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WO2017104858A1 - Procédé pour réaliser une connexion s1 entre une station de base alternative et une entité de réseau dans un système de communication sans fil et appareil pour prendre en charge ce dernier - Google Patents

Procédé pour réaliser une connexion s1 entre une station de base alternative et une entité de réseau dans un système de communication sans fil et appareil pour prendre en charge ce dernier Download PDF

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Publication number
WO2017104858A1
WO2017104858A1 PCT/KR2015/013681 KR2015013681W WO2017104858A1 WO 2017104858 A1 WO2017104858 A1 WO 2017104858A1 KR 2015013681 W KR2015013681 W KR 2015013681W WO 2017104858 A1 WO2017104858 A1 WO 2017104858A1
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WIPO (PCT)
Prior art keywords
base station
terminal
alternative
message
link
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Ceased
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PCT/KR2015/013681
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English (en)
Korean (ko)
Inventor
한진백
조희정
이은종
변일무
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LG Electronics Inc
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LG Electronics Inc
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Priority to PCT/KR2015/013681 priority Critical patent/WO2017104858A1/fr
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Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W8/00—Network data management
    • H04W8/02—Processing of mobility data, e.g. registration information at HLR [Home Location Register] or VLR [Visitor Location Register]; Transfer of mobility data, e.g. between HLR, VLR or external networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup

Definitions

  • the present specification relates to a method for performing an S1 connection in a wireless communication system and an apparatus supporting the same.
  • Mobile communication systems have been developed to provide voice services while ensuring user activity.
  • the mobile communication system has expanded not only voice but also data service, and the explosive increase in traffic causes shortage of resources and users require faster services. Therefore, a more advanced mobile communication system is required. .
  • an available alternative base station is searched for available base stations that can be quickly replaced according to a channel condition of the UE or a switch to a corresponding alternative base station. There is a difficult problem to secure.
  • the terminal secures a plurality of alternative base stations, so that the channel condition of the serving base station link may be replaced.
  • a plurality of base stations are provided through a preemptive link quality indicator indication by the base station when the terminal initially accesses the network or when the bearer is set / released for the MCS, or when the link quality value of the base station is changed.
  • the UE establishes an S1 signaling connection between each alternative base station and the MME and sets an S1 bearer between each alternative base station and the S-GW, from the terminal to the S-GW.
  • the E-RAB and setting the S5 / S8 Bearer between the S-GW and the P-GW it is not defined how to set the EPS Bearer from the terminal to the P-GW.
  • the present specification provides a method for establishing an S1 signaling connection between alternative base stations and an MME and configuring an S1 bearer between alternative base stations and an S-GW when establishing a multi-connection for providing new 5G MCSs with high service availability.
  • an S1 signaling connection between alternative base stations and an MME and configuring an S1 bearer between alternative base stations and an S-GW when establishing a multi-connection for providing new 5G MCSs with high service availability.
  • the present specification provides a method for generating a security key for multiple connectivity and delivering it to each alternative base station so that the DRBs of alternative base stations configured by the S1 Bearer can be set up at all times in order to maximize the availability of the radio link when establishing the multiple connection.
  • a security key for multiple connectivity and delivering it to each alternative base station so that the DRBs of alternative base stations configured by the S1 Bearer can be set up at all times in order to maximize the availability of the radio link when establishing the multiple connection.
  • a method for performing an S1 connection between an alternative base station and a network entity in a wireless communication system comprising: establishing an alternative link between a terminal and the alternative base station, and the alternative link is a signaling radio bearer (SRB) Inactive state; Transmitting, by the serving base station, first indication information indicating whether the terminal is a mission critical service (MCS) capable terminal to the network entity; And performing an S1 connection between the alternative base station on which the alternative link is set and the network entity, wherein performing the S1 connection may include: an alternative base station for identifying, by the serving base station, an alternative base station on which the alternative link is set; Sending a first message to the network entity comprising a list of identifiers; Transmitting, by the network entity, a second message based on the first message to an alternative base station on which the alternative link is set, the second message includes an E-RAB between the alternative base station on which the alternative link is established and the terminal; At least one of E-RAB configuration information related to
  • the E-RAB configuration information may include at least one of third indication information indicating that the E-RAB ID, the E-RAB QoS, or the E-RAB configuration through an alternative base station.
  • the S1 signaling configuration information may include an MME UE S1 Application Protocol (S1AP) ID.
  • S1AP S1 Application Protocol
  • the serving base station further comprises the step of assigning the eNB UE S1AP ID to the terminal based on the received S1 signaling configuration information.
  • the present specification further comprises the step of transmitting, by the terminal, an RRC connection setup complete message including information related to an attach request to the serving base station. It features.
  • the information related to the attach request may include at least one of International Mobile Subscriber Identity (IMSI) or UE Network Capability information.
  • IMSI International Mobile Subscriber Identity
  • UE Network Capability information may be included in the attach request.
  • the first indication information is included in an initial UE message.
  • the present specification provides a method, comprising: receiving, by the serving base station, an Initial Context Setup Request message including UE context information from the network entity; And transmitting, by the serving base station, an initial context setup response message to the network entity.
  • the first message may include information related to attach complete.
  • the first security key is generated for each alternative base station to which the alternative link is set by the network entity.
  • the first security key is generated based on a second security key and a counter, and the second security key is generated when authentication of the terminal is successful, and the counter is generated by the terminal.
  • a counter that increases by '1' or by a 'specific value' according to the number of times of requesting multiple connectivity to an alternative base station maintained by the network entity.
  • the counter is set for each alternative base station, and the initial count value for each alternative base station is characterized in that the same or different values are applied.
  • the specific value in the present specification is characterized in that the terminal has a value equal to the number of alternative base station (s) requesting the multi-connection at a certain time.
  • the first security key is K eNB
  • the second security key is K ASME .
  • the first indication information is transmitted to the network entity before establishing the alternate link.
  • the present specification provides a method, comprising: transmitting, by the terminal, a report message for reporting that the quality of a serving link for an MCS is deteriorated to the serving base station; And setting the alternate link is performed after transmitting the report message.
  • the first indication information is transmitted to the network entity after setting the replacement link.
  • the present specification provides a method for performing an S1 connection between an alternative base station and a network entity in a wireless communication system, wherein the network entity is configured to support E-RAB (Mission Critical Service (MCS)) for mission critical service (MCS).
  • E-RAB Mobility Critical Service
  • MCS mission critical service
  • E-RAB setup request message includes an indicator indicating an alternate link setup between the terminal and the alternative base station; Includes; Establishing an alternate link between the terminal and the alternative base station based on the received E-RAB setup request message, wherein the alternative link is a Signaling Radio Bearer (SRB) inactive state; And performing an S1 connection between the alternative base station on which the alternative link is set and the network entity, wherein performing the S1 connection may include: an alternative base station for identifying, by the serving base station, an alternative base station on which the alternative link is set; Sending a first message to the network entity comprising a list of identifiers; Sending, by the network entity, a second message to an alternative base station configured with the alternative link based on the first message; And transmitting, by the alternate base station on which the alternate link is established, a response message for the second message to the network entity.
  • SRB Signaling Radio Bearer
  • the second message includes E-RAB configuration information related to E-UTRAN Radio Access Bearer (E-RAB) configuration of an alternative base station with which the alternative link is set and the terminal; And at least one of S1 signaling configuration information or a first security key related to S1 signaling connection establishment with the network entity.
  • E-RAB E-UTRAN Radio Access Bearer
  • the method may further include receiving, by the serving base station, second indication information indicating that the connection reason of the terminal is connection for MCS from the terminal.
  • the S1 signaling connection and the S1 bearer connection of a network section are established to provide connection availability and reliability for supporting MCS. There is an effect that can be secured.
  • the present specification when the terminal detects a change in its surrounding channel status, determines the best alternative link, by determining and when the important reliable communication that must satisfy both the short delay requirements and high reliability requirements at the same time, when There is an effect that can be realized wherever and whenever possible.
  • the present specification ensures that there is always an alternate available link adjacent to avoid link outage, so that it can quickly cope with link failure and connection failure, realize high reliability cloud connectivity, and improve the data rate for receiving MCSs. It can be effective.
  • FIG. 1 is a diagram illustrating an example of an EPS (Evolved Packet System) related to an LTE system to which the present invention can be applied.
  • EPS Evolved Packet System
  • FIG. 2 is a diagram illustrating a wireless communication system to which the present invention is applied.
  • FIG. 3 is a block diagram illustrating an example of a functional split between an E-UTRAN and an EPC to which the present invention can be applied.
  • 4A is a block diagram illustrating an example of a radio protocol architecture for a user plane to which technical features of the present specification can be applied.
  • 4B is a block diagram illustrating an example of a radio protocol structure for a control plane to which technical features of the present specification can be applied.
  • FIG. 5 is a diagram illustrating an S1 interface protocol structure in a wireless communication system to which the present invention can be applied.
  • FIG. 6 is a diagram illustrating EMM and ECM states in a wireless communication system to which the present invention can be applied.
  • FIG. 7 is a diagram illustrating a bearer structure in a wireless communication system to which the present invention can be applied.
  • FIG. 8 is a diagram illustrating a transmission path of a control plane and a user plane in an EMM registration state in a wireless communication system to which the present invention can be applied.
  • FIG. 9 illustrates an example of a dedicated bearer activation procedure.
  • FIG. 10 illustrates an example of a dedicated bearer deactivation procedure.
  • FIG. 11 is a diagram illustrating a handover procedure defined in LTE (-A).
  • FIG. 12 is a diagram illustrating an operation process of a terminal and a base station in a contention based random access procedure.
  • FIG. 13 is a flowchart illustrating an operation of a terminal in an RRC idle state to which the present invention can be applied.
  • FIG. 14 is a flowchart illustrating a process of establishing an RRC connection to which the present invention can be applied.
  • 15 is a flowchart illustrating a RRC connection resetting process to which the present invention can be applied.
  • 16 is a diagram illustrating an example of an RRC connection reestablishment procedure to which the present invention can be applied.
  • 17 is a flowchart illustrating an example of a measurement performing method to which the present invention can be applied.
  • FIG. 18 is a diagram illustrating a conceptual diagram of an alternative link to which the methods proposed herein may be applied.
  • 19 to 21 are flowcharts illustrating examples of a network indication based multilink configuration method proposed in the present specification.
  • 22 and 23 are flowcharts illustrating examples of a method of canceling a multilink proposed in the present specification.
  • 24 to 26 are flowcharts illustrating examples of a method of configuring an alternate link activation and an MCS bearer of an alternative base station according to a decrease in radio link quality of a serving base station proposed in the present specification.
  • 29 to 32 are flowcharts illustrating an example of a procedure for establishing an S1-C and S1-U connection with alternative base stations proposed herein.
  • 33 is a block diagram illustrating a wireless device in which the methods proposed herein may be implemented.
  • 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) is a fixed station (Node B), an evolved-NodeB (eNB), a base transceiver system (BTS), an access point (AP), a macro eNB (MeNB), a SeNB (SeNB). Secondary eNB).
  • 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.
  • UE user equipment
  • MS mobile station
  • UT user terminal
  • MSS mobile subscriber station
  • SS subscriber station
  • AMS Advanced Mobile Station
  • WT Wireless Terminal
  • MTC Machine-Type Communication
  • M2M Machine-to-Machine
  • D2D Device-to-Device
  • downlink means communication from a base station to a terminal
  • uplink means communication from a terminal to a base station.
  • a transmitter may be part of a base station, and a receiver may be part of a terminal.
  • a transmitter may be part of a terminal and a receiver may be part of a base station.
  • CDMA code division multiple access
  • FDMA frequency division multiple access
  • TDMA time division multiple access
  • OFDMA orthogonal frequency division multiple access
  • SC-FDMA single carrier frequency division multiple access
  • GSM global system for mobile communications
  • GPRS general packet radio service
  • EDGE enhanced data rates for GSM evolution
  • 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.
  • EPS stands for Evolved Packet System and means a core network supporting a Long Term Evolution (LTE) network.
  • LTE Long Term Evolution
  • UMTS evolved network
  • PDN Public Data Network
  • APN Access Point Name: A name of an access point managed in a network, which is provided to a UE. That is, the name (string) of the PDN. Based on the name of the access point, the corresponding PDN for the transmission and reception of data is determined.
  • Tunnel Endpoint Identifier An end point ID of a tunnel established between nodes in a network, and is set for each section in bearer units of each UE.
  • MME Mobility Management Entity
  • a session is a channel for data transmission.
  • the unit may be a PDN, a bearer, or an IP flow unit.
  • the difference in each unit can be divided into the entire target network unit (APN or PDN unit), the QoS classification unit (Bearer unit), and the destination IP address unit as defined in 3GPP.
  • APN or PDN unit the entire target network unit
  • QoS classification unit the QoS classification unit
  • destination IP address unit as defined in 3GPP.
  • PDN connection (connection) A connection from the terminal to the PDN, that is, the association (connection) between the terminal represented by the IP address and the PDN represented by the APN.
  • UE Context The context information of the UE used to manage the UE in the network, that is, the context information consisting of UE id, mobility (current location, etc.), and attributes of the session (QoS, priority, etc.)
  • P-TMSI Packet Temporary Mobile Subscriber
  • GTP GPRS Tunneling Protocol
  • TEID Tunnel Endpoint ID
  • GUTI Globally Unique Temporary Identity, UE identifier known to MME
  • FIG. 1 is a diagram illustrating an example of an EPS (Evolved Packet System) related to an LTE system to which the present invention can be applied.
  • EPS Evolved Packet System
  • the LTE system aims to provide seamless Internet Protocol connectivity between the user equipment (UE) and the packet data network (PDN) without interfering with the end user's use of the application on the go. .
  • the LTE system completes the evolution of wireless access through the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), which defines a radio protocol architecture between the user terminal and the base station, which is an Evolved Packet Core (EPC) network. It is also achieved through evolution in non-wireless terms by the inclusion of System Architecture Evolution (SAE).
  • SAE System Architecture Evolution
  • LTE and SAE include an Evolved Packet System (EPS).
  • EPS Evolved Packet System
  • the EPS uses the concept of EPS bearers to route IP traffic from the gateway to the user terminal in the PDN.
  • a bearer is an IP packet flow having a specific Quality of Service (QoS) between the gateway and the user terminal.
  • QoS Quality of Service
  • E-UTRAN and EPC both set up and release bearers required by the application.
  • EPC also called CN (core network)
  • CN core network
  • a node (logical or physical node) of an EPC of the SAE includes a mobility management entity (MME) 30, a PDN-GW or a PDN gateway (P-GW) 50, and an S-GW ( Serving Gateway (40), Policy and Charging Rules Function (PCRF) 60, Home Subscriber Server (HSS) 70, and the like.
  • MME mobility management entity
  • P-GW PDN gateway
  • S-GW Serving Gateway
  • PCRF Policy and Charging Rules Function
  • HSS Home Subscriber Server
  • the MME 30 is a control node that handles signaling between the UE and the CN.
  • the protocol exchanged between the UE and the CN is known as the Non-Access Stratum (NAS) protocol.
  • NAS Non-Access Stratum
  • Examples of functions supported by the MME 30 include functions related to bearer management operated by the session management layer in the NAS protocol, including network setup, management, and release of bearers, network and It is manipulated by the connectivity layer or mobility management layer in the NAS protocol layer, including the establishment of connection and security between UEs.
  • the S-GW 40 serves as a local mobility anchor for data bearers when the UE moves between base stations (eNodeBs). All user IP packets are sent via the S-GW 40.
  • the S-GW 40 may also temporarily downlink data while the UE is in an idle state known as the ECM-IDLE state and the MME initiates paging of the UE to re-establish the bearer. Maintain information about bearers when buffering. It also serves as a mobility anchor for inter-working with other 3GPP technologies such as General Packet Radio Service (GRPS) and Universal Mobile Telecommunications System (UMTS).
  • GRPS General Packet Radio Service
  • UMTS Universal Mobile Telecommunications System
  • the P-GW 50 performs IP address assignment for the UE and performs flow-based charging in accordance with QoS enforcement and rules from the PCRF 60.
  • the P-GW 50 performs QoS enforcement for GBR bearers (Guaranteed Bit Rate (GBR) bearers). It also serves as a mobility anchor for interworking with non-3GPP technologies such as CDMA2000 and WiMAX networks.
  • GBR bearers Guard Bit Rate (GBR) bearers
  • the PCRF 60 performs policy control decision-making and performs flow-based charging.
  • the HSS 70 is also called a home location register (HLR) and includes SAE subscription data including information on EPS-subscribed QoS profiles and access control for roaming. It also includes information about the PDN that the user accesses. This information may be maintained in the form of an Access Point Name (APN), which is a Domain Name system (DNS) -based label that identifies the PDN address that represents the access point or subscribed IP address for the PDN.
  • API Access Point Name
  • DNS Domain Name system
  • various interfaces such as S1-U, S1-MME, S5 / S8, S11, S6a, Gx, Rx, and SG may be defined between EPS network elements.
  • Mobility Management is a procedure to reduce overhead on the E-UTRAN and processing at the UE.
  • MME mobility management
  • the UE can inform the network about the new location whenever it leaves the current tracking area (TA) so that the network can contact the UE in the ECM-IDLE state.
  • This procedure may be called “Tracking Area Update”, which may be called “Routing Area Update” in universal terrestrial radio access network (UTRAN) or GSM EDGE Radio Access Network (GERAN) system.
  • the MME performs the function of tracking the user's location while the UE is in the ECM-IDLE state.
  • the MME transmits a paging message to all base stations (eNodeBs) on the tracking area (TA) where the UE is registered.
  • eNodeBs base stations
  • TA tracking area
  • the base station then begins paging for the UE over a radio interface.
  • a procedure for causing the state of the UE to transition to the ECM-CONNECTED state is performed.
  • This procedure can be called a “Service Request Procedure”. Accordingly, information related to the UE is generated in the E-UTRAN, and all bearers are re-established.
  • the MME is responsible for resetting the radio bearer and updating the UE context on the base station.
  • a mobility management (MM) backoff timer may be further used.
  • the UE may transmit a tracking area update (TAU) to update the TA, and the MME may reject the TAU request due to core network congestion, in which case the MM backoff timer You can provide a time value.
  • the UE may activate the MM backoff timer.
  • TAU tracking area update
  • FIG. 2 shows a wireless communication system to which the present invention is applied.
  • E-UTRAN Evolved-UMTS Terrestrial Radio Access Network
  • LTE Long Term Evolution
  • the E-UTRAN includes a base station (BS) 20 that provides a control plane and a user plane to a user equipment (UE).
  • BS base station
  • UE user equipment
  • the base stations 20 may be connected to each other through an X2 interface.
  • the base station 20 is connected to a Serving Gateway (S-GW) through a Mobility Management Entity (MME) and an S1-U through an Evolved Packet Core (EPC), more specifically, an S1-MME through an S1 interface.
  • S-GW Serving Gateway
  • MME Mobility Management Entity
  • EPC Evolved Packet Core
  • EPC consists of MME, S-GW and Packet Data Network Gateway (P-GW).
  • the MME has information about the access information of the terminal or the capability of the terminal, and this information is mainly used for mobility management of the terminal.
  • S-GW is a gateway having an E-UTRAN as an endpoint
  • P-GW is a gateway having a PDN as an endpoint.
  • Layers of the Radio Interface Protocol between the terminal and the network are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems.
  • L2 second layer
  • L3 third layer
  • the RRC Radio Resource Control
  • the RRC layer located in the third layer plays a role of controlling radio resources between the terminal and the network. To this end, the RRC layer exchanges an RRC message between the terminal and the base station.
  • FIG. 3 is a block diagram illustrating an example of a functional split between an E-UTRAN and an EPC to which the present invention can be applied.
  • hatched blocks represent radio protocol layers and empty blocks represent functional entities in the control plane.
  • the base station performs the following functions.
  • Radio resource management such as radio bearer control, radio admission control, connection mobility control, and dynamic resource allocation to a terminal RRM
  • IP Internet Protocol
  • IP Internet Protocol
  • Scheduling and transmission (5) scheduling and transmission of broadcast information, and (6) measurement and measurement report setup for mobility and scheduling.
  • the MME performs the following functions. (1) distribution of paging messages to base stations, (2) Security Control, (3) Idle State Mobility Control, (4) SAE Bearer Control, (5) NAS ( Ciphering and Integrity Protection of Non-Access Stratum Signaling.
  • S-GW performs the following functions. (1) termination of user plane packets for paging, and (2) user plane switching to support terminal mobility.
  • FIG. 4A illustrates an example of a radio protocol architecture for a user plane to which technical features of the present specification can be applied
  • FIG. 4B illustrates a control plane to which technical features of the present specification can be applied.
  • the user plane is a protocol stack for user data transmission
  • the control plane is a protocol stack for control signal transmission.
  • a physical layer (PHY) layer provides an information transfer service to a higher layer using a physical channel.
  • the physical layer is connected to a medium access control (MAC) layer, which is an upper layer, through a transport channel. Data is moved 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.
  • MAC medium access control
  • the physical channel may be modulated by an orthogonal frequency division multiplexing (OFDM) scheme and utilizes time and frequency as radio resources.
  • OFDM orthogonal frequency division multiplexing
  • the function of the MAC layer is mapping between logical channels and transport channels and multiplexing / demultiplexing ('/') into transport blocks provided as physical channels on transport channels of MAC service data units (SDUs) belonging to the logical channels. Meaning includes both the concepts of 'or' and 'and').
  • the MAC layer provides a service to a Radio Link Control (RLC) layer through a logical channel.
  • RLC Radio Link Control
  • RLC layer Functions of the RLC layer include concatenation, segmentation, and reassembly of RLC SDUs.
  • QoS Quality of Service
  • the RLC layer has a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (Acknowledged Mode).
  • TM transparent mode
  • UM unacknowledged mode
  • Acknowledged Mode acknowledged mode
  • AM Three modes of operation (AM).
  • AM RLC provides error correction through an automatic repeat request (ARQ).
  • the RRC (Radio Resource Control) layer is defined only in the control plane.
  • the RRC layer is responsible for the control of logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers.
  • RB means a logical path provided by the first layer (PHY layer) and the second layer (MAC layer, RLC layer, PDCP layer) for data transmission between the terminal and the network.
  • PDCP Packet Data Convergence Protocol
  • Functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include delivery of user data, header compression, and ciphering.
  • the functionality of the Packet Data Convergence Protocol (PDCP) layer in the control plane includes the transfer of control plane data and encryption / integrity protection.
  • the establishment of the RB means a process of defining characteristics of a radio protocol layer and a channel to provide a specific service, and setting each specific parameter and operation method.
  • RB can be further divided into SRB (Signaling RB) and DRB (Data RB).
  • SRB is used as a path for transmitting RRC messages in the control plane
  • DRB is used as a path for transmitting user data in the user plane.
  • the UE If an RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in an RRC connected state, otherwise it is in an RRC idle state.
  • the downlink transmission channel for transmitting data from the network to the UE includes a BCH (Broadcast Channel) for transmitting system information and a downlink shared channel (SCH) for transmitting user traffic or control messages.
  • Traffic or control messages of a downlink multicast or broadcast service may be transmitted through a downlink SCH or may be transmitted through a separate downlink multicast channel (MCH).
  • the uplink transport channel for transmitting data from the terminal to the network includes a random access channel (RACH) for transmitting an initial control message and an uplink shared channel (SCH) for transmitting user traffic or control messages.
  • RACH random access channel
  • SCH uplink shared channel
  • BCCH broadcast control channel
  • PCCH paging control channel
  • CCCH common control channel
  • MCCH multicast control channel
  • MTCH multicast traffic
  • the physical channel is composed of several OFDM symbols in the time domain and several sub-carriers in the frequency domain.
  • One sub-frame consists of a plurality of OFDM symbols in the time domain.
  • the RB is a resource allocation unit and includes a plurality of OFDM symbols and a plurality of subcarriers.
  • each subframe may use specific subcarriers of specific OFDM symbols (eg, the first OFDM symbol) of the corresponding subframe for the physical downlink control channel (PDCCH), that is, the L1 / L2 control channel.
  • Transmission Time Interval is a unit time of subframe transmission.
  • FIG. 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
  • FIG. 5B illustrates a user plane interface protocol structure in an S1 interface.
  • 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.
  • SCTP Stream Control Transmission Protocol
  • 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.
  • PDU protocol data unit
  • a single SCTP association per S1-MME interface instance uses a pair of stream identifiers for the S1-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.
  • 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.
  • GTP-U GPRS Tunneling Protocol User Plane
  • EMM EPS mobility management
  • ECM EPS connection management
  • FIG. 6 is a diagram illustrating EMM and ECM states in a wireless communication system to which the present invention can be applied.
  • 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.
  • 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.
  • 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.
  • ECM-connected state and an ECM idle state 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.
  • 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.
  • the terminal 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.
  • DRX Discontinuous Reception
  • 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.
  • the terminal 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.
  • TAU tracking area update
  • 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.
  • the terminal needs to transition to the ECM-CONNECTED state in order to receive a normal mobile communication service such as voice or data.
  • the initial terminal is in the ECM-IDLE state as in the EMM state.
  • the terminal and the MME are in the ECM connection state. Transition is made.
  • 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.
  • FIG. 7 illustrates a bearer structure in a wireless communication system to which the present invention can be applied.
  • PDN packet date network
  • EPS Packet Data Network
  • 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.
  • E-RAB E-UTRAN radio access bearer
  • S5 / S8 bearer an S5 / S8 bearer
  • RB radio bearer
  • 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).
  • LBI Linked EPS Bearer Identity
  • 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.
  • 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.
  • 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.
  • PCC Policy and Charging Control Function
  • PCEF Policy and Charging Enforcement Function
  • 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 QoS Class Identifier
  • ARP Allocation and Retention Priority
  • 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.
  • a scalar may be preset to any one of integer values 1-9.
  • ARP 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.
  • 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).
  • MBR MBR: Aggregated MBR
  • AMBR Aggregated MBR
  • 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.
  • FIG. 8 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.
  • FIG. 8A illustrates an ECM-CONNECTED state and FIG. 8B illustrates an ECM-IDLE.
  • the terminal When the terminal successfully attaches to the network and becomes the EMM-Registered state, the terminal receives the service using the EPS bearer.
  • the EPS bearer is configured by divided into DRB, S1 bearer, S5 bearer for each interval.
  • a NAS signaling connection that is, an ECM connection (that is, an RRC connection and an S1 signaling connection) is established.
  • 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.
  • GTP-C GPRS Tunneling Protocol Control Plane
  • the DRB, S1 bearer, and S5 bearer are all configured (ie, radio or network resource allocation).
  • the ECM connection (that is, the RRC connection and the S1 signaling connection) is released.
  • 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.
  • both the DRB and the S1 bearer are released, but the S5 bearer maintains the configuration (ie, radio or network resource allocation).
  • FIG. 9 illustrates an example of a dedicated bearer activation procedure.
  • FIG. 9 is a flowchart illustrating a dedicated bearer activation procedure for S5 / S8 based on GPRS Tunneling Protocol (GTP).
  • GTP GPRS Tunneling Protocol
  • the PCRF transmits a PCC decision provision (QoS policy) message to the PDN GW.
  • QoS policy PCC decision provision
  • the PDN GW transmits a Create Bearer Request message (IMSI, PTI, EPS Bearer QoS, TFT, S5 / S8 TEID, Charging Id, LBI, Protocol Configuration Options) for requesting bearer creation to the Serving GW.
  • IMSI Create Bearer Request message
  • PTI Packet Control
  • EPS Bearer QoS Packet Control Service
  • TFT Time Division Multiple Access
  • S5 / S8 TEID Charging Id
  • LBI Protocol Configuration Options
  • the Serving GW transmits the Create Bearer Request (IMSI, PTI, EPS Bearer QoS, TFT, S1-TEID, PDN GW TEID (GTP-based S5 / S8), LBI, Protocol Configuration Options) message to the MME.
  • IMSI Create Bearer Request
  • PTI Packet Control
  • EPS Bearer QoS Packet Control Service
  • TFT Time Division Multiple Access
  • S1-TEID Packet Control Protocol
  • PDN GW TEID GTP-based S5 / S8
  • LBI Protocol Configuration Options
  • the MME sends a Bearer Setup Request (EPS Bearer Identity, EPS Bearer QoS, Session Management Request, S1-TEID) message for requesting bearer setup to the eNodeB.
  • EPS Bearer Identity EPS Bearer Identity
  • EPS Bearer QoS EPS Bearer QoS
  • Session Management Request S1-TEID
  • the eNodeB transmits an RRC Connection Reconfiguration (Radio Bearer QoS, Session Management Request, EPS RB Identity) message to the UE.
  • RRC Connection Reconfiguration Radio Bearer QoS, Session Management Request, EPS RB Identity
  • the UE transmits an RRC Connection Reconfiguration Complete message to the eNodeB to inform radio bearer activation.
  • the eNodeB transmits a Bearer Setup Response (EPS Bearer Identity, S1-TEID) message to the MME to inform the radio bearer activation of the terminal.
  • EPS Bearer Identity S1-TEID
  • the UE transmits a Direct Transfer (Session Management Response) message to the eNodeB.
  • a Direct Transfer Session Management Response
  • the eNodeB transmits an Uplink NAS Transport (Session Management Response) message to the MME.
  • Uplink NAS Transport Session Management Response
  • the MME transmits a Create Bearer Response (EPS Bearer Identity, S1-TEID, User Location Information (ECGI)) message to the Serving GW to inform the bearer activation to the Serving GW.
  • EPS Bearer Identity S1-TEID
  • ECGI User Location Information
  • the Serving GW transmits a Create Bearer Response (EPS Bearer Identity, S5 / S8-TEID, User Location Information (ECGI)) message to the PDN GW in order to inform bearer activation to the PDN GW.
  • EPS Bearer Identity S5 / S8-TEID, User Location Information (ECGI)
  • the PDN GW indicates to the PCRF whether a requested PCC decision (QoS policy) has been performed.
  • FIG. 10 illustrates an example of a dedicated bearer deactivation procedure.
  • FIG. 10 is a flowchart illustrating a dedicated bearer deactivation procedure for S5 / S8 based on GPRS Tunneling Protocol (GTP).
  • GTP GPRS Tunneling Protocol
  • the procedure of FIG. 10 may be used to deactivate a dedicated bearer or to deactivate all bearers belonging to a PDN address.
  • the PDN GW deactivates all bearers belonging to the PDN connection. A detailed procedure will be described with reference to FIG. 10.
  • 11 illustrates a handover procedure defined in LTE.
  • 11 shows a case in which the MME and the serving gateway are not changed.
  • the detailed handover process is as follows and can refer to 3GPP Technical Specification (TS) 36.300.
  • Step 0 The terminal context in the source base station eNB includes information regarding roaming restrictions given at connection establishment or recent TA update.
  • Step 1 The source base station configures a terminal measurement process according to area restriction information.
  • the measurements provided by the source base station may help to control the connection mobility of the terminal.
  • Step 2 The terminal is triggered to send the measurement report according to the rules set by the (system information, etc.).
  • Step 3 The source base station determines whether to handover the terminal based on the measurement report and RRM (Radio Resource Management) information.
  • RRM Radio Resource Management
  • Step 4 The source base station transmits information required for handover (HO) to the target base station through a handover request message.
  • Information required for handover includes a terminal X2 signaling context reference, a terminal S1 EPC signaling context reference, a target cell ID, an RRC context including an identifier of a terminal (eg, a Cell Radio Network Temporary Identifier (CRNTI)) in a source base station, and the like. do.
  • Step 6 The target base station prepares a HO with L1 / L2 and sends a Handover Request Ack (ACKNOWLEDGE) message to the source base station.
  • the handover request Ack message includes a transparent container (RRC message) that is transmitted to the terminal to perform handover.
  • the container contains the new C-RNTI, the security algorithm identifier of the target base station.
  • the container may further include additional parameters such as connection parameters, SIBs, and the like.
  • the target base station divides the RA signatures into a non-contention based RA signature set (hereinafter, group 1) and a competition based RA signature set (hereinafter, group 2) in order to minimize handover delay,
  • group 1 a non-contention based RA signature set
  • group 2 a competition based RA signature set
  • One of the group 1 may be selected and informed to the handover terminal.
  • the container may further include information about the dedicated RA signature.
  • the container may also include information about the RACH slot duration to use the dedicated RA signature.
  • Step 7 The source base station generates an RRC message (eg, RRCConnectionReconfiguration message) having mobility control information for the terminal to perform the handover and transmits it to the terminal.
  • RRC message eg, RRCConnectionReconfiguration message
  • the RRCConnectionReconfiguration message contains parameters necessary for handover (eg, a new C-RNTI, a security algorithm identifier of the target base station, and optionally information on a dedicated RACH signature, a target base station SIB, etc.) and instructs HO to be performed.
  • parameters necessary for handover eg, a new C-RNTI, a security algorithm identifier of the target base station, and optionally information on a dedicated RACH signature, a target base station SIB, etc.
  • Step 8 The source base station transmits a serial number (SN) STATUS TRANSFER message to the target base station to transmit an uplink PDCP SN reception state and a downlink PDCP SN transmission state.
  • SN serial number
  • Step 9 After receiving the RRCConnectionReconfiguration message, the UE attempts to access the target cell using the RACH procedure.
  • the RACH proceeds on a non-competition basis if a dedicated RACH preamble is assigned, otherwise proceeds on a contention basis.
  • Step 10 The network performs uplink allocation and timing adjustment.
  • Step 11 When the UE successfully accesses the target cell, the UE sends an RRCConnectionReconfigurationComplete message (CRNTI) to confirm the handover and sends an uplink buffer status report to inform the target base station that the handover process is completed.
  • the target base station confirms the received C-RNTI through a Handover Confirm message and starts data transmission to the terminal.
  • Step 12 The target base station sends a path switch message to the MME to inform that the terminal has changed the cell.
  • Step 13 The MME sends a User Plane Update Request message to the serving gateway.
  • Step 14 The serving gateway switches the downlink data path to the target side.
  • the serving gateway transmits an end marker packet to the source base station through the existing path, and then releases user plane / TNL resources for the source base station.
  • Step 15 The serving gateway sends a User Plane Update Response message to the MME.
  • Step 16 The MME responds to the path switch message using the path switch Ack message.
  • Step 17 The target base station sends a UE context release message to inform the source base station of the success of the HO and triggers resource release.
  • Step 18 Upon receiving the terminal context release message, the source base station releases the radio resources and user plane related resources associated with the terminal context.
  • FIG. 12 is a diagram illustrating an operation process of a terminal and a base station in a contention based random access procedure.
  • a UE randomly selects one random access preamble from a set of random access preambles indicated by system information or a handover command, and transmits the random access preamble.
  • the resource may be selected and transmitted (S1201).
  • the method of receiving the random access response information is similar to that in the aforementioned non- contention based random access procedure. That is, after the UE transmits the random access preamble as in step S1201, the base station attempts to receive its random access response within the random access response reception window indicated by the system information or the handover command, and corresponds to the corresponding RA.
  • the PDSCH is received through the RNTI information (S1202). Through this, an UL grant, a temporary C-RNTI, a timing synchronization command (TAC), and the like may be received.
  • TAC timing synchronization command
  • the terminal When the terminal receives a random access response valid 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 temporary C-RNTI.
  • the UL grant transmits data (ie, a third message) to the base station (S1203).
  • the third message should include the identifier of the terminal.
  • the base station In the contention-based random access process, the base station cannot determine which terminals perform the random access process, because the terminal needs to be identified for future collision resolution.
  • Two methods have been discussed as a method of including the identifier of the terminal.
  • the first method if the UE already has a valid cell identifier assigned to the cell before the random access procedure, the UE transmits its cell identifier through an uplink transmission signal corresponding to the UL grant.
  • the terminal transmits its own unique identifier (eg, S-TMSI or random ID). In general, the unique identifier is longer than the cell identifier.
  • the terminal transmits data corresponding to the UL grant, it starts a timer for contention resolution (contention resolution timer).
  • the terminal After the terminal transmits data including its identifier through the UL grant included in the random access response, the terminal waits for instructions from the base station to resolve the collision. That is, an attempt is made to receive a PDCCH in order to receive a specific message (S1204). Two methods have been discussed in the method of receiving the PDCCH. As mentioned above, when the third message transmitted in response to the UL grant is transmitted using a cell identifier of its own, it attempts to receive the PDCCH using its cell identifier, and the identifier is a unique identifier. In this case, it may attempt to receive the PDCCH using the temporary C-RNTI included in the random access response.
  • the terminal determines that the random access procedure has been normally performed, and terminates the random access procedure.
  • the terminal determines that the random access procedure has been normally performed, and terminates the random access procedure.
  • the RRC state refers to whether or not the RRC layer of the UE is in a logical connection with the RRC layer of the E-UTRAN. If connected, the RRC connection state is called. Since the UE in the RRC connected state has an RRC connection, the E-UTRAN can grasp the existence of the corresponding UE in a cell unit, and thus can effectively control the UE.
  • the UE of the RRC idle state cannot be recognized by the E-UTRAN, and is managed by the CN (core network) in units of a tracking area, which is a larger area unit than a cell. That is, the UE in the RRC idle state is identified only in a large area unit, and must move to the RRC connected state in order to receive a normal mobile communication service such as voice or data.
  • the terminal When the user first powers on the terminal, the terminal first searches for an appropriate cell and then stays in an RRC idle state in the cell.
  • the UE in the RRC idle state needs to establish an RRC connection, it establishes an RRC connection with the E-UTRAN through an RRC connection procedure and transitions to the RRC connected state.
  • RRC connection procedure There are several cases in which the UE in RRC idle state needs to establish an RRC connection. For example, an uplink data transmission is necessary due to a user's call attempt, or a paging message is sent from E-UTRAN. If received, a response message may be sent.
  • the non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.
  • EMM-REGISTERED EPS Mobility Management-REGISTERED
  • EMM-DEREGISTERED EMM-DEREGISTERED
  • 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 attach procedure is successfully performed, the UE and the MME are in the EMM-REGISTERED state.
  • ECM EPS Connection Management
  • ECM-CONNECTED ECM-CONNECTED
  • the MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes an S1 connection with the E-UTRAN.
  • the E-UTRAN does not have context information of the terminal. Accordingly, the UE in the ECM-IDLE state performs a terminal-based mobility related procedure such as cell selection or cell reselection without receiving a command from the network.
  • the terminal when the terminal is in the ECM-CONNECTED state, the mobility of the terminal is managed by the command of the network.
  • the terminal informs the network of the corresponding position of the terminal through a tracking area update procedure.
  • the system information includes essential information that the terminal needs to know in order to access the base station. Therefore, the terminal must receive all system information before accessing the base station, and must always have the latest system information. In addition, since the system information is information that all terminals in a cell should know, the base station periodically transmits the system information.
  • the system information includes a master information block (MIB) and a scheduling block (SB). It is divided into SIB (System Information Block).
  • MIB master information block
  • SB scheduling block
  • the MIB enables the UE to know the physical configuration of the cell, for example, bandwidth.
  • SB informs transmission information of SIBs, for example, a transmission period.
  • SIB is a collection of related system information. For example, some SIBs contain only information of neighboring cells, and some SIBs contain only information of an uplink radio channel used by the terminal.
  • services provided by a network to a terminal can be classified into three types as follows.
  • the terminal also recognizes the cell type differently according to which service can be provided. The following describes the service type first, followed by the cell type.
  • Limited service This service provides Emergency Call and Tsunami Warning System (ETWS) and can be provided in an acceptable cell.
  • ETWS Emergency Call and Tsunami Warning System
  • Normal service This service means a public use for general use, and can be provided in a suitable or normal cell.
  • This service means service for network operator. This cell can be used only by network operator and not by general users.
  • the cell types may be classified as follows.
  • Acceptable cell A cell in which the terminal can receive limited service. This cell is a cell that is not barred from the viewpoint of the terminal and satisfies the cell selection criteria of the terminal.
  • Suitable cell The cell that the terminal can receive a regular service. This cell satisfies the conditions of an acceptable cell, while at the same time satisfying additional conditions. As an additional condition, this cell must belong to a Public Land Mobile Network (PLMN) to which the terminal can access, and must be a cell which is not prohibited from performing a tracking area update procedure of the terminal. If the cell is a CSG cell, the terminal should be a cell that can be connected to the cell as a CSG member.
  • PLMN Public Land Mobile Network
  • Barred cell A cell that broadcasts information that a cell is a prohibited cell through system information.
  • Reserved cell A cell that broadcasts information that a cell is a reserved cell through system information.
  • FIG. 13 is a flowchart illustrating an operation of a terminal in an RRC idle state to which the present invention can be applied.
  • FIG. 13 illustrates a procedure in which an initially powered-on UE registers with a network through a cell selection process and then reselects a cell if necessary.
  • the terminal selects a radio access technology (RAT) for communicating with a public land mobile network (PLMN), which is a network to be serviced (S1310).
  • RAT radio access technology
  • PLMN public land mobile network
  • S1310 a network to be serviced
  • Information about the PLMN and the RAT may be selected by a user of the terminal or may be stored in a universal subscriber identity module (USIM).
  • USIM universal subscriber identity module
  • the terminal selects a cell having the largest value among the measured base station and a cell whose signal strength or quality is greater than a specific value (Cell Selection) (S1320). This is referred to as initial cell selection by the UE that is powered on to perform cell selection. The cell selection procedure will be described later.
  • the terminal receives system information periodically transmitted by the base station.
  • the above specific value refers to a value defined in the system in order to ensure the quality of the physical signal in data transmission / reception. Therefore, the value may vary depending on the RAT applied.
  • the terminal performs a network registration procedure (S1330).
  • the terminal registers its information (eg IMSI) in order to receive a service (eg paging) from the network.
  • IMSI information
  • a service eg paging
  • the UE Whenever a cell is selected, the UE does not register with the accessing network. If the UE does not register the network information (for example, tracking area identity (TAI)) received from the system information and the network information that it knows is registered, it registers with the network. do.
  • TAI tracking area identity
  • the terminal performs cell reselection based on the service environment provided by the cell or the environment of the terminal (S1340).
  • the terminal selects one of the other cells that provides better signal characteristics than the cell of the base station to which the terminal is connected if the strength or quality of the signal measured from the base station being service is lower than the value measured from the base station of the adjacent cell. do.
  • This process is called Cell Re-Selection, which is distinguished from Initial Cell Selection of Step 2.
  • a time constraint is placed. The cell reselection procedure will be described later.
  • FIG. 14 is a flowchart illustrating a process of establishing an RRC connection to which the present invention can be applied.
  • the terminal sends an RRC connection request message to the network requesting an RRC connection (S1410).
  • the network sends an RRC connection setup message in response to the RRC connection request (S1420). After receiving the RRC connection configuration message, the terminal enters the RRC connection mode.
  • the UE sends an RRC Connection Setup Complete message used to confirm successful completion of RRC connection establishment to the network (S1430).
  • 15 is a flowchart illustrating a RRC connection resetting process to which the present invention can be applied.
  • RRC connection reconfiguration is used to modify an RRC connection. It is used to establish / modify / release RBs, perform handovers, and set up / modify / release measurements.
  • the network sends an RRC connection reconfiguration message for modifying the RRC connection to the terminal (S1510).
  • the UE sends an RRC connection reconfiguration complete message used to confirm successful completion of the RRC connection reconfiguration to the network (S1520).
  • the terminal selects / reselects a cell of appropriate quality and performs procedures for receiving service.
  • the UE in the RRC idle state should always select a cell of appropriate quality and prepare to receive service through this cell. For example, a terminal that has just been powered on must select a cell of appropriate quality to register with the network. When the terminal in the RRC connected state enters the RRC idle state, the terminal should select a cell to stay in the RRC idle state. As such, the process of selecting a cell satisfying a certain condition in order for the terminal to stay in a service standby state such as an RRC idle state is called cell selection. Importantly, since the cell selection is performed in a state in which the UE does not currently determine a cell to stay in the RRC idle state, it is most important to select the cell as soon as possible.
  • the cell may be selected during the cell selection process of the terminal.
  • an initial cell selection process in which the terminal does not have prior information on the radio channel. Accordingly, the terminal searches all radio channels to find an appropriate cell. In each channel, the terminal finds the strongest cell. Thereafter, the terminal selects a corresponding cell if it finds a suitable cell that satisfies a cell selection criterion.
  • the terminal may select the cell by using the stored information or by using the information broadcast in the cell.
  • cell selection can be faster than the initial cell selection process.
  • the UE selects a corresponding cell if it finds a cell that satisfies a cell selection criterion. If a suitable cell that satisfies the cell selection criteria is not found through this process, the UE performs an initial cell selection process.
  • the terminal After the terminal selects a cell through a cell selection process, the strength or quality of a signal between the terminal and the base station may change due to a change in mobility or a wireless environment of the terminal. Therefore, if the quality of the selected cell is degraded, the terminal may select another cell that provides better quality. When reselecting a cell in this way, a cell that generally provides better signal quality than the currently selected cell is selected.
  • the cell reselection process has a basic purpose in selecting a cell that generally provides the best quality to a terminal in view of the quality of a radio signal.
  • the network may determine the priority for each frequency and notify the terminal. Upon receiving this priority, the UE considers this priority prior to the radio signal quality criteria in the cell reselection process.
  • a method of selecting or reselecting a cell according to a signal characteristic of a wireless environment In selecting a cell for reselection when reselecting a cell, the following cell reselection is performed according to a cell's RAT and frequency characteristics. There may be a method of selection.
  • Intra-frequency cell reselection Reselection of a cell having a center-frequency equal to the RAT, such as a cell in which the UE is camping
  • Inter-frequency cell reselection Reselects a cell having a center frequency different from that of the same RAT as the cell camping
  • Inter-RAT cell reselection The UE reselects a cell that uses a different RAT from the camping RAT.
  • the UE measures the quality of a serving cell and a neighboring cell for cell reselection.
  • cell reselection is performed based on cell reselection criteria.
  • the cell reselection criteria have the following characteristics with respect to serving cell and neighbor cell measurements.
  • Intra-frequency cell reselection is basically based on ranking.
  • Ranking is an operation of defining index values for cell reselection evaluation and using the index values to order the cells in order of the index values.
  • the cell with the best indicator is often called the best ranked cell.
  • the cell index value is a value obtained by applying a frequency offset or a cell offset as necessary based on the value measured by the terminal for the corresponding cell.
  • Inter-frequency cell reselection is based on the frequency priority provided by the network.
  • the terminal attempts to camp on the frequency with the highest frequency priority.
  • the network may provide the priorities to be commonly applied to the terminals in the cell or provide the frequency priority through broadcast signaling, or may provide the priority for each frequency for each terminal through dedicated signaling.
  • the cell reselection priority provided through broadcast signaling may be referred to as common priority, and the cell reselection priority set by the network for each terminal may be referred to as a dedicated priority.
  • the terminal may also receive a validity time associated with the dedicated priority.
  • the terminal starts a validity timer set to the valid time received together.
  • the terminal applies the dedicated priority in the RRC idle mode while the validity timer is running.
  • the validity timer expires, the terminal discards the dedicated priority and applies the public priority again.
  • the network may provide the UE with a parameter (for example, frequency-specific offset) used for cell reselection for each frequency.
  • a parameter for example, frequency-specific offset
  • the network may provide the UE with a neighboring cell list (NCL) used for cell reselection.
  • NCL neighboring cell list
  • This NCL contains cell-specific parameters (eg cell-specific offsets) used for cell reselection.
  • the network may provide the UE with a cell reselection prohibition list (black list) used for cell reselection.
  • the UE does not perform cell reselection for a cell included in the prohibition list.
  • RLM Radio Link Monitoring
  • the terminal monitors the downlink quality based on a cell-specific reference signal to detect the downlink radio link quality of the PCell.
  • the UE estimates the downlink radio link quality for PCell downlink radio link quality monitoring purposes and compares it with thresholds Qout and Qin.
  • the threshold Qout is defined as the level at which the downlink radio link cannot be stably received, which corresponds to a 10% block error rate of hypothetical PDCCH transmission in consideration of the PDFICH error.
  • the threshold Qin is defined as a downlink radio link quality level that can be received more stably than the level of Qout, which corresponds to a 2% block error rate of virtual PDCCH transmission in consideration of PCFICH errors.
  • RLF Radio Link Failure
  • the UE continuously measures to maintain the quality of the radio link with the serving cell receiving the service.
  • the terminal determines whether communication is impossible in the current situation due to deterioration of the quality of the radio link with the serving cell.
  • the terminal determines the current situation as a radio link failure.
  • the UE abandons communication with the current serving cell, selects a new cell through a cell selection (or cell reselection) procedure, and reestablishes an RRC connection to the new cell (RRC connection re). -establishment).
  • the UE may determine that the RLF has occurred when the following problems occur in the radio link.
  • the UE may determine that out-of-sync has occurred in the physical channel when the quality of a reference signal (RS) periodically received from the eNB in the physical channel is detected below a threshold. If such out-of-sync occurs continuously by a certain number (eg, N310), it is notified to RRC. Receiving an out-of-sync message from the physical layer, the RRC runs the timer T310 and waits for the physical channel to be resolved while the T310 is running. If RRC receives a message from the physical layer that a certain number of consecutive in-syncs have occurred (eg, N311) while the T310 is running, the RRC determines that the physical channel problem has been resolved and stops the running T310. Let's do it. However, if the in-sync message is not received until T310 expires, the RRC determines that an RLF has occurred.
  • RS reference signal
  • random access resource selection-> random access preamble transmission-> random access response reception-> contention cancellation Go through the process of (Contention Resolution).
  • the entire process is referred to as one random access process. If this process is not completed successfully, the user waits for the back off time and performs the next random access process. However, if this random access process is attempted a predetermined number of times (eg, preambleTransMax) but is not successful, it is notified to the RRC, and the RRC determines that the RLF has occurred.
  • preambleTransMax a predetermined number of times
  • the UE retransmits an RLC PDU that is not successfully transmitted when using an AM (Acknowledged Mode) RLC in the RLC layer.
  • AM Acknowledged Mode
  • the RRC informs the RRC, and the RRC determines that an RLF has occurred.
  • RRC determines the occurrence of RLF due to the above three causes.
  • the RRC connection reestablishment which is a procedure for reestablishing the RRC connection with the eNB, is performed.
  • the RRC connection reestablishment process which is performed when RLF occurs, is as follows.
  • RRC connection reestablishment process If the UE determines that a serious problem has occurred in the RRC connection itself, to perform the RRC connection reestablishment process to reestablish the connection with the eNB.
  • RLF Radio Link Failure
  • Handover Failure (3) Mobility from E-UTRA
  • PDCP Integrity PDCP Integrity Check Failure (5) RRC Connection Reconfiguration Failure.
  • the terminal drives the timer T311 and starts the RRC connection reestablishment process. During this process, the UE accesses a new cell through cell selection and random access procedures.
  • the terminal stops T311 and starts a random access procedure to the corresponding cell. However, if no suitable cell is found until T311 expires, the UE determines that the RRC connection has failed and transitions to the RRC_IDLE mode.
  • 16 is a diagram illustrating an example of an RRC connection reestablishment procedure to which the present invention can be applied.
  • the UE stops using all radio bearers that have been set except SRB 0 (Signaling Radio Bearer # 0) and initializes various sub-layers of an AS (Access Stratum). (S1610). In addition, each sublayer and physical layer are set to a default configuration. During this process, the UE maintains an RRC connection state.
  • SRB 0 Synignaling Radio Bearer # 0
  • AS Access Stratum
  • the UE performs a cell selection procedure for performing an RRC connection reestablishment procedure (S1620).
  • the cell selection procedure of the RRC connection reestablishment procedure may be performed in the same manner as the cell selection procedure performed by the UE in the RRC idle state, although the UE maintains the RRC connection state.
  • the UE After performing the cell selection procedure, the UE checks the system information of the corresponding cell to determine whether the corresponding cell is a suitable cell (S1630). If it is determined that the selected cell is an appropriate E-UTRAN cell, the terminal transmits an RRC connection reestablishment request message to the cell (S1640).
  • the RRC connection re-establishment procedure is stopped, the terminal is in the RRC idle state Enter (S1650).
  • the terminal may be implemented to complete the confirmation of the appropriateness of the cell within a limited time through the cell selection procedure and the reception of system information of the selected cell.
  • the terminal may run a timer as the RRC connection reestablishment procedure is initiated.
  • the timer may be stopped when it is determined that the terminal has selected a suitable cell. If the timer expires, the UE may consider that the RRC connection reestablishment procedure has failed and may enter the RRC idle state.
  • This timer is referred to hereinafter as a radio link failure timer.
  • a timer named T311 may be used as a radio link failure timer.
  • the terminal may obtain the setting value of this timer from the system information of the serving cell.
  • the cell When the RRC connection reestablishment request message is received from the terminal and the request is accepted, the cell transmits an RRC connection reestablishment message to the terminal.
  • the UE Upon receiving the RRC connection reestablishment message from the cell, the UE reconfigures the PDCP sublayer and the RLC sublayer for SRB1. In addition, it recalculates various key values related to security setting and reconfigures the PDCP sublayer responsible for security with newly calculated security key values.
  • SRB 1 between the UE and the cell is opened and an RRC control message can be exchanged.
  • the terminal completes the resumption of SRB1 and transmits an RRC connection reestablishment complete message indicating that the RRC connection reestablishment procedure is completed to the cell (S1660).
  • the cell transmits an RRC connection reestablishment reject message to the terminal.
  • the cell and the terminal perform the RRC connection reestablishment procedure.
  • the UE recovers the state before performing the RRC connection reestablishment procedure and guarantees the continuity of the service to the maximum.
  • the UE reports this failure event to the network when an RLF occurs or a handover failure occurs in order to support Mobility Robustness Optimization (MRO) of the network.
  • MRO Mobility Robustness Optimization
  • the UE may provide an RLF report to the eNB.
  • Radio measurement included in the RLF report can be used as a potential reason for failure to identify coverage problems. This information can be used to exclude such events from the MRO evaluation of intra-LTE mobility connection failures and to write those events as input to other algorithms.
  • the UE may generate a valid RLF report to the eNB after reconnecting in the idle mode. For this purpose, the UE stores the latest RLF or handover failure related information, and for 48 hours after the RLF report is retrieved by the network or after the RLF or handover failure is detected, the RRC connection ( Re-establishment and handover may indicate to the LTE cell that the RLF report is valid.
  • the UE maintains the information during state transition and RAT change, and indicates that the RLF report is valid again after returning to the LTE RAT.
  • the validity of the RLF report in the RRC connection establishment procedure indicates that the UE has been interrupted such as a connection failure and that the RLF report due to this failure has not yet been delivered to the network.
  • the RLF report from the terminal includes the following information.
  • E-CGI of the target cell of the last cell in case of RRL or handover that provided a service to the terminal. If the E-CGI is unknown, PCI and frequency information is used instead.
  • E-CGI of the cell that serviced the terminal when the last handover initialization for example when message 7 (RRC connection reset) was received by the terminal.
  • the eNB receiving the RLF failure from the terminal may forward the report to the eNB that provided the service to the terminal before the reported connection failure.
  • Radio measurements included in the RLF report can be used to identify coverage issues as a potential cause of radio link failure. This information can be used to exclude these events from the MRO assessment of intra-LTE mobility connection failures and send them back as input to other algorithms.
  • RRM radio resource management
  • the terminal may perform measurement for a specific purpose set by the network and report the measurement result to the network in order to provide information that may help the operator operate the network in addition to the purpose of mobility support. For example, the terminal receives broadcast information of a specific cell determined by the network.
  • the terminal may include a cell identity (also referred to as a global cell identifier) of the specific cell, location identification information (eg, tracking area code) to which the specific cell belongs, and / or other cell information (eg, For example, whether a member of a closed subscriber group (CSG) cell is a member) may be reported to the serving cell.
  • a cell identity also referred to as a global cell identifier
  • location identification information eg, tracking area code
  • other cell information eg, For example, whether a member of a closed subscriber group (CSG) cell is a member
  • the mobile station may report location information and measurement results of poor quality cells to the network.
  • the network can optimize the network based on the report of the measurement results of the terminals helping the network operation.
  • the terminal should be able to measure the quality and cell information of neighboring cells having the same center frequency as the center frequency of the serving cell.
  • the measurement of the cell having the same center frequency as that of the serving cell is called intra-frequency measurement.
  • the terminal performs the intra-frequency measurement and reports the measurement result to the network at an appropriate time, so that the purpose of the corresponding measurement result is achieved.
  • the mobile operator may operate the network using a plurality of frequency bands.
  • the terminal may measure quality and cell information of neighboring cells having a center frequency different from that of the serving cell. Should be As such, a measurement for a cell having a center frequency different from that of the serving cell is called inter-frequency measurement.
  • the terminal should be able to report the measurement results to the network at an appropriate time by performing inter-frequency measurements.
  • the terminal When the terminal supports the measurement for the network based on the other RAT, it may be measured for the cell of the network by the base station configuration. This measurement is called inter-radio access technology (inter-RAT) measurement.
  • the RAT may include a UMTS Terrestrial Radio Access Network (UTRAN) and a GSM EDGE Radio Access Network (GERAN) conforming to the 3GPP standard, and may also include a CDMA 2000 system conforming to the 3GPP2 standard.
  • UTRAN UMTS Terrestrial Radio Access Network
  • GERAN GSM EDGE Radio Access Network
  • 17 is a flowchart illustrating an example of a measurement performing method to which the present invention can be applied.
  • the terminal receives measurement configuration information from the base station (S1710).
  • a message including measurement setting information is called a measurement setting message.
  • the terminal performs the measurement based on the measurement setting information (S1720). If the measurement result satisfies the reporting condition in the measurement configuration information, the terminal reports the measurement result to the base station (S1730).
  • a message containing a measurement result is called a measurement report message.
  • the measurement setting information may include the following information.
  • the measurement object includes at least one of an intra-frequency measurement object that is an object for intra-cell measurement, an inter-frequency measurement object that is an object for inter-cell measurement, and an inter-RAT measurement object that is an object for inter-RAT measurement.
  • the intra-frequency measurement object indicates a neighboring cell having the same frequency band as the serving cell
  • the inter-frequency measurement object indicates a neighboring cell having a different frequency band from the serving cell
  • the inter-RAT measurement object is
  • the RAT of the serving cell may indicate a neighboring cell of another RAT.
  • the report setting information may consist of a list of report settings.
  • Each reporting setup may include a reporting criterion and a reporting format.
  • the reporting criterion is a criterion that triggers the terminal to transmit the measurement result.
  • the reporting criteria may be a single event for the measurement reporting period or the measurement report.
  • the report format is information on what type the terminal configures the measurement result.
  • Measurement identity information This is information about a measurement identifier that associates a measurement object with a report configuration, and allows the terminal to determine what type and when to report to which measurement object.
  • the measurement identifier information may be included in the measurement report message to indicate which measurement object the measurement result is and in which reporting condition the measurement report occurs.
  • Quantitative configuration information information on a parameter for setting filtering of a measurement unit, a reporting unit, and / or a measurement result value.
  • Measurement gap information Information about a measurement gap, which is a section in which a UE can only use measurement without considering data transmission with a serving cell because downlink transmission or uplink transmission is not scheduled. .
  • the terminal has a measurement target list, a measurement report configuration list, and a measurement identifier list to perform a measurement procedure.
  • the base station may set only one measurement target for one frequency band to the terminal.
  • E-UTRA Evolved Universal Terrestrial Radio Access
  • RRC Radio Resource Control
  • Protocol specification Release 8
  • the terminal If the measurement result of the terminal satisfies the set event, the terminal transmits a measurement report message to the base station.
  • Reliable communication means a new communication service realized through error free transmission or service availability for realizing mission critical service (MCS).
  • MCS mission critical service
  • Reliable communication is machine-to-measure that meets real-time requirements for traffic safety, traffic efficiency, e-health, efficient industrial communication, and more. As part of the communication, the need is recognized.
  • reliable communications must provide reliable connections for delay-sensitive applications such as traffic safety or for mission-critical machine-type communications (MTCs). do.
  • MTCs mission-critical machine-type communications
  • Reliable communication is also recognized for the purposes of medical / emergency response, remote control, sensing, and the like.
  • MCSs are expected to require enormous improvements in terms of end-to-end latency, ubiquity, security, availability and reliability compared to conventional UMTS / LTE and LTE-A / Wi-Fi.
  • a metric called reliability may be 'an evaluation criterion for describing the quality of a radio link connection to satisfy a specific service level'.
  • RLA Radio Link Availability
  • RLQ is the measured radio link quality and QoE are the QoE requirements in terms of link quality.
  • examples of applicable scenarios of the 5G mobile communication environment for MCSs include the following services.
  • AGV automated guided vehicles
  • Safe signals can be exchanged between vehicles to provide autonomous driving services, or safety signals that indicate hidden vehicles or forward collisions that are not captured by the vehicle's sensors (cameras, radars, etc.). Safe delivery
  • the above-mentioned services can quickly determine another available alternative base station link according to the deterioration of the radio link (serving link) quality of the serving base station, so that if the radio link quality of the serving base station is not suitable for MCS, the terminal may substitute the corresponding substitute base station.
  • the terminal may substitute the corresponding substitute base station.
  • the UE utilizes all the radio links around itself and instructs to maximize the quality of the radio link according to the situation, thereby providing wireless link outage for MCS. Should be considered as an essential factor.
  • the terminal controls the RLF based on a plurality of Timers.
  • the UE does not recognize the RLF until the specific Timer (eg, T310) expires, and depending on the success of the RRC Connection Re-establishment procedure before another Timer (eg, T311) expires.
  • the terminal maintains the RRC connection or transitions to the RRC Idle state.
  • Future 5G mobile communications must meet error rates below 10 -6 and RLA requirements below 10 -6 to support MCSs such as industrial automation, drone remote control, autonomous vehicle driving, etc. .
  • 5G aims to build a high-reliability system that can always receive the MCS without the terminal feels the outage of the radio link.
  • the current LTE / LTE-A system is designed to handle the recovery from the RLF considerably conservatively, and thus search for other available link base stations that can be quickly replaced according to the channel conditions of the terminal, and to the alternative link base stations There is a problem in that it is difficult to secure an available alternative link base station for connection switching.
  • a method for setting a multi-connection (or multilink) by a terminal to a plurality of base stations by transmitting an indicator indicating that the terminal is an MCS capable (Capable) terminal when the terminal accesses the network is not limited to, but not limited to, MCS capable (Capable) terminal.
  • Multi-Link refers to a plurality of radio links in which a terminal has a connection with a plurality of base stations.
  • the multilink may include a serving link and at least one replacement link.
  • the serving link indicates a radio link in which the terminal has a connection with a serving base station
  • the alternative link means a radio link in which the terminal has a connection with a base station other than the serving base station.
  • the serving link may be represented by a first radio link and the replacement link by a second radio link.
  • the base station other than the serving base station may be represented as an alternative base station, a candidate (target) base station, a neighbor base station, a target base station, and the like.
  • the serving base station establishes an active RRC connection with the terminal and means the base station to which the terminal is currently receiving service.
  • the alternate serving base station refers to a new serving base station replacing the serving base station when the serving base station deteriorates (or degrades) the radio link quality, which will be described later.
  • the alternate serving base station may be any one of the alternative base stations in which the alternative link in the SRB inactive state is configured.
  • the alternate serving base station may be an alternate base station in which an alternate link in an SRB inactive state transitions to an alternate link in an SRB active state according to a link quality degradation of the serving base station.
  • the additional substitute base station will be described later, and indicates an alternative base station in which the alternative link is additionally found by the terminal except for the preset alternative base station.
  • Link connection means a wireless connection with a base station, and may be expressed as a radio link establishment, a radio link establishment, and the like.
  • multilink connection (or configuration) may be represented as a multi-connection, alternative link connection and the like.
  • FIG. 18 is a diagram illustrating a conceptual diagram of an alternative link to which the methods proposed herein may be applied.
  • the multi-connection or multilink includes a serving link and at least one replacement link.
  • the serving link refers to a radio link between a terminal and a serving base station.
  • the serving link has both a signaling radio bearer (SRB) and a data radio bearer (DRB) active.
  • SRB signaling radio bearer
  • DRB data radio bearer
  • the alternate link represents a radio link between the terminal and the at least one alternative base station. Only the inactive SRB is set, and the DRB is not set.
  • the alternate link is activated only by the activation indication of the serving base station, and is a link concept having a state different from that of a general dormant mode, and may be an event-triggered dormant mode.
  • the alternate link connected to the alternate base station in the SRB inactive state maintains a sleep state on the alternate link until there is an activation instruction by the terminal (or from the serving base station).
  • the terminal may receive in advance from the serving base station information on the number of the maximum alternative link that can be connected to the surrounding alternative base station via a broadcast message such as SIB.
  • the UE may additionally configure an alternative link with an alternative base station that satisfies a specific condition (Q MCS ).
  • the conventional method relates to a method in which the terminal establishes an alternate link with a neighboring base station when the terminal accesses the network.
  • MCS mission critical service
  • the conventional method relates to a method of setting up an alternative base station and an alternative link to support MCS when the terminal accesses the network.
  • the conventional method can be applied to both (1) when there is no need to synchronize between the terminal and the alternative base station and (2) when the synchronization between the terminal and the alternative base station is to be synchronized.
  • the terminal When the terminal has a multilink with a plurality of base stations, the terminal has an active connection (serving link of the active state) with the serving base station, the inactive state (inactive state with the alternative base station) Has an alternative link of).
  • the serving link in the active state means that the terminal configures an active signaling radio bearer (SRB) / active data radio bearer (DRB) with the serving base station, and in the alternative link in the inactive state, the terminal configures only the alternative base station and the inactive SRB. It can mean doing.
  • SRB active signaling radio bearer
  • DRB active data radio bearer
  • the inactive SRB may indicate a state in which the UE does not have an alternative base station and DRB configured.
  • the serving base station sets the S-GW and S1-U Bearer to set the E-RAB, which means that the EPS Bearer is set up along with the S5 / S8 Bearer between the S-GW and the P-GW. .
  • the alternative base station for setting up the alternative link with the terminal configures the S-GW and S1-U Bearer, but the UE and DRB is not set, the E-RAB is not set.
  • the P-GW and the S5 / S8 bearer may be set.
  • the terminal configures at least one alternative base station and inactive SRB with respect to the MCS, but does not configure the DRB.
  • an inactive SRB (or SRB inactive state) has a state different from the normal (LTE / LTE-A system) dormant mode or dormant state.
  • the SRB inactive state may be expressed as an SRB inactive mode or an RRC inactive state.
  • the general dormant mode refers to a mode used for power saving of the RRC connected UE.
  • the terminal when there is no data to be received by the terminal, the terminal enters the dormant mode and periodically sleeps and wakes up, thereby repeatedly reducing unnecessary power consumption of the terminal.
  • the SRB inactive mode (or state) used in the present specification refers to a state in which the user continues to sleep unless there is a separate SRB active indication.
  • the SRB inactive mode may be defined as a state activated by an indication of a terminal or a serving base station.
  • the SRB inactive mode may be represented as an event-triggered dormant mode.
  • the serving base station can be reliably and seamlessly provided by securing a radio link with another base station, that is, an alternative base station that can guarantee better radio link quality.
  • the following four modes may be considered according to the active or inactive states of the SRB and DRB of the alternate link between the UE and the alternative base station.
  • the SRB is inactive state and the EPS Bearer that satisfies QoS for MCS is not set.
  • DRB is not set in the first mode.
  • the fourth mode is a state in which an inactivated RRC connection is activated by a separate activation indicator to exchange RRC messages between the terminal and the base station.
  • an EPS bearer that satisfies the QoS for the MCS may be set, and the DRB is set.
  • the aforementioned conventional method (method of setting up a multilink when accessing a network) and a method of dynamically setting up a multilink when an MCS occurs have many differences in the procedure for setting the multilink and the effects thereof.
  • the terminal when a terminal accesses a network, the terminal is connected to a serving base station and a plurality of alternative base stations, whether (1) it is necessary to synchronize with the alternative base station or (2) it is not necessary to synchronize with the alternative base station. Synchronize and receive a C-RNTI from a plurality of alternative base stations.
  • a method for dynamically setting a multi-connection (or multilink) with a plurality of base stations by network indication and the like needs to be defined.
  • the terminal may use RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), SINR (Signal to Interference Plus Noise Ratio), and the like. have.
  • RSRP Reference Signal Received Power
  • RSRQ Reference Signal Received Quality
  • RSSI Receiveived Signal Strength Indicator
  • SINR Signal to Interference Plus Noise Ratio
  • activating the replacement link of the replacement base station means changing the replacement link in the SRB inactive state to the SRB active state.
  • setting the MCS bearer can be interpreted as setting up a DRB for the MCS between the terminal and the base station.
  • the terminal may receive C-RNTI, Timing Advanced (TA) from the alternative base station through the configuration of the alternative link, but there may occur a situation where the alternative base station and the TA are shifted according to the movement of the terminal.
  • C-RNTI C-RNTI
  • TA Timing Advanced
  • the network transmits a radio link quality threshold newly defined for the MCS to the terminal, so that the terminal replaces the SRB inactive state when the radio link quality of the serving base station is lower than the radio link quality threshold for receiving the MCS. Activate the link with SRB active.
  • the newly defined MCS radio link quality threshold may be used as a trigger condition of alternate link activation.
  • the LTE (-A) system generates different EPS bearers according to the quality of service (QoS).
  • QoS quality of service
  • the LTE (-A) system requests a dedicated bearer to the terminal through the S-GW, the MME, and the base station at the request of the PDN-GW. Set it.
  • UL traffic occurs in the terminal, that is, when a bearer resource modification request is generated by the terminal, a dedicated bearer setup procedure defined in the DL traffic is the same. Can be applied.
  • 19 is a flowchart illustrating an example of a network indication based multilink configuration method.
  • the setting of the multilink is a concept of setting an alternative link in addition to the serving link.
  • the multilink setting may have the same meaning and interpretation or expression as the “alternative link setting”.
  • the expression that the terminal is connected to the alternative base station may be interpreted to mean that the alternative link is established between the terminal and the alternative base station.
  • the serving base station transmits a broadcast message including control information related to a mission critical service (MCS) to the terminal (S1910).
  • MCS mission critical service
  • the broadcast message may be a system information block (SIB), a master information block (MIB), or the like.
  • SIB system information block
  • MIB master information block
  • the control information related to the MCS may include a radio link quality degradation (RLQD) threshold value, maximum number of replacement links indicating the maximum number of replacement links that can be set by the terminal, and the like.
  • RQD radio link quality degradation
  • the RLQD threshold is a minimum value of the radio link quality for receiving the MCS, and refers to a reference value for determining whether the radio link (signal) quality is deteriorated and can no longer be provided with the MCS through the corresponding radio link.
  • the terminal attempts to connect with another radio link.
  • the measurement of the radio link (signal) quality may be performed using Salpin RSRP, RSRQ, RSSI, SINR, and the like.
  • the maximum number of replacement links is information indicating the maximum number of replacement links that the terminal can configure with the replacement base station for a specific service such as an MCS.
  • the terminal measures the radio link quality for each alternative base station based on the list of the alternative base station (or neighbor base station, candidate base station) owned by it, and reports the measurement result to the serving base station (S1920). .
  • the MME transmits an E-RAB setup request message including multi-link setup indication information for MCS to the serving base station (S1930).
  • the MCS bearer setup procedure between the terminal and the base stations (serving base station and alternate base station) is performed (or started).
  • the E-RAB setup request message may include E-RAB QoS parameters related to the MCS in addition to the multi-link setup indication information.
  • the multi-link setup indication information refers to an indicator for indicating multi-link (or alternative link) configuration between the terminal and at least one alternative base station.
  • One of the E-RAB QoS parameters related to the MCS may be a QoS Class Identifier (QCI) of the MCS, and the E-RAB QoS parameters may be included in an E-RAB QoS Parameters Information Element (IE).
  • QCI QoS Class Identifier
  • IE E-RAB QoS Parameters Information Element
  • the serving base station can know what service (which QoS has a service) related to MCS bearer configuration through the received E-RAB QoS Parameter.
  • the serving base station may set a data radio bearer (DRB) for a service having a specific QoS with the terminal.
  • DRB data radio bearer
  • the network entity eg, MME
  • MME Mobility Management Entity
  • the serving base station may instruct to configure a DRB for the terminal and the MCS, and to configure a multilink or an alternate link for the terminal as necessary.
  • the serving base station receiving the E-RAB Setup Request message determines the load state of the alternative base stations for which the terminal periodically reports the measurement result (through step S1920), and has a good load state.
  • An alternative base station having a request may be made to establish an alternative link with the terminal.
  • the alternative base stations held (or identified) by the serving base station may be limited to alternative base stations satisfying a threshold of MCS radio link (signal) quality to be searched (or selected) as an alternative link for MCS. .
  • the threshold of the MCS radio link quality may be a salping RLQD threshold.
  • the terminal selects alternative base stations having a better radio link quality than the RLQD threshold obtained through step S1910, lists them as candidate alternative base stations to establish the alternative link, and transmits them to the serving base station.
  • the serving base station transmits a load query request (Load Query Request) message to the alternative base stations (alternative base stations 1 and 2) to determine the current load status of each alternative base station (S1940).
  • Load Query Request a load query request
  • the alternative base stations (replacement base stations 1 and 2) transmit a Load Query Response message to the serving base station in response to the load query request (S1950).
  • the load query response message includes information on the current load status of the alternative base station.
  • the load state may be expressed as high / medium / low.
  • the serving base station transmits a multi-link connection request message for requesting a multilink connection with the terminal to the alternative base stations (alternative base stations 1 and 2) (S1960).
  • the expression of the multilink connection request message is one example, which may be referred to in various terms such as a multi-connection request message, an alternative link connection request message, an alternative link securing request message.
  • the multilink connection request message may include a terminal identifier (eg, UE ID), terminal context (UE context) information, signaling radio bearer (SRB) deactivate indication information, and the like.
  • UE ID terminal identifier
  • UE context terminal context
  • SRB signaling radio bearer
  • the UE context information refers to context information of UE, which is used to manage a UE in a network, that is, context information including UE ID, mobility (current location, etc.), and session attributes (QoS, priority, etc.).
  • the SRB deactivate indication information indicates an indicator indicating that the SRB state of the alternate link established with the alternative base station is set to inactive (or event-triggered Dormant mode).
  • the serving base station receives a multi-link connection response message from the alternative base stations (alternative base stations 1 and 2) in response to the multi-link connection request message (S1970).
  • the multilink connection response message may also be referred to in other terms as described in the multilink connection request message.
  • the multilink connection response message includes information on an alternative base station.
  • the multilink connection response message may include C-RNTI of the alternative base station, result (success / failure) information on the multilink connection request, TA tracking indication information for acquiring synchronization between the UE and the alternative base station, TA tracking period information, and the like. It may include.
  • the TA tracking indication information and the TA tracking period information correspond to information necessary for acquiring synchronization when the synchronization between the terminal and the alternative base station does not match due to the movement of the terminal.
  • the serving base station transmits information related to multilink connection establishment, that is, from the alternative base stations (alternative base stations 1 and 2) through step S1970 to inform that the alternative link is established with the alternative base stations (alternative base stations 1 and 2).
  • An RRC connection reconfiguration message including the received information is transmitted to the terminal (S1980).
  • the RRC connection reconfiguration message may further include radio bearer quality of service (Radio Bearer QoS), session management request information, EPS RB ID information, etc. to inform that the MCS bearer is configured.
  • Radio Bearer QoS Radio Bearer QoS
  • session management request information e.g., session management request information
  • EPS RB ID information e.g., EPS RB ID information
  • the terminal transmits an RRC Connection Reconfiguration Complete message to inform the serving base station that the multilink connection setup for the alternative base stations (alternative base stations 1 and 2) is completed (S1990).
  • the serving base station continuously maintains a list of alternative base stations and may update the corresponding list as necessary.
  • FIG. 19 illustrates an example of a method for configuring an alternate link between the terminal and the alternative base station by a network (MME) indication when it is not necessary to synchronize the terminal and the alternative base station.
  • MME network
  • 20 is a flowchart illustrating still another example of a network indication based multilink configuration method.
  • steps S2001 to S2008 are the same as steps S1910 to S1980 of FIG. 19, a detailed description thereof will be made with reference to FIG. 19, and only a part different from FIG. 19 will be described in detail with reference to FIG. 20.
  • FIG. 20 relates to a method for configuring an alternative link when the terminal needs to synchronize with an alternative base station, and the terminal is assigned a dedicated random access preamble allocated from each alternative base station through an RRC connection reconfiguration message. Preamble), and C-RNTI is obtained through a random access procedure with each alternative base station.
  • the terminal receives C-RNTI and Timing Advance (TA) information from the alternative base station, but since the TA may deviate from the alternative base stations where the alternative link of the Inactive SRB is set according to the movement of the terminal, the uplink synchronization This is a method for periodically tracking the tracking.
  • TA Timing Advance
  • each alternative base station includes its C-RNTI, indication information indicating periodic TA tacking, and periodic information for TA tracking in a random access response, and transmits it to the terminal.
  • the terminal may transmit uplink synchronization with the alternative base station by periodically transmitting a dedicated random access preamble to the alternative base station according to a TA tracking period indicated by the alternative base station through the random access response.
  • the serving base station transmits an RRC connection reconfiguration message including a dedicated random access preamble allocated from each alternative base station (alternative base stations 1 and 2) to the terminal (S2008). ).
  • the terminal performs an RACH procedure for synchronizing uplink synchronization with each alternative base station (alternative base station 1 and 2) (S2009, S2010).
  • the terminal transmits a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2) through the PRACH (S2009).
  • the terminal receives a random access response including a C-RNTI, periodic TA tracking indication information, and TA tracking period information associated with each alternative base station from each alternative base station (S2010).
  • the terminal transmits an RRC Connection Reconfiguration Complete message indicating that the RRC connection reconfiguration has been completed to the serving base station (S2011).
  • 21 is a flowchart illustrating still another example of a network indication based multilink configuration method.
  • FIG. 21 is another embodiment of FIG. 19.
  • TA tracking information (TA tracking indication information and TA tracking period information) may be included in an RRC connection reconfiguration message and transmitted to the terminal. .
  • the terminal establishes a multilink with the base stations, in particular, sets a serving base station, an active SRB and an active DRB, and sets an alternative base station and an inactive SRB.
  • FIGS. 22 and 23 a method of releasing a multilink (or multiple connectivity) with an alternative base station by referring to FIGS. 22 and 23 will be described in detail.
  • the MME forwards a request to the serving base station or the serving base station provides the request.
  • the replacement link for the MCS between the terminal and the alternative base station is terminated.
  • the method of canceling the multilink may be divided into (1) a method in which the serving base station notifies the terminal (Fig. 22) and (2) a method in which an alternative base station to be canceled is notified directly to the terminal (Fig. 23).
  • 22 is a flowchart illustrating an example of a method of terminating a multilink.
  • FIG. 22 may be classified according to who sends an E-RAB release command or an E-RAB release instruction indicating that the MCS dedicated bearer should be released as follows.
  • MME sends E-RAB Release Command message to serving base station (FIG. 22A)
  • an MCS bearer is set between a terminal and a base station (a serving base station and an alternative base station).
  • the serving base station receives an E-RAB release command message indicating an MCS bearer release from the MME (S2211).
  • the serving base station transmits an E-RAB Release Indication (Release Indication) message to release the MCS Bearer to the MME (S2212).
  • E-RAB Release Indication Release Indication
  • the E-RAB release command message or E-RAB release indication message may include multilink-connection release indication information indicating a multilink connection release indication and E-RAB release list information for MCS. Include.
  • the serving base station transmits a multi-link release request message for the multi-link release request to the alternative base stations (alternative base stations 1 and 2) to release the alternate link (S2220).
  • the multilink release request message includes a UE ID and the like.
  • the serving base station receives a multi-link release response (Multi-Link Release Response) message from the alternative base stations (alternative base station 1 and 2) in response to the multilink release request message (S2230).
  • Multi-Link Release Response Multi-Link Release Response
  • the serving base station transmits a result of the replacement link cancellation with the alternative base stations (replacement base stations 1 and 2) to the terminal through an RRC connection reconfiguration message (S2240).
  • the RRC connection reconfiguration message may include C-RNTI and identifier information of the alternative base stations.
  • the terminal transmits an RRC connection reconfiguration complete message to the serving base station in response to the RRC connection reconfiguration message to the serving base station (S2250).
  • the MCS bearer setup which was established between the terminal and the base stations, is terminated.
  • the terminal maintains the active SRB / DRB set with the serving base station (but the dedicated bearer for MCS is terminated), and the inactive SRB set with the alternative base stations is terminated.
  • 23 is a flowchart illustrating still another example of a method of canceling a multilink.
  • FIG. 23 illustrates a method in which an alternative base station directly notifies a user equipment that a multilink or an alternative link has been terminated unlike FIG. 22.
  • steps S2311 to S2320 are the same as steps S2211 to S2220 of FIG. 22, a detailed description thereof will be described with reference to FIG. 22, and only a part different from FIG. 22 will be described in detail with reference to FIG. 23.
  • the serving base station transmits a multi-link release request message in step S2320 to alternative base stations (alternative base stations 1 and 2) to release the alternate link, and then transmits the message to the terminal.
  • the serving base station transmits an RRC connection reconfiguration message indicating that the bearer for the MCS has been terminated (S2330).
  • the alternative base stations that have received the multi-link release request from the serving base station transmit an RRC connection release message to indicate that the MCS bearer (i.e., the alternative link) has been terminated at the replacement base stations.
  • the terminal S2340.
  • the alternative base stations may inform the serving base station of the result of the alternative link termination between them and the terminal, and the procedure may be selectively applied.
  • the result of the alternate link termination transmitted by the alternative base stations to the serving base station may be performed in response to the multilink termination request, through a multilink termination response message.
  • the terminal may synchronize with the serving base station and the alternative base station whether or not it is necessary to synchronize with the alternative base station, and C- from the alternative base station.
  • Receive and secure RNTI Receive and secure RNTI.
  • the UE activates the alternative link of the optimal alternative base station according to the radio link quality change of the serving base station and / or the alternative base station, and sets up the MCS Bearer faster by receiving a UL Grant through the alternative link of the activated alternative base station. Can be.
  • activation of the alternate link means to change the alternate link of the Salpin SRB inactive state to the SRB active state in FIGS. 19 to 21, which may be triggered by the serving base station or the terminal.
  • 'Q out ' corresponding to a criterion (value) in which the downlink radio link quality cannot be reliably measured.
  • Q out is defined as follows.
  • the threshold Qout is defined as the level at which the downlink radio link cannot be reliably received and shall correspond to 10% block error rate of a hypothetical PDCCH transmission taking into account the PCFICH errors with transmission parameters specified in Table 2.
  • Theshold Q out is defined as the level at which the downlink radio link cannot be reliably received, and with the transmission parameters specified in Table 2, at the 10% block error rate of virtual PDCCH transmission considering PCFICH errors. Applicable
  • Table 2 below shows an example of PDCCH / PCHICH transmission parameters for out-of-sync.
  • RS RE energy 1 dB when two or four antenna ports are used for cell-specific reference signal transmission by the PCell or PSCell.
  • DCI format 1A is defined in clause 5.3.3.1.3 in TS 36.212 [21].
  • Note 2 A hypothetical PCFICH transmission corresponding to the number of control symbols shall be assumed.
  • the reason is that the reliability requirement for providing MCSs, that is, the reliability criterion reaches 99.999%.
  • the threshold Q out defined by a 10% Block Error Rate (BER) criterion cannot satisfy the Reliability requirement for providing MCSs.
  • Q MCS is newly defined as a threshold of reliability requirements (or criteria) for MCS provision.
  • the newly defined Q MCS means a minimum value or a reference value or threshold value of radio link quality capable of supporting the MCS.
  • the Q MCS may be used as a trigger condition for fast MCS bearer setup.
  • the Q MCS may be determined according to a channel code type, a codeword length, a data size, and a modulation and coding scheme (MCS) level.
  • MCS modulation and coding scheme
  • 19 to 21 may inform the UE of the radio link quality threshold Q MCS for the MCS through an RRC connection reconfiguration message informing the UE that the MCS Dedicated Bearer is set.
  • the terminal receives the Q MCS through the front (1) or (2), and the procedure of the downlink radio link (Radio Link) quality in this case falls below a threshold value of Q MCS, FIG. 24 to FIG. 26 to be described later
  • the alternative link of the optimal alternative base station By activating the alternative link of the optimal alternative base station through, and by setting up the alternative base station and the bearer the alternative link is activated, it is possible to provide a reliable and seamless MCS.
  • 24 to 26 illustrate that the quality of the radio link (serving link) (signal) of the serving base station is not suitable for supporting a specific MCS while the terminal accesses the network through the serving base station and sets the EPS bearer for the MCS. If not, it shows a method of activating the alternative link of the optimal alternative base station among the alternative base stations having the alternative link with the UE and the SRB Inactive state, and quickly configures the MCS Bearer through the alternative base station activated the alternative link.
  • the state of setting the EPS bearer for the MCS refers to a state in which the terminal secures the DRB ID of the radio section and the EPS bearer ID of the network section.
  • the fact that the radio link (signal) quality of the serving base station is degraded to be unsuitable for a particular MCS indicates that the radio link quality of the serving base station has fallen below the Q MCS threshold.
  • 24 is a flowchart illustrating an example of a method of configuring an alternate link activation and an MCS bearer of an alternative base station according to a deterioration of radio link quality of a serving base station.
  • 24 is a method that may be applied when it is not necessary to synchronize synchronization between a terminal and an alternative base station.
  • the case where it is not necessary to synchronize the terminal and the alternative base station may be a small cell environment or an environment in which a new waveform-based asynchronous system is built.
  • the serving base station represents a method for determining or selecting an alternative serving base station from among the alternative base stations to replace itself.
  • a terminal establishes a multilink connection with a serving base station and an alternative base station through the method of FIGS. 19 to 21. That is, it is assumed that the alternative link in the SRB inactive state is established between the terminal and the alternative base station.
  • the terminal periodically measures the DL signal quality for the serving base station and the alternative base station (S2401).
  • the DL signal quality measurement period of the terminal may be possible by specifying DL signal quality measurement period information in an RRC connection reconfiguration message transmitted from the serving base station to the terminal when establishing an alternative link with the alternative base station.
  • the terminal notifies the serving base station when the radio link signal quality of the serving base station falls below a defined threshold (Q MCS ), that is, lower than the Q MCS value (S2402). That is, it triggers multilink activation.
  • Q MCS a defined threshold
  • the terminal determines whether the radio link quality of the serving base station is sufficient to provide the MCS based on a threshold value of the MCS-related radio link quality obtained through an RRC connection reconfiguration message.
  • the terminal transmits radio link quality deterioration (RLQD) indication information to the serving base station (S2402).
  • RQD radio link quality deterioration
  • the terminal when the terminal additionally discovers or identifies alternative base stations having a better signal quality than the radio link signal quality of the serving base station, the serving base station together with RLQD Indication information, the information on the found additional alternative base stations To send.
  • the serving base station has information such as DRB ID, E-RAB ID, E-RAB QoS Parameter, EPS Bearer ID, S-GW TEID, etc. for the UE.
  • the serving base station has a list of alternative base stations in which an alternative link is set in an SRB inactive state with the terminal, and another alternative base station further identified by the terminal (not configured in an alternative link in an SRB inactive state).
  • the another alternative base station means an alternative base station in which an alternative link is additionally established with the terminal, and will be referred to hereinafter as an additional alternative base station.
  • the serving base station selects all of the alternative base stations (candidate base stations 1 and 2) which are present in the list (or list) of the base stations owned by the terminal in order to select an optimal alternative base station among the alternative base stations in which the alternative link is established. , 3) transmits a link activation request (Link Activation Request) message requesting the replacement link activation (S2403).
  • Link Activation Request Link Activation Request
  • the link activation request message may include terminal identifier information (UE ID) and load query request indication information for requesting a load status of an alternative base station.
  • UE ID terminal identifier information
  • load query request indication information for requesting a load status of an alternative base station.
  • the serving base station receives a link activation response message in response to the link activation request message from corresponding alternative base stations (candidate base stations 1, 2, and 3) (S2404).
  • the link activation response message may include a UE ID, information indicating a load state of an alternative base station.
  • the load state may be expressed as high / medium / low.
  • the serving base station determines or selects an optimal alternative base station (alternative base station 2) to replace the serving base station based on the received link activation response message.
  • the serving base station transmits a link activation confirmation message including information necessary for activation of an alternate link connection with the terminal and quick bearer setup to the determined alternative base station (alternative base station 2) (S2405).
  • alternative base station 2 alternative base station 2
  • the serving base station is a terminal identifier (UE ID), an indicator indicating the SRB activation with the terminal, the E-RAB parameter for the terminal, UE Capability, S-GW TEID, the terminal in the SRB Inactive state the alternate link
  • UE ID terminal identifier
  • E-RAB parameter for the terminal UE Capability
  • S-GW TEID the terminal in the SRB Inactive state the alternate link
  • the information on the list of the alternative link base stations configured and the list of additional alternative base stations (not connected to the SRB Inactive state) additionally reported by the terminal is included in the link activation confirmation message, and the UE is included in the link activation confirmation message.
  • alternative base station eg, alternative base station 2
  • alternative base station for the SRB connection activation target with the terminal will be simply referred to as "alternative serving base station”.
  • the serving base station stops transmitting DL data to the terminal and forwards the DL data of the terminal to an alternative serving base station (candidate base station 2).
  • the alternative serving base station (candidate base station 2) that has received the link activation confirmation message (candidate base station 2) may indicate (Serving eNB Switch Indication) information indicating a change in the serving base station and the alternative serving base station for the terminal.
  • an RRC connection activation message including radio resource setting related information is transmitted to the terminal.
  • the radio resource configuration related information may include information on radio resource configuration including a DRB ID.
  • the terminal transmits an RRC Connection Activation Complete message to an alternative serving base station (alternative base station 2) that will serve as a new serving base station (S2407).
  • alternative base station 2 alternative serving base station 2
  • the terminal transmits UL data to the alternative serving base station and stops transmitting UL data to the previous serving base station.
  • the alternative serving base station (alternative base station 2) transmits a link activation complete (Link Activation Complete) message indicating that SRB activation and bearer setup with the terminal are completed (S2408).
  • Link Activation Complete link activation complete
  • the link activation complete message may include a terminal identifier (UE ID).
  • UE ID terminal identifier
  • the serving base station After receiving the Link Activation Complete message, the serving base station deletes the context of the terminal and transmits a status number (SN) status transfer to an alternative serving base station in which an SRB with the terminal is activated (S2409).
  • SN status number
  • the SN Status Transfer includes status number (SN) information on DL data received until the serving base station transmits a link activation confirmation message to the alternate serving base station, and link activation completed from the alternate serving base station. It may include SN information about UL data received from the terminal until the Activation Complete) message is received.
  • SN status number
  • the alternate serving base station is an additional link of an additional SRB inactive state for the terminal to the additional alternative base station (alternative base station 3) through the information on the additional alternative base station (alternative base station 3) of the terminal received from the serving base station.
  • the multi-link connection request message for requesting the setting is transmitted (S2410).
  • the substitute serving base station receives a multi-link connection response message from the additional alternative base station (alternative base station 3) in response to the multilink connection request message (S2411).
  • the multilink connection response message transmitted from the additional alternative base station includes the C-RNTI allocated to the terminal by the additional alternative base station.
  • the alternative serving base station transmits the C-RNTI received from the additional alternative base station in which an alternative link of an SRB inactive state is additionally established through an RRC connection reconfiguration message (S2412).
  • FIG. 25 is a flowchart illustrating still another example of a method for activating an alternate link and setting up an MCS bearer according to a degradation of a radio link quality of a serving base station.
  • FIG. 25 relates to a method that may be applied when it is necessary to synchronize between a terminal and an additional alternative base station.
  • the additional alternative base station refers to an alternative base station additionally found by the terminal other than the alternative base stations for which the alternative link is already set up through FIGS. 19 to 21.
  • alternative base station 3 represents a further alternative base station.
  • the additional alternative base station means an alternative base station that satisfies the Q MCS additionally identified by the terminal (the alternative link of the SRB inactive state is not set yet).
  • FIG. 25 also, when the terminal detects a deterioration in the radio link signal quality of the MCS with the serving base station, the terminal notifies the serving base station, and the serving base station determines or selects an alternative serving base station to replace itself. The method is shown.
  • steps S2501 to S2511 are the same as steps S2401 to S2411 of FIG. 24, a detailed description thereof will be made with reference to FIG. 24. In FIG. 25, only parts that differ from FIG. 24 will be described in detail.
  • the alternative serving base station requests the additional alternative base station to establish an additional SRB inactive state for the additional link through the information on the additional alternative base station for the terminal received from the serving base station, and receives a response thereto.
  • the multi-link connection response message transmitted from the additional alternative base station includes a dedicated random access preamble allocated by the additional alternative base station to the terminal.
  • the alternative serving base station (alternative base station 2) transmits an RRC connection reconfiguration message to the terminal (S2512).
  • the RRC connection reconfiguration message includes a dedicated random access preamble allocated by the additional replacement base station (alternative base station 3) to the terminal.
  • the alternate serving base station delivers a dedicated random access preamble received from the additional alternate base station in which an alternative link of SRB Inactive state is additionally set through the RRC connection reconfiguration message to the terminal.
  • the terminal transmits the received Dedicated Random Access Preamble to the additional alternative base station (alternative base station 3) through the PRACH (S2513).
  • the terminal is allocated a C-RNTI of the additional alternative base station through a random access response as a response of the dedicated random access preamble from the additional alternative base station (S2514).
  • FIG. 26 is a flowchart illustrating still another example of a method of activating an alternate link and configuring an MSC bearer according to a deterioration of radio link quality of a serving base station.
  • FIG. 26 is an example of a method that may be applied when synchronization between a terminal and an additional alternative base station is to be synchronized as shown in FIG. 25.
  • FIG. 26 may be equally applied to cases where synchronization is not necessary, that is, FIG. 24.
  • FIG. 26 transmits a link activation complete message to the serving base station immediately after the alternative serving base station (alternative base station 2) to be converted to the serving base station receives the link activation confirmation message from the serving base station.
  • steps S2601 to S2605 are the same as steps S2501 to S2505 of FIG. 25, the detailed description will be described with reference to FIG. 25, and FIG. 26 will only be described in detail with reference to FIG. 26.
  • the serving base station does not stop transmitting DL data even after transmitting a link activation confirmation message to the alternative serving base station (alternative base station 2) (S2605).
  • the serving base station transmits the link activation confirmation message to the alternative serving base station, receives a link activation complete message from the alternative serving base station, and transmits an RRC connection activation message to the terminal.
  • the DL data of the UE, which is buffered, is forwarded to the alternative serving BS.
  • the terminal since the terminal has not received any indication related to the switching of the serving base station from the serving base station, the terminal continuously transmits UL data to the serving base station.
  • the alternative serving base station receiving the link activation confirmation message may include a link activation complete message including a terminal identifier and radio resource setting information of the alternative base station for the terminal. Transmits to the serving base station (S2606).
  • the Link Activation Complete message includes information on a radio resource configuration including a DRB ID and the like.
  • the part where FIG. 26 differs from FIGS. 24 and 25 is that the alternate serving base station transmits the link activation complete message to the serving base station immediately after receiving the link activation confirmation message from the serving base station.
  • the serving base station receiving the link activation complete message includes an identifier (ID) of a new serving base station (alternative base station 2) and an indicator indicating (or specifying) a switch of the serving base station.
  • ID an identifier
  • alternative base station 2 an indicator indicating (or specifying) a switch of the serving base station.
  • An RRC Connection Activation message is transmitted to the terminal.
  • the serving base station forwards the UL data of the terminal and the DL data of the terminal, which are simultaneously buffered with the RRC connection activation message, to an alternative serving base station (candidate base station 2) (S2607).
  • the terminal terminates the connection with the serving base station and transmits an RRC Connection Activation Complete message to the alternative serving base station (candidate base station 2) (S2608).
  • the RRC Connection Activation Complete message is an SN for UL and DL data transmitted / received between the serving base station and the terminal until the terminal receives an RRC Connection Activation message from the serving base station.
  • (Status Number) Contains Status information.
  • the terminal transmits UL data to the alternative serving base station.
  • the alternative serving base station requests multi-link establishment of an additional SRB inactive state for the terminal to the additional alternative base station through the information on the additional alternative base station for the terminal received from the serving base station in step S2605.
  • a multi-link connection request message is transmitted (S2609), and a multi-link connection response message is received from the additional alternative base station in response (S2610).
  • the alternative serving base station performs steps S2510 and S2511 of FIG. 25 with the additional alternative base station.
  • the multilink connection response message includes a dedicated random access preamble allocated to the terminal by the additional alternative base station (alternative base station 3).
  • the alternative serving base station transmits a dedicated random access preamble received from alternative base stations (additional alternative base stations) in which an additional link of SRB Inactive state is additionally set through an RRC connection reconfiguration message (S2611).
  • the terminal transmits the received Dedicated Random Access Preamble to the additional alternative base station through the PRACH (S2612), and receives the C-RNTI through the Random Access Response in response thereto (S2613).
  • the content of the method of FIG. 26 differs from the method of FIGS. 24 and 25 can be summarized as follows.
  • the serving base station even after the serving base station receives a link activation complete message from the alternative serving base station, the serving base station sends DL data to the terminal, thereby transmitting DL data of the terminal. You can remove the interrupted section.
  • the serving base station can reduce the period in which DL data transmission is stopped by stopping the DL data transmission while transmitting an RRC Connection Activation message to the terminal.
  • the terminal only receives a terminal for receiving a RRC Connection Activation message from the serving base station until transmitting an RRC Connection Activation Complete message to an alternative serving base station. Since the UL data transmission is interrupted, it is possible to reduce the period in which the UL data transmission of the terminal is stopped.
  • Integrity protection prevents user data and signaling from being altered in an unauthorized manner
  • encryption provides confidentiality of the user data and signaling.
  • AS security protects RRC signaling and user data between UE and E-UTRAN. This provides encryption protection and integrity of RRC signaling on the control plane of the radio protocol. AS security also provides for encryption of user data on the user plane of the wireless protocol. In RRC, the security mode command procedure is used to activate AS security between the UE and the E-UTRAN.
  • NAS security protects NAS signaling between the terminal and the MME. This provides integrity protection and encryption of NAS signaling.
  • the security mode command procedure in the NAS is used to activate NAS security between the terminal and the MME.
  • K ASME secret key
  • the K ASME is derived from a permanent key stored in both the universal subscriber identity module (USIM) and the home subscriber server (HSS). MME receives K ASME from HSS.
  • the terminal induces K ASME using the result of the AKA (authentication and key agreement) procedure in the NAS protocol.
  • AKA authentication and key agreement
  • the terminal and the network perform mutual authentication and agreement with respect to the K ASME .
  • Terminal and the MME derives a K for K NASenc NASint, security of the NAS message, for integrity protection of the NAS message using the K ASME.
  • the UE and the eNB derive the K eNB from the K ASME to protect the signaling and user data on the Uu interface between each other.
  • K eNB from the UE and the eNB derives a K UPenc for encrypting K RRCenc, user data for the K RRCint, encryption of the RRC message for integrity protection of RRC messages.
  • K eNB a new K eNB used in the target cell.
  • K RRCint a new K eNB used in the target cell.
  • K RRCenc a new K eNB used in the target cell.
  • K UPenc a new K eNB used in the target cell.
  • K eNB * is derived based on the current K eNB or new NH (next hop) of the UE and eNB. In addition, the physical cell ID and the downlink carrier frequency of the target cell are used for derivation of K eNB *.
  • NH is derived from KASME at the terminal and MME.
  • the eNB receives the NH from the MME to derive K eNB * for handover.
  • the intra cell handover procedure may be used to change the AS key during RRC_CONNECTED.
  • AS security activation is initiated by the eNB.
  • the MME provides the eNB with information about the integrity protection and encryption algorithms supported by the K eNB , the UE directly derived from the K ASME for AS key derivation. Therefore, after receiving the K eNB and the algorithm from the MME, the eNB may initialize the AS security activation of the terminal.
  • the eNB transmits a SecurityModeCommand message (S2810).
  • the SecurityModeCommand message indicates the integrity protection algorithm and the encryption algorithm to the RRC layer of the terminal after the RRC connection establishment procedure is completed.
  • the RRC layer of the terminal receives the SecurityModeCommand message to apply integrity protection before configuring the PDCP layer of the terminal. Therefore, upon receiving the SecurityModeCommand message, the RRC layer of the terminal decodes the SecurityModeCommand message and derives K RRCint with an algorithm indicated by the received SecurityModeCommand message to protect the integrity of the RRC message ( S2820 ). The RRC layer of the terminal requests the PDCP layer of the terminal to check the integrity of the received SecurityModeCommand message using an algorithm and KRRCint (S2830).
  • the PDCP layer of the terminal checks the integrity of the SecurityModeCommand message (S2840).
  • the PDCP layer of the terminal transmits the result of the integrity check (S2850). If the terminal fails to check the integrity of the SecurityModeCommand message, the terminal transmits a SecurityModeFailure message to the eNB in response to the SecurityModeCommand message. In this case, since no valid algorithm is available at the terminal, neither integrity protection nor encryption apply to the SecurityModeFailure message.
  • the RRC layer of the terminal further derives K RRCenc and K UPenc .
  • the RRC layer of the terminal configures the PDCP layer of the terminal to apply integrity protection using an integrity protection algorithm and K RRCint .
  • the RRC layer of the terminal configures the PDCP layer of the terminal to apply encryption using an encryption algorithm, K RRCenc and K UPenc (S2860).
  • the terminal considers that the AS security is activated, and applies both integrity protection and encryption to all RRC messages after being received or transmitted by the terminal (S2870).
  • the RRC layer of the terminal transmits a SecurityModeComplete message to the eNB in response to the SecurityModeCommand message (S2880).
  • the SecurityModeComplete message is integrity protected but not encrypted.
  • the reason for not applying encryption to the SecurityModeComplete message is that the eNB responds without decryption, whether or not security activation was successfully performed on the UE by sending two response messages (that is, an unencrypted SecurityModeFailure message and an unencrypted SecurityModeComplete message). This is because the message can be easily decoded.
  • the eNB After AS security is activated, the eNB establishes SRB2 and DRB. The eNB does not establish SRB2 and DRB prior to AS security activation. Once AS security is enabled, all RRC messages through SRB1 and SRB2 are integrity protected and encrypted.
  • All user data is then encrypted by the PDCP layer through the DRB.
  • encryption as well as integrity protection do not apply to SRB0.
  • the integrity protection algorithm is common to signaling radio bearers SRB1 and SRB2, and the encryption algorithm is common to all radio bearers (ie SRB1, SRB2 and DRB).
  • Integrity protection and encryption algorithms can only be changed at handover.
  • the present specification provides a method for establishing an S1 signaling connection between the alternative base station (s) and the MME, and setting up an S1 bearer between the alternative base station (s) and the S-GW.
  • the present specification provides a method for generating a security key for multiple connectivity and delivering it to each alternative base station so that the DRBs of alternative base stations configured by the S1 Bearer can be set up at all times in order to maximize the availability of a radio link when establishing the multiple connection. .
  • the present disclosure provides a method for supporting a method in which a terminal secures a plurality of alternative base station links, so that the terminal may have alternative base stations that can quickly replace the channel condition of the serving base station link.
  • 29 is a flowchart illustrating an example of a procedure for establishing an S1-C and S1-U connection with alternative base stations proposed herein.
  • FIG. 29 illustrates an example of a method for establishing a multi-connection with alternative base stations by the serving base station after determining the serving base station and the alternative base stations according to the load state of the alternative base stations without obtaining the UE context information.
  • FIG. 29 illustrates that in a procedure in which the MCS Capable UE establishes a multi-connection with a plurality of alternative base stations upon initial access to a (temporary) serving base station, the alternative base stations establish an S1-C signaling connection with the MME and the alternative base stations are S -An example of a method for setting GW and S1-U Bearer is shown.
  • the temporary serving base station is a serving base station of a terminal.
  • the terminal transmits an RRC connection request message to the temporary serving base station (S2901).
  • the UE informs that the UE is an MCS Capable UE by transmitting an RRC connection request message, and transmits information on candidate target base stations (or candidate replacement base stations) to the temporary serving base station.
  • the terminal delivers an indicator indicating that the connection is a connection for the MCS in the RRC connection request message to the base station.
  • the temporary serving base station inquires about a load state of candidate alternative base stations (that is, candidate alternative base stations included in an RRC connection request message) detected by the terminal (S2902), and transmits the query from each candidate alternative base station. Respond to the response (S2903).
  • candidate alternative base stations that is, candidate alternative base stations included in an RRC connection request message
  • the temporary serving base station determines an alternative base station to establish a multi-connection with the serving base station according to the load state included in the response.
  • the temporary serving base station delivers a serving base station identifier and a C-RNTI assigned by the serving base station to the terminal.
  • the serving base station identifier and the C-RNTI allocated by the serving base station may be included in an RRC connection setup message (S2904).
  • the terminal transmits an RRC Connection Setup Complete message to the serving base station (S2905).
  • the temporary serving base station is a serving base station.
  • the RRC Connection Setup Complete message includes an Attach Request including information such as IMSI and UE Network Capability.
  • the Attach Request is an IMSI or old GUTI, Old GUTI type, last visited TAI (if available), UE Core Network Capability, UE Specific DRX parameters, extended idle mode DRX parameters, Attach Type, ESM message container (Request Type, PDN Type, Protocol Configuration Options, Ciphered Options Transfer Flag), KSIASME, NAS sequence number, NAS-MAC, additional GUTI, P-TMSI signature, Voice domain preference and UE's usage setting, and MS Network Capability.
  • the Attach Request may mean information related to a NAS procedure.
  • the serving base station transmits an initial UE message to the MME (S2905).
  • the initial UE message includes the Attach Request, an eNB UE S1AP ID for S1 Signaling connection establishment, and an indicator indicating that the UE to be registered in the network is an MCS Capable UE (the UE is an MCS capable terminal).
  • the MME allocates an MME UE S1AP ID to the UE, thereby establishing an S1 signaling connection between the eNB and the MME.
  • the S1 signaling connection is defined by a pair (eNB UE S1AP ID, MME UE S1AP ID) allocated by the eNB and the MME to identify a specific UE.
  • the MME performs a procedure for setting an EPS session and a default EPS bearer for the terminal.
  • the MME determines resources necessary for generating an E-RAB and information necessary for NAS signaling, and transfers them to the serving base station (or transmits them) (S2906).
  • step S2906 is a response to the Attach Request, the MME transmits an Attach Accept (Attach Accept) to the terminal.
  • the attach permission includes a QoS parameter received from a GUTI, a TAI list, an EPS bearer ID, a UE-AMBR, and an S-GW.
  • the attach accept is transmitted through an initial context setup request message in a base station and an MME section, and is transmitted in an RRC connection reconfiguration message in a base station and a UE section.
  • the MME may configure the E-RAB ID, the E-RAB QoS, the KeNB, the UE Security Capability, etc., so that the serving base station may configure the S-GW and the S1-U bearer, and the serving base station may configure the UE and the DRB.
  • the initial context setup request message is transmitted to the serving base station (S2906).
  • the serving base station suspends the transmission of the RRC Connection Reconfiguration message to the terminal until the multi-connection configuration is completed.
  • the serving base station receives an Initial Context Setup Request message from the MME to secure a UE context, and then performs a procedure of establishing a multi-connection with alternative base stations through the secured UE context (S2907).
  • the terminal may transmit the identifier information for the alternative base stations to the serving base station through the RRC connection request message, the serving base station to the alternative base stations through this
  • An indicator indicating which base station is a serving base station and which base station is an alternative base station may be included in a multi-connection (or multilink) request message and transmitted.
  • the indicator may be expressed as Serving / Candidate Target eNB ID and Serving / Candidate Target Indication.
  • the serving base station delivers the result of the multi-connection setup to the terminal through an RRC connection reconfiguration message (S2908).
  • the RRC connection reconfiguration message includes identifiers of alternative base stations configured for multiple connectivity and C-RNTIs allocated by the corresponding alternative base stations.
  • the serving base station generates a DRB while transmitting to the terminal the Attach Accept included in the Initial Context Setup Request message received from the MME through an RRC Connection Reconfiguration message.
  • the serving base station transmits an Initial Context Setup Response message including a DRB generation result to the MME (S2909), thereby completing the S1 bearer setup between the base station and the S-GW so that the E-RAB is configured.
  • the terminal delivers an Attach Complete.
  • the Attach Complete is transmitted through an UL Information Transfer message between the UE and the base station (S2910), and is transmitted through an UPLINK NAS Transport message between the base station and the MME (S2911).
  • the UL Information Transfer message includes an identifier list for alternative base stations configured to be connected to an RRC Inactive (or SRB inactive) state.
  • the RRC inactive state refers to the salping SRB inactive state.
  • the Attach Complete is included in the UPLINK NAS TRANSORT by the serving base station and delivered to the MME.
  • the MME receiving the Attach Complete generates individual K eNBs for alternative base stations (S2912).
  • the K eNB is a combination of a K ASME generated as a result of successful authentication of the UE by the MME and a multiple connectivity counter to alternative base stations maintained by the MME for each user requesting multiple connectivity. Is generated.
  • the multi-connection counter is used to ensure freshness of the K eNB delivered to the alternative base stations, and can be operated in various ways.
  • each time the UE attempts multiple connectivity to the alternative base stations for each terminal a different value may be applied to each alternative base station to generate a K eNB (in this case, a large size counter is required), or the terminal may be
  • the MME may operate a separate counter to generate a K eNB by applying a different value every time it attempts multiple connectivity for the alternative base stations (in this case, a small size Counter is required).
  • a UE may generate K eNBs for alternate base stations by applying A: 1, B: 2, and C: 3. Can be.
  • A: 4 and B: 5 may be applied.
  • the UE As a counter applied by the alternative base stations A, B, and C requesting multiple connectivity, the UE generates A K eNB by applying A: 1, B: 1, C: 1.
  • A: 2 and B: 2 may be applied.
  • the MME receives a list of identifiers for the alternative base stations connected to the Attach Complete and RRC Inactive state from the UE, the MME generates a KeNB for each alternative base station, and sets the generated KeNB along with the E-RAB configuration to the corresponding UE.
  • the Multi-Connection Context Setup Request is transmitted (S2913), and in response thereto, the Multi-Connection Context Setup Response is received (S2914).
  • the Multi-Connection Context Setup Request may include an E-RAB ID to be set for each alternative base station, E-RAB QoS information, and an alternate E-RAB indication indicating that the E-RAB is configured through the alternative base station. have.
  • the MME includes the MME UE S1AP ID for S1 signaling connection establishment in the Multi-Connection Context Setup Request and delivers them to the alternative base stations, and the alternative base stations receive the Multi-Connection Context Setup Request from the MME and receive an eNB for the corresponding UE.
  • S1 signaling connection is established between itself and the MME.
  • FIG. 29 illustrates a case in which a base station (temporary serving base station) temporarily connected to a terminal becomes a serving base station, and similarly to a case in which a base station to which a terminal is initially connected does not become a serving base station, a base station to serve as a serving base station is first selected. After the determination, the identifier of the serving base station and the C-RNTI are transmitted to the terminal, and the RRC Connection Setup Complete message including the Attach Request is transmitted to the serving base station.
  • FIG. 29 illustrates an example in which it is not necessary to synchronize the terminal and the alternative base stations.
  • the UE transmits an alternative base station through an RRC Connection Reconfiguration message.
  • Dedicated Preamble (instead of C-RNTI) is received from each other, and through this, a random access procedure is performed with each alternative base station.
  • the terminal acquires the C-RNTI from each alternative base station through random access response with the alternative base stations.
  • FIG. 30 is a flowchart illustrating still another example of a procedure for establishing S1-C and S1-U connection with alternative base stations proposed herein.
  • FIG. 30A illustrates an example of a method of first establishing a multi-connection with alternative base stations and acquiring UE context information by the serving base station.
  • the terminal transmits the RRC Connection Request message to the temporary serving base station and immediately requests the multi-connection configuration to candidate alternative base stations.
  • 30A also shows a case where the provisional serving base station becomes a serving base station.
  • the temporary serving base station Since the temporary serving base station is before performing the NAS procedure, it may be in a state that does not have a UE context received from the MME.
  • the UE context is not included in the multi-connection connection setup.
  • the UE After the multi-connection setup is completed, if the result is transmitted to the UE, the UE performs an NAS procedure while transmitting an RRC Connection Setup Complete message to the serving base station.
  • the serving base station may obtain the UE context from the MME through the NAS procedure.
  • the alternative base stations may receive the UE context through a procedure of obtaining a security key for multiple connectivity.
  • 30B is a flowchart illustrating still another example of a procedure for establishing an S1-C and S1-U connection with alternative base stations proposed herein.
  • FIG. 30B is different from FIG. 30A, after the serving base station includes an Attach Request message included in an RRC connection request received from the UE, the UE transmits the message to the MME after initializing the Attach Request message, and acquires information necessary for UE context and bearer setting from the MME An example of a method of establishing multiple connectivity with alternative base stations with the obtained UE context is shown.
  • the temporary serving base station After the UE transmits the RRC Connection Request message to the temporary serving base station, and before the temporary serving base station requests the multi-connection configuration to the candidate alternative base stations, the temporary serving base station establishes the context and bearer setting of the UE from the MME. eg, E-RAB).
  • 30B also shows a case where the provisional serving base station becomes a serving base station.
  • the temporary serving base station Since the temporary serving base station requests a multi-connection setup after performing the NAS procedure, it has a UE context received from the MME.
  • a multi-connection connection setup includes a UE context.
  • the terminal After the multi-connection setup is completed, if the result is delivered to the terminal, the terminal transmits an RRC Connection Setup Complete message to the serving base station.
  • the serving base station may obtain a UE context from the MME through a NAS procedure using a NAS message (e.g., Attach Request) included in the RRC connection request.
  • a NAS message e.g., Attach Request
  • the alternative base stations may establish S1-C and S1-U connections through a procedure of obtaining a security key for multiple connectivity.
  • FIG. 31 is a flowchart illustrating still another example of a procedure for establishing an S1-C and S1-U connection with alternative base stations proposed herein.
  • FIG. 31 illustrates an MME for corresponding alternative base stations in a procedure of establishing multiple connectivity with a plurality of alternative base stations based on a link quality value (eg, PER value, number of RBs, etc.) for the Salping MCS Capable terminal.
  • a link quality value eg, PER value, number of RBs, etc.
  • S1-C Signaling connection the method for setting the S-GW and S1-U Bearer.
  • the MCS Capable terminal refers to a terminal capable of performing MCS.
  • the RRC Connection Setup Complete message S3101 includes an Attach Request including information such as IMSI and UE Network Capability.
  • the serving base station includes an eNB UE S1AP ID for S1 signaling connection establishment and an indicator indicating that the terminal to be registered in the network is an MCS Capable UE together with the Attach Request in an Initial UE message to the MME (S3102).
  • the MME allocates an MME UE S1AP ID to the UE, thereby establishing an S1 signaling connection between the eNB and itself (MME).
  • the MME performs a procedure for setting the EPS Session and Default EPS Bearer for the terminal.
  • the MME determines resources necessary for E-RAB generation and information necessary for NAS signaling and transmits them to the serving base station.
  • the MME transmits an Attach Accept to the UE.
  • the Attach Accept may include a GUTI, a TAI List, an EPS Bearer ID, a QoS parameter received from the UE-AMBR, and an S-GW.
  • the Attach Accept is transmitted through an Initial Contest Setup Request in the base station and the MME section, and is transmitted through the RRC Connection Reconfiguration in the base station and the UE section.
  • the MME is an Initial Context Setup including E-RAB ID, E-RAB QoS, KeNB, UE Security Capability, etc., so that the serving base station can configure the S-GW and S1-U Bearer, and configure the UE and DRB.
  • the request message is transmitted to the serving base station (S3103).
  • the serving base station delivers the Attach Accept included in the Initial Context Setup Request message to the terminal through an RRC Connection Reconfiguration message (S3104) and generates a DRB.
  • the serving base station transmits an Initial Context Setup Response message including the DRB generation result to the MME (S3105).
  • the serving base station completes S1 bearer setup with the S-GW so that the E-RAB is configured.
  • the UE In response to the Attach Accept, the UE delivers Attach Complete.
  • the Attach Complete is transmitted through a UL Information Transfer message between the UE and the base station, and is transmitted through an UPLINK NAS Transport message between the base station and the MME.
  • the UE sends an RRC Connection Reconfiguration message including an indicator indicating that a (wireless) link quality value (eg, PER) will be changed from the serving base station, a link quality value to be changed, and a time point at which the link quality value to be changed is applied.
  • a (wireless) link quality value eg, PER
  • the UE may detect a link quality degradation of the serving base station (S3106) and obtain information about a minimum link quality value that each base station can provide through SIB transmitted from neighboring base stations. .
  • a guarantee time indicator indicating that the current PER and the corresponding PER will be guaranteed for some time may be considered.
  • the UE can select a neighbor base station having a longer link quality guarantee time for neighboring base stations providing the same link quality.
  • the terminal reports the link quality change to the serving base station based on the obtained link quality related information (S3107), and through this, may transmit information about identifiers of neighboring base stations, link quality values provided by neighboring base stations, and the like.
  • the terminal searches for an alternative base station (two) in which the sum of the link quality value to be changed of the serving base station and the minimum link quality value of the searched alternative base station (say log sum) satisfies the target link quality of the MCS.
  • the subcarrier transmits information to the serving base station about the alternative base stations whose sum of the changed link quality value of the serving base station and the found alternative base station link quality value satisfies the target link quality of the MCS.
  • the serving base station identifies the alternative base station (s) whose sum of the link quality value to be changed of the serving base station and the minimum link quality value of the found alternative base station satisfies the target link quality of the MCS, the serving base station
  • the multi-connection setup request is made to the corresponding alternative base stations, and a response to the multi-connection setup request is received from each alternative base station (S3108).
  • the terminal If the sum of the link quality value to be changed of the serving base station and the minimum link quality value of the alternative base station does not satisfy the target link quality of the corresponding MCS, the terminal is deficient in link quality as insufficient for the target link quality for the MCS. Further inform the serving base station.
  • the serving base station transmits the information on the insufficient link quality to the alternative base station for the multi-connection establishment.
  • the serving base station receives a multi-connection setup complete message in response to the multi-connection setup request.
  • the Multi-Connection Setup Complete message includes (1) when the terminal does not need to synchronize with the alternative base stations, includes an identifier of the alternative base stations and a C-RNTI corresponding to each alternative base station, and (2) the terminal receives the alternative base station. If it is necessary to synchronize with the mobile station, it includes the identifier of the alternative base stations and the Random Access Preamble corresponding to each alternative base station.
  • the serving base station notifies the terminal of the result of the multi-connection configuration through the RRC Connection Reconfiguration message (S3109).
  • the terminal needs to synchronize with the corresponding alternative base station (s) (candidate target base station 2), it synchronizes with the timing, transmits its own preamble to the corresponding alternative base station (s), and responds thereto. Receive a Random Access Response.
  • the terminal can receive the C-RNTI from each of the alternative base stations.
  • the serving base station transmits a multi-connection setup indication message indicating that the multi-connection setup is completed for the corresponding UE to the MME (S3110).
  • the Multi-Connection Setup Indication message includes a UE identifier and an identifier of alternate base stations established for multi-connection for the UE (identifier list for alternate base stations connected to the RRC Inactive state).
  • the MME receiving the Attach Complete generates individual K eNBs for alternative base stations (S3111).
  • the K eNB is a combination of a K ASME generated as a result of successful authentication of the UE by the MME and a multiple connectivity counter to alternative base stations maintained by the MME for each user requesting multiple connectivity. Is generated.
  • the multi-connection counter is used to ensure freshness of the K eNB delivered to the alternative base stations, and can be operated in various ways.
  • the MME may operate a separate counter to generate a K eNB by applying a different value every time it attempts multiple connectivity for the alternative base stations (in this case, a small size Counter is required).
  • the MME receives a list of identifiers for the alternative base stations connected to the Complete Complete and the RRC Inactive state from the UE, the MME generates K eNBs for each alternative base station, and sets the generated KeNB with the E-RAB configuration to the corresponding UE.
  • a multi-connection context setup request message is transmitted to each alternative base station (S3112), and in response thereto, a multi-connection context setup response message is received (S3113).
  • the Multi-Connection Context Setup Request message includes an E-RAB ID to be set for each alternative base station, E-RAB QoS information, and an alternate E-RAB indication indicating that the E-RAB is configured through the alternative base station. can do.
  • the MME includes the MME UE S1AP ID for S1 signaling connection establishment in the Multi-Connection Context Setup Request message and delivers them to the alternative base stations, and the alternative base stations receive the Multi-Connection Context Setup Request message from the MME to the corresponding UE.
  • the eNB UE S1AP ID for the S1 Signaling connection between the MME and itself By assigning the eNB UE S1AP ID for the S1 Signaling connection between the MME and itself.
  • 32 is a flowchart illustrating still another example of a procedure for establishing an S1-C and S1-U connection with alternative base stations proposed herein.
  • FIG. 32 is a procedure for setting up a multi-connection with a plurality of alternative base stations based on an MME indication when configuring a dedicated bearer for MCS for an MCS Capable terminal, and connecting the MME and S1-C signaling to the corresponding alternative base stations.
  • An example of a method for setting the S-GW and S1-U Bearer is shown.
  • the MME When the dedicated bearer configuration for the MCS is required for the terminal, when the MME receives the P-GW request through the S-GW, the MME transmits an E-RAB Setup Request message to the serving base station (S3201).
  • the serving base station can determine which QoS has an MCS through the QoS parameter included in the E-RAB Setup Request message, and can set a corresponding DRB for the corresponding terminal.
  • the serving base station may set up a multi-connection as necessary for the terminal, while setting the DRB to the terminal.
  • the serving base station receiving the E-RAB Setup Request message for the MCS from the MME determines the load status of each neighboring base station based on the information on the neighboring base stations periodically reported by the corresponding terminal, and has the best load situation. Set up multiple connections to the base station (s).
  • neighboring base stations measured and grasped by the UE may be limited to neighboring base stations satisfying a threshold of received signal quality to be searched by an alternate (base station) link.
  • the terminal selects neighboring base stations having a better signal quality than the "threshold signal quality defined for the substitute base station link" broadcasted from the serving base station through the SIB, and delivers it to the serving base station.
  • the serving base station receives C-RNTI or Dedicated Preamble from the alternative base station as a result of the multi-connection setup.
  • the serving base station transmits an RRC Connection Reconfiguration message including the result of the multiple connection configuration and the identifier of the alternative base station to the terminal (S3202).
  • the S1 E-RAB Setup Request message may include an indicator that specifies that the MCS Bearer is set up so that multiple connections need to be established, that is, a Multi-Connection Setup Indication.
  • the S1 E-RAB Setup Request message may include a newly defined QCI value for the MCS in the E-RAB QoS Parameters IE.
  • the serving base station transmits an RRC Connection Reconfiguration message indicating that multiple connectivity is established for the alternative base stations to the terminal (S3202).
  • the serving base station may transmit information such as radio bearer QoS, session management request, EPS bearer ID, etc. to inform the terminal that the bearer for the MCS is configured, as defined in LTE / LTE-A.
  • the serving base station transmits a multi-connection setup indication message indicating that the multi-connection setup is completed for the corresponding UE to the MME (S3203).
  • the Multi-Connection Setup Indication message includes a UE identifier and an identifier of alternate base stations configured for multi-connection for the UE (list of identifiers for alternate base stations connected in an RRC Inactive state).
  • the MME receiving the Attach Complete generates individual K eNBs for alternative base stations.
  • the K eNB is a combination of a K ASME generated as a result of successful authentication of the UE by the MME and a multiple connectivity counter to alternative base stations maintained by the MME for each user requesting multiple connectivity. Is generated.
  • the multi-connection counter is used to ensure freshness of the K eNB delivered to the alternative base stations, and can be operated in various ways.
  • each time the UE attempts multiple connectivity to the alternative base stations for each terminal a different value may be applied to each alternative base station to generate a K eNB (in this case, a large size counter is required), or the terminal may be
  • the MME may operate a separate counter to generate a K eNB by applying a different value every time it attempts multiple connectivity for the alternative base stations (in this case, a small size Counter is required).
  • the MME receives a list of identifiers for the alternative base stations connected to the Complete Complete and the RRC Inactive state from the UE, the MME generates K eNBs for each alternative base station, and sets the generated KeNB with the E-RAB configuration to the corresponding UE.
  • the multi-connection context setup request message is transmitted to the alternative base stations (S3204), and in response thereto, the multi-connection context setup response message is received (S3205).
  • the Multi-Connection Context Setup Request message includes an E-RAB ID to be set for each alternative base station, E-RAB QoS information, and an alternate E-RAB indication indicating that the E-RAB is configured through the alternative base station. can do.
  • the MME includes the MME UE S1AP ID for S1 signaling connection establishment in the Multi-Connection Context Setup Request message and delivers them to the alternative base stations, and the alternative base stations receive the Multi-Connection Context Setup Request message from the MME to the corresponding UE.
  • the eNB UE S1AP ID for the S1 Signaling connection between the MME and itself By assigning the eNB UE S1AP ID for the S1 Signaling connection between the MME and itself.
  • 33 is a block diagram illustrating a wireless device in which the methods proposed herein may be implemented.
  • the wireless device may be a network entity, a base station, a terminal, and the like, and the base station includes both a macro base station and a small base station.
  • the base station 20 and the terminal 10 include a communication unit (transmitter and receiver, an RF unit, 3313 and 3323), a processor 3311 and 3321, and a memory 3312 and 3322.
  • the base station and the terminal may further include an input unit and an output unit.
  • the communication units 3313 and 3323, the processors 3311 and 3321, the input unit, the output unit, and the memory 3312 and 3322 are functionally connected to perform the method proposed in the present specification.
  • the communication unit transmitter / receiver unit or RF unit, 3313, 3323
  • the communication unit receives information generated from the PHY protocol (Physical Layer Protocol)
  • the received information is transferred to the RF-Radio-Frequency Spectrum, filtered, and amplified.
  • the communication unit functions to move an RF signal (Radio Frequency Signal) received from the antenna to a band that can be processed by the PHY protocol and perform filtering.
  • the communication unit may also include a switch function for switching the transmission and reception functions.
  • Processors 3311 and 3331 implement the functions, processes and / or methods proposed herein. Layers of the air interface protocol may be implemented by a processor.
  • the processor may be represented by a controller, a controller, a control unit, a computer, or the like.
  • the memories 3312 and 3322 are connected to a processor and store protocols or parameters for performing the method proposed in the present specification.
  • Processors 3311 and 3321 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices.
  • the memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device.
  • the communication unit may include a baseband circuit for processing a wireless signal.
  • the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function.
  • the module may be stored in memory and executed by a processor.
  • the memory may be internal or external to the processor and may be coupled to the processor by various well known means.
  • the output unit (display unit or display unit) is controlled by a processor and outputs information output from the processor together with a key input signal generated at the key input unit and various information signals from the processor.
  • the method proposed in the present specification may be embodied as a processor readable code on a processor readable recording medium included in a network device.
  • the processor-readable recording medium includes all kinds of recording devices that store data that can be read by the processor. Examples of the processor-readable recording medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, and the like, and may also be implemented in the form of a carrier wave such as transmission over the Internet. .
  • the processor-readable recording medium can also be distributed over network coupled computer systems so that the processor-readable code is stored and executed in a distributed fashion.
  • Disclosed herein is a method of establishing an S1 connection in a wireless communication system.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Databases & Information Systems (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention concerne un procédé pour configurer un support dans un système de communication sans fil, le procédé étant réalisé par une première station de base et consistant : à recevoir, à partir d'une entité de réseau, un premier message demandant une configuration de support d'accès radio E-UTRAN (E-RAB) pour un service essentiel de mission (MCS) ; à transmettre, à au moins une seconde station de base, un second message demandant une configuration de liaison alternative avec un terminal sur la base du premier message reçu ; et à recevoir, à partir d'au moins l'une de la seconde station de base, un message de réponse correspondant au second message.
PCT/KR2015/013681 2015-12-14 2015-12-14 Procédé pour réaliser une connexion s1 entre une station de base alternative et une entité de réseau dans un système de communication sans fil et appareil pour prendre en charge ce dernier Ceased WO2017104858A1 (fr)

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