                   
                   
               
               
                 78 
                 EAP message 
                 EAP message 
                 O 
                 TLV-E 
                 7-1503 
               
               
                   
                   
                 9.11.2.2. 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 4-34 
               
               
                   
                 session reactivation  
                 session activation  
                   
                   
                   
               
               
                   
                 result 
                 result 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result error cause 
               
               
                   
               
            
           
         
       
     
     Here, a multi-access PDU session reactivation result may be transmitted to inform information about the result of the multi-access PDU session activation requested in the service request. This information may be transmitted by being included in the multi-access PDU session reactivation result information element as shown in Table 15 included in the service accept message at step  311 . 
     The information element in Table 15 is coded and interpreted as in Table 16. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 15 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivaton result contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 16 
               
               
                   
               
             
            
               
                 PSI(x) shall be coded as follows. 
               
               
                 PSI(0): 
               
               
                 Bit 1 of octet 3 is spare and shall be coded as zero 
               
               
                 PSI(1) - PSI(15): 
               
               
                 0 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION INACTIVE 
               
               
                 1 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION ACTIVE 
               
               
                 All bits in octet 5 to 34 are spare and shall be coded as zero, if the respective octets is included in the information 
               
               
                 element 
               
               
                   
               
            
           
         
       
     
     Additionally, at this time, to inform information about an error occurrence together with the result of the multi-access PDU session activation requested in the service request, information about the error may be included in the multi-access PDU session reactivation result error cause information element as shown in Table 17 and transmitted. This multi-access PDU session reactivation result error cause information element may be transmitted by being included in the service accept message at step  311 . 
     Coding and interpretation for Table 17 are shown in Table 18. 
     That is, it is possible to notify various causes (reasons) given in the 5GMM cause information element, such as insufficient resource for a PDU session, insufficient resource for a specific DNN or slice, or insufficient resource for a specific slice. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 17 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result error cause |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result error cause 
                 octet 2 
               
               
                   
                 octet 3 
               
               
                 PDU session ID 
                 octet 4 
               
               
                 cause value 
                 octet 5 
               
               
                 . . . 
                   
               
               
                 PDU session ID 
                 octet 514* 
               
               
                 cause value 
                 octet 515* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 18 
               
               
                   
               
             
            
               
                   
                 PDU session ID is coded same as PDU session ID IE 
               
               
                   
                 The cause value is coded same as second octet of 5GMM cause  
               
               
                   
                 information element 
               
               
                   
               
            
           
         
       
     
     Alternatively, as another embodiment, there may be a method in which the AMF informs the UE of the result of multiple access PDU session reactivation by utilizing the existing PDU session reactivation result IE (information element). When using the existing PDU session reactivation result IE (information element), an information element notifying the UE that the AMF supports a multiple access PDU session or multiple access PDU session reactivation may be added. 
     The configuration of such multiple access PDU session or multiple access PDU session reactivation supporting indication IE (information element) is shown in Table 19 below, and the interpretation and coding thereof are shown in Table 19-1. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 19 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Multiple access PDU session 
                 0 
                 0 
                 0 
                 Multiple Multiple access 
                 octet 1 
               
               
                 supporting indication |E| 
                 Spare 
                 Spare 
                 Spare 
                 PDU session supporting 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 19-1 
               
               
                   
                   
               
             
            
               
                   
                   
                 Multiple access PDU session supporting Indication (octet 1) 
               
               
                   
                   
                 Bit 
               
               
                   
                   
                 1 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 0 
                 Multiple access PDU session is not supported 
               
               
                   
                   
                 1 
                 Multiple access PDU session is supported. 
               
            
           
           
               
               
               
            
               
                   
                   
                 Bits 2, 3 and 4 are spare and shall be coded as zero 
               
               
                   
                   
               
            
           
         
       
     
     In addition, information about the access type that indicates the access at which reactivation has occurred or an error or problem has occurred may be added. 
     (Method 3) 
       FIG. 4  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     At step  401 , the terminal has established a PDU session with the UPF to communicate. Here, the PDU session has been established through the 5G RAN; that is, data communication is being performed through the terminal, 5G RAN and UPF. 
     At step  403 , the terminal has established a PDU session with the UPF to communicate. In this case, the PDU session has been established through non-3GPP access, for example, WiFi, trusted WiFi, or non-trusted WiFi; that is, data communication is being performed through the terminal, non-3GPP access and UPF. 
     At step  405 , the terminal transmits a service request to the AMF. Here, the terminal may transmit a service request to the AMF through 3GPP access. In another embodiment, the terminal may transmit a service request to the AMF through non-3GPP access. Here, the status of the multi-access PDU session may be informed to the AMF through a multi-access PDU session status information element. 
       FIG. 4  illustrates a case of executing a service request through non-3GPP access, and illustrates a case where the session can be recovered when the service request is sent through non-3GPP access but the access situation has changed from before. That is, for example, when 70% of the flow has been sent through 3GPP and 30% has been sent through non-3GPP before the service request, and when 80% of the flow is sent through 3GPP and 20% is sent through non-3GPP after the service request, such information may be notified by using this method. 
     In this case, after the service accept, parameters related to the multiple access PDU session may be changed through a PDU session modification command as at steps  417  and  419 , and accordingly, it is possible to adjust the transmission rates or ratios of the flows transmitted for the corresponding PDU session. 
     This multi-access PDU session status information element is configured as shown in Table 21. And, multi-access PDU session status information can be coded and interpreted as shown in Table 22. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 21 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session status |E| 
                 octet 1 
               
               
                 Length of multi access PDU session status contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 22 
               
               
                   
                   
               
             
            
               
                   
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                   
                 PSI(0): 
               
               
                   
                   
                 Bit 1 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 0 
                 indicates that the 5GSM state of the correspoinding  
               
            
           
           
               
               
               
            
               
                   
                   
                 multi access PDU session is multi access PDU 
               
               
                   
                   
                 SESSION INACTIVE 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 1 
                 indicates that the 5GSM state of the correspoinding  
               
            
           
           
               
               
               
            
               
                   
                   
                 multi access PDU session is multi access PDU 
               
               
                   
                   
                 SESSION ACTIVE 
               
               
                   
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                   
                 if the respective octet is included in the information element. 
               
               
                   
                   
               
            
           
         
       
     
     In addition, this multi-access PDU session status information element is an information element included in the service request message as shown in Table 23. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 23 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 Type 
                 Type 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service request  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                   
                 ngKSI 
                 NAS key set  
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 identifier 
                   
                   
                   
               
               
                   
                   
                 9.11.3.32 
                   
                   
                   
               
               
                   
                 Service type 
                 Service type 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.11.3.50 
                   
                   
                   
               
               
                   
                 5G-S-TMSI 
                 5GS mobile  
                 M 
                 LV-E 
                 9 
               
               
                   
                   
                 identity 9.11.3.4 
                   
                   
                   
               
               
                 40 
                 Uplink data status 
                 Uplink data status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.57 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 status 9.11.3.44 
                   
                   
                   
               
               
                 25 
                 Allowed PDU  
                 Allowed PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status  
                   
                   
                   
               
               
                   
                   
                 9.11.3.13 
                   
                   
                   
               
               
                 71 
                 NAS message  
                 NAS message  
                 O 
                 TLV-E 
                 4-n 
               
               
                   
                 container 
                 container 9.11.3.33 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status 
               
               
                   
               
            
           
         
       
     
     At step  407 , the AMF transmits a PDU session update request message to the SMF. 
     At step  409 , the SMF transmits a PDU session update response message to the AMF. 
     At step  411 , the AMF transmits a service accept message to the terminal as shown in Table 24. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 24 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended prtocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 type 9.3 
                   
                   
                   
               
               
                   
                 Spare halt octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5. 
                   
                   
                   
               
               
                   
                 Service accept  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU Session status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.44 
                   
                   
                   
               
               
                 26 
                 PDU session  
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 reactivation result 
                 reactivation  
                   
                   
                   
               
               
                   
                   
                 result 9.11.3.42 
                   
                   
                   
               
               
                 72 
                 PDU session  
                 PDU session  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 reactivation result  
                 reactivation  
                   
                   
                   
               
               
                   
                 error cause 
                 result error cause 
                   
                   
                   
               
               
                   
                   
                 9.11.3.43 
                   
                   
                   
               
               
                 78 
                 EAP message 
                 EAP message 
                 O 
                 TLV-E 
                 7-1503 
               
               
                   
                   
                 9.11.2.2. 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 4-34 
               
               
                   
                 session reactivation  
                 session activation  
                   
                   
                   
               
               
                   
                 result 
                 result 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result error cause 
               
               
                   
               
            
           
         
       
     
     Here, a multi-access PDU session reactivation result may be transmitted to inform information about the result of the multi-access PDU session activation requested in the service request. This information may be transmitted by being included in the multi-access PDU session reactivation result information element as shown in Table 25 included in the service accept message at step  411 . 
     The information element in Table 25 is coded and interpreted as in Table 26. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 25 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 26 
               
               
                   
               
             
            
               
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                 PSI(0): 
               
               
                   
                 Bit 0 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
            
               
                   
                 0 
                 indicates establishment of user-plane resources of  
               
            
           
           
               
               
            
               
                   
                 the multi access PDU session was not allowed in the multi  
               
               
                   
                 acess PDU session reactivation status IE or establishment 
               
               
                   
                 of user-plane resource of the PDU session is successful. 
               
            
           
           
               
               
               
            
               
                   
                 1 
                 indicates establishment of user plane resources of the  
               
            
           
           
               
               
            
               
                   
                 PDU session was requested in the multi access PDU session  
               
               
                   
                 status IE but establishment of user-plane resource of the multi  
               
               
                   
                 access PDU session is either not performed or not successful 
               
               
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                 if the respective octet is included in the information element. 
               
               
                   
               
            
           
         
       
     
     Additionally, at this time, to inform information about an error occurrence together with the result of the multi-access PDU session activation requested in the service request, information about the error may be included in the multi-access PDU session reactivation result error cause information element as shown in Table 27 and transmitted. This multi-access PDU session reactivation result error cause information element may be transmitted by being included in the service accept message at step  411 . 
     Coding and interpretation for Table 27 are shown in Table 28. 
     That is, it is possible to notify various causes (reasons) given in the 5GMM cause information element, such as insufficient resource for a PDU session, insufficient resource for a specific DNN or slice, or insufficient resource for a specific slice. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 27 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result error cause |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result error cause 
                 octet 2 
               
               
                   
                 octet 3 
               
               
                 PDU session ID 
                 octet 4 
               
               
                 cause value 
                 octet 5 
               
               
                 . . . 
                   
               
               
                 PDU session ID 
                 octet 514* 
               
               
                 cause value 
                 octet 515* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 28 
               
               
                   
               
             
            
               
                   
                 PDU session ID is coded same as PDU session ID IE 
               
               
                   
                 The cause value is coded same as second octet of 5GMM cause  
               
               
                   
                 information element 
               
               
                   
               
            
           
         
       
     
     Alternatively, as another embodiment, there may be a method in which the AMF informs the terminal of the result of multiple access PDU session reactivation by utilizing the existing PDU session reactivation result IE (information element). When using the existing PDU session reactivation result IE (information element), an information element notifying the terminal that the AMF supports a multiple access PDU session or multiple access PDU session reactivation may be added. 
     The configuration of such multiple access PDU session or multiple access PDU session reactivation supporting indication IE (information element) is shown in Table 28-1 below, and the interpretation and coding thereof are shown in Table 28-2. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 28-1 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Multiple access PDU session 
                 0 
                 0 
                 0 
                 Multiple Multiple access 
                 octet 1 
               
               
                 supporting indication |E| 
                 Spare 
                 Spare 
                 Spare 
                 PDU session supporting 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 28-2 
               
               
                   
                   
               
             
            
               
                   
                   
                 Multiple access PDU session supporting Indication (octet 1) 
               
               
                   
                   
                 Bit 
               
               
                   
                   
                 1 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 0 
                 Multiple access PDU session is not supported 
               
               
                   
                   
                 1 
                 Multiple access PDU session is supported. 
               
            
           
           
               
               
               
            
               
                   
                   
                 Bits 2, 3 and 4 are spare and shall be coded as zero. 
               
               
                   
                   
               
            
           
         
       
     
     In addition, information about the access type that indicates the access at which reactivation has occurred or an error or problem has occurred may be added. 
     At step  417 , the SMF transmits a PDU session modification command to the terminal. At this time, information related to the multi-access PDU session, for example, parameters related to a multiple access PDU session parameter container may be transmitted, and the multiple access PDU session parameter container may include information such as multiple access PDU session related rules, an IP address and port number of the multi-path TCP (MPTCP) proxy, and a UE link specific address. 
     
       
         
           
               
             
               
                 TABLE 29 
               
             
            
               
                   
               
               
                 PDU session modification command 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format  
                 Length 
               
               
                   
               
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 PDU session ID 
                 PDU session  
                 M 
                 V 
                 1 
               
               
                   
                   
                 Identity 9.4 
                   
                   
                   
               
               
                   
                 PTI 
                 Procedure  
                 M 
                 V 
                 1 
               
               
                   
                   
                 transaction  
                   
                   
                   
               
               
                   
                   
                 identity 9.6 
                   
                   
                   
               
               
                   
                 PDU SESSION  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 MODIFICATION 
                 9.7 
                   
                   
                   
               
               
                   
                 COMMAND  
                   
                   
                   
                   
               
               
                   
                 message identity 
                   
                   
                   
                   
               
               
                 59 
                 5GSM cause 
                 5GSM cause 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.4.2 
                   
                   
                   
               
               
                 2A 
                 Session AMBR 
                 Session-AMBR 
                 O  
                 TLV 
                 8 
               
               
                   
                   
                 9.11.4.14 
                   
                   
                   
               
               
                 56 
                 RQ timer value 
                 GPRS tirne 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.2.3 
                   
                   
                   
               
               
                 8- 
                 Always-on PDU  
                 Always-on PDU  
                 O 
                 TV 
                 1 
               
               
                   
                 session indication 
                 session indication  
                   
                   
                   
               
               
                   
                   
                 9.11.4 3 
                   
                   
                   
               
               
                 7A 
                 Authorized QoS  
                 QoS rules 
                 O 
                 TLV-E  
                 7-65538 
               
               
                   
                 rules 
                 9.11.4.13 
                   
                   
                   
               
               
                 75 
                 Mapped EPS bearer  
                 Mapped EPS bearer  
                 O 
                 TLV-E  
                 7-65538 
               
               
                   
                 contexts 
                 context 9.11.4.8 
                   
                   
                   
               
               
                 79 
                 Authorized QoS  
                 QoS flow  
                 O 
                 TLV-E 
                 6-65538 
               
               
                   
                 flow descriptions 
                 descriptions 
                   
                   
                   
               
               
                   
                   
                 9.11.4.12 
                   
                   
                   
               
               
                 7B 
                 Extended protocol  
                 Extended protocol  
                 O 
                 TLV-E 
                 4-65538 
               
               
                   
                 configuration  
                 configuration  
                   
                   
                   
               
               
                   
                 options 
                 options 9.11.4.6 
                   
                   
                   
               
               
                   
                 Multiple access PDU  
                 Multiple access  
                 O 
                 TLV-E 
                 3-65538 
               
               
                   
                 session parameter  
                 PDU session  
                   
                   
                   
               
               
                   
                 container 
                 parameter container 
               
               
                   
               
            
           
         
       
     
     At step  419 , the terminal transmits a PDU session modification complete message to the SMF. 
     (Method 4) 
       FIG. 5  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     At step  501 , the UE has established a PDU session with the UPF to communicate. Here, the PDU session has been established through the 5G RAN; that is, data communication is being performed through the UE, 5G RAN and UPF. 
     At step  503 , the UE has established a PDU session with the UPF to communicate. In this case, the PDU session has been established through non-3GPP access, for example, WiFi, trusted WiFi, or non-trusted WiFi; that is, data communication is being performed through the UE, non-3GPP access and UPF. 
     At step  505 , the UE transmits a service request to the AMF. Here, the UE may transmit a service request to the AMF through 3GPP access. In another embodiment, the UE may transmit a service request to the AMF through non-3GPP access. Here, the status of the multi-access PDU session may be informed to the AMF through a multi-access PDU session status information element. 
     This multi-access PDU session status information element is configured as shown in Table 31. And, multi-access PDU session status information can be coded and interpreted as shown in Table 32. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 31 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session status |E| 
                 octet 1 
               
               
                 Length of multi access PDU session status contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 32 
               
               
                   
               
             
            
               
                 PSI(x) shall be coded as follows. 
               
               
                 PSI(0): 
               
               
                 Bit 1 of octet 3 is spare and shall be coded as zero 
               
               
                 PSI(1) - PSI(15): 
               
               
                 0 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION INACTIVE 
               
               
                 1 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION ACTIVE 
               
               
                 All bits in octet 5 to 34 are spare and shall be coded as zero, if the respective octets is included in the information 
               
               
                 element 
               
               
                   
               
            
           
         
       
     
     In addition, this multi-access PDU session status information element is an information element included in the service request message as shown in Table 33. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 33 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 Type 
                 Type 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service request  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                   
                 ngKSI 
                 NAS key set  
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 identifier 
                   
                   
                   
               
               
                   
                   
                 9.11.3.32 
                   
                   
                   
               
               
                   
                 Service type 
                 Service type 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.11.3.50 
                   
                   
                   
               
               
                   
                 5G-S-TMSI 
                 5GS mobile  
                 M 
                 LV-E 
                 9 
               
               
                   
                   
                 identity 9.11.3.4 
                   
                   
                   
               
               
                 40 
                 Uplink data status 
                 Uplink data status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.57 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 status 9.11.3.44 
                   
                   
                   
               
               
                 25 
                 Allowed PDU  
                 Allowed PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status  
                   
                   
                   
               
               
                   
                   
                 9.11.3.13 
                   
                   
                   
               
               
                 71 
                 NAS message  
                 NAS message  
                 O 
                 TLV-E 
                 4-n 
               
               
                   
                 container 
                 container 9.11.3.33 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status 
               
               
                   
               
            
           
         
       
     
     At step  511 , the AMF transmits a service accept message to the UE as shown in Table 34. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 34 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended prtocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 type 9.3 
                   
                   
                   
               
               
                   
                 Spare halt octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5. 
                   
                   
                   
               
               
                   
                 Service accept  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU Session status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.44 
                   
                   
                   
               
               
                 26 
                 PDU session  
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 reactivation result 
                 reactivation  
                   
                   
                   
               
               
                   
                   
                 result 9.11.3.42 
                   
                   
                   
               
               
                 72 
                 PDU session  
                 PDU session  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 reactivation result  
                 reactivation  
                   
                   
                   
               
               
                   
                 error cause 
                 result error cause 
                   
                   
                   
               
               
                   
                   
                 9.11.3.43 
                   
                   
                   
               
               
                 78 
                 EAP message 
                 EAP message 
                 O 
                 TLV-E 
                 7-1503 
               
               
                   
                   
                 9.11.2.2. 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 4-34 
               
               
                   
                 session reactivation  
                 session activation  
                   
                   
                   
               
               
                   
                 result 
                 result 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result error cause 
               
               
                   
               
            
           
         
       
     
     Here, a multi-access PDU session reactivation result may be transmitted to inform information about the result of the multi-access PDU session activation requested in the service request. This information may be transmitted by being included in the multi-access PDU session reactivation result information element as shown in Table 35 included in the service accept message at step  511 . 
     The information element in Table 35 is coded and interpreted as in Table 36. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 35 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 36 
               
               
                   
               
             
            
               
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                 PSI(0): 
               
               
                   
                 Bit 0 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
            
               
                   
                 0 
                 indicates establishment of user-plane resources of  
               
            
           
           
               
               
            
               
                   
                 the multi access PDU session was not allowed in the multi  
               
               
                   
                 acess PDU session reactivation status IE or establishment 
               
               
                   
                 of user-plane resource of the PDU session is successful. 
               
            
           
           
               
               
               
            
               
                   
                 1 
                 indicates establishment of user plane resources of the  
               
            
           
           
               
               
            
               
                   
                 PDU session was requested in the multi access PDU session  
               
               
                   
                 status IE but establishment of user-plane resource of the multi  
               
               
                   
                 access PDU session is either not performed or not successful 
               
               
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                 if the respective octet is included in the information element. 
               
               
                   
               
            
           
         
       
     
     Additionally, at this time, to inform information about an error occurrence together with the result of the multi-access PDU session activation requested in the service request, information about the error may be included in the multi-access PDU session reactivation result error cause information element as shown in Table 37 and transmitted. This multi-access PDU session reactivation result error cause information element may be transmitted by being included in the service accept message at step  511 . 
     Coding and interpretation for Table 37 are shown in Table 38. 
     That is, it is possible to notify various causes (reasons) given in the 5GMM cause information element, such as insufficient resource for a PDU session, insufficient resource for a specific DNN or slice, or insufficient resource for a specific slice. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 37 
               
               
                   
               
             
            
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result error cause |E| 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result error cause 
                 octet 2 
               
               
                   
                 octet 3 
               
               
                 PDU session ID 
                 octet 4 
               
               
                 cause value 
                 octet 5 
               
               
                 . . . 
                   
               
               
                 PDU session ID 
                 octet 514* 
               
               
                 cause value 
                 octet 515* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 38 
               
               
                   
               
             
            
               
                   
                 PDU session ID is coded same as PDU session ID IE 
               
               
                   
                 The cause value is coded same as second octet of 5GMM cause  
               
               
                   
                 information element 
               
               
                   
               
            
           
         
       
     
     Alternatively, as another embodiment, there may be a method in which the AMF informs the UE of the result of multiple access PDU session reactivation by utilizing the existing PDU session reactivation result IE (information element). When using the existing PDU session reactivation result IE (information element), an information element notifying the UE that the AMF supports a multiple access PDU session or multiple access PDU session reactivation may be added. 
     The configuration of such multiple access PDU session or multiple access PDU session reactivation supporting indication IE (information element) is shown in Table 39 below, and the interpretation and coding thereof are shown in Table 39-1. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 39 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Multiple access PDU session 
                 0 
                 0 
                 0 
                 Multiple Multiple access 
                 octet 1 
               
               
                 supporting indication IEI 
                 Spare 
                 Spare 
                 Spare 
                 PDU session supporting 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 39-1 
               
               
                   
                   
               
             
            
               
                   
                   
                 Multiple access PDU session supporting Indication (octet 1) 
               
               
                   
                   
                 Bit 
               
               
                   
                   
                 1 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 0 
                 Multiple access PDU session is not supported 
               
               
                   
                   
                 1 
                 Multiple access PDU session is supported. 
               
            
           
           
               
               
               
            
               
                   
                   
                 Bits 2, 3 and 4 are spare and shall be coded as zero. 
               
               
                   
                   
               
            
           
         
       
     
     In addition, information about the access type that indicates the access at which reactivation has occurred or an error or problem has occurred may be added. 
     At step  513 , the AMF transmits a PDU session update request message to the SMF. 
     At step  515 , the SMF transmits a PDU session update response message to the AMF. 
     Unlike  FIGS. 2 to 4 ,  FIG. 5  is an embodiment in which the process of PDU session update request and PDU session update response occurs after the process of service request and service accept. Likewise, an embodiment where the process of PDU session update request and PDU session update response occurs after the process of service request is possible, the process of PDU session update request and PDU session update response may occur in the middle of the process of service request and accept as in  FIGS. 2 to 4 , the process of PDU session update request and PDU session update response may occur after the process of service request and accept as in  FIG. 5 , or the process of PDU session update request and PDU session update response may occur in both cases. 
     (Method 5) 
       FIG. 6  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     At step  601 , the UE has established a PDU session with the UPF to communicate. Here, the PDU session has been established through the 5G RAN; that is, data communication is being performed through the UE, 5G RAN and UPF. 
     At step  603 , the UE has established a PDU session with the UPF to communicate. In this case, the PDU session has been established through non-3GPP access, for example, WiFi, trusted WiFi, or non-trusted WiFi; that is, data communication is being performed through the UE, non-3GPP access and UPF. 
     At step  605 , the UE transmits a service request to the AMF. Here, the UE may transmit a service request to the AMF through 3GPP access. In another embodiment, the UE may transmit a service request to the AMF through non-3GPP access. Here, the status of the multi-access PDU session may be informed to the AMF through a multi-access PDU session status information element. 
     This multi-access PDU session status information element is configured as shown in Table 41. And, multi-access PDU session status information can be coded and interpreted as shown in Table 42. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 41 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session status IEI 
                 octet 1 
               
               
                 Length of multi access PDU session status contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 42 
               
               
                   
               
             
            
               
                 PSI(x) shall be coded as follows. 
               
               
                 PSI(0): 
               
               
                 Bit 1 of octet 3 is spare and shall be coded as zero 
               
               
                 PSI(1) - PSI(15): 
               
               
                 0 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION INACTIVE 
               
               
                 1 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION ACTIVE 
               
               
                 All bits in octet 5 to 34 are spare and shall be coded as zero, if the respective octets is included in the information 
               
               
                 element 
               
               
                   
               
            
           
         
       
     
     In addition, this multi-access PDU session status information element is an information element included in the service request message as shown in Table 43. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 43 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 type 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service request  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                   
                 ngKSI 
                 NAS key set  
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 identifier 
                   
                   
                   
               
               
                   
                   
                 9.11.3.32 
                   
                   
                   
               
               
                   
                 Service type 
                 Service type 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.11.3.50 
                   
                   
                   
               
               
                   
                 5G-S-TMSI 
                 5GS mobile  
                 M 
                 LV-E 
                 9 
               
               
                   
                   
                 identity 9.11.3.4 
                   
                   
                   
               
               
                 40 
                 Uplink data status 
                 Uplink data status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.57 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 status 9.11.3.44 
                   
                   
                   
               
               
                 25 
                 Allowed PDU  
                 Allowed PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status  
                   
                   
                   
               
               
                   
                   
                 9.11.3.13 
                   
                   
                   
               
               
                 71 
                 NAS message  
                 NAS message  
                 O 
                 TLV-E 
                 4-n 
               
               
                   
                 container 
                 container 9.11.3.33 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status 
               
               
                   
               
            
           
         
       
     
     At step  607 , the AMF transmits a PDU session update request message to the SMF. 
     At step  609 , the SMF transmits a PDU session update response message to the AMF. 
     At step  611 , the AMF transmits a service accept message to the UE as shown in Table 44. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 44 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended prtocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header  
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 type 9.3 
                   
                   
                   
               
               
                   
                 Spare halt octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5. 
                   
                   
                   
               
               
                   
                 Service accept  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU Session status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.44 
                   
                   
                   
               
               
                 26 
                 PDU session  
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 reactivation result 
                 reactivation  
                   
                   
                   
               
               
                   
                   
                 result 9.11.3.42 
                   
                   
                   
               
               
                 72 
                 PDU session  
                 PDU session  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 reactivation result  
                 reactivation  
                   
                   
                   
               
               
                   
                 error cause 
                 result error cause 
                   
                   
                   
               
               
                   
                   
                 9.11.3.43 
                   
                   
                   
               
               
                 78 
                 EAP message 
                 EAP message 
                 O 
                 TLV-E 
                 7-1503 
               
               
                   
                   
                 9.11.2.2. 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 4-34 
               
               
                   
                 session reactivation  
                 session activation  
                   
                   
                   
               
               
                   
                 result 
                 result 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result error cause 
               
               
                   
               
            
           
         
       
     
     Here, a multi-access PDU session reactivation result may be transmitted to inform information about the result of the multi-access PDU session activation requested in the service request. This information may be transmitted by being included in the multi-access PDU session reactivation result information element as shown in Table 45 included in the service accept message at step  611 . 
     The information element in Table 45 is coded and interpreted as in Table 46. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 45 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result IEI 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 46 
               
               
                   
               
             
            
               
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                 PSI(0): 
               
               
                   
                 Bit 0 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
            
               
                   
                 0 
                 indicates establishment of user-plane resources of  
               
            
           
           
               
               
            
               
                   
                 the multi access PDU session was not allowed in the multi  
               
               
                   
                 acess PDU session reactivation status IE or establishment 
               
               
                   
                 of user-plane resource of the PDU session is successful. 
               
            
           
           
               
               
               
            
               
                   
                 1 
                 indicates establishment of user plane resources of the  
               
            
           
           
               
               
            
               
                   
                 PDU session was requested in the multi access PDU session  
               
               
                   
                 status IE but establishment of user-plane resource of the multi  
               
               
                   
                 access PDU session is either not performed or not successful 
               
               
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                 if the respective octet is included in the information element. 
               
               
                   
               
            
           
         
       
     
     Additionally, at this time, to inform information about an error occurrence together with the result of the multi-access PDU session activation requested in the service request, information about the error may be included in the multi-access PDU session reactivation result error cause information element as shown in Table 47 and transmitted. This multi-access PDU session reactivation result error cause information element may be transmitted by being included in the service accept message at step  611 . 
     Coding and interpretation for Table 47 are shown in Table 48. 
     That is, it is possible to notify various causes (reasons) given in the 5GMM cause information element, such as insufficient resource for a PDU session, insufficient resource for a specific DNN or slice, or insufficient resource for a specific slice. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 47 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result error cause IEI 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result error cause 
                 octet 2 
               
               
                   
                 octet 3 
               
               
                 PDU session ID 
                 octet 4 
               
               
                 cause value 
                 octet 5 
               
               
                 . . . 
                   
               
               
                 PDU session ID 
                 octet 514* 
               
               
                 cause value 
                 octet 515* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 48 
               
               
                   
               
             
            
               
                   
                 PDU session ID is coded same as PDU session ID IE 
               
               
                   
                 The cause value is coded same as second octet of 5GMM cause  
               
               
                   
                 information element 
               
               
                   
               
            
           
         
       
     
     Alternatively, as another embodiment, there may be a method in which the AMF informs the UE of the result of multiple access PDU session reactivation by utilizing the existing PDU session reactivation result IE (information element). When using the existing PDU session reactivation result IE (information element), an information element notifying the UE that the AMF supports a multiple access PDU session or multiple access PDU session reactivation may be added. 
     The configuration of such multiple access PDU session or multiple access PDU session reactivation supporting indication IE (information element) is shown in Table 48-1 below, and the interpretation and coding thereof are shown in Table 48-2. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 48-1 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Multiple access PDU session 
                 0 
                 0 
                 0 
                 Multiple Multiple access  
                 octet 1 
               
               
                 supporting indication IEI 
                 Spare 
                 Spare 
                 Spare 
                 PDU session supporting 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 48-2 
               
               
                   
                   
               
             
            
               
                   
                   
                 Multiple access PDU session supporting Indication (octet 1) 
               
               
                   
                   
                 Bit 
               
               
                   
                   
                 1 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 0 
                 Multiple access PDU session is not supported 
               
               
                   
                   
                 1 
                 Multiple access PDU session is supported. 
               
            
           
           
               
               
               
            
               
                   
                   
                 Bits 2, 3 and 4 are spare and shall be coded as zero 
               
               
                   
                   
               
            
           
         
       
     
     In addition, information about the access type that indicates the access at which reactivation has occurred or an error or problem has occurred may be added. 
     At step  617 , the SMF transmits a PDU session modification command to the UE. At this time, information related to the multi-access PDU session, for example, parameters related to a multiple access PDU session parameter container may be transmitted, and the multiple access PDU session parameter container may include information such as multiple access PDU session related rules, an IP address and port number of the multi-path TCP (MPTCP) proxy, and a UE link specific address. 
     
       
         
           
               
             
               
                 TABLE 49 
               
             
            
               
                   
               
               
                 PDU session modification command 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format  
                 Length 
               
               
                   
               
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 PDU session ID 
                 PDU session  
                 M 
                 V 
                 1 
               
               
                   
                   
                 Identity 9.4 
                   
                   
                   
               
               
                   
                 PTI 
                 Procedure  
                 M 
                 V 
                 1 
               
               
                   
                   
                 transaction  
                   
                   
                   
               
               
                   
                   
                 identity 9.6 
                   
                   
                   
               
               
                   
                 PDU SESSION  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 MODIFICATION 
                 9.7 
                   
                   
                   
               
               
                   
                 COMMAND  
                   
                   
                   
                   
               
               
                   
                 message identity 
                   
                   
                   
                   
               
               
                 59 
                 5GSM cause 
                 5GSM cause 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.4.2 
                   
                   
                   
               
               
                 2A 
                 Session AMBR 
                 Session-AMBR 
                 O  
                 TLV 
                 8 
               
               
                   
                   
                 9.11.4.14 
                   
                   
                   
               
               
                 56 
                 RQ timer value 
                 GPRS tirne 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.2.3 
                   
                   
                   
               
               
                 8- 
                 Always-on PDU  
                 Always-on PDU  
                 O 
                 TV 
                 1 
               
               
                   
                 session indication 
                 session indication  
                   
                   
                   
               
               
                   
                   
                 9.11.4 3 
                   
                   
                   
               
               
                 7A 
                 Authorized QoS  
                 QoS rules 
                 O 
                 TLV-E  
                 7-65538 
               
               
                   
                 rules 
                 9.11.4.13 
                   
                   
                   
               
               
                 75 
                 Mapped EPS bearer  
                 Mapped EPS bearer  
                 O 
                 TLV-E  
                 7-65538 
               
               
                   
                 contexts 
                 context 9.11.4.8 
                   
                   
                   
               
               
                 79 
                 Authorized QoS  
                 QoS flow  
                 O 
                 TLV-E 
                 6-65538 
               
               
                   
                 flow descriptions 
                 descriptions 
                   
                   
                   
               
               
                   
                   
                 9.11.4.12 
                   
                   
                   
               
               
                 7B 
                 Extended protocol  
                 Extended protocol  
                 O 
                 TLV-E 
                 4-65538 
               
               
                   
                 configuration  
                 configuration  
                   
                   
                   
               
               
                   
                 options 
                 options 9.11.4.6 
                   
                   
                   
               
               
                   
                 Multiple access PDU  
                 Multiple access  
                 O 
                 TLV-E 
                 3-65538 
               
               
                   
                 session parameter  
                 PDU session  
                   
                   
                   
               
               
                   
                 container 
                 parameter container 
               
               
                   
               
            
           
         
       
     
     At step  619 , the UE transmits a PDU session modification complete message to the SMF. 
     (Method 6) 
       FIG. 7  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     At step  701 , the UE has established a PDU session with the UPF to communicate. Here, the PDU session has been established through the 5G RAN; that is, data communication is being performed through the UE, 5G RAN and UPF. 
     At step  703 , the UE has established a PDU session with the UPF to communicate. In this case, the PDU session has been established through non-3GPP access, for example, WiFi, trusted WiFi, or non-trusted WiFi; that is, data communication is being performed through the UE, non-3GPP access and UPF. 
     At step  717 , the SMF transmits a PDU session modification command to the UE. At this time, information related to the multi-access PDU session, for example, parameters related to a multiple access PDU session parameter container may be transmitted, and the multiple access PDU session parameter container may include information such as multiple access PDU session related rules, an IP address and port number of the multi-path TCP (MPTCP) proxy, and a UE link specific address. 
     
       
         
           
               
             
               
                 TABLE 59 
               
             
            
               
                   
               
               
                 PDU session modification command 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format  
                 Length 
               
               
                   
               
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 PDU session ID 
                 PDU session  
                 M 
                 V 
                 1 
               
               
                   
                   
                 Identity 9.4 
                   
                   
                   
               
               
                   
                 PTI 
                 Procedure  
                 M 
                 V 
                 1 
               
               
                   
                   
                 transaction  
                   
                   
                   
               
               
                   
                   
                 identity 9.6 
                   
                   
                   
               
               
                   
                 PDU SESSION  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 MODIFICATION 
                 9.7 
                   
                   
                   
               
               
                   
                 COMMAND  
                   
                   
                   
                   
               
               
                   
                 message identity 
                   
                   
                   
                   
               
               
                 59 
                 5GSM cause 
                 5GSM cause 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.4.2 
                   
                   
                   
               
               
                 2A 
                 Session AMBR 
                 Session-AMBR 
                 O  
                 TLV 
                 8 
               
               
                   
                   
                 9.11.4.14 
                   
                   
                   
               
               
                 56 
                 RQ timer value 
                 GPRS tirne 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.2.3 
                   
                   
                   
               
               
                 8- 
                 Always-on PDU  
                 Always-on PDU  
                 O 
                 TV 
                 1 
               
               
                   
                 session indication 
                 session indication  
                   
                   
                   
               
               
                   
                   
                 9.11.4 3 
                   
                   
                   
               
               
                 7A 
                 Authorized QoS  
                 QoS rules 
                 O 
                 TLV-E  
                 7-65538 
               
               
                   
                 rules 
                 9.11.4.13 
                   
                   
                   
               
               
                 75 
                 Mapped EPS bearer  
                 Mapped EPS bearer  
                 O 
                 TLV-E  
                 7-65538 
               
               
                   
                 contexts 
                 context 9.11.4.8 
                   
                   
                   
               
               
                 79 
                 Authorized QoS  
                 QoS flow  
                 O 
                 TLV-E 
                 6-65538 
               
               
                   
                 flow descriptions 
                 descriptions 
                   
                   
                   
               
               
                   
                   
                 9.11.4.12 
                   
                   
                   
               
               
                 7B 
                 Extended protocol  
                 Extended protocol  
                 O 
                 TLV-E 
                 4-65538 
               
               
                   
                 configuration  
                 configuration  
                   
                   
                   
               
               
                   
                 options 
                 options 9.11.4.6 
                   
                   
                   
               
               
                   
                 Multiple access PDU  
                 Multiple access  
                 O 
                 TLV-E 
                 3-65538 
               
               
                   
                 session parameter  
                 PDU session  
                   
                   
                   
               
               
                   
                 container 
                 parameter container 
               
               
                   
               
            
           
         
       
     
     At step  719 , the UE transmits a PDU session modification complete message to the SMF. 
       FIG. 8  is a diagram illustrating the structure of a terminal according to an embodiment of the disclosure. 
     With reference to  FIG. 8 , the terminal may include a transceiver  810 , a controller  820 , and a storage  830 . In the disclosure, the controller may be defined as a circuit, an application-specific integrated circuit, or at least one processor. 
     The transceiver  810  may transmit and receive signals to and from other network entities. The transceiver  810  may receive system information from, for example, a base station, and may receive a synchronization signal or a reference signal. 
     The controller  820  may control the overall operation of the terminal according to the embodiments proposed in the disclosure. For example, the controller  820  may control signal flows between blocks to perform operations according to the flowcharts depicted in  FIGS. 2 to 7  and  FIG. 10 . 
     The storage  830  may store at least one of information transmitted and received through the transceiver  810  or information generated through the controller  820 . 
       FIG. 9  is a diagram illustrating the structure of a network entity according to an embodiment of the present disclosure. The network entity shown in  FIG. 9  may be one of the entities  103  to  171  in the network shown in  FIG. 1 . 
     With reference to  FIG. 8 , the network entity may include a transceiver  910 , a controller  920 , and a storage  930 . In the disclosure, the controller may be defined as a circuit, an application specific integrated circuit, or at least one processor. 
     The transceiver  910  may transmit and receive signals to and from a terminal or other network entity. 
     The controller  920  may control the overall operation of the network entity according to the embodiments proposed in the disclosure. For example, the controller  920  may control signal flows between blocks to perform operations according to the flowcharts depicted in  FIGS. 2 to 7  and  FIG. 10 . 
     The storage  930  may store at least one of information transmitted and received through the transceiver  910  or information generated through the controller  920 . 
     (Method 8) 
       FIG. 10  illustrates an embodiment of a communication procedure and method for mobility management and session activation through NAS protocols in a 5G network environment according to an embodiment of the disclosure. 
     At step  1001 , the UE has established a PDU session with the UPF to communicate. Here, the PDU session has been established through the 5G RAN; that is, data communication is being performed through the UE, 5G RAN and UPF. 
     At step  1003 , the UE has established a PDU session with the UPF to communicate. In this case, the PDU session has been established through non-3GPP access, for example, WiFi, trusted WiFi, or non-trusted WiFi; that is, data communication is being performed through the UE, non-3GPP access and UPF. 
     Step  1005  and step  1006  below correspond to a situation that may occur when one or both of 3GPP access and non-3GPP access are not active and the UE is not in the connected state as to the corresponding access, and both or one of step  1005  and step  1006  may be performed to reactivate the user plane of the multiple access PDU session for the non-active access. 
     At step  1005 , the UE transmits a service request to the AMF. Here, the UE may transmit a service request to the AMF through 3GPP access. 
     Here, in one embodiment, the status of the multi-access PDU session may be informed to the AMF through a multi-access PDU session status information element. 
     In this case, in another embodiment, whether the PDU session identified by the PDU session identity is active may be notified through the PDU session status information element. That is, when the UE has released the multi-access (MA) PDU session for the corresponding access (here, 5G RAN access at step  1005 ), it may notify the AMF of whether the MA PDU session has been released through the PDU session status information element of the service request message; the AMF may receive this and notify the SMF to release the network resource corresponding to the identity of the multi access (MA) PDU session. 
     At this time, in another embodiment, the uplink data status may be used to notify that uplink data associated with the multiple access (MA) PDU session, that is, the corresponding MA PDU session identity is pending. 
     Additionally, in one embodiment, as a case of executing a service request through 3GPP access, a case is illustrated where the session can be recovered when the service request is sent through 3GPP access but the access situation has changed from before. That is, for example, when 70% of the flow has been sent through 3GPP and 30% has been sent through non-3GPP before the service request, and when 80% of the flow is sent through 3GPP and 20% is sent through non-3GPP after the service request, such information may be notified by using this method. 
     In such a case, after the service accept, parameters related to the multiple access PDU session may be changed through a PDU session modification command as at steps  1017  and  1019 , and accordingly, it is possible to adjust the transmission rates or ratios of the flows transmitted for the corresponding PDU session. 
     Meanwhile, in one embodiment, the multi-access PDU session status information element is configured as shown in Table 61. And, multi-access PDU session status information can be coded and interpreted as shown in Table 62. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 61 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session status IEI 
                 octet 1 
               
               
                 Length of multi access PDU session status contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 62 
               
               
                   
               
             
            
               
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                 PSI(0): 
               
               
                   
                 Bit 1 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
            
               
                   
                 0 
                 indicates that the 5GSM state of the correspoinding  
               
            
           
           
               
               
            
               
                   
                 multi access PDU session is multi access PDU 
               
               
                   
                 SESSION INACTIVE 
               
            
           
           
               
               
               
            
               
                   
                 1 
                 indicates that the 5GSM state of the correspoinding  
               
            
           
           
               
               
            
               
                   
                 multi access PDU session is multi access PDU 
               
               
                   
                 SESSION ACTIVE 
               
               
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                 if the respective octet is included in the information element. 
               
               
                   
               
            
           
         
       
     
     In addition, this multi-access PDU session status information element is an information element included in the service request message as shown in Table 63. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 63 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security Header  
                 Security Header  
                 M 
                 V 
                 1/2 
               
               
                   
                 Type 
                 Type 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service request  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                   
                 ngKSI 
                 NAS key set  
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 identifier 
                   
                   
                   
               
               
                   
                   
                 9.11.3.32 
                   
                   
                   
               
               
                   
                 Service type 
                 Service type 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.11.3.50 
                   
                   
                   
               
               
                   
                 5G-S-TMSI 
                 5GS mobile  
                 M 
                 LV-E 
                 9 
               
               
                   
                   
                 identity 9.11.3.4 
                   
                   
                   
               
               
                 40 
                 Uplink data status 
                 Uplink data status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.57 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 status 9.11.3.44 
                   
                   
                   
               
               
                 25 
                 Allowed PDU  
                 Allowed PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status  
                   
                   
                   
               
               
                   
                   
                 9.11.3.13 
                   
                   
                   
               
               
                 71 
                 NAS message  
                 NAS message  
                 O 
                 TLV-E 
                 4-n 
               
               
                   
                 container 
                 container 9.11.3.33 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status 
               
               
                   
               
            
           
         
       
     
     At step  1006 , the UE transmits a service request message to the AMF. Here, the UE may transmit a service request message to the AMF through non-3GPP access. 
     Here, the status of the multi-access PDU session may be informed to the AMF through a multi-access PDU session status information element. 
     In this case, in another embodiment, whether the PDU session identified by the PDU session identity is active may be notified through the PDU session status information element. That is, when the UE has released the multi-access (MA) PDU session for the corresponding access (here, non-3GPP access at step  1006 ), it may notify the AMF of whether the MA PDU session has been released through the PDU session status information element; the AMF may receive this and notify the SMF to release the network resource corresponding to the identity of the multi access (MA) PDU session. 
     At this time, in another embodiment, the uplink data status may be used to notify that uplink data associated with the corresponding MA PDU session identity is pending. 
     Step  1006  is a case of executing a service request through non-3GPP access, and illustrates a case where the session can be recovered when the service request is sent through non-3GPP access but the access situation has changed from before. That is, for example, when 70% of the flow has been sent through 3GPP and 30% has been sent through non-3GPP before the service request, and when 80% of the flow is sent through 3GPP and 20% is sent through non-3GPP after the service request, such information may be notified by using this method. 
     In this case, after the service accept, parameters related to the multiple access PDU session may be changed through a PDU session modification command as at steps  1017  and  1019 , and accordingly, it is possible to adjust the transmission rates or ratios of the flows transmitted for the corresponding PDU session. 
     Meanwhile, in one embodiment, the multi-access PDU session status information element is configured as shown in Table 61-2. And, multi-access PDU session status information can be coded and interpreted as shown in Table 62-2. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 61-2 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session status IEI 
                 octet 1 
               
               
                 Length of multi access PDU session status contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14)  
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 62-2 
               
               
                   
               
             
            
               
                 PSI(x) shall be coded as follows. 
               
               
                 PSI(0): 
               
               
                 Bit 1 of octet 3 is spare and shall be coded as zero 
               
               
                 PSI(1) - PSI(15): 
               
               
                 0 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION INACTIVE 
               
               
                 1 indicates that the 5GSM state of the corresponding multi access PDU session is multi access PDU 
               
               
                 SESSION ACTIVE 
               
               
                 All bits in octet 5 to 34 are spare and shall be coded as zero, if the respective octets is included in the information 
               
               
                 element 
               
               
                   
               
            
           
         
       
     
     In addition, this multi-access PDU session status information element is an information element included in the service request message as shown in Table 63-2. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 63-2 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security Header  
                 Security Header  
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 type 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half octet 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service request  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                   
                 ngKSI 
                 NAS key set  
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 identifier 
                   
                   
                   
               
               
                   
                   
                 9.11.3.32 
                   
                   
                   
               
               
                   
                 Service type 
                 Service type 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.11.3.50 
                   
                   
                   
               
               
                   
                 5G-S-TMSI 
                 5GS mobile  
                 M 
                 LV-E 
                 9 
               
               
                   
                   
                 identity 9.11.3.4 
                   
                   
                   
               
               
                 40 
                 Uplink data status 
                 Uplink data status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.57 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session  
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 status 9.11.3.44 
                   
                   
                   
               
               
                 25 
                 Allowed PDU  
                 Allowed PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status  
                   
                   
                   
               
               
                   
                   
                 9.11.3.13 
                   
                   
                   
               
               
                 71 
                 NAS message  
                 NAS message  
                 O 
                 TLV-E 
                 4-n 
               
               
                   
                 container 
                 container 9.11.3.33 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV 
                 4-34 
               
               
                   
                 session status 
                 session status 
               
               
                   
               
            
           
         
       
     
     At step  1007 , the AMF transmits a PDU session update request message to the SMF. 
     At step  1009 , the SMF transmits a PDU session update response message to the AMF. 
     Step  1011  or step  1013  below corresponds to a situation that may occur when one or both of 3GPP access and non-3GPP access are not active and the UE is not in the connected state as to the corresponding access, and both or one of step  1011  and step  1013  may be performed to reactivate the user plane of the multiple access PDU session for the non-active access. 
     At step  1011 , the AMF transmits a service accept message to the UE as shown in Table 64. 
     The corresponding process may occur through 3GPP access. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 64 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header type 
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half ocret 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service accept  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.44 
                   
                   
                   
               
               
                 26 
                 PDU session  
                 PDU session  
                 O  
                 TLV 
                 4-34 
               
               
                   
                 reactivation result 
                 reactivation result  
                   
                   
                   
               
               
                   
                   
                 9.11.3.42 
                   
                   
                   
               
               
                 72 
                 PDU session  
                 PDU session  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 reactivation  
                 reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result cause 
                   
                   
                   
               
               
                   
                   
                 9.11.3.43 
                   
                   
                   
               
               
                 78 
                 EAP message 
                 EAP message 
                 O 
                 TLV-E 
                 7-1503 
               
               
                   
                   
                 9.11.2.2 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 4-34 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result 
                 result 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDI  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result error cause 
               
               
                   
               
            
           
         
       
     
     In this case, in one embodiment, when the AMF informs the UE that the PDU session for the corresponding multiple access (MA) PDU session identity is inactive through the PDU session status information element, the UE may release the corresponding PDU session. 
     Here, a multi-access PDU session reactivation result may be transmitted to inform information about the result of the multi-access PDU session activation requested in the service request. This information may be transmitted by being included in the multi-access PDU session reactivation result information element as shown in Table 65 included in the service accept message at step  1011 . 
     The information element in Table 65 is coded and interpreted as in Table 66. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 65 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result IEI 
                 octet 1 
               
               
                 Length of multi access PDU sesson reactivation result contents  
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 66 
               
               
                   
               
             
            
               
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                 PSI(0): 
               
               
                   
                 Bit 0 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
            
               
                   
                 0 
                 indicates establishment of user-plane resources of  
               
            
           
           
               
               
            
               
                   
                 the multi access PDU session was not allowed in the multi  
               
               
                   
                 acess PDU session reactivation status IE or establishment 
               
               
                   
                 of user-plane resource of the PDU session is successful. 
               
            
           
           
               
               
               
            
               
                   
                 1 
                 indicates establishment of user plane resources of the  
               
            
           
           
               
               
            
               
                   
                 PDU session was requested in the multi access PDU session  
               
               
                   
                 status IE but establishment of user-plane resource of the multi  
               
               
                   
                 access PDU session is either not performed or not successful 
               
               
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                 if the respective octet is included in the information element 
               
               
                   
               
            
           
         
       
     
     Additionally, at this time, to inform information about an error occurrence together with the result of the multi-access PDU session activation requested in the service request, information about the error may be transmitted by being included in the multi-access PDU session reactivation result error cause information element as shown in Table 67. This multi-access PDU session reactivation result error cause information element may be transmitted by being included in the service accept message at step  1011 . 
     Coding and interpretation for Table 67 are shown in Table 68. 
     That is, it is possible to notify various causes (reasons) given in the 5GMM cause information element, such as insufficient resource for a PDU session, insufficient resource for a specific DNN or slice, or insufficient resource for a specific slice. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 67 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result error cause  
                 octet 1 
               
               
                 IEI 
                   
               
               
                 Length of multi access PDU session reactivation result  
                 octet 2 
               
               
                 error cause 
                 octet 3 
               
               
                 PDU session ID 
                 octet 4 
               
               
                 cause value 
                 octet 5 
               
               
                 PDU session ID octet 514* 
                   
               
               
                 cause value 
                 octet 515* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                   
                 PDU session ID is coded same as PDU session ID IE 
               
               
                   
                   
                 The cause calue is coded same as second octet of 5GMM  
               
               
                   
                   
                 cause information element 
               
               
                   
                   
               
            
           
         
       
     
     Alternatively, as another embodiment, there may be a method in which the AMF informs the UE of the result of multiple access PDU session reactivation for the corresponding access by utilizing a PDU session reactivation result IE (information element) included in the existing service accept message. When using the existing PDU session reactivation result IE (information element), an information element notifying the UE that the AMF supports a multiple access PDU session or multiple access PDU session reactivation may be added. 
     The configuration of such multiple access PDU session or multiple access PDU session reactivation supporting indication IE (information element) is shown in Table 68-1 below, and the interpretation and coding thereof are shown in Table 68-2. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 68-1 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Multiple access PDU session 
                 0 
                 0 
                 0 
                 Multiple Multiple access 
                 octet 1 
               
               
                 supporting indication IEI 
                 Spare 
                 Spare 
                 Spare 
                 PDU session supporting 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                   
                 TABLE 68-2 
               
               
                   
                   
               
             
            
               
                   
                 Multiple access PDU session supporting Indication (octet 1) 
               
               
                   
                 Bit 
               
               
                   
                 1 
               
            
           
           
               
               
               
            
               
                   
                 0 
                 Multiple access PDU session is not supported 
               
               
                   
                 1 
                 Multiple access PDU session is supported 
               
            
           
           
               
               
            
               
                   
                 Bits 2. 3 and 4 are spare and shall be coded as zero. 
               
               
                   
                   
               
            
           
         
       
     
     In addition, information about the access type that indicates the access at which reactivation has occurred or an error or problem has occurred may be added. 
     This access type is information on whether 3GPP access or non-3GPP access. 
     At step  1013 , the AMF transmits a service accept message to the UE as shown in Table 64-3. 
     This process may occur through non-3GPP access. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 64-3 
               
               
                   
               
               
                   
                 Information  
                   
                 Pres- 
                   
                   
               
               
                 IEI 
                 Element 
                 Type/Reference 
                 ence 
                 Format 
                 Length 
               
               
                   
               
             
            
               
                   
                 Extended protocol  
                 Extended protocol  
                 M 
                 V 
                 1 
               
               
                   
                 discriminator 
                 discriminator 9.2 
                   
                   
                   
               
               
                   
                 Security header  
                 Security header type 
                 M 
                 V 
                 1/2 
               
               
                   
                 type 
                 9.3 
                   
                   
                   
               
               
                   
                 Spare half octet 
                 Spare half ocret 
                 M 
                 V 
                 1/2 
               
               
                   
                   
                 9.5 
                   
                   
                   
               
               
                   
                 Service accept  
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 message identity 
                 9.7 
                   
                   
                   
               
               
                 50 
                 PDU session status 
                 PDU session status 
                 O 
                 TLV 
                 4-34 
               
               
                   
                   
                 9.11.3.44 
                   
                   
                   
               
               
                 26 
                 PDU session  
                 PDU session  
                 O  
                 TLV 
                 4-34 
               
               
                   
                 reactivation result 
                 reactivation result  
                   
                   
                   
               
               
                   
                   
                 9.11.3.42 
                   
                   
                   
               
               
                 72 
                 PDU session  
                 PDU session  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 reactivation  
                 reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result cause 
                   
                   
                   
               
               
                   
                   
                 9.11.3.43 
                   
                   
                   
               
               
                 78 
                 EAP message 
                 EAP message 
                 O 
                 TLV-E 
                 7-1503 
               
               
                   
                   
                 9.11.2.2 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDU  
                 O 
                 TLV-E 
                 4-34 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result 
                 result 
                   
                   
                   
               
               
                   
                 Multi access PDU  
                 Multi access PDI  
                 O 
                 TLV-E 
                 5-515 
               
               
                   
                 session reactivation  
                 session reactivation  
                   
                   
                   
               
               
                   
                 result error cause 
                 result error cause 
               
               
                   
               
            
           
         
       
     
     Here, in one embodiment, when the AMF informs the UE that the PDU session for the corresponding multiple access (MA) PDU session identity is inactive through the PDU session status information element, the UE may release the corresponding PDU session. 
     Here, a multi-access PDU session reactivation result may be transmitted to inform information about the result of the multi-access PDU session activation requested in the service request. This information may be transmitted by being included in the multi-access PDU session reactivation result information element as shown in Table 65-3 included in the service accept message at step  1013 . 
     The information element in Table 65-3 is coded and interpreted as in Table 66. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 65-3 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result IEI 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result contents 
                 octet 2 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 3 
               
               
                 (7) 
                 (6) 
                 (5) 
                 (4) 
                 (3) 
                 (2) 
                 (1) 
                 (0) 
                   
               
               
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 PSI 
                 octet 4 
               
               
                 (15) 
                 (14) 
                 (13) 
                 (12) 
                 (11) 
                 (10) 
                 (9) 
                 (8) 
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                   
               
            
           
           
               
               
            
               
                 spare 
                 octet 5*-34* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 66-3 
               
               
                   
               
             
            
               
                   
                 PSI(x) shall be coded as follows: 
               
               
                   
                 PSI(0): 
               
               
                   
                 Bit 0 of octet 3 is spare and shall he coded as zero. 
               
               
                   
                 PSI(1)-PSI(15): 
               
            
           
           
               
               
               
            
               
                   
                 0 
                 indicates establishment of user-plane resources of  
               
            
           
           
               
               
            
               
                   
                 the multi access PDU session was not allowed in the multi  
               
               
                   
                 acess PDU session reactivation status IE or establishment 
               
               
                   
                 of user-plane resource of the PDU session is successful. 
               
            
           
           
               
               
               
            
               
                   
                 1 
                 indicates establishment of user plane resources of the  
               
            
           
           
               
               
            
               
                   
                 PDU session was requested in the multi access PDU session  
               
               
                   
                 status IE but establishment of user-plane resource of the multi  
               
               
                   
                 access PDU session is either not performed or not successful 
               
               
                   
                 All bits in octet 5 to 34 are spare and shall be coded as zero,  
               
               
                   
                 if the respective octet is included in the information element 
               
               
                   
               
            
           
         
       
     
     Additionally, at this time, to inform information about an error occurrence together with the result of the multi-access PDU session activation requested in the service request, information about the error may be transmitted by being included in the multi-access PDU session reactivation result error cause information element as shown in Table 67-3. This multi-access PDU session reactivation result error cause information element may be transmitted by being included in the service accept message at step  1013 . 
     Coding and interpretation for Table 67-3 are shown in Table 68-3. 
     That is, it is possible to notify various causes (reasons) given in the 5GMM cause information element, such as insufficient resource for a PDU session, insufficient resource for a specific DNN or slice, or insufficient resource for a specific slice. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 67-3 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4  
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Multi access PDU session reactivation result error cause IEI 
                 octet 1 
               
               
                 Length of multi access PDU session reactivation result error cause 
                 octet 2 
               
               
                   
                 octet 3 
               
               
                 PDU session ID 
                 octet 4 
               
               
                 cause value 
                 octet 5 
               
               
                 PDU session ID 
                 octet 514* 
               
               
                 cause value 
                 octet 515* 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 68-3 
               
               
                   
               
             
            
               
                   
                 PDU session ID is coded same as PDU session ID IE  
               
               
                   
                 The cause value is coded same as second octet of 5GMM cause  
               
               
                   
                 information element 
               
               
                   
               
            
           
         
       
     
     Alternatively, as another embodiment, there may be a method in which the AMF informs the UE of the result of multiple access PDU session reactivation for the corresponding access by utilizing a PDU session reactivation result IE (information element) included in the existing service accept message. When using the existing PDU session reactivation result IE (information element), an information element notifying the UE that the AMF supports a multiple access PDU session or multiple access PDU session reactivation may be added. 
     The configuration of such multiple access PDU session or multiple access PDU session reactivation supporting indication IE (information element) is shown in Table 68-11 below, and the interpretation and coding thereof are shown in Table 68-12. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 68-11 
               
               
                   
               
               
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Multiple access PDU session 
                 0 
                 0 
                 0 
                 Multiple Multiple access 
                 octet 1 
               
               
                 supporting indication IEI 
                 Spare 
                 Spare 
                 Spare 
                 PDU session supporting 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 68-12 
               
               
                   
               
               
                 Multiple access PDU session supporting Indication (octet 1) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Bit 1 
                   
               
               
                   
                 0 
                 Multiple access PDU session is not supported 
               
               
                   
                 1 
                 Multiple access PDU session is supported 
               
            
           
           
               
               
            
               
                   
                 Bits 2, 3 and 4 are spare and shall be coded as zero 
               
               
                   
                   
               
            
           
         
       
     
     In addition, information about the access type that indicates the access at which reactivation has occurred or an error or problem has occurred may be added. 
     This access type is information on whether 3GPP access or non-3GPP access. 
     At step  1017 , the SMF transmits a PDU session modification command to the UE. At this time, information related to the multi-access PDU session, for example, parameters related to a multiple access PDU session parameter container may be transmitted, and the multiple access PDU session parameter container may include information such as multiple access PDU session related rules, an IP address and port number of the multi-path TCP (MPTCP) proxy, and a UE link specific address. 
     Meanwhile, in one embodiment, when a GBR QoS flow needs to be transferred from one access (source access) to another target access, the PDU session modification command may include a process of creating or modifying a QoS flow. 
     Also, in one embodiment, a rule related to the multiple access PDU session may be changed. In such a change, for the rule included in the PDU session modification command, information related to the multiple access PDU session, for example, a parameter related to a multiple access PDU session parameter container may be transmitted; the multiple access PDU session parameter container may include information such as multiple access PDU session related rules, an IP address and port number of the multi-path TCP (MPTCP) proxy, and a UE link specific address. 
     In one embodiment, while the UE and the UPF are in communication, the UPF may determine that GBR traffic cannot be transmitted through the current access, that is, 3GPP or non-3GPP. This determination may also be made by the UPF having receiving a report that access is not available from the UE. In such a case, the UPF notifies the SMF that GBR traffic cannot be transmitted in the current access by including the QFI of the GBR QoS flow. Then, the SMF receiving this notification may transfer the GBR QoS flow from the current source access to the target access. That is, the SMF may switch the GBR QoS flow in the current source access to the target access by sending a PDU session modification command message to the UE. This procedure is possible by creating a QoS flow in the target access and transferring the QoS flow in the source to the target. Here, the source access or the target access is 3GPP or non-3GPP access, and this is to move the GBR QoS flow from one of 3GPP access and non-3GPP access to another one of 3GPP access and non-3GPP access, which is accessible to the UE. 
     To this end, 
     1) The SMF should create a new authorized QoS rule for a new QoS flow, and include information about the QFI to be transferred from one access (i.e., source access) to another (i.e. target access) in the QFI (QoS flow identifier) field of the authorized Qos flow description information element in the PUD session modification message. 
     2) Alternatively, in one embodiment, the SMF needs to change the authorized QoS flow description information element information for the PDU session in the PUD session modification message. In one embodiment, to use the corresponding GBR QoS flow after moving QFI information used in one access to another access, the QFI (QoS flow identifier) field of the authorized QoS flow description information element should be changed to the QFI information of the corresponding GBR QoS flow and included in the PDU session modification message. 
     
       
         
           
               
             
               
                 TABLE 69 
               
             
            
               
                   
               
               
                 PDU session modification command 
               
            
           
           
               
               
               
               
               
               
            
               
                 IEI 
                 Information Element 
                 Type/Reference 
                 Presence 
                 Format 
                 Length 
               
               
                   
               
               
                   
                 Extended protocol discriminator 
                 Extended protocol discriminator 
                 M 
                 V 
                 1 
               
               
                   
                   
                 9.2 
                   
                   
                   
               
               
                   
                 PDU session ID 
                 PDU session identity 
                 M 
                 V 
                 1 
               
               
                   
                   
                 9.4 
                   
                   
                   
               
               
                   
                 PTI 
                 Procedure transaction identity 
                 M 
                 V 
                 1 
               
               
                   
                   
                 9.6 
                   
                   
                   
               
               
                   
                 PDU SESSION MODIFICATION 
                 Message type 
                 M 
                 V 
                 1 
               
               
                   
                 COMMAND message identity 
                 9.7 
                   
                   
                   
               
               
                 59 
                 5GSM cause 
                 5GSM cause 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.4.2 
                   
                   
                   
               
               
                 2A 
                 Session AMBR 
                 Session-AMBR 
                 O 
                 TLV 
                 8 
               
               
                   
                   
                 9.11.4.14 
                   
                   
                   
               
               
                 56 
                 RQ timer value 
                 GPRS timer 
                 O 
                 TV 
                 2 
               
               
                   
                   
                 9.11.2.3 
                   
                   
                   
               
               
                 8- 
                 Always-on PDU session indication 
                 Always-on PDU session indication 
                 O 
                 TV 
                 1 
               
               
                   
                   
                 9.11.4.3 
                   
                   
                   
               
               
                 7A 
                 Authorized QoS rules 
                 QoS rules 
                 O 
                 TLV-E 
                 7-65538 
               
               
                   
                   
                 9.11.4.13 
                   
                   
                   
               
               
                 75 
                 Mapped EPS bearer contexts 
                 Mapped EPS bearer contexts 
                 O 
                 TLV-E 
                 7-65538 
               
               
                   
                   
                 9.11.4.8 
                   
                   
                   
               
               
                 79 
                 Authorized QoS flow descriptions 
                 QoS flow descriptions 
                 O 
                 TLV-E 
                 6-65538 
               
               
                   
                   
                 9.11.4.12 
                   
                   
                   
               
               
                 7B 
                 Extended protocol configuration 
                 Extended protocol configuration 
                 O 
                 TLV-E 
                 4-65538 
               
               
                   
                 options 
                 options 
                   
                   
                   
               
               
                   
                   
                 9.11.4.6 
                   
                   
                   
               
               
                   
                 Multiple access PDU session 
                 Multiple access PDU session 
                 O 
                 TLV-E 
                 3-65538 
               
               
                   
                 parameter container 
                 parameter container 
               
               
                   
               
            
           
         
       
     
     At step  1019 , the UE transmits a PDU session modification complete message to the SMF. 
     Thereafter, the UE may transmit uplink GBR traffic to the UPF through the target access having been changed from the source access. 
     In the above-described embodiments of the disclosure, the elements included in the disclosure are expressed in a singular or plural form according to the proposed specific embodiment. However, the singular or plural expression is appropriately selected for ease of description according to the presented situation, and the disclosure is not limited to a single element or plural elements. Those elements described in a plural form may be configured as a single element, and those elements described in a singular form may be configured as plural elements. 
     Meanwhile, although specific embodiments have been described in the detailed description of the disclosure, various modifications are possible without departing from the scope of the disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments and should be defined by the claims described below and their equivalents.