WO2018026232A1 - Method for supporting cl service in wireless communication system and device therefor - Google Patents

Abstract

One embodiment of the present invention relates to a method by which a core control plane (CP) supports a connectionless (CL) service in a wireless communication system, comprising the steps of: allowing the core CP to receive, from a radio access network (RAN), first information for notifying that UE is unreachable; and allowing the core CP to transmit, to all UPGWs associated with the UE, second information for notifying that the UE is unreachable.

Description

CL service support method in wireless communication system and apparatus therefor

The following description relates to a wireless communication system, and more particularly, to a method and apparatus for supporting a ConnectionLess (CL) service.

Wireless communication systems are widely deployed to provide various kinds of communication services such as voice and data. In general, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency (SC-FDMA). division multiple access (MCD) systems and multi-carrier frequency division multiple access (MC-FDMA) systems.

In the present invention, in the mobile communication system such as 3GPP EPS, Next Generation system (aka 5G), it is necessary to efficiently handle transmission failure when sending data without explicitly establishing a connection between the RAN and the Core Network for the UE. The method is a technical task.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

According to an embodiment of the present invention, in a method in which a core control plane (CP) supports a ConnectionLess (CL) service in a wireless communication system, first information indicating that the core CP is unreachable from a radio access network (RAN) by the core CP Receiving; And transmitting, by the core CP, all of the UPGWs associated with the UE to the second information informing that the UE is unreachable.

An embodiment of the present invention, a core control plane (CP) device for supporting a CL (ConnectionLess) service in a wireless communication system, comprising: a transceiver; And a processor, wherein the core CP receives, from the radio access network (RAN), first information indicating that the UE is unreachable through the transmitting and receiving device, and the core CP informs all UPGWs associated with the UE to the UE. Is a core CP device that transmits, via the transceiver device, second information indicating that is unreachable.

The second information may be an indication that the UPGW receiving the second information changes all UPGW ConnectionLess Service Information (UCLSI) for the UE to the IDLE state.

The UPGW of the UE may have two UCLSI whose status is REACHABLE for the UE.

The first information may be received when at least one of the two or more UCLSI is changed to the IDLE state.

The second information may be transmitted when the UPGW of the UE has two UCLSI whose status is REACHABLE for the UE.

The first information may be received when at least one of the two or more UCLSI is changed to the IDLE state.

Each of the two or more UPGWs of the UE may have at least one UCLSI whose status is REACHABLE for the UE.

The first information may be received when the UCLSI for the UE included in at least one UPGW of the two or more UPGWs is changed to an IDLE state.

The second information may be transmitted when each of two or more UPGWs of the UE has at least one UCLSI whose status is REACHABLE for the UE.

The first information may be received when the UCLSI for the UE included in at least one UPGW of the two or more UPGWs is changed to an IDLE state.

The first information may be transmitted when the RAN transmits a NACK to the UPGW.

When the RAN transmits the NACK, the first information may be omitted from the UPGW that receives the NACK.

The UPGW that receives the NACK may change all UCLSI for the UE to an ILDE state.

The core CP may be composed of one or more of an MM CP function, an SM CP function, a function having subscriber information, and a function for managing SM information of the UE.

According to the present invention, unnecessary transmission can be prevented from repeating in a transmission failure situation.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings appended hereto are for the purpose of providing an understanding of the present invention and for illustrating various embodiments of the present invention and for describing the principles of the present invention together with the description of the specification.

1 is a diagram illustrating a schematic structure of an EPS (Evolved Packet System) including an Evolved Packet Core (EPC).

2 is an exemplary view showing the architecture of a general E-UTRAN and EPC.

3 is an exemplary view showing the structure of a radio interface protocol in a control plane.

4 is an exemplary view showing the structure of a radio interface protocol in a user plane.

5 is a flowchart illustrating a random access procedure.

6 is a diagram illustrating a connection process in a radio resource control (RRC) layer.

7 is a diagram for describing a 5G system.

8 is a diagram illustrating a structure for CL mode transmission.

9 is a diagram for explaining CL downlink data transmission according to an embodiment of the present invention.

10 is a diagram illustrating a configuration of a node device according to an embodiment of the present invention.

The following embodiments combine the components and features of the present invention in a predetermined form. Each component or feature may be considered to be optional unless otherwise stated. Each component or feature may be embodied in a form that is not combined with other components or features. In addition, some components and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

Embodiments of the present invention may be supported by standard documents disclosed in relation to at least one of the Institute of Electrical and Electronics Engineers (IEEE) 802 series system, 3GPP system, 3GPP LTE and LTE-A system, and 3GPP2 system. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.

The following techniques can be used in various wireless communication systems. For clarity, the following description focuses on 3GPP LTE and 3GPP LTE-A systems, but the technical spirit of the present invention is not limited thereto.

Terms used in this document are defined as follows.

UMTS (Universal Mobile Telecommunications System): A third generation mobile communication technology based on Global System for Mobile Communication (GSM) developed by 3GPP.

Evolved Packet System (EPS): A network system composed of an Evolved Packet Core (EPC), which is a packet switched (PS) core network based on Internet Protocol (IP), and an access network such as LTE / UTRAN. UMTS is an evolutionary network.

NodeB: base station of GERAN / UTRAN. It is installed outdoors and its coverage is macro cell size.

eNodeB: base station of E-UTRAN. It is installed outdoors and its coverage is macro cell size.

UE (User Equipment): a user device. The UE may be referred to in terms of terminal, mobile equipment (ME), mobile station (MS), and the like. In addition, the UE may be a portable device such as a laptop, a mobile phone, a personal digital assistant (PDA), a smart phone, a multimedia device, or the like, or may be a non-portable device such as a personal computer (PC) or a vehicle-mounted device. In the context of MTC, the term UE or UE may refer to an MTC device.

Home NodeB (HNB): A base station of a UMTS network, which is installed indoors and has a coverage of a micro cell.

HeNB (Home eNodeB): A base station of an EPS network, which is installed indoors and its coverage is micro cell size.

Mobility Management Entity (MME): A network node of an EPS network that performs mobility management (MM) and session management (SM) functions.

Packet Data Network-Gateway (PDN-GW) / PGW: A network node of an EPS network that performs UE IP address assignment, packet screening and filtering, charging data collection, and the like.

Serving Gateway (SGW): A network node of an EPS network that performs mobility anchor, packet routing, idle mode packet buffering, and triggers the MME to page the UE.

Non-Access Stratum (NAS): Upper stratum of the control plane between the UE and the MME. A functional layer for exchanging signaling and traffic messages between a UE and a core network in an LTE / UMTS protocol stack, which supports session mobility and establishes and maintains an IP connection between the UE and the PDN GW. Supporting is the main function.

Packet Data Network (PDN): A network in which a server supporting a specific service (eg, a Multimedia Messaging Service (MMS) server, a Wireless Application Protocol (WAP) server, etc.) is located.

PDN connection: A logical connection between the UE and the PDN, represented by one IP address (one IPv4 address and / or one IPv6 prefix).

RAN (Radio Access Network): a unit including a NodeB, an eNodeB and a Radio Network Controller (RNC) controlling them in a 3GPP network. It exists between UEs and provides a connection to the core network.

Home Location Register (HLR) / Home Subscriber Server (HSS): A database containing subscriber information in the 3GPP network. The HSS may perform functions such as configuration storage, identity management, and user state storage.

Public Land Mobile Network (PLMN): A network composed for the purpose of providing mobile communication services to individuals. It may be configured separately for each operator.

Proximity Service (or ProSe Service or Proximity based Service): A service that enables discovery and direct communication between physically close devices or communication through a base station or through a third party device. In this case, user plane data is exchanged through a direct data path without passing through a 3GPP core network (eg, EPC).

Evolved Packet Core (EPC)

1 is a diagram illustrating a schematic structure of an EPS (Evolved Packet System) including an Evolved Packet Core (EPC).

EPC is a key element of System Architecture Evolution (SAE) to improve the performance of 3GPP technologies. SAE is a research project to determine network structure supporting mobility between various kinds of networks. SAE aims to provide an optimized packet-based system, for example, supporting various radio access technologies on an IP basis and providing enhanced data transfer capabilities.

Specifically, the EPC is a core network of an IP mobile communication system for a 3GPP LTE system and may support packet-based real-time and non-real-time services. In a conventional mobile communication system (i.e., a second generation or third generation mobile communication system), the core network is divided into two distinct sub-domains of circuit-switched (CS) for voice and packet-switched (PS) for data. The function has been implemented. However, in the 3GPP LTE system, an evolution of the third generation mobile communication system, the sub-domains of CS and PS have been unified into one IP domain. That is, in the 3GPP LTE system, the connection between the terminal and the terminal having the IP capability (capability), IP-based base station (for example, eNodeB (evolved Node B)), EPC, application domain (for example, IMS ( IP Multimedia Subsystem)). That is, EPC is an essential structure for implementing end-to-end IP service.

The EPC may include various components, and in FIG. 1, some of them correspond to a serving gateway (SGW), a packet data network gateway (PDN GW), a mobility management entity (MME), and a serving general packet (SGRS) Radio Service (Supporting Node) and Enhanced Packet Data Gateway (ePDG) are shown.

The SGW (or S-GW) acts 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 and the PDN GW. In addition, when the UE moves over the area served by the eNodeB, the SGW serves as a local mobility anchor point. That is, packets may be routed through the SGW for mobility in the E-UTRAN (Universal Mobile Telecommunications System (Evolved-UMTS) Terrestrial Radio Access Network defined in 3GPP Release-8 or later). SGW also provides mobility with other 3GPP networks (RANs defined before 3GPP Release-8, such as UTRAN or GERAN (Global System for Mobile Communication (GSM) / Enhanced Data rates for Global Evolution (EDGE) Radio Access Network). It can also function as an anchor point.

The PDN GW (or P-GW) corresponds to the termination point of the data interface towards the packet data network. The PDN GW 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 SGW and the PDN GW are configured as separate gateways, two gateways may be implemented according to a single gateway configuration option.

The MME 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 controls control plane functions related to subscriber and session management. The MME manages a number of eNodeBs and performs signaling for the selection of a conventional gateway for handover to other 2G / 3G networks. The MME also performs functions such as security procedures, terminal-to-network session handling, and idle terminal location management.

SGSN handles all packet data, such as user's mobility management and authentication to other 3GPP networks (eg GPRS networks).

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 terminal having IP capability is an IP service network provided by an operator (ie, an operator) via various elements in the EPC, based on 3GPP access as well as non-3GPP access. (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.

Reference point	Explanation
S1-MME	Reference point for the control plane protocol between E-UTRAN and MME
S1-U	Reference point between E-UTRAN and Serving GW for the per bearer user plane tunneling and inter eNodeB path switching during handover
S3	Reference point between the MME and SGSN providing user and bearer information exchange for mobility between 3GPP access networks in idle and / or active state. This reference point can be used in PLMN-to-PLMN-to-for example (for PLMN-to-PLMN handovers) (It enables user and bearer information exchange for inter 3GPP access network mobility in idle and / or active state This reference point can be used intra-PLMN or inter-PLMN (eg in the case of Inter-PLMN HO).)
S4	(Reference point between SGW and SGSN that provides related control and mobility support between the GPRS core and SGW's 3GPP anchor functionality.It also provides user plane tunneling if no direct tunnel is established.) and the 3GPP Anchor function of Serving GW.In addition, if Direct Tunnel is not established, it provides the user plane tunnelling.)
S5	Reference point providing user plane tunneling and tunnel management between the SGW and the PDN GW. It provides user plane tunneling and tunnel management between Serving GW and PDN GW.It is used because of the mobility of the terminal, and for connection to a PDN GW where the SGW is not co-located for the required PDN connectivity. for Serving GW relocation due to UE mobility and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.)
S11	Reference point between MME and SGW
SGi	Reference point between the PDN GW and the PDN. The PDN may be an operator external public or private PDN or, for example, an in-operator PDN for the provision of IMS services. It is the reference point between the PDN GW and the packet data network.Packet data network may be an operator external public or private packet data network or an intra operator packet data network, eg for provision of IMS services.This reference point corresponds to Gi for 3GPP accesses.)

Among the reference points shown in FIG. 1, S2a and S2b correspond to non-3GPP interfaces. S2a is a reference point that provides the user plane with associated control and mobility support between trusted non-3GPP access and PDN GW. S2b is a reference point that provides the user plane with relevant control and mobility support between the ePDG and PDN GW.

2 is an exemplary view showing the architecture of a general E-UTRAN and EPC.

As shown, an eNodeB can route to a gateway, schedule and send paging messages, schedule and send broadcaster channels (BCHs), and resources in uplink and downlink while an RRC (Radio Resource Control) connection is active. Can perform functions for dynamic allocation to the UE, configuration and provision for measurement of the eNodeB, radio bearer control, radio admission control, and connection mobility control. Within the EPC, paging can occur, LTE_IDLE state management, user plane can perform encryption, SAE bearer control, NAS signaling encryption and integrity protection.

3 is an exemplary diagram illustrating a structure of a radio interface protocol in a control plane between a terminal and a base station, and FIG. 4 is an exemplary diagram illustrating a structure of a radio interface protocol in a user plane between a terminal and a base station. .

The air interface protocol is based on the 3GPP radio access network standard. The air interface protocol is composed of a physical layer, a data link layer, and a network layer horizontally, and a user plane and control for data information transmission vertically. It is divided into a control plane for signal transmission.

The protocol layers are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems, and includes L1 (first layer), L2 (second layer), and L3 (third layer). ) Can be separated.

Hereinafter, each layer of the radio protocol of the control plane shown in FIG. 3 and the radio protocol in the user plane shown in FIG. 4 will be described.

The physical layer, which is the first layer, provides an information transfer service using a physical channel. The physical layer is connected to a medium access control layer on the upper side through a transport channel, and data between the medium access control layer and the physical layer is transmitted through the transport channel. In addition, data is transferred between different physical layers, that is, between physical layers of a transmitting side and a receiving side through a physical channel.

The physical channel is composed of several subframes on the time axis and several sub-carriers on the frequency axis. Here, one subframe includes a plurality of symbols and a plurality of subcarriers on the time axis. One subframe consists of a plurality of resource blocks, and one resource block consists of a plurality of symbols and a plurality of subcarriers. The transmission time interval (TTI), which is a unit time for transmitting data, is 1 ms corresponding to one subframe.

According to 3GPP LTE, the physical channels existing in the physical layer of the transmitting side and the receiving side are physical downlink shared channel (PDSCH), physical uplink shared channel (PUSCH) and physical downlink control channel (PDCCH), which are control channels, It may be divided into a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a Physical Uplink Control Channel (PUCCH).

There are several layers in the second layer.

First, the medium access control (MAC) layer of the second layer serves to map various logical channels to various transport channels, and also logical channel multiplexing to map several logical channels to one transport channel. (Multiplexing). The MAC layer is connected to the upper layer RLC layer by a logical channel, and the logical channel includes a control channel for transmitting information of a control plane according to the type of information to be transmitted. It is divided into a traffic channel that transmits user plane information.

The Radio Link Control (RLC) layer of the second layer adjusts the data size so that the lower layer is suitable for transmitting data to the radio section by segmenting and concatenating data received from the upper layer. It plays a role.

The Packet Data Convergence Protocol (PDCP) layer of the second layer is an IP containing relatively large and unnecessary control information for efficient transmission in a wireless bandwidth where bandwidth is small when transmitting an IP packet such as IPv4 or IPv6. Performs Header Compression which reduces the packet header size. In addition, in the LTE system, the PDCP layer also performs a security function, which is composed of encryption (Ciphering) to prevent third-party data interception and integrity protection (Integrity protection) to prevent third-party data manipulation.

The radio resource control layer (hereinafter RRC) layer located at the top of the third layer is defined only in the control plane, and the configuration and resetting of radio bearers (abbreviated as RBs) are performed. It is responsible for the control of logical channels, transport channels and physical channels in relation to configuration and release. In this case, RB means a service provided by the second layer for data transmission between the terminal and the E-UTRAN.

If there is an RRC connection (RRC connection) between the RRC of the terminal and the RRC layer of the wireless network, the terminal is in the RRC connected mode (Connected Mode), otherwise it is in the RRC idle mode (Idle Mode).

Hereinafter, the RRC state and the RRC connection method of the UE will be described. The RRC state refers to whether or not the RRC of the UE is in a logical connection with the RRC of the E-UTRAN. If the RRC state is connected, the RRC_CONNECTED state is called, and the RRC_IDLE state is not connected. Since the UE in the RRC_CONNECTED state has an RRC connection, the E-UTRAN can grasp the existence of the UE in units of cells, and thus can effectively control the UE. On the other hand, the UE in the RRC_IDLE state cannot identify the existence of the UE by the E-UTRAN, and the core network manages the unit in a larger tracking area (TA) unit than the cell. That is, the terminal in the RRC_IDLE state is only detected whether the terminal exists in a larger area than the cell, and the terminal must transition to the RRC_CONNECTED state in order to receive a normal mobile communication service such as voice or data. Each TA is identified by a tracking area identity (TAI). The terminal may configure a TAI through a tracking area code (TAC), which is information broadcast in a cell.

When the user first turns on the power of the terminal, the terminal first searches for an appropriate cell, then establishes an RRC connection in the cell, and registers the terminal's information in the core network. Thereafter, the terminal stays in the RRC_IDLE state. The terminal staying in the RRC_IDLE state (re) selects a cell as needed and looks at system information or paging information. This is called camping on the cell. When it is necessary to establish an RRC connection, the UE staying in the RRC_IDLE state makes an RRC connection with the RRC of the E-UTRAN through an RRC connection procedure and transitions to the RRC_CONNECTED state. There are several cases in which a UE in RRC_IDLE state needs to establish an RRC connection. For example, a user's call attempt, a data transmission attempt, etc. are required or a paging message is received from E-UTRAN. Reply message transmission, and the like.

A non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

The following describes the NAS layer shown in FIG. 3 in detail.

ESM (evolved Session Management) belonging to the NAS layer performs functions such as default bearer management and dedicated bearer management, and is responsible for controlling the terminal to use the PS service from the network. The default bearer resource is characterized in that it is allocated from the network when it is connected to the network when it first accesses a specific Packet Data Network (PDN). At this time, the network allocates an IP address usable by the terminal so that the terminal can use the data service, and also allocates QoS of the default bearer. LTE supports two types of bearer having a guaranteed bit rate (GBR) QoS characteristic that guarantees a specific bandwidth for data transmission and reception, and a non-GBR bearer having a best effort QoS characteristic without guaranteeing bandwidth. In case of Default bearer, Non-GBR bearer is assigned. In the case of a dedicated bearer, a bearer having a QoS characteristic of GBR or non-GBR may be allocated.

The bearer allocated to the terminal in the network is called an evolved packet service (EPS) bearer, and when the EPS bearer is allocated, the network allocates one ID. This is called EPS Bearer ID. One EPS bearer has a QoS characteristic of a maximum bit rate (MBR) or / and a guaranteed bit rate (GBR).

5 is a flowchart illustrating a random access procedure in 3GPP LTE.

The random access procedure is used for the UE to get UL synchronization with the base station or to be allocated UL radio resources.

The UE receives a root index and a physical random access channel (PRACH) configuration index from the eNodeB. Each cell has 64 candidate random access preambles defined by a Zadoff-Chu (ZC) sequence, and the root index is a logical index for the UE to generate 64 candidate random access preambles.

Transmission of the random access preamble is limited to a specific time and frequency resource for each cell. The PRACH configuration index indicates a specific subframe and a preamble format capable of transmitting the random access preamble.

The UE sends the randomly selected random access preamble to the eNodeB. The UE selects one of the 64 candidate random access preambles. Then, the corresponding subframe is selected by the PRACH configuration index. The UE transmits the selected random access preamble in the selected subframe.

Upon receiving the random access preamble, the eNodeB sends a random access response (RAR) to the UE. The random access response is detected in two steps. First, the UE detects a PDCCH masked with random access-RNTI (RA-RNTI). The UE receives a random access response in a medium access control (MAC) protocol data unit (PDU) on the PDSCH indicated by the detected PDCCH.

6 shows a connection process in a radio resource control (RRC) layer.

As shown in FIG. 6, the RRC state is shown depending on whether the RRC is connected. The RRC state refers to whether or not an entity of the RRC layer of the UE is in a logical connection with an entity of the RRC layer of the eNodeB. When the RRC state is connected, the RRC state is referred to as an RRC connected state. The non-state is called the RRC idle state.

Since the UE in the connected state has an RRC connection, the E-UTRAN may determine the existence of the corresponding UE in units of cells, and thus may effectively control the UE. On the other hand, the UE in the idle state (idle state) can not be identified by the eNodeB, the core network (core network) is managed by the tracking area (Tracking Area) unit that is larger than the cell unit. The tracking area is a collection unit of cells. That is, the idle state (UE) is determined only in the presence of the UE in a large area, and in order to receive a normal mobile communication service such as voice or data, the UE must transition to the connected state (connected state).

When a user first powers up a UE, the UE first searches for an appropriate cell and then stays in an idle state in that cell. When the UE staying in the idle state needs to establish an RRC connection, the UE establishes an RRC connection with the RRC layer of the eNodeB through an RRC connection procedure and transitions to an RRC connected state. .

There are several cases in which the UE in the idle state needs to establish an RRC connection. For example, a user's call attempt or uplink data transmission is required, or a paging message is received from EUTRAN. In this case, the response message may be transmitted.

In order to establish an RRC connection with the eNodeB, the UE in an idle state must proceed with an RRC connection procedure as described above. The RRC connection process is largely a process in which a UE sends an RRC connection request message to an eNodeB, an eNodeB sends an RRC connection setup message to the UE, and a UE completes RRC connection setup to the eNodeB. (RRC connection setup complete) message is sent. This process will be described in more detail with reference to FIG. 6 as follows.

1) When a UE in idle mode attempts to establish an RRC connection due to a call attempt, a data transmission attempt, or a response to an eNodeB's paging, the UE first sends an RRC connection request message. Send to eNodeB.

2) When the RRC connection request message is received from the UE, the eNB accepts the RRC connection request of the UE when the radio resources are sufficient, and transmits an RRC connection setup message, which is a response message, to the UE. .

3) When the UE receives the RRC connection setup message, it transmits an RRC connection setup complete message to the eNodeB. When the UE successfully transmits an RRC connection establishment message, the UE establishes an RRC connection with the eNodeB and transitions to the RRC connected mode.

In the conventional EPC, the MME is divided into a core access and mobility management function (AMF) and a session management function (SMF) in a next generation system (or 5G CN). The NAS interaction and mobility management (MM) with the UE are performed by the AMF, and the session management (SM) is performed by the SMF. In addition, the SMF manages a user plane function (UPF), which has a user-plane function, that is, a gateway for routing user traffic. The SMF is responsible for the control-plane portion of the S-GW and the P-GW in the conventional EPC. The user-plane part can be considered to be in charge of the UPF. There may be one or more UPFs between the RAN and the DN for the routing of user traffic. That is, the conventional EPC may be configured as illustrated in FIG. 7 at 5G. In addition, as a concept corresponding to the PDN connection in the conventional EPS, a PDU (Protocol Data Unit) session is defined in the 5G system. The PDU session refers to an association between the UE and the DN providing the PDU connectivity service of the Ethernet type or the unstructured type as well as the IP type. In addition, UDM (Unified Data Management) performs a function corresponding to the HSS of the EPC, PCF (Policy Control Function) performs a function corresponding to the PCRF of the EPC. Of course, the functions can be provided in an expanded form to satisfy the requirements of the 5G system. For details on the 5G system architecture, each function and each interface, TS 23.501 is applicable.

Recently, as an efficient data transmission method targeting IoT terminals, a connection (CL) data transmission solution has been discussed. In this solution, in case of a terminal that transmits a small amount of data intermittently, the RAN and CN (Core Network) exchange a large amount of signaling to send a small amount of data so that the user plane is connected between the RAN and the CN to send data. Instead, it allows a connectionless UE to send data to and to the UE. For basic information regarding such CL mode transmission, refer to 6.4.8.1 Solution Overview of the 3GPP TR 23.799 document, which is referred to as a prior art of the present invention.

8 shows a structure for CL mode transmission, which is composed of network elements such as a UE, a Radio Access Network (RAN), a User plane Gateway (UPGW), a Core control plane (Core CP), and the like.

On the other hand, the user plane protocol stack is derived from the basic connection-oriented protocol stack with the following additions.

CLS UPL (ConnectionLess Service User Plane) layer: This layer, placed between the IP and the access layer, connects the UE and the UPGW, and protects encryption and integrity between the UE and the network, including PDU session identification in the RAN and UPGW, and the air interface section. To provide. The CLS UP layer supports avoiding packet duplication (sequence numbering).

Generic Routing Encapsulation (tunnel protocol) (GRE): GRE is an example protocol that can be used for tunneling. Other tunneling protocols may be used.

The following layers are defined by the RAN group.

(NG-) RLC: Radio control sublayer (responsible for segmentation and ARQ).

(NG-) MAC: Media Access control (responsible for connectionless access and HARQ).

-(NG-) PHY: Physical Access.

9 shows a downlink CL data transmission procedure. In this regard, the procedures for setting up CL mode data transmission PDU sessions, CL uplink data transmission, paging for CL data transmission UEs, etc. are described in Sections 6.4.8.2.3.1, 6.4.8.2.3.2, 3GPP TR 23.799, See section 6.4.8.2.3.4, which is referred to in the prior art of the present invention. In the following description, UPGW CL Service Information (UCLSI) is an identifier used by the UE, RAN and UPGW to identify a PDU session with CL mode data transmission on the RAN and core interface. This identifier includes the identifier of the UPGW serving the PDU session and the local identifier for the particular PDU session for the particular UE. The RAN uses UCLSI to derive a UPGW that must process data exchanged with the UE. The UE may be assigned one or more UCLSI on one or more UPGWs.

Subsequently, each procedure will be described in detail with reference to FIG. 9. In FIG. 9, it is assumed that the UE is already attached to the network and authenticated and has obtained a master authentication key. In step S901, the core UPGW receives downlink incoming data (PDU). In step S902, the UPGW searches for the corresponding UCLSI. If UCLSI is marked as REACHABLE, UPGW uses the last known RAN to service this UCLSI. The UPGW compresses the IP header if necessary, encrypts the data, and then passes the data and UCLSI over the appropriate downlink RAN transport interface to UCLSI. UPGW restarts the UE location freshness timer for UCLSI. If UCLSI is marked as IDLE, UPGW drops the packet or starts network paging. This behavior is controlled by the policy received from the Core Control Plane (ie, Session Management). If network paging is required, the UPGW sends a paging request for UCLSI to the core CP, buffers the data, and starts a paging timer. The core CP triggers the corresponding paging by the RAN. If a page response from the UE arrives before the paging timer expires, the UPGW learns the current RAN serving the UE and forwards the data over this RAN.

In step S903 (assuming UCLSI is marked REACHABLE), the UPGW transmits data and UCLSI via the appropriate downlink RAN transport interface to UCLSI. For any downlink received data, the RAN matches the downlink UCLSI. If UCLSI is known by the RAN, the RAN sends data to the UE. Here, if the UE transmission is successful, the RAN restarts the UE location freshness timer for UCLSI. Or if the UE transmission fails, the RAN discards the packet, sends a NACK to the UPGW, and deletes the context for the UCLSI. If UCLSI is not known by the RAN (eg the RAN previously failed to transmit to the UE), the RAN drops the data and sends a NACK to the UPGW. When UPGW receives a NACK from the RAN (for example, UCLSI is known but transmission fails or UCLSI is unknown), UPGW clears the UPGW UE location freshness timer and marks UCLSI as IDLE (UCLSI no longer works with the RAN node). Not associated).

In step S904, the RAN sends CL data to the UE.

In step S905, upon receiving the CL data, the UE processes the data (reconstructs, decrypts, etc.) and then forwards the data to the application and sends an uplink grant. The UE resets the UE location freshness timer.

If the UPGW UE freshness timer for UCLSI expires, UPGW displays UCLSI as IDLE. If the RAN UE freshness timer for UCLSI expires, the RAN deletes the UCLSI. If the UE freshness timer for UCLSI expires or the UE reselects a new cell, the UE returns to the CL idle state and stops monitoring downlink channels for data reception.

As shown in FIG. 9, when the UPGW receives DL data, the UPGW transmits the DL data to the appropriate RAN. When the RAN receives this and knows the UCLSI, that is, it has a context for the target UE of the DL data (more specifically, the context for the PDU session of the UE), the RAN transmits it to the UE. If it transmits to the UE but fails, the RAN drops this data and sends a NACK to the UPGW that sent it, and the UPGW deletes the context for the UCLSI (ie, the associated PDU session). In addition, UPGW marks that the UCLSI of the UE is "IDLE". That is, when the RAN node information about the UCLSI of the UE is deleted, when the DL data is received, when the UCLSI is marked as 'IDLE', for example, the packet is deleted instead of transmitting data to the previous RAN. Perform the corresponding action.

However, one UE may have a plurality of PDU sessions, and a plurality of UCLSIs may be allocated to one UE. In addition, one UPGW may be allocated for a plurality of PDU sessions or a plurality of UPGWs may be allocated. UPGW manages the state (state, REACHABLE or IDLE) for each UCLSI. As described above, if the RAN sends a NACK to the UPGW after a data transmission failure to the UE, the UPGW changes its UCLSI to the IDLE state. However, when the UPGW receiving the NACK maintains another REACHABLE marked UCLSI context for the UE, or when another UPGW of the UE maintains the REACHABLE marked UCLSI context, the UPGW is received when DL data to the UE is received. Has a problem of forwarding DL data to the RAN which has already failed transmission. This not only causes unnecessary data transmission from the CN to the RAN, but also once the data has been transmitted to the RAN, it can no longer be delivered to the UE because the RAN drops the corresponding data. Therefore, the following describes an efficient CL data transmission failure handling method that can solve this problem.

Core CP Operation-oriented Embodiments

The RAN receives DL data from the UPGW and transmits it to the UE, but fails. In this case, the core CP receives first information from the RAN indicating that the UE is unreachable. The transmission of the first information may always be performed or may be performed only when the RAN has different UCLSI for the corresponding UE and then has another UCLSI. The core CP may transmit second information indicating that the UE is unreachable to all UPGWs associated with the UE. The UPGW (s) receiving this will change all UCLSI for the UE to the IDLE state. That is, the second information may be an indication that the UPGW receiving the second information changes all UCLSI for the UE to the IDLE state. Through this operation of the core CP, it is possible to solve the unnecessary repetitive transmission problem to the RAN that has already failed transmission described above.

Specifically, the (unique) UPGW of the UE may have two UCLSI whose state is REACHABLE for the UE, wherein the first information is received when at least one of the two or more UCLSI is changed to the IDLE state It may be. In this case, according to the prior art, even if one UCLSI is changed to the IDLE state due to a transmission failure, data transmission to the RAN which failed to be transmitted may occur again because of the UCLSI in the remaining REACHABLE state. Even in this case, since the core CP instructs all UPGWs related to the UE to change all UCLSI for the UE to the IDLE state, unnecessary transmission to the RAN does not occur. Optionally, the second information may be transmitted if the (unique) UPGW of the UE has two UCLSI whose status is REACHABLE for the UE.

In another case, each of the two or more UPGWs of the UE has at least one UCLSI having a status of REACHABLE for the UE, and the first information is UCLSI for the UE that has at least one UPGW of the two or more UPGWs. May be received when IDLE is changed to the IDLE state. In this case, according to the related art, UCLSI may be marked as IDLE in one UPGW, and thus data transmission may be performed to a RAN that has failed to transmit due to UCLSI REACHABLE in another UPGW. Even in such a case, according to the embodiment, since the core CP instructs all UPGWs related to the UE to change all UCLSI for the UE to the IDLE state, unnecessary transmission to the RAN does not occur. Optionally, the second information may be transmitted when each of the two or more UPGWs of the UE has at least one UCLSI whose status is REACHABLE for the UE.

As such, the operation of notifying the core CP that the UE is unreachable may be performed together with the operation of transmitting the NACK to the UPGW having transmitted the DL data, or may be performed without replacing the NACK (that is, replacing it). . When the RAN transmits the NACK, the first information may be omitted from the UPGW that receives the NACK. In this case, the UPGW receiving the NACK from the RAN may be set to change all UCLSI for the UE to an ILDE state.

The core CP may be composed of one or more of an MM CP function, an SM CP function, a function having subscriber information, and a function for managing SM information of the UE.

UPGW operation-oriented embodiment

When the UPGW forwards DL data to the RAN and then receives a NACK from the RAN, the UPGW checks whether there is another UCLSI other than the UCLSI corresponding to the NACK (this means a PDU session associated therewith) for the UE. If there is another UCLSI and the state is REACHABLE, it is changed to IDLE and marked.

Alternatively, if the UPGW forwards DL data to the RAN and then receives a NACK from the RAN, it may inform the core CP that this UE is IDLE. Here, the IDLE may mean that the RAN of the UE is no longer valid / available. The fact that the UE is IDLE may mean that the UE is unreachable. As such, the UPGW notifying the core CP that the UE is IDLE may be performed i) always or ii) the core CP may be instructed by the UPGW. In the case of ii), the core CP may select and instruct the UPGW during the PDU session setup procedure, and may direct the UPGW at any time after the PDU session setup procedure. This indication may always occur, and may indicate to all UPGWs related to the UE when a second PDU session is setup for the UE. The operation of instructing the core CP to inform the UPGW of the unreachability of the UE may be interpreted as "unreachability notification service subscription," and the operation of the UPGW informing the core CP of the unreachability of the UE may be interpreted as "unreachability notification."

Upon receiving the IDLE, the core CP notifies the UPGW (s) maintaining the UCLSI for the UE, indicating that the UE is IDLE. This is ultimately to cause UPGW to change IDLE if UCLSI's status is REACHABLE. The UPGW (s) may include but not include UPGW which informs the core CP that the UE is IDLE.

In the above description, when a plurality of UPGWs exist for one UE, each UPGW may be controlled by a different session management (SM) CP function. In this case, when the UPGW informs the SM CP function controlling itself of the UE's unreachability, this notification / notified information is a) transferred to another SM CP function through the Mobility Management (MM) CP function of the UE to the UPGW controlled. B) a connection between SM CP functions, which is transferred to a different SM CP function, and then transferred to a controlled UPGW, or c) a function having subscriber information (a function serving HSS) or SM information of a UE. The function may be transferred to another UPGW controlled by being transferred to another SM CP function. In other words, the core CP may be considered to be a collective of all functions that are responsible for such a control plane function.

RAN operation-oriented embodiment

The UPGW forwards DL data to the RAN and then receives a NACK from the RAN. In this case, the RAN checks whether it has another UCLSI for the UE. If the RAN has another UCLSI for the UE, a message indicating that the UE is IDLE is transmitted to a corresponding UPGW.

Here, that the UE is IDLE may mean that the RAN of the UE is no longer valid / available. Alternatively, the UE being IDLE may mean that the UE is unreachable. When sending such a message, if the corresponding UPGW (ie, the UPGW associated with another UCLSI) is the same as the UPGW that sent the NACK, then the message may not be sent to this UPGW, and this IDLE is given to all corresponding UPGWs without this consideration. You can also send a message.

The UPGW receiving the message indicating that the UE is IDLE from the RAN marks the IDLE when the state of the corresponding UCLSI context of the UE is REACHABLE.

In each of the above-described embodiments, the core CP may be configured with one or more of a MM CP function, an SM CP function, a function having subscriber information (function performing HSS), and a function for managing SM information of the UE. . For example, the core CP to which the RAN sends a message may be an MM CP function (or AMF: Access and Mobility Management Function). In this case, the MM CP function that has received information that the UE is unreachable from the RAN may transmit it to the UPGW (or UPF: User Plane Function) through the SM CP function (or SMF: Session Management Function). This means that the CN function receiving the information from the RAN may ultimately go through a number of related functions to send this information to the UPGW.

10 is a diagram showing the configuration of a preferred embodiment of a terminal device and a network node device according to an example of the present invention.

The terminal device 100 according to the present invention with reference to FIG. 10 may include a transceiver 110, a processor 120, and a memory 130. The transceiver 110 may be configured to transmit various signals, data and information to an external device, and to receive various signals, data and information to an external device. The terminal device 100 may be connected to an external device by wire and / or wirelessly. The processor 120 may control the overall operation of the terminal device 100, and may be configured to perform a function of the terminal device 100 to process and process information to be transmitted and received with an external device. The memory 130 may store the processed information for a predetermined time and may be replaced with a component such as a buffer (not shown). In addition, the processor 120 may be configured to perform a terminal operation proposed in the present invention.

Referring to FIG. 10, the network node device 200 according to the present invention may include a transceiver 210, a processor 220, and a memory 230. The transceiver 210 may be configured to transmit various signals, data and information to an external device, and to receive various signals, data and information to an external device. The network node device 200 may be connected to an external device by wire and / or wirelessly. The processor 220 may control the overall operation of the network node device 200, and may be configured to perform a function of calculating and processing information to be transmitted / received with an external device. The memory 230 may store the processed information for a predetermined time and may be replaced with a component such as a buffer (not shown). In addition, the processor 220 may be configured to perform the network node operation proposed in the present invention. In detail, the processor 220 receives the first information from the radio access network (RAN) by the core CP through the transmitting / receiving apparatus, and the core CP informs all UPGWs of the UE that the UE is unreachable. Second information indicating the unreachable may be transmitted through the transceiver.

In addition, the specific configuration of the terminal device 100 and the network device 200 as described above, may be implemented so that the above-described matters described in various embodiments of the present invention can be applied independently or two or more embodiments are applied at the same time, overlapping The description is omitted for clarity.

Embodiments of the present invention described above may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

For implementation in hardware, a method according to embodiments of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), and Programmable Logic Devices (PLDs). It may be implemented by field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of an apparatus, procedure, or function for performing the above-described functions or operations. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable any person skilled in the art to make and practice the invention. Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Various embodiments of the present invention as described above have been described with reference to the 3GPP system, but may be applied to various mobile communication systems in the same manner.

Claims (15)

1. A method of supporting a CL (ConnectionLess) service in a core control plane (CP) in a wireless communication system,

   Receiving, by the core CP, first information indicating that the UE is unreachable from a radio access network (RAN); And

   Sending, by the core CP, all of the UPGWs associated with the UE to the second information informing that the UE is unreachable;

   Including, CL service support method.
2. The method of claim 1,

   And the second information is an instruction for the UPGW to receive the second information to change all UCLSI (UPGW ConnectionLess Service Information) for the UE to IDLE state.
3. The method of claim 1,

   The UPGW of the UE has two UCLSI whose status is REACHABLE for the UE.
4. The method of claim 3,

   And the first information is received when at least one of the two or more UCLSI is changed to an IDLE state.
5. The method of claim 1,

   The second information is transmitted when the UPGW of the UE has two UCLSI whose status is REACHABLE for the UE.
6. The method of claim 5,

   And the first information is received when at least one of the two or more UCLSI is changed to an IDLE state.
7. The method of claim 1,

   Wherein each of the two or more UPGWs of the UE has at least one UCLSI with a status of REACHABLE for the UE.
8. The method of claim 1,

   The first information is received when the UCLSI for the UE of the at least one UPGW of the two or more UPGW is changed to the IDLE state, CL service support method.
9. The method of claim 1,

   The second information is transmitted when each of the two or more UPGWs of the UE has at least one UCLSI whose status is REACHABLE for the UE.
10. The method of claim 9,

    The first information is received when the UCLSI for the UE of the at least one UPGW of the two or more UPGW is changed to the IDLE state, CL service support method.
11. The method of claim 1,

    The first information is transmitted when the RAN transmits a NACK to the UPGW.
12. The method of claim 11,

    If the RAN transmits a NACK, the first information is omitted transmission to the UPGW receiving the NACK.
13. The method of claim 12,

    The UPGW receiving the NACK changes all UCLSI for the UE to an ILDE state.
14. The method of claim 1,

    The core CP is composed of one or more of MM CP function, SM CP function, a function having subscriber information, a function for managing the SM information of the UE,
15. In a core control plane (CP) device supporting a CL (ConnectionLess) service in a wireless communication system,

    A transceiver; And

    Includes a processor,

    The processor is configured to receive, via the transceiver, first information indicating that the UE is unreachable from a radio access network (RAN) by the core CP, and the core CP notifies all UPGWs associated with the UE that the UE is unreachable. A core CP device for transmitting 2 information through the transceiver.

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