WO2016064201A1 - Pdn type fallback method in wireless communication system and apparatus therefor - Google Patents

Abstract

Disclosed are a PDN type fallback method in a wireless communication system and an apparatus therefor. Specifically, a method for performing fallback from a first packet data network (PDN) type, in which a fault has occurred, to a second PDN type, which is capable of a normal operation, by a home subscriber server (HSS) in a wireless communication system may comprise the steps of: detecting the occurrence of the fault of the first PDN type and then, when there is user equipment (UE) to/from which a voice call is transmitted/received, determining whether all PDN types allocated for a PDN connection established preferentially by the UE is the first PDN type; determining one of a detach with re-attach procedure and a disconnection with re-activation procedure according to whether all the PDN types allocated for the PDN connection of the UE are the first PDN type; and starting the determined procedure.

Description

PDN type fallback method in wireless communication system and apparatus therefor

The present invention relates to a wireless communication system, and more particularly, to a method for performing or supporting a fallback of a PDN type to a PDN type capable of normal operation of a failed PDN type. It is about supporting devices.

Mobile communication systems have been developed to provide voice services while ensuring user activity. However, the mobile communication system has expanded not only voice but also data service.As a result of the explosive increase in traffic, a shortage of resources and users are demanding higher speed services, a more advanced mobile communication system is required. have.

The requirements of the next generation of mobile communication systems will be able to accommodate the explosive data traffic, dramatically increase the data rate per user, greatly increase the number of connected devices, very low end-to-end latency, and high energy efficiency. It should be possible. Dual connectivity, Massive Multiple Input Multiple Output (MIMO), In-band Full Duplex, Non-Orthogonal Multiple Access (NOMA), Super Various technologies such as wideband support and device networking have been studied.

An object of the present invention is to propose a method for falling back a PDN type from a failed PDN type to a PDN type capable of normal operation.

It is also an object of the present invention to propose a method for determining a procedure for falling back a PDN type by comparing a PDN type allocated in a PDN connection established to a terminal with a failed PDN type.

In addition, a PDN type fallback method for smoothly serving voice call transmission / reception services is proposed.

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 aspect of the present invention, a Home Subscriber Server (HSS) in a wireless communication system falls back to a second PDN type capable of normal operation from a failure of a first Packet Data Network (PDN) type. In the method for fallback, after detecting the occurrence of the failure of the first PDN type, if there is a terminal with voice call (voice call) transmission and reception, PDN allocated for the PDN connection established by the terminal preferentially Determining whether all of the types are the first PDN type, Detach with re-attach procedure with re-attachment depending on whether all the PDN types allocated to the PDN connection of the terminal is the first PDN type Or determining any one of a disconnection with re-activation procedure involving the re-activation and initiating the determined procedure.

According to another aspect of the present invention, a home subscribe server (HSS) for falling back a failed Packet Data Network (PDN) type to a second PDN type capable of normal operation in a wireless communication system (HSS) A Home Subscriber Server, comprising: a communication module for transmitting and receiving signals and a processor for controlling the communication module, wherein the processor detects a failure of the first PDN type and then voices a voice call. call) When there is a terminal having transmission and reception, it is first determined whether all of the PDN types allocated for the PDN connection established by the terminal are the first PDN type, and all of the PDN types assigned to the PDN connection of the terminal are all Depending on whether it is a first PDN type, either a Detach with re-attach procedure or a Disconnection with re-activation procedure. Determine, and may be configured to initiate the determined procedure.

Preferably, when all of the PDN types allocated to the PDN connection of the UE are the first PDN type, a detach with re-attach procedure may be determined.

Preferably, the mobility management entity sends a Cancel Location message including an HSS initiated detach or an IP version change or a PDN type change as a cause value. (MME: Mobility Management Entity).

Preferably, the MME may belong to a Visited Public Land Mobile Network (VPLMN).

Preferably, the Cancel Location message may indicate the first PDN type as a PDN type in which a failure occurs, or indicate the second PDN type as a PDN type in which normal operation is possible.

Preferably, during the attach procedure by the terminal, the terminal may be connected to a PDN GW (Packet Data Network Gateway) for allocating the second PDN type by the MME.

Preferably, when all of the PDN types allocated to the PDN connection of the UE are not the first PDN type, a disconnection with re-activation procedure for the PDN to which the first PDN type is assigned Can be determined.

Preferably, a PDN disconnect request including a relocation message or a Cancel Location message containing a bearer deactivation with reactivation requested with a cause value ( A PDN disconnection request (PDN) message may be transmitted to a mobility management entity (MME).

Preferably, the MME may belong to a Visited Public Land Mobile Network (VPLMN).

Preferably, the Cancel Location message may indicate the first PDN type as a PDN type in which a failure occurs, or indicate the second PDN type as a PDN type in which normal operation is possible.

Preferably, the terminal may be connected to a PDN Packet Data Network Gateway (GW) that allocates the second PDN type by the MME during a PDN connectivity procedure by the terminal.

According to an embodiment of the present invention, the mobile communication service can be smoothly performed by falling back the PDN type to the PDN type capable of normal operation from the failed PDN type.

In addition, according to an embodiment of the present invention, the PDN type fallback procedure may be more efficiently performed by determining a procedure of falling back a PDN type suitable for a terminal.

In addition, the voice call transmission and reception service may be smoothly provided by first falling back the terminal where the voice call is generated.

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

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide embodiments of the present invention and together with the description, describe the technical features of the present invention.

1 is a view briefly illustrating an EPS (Evolved Packet System) to which the present invention can be applied.

2 shows an example of a network structure of an evolved universal terrestrial radio access network (E-UTRAN) to which the present invention can be applied.

3 illustrates the structure of an E-UTRAN and an EPC in a wireless communication system to which the present invention can be applied.

4 shows a structure of a radio interface protocol between a terminal and an E-UTRAN in a wireless communication system to which the present invention can be applied.

5 shows an S1 interface protocol structure in a wireless communication system to which the present invention can be applied.

6 is a diagram exemplarily illustrating a structure of a physical channel in a wireless communication system to which the present invention can be applied.

7 is a diagram illustrating EMM and ECM states in a wireless communication system to which the present invention can be applied.

8 illustrates a bearer structure in a wireless communication system to which the present invention can be applied.

FIG. 9 is a diagram illustrating a transmission path of a control plane and a user plane in an EMM registered state in a wireless communication system to which the present invention can be applied.

10 is a diagram for explaining a contention based random access procedure in a wireless communication system to which the present invention can be applied.

11 is a diagram briefly illustrating an attach procedure in a wireless communication system to which the present invention may be applied.

12 is a diagram illustrating a UE requested PDN connectivity procedure in a wireless communication system to which the present invention can be applied.

FIG. 13 is a diagram illustrating a method for informing a HSS of a PDN type according to an embodiment of the present invention. FIG.

14 is a diagram illustrating a PDN type fallback method according to an embodiment of the present invention.

15 is a diagram illustrating a PDN type fallback method according to an embodiment of the present invention.

16 is a diagram illustrating a PDN type fallback method according to an embodiment of the present invention.

17 and 18 illustrate a block diagram of a communication device according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

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 this specification, a base station has a meaning as a terminal node of a network that directly communicates with a terminal. The specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases. That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. A 'base station (BS)' may be replaced by terms such as a fixed station, a Node B, an evolved-NodeB (eNB), a base transceiver system (BTS), an access point (AP), and the like. . In addition, a 'terminal' may be fixed or mobile, and may include a user equipment (UE), a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), and an AMS ( Advanced Mobile Station (WT), Wireless Terminal (WT), Machine-Type Communication (MTC) Device, Machine-to-Machine (M2M) Device, Device-to-Device (D2D) Device, etc.

Hereinafter, downlink (DL) means communication from a base station to a terminal, and uplink (UL) means communication from a terminal to a base station. In downlink, a transmitter may be part of a base station, and a receiver may be part of a terminal. In uplink, a transmitter may be part of a terminal and a receiver may be part of a base station.

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.

The following techniques are code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and NOMA It can be used in various radio access systems such as non-orthogonal multiple access. CDMA may be implemented by a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA). UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (advanced) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802, 3GPP and 3GPP2. 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.

For clarity, the following description focuses on 3GPP LTE / LTE-A, but the technical features of the present invention are not limited thereto.

Terms that can be 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 consisting of an Evolved Packet Core (EPC), which is a packet switched core network based on Internet Protocol (IP), and an access network such as LTE and UTRAN. UMTS is an evolutionary network.

NodeB: base station of UMTS network. It is installed outdoors and its coverage is macro cell size.

eNodeB: base station of EPS network. It is installed outdoors and its coverage is macro cell size.

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

IMS (IP Multimedia Subsystem): A subsystem for providing multimedia services based on IP.

International Mobile Subscriber Identity (IMSI): An internationally uniquely assigned user identifier in a mobile communications network.

Machine Type Communication (MTC): Communication performed by a machine without human intervention. It may also be referred to as M2M (Machine to Machine) communication.

MTC terminal (MTC UE or MTC device or MTC device): a terminal having a communication function through a mobile communication network and performing an MTC function (for example, a vending machine, a meter reading device, etc.).

MTC server: A server on a network that manages an MTC terminal. It may exist inside or outside the mobile communication network. It may have an interface that an MTC user can access. In addition, the MTC server may provide MTC related services to other servers (Services Capability Server (SCS)), or the MTC server may be an MTC application server.

(MTC) application: services (e.g., remote meter reading, volume movement tracking, weather sensors, etc.)

(MTC) application server: a server on a network where (MTC) applications run

MTC feature: A function of a network to support an MTC application. For example, MTC monitoring is a feature for preparing for loss of equipment in an MTC application such as a remote meter reading, and low mobility is a feature for an MTC application for an MTC terminal such as a vending machine.

MTC subscriber: An entity having a connection relationship with a network operator and providing a service to one or more MTC terminals.

MTC group: A group of MTC terminals that share at least one MTC feature and belongs to an MTC subscriber.

Services Capability Server (SCS): An entity for communicating with an MTC InterWorking Function (MTC-IWF) and an MTC terminal on a Home PLMN (HPLMN), which is connected to a 3GPP network.

External Identifier: An identifier used by an external entity (e.g., an SCS or application server) of a 3GPP network to point to (or identify) an MTC terminal (or a subscriber to which the MTC terminal belongs). Globally unique. The external identifier is composed of a domain identifier and a local identifier as follows.

Domain Identifier: An identifier for identifying a domain in a control term of a mobile communication network operator. One provider may use a domain identifier for each service to provide access to different services.

Local Identifier: An identifier used to infer or obtain an International Mobile Subscriber Identity (IMSI). Local identifiers must be unique within the application domain and are managed by the mobile telecommunications network operator.

RAN (Radio Access Network): a unit including a Node B, a Radio Network Controller (RNC), and an eNodeB controlling the Node B in a 3GPP network. It exists at the terminal end and provides 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.

RANAP (RAN Application Part): between the RAN and the node in charge of controlling the core network (ie, Mobility Management Entity (MME) / Serving General Packet Radio Service (GPRS) Supporting Node) / MSC (Mobile Switching Center) Interface.

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.

Non-Access Stratum (NAS): A functional layer for transmitting and receiving signaling and traffic messages between a terminal and a core network in a UMTS and EPS protocol stack. The main function is to support the mobility of the terminal and to support the session management procedure for establishing and maintaining an IP connection between the terminal and the PDN GW.

Hereinafter, the present invention will be described based on the terms defined above.

General system to which the present invention can be applied

1 is a diagram briefly illustrating an EPS (Evolved Packet System) to which the present invention may be applied.

The network structure diagram of FIG. 1 briefly reconstructs a structure of an EPS (Evolved Packet System) including an Evolved Packet Core (EPC).

Evolved Packet Core (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 improved data transfer capability.

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), the IP-based base station (for example, eNodeB (evolved Node B)), EPC, application domain (for example, IMS) It can be configured through. 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) (or S-GW), PDN GW (Packet Data Network Gateway) (or PGW or P-GW), A mobility management entity (MME), a Serving General Packet Radio Service (GPRS) Supporting Node (SGSN), and an enhanced Packet Data Gateway (ePDG) are shown.

The SGW 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 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. Also, untrusted networks such as 3GPP networks and non-3GPP networks (e.g., Interworking Wireless Local Area Networks (I-WLANs), trusted divisions such as Code Division Multiple Access (CDMA) networks or Wimax). It can serve as an anchor point for mobility management with the network.

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 for supporting access to a network connection, allocation of network resources, tracking, paging, roaming, handover, and the like. The MME controls the 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 includes 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. For example, 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, various reference points may exist according to the network structure.

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 relevant control and mobility resources 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 the PDN GW.

2 shows an example of a network structure of an evolved universal terrestrial radio access network (E-UTRAN) to which the present invention can be applied.

The E-UTRAN system is an evolution from the existing UTRAN system and may be, for example, a 3GPP LTE / LTE-A system. Communication networks are widely deployed to provide various communication services, such as voice (eg, Voice over Internet Protocol (VoIP)) over IMS and packet data.

Referring to FIG. 2, an E-UMTS network includes an E-UTRAN, an EPC, and one or more UEs. The E-UTRAN consists of eNBs providing a control plane and a user plane protocol to the UE, and the eNBs are connected through an X2 interface.

X2 user plane interface (X2-U) is defined between eNBs. The X2-U interface provides non guaranteed delivery of user plane packet data units (PDUs). An X2 control plane interface (X2-CP) is defined between two neighboring eNBs. X2-CP performs functions such as context transfer between eNBs, control of user plane tunnel between source eNB and target eNB, delivery of handover related messages, and uplink load management.

The eNB is connected to the terminal through a wireless interface and is connected to an evolved packet core (EPC) through the S1 interface.

The S1 user plane interface (S1-U) is defined between the eNB and the serving gateway (S-GW). The S1 control plane interface (S1-MME) is defined between the eNB and the mobility management entity (MME). The S1 interface performs an evolved packet system (EPS) bearer service management function, a non-access stratum (NAS) signaling transport function, network sharing, and MME load balancing function. The S1 interface supports a many-to-many-relation between eNB and MME / S-GW.

MME provides NAS signaling security, access stratum (AS) security control, inter-CN inter-CN signaling to support mobility between 3GPP access networks, and performing and controlling paging retransmission. IDLE mode UE accessibility, tracking area identity (TAI) management (for children and active mode terminals), PDN GW and SGW selection, MME for handover with MME changes Public warning system (PWS), bearer management capabilities including optional, SGSN selection for handover to 2G or 3G 3GPP access networks, roaming, authentication, dedicated bearer establishment System (including Earthquake and Tsunami Warning System (ETWS) and Commercial Mobile Alert System (CMAS)) support for message transmission. Can.

3 illustrates the structure of an E-UTRAN and an EPC in a wireless communication system to which the present invention can be applied.

Referring to FIG. 3, an eNB may select a gateway (eg, MME), route to the gateway during radio resource control (RRC) activation, scheduling of a broadcast channel (BCH), and the like. Dynamic resource allocation to the UE in transmission, uplink and downlink, and may perform the function of mobility control connection in the LTE_ACTIVE state. As mentioned above, within the EPC, the gateway is responsible for paging initiation, LTE_IDLE state management, ciphering of the user plane, System Architecture Evolution (SAE) bearer control, and NAS signaling encryption. It can perform the functions of ciphering and integrity protection.

4 shows a structure of a radio interface protocol between a terminal and an E-UTRAN in a wireless communication system to which the present invention can be applied.

FIG. 4 (a) shows the radio protocol structure for the control plane and FIG. 4 (b) shows the radio protocol structure for the user plane.

Referring to FIG. 4, the layers of the air interface protocol between the terminal and the E-UTRAN are based on the lower three layers of the open system interconnection (OSI) standard model known in the art of communication systems. It may be divided into a first layer L1, a second layer L2, and a third layer L3. The air interface protocol between the UE and the E-UTRAN consists of a physical layer, a data link layer, and a network layer horizontally, and vertically stacks a protocol stack for transmitting data information. (protocol stack) It is divided into a user plane and a control plane, which is a protocol stack for transmitting control signals.

The control plane refers to a path through which control messages used by the terminal and the network to manage a call are transmitted. The user plane refers to a path through which data generated at an application layer, for example, voice data or Internet packet data, is transmitted. Hereinafter, each layer of the control plane and the user plane of the radio protocol will be described.

A physical layer (PHY), which is a first layer (L1), provides an information transfer service to a higher layer by using a physical channel. The physical layer is connected to a medium access control (MAC) layer located at a higher level through a transport channel, and data is transmitted between the MAC layer and the physical layer through the transport channel. Transport channels are classified according to how and with what characteristics data is transmitted over the air interface. In addition, data is transmitted between different physical layers through a physical channel between a physical layer of a transmitter and a physical layer of a receiver. The physical layer is modulated by an orthogonal frequency division multiplexing (OFDM) scheme and utilizes time and frequency as radio resources.

There are several physical control channels used at the physical layer. A physical downlink control channel (PDCCH) is a resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH) and uplink shared channel (UL-SCH) to the UE. : informs hybrid automatic repeat request (HARQ) information related to uplink shared channel (HARQ). In addition, the PDCCH may carry an UL grant that informs the UE of resource allocation of uplink transmission. The physical control format indicator channel (PDFICH) informs the UE of the number of OFDM symbols used for PDCCHs and is transmitted every subframe. A physical HARQ indicator channel (PHICH) carries a HARQ acknowledgment (ACK) / non-acknowledge (NACK) signal in response to uplink transmission. The physical uplink control channel (PUCCH) carries uplink control information such as HARQ ACK / NACK, downlink request and channel quality indicator (CQI) for downlink transmission. A physical uplink shared channel (PUSCH) carries a UL-SCH.

The MAC layer of the second layer (L2) provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. In addition, the MAC layer multiplexes / demultiplexes into a transport block provided as a physical channel on a transport channel of a MAC service data unit (SDU) belonging to the logical channel and mapping between the logical channel and the transport channel. Includes features

The RLC layer of the second layer (L2) supports reliable data transmission. Functions of the RLC layer include concatenation, segmentation, and reassembly of RLC SDUs. In order to guarantee the various quality of service (QoS) required by the radio bearer (RB), the RLC layer has a transparent mode (TM), an unacknowledged mode (UM) and an acknowledgment mode (AM). There are three modes of operation: acknowledge mode. AM RLC provides error correction through an automatic repeat request (ARQ). Meanwhile, when the MAC layer performs an RLC function, the RLC layer may be included as a functional block of the MAC layer.

The packet data convergence protocol (PDCP) layer of the second layer (L2) performs user data transmission, header compression, and ciphering functions in the user plane. Header compression is relatively large and large in order to allow efficient transmission of Internet protocol (IP) packets, such as IPv4 (internet protocol version 4) or IPv6 (internet protocol version 6), over a small bandwidth wireless interface. It means the function to reduce the IP packet header size that contains unnecessary control information. The function of the PDCP layer in the control plane includes the transfer of control plane data and encryption / integrity protection.

A radio resource control (RRC) layer located at the lowest part of the third layer L3 is defined only in the control plane. The RRC layer serves to control radio resources between the terminal and the network. To this end, the UE and the network exchange RRC messages with each other through the RRC layer. The RRC layer controls the logical channel, transport channel and physical channel with respect to configuration, re-configuration and release of radio bearers. The radio bearer means a logical path provided by the second layer (L2) for data transmission between the terminal and the network. Establishing a radio bearer means defining characteristics of a radio protocol layer and a channel to provide a specific service, and setting each specific parameter and operation method. The radio bearer may be further divided into two signaling radio bearers (SRBs) and data radio bearers (DRBs). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

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

One cell constituting the base station is set to one of the bandwidth, such as 1.25, 2.5, 5, 10, 20Mhz to provide a downlink or uplink transmission service to multiple terminals. Different cells may be configured to provide different bandwidths.

A downlink transport channel for transmitting data from a network to a terminal includes a broadcast channel (BCH) for transmitting system information, a PCH for transmitting a paging message, and a DL-SCH for transmitting user traffic or control messages. There is this. Traffic or control messages of the downlink multicast or broadcast service may be transmitted through the DL-SCH or may be transmitted through a separate downlink multicast channel (MCH). Meanwhile, an uplink transport channel for transmitting data from a terminal to a network includes a random access channel (RACH) for transmitting an initial control message, and an UL-SCH (uplink shared) for transmitting user traffic or a control message. channel).

The logical channel is on top of the transport channel and is mapped to the transport channel. The logical channel may be divided into a control channel for transmitting control region information and a traffic channel for delivering user region information. The control channel includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a dedicated control channel (DCCH), multicast And a control channel (MCCH: multicast control channel). Traffic channels include a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). PCCH is a downlink channel that carries paging information and is used when the network does not know the cell to which the UE belongs. CCCH is used by a UE that does not have an RRC connection with the network. A point-to-multipoint downlink channel used to convey multimedia broadcast and multicast service (MBMS) control information from an MCCH network to a UE. The DCCH is a point-to-point bi-directional channel used by a terminal having an RRC connection for transferring dedicated control information between the UE and the network. DTCH is a point-to-point channel dedicated to one terminal for transmitting user information that may exist in uplink and downlink. MTCH is a point-to-multipoint downlink channel for carrying traffic data from the network to the UE.

In the case of an uplink connection between a logical channel and a transport channel, the DCCH may be mapped to the UL-SCH, the DTCH may be mapped to the UL-SCH, and the CCCH may be mapped to the UL-SCH. Can be. In the case of a downlink connection between a logical channel and a transport channel, the BCCH may be mapped with the BCH or DL-SCH, the PCCH may be mapped with the PCH, and the DCCH may be mapped with the DL-SCH. The DTCH may be mapped with the DL-SCH, the MCCH may be mapped with the MCH, and the MTCH may be mapped with the MCH.

5 shows an S1 interface protocol structure in a wireless communication system to which the present invention can be applied.

FIG. 5A illustrates a control plane protocol stack in an S1 interface, and FIG. 5B illustrates a user plane interface protocol structure in an S1 interface.

4, the S1 control plane interface (S1-MME) is defined between the base station and the MME. Similar to the user plane, the transport network layer is based on IP transport. However, it is added to the SCTP (Stream Control Transmission Protocol) layer above the IP layer for reliable transmission of message signaling. The application layer signaling protocol is referred to as S1-AP (S1 application protocol).

The SCTP layer provides guaranteed delivery of application layer messages.

Point-to-point transmission is used at the transport IP layer for protocol data unit (PDU) signaling transmission.

A single SCTP association per S1-MME interface instance uses a pair of stream identifiers for the S-MME common procedure. Only some pairs of stream identifiers are used for the S1-MME dedicated procedure. The MME communication context identifier is assigned by the MME for the S1-MME dedicated procedure, and the eNB communication context identifier is assigned by the eNB for the S1-MME dedicated procedure. The MME communication context identifier and the eNB communication context identifier are used to distinguish the UE-specific S1-MME signaling transmission bearer. Communication context identifiers are each carried in an S1-AP message.

When the S1 signaling transport layer notifies the S1AP layer that the signaling connection is disconnected, the MME changes the state of the terminal that used the signaling connection to the ECM-IDLE state. And, the eNB releases the RRC connection of the terminal.

S1 user plane interface (S1-U) is defined between the eNB and the S-GW. The S1-U interface provides non-guaranteed delivery of user plane PDUs between the eNB and the S-GW. The transport network layer is based on IP transmission, and a GPRS Tunneling Protocol User Plane (GTP-U) layer is used above the UDP / IP layer to transfer user plane PDUs between the eNB and the S-GW.

6 is a diagram exemplarily illustrating a structure of a physical channel in a wireless communication system to which the present invention can be applied.

Referring to FIG. 6, a physical channel transmits signaling and data through a radio resource including one or more subcarriers in a frequency domain and one or more symbols in a time domain.

One subframe having a length of 1.0 ms is composed of a plurality of symbols. The specific symbol (s) of the subframe (eg, the first symbol of the subframe) can be used for the PDCCH. The PDCCH carries information about dynamically allocated resources (eg, a resource block, a modulation and coding scheme (MCS), etc.).

EMM  And ECM status

It looks at the status of EPS mobility management (EMM) and EPS connection management (ECM).

7 is a diagram illustrating EMM and ECM states in a wireless communication system to which the present invention can be applied.

Referring to FIG. 7, an EMM registered state (EMM-REGISTERED) according to whether a UE is attached or detached from a network in order to manage mobility of the UE in a NAS layer located in a control plane of the UE and the MME. And an EMM deregistration state (EMM-DEREGISTERED) may be defined. The EMM-REGISTERED state and the EMM-DEREGISTERED state may be applied to the terminal and the MME.

As in the case of powering on the terminal for the first time, the initial terminal is in the EMM-DEREGISTERED state, and the terminal performs a process of registering with the corresponding network through an initial attach procedure to access the network. If the access procedure is successfully performed, the UE and the MME are transitioned to the EMM-REGISTERED state. In addition, when the terminal is powered off or the radio link fails (when the packet error rate exceeds the reference value on the wireless link), the terminal is detached from the network and transitioned to the EMM-DEREGISTERED state.

In addition, an ECM-connected state and an ECM idle state (ECM-IDLE) may be defined to manage a signaling connection between the terminal and the network. ECM-CONNECTED state and ECM-IDLE state may also be applied to the UE and the MME. The ECM connection consists of an RRC connection established between the terminal and the base station and an S1 signaling connection established between the base station and the MME. In other words, when the ECM connection is set / released, it means that both the RRC connection and the S1 signaling connection are set / released.

The RRC state indicates whether the RRC layer of the terminal and the RRC layer of the base station are logically connected. That is, when the RRC layer of the terminal and the RRC layer of the base station is connected, the terminal is in the RRC connected state (RRC_CONNECTED). If the RRC layer of the terminal and the RRC layer of the base station is not connected, the terminal is in the RRC idle state (RRC_IDLE).

The network can grasp the existence of the terminal in the ECM-CONNECTED state in units of cells and can effectively control the terminal.

On the other hand, the network cannot grasp the existence of the UE in the ECM-IDLE state, and manages the core network (CN) in a tracking area unit that is a larger area than the cell. When the terminal is in the ECM idle state, the terminal performs Discontinuous Reception (DRX) set by the NAS using an ID assigned only in the tracking area. That is, the UE may receive broadcast of system information and paging information by monitoring a paging signal at a specific paging occasion every UE-specific paging DRX cycle.

In addition, when the terminal is in the ECM-IDLE state, the network does not have context information of the terminal. Accordingly, the UE in the ECM-IDLE state may perform a terminal-based mobility related procedure such as cell selection or cell reselection without receiving a command from the network. In the ECM idle state, when the location of the terminal is different from the location known by the network, the terminal may inform the network of the location of the terminal through a tracking area update (TAU) procedure.

On the other hand, when the terminal is in the ECM-CONNECTED state, the mobility of the terminal is managed by the command of the network. In the ECM-CONNECTED state, the network knows the cell to which the UE belongs. Accordingly, the network may transmit and / or receive data to or from the terminal, control mobility such as handover of the terminal, and perform cell measurement on neighbor cells.

As described above, the terminal needs to transition to the ECM-CONNECTED state in order to receive a normal mobile communication service such as voice or data. As in the case of powering on the terminal for the first time, the initial terminal is in the ECM-IDLE state as in the EMM state, and when the terminal is successfully registered in the network through an initial attach procedure, the terminal and the MME are in the ECM connection state. Transition is made. In addition, if the terminal is registered in the network but the traffic is inactivated and the radio resources are not allocated, the terminal is in the ECM-IDLE state, and if a new traffic is generated uplink or downlink to the terminal, a service request procedure UE and MME is transitioned to the ECM-CONNECTED state through.

EPS Bearer (bearer)

8 illustrates a bearer structure in a wireless communication system to which the present invention can be applied.

When a terminal is connected to a packet date network (PDN) (peer entity in FIG. 8), a PDN connection is generated, and the PDN connection may also be referred to as an EPS session. PDN is a service provider's external or internal IP (internet protocol) network to provide service functions such as the Internet or IMS (IP Multimedia Subsystem).

EPS sessions have one or more EPS bearers. The EPS bearer is a transmission path of traffic generated between the UE and the PDN GW in order to deliver user traffic in EPS. One or more EPS bearers may be set per terminal.

Each EPS bearer may be divided into an E-UTRAN radio access bearer (E-RAB) and an S5 / S8 bearer, and the E-RAB is divided into a radio bearer (RB: radio bearer) and an S1 bearer. Can lose. That is, one EPS bearer corresponds to one RB, S1 bearer, and S5 / S8 bearer, respectively.

The E-RAB delivers the packet of the EPS bearer between the terminal and the EPC. If there is an E-RAB, the E-RAB bearer and the EPS bearer are mapped one-to-one. A data radio bearer (DRB) transfers a packet of an EPS bearer between a terminal and an eNB. If the DRB exists, the DRB and the EPS bearer / E-RAB are mapped one-to-one. The S1 bearer delivers the packet of the EPS bearer between the eNB and the S-GW. The S5 / S8 bearer delivers an EPS bearer packet between the S-GW and the P-GW.

The UE binds a service data flow (SDF) to the EPS bearer in the uplink direction. SDF is an IP flow or collection of IP flows that classifies (or filters) user traffic by service. A plurality of SDFs may be multiplexed onto the same EPS bearer by including a plurality of uplink packet filters. The terminal stores mapping information between the uplink packet filter and the DRB in order to bind between the SDF and the DRB in the uplink.

P-GW binds SDF to EPS bearer in downlink direction. A plurality of SDFs may be multiplexed on the same EPS bearer by including a plurality of downlink packet filters. The P-GW stores the mapping information between the downlink packet filter and the S5 / S8 bearer to bind between the SDF and the S5 / S8 bearer in the downlink.

The eNB stores a one-to-one mapping between the DRB and the S1 bearer to bind between the DRB and the S1 bearer in the uplink / downlink. S-GW stores one-to-one mapping information between S1 bearer and S5 / S8 bearer in order to bind between S1 bearer and S5 / S8 bearer in uplink / downlink.

EPS bearers are classified into two types: a default bearer and a dedicated bearer. The terminal may have one default bearer and one or more dedicated bearers per PDN. The minimum default bearer of the EPS session for one PDN is called a default bearer.

The EPS bearer may be classified based on an identifier. EPS bearer identity is assigned by the terminal or the MME. The dedicated bearer (s) is combined with the default bearer by Linked EPS Bearer Identity (LBI).

When the terminal initially accesses the network through an initial attach procedure, a PDN connection is generated by assigning an IP address, and a default bearer is generated in the EPS section. Even if there is no traffic between the terminal and the corresponding PDN, the default bearer is not released unless the terminal terminates the PDN connection, and the default bearer is released when the corresponding PDN connection is terminated. Here, the bearer of all sections constituting the terminal and the default bearer is not activated, the S5 bearer directly connected to the PDN is maintained, the E-RAB bearer (ie DRB and S1 bearer) associated with the radio resource is Is released. When new traffic is generated in the corresponding PDN, the E-RAB bearer is reset to deliver the traffic.

While the terminal uses a service (for example, the Internet, etc.) through a default bearer, the terminal may use an insufficient service (for example, Videon on Demand (VOD), etc.) to receive a Quality of Service (QoS) with only the default bearer. Dedicated bearer is generated when the terminal requests (on-demand). If there is no traffic of the terminal dedicated bearer is released. The terminal or the network may generate a plurality of dedicated bearers as needed.

The IP flow may have different QoS characteristics depending on what service the UE uses. The network determines the allocation of network resources or a control policy for QoS at the time of establishing / modifying an EPS session for the terminal and applies it while the EPS session is maintained. This is called PCC (Policy and Charging Control). PCC rules are determined based on operator policy (eg, QoS policy, gate status, charging method, etc.).

PCC rules are determined in units of SDF. That is, the IP flow may have different QoS characteristics according to the service used by the terminal, IP flows having the same QoS are mapped to the same SDF, and the SDF becomes a unit for applying the PCC rule.

The main entities for performing such a PCC function may be Policy and Charging Control Function (PCRF) and Policy and Charging Enforcement Function (PCEF).

PCRF determines PCC rules for each SDF when creating or changing EPS sessions and provides them to the P-GW (or PCEF). After setting the PCC rule for the SDF, the P-GW detects the SDF for each IP packet transmitted and received and applies the PCC rule for the SDF. When the SDF is transmitted to the terminal via the EPS, it is mapped to an EPS bearer capable of providing a suitable QoS according to the QoS rules stored in the P-GW.

PCC rules are divided into dynamic PCC rules and pre-defined PCC rules. Dynamic PCC rules are provided dynamically from PCRF to P-GW upon EPS session establishment / modification. On the other hand, the predefined PCC rule is preset in the P-GW and activated / deactivated by the PCRF.

The EPS bearer includes a QoS Class Identifier (QCI) and Allocation and Retention Priority (ARP) as basic QoS parameters.

QCI is a scalar that is used as a reference to access node-specific parameters that control bearer level packet forwarding treatment, and the scalar value is pre-configured by the network operator. ) For example, a scalar may be preset to any one of integer values 1-9.

The main purpose of ARP is to determine if a bearer's establishment or modification request can be accepted or rejected if resources are limited. In addition, ARP can be used to determine which bearer (s) to drop by the eNB in exceptional resource constraints (eg, handover, etc.).

The EPS bearer is classified into a guaranteed bit rate (GBR) type bearer and a non-guaranteed bit rate (non-GBR) type bearer according to the QCI resource type. The default bearer may always be a non-GBR type bearer, and the dedicated bearer may be a GBR type or non-GBR type bearer.

GBR bearer has GBR and Maximum Bit Rate (MBR) as QoS parameters in addition to QCI and ARP. MBR means that fixed resources are allocated to each bearer (bandwidth guarantee). On the other hand, the non-GBR bearer has an MBR (AMBR: Aggregated MBR) combined as a QoS parameter in addition to QCI and ARP. AMBR means that resources are not allocated for each bearer, but the maximum bandwidth that can be used like other non-GBR bearers is allocated.

If the QoS of the EPS bearer is determined as above, the QoS of each bearer is determined for each interface. Since the bearer of each interface provides QoS of the EPS bearer for each interface, the EPS bearer, the RB, and the S1 bearer all have a one-to-one relationship.

While the terminal uses the service through the default bearer, if the service is insufficient to receive the QoS provided only by the default bearer, a dedicated bearer is generated on-demand.

FIG. 9 is a diagram illustrating a transmission path of a control plane and a user plane in an EMM registered state in a wireless communication system to which the present invention can be applied.

9 (a) illustrates the ECM-CONNECTED state, and FIG. 9 (b) illustrates the ECM-IDLE.

When the terminal successfully attaches to the network and becomes the EMM-Registered state, the terminal receives the service using the EPS bearer. As described above, the EPS bearer is configured by divided into DRB, S1 bearer, S5 bearer for each interval.

As illustrated in FIG. 9A, in the ECM-CONNECTED state in which user traffic is present, a NAS signaling connection, that is, an ECM connection (that is, an RRC connection and an S1 signaling connection) is established. In addition, an S11 GTP-C (GPRS Tunneling Protocol Control Plane) connection is established between the MME and the SGW, and an S5 GTP-C connection is established between the SGW and the PDN GW.

In addition, in the ECM-CONNECTED state, the DRB, S1 bearer, and S5 bearer are all configured (ie, radio or network resource allocation).

As shown in FIG. 9B, in the ECM-IDLE state in which there is no user traffic, the ECM connection (that is, the RRC connection and the S1 signaling connection) is released. However, the S11 GTP-C connection between the MME and the SGW and the S5 GTP-C connection between the SGW and the PDN GW are maintained.

In addition, in the ECM-IDLE state, both the DRB and the S1 bearer are released, but the S5 bearer maintains the configuration (ie, radio or network resource allocation).

Random Access Procedure

Hereinafter, a random access procedure provided by the LTE / LTE-A system will be described.

The random access procedure is used for the terminal to obtain uplink synchronization with the base station or to receive uplink radio resources. After the terminal is powered on, the terminal acquires downlink synchronization with the initial cell and receives system information. From the system information, a set of available random access preambles and information about radio resources used for transmission of the random access preambles are obtained. The radio resource used for the transmission of the random access preamble may be specified by a combination of at least one subframe index and an index on the frequency domain. The terminal transmits a random access preamble selected randomly from the set of random access preambles, and the base station receiving the random access preamble sends a timing alignment (TA) value for uplink synchronization to the terminal through a random access response. As a result, the terminal acquires uplink synchronization.

The random access procedure is a common procedure in frequency division duplex (FDD) and time division duplex (TDD). The random access procedure is irrelevant to the cell size, and is independent of the number of serving cells when carrier aggregation (CA) is configured.

First, a case where the UE performs a random access procedure may be as follows.

When the terminal performs an initial access in the RRC idle state because there is no RRC connection with the base station

When performing the RRC connection re-establishment procedure

When the UE first accesses the target cell during the handover process

When the random access procedure is requested by the command of the base station

In case of data to be transmitted in downlink during non-synchronized uplink time synchronization during RRC connection state

When there is data to be transmitted on the uplink in a situation in which the uplink time synchronization is not synchronized (non-synchronized) during the RRC connection state or when a designated radio resource used for requesting a radio resource is not allocated.

In the case of performing positioning of the UE in a situation in which timing advance is needed during the RRC connection state

When performing recovery process in case of radio link failure or handover failure

In 3GPP Rel-10, a common consideration is to apply a timing advance (TA) value applicable to one specific cell (eg, a Pcell) to a plurality of cells in a wireless access system supporting carrier aggregation. However, the UE may merge a plurality of cells belonging to different frequency bands (that is, largely spaced on the frequency) or a plurality of cells having different propagation characteristics. In addition, in the case of a specific cell, a small cell or a secondary base station such as a remote radio header (RRH) (ie, a repeater), a femto cell, or a pico cell may be used to expand coverage or remove coverage holes. In a situation where a secondary eNB (SeNB: secondary eNB) is disposed in a cell, the terminal communicates with a base station (ie, macro eNB) through one cell, and when communicating with a secondary base station through another cell, Cells may have different propagation delay characteristics. In this case, when uplink transmission using one TA value in a common manner may be seriously affected in synchronization of uplink signals transmitted on a plurality of cells. Therefore, it may be desirable to have a plurality of TAs in a CA situation in which a plurality of cells are merged. In 3GPP Rel-11, it is considered that an TA is independently allocated to a specific cell group unit to support multiple TAs. do. This is called a TA group (TAG: TA group). The TAG may include one or more cells, and the same TA may be commonly applied to one or more cells included in the TAG. In order to support such multiple TAs, a MAC TA command control element is composed of a 2-bit TAG identifier (TAG ID) and a 6-bit TA command field.

When the UE for which carrier aggregation is configured performs the random access procedure described above with respect to the PCell, the UE performs the random access procedure. In the case of a TAG (ie, a pTAG: primary TAG) to which a Pcell belongs, all cell (s) in the pTAG are replaced with a TA determined based on the Pcell or adjusted through a random access procedure accompanying the Pcell. Applicable to On the other hand, in the case of a TAG (ie, sTAG: secondary TAG) composed only of S cells, a TA determined based on a specific S cell in the sTAG may be applied to all cell (s) in the sTAG, where TA is a base station. Can be obtained by a random access procedure. Specifically, in the sTAG, the SCell is configured as an RACH resource, and the base station requests an RACH access from the SCell to determine the TA. That is, the base station initiates the RACH transmission on the S cells by the PDCCH order transmitted in the P cell. The response message for the SCell preamble is transmitted through the Pcell using the RA-RNTI. The UE may apply the TA determined based on the SCell that has successfully completed the random access to all cell (s) in the corresponding sTAG. As such, the random access procedure may be performed in the SCell to obtain a timing alignment of the sTAG to which the SCell belongs.

In the LTE / LTE-A system, in the process of selecting a random access preamble (RACH preamble), a contention-based random access procedure in which the UE randomly selects and uses one preamble within a specific set And a non-contention based random access procedure using a random access preamble allocated by a base station only to a specific terminal. However, the non- contention based random access procedure may be used only for the terminal positioning and / or the timing advance alignment for the sTAG when requested by the above-described handover procedure, a command of the base station. After the random access procedure is completed, general uplink / downlink transmission occurs.

Meanwhile, a relay node (RN) also supports both a contention-based random access procedure and a contention-free random access procedure. When the relay node performs a random access procedure, it suspends the RN subframe configuration at that point. In other words, this means temporarily discarding the RN subframe configuration. Thereafter, the RN subframe configuration is resumed when the random access procedure is completed successfully.

10 is a diagram for explaining a contention based random access procedure in a wireless communication system to which the present invention can be applied.

(1) first message (Msg 1, message 1)

First, the UE randomly selects one random access preamble (RACH preamble) from a set of random access preambles indicated through system information or a handover command, and A physical RACH (PRACH) resource capable of transmitting a random access preamble is selected and transmitted.

The random access preamble is transmitted in 6 bits in the RACH transmission channel, and the 6 bits are 5 bits of a random identity for identifying the UE transmitting the RACH, and 1 bit (eg, a third for indicating additional information). Message (indicating the size of Msg 3).

The base station receiving the random access preamble from the terminal decodes the preamble and obtains an RA-RNTI. The RA-RNTI associated with the PRACH in which the random access preamble is transmitted is determined according to the time-frequency resource of the random access preamble transmitted by the corresponding UE.

(2) a second message (Msg 2, message 2)

The base station transmits a random access response addressed to the RA-RNTI obtained through the preamble on the first message to the terminal. The random access response includes a random access preamble index / identifier (UL preamble index / identifier), an UL grant indicating an uplink radio resource, a temporary cell identifier (TC-RNTI), and a time synchronization value. (TAC: time alignment commands) may be included. The TAC is information indicating a time synchronization value that the base station sends to the terminal to maintain uplink time alignment. The terminal updates the uplink transmission timing by using the time synchronization value. When the terminal updates the time synchronization, a time alignment timer is started or restarted. The UL grant includes an uplink resource allocation and a transmit power command (TPC) used for transmission of a scheduling message (third message), which will be described later. TPC is used to determine the transmit power for the scheduled PUSCH.

After the UE transmits the random access preamble, the base station attempts to receive its random access response within the random access response window indicated by the system information or the handover command, and PRACH The PDCCH masked by the RA-RNTI corresponding to the PDCCH is detected, and the PDSCH indicated by the detected PDCCH is received. The random access response information may be transmitted in the form of a MAC packet data unit (MAC PDU), and the MAC PDU may be transmitted through a PDSCH. The PDCCH preferably includes information of a terminal that should receive the PDSCH, frequency and time information of a radio resource of the PDSCH, a transmission format of the PDSCH, and the like. As described above, once the UE successfully detects the PDCCH transmitted to the UE, the UE can properly receive the random access response transmitted to the PDSCH according to the information of the PDCCH.

The random access response window refers to a maximum time period in which a terminal that transmits a preamble waits to receive a random access response message. The random access response window has a length of 'ra-ResponseWindowSize' starting from subframes after three subframes in the last subframe in which the preamble is transmitted. That is, the UE waits to receive a random access response during the random access window obtained after three subframes from the subframe in which the preamble is terminated. The terminal may acquire a random access window size ('ra-ResponseWindowsize') parameter value through system information, and the random access window size may be determined as a value between 2 and 10.

If the terminal successfully receives a random access response having the same random access preamble identifier / identifier as the random access preamble transmitted to the base station, the monitoring stops the random access response. On the other hand, if the random access response message is not received until the random access response window ends, or if a valid random access response having the same random access preamble identifier as the random access preamble transmitted to the base station is not received, the random access response is received. Is considered to have failed, and then the UE may perform preamble retransmission.

As described above, the reason why the random access preamble identifier is needed in the random access response is that the UL grant, the TC-RNTI, and the TAC are used by any terminal because one random access response may include random access response information for one or more terminals. This is because we need to know if it is valid.

(3) third message (Msg 3, message 3)

When the terminal receives a valid random access response to the terminal, it processes each of the information included in the random access response. That is, the terminal applies the TAC, and stores the TC-RNTI. In addition, by using the UL grant, the data stored in the buffer of the terminal or newly generated data is transmitted to the base station. In the case of initial access of the UE, an RRC connection request generated in the RRC layer and delivered through the CCCH may be included in the third message and transmitted, and in the case of an RRC connection reestablishment procedure, an RRC generated in the RRC layer and delivered through the CCCH The connection reestablishment request may be included in the third message and transmitted. It may also include a NAS connection request message.

The third message should include the identifier of the terminal. In the contention-based random access procedure, it is not possible to determine which terminals perform the random access procedure in the base station, because the terminal needs to be identified for future collision resolution.

There are two methods for including the identifier of the terminal. In the first method, if the UE has a valid cell identifier (C-RNTI) allocated in the corresponding cell before the random access procedure, the UE transmits its cell identifier through an uplink transmission signal corresponding to the UL grant. do. On the other hand, if a valid cell identifier has not been allocated before the random access procedure, the UE transmits its own unique identifier (eg, S-TMSI or random number). In general, the unique identifier is longer than the C-RNTI. Terminal specific scrambling is used for transmission on the UL-SCH. However, if the terminal has not yet been assigned a C-RNTI, scrambling cannot be based on the C-RNTI, and the TC-RNTI received in the random access response is used instead. If the UE transmits data corresponding to the UL grant, it starts a timer for contention resolution (contention resolution timer).

(4) Fourth message (Msg 4, message 4)

When the base station receives the C-RNTI of the terminal through the third message from the terminal, the base station transmits a fourth message to the terminal using the received C-RNTI. On the other hand, when the unique identifier (ie, S-TMSI or random number) is received from the terminal through the third message, the fourth message is transmitted using the TC-RNTI allocated to the terminal in the random access response. Send to the terminal. Here, the fourth message may correspond to an RRC connection setup message including a C-RNTI.

After transmitting the data including its identifier through the UL grant included in the random access response, the terminal waits for an instruction of the base station to resolve the collision. That is, it attempts to receive a PDCCH to receive a specific message. There are two methods for receiving the PDCCH. As mentioned above, when the third message transmitted in response to the UL grant is its C-RNTI, it attempts to receive the PDCCH using its C-RNTI, and the identifier is a unique identifier (that is, In the case of S-TMSI or a random number, it attempts to receive the PDCCH using the TC-RNTI included in the random access response. Then, in the former case, if the PDCCH is received through its C-RNTI before the conflict resolution timer expires, the terminal determines that the random access procedure has been normally performed, and terminates the random access procedure. In the latter case, if the PDCCH is received through the TC-RNTI before the conflict resolution timer expires, the data transmitted by the PDSCH indicated by the PDCCH is checked. If the unique identifier is included in the content of the data, the terminal determines that the random access procedure is normally performed, and terminates the random access procedure. The terminal acquires the C-RNTI through the fourth message, and then the terminal and the network transmit and receive a terminal-specific message using the C-RNTI.

The following describes a method for conflict resolution in random access.

The reason for collision in performing random access is basically because the number of random access preambles is finite. That is, since the base station cannot grant the UE-specific random access preamble to all the UEs, the UE randomly selects and transmits one of the common random access preambles. Accordingly, when two or more terminals select and transmit the same random access preamble through the same radio resource (PRACH resource), the base station determines that one random access preamble is transmitted from one terminal. For this reason, the base station transmits a random access response to the terminal and predicts that the random access response will be received by one terminal. However, as described above, since collision may occur, two or more terminals receive one random access response, and thus, each terminal performs an operation according to reception of a random access response. That is, a problem occurs in that two or more terminals transmit different data to the same radio resource by using one UL Grant included in the random access response. Accordingly, all of the data transmission may fail, or only the data of a specific terminal may be received at the base station according to the location or transmission power of the terminals. In the latter case, since both of the two or more terminals assume that the transmission of their data was successful, the base station should inform the terminals that have failed in the competition information about the fact of the failure. That is, contention of failure or success of the competition is referred to as contention resolution.

There are two methods of conflict resolution. One method is to use a contention resolution timer, and the other is to transmit an identifier of a successful terminal to the terminals. The former case is used when the terminal already has a unique C-RNTI before the random access procedure. That is, the terminal already having the C-RNTI transmits data including its C-RNTI to the base station according to the random access response, and operates the collision resolution timer. When the PDCCH information indicated by the C-RNTI is received before the conflict resolution timer expires, the UE determines that the UE has succeeded in the competition and ends the random access normally. Conversely, if the PDCCH indicated by its C-RNTI has not been transmitted before the conflict resolution timer expires, it is determined that it has failed in the race, and the random access procedure is performed again or failed to a higher layer. Can be informed. The latter case of the collision resolution method, that is, a method of transmitting an identifier of a successful terminal is used when the terminal does not have a unique cell identifier before the random access procedure. That is, when the UE itself does not have a cell identifier, the UE transmits data including an identifier higher than the cell identifier (S-TMSI or random number) according to UL Grant information included in the random access response, and the UE operates a collision resolution timer. Let's do it. Before the conflict resolution timer expires, if data including its higher identifier is transmitted to the DL-SCH, the terminal determines that the random access procedure is successful. On the other hand, if the conflict resolution timer is not expired, if the data including its higher identifier is not transmitted to the DL-SCH, the UE is determined that the random access process has failed.

Meanwhile, unlike the contention-based random access procedure illustrated in FIG. 15, the operation in the non-competitive random access procedure ends the random access procedure only by transmitting the first message and transmitting the second message. However, before the terminal transmits the random access preamble to the base station as the first message, the terminal is allocated a random access preamble from the base station, and transmits the allocated random access preamble to the base station as a first message and from the base station. The random access procedure is terminated by receiving the random access response.

PDN  Connectivity

The network generates a PDN connection (or EPS session, IP session) and a packet data network (PDN) suitable for the purpose of packet data to be transmitted and received by the terminal, and bearers within the corresponding PDN connection. ) To send packets.

Here, the PDN means an external IP network interconnected with the EPC through the P-GW. As an example of such a PDN, the Internet, an IP Multimedia Subsystem (IMS), and the like may correspond thereto.

The PDN connection means an association between a terminal represented by one IPv4 address and / or one IPv6 prefix and a PDN represented by an access point name (APN). That is, the PDN connection means a connection between the terminal and the PDN.

In order to access the network, the PDN connection is established between the UE and the PDN through an attach procedure or a UE requested PDN connectivity procedure. That is, in order for the terminal to be connected to the PDN, the terminal is assigned a PDN address (ie, an IP address of the terminal to be used in the corresponding PDN).

In other words, the network creates a default bearer in one PDN connection and a PDN connection as a default between the UE and the PDN, and the IP address of the UE is generated in the process of creating a default bearer between the P-GW and the UE. It is generated in the P-GW and delivered to the terminal. In addition, the terminal receives the service provided by the corresponding PDN using the IP address allocated to the corresponding PDN. The basic bearer is maintained until the terminal is released from the network through a detach procedure, and also maintains the IP address assigned to the terminal when accessing the initial mobile communication network. At this time, the terminal is assigned an IP address for each PDN.

Here, the APN (Access Point Name) is an identifier for identifying the PDN. In other words, the PDN is identified by the APN. APNs are classified into network IDs and operator IDs. The network ID is used to identify a PDN, such as the Internet or a cooperating VPN, or to identify services provided by the PDN, such as IMS.

The establishment of the PDN connection may be performed by the MME, and the MME determines which PDN the UE connects to and which P-GW to access in order to establish a PDN connection between the UE and the PDN.

First, in the method of determining the PDN, since information on the PDN to be accessed by the UE (ie, APN) is previously stored in the HSS as subscription data, the MME receives subscription information from the HSS. The PDN to which the corresponding UE is connected may be determined.

The APN is pre-provisioned in the HSS as registration information when the subscriber is registered, and is stored in the MME, S-GW, P-GW, and PCRF as the PDN connection is established when the terminal is initially connected. The MME uses the APN to find a gateway (ie, P-GW) to connect the UE to the PDN defined by the APN.

The default APN is defined as an APN marked by default in subscription information / subscription data. When there is no APN provided to the terminal, it is used in the attach procedure and the UE requested PDN connectivity procedure.

Next, in the method of determining the P-GW, a method of using subscription information pre-stored in the HSS and a method of determining the P-GW using a predetermined P-GW selection policy. There is this. In the former case, the MME checks the P-GW to be used by the UE from the HSS when the UE accesses the PDN, and establishes a PDN connection to the UE through the corresponding P-GW.

The P-GW ID is an identifier used to identify the P-GW and may have an IP address or a fully qualified domain name (FQDN).

For example, when PDN 1 (eg, the Internet) is set as the default APN (PDN) of the terminal, when the terminal initially accesses the network, the MME requests subscription information of the terminal from the HSS. And, the MME receives the information that the P-GW P-GW 1 for accessing the PDN 1 and PDN 1 which is the default PDN of the terminal from the HSS. The MME establishes a PDN connection between the UE and PDN 1 through P-GW 1. At this time, the MME uses the P-GW ID to identify the P-GW 1. If the P-GW ID is given as the FQDN, the MME may obtain the P-GW IP address through a DNS query. In this case, when the DNS gives the P-GW list, the MME may select one of them according to the P-GW selection policy.

Three types of PDN types (or IP versions) are defined: IPv4 (IP Version 4), IPv6 (IP Version 6), and IPv4v6.

First, in the case of the IPv4 PDN type, the network may assign an IP address to the terminal during the basic bearer activation in the attach procedure or the UE requested PDN connectivity procedure, and the access procedure of the terminal. (Attach Procedure) can also be assigned through the Dynamic Host Configuration Protocol (DHCP) procedure.

In the case of IPv6 PDN type, the network performs IPv6 stateless address auto-configuration (SLLAC) procedure for global IPv6 address assignment, and the terminal is a basic service in the attach procedure or UE requested PDN connectivity procedure. A 64-bit Interface Identifier (IID) is assigned in the bearer activation process, and a 64-bit prefix is allocated through the IPv6 SLLAC process, thereby allowing a global IPv6 address of 128 bits to be allocated.

In the case of the IPv4v6 PDN type, the above-described address allocation method of the IPv4 PDN type and the IPv6 PDN type is applied simultaneously.

Hereinafter, a procedure of establishing a PDN connection between a terminal and a PDN will be described.

11 is a diagram briefly illustrating an attach procedure in a wireless communication system to which the present invention may be applied.

The attach procedure is generally used to establish a connection to a network when the UE enters an E-UTRAN cell. It may also be used in case of handover from the non-3GPP network to the E-UTRAN.

1-2. The UE (UE) initiates the attach procedure by sending an Attach Request message to the MME.

The attach request message includes an International Mobile Subscriber Identity (IMSI) of the terminal, a PDN type requested by the terminal, and the like. Here, the PDN type indicates an IP version (ie, IPv4, IPv4v6, IPv6) requested by the terminal.

The Attach Request message is included in the RRC Connection Setup Complete message in the RRC connection and delivered, and is included in the Initial UE message in the S1 signaling connection.

3. The MME requests and receives information for authentication from the HSS for terminal authentication, and performs mutual authentication with the terminal.

4. The MME registers the location of the terminal to the HSS and receives user subscription information (ie, subscribed QoS Profile) from the HSS to create a default bearer for the terminal.

Here, in the case of dynamic IP address allocation, the subscription information does not include IP address information for the corresponding terminal, but in the case of static IP address allocation, the subscription information is fixed assigned to the corresponding terminal. Contains IP address information.

5. The MME assigns a default EPS bearer ID and sends a Create Session Request message to the S-GW.

The Create Session Request message includes the IMSI of the UE, the EPS bearer ID, the P-GW ID selected by the MME for creating the EPS bearer (ie, the P-GW address), the subscription QoS profile received from the APN, and the HSS, and the PDN. Type, IP address (ie, PDN address) of the terminal, and the like.

Here, the PDN type includes the same PDN type information received from the terminal. In the case of dynamic IP address allocation, the IP address of the terminal may be set to 0. In the case of static IP address allocation, the static IP address information allocated to the terminal may be Inclusively).

6. The S-GW allocates an S5 S-GW Tunnel Endpoint Identifier (TEID) to create an S5 bearer with the P-GW included in the Create Session Request message received from the MME, and the corresponding P-GW. Send a Create Session Request message to the user.

The Create Session Request message includes the IMSI, EPS bearer ID, S5 S-GW TEID, APN, subscription QoS profile, PDN type (i.e., IP version), IP address (i.e., PDN address) of the terminal, and the like. It includes.

7. The P-GW allocates an Internet Protocol (IP) address to be used by the terminal and performs a PCRF and IP connectivity access network (IP-CAN) session establishment / modification procedure.

In this case, the P-GW may allocate an IP address selected from the IP address pool owned by the P-GW to the terminal in the case of dynamic IP address allocation, and a static IP address allocation. ), The fixed IP address information (included in the subscription information) allocated to the terminal may be identically allocated.

8. The P-GW allocates a P-GW Tunnel Endpoint Identifier (TEID) to create an S5 bearer with the S-GW, and sends a session creation response to the S-GW in response to a Create Session Request message. Create Session Response) message.

 The Create Session Response message includes an IMSI of the terminal, an EPS bearer ID, an S5 P-GW TEID, a subscription QoS profile, a PDN type, an IP address assigned to the terminal (ie, a PDN address), and the like.

If the P-GW selects a PDN type different from the requested PDN type, the P-GW indicates to the UE why the PDN type is modified along with the PDN type.

After completing this procedure, the generation of the S5 bearer between the S-GW and the P-GW is completed, and the S-GW may transmit uplink traffic to the P-GW or receive downlink traffic from the P-GW.

9. The S-GW allocates the S1 S-GW TEID to create the S1 bearer, and sends a Create Session Response message to the MME in response to the Create Session Request message.

The Create Session Response message includes an IMSI of the terminal, an EPS bearer ID, an S1 S-GW TEID, a PDN type, an IP address assigned to the terminal (ie, a PDN address), and the like.

10-11. The MME transmits an attach accept message to the terminal in response to an attach request message.

Attach Accept message includes EPS bearer ID, APN, IP address (ie PDN address) of UE assigned by P-GW, PDN type, Tracking Area Identity (TAI) list, TAU timer, etc. It includes.

The attach accept message is included in an initial context setup request message in the S1 signaling connection and delivered to the base station.

After completing this procedure, the generation of the uplink S1 bearer between the base station and the S-GW is completed, the base station can transmit the uplink traffic to the S-GW.

The attach accept message is included in the RRC connection reconfiguration message in the RRC connection and transmitted from the base station to the terminal.

After completing this procedure, the generation of the DRB between the terminal and the base station is completed, the terminal may transmit the uplink traffic to the base station or receive downlink traffic from the base station.

12. The base station transmits an initial context setup response message to the MME in response to the initial context setup request message. The Initial Context Setup Response message includes an S1 eNB TEID.

13-14. The terminal transmits an Attach Complete message to the MME in response to the Attach Accept message.

The Attach Complete message is included in the UL Information Transfer message in the RRC connection and transmitted, and is included in the Uplink NAS Transport message in the S1 signaling connection.

After this procedure, the generation of the uplink default EPS bearer between the terminal and the P-GW is completed, the terminal may transmit the uplink data to the P-GW.

15. The MME delivers the S1 eNB TEID received from the base station to the S-GW through a Modify Bearer Request message.

After this procedure, the generation of the downlink S1 bearer between the base station and the S-GW is completed, the base station can receive the downlink traffic from the S-GW.

16-17. If necessary, bearers are updated between the S-GW and the P-GW.

18. The S-GW sends a Modify Bearer Response message to the MME in response to the Modify Bearer Request message.

After this procedure, the generation of the downlink default EPS bearer between the terminal and the P-GW is completed, the P-GW may transmit the downlink data to the terminal. That is, the terminal may establish a connection with the PDN and receive the PDN service using the assigned IP address.

19. The MME sends a Notify Request message to the HSS including the P-GW ID (ie, P-GW address) and APN as needed.

20. The HSS stores the P-GW ID (ie, P-GW address) and associated APN and sends a Notify Response message to the MME.

12 is a diagram illustrating a UE requested PDN connectivity procedure in a wireless communication system to which the present invention can be applied.

The UE requested PDN connectivity procedure is used for the UE to request connection (including assignment of a default bearer) to an additional PDN through the E-UTRAN.

1. The UE initiates a UE Requested PDN procedure by sending a PDN Connectivity Request message to the MME.

The PDN Connectivity Request message includes an APN, a PDN type (ie, an IP version) requested by the UE, and the like. As described above, the PDN type indicates the IP version (ie, IPv4, IPv4v6, IPv6) requested by the terminal.

The MME verifies whether the APN provided by the terminal is allowed by the subscription information. If the terminal does not provide the APN in the PDN Connectivity Request message, the MME uses the APN from the default PDN subscription context.

2. The MME assigns an EPS bearer ID and sends a Create Session Request message to the S-GW.

The Create Session Request message includes the IMSI of the UE, the EPS bearer ID, the P-GW ID selected by the MME for creating the EPS bearer (ie, the P-GW address), the subscription QoS profile received from the APN, and the HSS, and the PDN. Type, IP address (ie, PDN address) of the terminal, and the like.

Here, the PDN type includes the same PDN type information received from the terminal. In the case of dynamic IP address allocation, the IP address of the terminal may be set to 0. In the case of static IP address allocation, the static IP address information allocated to the terminal may be Inclusively).

3. The S-GW allocates an S5 S-GW Tunnel Endpoint Identifier (TEID) to create an S5 bearer with the P-GW included in the Create Session Request message received from the MME, and the corresponding P-GW. Send a Create Session Request message to the user.

The Create Session Request message includes the IMSI, EPS bearer ID, S5 S-GW TEID, APN, subscription QoS profile, PDN type (i.e., IP version), IP address (i.e., PDN address) of the terminal, and the like. It includes.

4. The P-GW allocates an Internet Protocol (IP) address to be used by the terminal and performs a PCRF and IP connectivity access network (IP-CAN) session establishment / modification procedure.

In this case, the P-GW may allocate an IP address selected from the IP address pool owned by the P-GW to the terminal in the case of dynamic IP address allocation, and a static IP address allocation. ), The fixed IP address information (included in the subscription information) allocated to the terminal may be identically allocated.

5. The P-GW allocates a P-GW Tunnel Endpoint Identifier (TEID) to create an S5 bearer with the S-GW, and responds to the S-GW with a session creation response (in response to a Create Session Request message). Create Session Response) message.

The Create Session Response message includes an IMSI of the terminal, an EPS bearer ID, an S5 P-GW TEID, a subscription QoS profile, a PDN type, an IP address assigned to the terminal (ie, a PDN address), and the like.

If the P-GW selects a PDN type different from the requested PDN type, the P-GW indicates to the UE why the PDN type is modified along with the PDN type.

After completing this procedure, the generation of the S5 bearer between the S-GW and the P-GW is completed, and the S-GW may transmit uplink traffic to the P-GW or receive downlink traffic from the P-GW.

6. The S-GW allocates the S1 S-GW TEID to create the S1 bearer, and sends a Create Session Response message to the MME in response to the Create Session Request message.

The Create Session Response message includes an IMSI of the terminal, an EPS bearer ID, an S1 S-GW TEID, a PDN type, an IP address assigned to the terminal (ie, a PDN address), and the like.

7. The MME transmits a PDN Connectivity Accept message to the UE in response to the PDN Connectivity Request message.

The PDN Connectivity Accept message includes an EPS bearer ID, an APN, an IP address (ie, a PDN address), a PDN type, etc. of a UE allocated by the P-GW.

The PDN Connectivity Accept message is included in the bearer setup request message in the S1 signaling connection and delivered to the base station.

After completing this procedure, the generation of the uplink S1 bearer between the base station and the S-GW is completed, the base station can transmit the uplink traffic to the S-GW.

8. The PDN Connectivity Accept message is included in the RRC Connection Reconfiguration message in the RRC connection and transmitted from the base station to the terminal.

After completing this procedure, the generation of the DRB between the terminal and the base station is completed, the terminal may transmit the uplink traffic to the base station or receive downlink traffic from the base station.

9. The terminal transmits an RRC connection reconfiguration complete message to the base station.

10. The base station sends a bearer setup response message to the MME.

The bearer setup response message includes an S1 eNB TEID.

11-12. The terminal transmits a PDN Connectivity Complete message including the EPS bearer ID to the MME.

After this procedure, the generation of the uplink default EPS bearer between the terminal and the P-GW is completed, the terminal may transmit the uplink data to the P-GW.

13. The MME forwards the S1 eNB TEID received from the base station to the S-GW through a Modify Bearer Request message.

After this procedure, the generation of the downlink S1 bearer between the base station and the S-GW is completed, the base station can receive the downlink traffic from the S-GW.

13a-13b. If necessary, bearers are updated between the S-GW and the P-GW.

14. The S-GW sends a Modify Bearer Response message to the MME in response to the Modify Bearer Request message.

After this procedure, the generation of the downlink default EPS bearer between the terminal and the P-GW is completed, the P-GW may transmit the downlink data to the terminal. That is, the terminal may establish a connection with the PDN and receive the PDN service using the assigned IP address.

15. The MME sends a Notify Request message to the HSS that includes the P-GW ID (ie, P-GW address) and APN as needed.

16. The HSS stores the P-GW ID (ie, P-GW address) and associated APN and sends a Notify Response message to the MME.

PDN  type Fallback (fallback) control method

Currently, IPv Version 6 (IPv6) has been developed to address the lack of IP Version 4 (IPv4) addresses, and operators are preparing to transition. However, studies have been conducted in 3GPP to address possible problems during the migration (see 3GPP TR 23.975).

Table 2 below categorizes PDN types that are substantially generated by IP version capabilities of UEs and networks.

Table 2 is a table illustrating PDN types and PDN connections.

Referring to Table 2, when the PDN type requested by the UE is IPv4v6 and the PDN type subscribed to the HSS is IPv4v6, a single PDN connection having a dual address is established.

On the other hand, if the PDN type requested by the UE is IPv4v6 and the PDN types subscribed to the HSS are IPv4 and IPv6, two PDN connections having a single address are established.

If the PDN type requested by the terminal is IPv4v6 and the PDN type subscribed to the HSS is IPv4 or IPv6, one PDN connection having a single address is established. In addition, when the PDN type subscribed to the HSS is IPv4v6, when the PDN type requested by the UE is IPv4 or IPv6, one PDN connection having a single address is established.

That is, there is a dual address bearer that supports dual stack (IPv4, IPV6) for a single PDN connection, and also configures IPv4 and IPv6 PDN connections, respectively. There are two PDN connections.

Through this, backward compatibility with applications that do not support IPv6 is solved, and even if a problem occurs in IPv6 system, it can be used as IPv4.

As described above, the 3GPP standard recommends IP version migration by allowing both IPv4 and IPv6 addresses to be assigned to the same PDN connection.

However, in this case, the operator may have a burden of operating two pools of IP addresses, which may not be a practical solution. In other words, when operating one APN (PDN), there is a high possibility that operators do not operate with dual stack (single PDN connection with dual address) PDN or two PDN connections with each single address.

Accordingly, as shown in Table 2, an IPv6 address is allocated to an IMS PDN operated by an operator and an IPv4 address is allocated for backward compatibility with an application that does not support IPv6 in an Internet PDN. Combination IP version operation is possible.

However, for various reasons, IPv6 operational failure may occur until the initial network operation is stabilized. Accordingly, there is a need for an operation of returning to / falling back to IPv4 which is stable when an IPv6 failure occurs during actual network operation. That is, IP addresses allocated to UEs are different according to IPv4 and IPv6 allocated by P-GW, and falling back to IPv4 means that an IPv4 address is reassigned to a UE.

In the past, when an IPv6 failure occurs, the operator sequentially falls back the subscriber's IP address to IPv4 to distribute the network load. For example, if you have about 8 million subscribers, it can take hours (eg 3 hours) to reassign all subscribers' IP addresses to IPv4. That is, in the case of randomly reassigning subscribers to IPv4 after an IPv6 failure, a specific terminal may experience service failure for up to 3 hours. In particular, in the case of IMS networks that support voice services, such a service failure may cause a situation where many terminals cannot make or receive calls (for example, call loss), which may significantly affect the service provider. have. Therefore, there is a need for a method capable of providing a service as smoothly as possible, especially in case of an IPv6 failure.

Accordingly, the present invention proposes a criterion for determining a fall back scheme for each PDN type combination of the PDN and a corresponding operation thereof.

The present invention largely proposes the following two configurations.

First, we propose a method to select one of two methods of falling back to IPv4 when an IPv6 failure occurs according to the IP version configuration of each provider's PDN.

That is, in case of a failure in IPv6 operation, the HSS checks the PDN connection allocated to the IPv6 among the PDN connections established in the terminal, thereby performing an HSS initiated detach and reattach procedure and an HSS request PDN. Determine whether to proceed with the HSS requested PDN disconnection and reconnection procedure.

2. And, based on the choice mentioned in section 1, we propose two IPv4 fallback schemes:

A. HSS initiated detach and reattach

B. HSS requested PDN disconnection and reconnection

In general, for a terminal supporting an IMS voice service, an Internet PDN and an IMS PDN are set.

For two PDNs, IPv4, IPv6, and IPv4v6 addresses can be allocated according to UE and operator capabilities.

However, the same IP version may be allocated to the two PDNs or different IP versions may be allocated according to the operator policy.

Accordingly, the present invention proposes a method of selecting an IPv4 fallback scheme according to the operator PDN IP version assignment in the following form.

Table 3 is a table illustrating an IP address allocation method according to an embodiment of the present invention.

Referring to Table 3, the HSS determines which PDN connection is a problem due to an IPv6 failure among PDN connections established to the UE, thereby causing problems for two PDN connections (that is, PDN connection to PDN 1 and PDN 2). If it is determined that the HSS initiated Detach with re-attach (HSS initiated Detach with re-attach) procedure can proceed.

On the other hand, if the HSS determines that only one PDN connection to PDN 1 and PDN 2 has occurred due to an IPv6 failure, a negligible or HSS requested PDN disconnection procedure may be performed.

In more detail, in the past, except for the cause of subscription withdrawal, the progress of the HSS initiated detach procedure cannot be performed through a Cancel Location message.

However, as shown in Table 3 above, when both PDNs operate IP addresses as IPv6, fallback to IPv4 is possible through re-attach after detach of the terminal when IPv6 failure occurs.

As such, if the detach procedure is performed, the terminal must re-establish the PDN connection through the attach procedure. And, during this process, the P-GW must reassign the IP address to the corresponding terminal. If the IPv6 is no longer available when the P-GW is determined, the P-GW reassigns the IPv4. Multimedia communication enables normal communication again through registration.

However, if only one of the two PDNs uses IPv6, it is possible to fall back to IPv4 by disconnecting and reactivating only the PDN (APN) where a failure situation occurs rather than detaching the terminal. That is, if there is one PDN connection in which an IPv6 failure occurs, and the UE establishes several PDN connections, it is sufficient to disconnect and reconnect only the PDN in question. Even in this case, if the detach procedure is performed for the terminal, the terminal should be re-connected after disconnecting all other PDN connections (that is, including PDN connection without problem).

Accordingly, the present invention proposes two procedures for falling back to IPv4.

That is, when IPv6 fails, HSS initiated Detach and Re-attach procedure (hereinafter referred to as' HSS initiated Detach with re-attach) Procedure ') and HSS request PDN disconnection and reconnection procedures (hereinafter referred to as' HSS requested PDN disconnection with HSS request reconnection') for specific PDNs that have an IPv6 failure. collectively referred to as the "with re-connection" procedure.

Furthermore, the present invention proposes a method of determining which procedure to proceed among the above two procedures by determining which PDN connection is a problem due to an IPv6 failure among PDN connections established to the UE.

In addition, in order to preferentially process a terminal having an IMS voice reception call / outgoing call, a method of processing an IPv4 fallback by giving priority to a terminal recognized for receiving an IMS voice call in the HSS is proposed.

To this end, first, the HSS transmits a Notify Request message during an attach procedure and a PDN connectivity procedure of an IP version according to a PDN for each UE. It can be stored in subscription information through the procedure of. In case of a failure of IPv6 or a specific PDN type, the provider uses this information to sequentially detach the HSS requested PDN disconnection or HSS initiated Detach with re-attach to individual terminals. attach).

Meanwhile, in Table 3 above, only Internet PDN and IMS PDN are illustrated for convenience of description, but in the present invention, other PDNs and terminals may be connected.

After all, according to the present invention, when a failure occurs for a specific PDN type, when the PDN type for all PDN connections established in the terminal is a failed PDN type, an HSS initiation re-attach is accompanied. Detach procedure may be performed, otherwise PDN disconnection procedure with HSS request reconnection may be performed for a specific PDN connection assigned a failed PDN type. have.

In the following description of the present invention, it is assumed that an operator determines that IPv6 cannot be used in a P-GW belonging to a home PLMN (HPLMN). That is, it is assumed that nodes belonging to the HPLMN (MME, HSS, S-GW, P-GW, etc.) by Operation and Maintenance (O & M) already know that they do not use the IPv6 allocated for the specific PDN connection. do.

In addition, in the following description of the present invention, it is assumed that the HSS knows a PDN type assigned to the terminal through a Notify Request message or the like.

As described above, in order for the HSS to select the PDN type fallback method, it is necessary to know the PDN type (ie, IP version) allocated for each PDN connection. This will be described with reference to the drawings below.

FIG. 13 is a diagram illustrating a method for informing a HSS of a PDN type according to an embodiment of the present invention. FIG.

When a problem is recognized (ie, by operator setting) for a specific PDN type, a recovery operation will be started. For example, the MME may detach and reattach (or PDN disconnect and re-connect) all terminals sequentially. . However, this recovery operation should occur in a range that minimizes the impact on the MME and network load, and it may take a considerable time for PDN type fallback of all subscribers.

Accordingly, the present invention proposes a method for performing recovery by prioritizing such a terminal in the HSS terminal in order to minimize service interference of voice call transmission and reception while such recovery operation is performed. That is, if the HSS recognizes that the voice call transmission and reception while recognizing that the recovery operation is already in progress, it is necessary to know whether the PDN type fallback of the corresponding UE is required. The current MME knows the PDN type actually assigned to the UE. However, the HSS is not known. Therefore, when establishing a PDN connection, the HSS needs to have information on the PDN type allocated to the UE.

Referring to FIG. 13, the UE transmits an attach request message or a PDN connectivity request message to an MME, and then attach or UE request PDN connectivity procedure. To start (S1301). That is, the procedure according to FIG. 11 and FIG. 12 is performed before (S1302).

During the Attach procedure or UE requested PDN connectivity procedure, the MME sends active PDN type information (active) assigned to the UE in the Notify Request message. Include and transmit to the HSS (S1303).

Through this process, the HSS can know the activated (assigned) PDN type for each PDN connection (or for each PDN (APN)) of the UE.

Table 4 below shows information in the HSS when the MME informs the HSS of the PDN type set for each PDN through the attach request procedure (see FIG. 11) and the Notify Request procedure of the PDN connection establishment procedure (see FIG. 12). Illustrates an information field.

Referring to Table 4, the HSS may store an allocated PDN type for each activated PDN connection.

Hereinafter, for convenience of description, the PDN type will be described by exemplifying IPv4, IPv6, and IPv4v6, but the present invention can be applied to the same PDN type.

1) HSS initiated Detach with re-attach procedure

14 is a diagram illustrating a PDN type fallback method according to an embodiment of the present invention.

If all PDNs operated by the service provider have an IPv6 failure while operating with IPv6, fallback to IPv4 can be performed through the Detach with re-attach procedure.

In addition, even if some PDNs operated by the service provider have an IPv6 failure while operating with IPv6, when all PDN connections of a specific terminal are set up as IPv6, the HSS is detached with a reattachment for the corresponding terminal. Fallback to IPv4 can be performed through the re-attach procedure.

In this case, the MME may proceed with the MME initiated Detach with re-attach procedure sequentially involving all terminals having a corresponding PDN connection.

In other words, the MME initiates a Detach with re-attach procedure that sequentially involves re-attachment for terminals allocated to IPv6 for all PDN connections.

According to the present invention, when the HSS recognizes a transmission / reception call of a specific terminal (terminal A in FIG. 14), the HSS initiated Detach with the HSS initiated reattachment is preferentially performed for the terminal. proceed with the re-attach procedure.

Referring to FIG. 14, the HSS detects (by setting of a network operator (operator)) that IPv6 has failed (S1401).

Thereafter, as described above, the IPv4 fallback procedure may be performed due to the IPv6 failure by the MME.

If the HSS recognizes an incoming IMS call to the terminal (terminal A in FIG. 14), the HSS initiated re-attach for IPv4 address assignment is given to the terminal to receive the received call. initiated Detach procedure with Re-attach (S1402), the HSS cancels the location including the identifier (e.g., IMSI) and the cause value (or cancellation type) of the terminal (terminal A). The message (Cancel Location) is transmitted to the MME (S1403).

In FIG. 14, only an incoming call to UE A is illustrated, but even when an outgoing call from UE A is generated, a Detach procedure with Re-attach procedure may be performed by prioritizing UE A in the same manner. Can be.

The HSS may first determine whether the terminal where the transmit / receive call is made is allocated IPv6 for all PDN connections. And, if the UE is assigned IPv6 for all PDN connections, the HSS may proceed with a Detach procedure with Re-attach for the IPv4 fallback of the UE.

In the present invention, a new cause is proposed so that an HSS initiation detach procedure can be performed to deal with a failure situation such as an IP version change.

The Cancel Location message is a 'HSS initiated detach' or 'IP' as an identifier (eg IMSI) and cause value (or cancellation type) of the terminal (terminal A). IP version change 'or' PDN type change '.

Also, the Cancel Location message may include re-attach indication information for indicating a re-attachment of the corresponding terminal. For example, the Detach type of the Cancel Location message may be set as a 'Re-attached required'.

The MME transmits a detach request message to the terminal (S1404).

In this case, when the MME receives a Cancel Location message from the HSS, the MME may transmit a Detach request message with priority over other terminals for the corresponding terminal.

The Detach request message includes re-attach indication information. For example, a detach type of a detach request message may be set as a 're-attached required'.

In addition, the detach request message may include 'HSS initiated detach' or 'IP version change' or 'PDN type change' as a cause value. can do.

If the terminal is in the ECM-IDLE state, after switching the terminal to the ECM-CONNECTED state through paging transmission, it may transmit a Detach request (Detach request) message to the terminal.

The terminal that receives the Detach request message from the MME deletes the EPS bearer context.

The MME transmits a Delete Session Request message to the SGW (S1405).

The Delete Session Request message may include an EPS bearer ID and the like, and the MME deletes EPS bearer context information of the corresponding UE after transmitting a Delete Session Request message.

The SGW transmits a Delete Session Request message received from the MME to the PGW (S1406).

The SGW deletes the EPS bearer context information of the terminal after transmitting a Delete Session Request message.

The PGW transmits a Delete Session Response message to the SGW in response to the Delete Session Request message in step S1406 (S1407).

The SGW deletes EPS bearer context information of the UE after transmitting a Delete Session Response message.

The SGW transmits a Delete Session Response message to the MME in response to the Delete Session Request message in step S1405 (S1408).

If the detach is successfully performed after the step S1404, the terminal transmits a detach accept message to the MME in response to the detach request message of the step S1404 (S1409).

Although not shown in FIG. 14, when the MME receives a Detach Accept message from the UE, the MME may transmit a Cancel Location Answer message to the HSS. Here, the Cancel Location Answer message may include an identifier of the terminal (eg, IMSI of the terminal).

The terminal, the base station, and the MME perform a signaling release procedure (S1410).

In more detail, the MME transmits a UE context release command message to the base station to release S1 signaling. If the RRC connection of the terminal is still established, the base station transmits an RRC connection release message to the terminal in order to release the RRC connection, and deletes information associated with the terminal. The base station transmits a UE context release complete message to the MME in response to the UE context release command message.

Since the Detach request message includes re-attach indication information, the UE immediately performs an attach procedure. That is, the terminal initiates the attach procedure illustrated in FIG. 11.

In this case, an instruction (for example, cause or indication) indicating this may be included in an attach request message for prompt processing of the IMS received call. For example, the attach request message may include a mobile originated progressed, an IP version change, or a PDN type change as the cause value. It may include.

Through this, even in congestion in the MME, the attach procedure of the corresponding terminal may be given priority.

Thereafter, the terminal is assigned an IPv4 address through an attach procedure. That is, since the P-GW already knows that an IPv6 failure occurs, the P-GW allocates an IPv4 address to the corresponding UE. Thereafter, the terminal may successfully process the IMS reception call.

Meanwhile, FIG. 14 briefly illustrates a detach procedure in order to clearly describe the present invention, and another procedure or another node not shown in FIG. 14 may be further added.

2) HSS requested PDN disconnection with reactivation procedure with HSS request re-activation (or re-connection)

15 is a diagram illustrating a PDN type fallback method according to an embodiment of the present invention.

If only some of the PDNs operated by the service provider have an IPv6 failure while operating with IPv6, PDN disconnection involving re-activation (or re-connection) only for PDN connections set up with IPv6 instead of the terminal attachment ( By performing fallback to IPv4 through PDN disconnection with reactivation procedure, IPv6 failure problem can be solved more simply.

In this case, the MME may proceed with MME requested PDN disconnection with reactivation procedure for all terminals having a connection with the corresponding PDN sequentially with respect to the PDN assigned with IPv6.

In other words, the MME initiates a PDN disconnection with reactivation procedure in which re-activation (or re-connection) is sequentially performed for terminals allocated to IPv6 only for some PDN connections.

Here, according to the present invention, when the HSS recognizes a transmission / reception call to a specific terminal (terminal A, in the case of FIG. 15), PDN accompanied with the HSS request re-activation (or re-connection) for the terminal Proceed with the HSS requested PDN disconnection with reactivation procedure.

Referring to FIG. 15, the HSS detects (by setting of a network operator (operator)) that IPv6 has failed (S1501).

Thereafter, as described above, the IPv4 fallback procedure may be performed due to the IPv6 failure by the MME.

If the HSS recognizes an incoming IMS call to the terminal (terminal A in FIG. 15), the HSS requested re-activation for IPv4 address assignment by prioritizing the terminal to receive the received call (HSS requested) Initiate a PDN disconnection with reactivation procedure (S1502), and the HSS requests a Cancel Location message or a PDN disconnect request including an identifier (eg, IMSI) and a PDN identifier (APN) of the corresponding UE (terminal A). The PDN disconnection request message is transmitted to the MME (S1503).

In FIG. 15, only an incoming call to the terminal A is illustrated, but even when an outgoing call from the terminal A is generated, the PDN disconnection with reactivation procedure may be performed by prioritizing the terminal A in the same manner. .

The HSS may first determine whether the terminal where the transmit / receive call is made is allocated IPv6 for all PDN connections. And, if the UE is not assigned IPv6 for all PDN connections (if IPv6 is allocated for some PDN connections), the HSS is a PDN disconnection with re-activation for IPv4 fallback of the UE. with reactivation).

In the present invention, a new message (for example, a PDN disconnection request message) is defined at the S6a interface between the MME and the HSS as shown in step S1503 of FIG. 15 so that the HSS may request a PDN disconnection from the HSS. .

This can be implemented by inserting a new cause into an existing Cancel Location message or by defining a new message that can command bearer deactivation.

That is, the Cancel Location message may include 'Bearer deactivation with reactivation requested' as a cause value (or cancellation type).

The PDN disconnection request message may include reactivation (or reconnection) indication information. For example, a reason for releasing PDN connection of a PDN disconnection request message may be set as a 'Reactivation required'.

When the MME receives a Cancel Location message or a PDN disconnection request message from the HSS for the UE, PDN disconnection with re-activation takes precedence over other UEs for the UE. With reactivation procedure (S1504), the MME transmits a Delete Session Request message to the SGW (S1505).

The Delete Session Request message may include an EPS bearer ID and the like, and the MME deletes EPS bearer context information of the corresponding UE after transmitting a Delete Session Request message.

The SGW transmits a Delete Session Request message received from the MME to the PGW (S1506).

The SGW deletes the EPS bearer context information of the terminal after transmitting a Delete Session Request message.

The PGW transmits a Delete Session Response message to the SGW in response to the Delete Session Request message in step S1506 (S1507).

The SGW deletes EPS bearer context information of the UE after transmitting a Delete Session Response message.

The SGW transmits a Delete Session Response message to the MME in response to the Delete Session Request message in step S1505 (S1508).

The MME transmits a bearer deactivate bearer request message to the base station in order to request deactivation of all bearers related to the corresponding PDN connection (S1509).

Here, the Deactivate Bearer Request message may include reactivation (or reconnection) indication information. For example, a reason for releasing PDN connection of a Deactivate Bearer Request message may be set as a 'Reactivation required'.

The base station transmits an RRC connection reconfiguration message to the terminal (S1510).

The RRC Connection Reconfiguration message may include a Deactivate EPS Bearer Context Request message, which is a NAS message.

In addition, the EPS bearer context deactivation request message may include reactivation (or reconnection) indication information. For example, a reason for releasing PDN connection of a Deactivate Bearer Request message may be set as a 'Reactivation required'.

The terminal transmits an RRC Connection Reconfiguration Complete message to the base station, and the terminal releases all radio resources for the corresponding PDN connection (S1511).

The base station transmits a bearer deactivate bearer response message to the MME in response to the bearer deactivate bearer request message of step S1509 (S1512).

The direct transfer message of the terminal is transmitted to the base station (S1513).

The direct transfer message may include a Deactivate EPS Bearer Context Accept message, which is a NAS message.

The base station transmits an uplink NAS transport message to the MME (S1514).

The uplink NAS transport message may include a Deactivate EPS Bearer Context Accept message.

Since the Deactivate EPS Bearer Context Request message previously includes reactivation (or reconnection) indication information, the UE immediately disconnects from the PDN (APN) and PDN connection request procedure (PDN connection request procedure). ). That is, the UE initiates the disconnected PDN (APN) and the UE requested PDN connectivity procedure illustrated in FIG. 12.

In this case, an indication (eg, cause or indication) indicating this in a PDN Connectivity Request message may be included for rapid processing of an IMS received call. For example, the PDN Connectivity Request message may include a mobile originated progressed, an IP version change, or a PDN type change as the cause value. It may include.

Through this, even in congestion in the MME, the PDN connection procedure of the corresponding UE may be prioritized and processed.

Thereafter, the terminal is assigned an IPv4 address through an attach procedure. That is, since the P-GW already knows that an IPv6 failure occurs, the P-GW allocates an IPv4 address to the corresponding UE. Thereafter, the terminal may successfully process the IMS reception call.

3) roaming case

When the terminal roams to the VPLMN, the MME belonging to the VPLMN (Visited PLMN) may not know whether a specific PDN type of the HPLMN (Home PLMN) has failed.

That is, even if the HSS requests detach and / or PDN disconnection from the MME as shown in the examples of FIGS. 14 and 15, the P-GW of the VPLMN may not be assigned as a valid PDN type that can be operated. In this case, processing is required at the MME stage.

Accordingly, in order for the HSS to change the PDN type to the MME, Detach with Reattach as shown in FIG. 14 or PDN Disconnection with reactivation as shown in FIG. 15 is performed. In case of request, appropriate information may be given to the corresponding UE so that a valid PDN type may be reset (or reassigned).

That is, the location cancellation (Cancel Location) message in step S1402 of FIG. 14 or the location cancellation (Cancel Location) message / PDN disconnection request message in step S1502 of FIG. 15 includes information on a valid PDN type. can do.

In this case, the information on the valid PDN type may indicate a PDN type in which a current failure occurs and thus the reset is not preferable, or a PDN type capable of normal operation may be indicated.

As above, when the MME receives a request for detach or PDN disconnection together with information on a valid PDN type, the MME sends information on a valid PDN type (ie, information on a PDN type that can operate normally) to the MME. Can save for a certain time.

Thereafter, the MME may be configured to assign a PDN type capable of normal operation of the terminal when the terminal is attached (attach) again or PDN connectivity (PDN Connectivity) reset. In this case, the MME may be configured to allocate a PDN type capable of normal operation regardless of the PDN type requested by the UE. For example, the MME may be used to configure the P-GW and PDN except for an invalid PDN type in the subscribed PDN type value provided from the HSS. In addition, the MME may select a P-GW supporting an appropriate PDN type. As a result, during the attach procedure or the PDN connectivity procedure by the terminal, the terminal may be connected to the P-GW which allocates a valid PDN type by the MME.

In particular, this proposed method can be used more effectively in roaming situations such as LBO (Local Break Out). In the LBO situation, the P-GW does not belong to the HPLMN, only to the VPLMN. In general, the P-GW can decide whether to use IPv4 IPv6 with a pool of IP addresses, but in the LBO situation, the P-GW belonging to the VPLMN cannot know whether IPv6 has failed. Accordingly, the HSS informs the MME belonging to the VPLMN that the UE should allocate IPv4, and when the UE establishes a PDN connection through the P-GW belonging to the VPLMN, the P-GW allocates an IPv4 address.

In addition, when operating in various ways for each operator, it is possible to more safely solve the PDN type failure (failure) problem by informing the MME belonging to the VPLMN to inform the PDN type that is not explicitly valid or only valid PDN type.

16 is a diagram illustrating a PDN type fallback method according to an embodiment of the present invention.

In FIG. 16, it is assumed that a first PDN type (for example, IPv6) fails and a second PDN type (for example, IPv4) can operate normally.

Referring to FIG. 16, after detecting an occurrence of a failure of a first PDN type, the HSS preferentially allocates a PDN type allocated for a PDN connection established by the terminal when there is a terminal having voice call transmission and reception. It is determined whether all of them are the first PDN type (S1601).

The HSS performs a detach with re-attach procedure or disconnection with re-activation depending on whether all PDN types allocated to the PDN connection of the UE are the first PDN type. One of the activation procedures is determined (S1602).

In addition, the HSS starts the procedure determined in step S1602 (S1603).

Here, when the PDN types allocated to the PDN connection of the UE are all the first PDN type, the HSS may determine a detach with re-attach procedure with the re-attach for the PDN type fallback. In this case, the procedure according to the example of FIG. 14 may be started.

On the other hand, when all of the PDN types allocated to the PDN connection of the UE are not the first PDN type, the HSS is disconnected with re-activation with respect to a specific PDN to which the first PDN type is allocated for the PDN type fallback. -activation) procedure. In this case, the procedure according to the example of FIG. 15 may be disclosed.

General apparatus to which the present invention can be applied

17 illustrates a block diagram of a communication device according to an embodiment of the present invention.

Referring to FIG. 17, a wireless communication system includes a network node 1710 and a plurality of terminals (UEs) 1720.

The network node 1710 includes a processor 1711, a memory 1712, and a communication module 1713. The processor 1711 implements the functions, processes, and / or methods proposed in FIGS. 1 to 16. Layers of the wired / wireless interface protocol may be implemented by the processor 1711. The memory 1712 is connected to the processor 1711 and stores various information for driving the processor 1711. The communication module 1713 is connected to the processor 1711 and transmits and / or receives a wired / wireless signal. As an example of the network node 1710, a base station, an MME, an HSS, an SGW, a PGW, an application server, and the like may correspond thereto. In particular, when the network node 1710 is a base station, the communication module 1713 may include a radio frequency unit (RF) for transmitting / receiving a radio signal.

The terminal 1720 includes a processor 1721, a memory 1722, and a communication module (or RF unit) 1723. The processor 1721 implements the functions, processes, and / or methods proposed in FIGS. 1 to 16. Layers of the air interface protocol may be implemented by the processor 1721. The memory 1722 is connected to the processor 1721 and stores various information for driving the processor 1721. The communication module 1723 is connected to the processor 1721 to transmit and / or receive a radio signal.

The memories 1712 and 1722 may be inside or outside the processors 1711 and 1721, and may be connected to the processors 1711 and 1721 by various well-known means. In addition, the network node 1710 (in the case of a base station) and / or the terminal 1720 may have a single antenna or multiple antennas.

18 illustrates a block diagram of a communication device according to an embodiment of the present invention.

In particular, FIG. 18 illustrates the terminal of FIG. 17 in more detail.

Referring to FIG. 18, a terminal may include a processor (or a digital signal processor (DSP) 1810, an RF module (or RF unit) 1835, and a power management module 1805). ), Antenna 1840, battery 1855, display 1815, keypad 1820, memory 1830, SIM card (SIM (Subscriber Identification Module) card) 1825 (this configuration is optional), a speaker 1845, and a microphone 1850. The terminal may also include a single antenna or multiple antennas. Can be.

The processor 1810 implements the functions, processes, and / or methods proposed in FIGS. 1 to 16. The layer of the air interface protocol may be implemented by the processor 1810.

The memory 1830 is connected to the processor 1810 and stores information related to the operation of the processor 1810. The memory 1830 may be inside or outside the processor 1810 and may be connected to the processor 1810 by various well-known means.

The user enters command information such as a telephone number, for example, by pressing (or touching) a button on keypad 1820 or by voice activation using microphone 1850. The processor 1810 receives the command information, processes the telephone number, and performs a proper function. Operational data may be extracted from the SIM card 1830 or the memory 1830. In addition, the processor 1810 may display command information or driving information on the display 1815 for user recognition and convenience.

The RF module 1835 is coupled to the processor 1810 to transmit and / or receive RF signals. The processor 1810 communicates command information to the RF module 1835 to initiate, for example, a radio signal constituting voice communication data. The RF module 1835 is composed of a receiver and a transmitter for receiving and transmitting a radio signal. The antenna 1840 functions to transmit and receive wireless signals. Upon receiving the wireless signal, the RF module 1835 may transmit the signal and convert the signal to baseband for processing by the processor 1810. The processed signal may be converted into audible or readable information output through the speaker 1845.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the 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. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in memory and driven by the processor. The memory may be located inside or outside the processor, and may exchange data with the processor by various known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

The method of performing PDN type fallback in the wireless communication system of the present invention has been described with reference to the example applied to the 3GPP LTE / LTE-A system, but is applicable to various wireless communication systems in addition to the 3GPP LTE / LTE-A system. It is possible.

Claims (12)

What is claimed is: 1. A method for a home subscriber server (HSS) in a wireless communication system to fall back a failed first Packet Data Network (PDN) type to a second PDN type capable of normal operation. , After detecting a failure of the first PDN type, if there is a terminal with voice call transmission and reception, all the PDN types allocated for the PDN connection established by the terminal are all the first PDN type. Determining whether it is cognitive; Detach with re-attach procedure with reattachment or disconnection with re-activation depending on whether all PDN types allocated to the PDN connection of the UE are the first PDN type. determining any one of an activation procedure; And Initiating the determined procedure. The method of claim 1, If the PDN type allocated to the PDN connection of the terminal all the first PDN type, Detach with re-attach (Petach with re-attach) procedure is determined. The method of claim 2, wherein the initiating step, As a cause value, a Location Cancel message including an HSS initiated detach or an IP version change or a PDN type change may be sent to a mobility management entity (MME). PDN type fallback method comprising the step of transmitting to (Mobility Management Entity). The method of claim 3, The MME is a PDN type fallback method belonging to the Visited Public Land Mobile Network (VPLMN). The method of claim 4, wherein The Cancel Location message indicates the first PDN type as a PDN type in which a failure occurs, or indicates the second PDN type as a PDN type that can operate normally. The method of claim 5, The terminal is connected to the PDN GW (Packet Data Network Gateway) for assigning the second PDN type by the MME during the attach procedure by the terminal. The method of claim 1, When all of the PDN types allocated to the PDN connection of the UE are not the first PDN type, a disconnection with re-activation procedure for the PDN to which the first PDN type is assigned is determined. PDN type fallback method. The method of claim 7, wherein the initiating step, PDN disconnection request with a relocation indication or a Cancel Location message containing a bearer deactivation with reactivation requested with a cause value ) PDN type fallback method comprising the step of sending a message to a mobility management entity (MME). The method of claim 8, The MME is a PDN type fallback method belonging to the Visited Public Land Mobile Network (VPLMN). The method of claim 9, The Cancel Location message indicates the first PDN type as a PDN type in which a failure occurs, or indicates the second PDN type as a PDN type that can operate normally. The method of claim 10, The PDN type fallback method is connected to the PDN GW (Packet Data Network Gateway) for assigning the second PDN type by the MME during the PDN connectivity (PDN Connectivity) procedure by the terminal. In the Home Subscriber Server (HSS) for falling back a first Packet Data Network (PDN) type that has failed in a wireless communication system to a second PDN type capable of normal operation, A communication module for transmitting and receiving a signal; And A processor for controlling the communication module, When the processor detects a failure of the first PDN type and there is a terminal with voice call transmission and reception, all of the PDN types allocated for the PDN connection established by the terminal are first selected. 1 PDN type, Detach with re-attach procedure with reattachment or disconnection with re-activation depending on whether all PDN types allocated to the PDN connection of the UE are the first PDN type. determine one of the activation procedures, An HSS configured to initiate the determined procedure.

Images