WO2019164188A1 - Method for performing handover by terminal capable of accessing plurality of network systems - Google Patents

Abstract

In order to achieve the aforementioned purpose, a disclosure of the present specification provides a method for performing a handover by a terminal capable of accessing a plurality of network systems. The method comprises the steps of: requesting connection of a PDU session from a first network system; receiving, from the first network system, information relating to whether the PDU session supports interworking; and in a case where the information indicates that the PDU session supports interworking, when the terminal performs a handover from the first network system to the second network system, transmitting a request for a handover of the PDU session configured in the first network system to the second network system.

Description

Method for handover by a terminal capable of accessing a plurality of network systems

The present invention relates to a method in which a terminal performs handover.

The 3GPP, which enacts the technical specifications of the mobile communication system, has been trying to optimize and improve the performance of 3GPP technologies since late 2004 in order to respond to various forums and new technologies related to 4G mobile communication. Started research on Term Evolution / System Architecture Evolution technology.

SAE, centered on 3GPP SA WG2, is a study on network technology aimed at determining network structure and supporting mobility between heterogeneous networks in parallel with LTE work of 3GPP TSG RAN. Recent important standardization issues of 3GPP Is one of. This is a work to develop a 3GPP system into a system supporting various radio access technologies based on IP, and has been aimed at an optimized packet-based system that minimizes transmission delay with improved data transmission capability.

The Evolved Packet System (EPS) high-level reference model defined by 3GPP SA WG2 includes non-roaming cases and roaming cases in various scenarios. See TS 23.401 and TS 23.402. The network structure diagram of FIG. 1 is a simple reconfiguration.

1 is a structural diagram of an evolved mobile communication network.

The EPC may include various components, and in FIG. 1, some of them correspond to a Serving Gateway (S-GW) 52, a PDN Packet Data Network Gateway (GW) 53, and a Mobility Management Entity (MME). 51, a Serving General Packet Radio Service (GPRS) Supporting Node (SGSN), and an enhanced Packet Data Gateway (ePDG).

The S-GW 52 operates as a boundary point between the radio access network (RAN) and the core network, and is an element that functions to maintain a data path between the eNodeB 20 and the PDN GW 53. In addition, when the UE (or User Equipment) moves over the area served by the eNodeB 20, the S-GW 52 serves as a local mobility anchor point. That is, packets may be routed through the S-GW 52 for mobility in the E-UTRAN (Universal Mobile Telecommunications System (Evolved-UMTS) Terrestrial Radio Access Network defined in 3GPP Release-8 or later). In addition, the S-GW 52 may be connected to other 3GPP networks (RANs defined before 3GPP Release-8, for example, UTRAN or GERAN (GSM (Global System for Mobile Communication) / EDGE (Enhanced Data rates for Global Evolution) Radio Access). It can also serve as an anchor point for mobility with a network).

PDN GW (or P-GW) 53 corresponds to the termination point of the data interface towards the packet data network. The PDN GW 53 may support policy enforcement features, packet filtering, charging support, and the like. In addition, mobility management between 3GPP networks and non-3GPP networks (for example, untrusted networks such as Interworking Wireless Local Area Networks (I-WLANs), code-division multiple access (CDMA) networks, or trusted networks such as WiMax) Can serve as an anchor point for.

Although the example of the network structure of FIG. 1 shows that the S-GW 52 and the PDN GW 53 are configured as separate gateways, two gateways may be implemented according to a single gateway configuration option. have.

The MME 51 is an element that performs signaling and control functions to support access to the network connection of the UE, allocation of network resources, tracking, paging, roaming and handover, and the like. . The MME 51 controls control plane functions related to subscriber and session management. The MME 51 manages a number of eNodeBs 20 and performs signaling for the selection of a conventional gateway for handover to other 2G / 3G networks. In addition, the MME 51 performs functions such as security procedures, UE-to-network session handling, idle UE location management, and the like.

The SGSN handles all packet data, such as user's mobility management and authentication to other connecting 3GPP networks (e.g., GPRS networks, UTRAN / GERAN).

The ePDG acts as a secure node for untrusted non-3GPP networks (eg, I-WLAN, WiFi hotspots, etc.).

As described with reference to FIG. 1, a UE (or UE) having IP capability is provided by an operator (ie, an operator) via various elements in the EPC on a 3GPP access as well as a non-3GPP access basis. Access to an IP service network (eg, IMS).

1 illustrates various reference points (eg, S1-U, S1-MME, etc.). In the 3GPP system, a conceptual link defining two functions existing in different functional entities of E-UTRAN and EPC is defined as a reference point. Table 1 below summarizes the reference points shown in FIG. 1. In addition to the examples of Table 1, there may be various reference points according to the network structure.

<Next Generation Mobile Communication Network>

Thanks to the success of long term evolution (LTE) / LTE-Advanced (LTE-A) for 4G mobile communication, interest in the next generation, or 5G (so-called 5G) mobile communication is increasing, and research is being conducted continuously. .

As defined by the International Telecommunication Union (ITU), "5th generation mobile communication" is a data transmission rate of up to 20Gbps and a haptic transmission rate of at least 100Mbps anywhere. The official name is “IMT-2020” and it aims to be commercialized worldwide in 2020.

The ITU presents three usage scenarios, such as Enhanced Mobile BroadBand (eMBB) massive Machine Type Communication (MMTC) and Ultra Reliable and Low Latency Communications (URLLC).

First, URLLC relates to usage scenarios that require high reliability and low latency. For example, services such as autonomous driving, factory automation, and augmented reality require high reliability and low latency (eg, less than 1 ms). Currently, latency of 4G (LTE) is statistically 21-43ms (best 10%) and 33-75ms (median). This is insufficient to support a service requiring a delay of less than 1ms.

Next, eMBB usage scenarios relate to usage scenarios that require mobile ultra-wideband.

This ultra-wideband high-speed service seems difficult to accept by the core network designed for the existing LTE / LTE-A.

Therefore, the redesign of the core network is urgently required in the so-called fifth generation mobile communication.

2 is an exemplary view showing the expected structure of the next generation mobile communication from a node perspective.

As can be seen with reference to FIG. 2, the UE is connected to a data network (DN) via a next generation Radio Access Network (RAN).

The illustrated control plane function (CPF) node is a control plane function of all or part of the mobility management entity (MME) of the 4th generation mobile communication, the serving gateway (S-GW) and the PDN gateway (P-GW). Do all or part of it. The CPF node includes an access and mobility management function (AMF) and a session management function (SMF).

The illustrated user plane function (UPF) node is a kind of gateway through which user data is transmitted and received. The UPF node may perform all or part of user plane functions of S-GW and P-GW of 4G mobile communication.

The illustrated PCF (Policy Control Function) is a node that controls the operator's policy.

The illustrated application function (AF) is a server for providing various services to the UE.

Unified Data Management (UDM) shown is a kind of server that manages subscriber information, such as the home subscriber server (HSS) of 4G mobile communication. The UDM stores and manages the subscriber information in a Unified Data Repository (UDR).

The illustrated Authentication Server Function (AUSF) authenticates and manages a UE.

The illustrated Network Slice Selection Function (NSSF) is a node for network slicing as described below.

3A illustrates multiple over two data networks PDU  Representing the architecture for supporting sessions Illustrative 3B is an exemplary diagram illustrating an architecture for supporting simultaneous access to two data networks.

3A illustrates an architecture for allowing a UE to simultaneously connect to two data networks using multiple PDU sessions. Two SMFs may be selected for two different PDU sessions.

3b shows an architecture for the UE to access two data networks simultaneously using one PDU session.

<Network Slice>

Hereinafter, slicing of a network to be introduced in the next generation mobile communication will be described.

Next-generation mobile communication introduces the concept of network slicing in order to provide various services through one network. Here, the slicing of the network is a combination of network nodes having functions required when providing a specific service. The network nodes constituting the slice instance may be hardware independent nodes or logically independent nodes.

Each slice instance can consist of any combination of nodes needed to form the entire network. In this case, one slice instance may provide a service exclusively to the UE.

Alternatively, the slice instance may be composed of a combination of some of the nodes constituting the network. In this case, the slice instance may not provide a service to the UE alone, but may provide a service to the UE in association with other existing network nodes. In addition, a plurality of slice instances may be associated with each other to provide a service to the UE.

Slice instances differ from dedicated core networks in that the entire network node, including the core network (CN) node and the RAN, can be separated. Slice instances are also different from dedicated core networks in that network nodes can be logically separated.

Roaming in next-generation cellular networks

On the other hand, there are two ways of handling signaling requests from the UE in a situation where the UE roams to a visited network, for example, a VPLMN (Visited Public Land Mobile Network). The first method, the local break out (LBO) method, processes signaling requests from the UE in the visited network. According to the second method, the home routing (HR) method, the visited network transmits a signaling request from the UE to the home network of the UE.

4a is Roaming LBO (local breakout) is an exemplary view showing an architecture applied, Figure 4b Roaming  It is an exemplary view showing an architecture to which the home routed (HR) method is applied.

As shown in FIG. 4A, in an architecture in which the LBO scheme is applied, data of a user is transferred to a data network in a VPLMN. To this end, the PCF in the VPLMN interacts with AF to generate PCC rules for service in the VPLMN. The PCF node in the VPLMN generates a PCC rule based on a policy set therein according to a roaming agreement with a Home Public Land Mobile Network (HPLMN) operator.

As shown in FIG. 4B, in the architecture where the HR scheme is applied, data of the UE is delivered to a data network in the HPLMN.

Data bypass to non-3GPP networks

In next generation mobile communication, data of the UE may be bypassed to a non-3GPP network, such as a Wireless Local Area Network (WLAN) or Wi-Fi.

Figure 5a To  5f is non- 3GPP  Represents architectures for bypassing data into a network.

Wireless Local Area Network (WLAN) or Wi-Fi is considered to be an untrusted non-3GPP network. In order to connect the non-3GPP network to the core network, a Non-3GPP InterWorking Function (N3IWF) may be added.

Interworking with existing 4th generation mobile communication systems

Even if the UE is out of coverage of the next generation Radio Access Network (RAN), the UE should be able to receive service even through a 4th generation (4G) mobile communication system. This is called interworking. Hereinafter, interworking will be described in detail.

6a UE Not roam  If not Interworking  6b shows an architecture for interworking when the UE roams.

Referring to FIG. 6A, when the UE does not roam, the E-UTRAN, the EPC, and the fifth generation mobile communication network for the existing fourth generation LTE may be interworked with each other. In FIG. 6A, a packet data network gateway (PGW) for an existing EPC is divided into a PGW-U serving only a user plane and a PGW-C serving a control plane. The PGW-U is merged into the UPF node of the fifth generation core network, and the PGW-C is merged into the SMF node of the fifth generation core network. In addition, the PCRF (Policy and Charging Rules Function) for the existing EPC can be incorporated into the PCF of the fifth generation core network. And HSS for existing EPC can be merged into UDM of 5th generation core network. The UE may access the core network via the E-UTRAN, but the UE may access the core network through the 5G radio access network (RAN) and AMF.

Referring to FIG. 6A and FIG. 6B, when the UE roams into a VPLMN (Vissited Public Land Mobile Network), data of the UE is transmitted via an HPLMN (Home PLMN).

Meanwhile, the N26 interface illustrated in FIGS. 6A and 6B is an interface connected between the MME and the AMF in order to facilitate interworking between the EPC and the NG core. This N26 interface may be selectively supported according to the operator. That is, the network operator may or may not provide an N26 interface for interworking with the EPC.

Meanwhile, as the terminal moves, a situation in which the terminal needs to handover PDU sessions to another network system may occur. However, if the network system of the region to which the terminal has moved does not support the PDU session that received the service from the previous network system, unnecessary / inefficient signaling overhead in which the request of the mobile terminal and the rejection of the network node are repeated. There is a problem that occurs.

In order to achieve the above object, one disclosure of the present specification provides a method for performing a handover (handover) by a terminal that can access a plurality of network systems. The method includes requesting a connection of a protocol data unit (PDU) session to a first network system; Receiving information related to whether the PDU session supports interworking from the first network system; And when the terminal indicates that the PDU session supports interworking, when the terminal hands over from the first network system to the second network system, the PDU session established in the first network system is changed to the second network. And sending a request to handover to the system.

The terminal may determine whether to handover the PDU session to the second network system based on the information.

If the PDU session does not support interworking, the terminal may not request handover of the PDU session.

The first network system may be a 5th generation system (5GS), the second network system may be an evolved packet system (EPS), the first network system may be the EPS, and the second network system may be the 5GS.

When the first network system is 5GS and the second network system is EPS, the information is an access point name (APN), and the APN may be set differently depending on whether the PDU session supports interworking. .

When the first network system is EPS and the second network system is 5GS, the information is a data network name (DNN), and the DNN may be set differently depending on whether the PDU session supports interworking. .

In order to achieve the above object, another disclosure of the present disclosure provides a terminal capable of connecting to a plurality of network systems. The terminal, the transceiver for transmitting and receiving a signal; And a processor for controlling the transceiver, wherein the processor requests a connection of a protocol data unit (PDU) session to a first network system, and supports the interworking of the PDU session from the first network system. Receiving information related to whether the PDU session supports the interworking, and when the terminal is handed over from the first network system to the second network system, the information set in the first network system The request for handing over the PDU session to the second network system may be transmitted.

According to one disclosure of the present specification, there is an effect of reducing signaling overhead by providing a method of processing a PDU session during handover of a terminal.

1 is a structural diagram of an evolved mobile communication network.

2 is an exemplary view showing the expected structure of the next generation mobile communication from a node perspective.

3A is an exemplary diagram illustrating an architecture for supporting multiple PDU sessions over two data networks, and FIG. 3B is an exemplary diagram illustrating an architecture for supporting simultaneous access to two data networks.

4A is an exemplary diagram illustrating an architecture in which a local breakout (LBO) scheme is applied when roaming, and FIG. 4B is an exemplary diagram illustrating an architecture in which a home routed (HR) scheme is applied when roaming.

5A-5F illustrate architectures for bypassing data with a non-3GPP network.

6A shows an architecture for interworking when the UE does not roam, and FIG. 6B shows an architecture for interworking when the UE roams.

7 illustrates a situation in which handover occurs as the terminal moves.

8 illustrates a conventional problem when a handover of the terminal occurs.

9 shows Proposal 1-1 presented herein.

10 shows the proposal 2-1 presented herein.

11a and 11b show the proposal 2-2 presented herein.

12 is a block diagram illustrating a wireless communication system in which an embodiment presented herein is implemented.

FIG. 13 is a detailed block diagram of a transceiver of the wireless device shown in FIG. 12.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments, and are not intended to limit the present invention. In addition, the technical terms used in the present specification should be interpreted as meanings generally understood by those skilled in the art unless they are specifically defined in this specification, and are overly inclusive. It should not be interpreted in the sense of or in the sense of being excessively reduced. In addition, when the technical terms used herein are incorrect technical terms that do not accurately represent the spirit of the present invention, it should be replaced with technical terms that can be understood correctly by those skilled in the art. In addition, the general terms used in the present invention should be interpreted as defined in the dictionary or according to the context before and after, and should not be interpreted in an excessively reduced sense.

Also, the singular forms used herein include the plural forms unless the context clearly indicates otherwise. In the present application, the term “consisting of” or “having” should not be construed as necessarily including all of the various components, or various steps described in the specification, and some of the components or some steps may not be included. It should be construed that it may further include additional components or steps.

In addition, terms including ordinal numbers, such as first and second, as used herein may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

When a component is said to be connected or connected to another component, it may be directly connected to or connected to the other component, but other components may be present in between. On the other hand, when a component is mentioned as being directly connected or directly connected to another component, it should be understood that no other component exists in the middle.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. In addition, in describing the present invention, when it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof is omitted. In addition, it should be noted that the accompanying drawings are only for easily understanding the spirit of the present invention and should not be construed as limiting the spirit of the present invention by the accompanying drawings. The spirit of the present invention should be construed to extend to all changes, equivalents, and substitutes in addition to the accompanying drawings.

In the accompanying drawings, although a user equipment (UE) is illustrated as an example, the illustrated UE may be referred to in terms of UE 100 (Terminal), Mobile Equipment (ME), and the like. In addition, the UE may be a portable device such as a laptop, a mobile phone, a PDA, a smart phone, a multimedia device, or a non-portable device such as a PC or a vehicle-mounted device.

Session and Service Continuity

Next-generation mobile communication networks provide various modes to support session and service continuity (SSC).

1) SSC mode 1

The UPF, which acts as a PDU session anchor during the PDU session establishment process, remains independent of the access technology (ie, access type and cell). In case of an IP type PDU session, IP continuity is supported regardless of the movement of the UE. SSC mode 1 may be applied to any PDU session type and may be applied to any access type.

2) SSC mode 2

If the PDU session has one PDU session anchor, the network may trigger the release of the PDU session and instruct the UE to establish the same PDU session. During the establishment of the new PDU session, a UPF acting as a PDU session anchor may be newly selected. SSC mode 2 may be applied to any PDU session type and may be applied to any access type.

3) SSC mode 3

For a PDU session for SSC mode 3, the network may allow the UE to establish a connection using a new PDU session to the same data network before releasing the connectivity between the UE and the previous PDU session anchor. When the trigger condition is applied, the network may determine whether to select a suitable PDU session anchor, i.e., UPF, for the new condition of the UE. SSC mode 3 can be applied to any PDU session type and can be applied to any access type.

4) SSC mode selection

The SSC mode selection policy may be used to determine the type of SSC mode associated with the UE's application or the UE's application group.

The operator may provide the SSC mode selection policy to the UE. The policy may include one or more SSC mode selection policy rules.

7 is in accordance with the movement of the terminal Handover  FIG. 8 illustrates a conventional situation when a handover of the terminal occurs.

Referring to FIGS. 7 and 8, when the UE moves from an area serving a 5G system (5GS) to an area serving an evolved packet system (EPS), the UE handovers PDU sessions received from the 5GS to an EPS. (handover) However, there may be a PDU session that is not supported by EPS among PDU sessions that are serviced by 5GS. In this case, the UE may request PDU session establishment / modification from the EPS network node for handover, and the EPS network nodes may reject the UE's request for the PDU session in which they do not support the service. Thereafter, the UE may try to request PDU session establishment / modification again for the PDU session in which handover is rejected. Even if the UE requests PDU session establishment / modification again, the EPS network node may reject the request again.

On the contrary, when the UE moves from the region serving the EPS to the region serving the 5GS, the terminal hands over the PDU sessions received from the EPS to the 5GS. However, there may be a PDU session that is not supported by 5GS among the PDU sessions received from the EPS. In this case, the UE requests PDU session establishment / modification to the 5GS network node for handover, and the 5GS network nodes reject the UE's request for the PDU session for which they do not support the service. Thereafter, the UE may attempt to request a PDU session establishment / modification again for the PDU session in which handover is rejected. Even if the UE requests PDU session establishment / modification again, the 5GS network node may reject the request again.

Here, the network before moving may be referred to as a source network, and the network to be moved may be referred to as a target network.

In this case, the PDU session to perform the handover may include an IMS voice (related) PDU session for supporting service continuity, and the PDU session in which the handover is rejected may include an encrypted user plane PDU session. It may include.

Therefore, when the network system in the region to which the terminal has moved does not support the PDU session that has received the service from the previous network system, unnecessary / inefficient signaling overhead in which the request of the mobile terminal and the rejection of the network node are repeated. There is a problem that occurs.

Disclosure of the Invention

The disclosure of the present specification proposes a method of efficiently processing a PDU session by minimizing the signaling overhead occurring in the above situation.

<Proposal 1>

When the source network node receives the PDU session establishment / modification request from the terminal, the source network node may transmit information on whether the PDU session supports interworking (interworking) to the terminal. The information may be included in a response to the PDU session establishment / modification request.

The information includes interworking availability information / indication, interworking unavailability information / indication, interworking is supported, or information indicating that no interworking is supported. (interworking is not supported).

The terminal handovers the PDU session to the target network (eg, EPS) based on the information received from the source network node when a handover (or intersystem change) occurs in the source network (eg, 5GS). You can decide whether or not to do so.

That is, when the information means that the PDU session supports interworking, the UE may transmit a PDU session establishment / modification request to the target network in order to perform handover for the PDU session. On the other hand, when the information means that the target network does not support the PDU session, the terminal may not transmit a PDU session establishment / modification request to the target network.

Here, when the source network is 5GS, the target network may be EPS. Conversely, if the source network is EPS, the target network may be 5GS.

<Proposal 1-1>

9 shows Proposal 1-1 presented herein.

Referring to FIG. 9, when the terminal transmits the PDU session establishment / modification request to a source network, the source network may transmit information on whether the PDU session is interworking to the terminal. The information may be included in a response to the PDU session establishment / modification request.

The information includes interworking availability information / indication, interworking unavailability information / indication, interworking is supported, or information indicating that no interworking is supported. (interworking is not supported).

When the source network is 5GS, the SMF may transmit the information to the terminal. When the source network is EPS, the PGW-C may transmit the information to the terminal through a protocol configuration option (PCO) of the response.

When a handover (or intersystem change) from the source network to the target network occurs, the terminal determines whether to handover the PDU session to the target network (EPS or 5GS) based on the information received from the source network node. Can be.

That is, when the information means that the PDU session supports interworking, when the handover from the source network to the target network occurs, the terminal may transmit a request for performing the handover for the PDU session. On the other hand, when the information means that the PDU session does not support interworking, even if a handover occurs from the source network to the target network, the UE may not transmit a handover request for the PDU session.

For example, interworking availability information / indication of a PDU session or information indicating that a PDU session supports interworking is included in a response of the source network to a PDU session establishment / modification request of the UE. If so, the UE can recognize that the PDU session supports interworking. Therefore, in such a case, if an intersystem change occurs, the UE may move the PDU session to the target network. On the other hand, interworking availability information / indication of the PDU session or information indicating that the PDU session supports interworking is included in the response of the source network to the PDU session establishment / modification request of the UE. If not, the UE may recognize that the PDU session does not support interworking. Therefore, in this case, if an intersystem change occurs, the terminal may not move the PDU session to the target network.

Also, interworking unavailability information / indication of a PDU session or information indicating that a PDU session does not support interworking in response to the source network to a PDU session establishment / modification request of the UE. supported), the UE may recognize that the PDU session does not support interworking. Therefore, in this case, if an intersystem change occurs, the terminal may not move the PDU session to the target network. On the other hand, interworking unavailability information / indication of the PDU session or information indicating that the PDU session does not support interworking in response to the target network to the PDU session establishment / modification request of the UE (interworking is not) If supported) is not included, the UE can recognize that the PDU session supports interworking. Therefore, in such a case, if an intersystem change occurs, the UE may move the PDU session to the target network.

<Proposal 1-2>

When the source network is 5GS and 5GS receives a PDU session establishment / modification request from the UE, the SMF of 5GS may transmit a response to the PDU session establishment / modification request to the UE. The response may include information about interworking support of the PDU session.

The information on the interworking support includes interworking availability information / indication, interworking unavailability information / indication, interworking is supported, or interworking support. It may be information indicating not working (interworking is not supported).

On the other hand, when the source network is EPS and the EPS receives a PDU session establishment / modification request from the terminal, the PGW-C of the EPS may transmit a response to the PDU session establishment / modification request to the terminal. However, unlike the case where the source network is 5GS, the response may not include information on the interworking support. However, the PGW-C of the EPS may transmit single-network slice selection assistance information (S-NSSAI) related to the PDU session to the terminal through the PCO of the response during a packet data network (PDN) connection establishment / modification process. In this case, the UE may recognize that only the PDU session related to the received S-NSSAI can be moved to 5GS, and that the PDU session not related to S-NSSAI cannot be moved to 5GS. Accordingly, the terminal may determine whether to transmit a PDU session establishment / modification request based on the S-NSSAI.

<Proposal 2>

<Proposal 2-1>

10 shows the proposal 2-1 presented herein.

Referring to FIG. 10, when the terminal transmits a PDU session establishment / modification request to a source network, the source network may transmit a response to the PDU session establishment / modification request to the terminal.

The response may include a data network name (DNN) / access point name (APN) associated with the PDU session. That is, when the source network is EPS, the response may include an APN associated with the PDU session, and when the source network is 5GS, the response may include a DNN associated with the PDU session. The DNN / APN may be configured differently depending on whether the PDU session supports interworking.

The DNN / APN is information indicating that interworking can be supported for the DNN / APN (interworking is supported for the DNN / APN), or information indicating that interworking cannot be supported for the DNN / APN ( interworking is not supported for the DNN / APN).

The DNN / APN may be provided to the terminal in advance by using a UE route selection policy (URSP), or may be pre-configured in a universal subscriber identification module (USIM).

Alternatively, the DNN / APN may be set in advance through an OMA-DM (Open Mobile Alliance (OMA) -Device Management (DM)), or may be preset and stored through a NAS signaling procedure from a network. . The NAS signaling procedure may include a mobility management procedure (registration, attach and TAU procedure) and a session management procedure (PDU session establishment and PDN connectivity request procedure).

When an intersystem change occurs, the UE may determine whether to move the PDU session to the target network based on the DNN / APN provided from the source network. That is, the UE transmits a PDU session establishment / modification request only for PDU sessions that support interworking based on DNN / APN, and transmits a PDU session establishment / modification request for PDU sessions that do not support interworking. You can't.

<Proposal 2-2>

11a and 11b show the proposal 2-2 presented herein.

Referring to FIG. 11A, when a terminal receiving a service from a source network moves to a target network, the terminal may hand over a PDU session established in the source network to the target network. In this case, when the target network does not support the PDU session, network nodes of the target network reject the setup / modification request for the PDU session and the network nodes transmit a rejection message including a reason for rejection to the terminal. Can be. When the reject message is received, the terminal may not retry the setup / modification request for the corresponding PDU session. However, when the UE is powered off, or when the UE enters a new PLMN or the PLMN is changed, the UE may transmit a PDU session establishment / modification request for the corresponding PDU session. have.

Referring to FIG. 11B, the target network may further provide a back-off timer to the terminal. The terminal may perform a setup / modification request for a corresponding PDU session only after the back-off timer expires. If the terminal does not expire, the terminal may not perform the setup / modification request.

Alternatively, unlike FIG. 11B, the network may use a timer value pre-configured in the terminal without providing a timer to the terminal. The terminal may perform a setup / modification request for a corresponding PDU session only after the preset timer value has expired. If the terminal does not expire, the terminal may not perform the setup / modification request.

The reason for rejection may include information indicating that the PDU session is not available, information indicating that the PDU session is not allowed in the target network, And / or the PDU session may include interworking is not supported for the PDU session.

The source network may be EPS, and the target network may be 5GS. Alternatively, the source network may be 5GS, and the target network may be EPS.

Degree 12 is  A block diagram showing a wireless communication system in which an embodiment presented herein is implemented.

The base station 200 includes a processor 201, a memory 202, and an RF unit 203. The memory 202 is connected to the processor 201 and stores various information for driving the processor 201. The RF unit 203 is connected to the processor 201 to transmit and / or receive a radio signal. The processor 201 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the base station may be implemented by the processor 51.

The wireless device 100 includes a processor 101, a memory 102, and an RF unit 103. The memory 102 is connected to the processor 101 and stores various information for driving the processor 101. The RF unit 103 is connected to the processor 101 and transmits and / or receives a radio signal. The processor 101 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the wireless device may be implemented by the processor 101.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

FIG. 13 is a detailed block diagram of a transceiver of the wireless device shown in FIG. 12.

Referring to FIG. 13, the transceiver 110 includes a transmitter 111 and a receiver 112. The transmitter 111 includes a discrete fourier transform (DFT) unit 1111, a subcarrier mapper 1112, an IFFT unit 1113, a CP inserter 1114, and a wireless transmitter 1115. The transmitter 111 may further include a modulator. Further, for example, the apparatus may further include a scramble unit (not shown), a modulation mapper (not shown), a layer mapper (not shown) and a layer permutator (not shown). It may be disposed before the DFT unit 1111. That is, in order to prevent an increase in the peak-to-average paging interval (POPR) power ratio, the transmitter 111 first passes the information through the DFT 1111 before mapping a signal to a subcarrier. After subcarrier mapping of a signal spread by the DFT unit 1111 (or precoded in the same sense) through the subcarrier mapper 1112, the inverse fast fourier transform (IFFT) unit 1113 is again on the time axis. Make it a signal.

The DFT unit 1111 outputs complex-valued symbols by performing a DFT on the input symbols. For example, when Ntx symbols are input (where Ntx is a natural number), the DFT size is Ntx. The DFT unit 1111 may be called a transform precoder. The subcarrier mapper 1112 maps the complex symbols to each subcarrier in the frequency domain. The complex symbols may be mapped to resource elements corresponding to resource blocks allocated for data transmission. The subcarrier mapper 1112 may be called a resource element mapper. The IFFT unit 1113 performs an IFFT on the input symbol and outputs a baseband signal for data, which is a time domain signal. The CP inserter 1114 copies a part of the rear part of the base band signal for data and inserts it in the front part of the base band signal for data. Inter-symbol interference (ISI) and inter-carrier interference (ICI) can be prevented through CP insertion to maintain orthogonality even in multipath channels.

On the other hand, the receiver 112 includes a wireless receiver 1121, a CP remover 1122, an FFT unit 1123, an equalizer 1124, and the like. The radio receiver 1121, the CP remover 1122, and the FFT unit 1123 of the receiver 112 include a radio transmitter 1115, a CP insertion unit 1114, and an IFF unit 1113 at the transmitter 111. Performs the reverse function of The receiver 112 may further include a demodulator.

Claims (12)

1. In a method for performing a handover (handover) by a terminal that can access a plurality of network systems,

   Requesting a connection of a protocol data unit (PDU) session to a first network system;

   Receiving information related to whether the PDU session supports interworking from the first network system; And

   If the information indicates that the PDU session supports interworking, when the terminal handovers from the first network system to the second network system, the PDU session established in the first network system is changed to the second network system. Sending a request to handover to a network.
2. The method of claim 1, wherein the terminal determines whether to handover the PDU session to the second network system based on the information.
3. The method of claim 1, wherein the terminal does not request handover of the PDU session when the PDU session does not support interworking.
4. According to claim 1,

   The first network system is a 5th generation system (5GS), the second network system is an EPS (evolved packet system),

   Wherein the first network system is the EPS and the second network system is the 5GS.
5. According to claim 1,

   When the first network system is 5GS and the second network system is EPS, the information is an access point name (APN),

   The APN is configured differently depending on whether the PDU session supports interworking.
6. According to claim 1,

   When the first network system is EPS and the second network system is 5GS, the information is a data network name (DNN),

   The DNN is configured differently depending on whether the PDU session supports interworking.
7. In a terminal that can be connected to a plurality of network systems,

   A transceiver for transmitting and receiving a signal; And

   A processor for controlling the transceiver;

   The processor,

   Request a connection of a protocol data unit (PDU) session to the first network system,

   Receive information regarding whether the PDU session supports interworking from the first network system,

   If the information indicates that the PDU session supports interworking, when the terminal handovers from the first network system to the second network system, the PDU session established in the first network system is changed to the second network system. A terminal for transmitting a request for handover to the terminal.
8. The method of claim 7, wherein

   And the processor determines whether to handover the PDU session to the second network system based on the information.
9. 8. The terminal of claim 7, wherein the processor does not request handover of the PDU session if the PDU session does not support interworking.
10. The method of claim 7.

    The first network system is a 5th generation system (5GS), the second network system is an EPS (evolved packet system),

    The first network system is the EPS, the second network system is the terminal 5GS.
11. The method of claim 7, wherein

    When the first network system is 5GS and the second network system is EPS, the information is an access point name (APN),

    The APN is configured differently depending on whether the PDU session supports interworking.
12. The method of claim 7, wherein

    When the first network system is EPS and the second network system is 5GS, the information is a data network name (DNN),

    The DNN is configured differently depending on whether the PDU session supports interworking.

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