WO2017086496A1

WO2017086496A1 - Method and apparatus for allocating terminal identifier in wireless communication system

Info

Publication number: WO2017086496A1
Application number: PCT/KR2015/012341
Authority: WO
Inventors: 한진백; 조희정; 이은종; 변일무
Original assignee: 엘지전자(주)
Priority date: 2015-11-17
Filing date: 2015-11-17
Publication date: 2017-05-26

Abstract

The present invention relates to a method and an apparatus for allocating a terminal identifier in a wireless communication system supporting a low latency service. The present invention provides a method comprising the steps of: transmitting a request message for requesting multi-link establishment with a terminal to at least one alternative base station, wherein the request message includes a common terminal identifier indicating a terminal identifier which is commonly used by a serving base station and the at least one alternative base station in order to identify the terminal; receiving a response message from the at least one alternative base station in response to the request message; and transmitting the common terminal identifier to the terminal.

Description

Method and apparatus for allocating terminal identifier in wireless communication system

The present invention relates to a method for allocating a terminal identifier for establishing a bearer in a wireless communication system, and more particularly, to a method for establishing a multi-connection with one or more base stations, a method for allocating a terminal identifier, and an apparatus for supporting the same. It is about.

The mobile communication system has been developed to provide a voice service while ensuring the user's activity. However, the mobile communication system has expanded not only voice but also data service, and the explosive increase in traffic causes a shortage of resources and users require a higher speed service. .

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

Currently, the availability of radio link in LTE / LTE-A system is entirely dependent on the probability of providing network coverage, which is approximately 95%.

In addition, the radio link reliability of the LTE / LTE-A system is BER (Block Error Rate) 10 in the case of Unicast data through PDSCH, without a distinction between a control plane (C-Plane) and a user plane (U-Plane). It is assumed that -3 can be applied to provide sufficient reliability with H-ARQ retransmission.

Although the current LTE / LTE-A system is highly active and provides various services, it does not always provide connectivity that guarantees reliability to meet Mission Critical Services (MCS) in all time intervals. can not do it.

This is because the LTE / LTE-A system itself is designed to provide relatively good connectivity for most of the time, providing near zero data rates in certain Poor Coverages that experience extreme interference or heavy network resources. Done.

In the future, new MCSs are expected to rely heavily on the availability / reliability of radio links to satisfy a high level of communication quality. There is a need for an evolution of a radio technology in which such new MCSs can be accommodated.

Therefore, the present specification is intended to provide a method for realizing the "Truly Reliable Communication" of 5G to escape from the "Best Effort Mobile Broadband" of the current LTE / LTE-A system.

That is, an object of the present specification is to provide a method for establishing a multi-connection with a plurality of base stations when configuring an MCS bearer for terminals receiving MCSs in a future 5G mobile communication system.

In addition, the present specification is to provide a method for preventing the waste of the terminal identifier (eg, C-RNTI) that can be excessively assigned in the process of establishing a multi-connection.

The proposed herein Smart Car Safety Services, in providing such a remote control service, such as medical / industrial / robot, while satisfying the requirements that the transmission delay requirement of less than 1ms at the same time high reliability ^{^{(Packet Error Rate <10 - 6}} ) This is a method for realizing a flexible radio link connection control to improve the radio link quality satisfaction of the terminal for the required applications.

Searching and maintaining an alternative base station in addition to the radio link being used by the terminal means that the terminal can always have radio links satisfying the minimum QoE requirements for the MCSs within a specific geographic area. .

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

In the present specification, a method for allocating a terminal identifier in a wireless communication system, wherein the method performed by a serving base station transmits a request message for requesting multi-link establishment with a terminal to at least one alternative base station, wherein the request message Includes a common terminal identifier indicating a terminal identifier commonly used by the serving base station and the at least one alternative base station to identify the terminal; Receiving a response message from the at least one alternative base station in response to the request message; And transmitting the common terminal identifier to the terminal.

The present invention further includes the step of the serving base station generating the common terminal identifier.

In the present invention, the common terminal identifier is at least two of a terminal ID indicating the terminal, an alternative base station ID indicating the at least one alternative base station, or a C-RNTI indicating a terminal identifier assigned to the terminal by the serving base station. It is generated based on the dog.

Also, in the present invention, when the common terminal identifier is generated based on the terminal ID, '0' is padded on the right or left side of the terminal ID.

In addition, in the present invention, when the common terminal identifier is generated based on the neighbor base station ID, the right or left side is truncated to 16 bits in length.

The present invention also provides a method comprising: transmitting a load state request message for requesting a load state to the at least one neighboring base station; And receiving a load status response message including a current load status to the at least one neighboring base station.

Also, in the present invention, the common terminal identifier is transmitted to an alternative base station having a good current load.

The present invention also transmits a request message for requesting multi-link establishment with a terminal to at least one alternative base station, wherein the connection request message provides autonomous allocation of a terminal identifier for identifying the terminal to at least one alternative base station. Autonomous allocation indication information indicating; And receiving a response message in response to the connection request message.

In addition, the present invention, the step of receiving a multilink activation message requesting the activation of the multilink from the terminal; Transmitting a link activation request message for requesting multilink activation with the terminal to a specific alternative base station among the at least one alternative base station; Receiving a link activation response message including the terminal identifier from the specific alternative base station; And transmitting the terminal identifier to the terminal.

In addition, the present invention, the step of transmitting a request message for requesting the multi-link configuration with the terminal to at least one alternative base station; Receiving a response message from the at least one alternative base station in response to the request message, wherein the response message includes terminal identifier allocation delay indication information indicating a delay of allocation of a terminal identifier for identifying the terminal; And delay information indicating whether the terminal identifier allocation is delayed to the terminal or information of alternative base stations that delay the terminal identifier allocation.

In addition, the present invention, the step of receiving a multi-link activation message requesting the activation of the multilink from the terminal; Transmitting a link activation request message for requesting multilink activation with the terminal to a specific alternative base station among the at least one alternative base station; Receiving a link activation response message including the terminal identifier from the specific alternative base station; And transmitting the terminal identifier to the terminal.

The present invention also transmits a request message for requesting multi-link establishment with a terminal to at least one alternative base station, wherein the request message includes terminal identifier recovery instruction information indicating the number of terminal identifiers; Receiving a response message in response to the request message from the at least one alternative base station, wherein the response message includes a terminal identifier validity timer indicating the terminal identifier and a valid time of the terminal identifier; And transmitting the terminal identifier and the terminal identifier valid timer to the terminal.

The present invention also provides a method comprising: receiving a multilink release request message indicating that the multilink release request and the terminal identifier have been recovered from a specific alternative base station among the at least one alternative base station; Transmitting a multilink release response message to the at least one alternative base station in response to the multilink release request message; And transmitting, to the terminal, base station information including information on the specific base station that has released the multilink and recovered the terminal identifier.

In addition, the present invention, the communication unit for transmitting and receiving a radio signal with the outside; And a processor that is functionally coupled with the communication unit, wherein the processor transmits a request message for requesting multilink establishment with a terminal to at least one alternative base station, wherein the request message includes the serving base station and the at least one. A common terminal identifier indicating a terminal identifier commonly used by the alternative base station to identify the terminal, receiving a response message in response to the request message from the at least one alternative base station, and transmitting the common to the terminal. Provides a base station for controlling to transmit an identifier.

In the present specification, when a terminal and a plurality of base stations set up a multilink, an excessive allocation of the terminal identifier may be prevented by allowing the plurality of base stations to autonomously allocate the terminal identifier.

In addition, in the present specification, when a terminal and a plurality of base stations establish a multilink, a plurality of base stations inform the terminal of a delay of assigning a terminal identifier, and the terminal requests and assigns a terminal identifier to the base station when the terminal activates the multilink. Excessive allocation of the terminal identifier can be prevented.

In addition, in the present specification, the terminal and the plurality of base stations do not allocate the terminal identifier to the terminal in the process of setting up the multilink, and when the terminal activates the multilink, the terminal requests the terminal identifier from the base station and is assigned. Excessive allocation of identifiers can be prevented.

In addition, the present specification may prevent excessive allocation of the terminal identifier by generating a terminal identifier commonly used by the serving base station and the plurality of alternative base stations to identify the terminal in the process of establishing the multilink.

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

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.

2 is a diagram illustrating a wireless communication system to which the present invention is applied.

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.

4 (a) shows an example of a radio protocol architecture for a user plane to which the technical features of the present specification can be applied, and FIG. 4 (b) shows the technical features of the present specification to which the technical features of the present specification are applied. FIG. 1 is a block diagram illustrating an example of a radio protocol structure for a control plane.

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

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

7 is a diagram illustrating a bearer structure in a wireless communication system to which the present invention can be applied.

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.

9 illustrates an example of a dedicated bearer activation procedure.

10 illustrates an example of a dedicated bearer deactivation procedure.

11 illustrates a handover procedure defined in LTE (-A).

FIG. 12 is a diagram illustrating an operation of a terminal and a base station in a contention-based random access procedure.

13 is a flowchart illustrating a terminal operation of an RRC idle state to which the present invention can be applied.

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.

18 is a diagram illustrating a conceptual diagram of a multilink to which the methods proposed in the specification can be applied.

19 and 20 are flowcharts illustrating an example of a method of allocating a terminal identifier in multi-link configuration based on network indication proposed in the present specification.

21 and 22 are flowcharts illustrating still another example of a method for allocating a terminal identifier in multi-link configuration based on network indication proposed in the present specification.

23 and 24 are flowcharts illustrating still another example of a method for allocating a terminal identifier in multi-link configuration based on network indication proposed in the present specification.

25 to 28 are flowcharts illustrating an example of a method for allocating a terminal identifier when configuring a multilink based on a radio link quality value indicator proposed in the present specification.

29 and 30 are flowcharts illustrating still another example of a method for allocating a terminal identifier when configuring a multilink based on a radio link quality value indicator proposed in the present specification.

31 to 34 are flowcharts illustrating still another example of a method for allocating a terminal identifier in multilink configuration proposed in the present specification.

35 is a block diagram illustrating an example of a wireless device in which the methods proposed herein may be implemented.

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

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention.

In this specification, a base station has a meaning as a terminal node of a network that directly communicates with a terminal. The specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases. That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. A base station (BS) 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).

In addition, a 'terminal' may be fixed or mobile, and may include a user equipment (UE), a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), and an AMS ( Advanced Mobile Station (WT), Wireless Terminal (WT), Machine-Type Communication (MTC) Device, Machine-to-Machine (M2M) Device, Device-to-Device (D2D) Device, etc.

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

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

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

Before describing with reference to the drawings, in order to help the understanding of the present invention, terms used herein will be briefly defined.

EPS: stands for Evolved Packet System and means a core network supporting a Long Term Evolution (LTE) network. UMTS evolved network

Public data network (PDN): An independent network on which servers providing services are located

APN (Access Point Name): The name of the access point managed by the network, which is provided to the 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 (TEID): 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, which stands for Mobility Management Entity, serves to control each entity in EPS to provide session and mobility for the UE.

Session: 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.

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. This means an inter-entity connection (terminal-PDN GW) in the core network so that a session can be established.

UE Context: The context information of the UE used to manage the UE in the network, that is, the context information composed of the UE id, mobility (current location, etc.), and attributes of the session (QoS, priority, etc.).

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 radio 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). LTE and SAE include an Evolved Packet System (EPS).

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. E-UTRAN and EPC both set up and release bearers required by the application.

EPC, also called CN (core network), controls the UE and manages the bearer's configuration.

As shown in FIG. 1, 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.

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. 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).

The P-GW 30 performs IP address assignment for the UE and performs flow-based charging according to 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.

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. Technique.

As shown in FIG. 1, various interfaces such as S1-U, S1-MME, S5 / S8, S11, S6a, Gx, Rx, and SG may be defined between EPS network elements.

Hereinafter, the concept of mobility management (MM) and mobility management (MM) back-off timer will be described in detail. Mobility Management (MM) is a procedure to reduce overhead on the E-UTRAN and processing at the UE.

When mobility management (MM) is applied, all information related to the UE in the access network may be released during the period in which data is deactivated. The MME may maintain information related to the UE context and the configured bearer during the idle period.

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.

If there is downlink data to be delivered to the UE 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.

The base station then begins paging for the UE over a radio interface. As the paging message is received, a procedure for causing the state of the UE to transition to the ECM-CONNECTED state is performed. This procedure may 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.

When the above described mobility management (MM) procedure is performed, a mobility management (MM) backoff timer may be further used. Specifically, 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 time associated with the MM backoff timer You can provide a value. Upon receiving the time value, the UE may activate the MM backoff timer.

2 shows a wireless communication system to which the present invention is applied.

This may also be called an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN), or Long Term Evolution (LTE) / LTE-A system.

The E-UTRAN includes a base station (BS) 20 that provides a control plane and a user plane to a user equipment (UE).

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.

EPC consists of MME, S-GW and Packet Data Network Gateway (P-GW). The MME has access information of the terminal or information on 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, and 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) can be divided into a physical layer belonging to the first layer of the information transfer service (Information Transfer Service) using a physical channel (Physical Channel), The RRC (Radio Resource Control) 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.

Referring to FIG. 3, hatched blocks represent radio protocol layers and empty blocks represent functional entities in the control plane.

The base station performs the following functions. (1) Radio resource management such as radio bearer control, radio admission control, connection mobility control, and dynamic resource allocation to a terminal RRM), (2) Internet Protocol (IP) header compression and encryption of user data streams, (3) routing of user plane data to S-GW, and (4) paging messages. 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 (Non-Access) Stratum) Ciphering and Integrity Protection of Signaling.

S-GW performs the following functions. (1) termination of user plane packets for paging, and (2) user plane switching to support terminal mobility.

The user plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

Referring to FIGS. 4A and 4B, a physical layer (PHY) layer provides an information transfer service to a higher layer using a physical channel. . The physical layer is connected to the upper layer MAC (Medium Access Control) 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.

Data moves between physical layers between physical layers, that is, between physical layers of a transmitter and a receiver. The physical channel may be modulated by an orthogonal frequency division multiplexing (OFDM) scheme and utilizes time and frequency as radio resources.

The function of the MAC layer is a 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.

Functions of the RLC layer include concatenation, segmentation, and reassembly of RLC SDUs. In order to guarantee the various Quality of Service (QoS) required by the radio bearer (RB), the RLC layer has a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (Acknowledged Mode). 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.

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 transmission 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). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

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). Meanwhile, 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.

It is located above the transport channel, and the logical channel mapped to the transport channel is a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic (MTCH). Channel).

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. In addition, 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 (TTI) is a unit time of subframe transmission.

Table 1 below shows an example of RNTI values used in the present invention.

Table 2 below shows an example of use of each RNTI values and associated logical and transport channels.

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 on an S1 interface, and FIG. 5B illustrates a user plane interface protocol structure on an S1 interface.

Referring to FIG. 5, an S1 control plane interface (S1-MME) is defined between a base station and an MME. Similar to the user plane, the transport network layer is based on IP transport. However, it is added to the SCTP (Stream Control Transmission Protocol) layer above the IP layer for reliable transmission of message signaling. The application layer signaling protocol is referred to as S1-AP (S1 application protocol).

The SCTP layer provides guaranteed delivery of application layer messages.

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

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

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

The S1 user level 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 GTP-U (GPRS Tunneling Protocol User Plane) layer is used above the UDP / IP layer to deliver user plane PDUs between the eNB and the S-GW.

EMMEMM 및 ECM 상태 And ECM status

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

Referring to FIG. 6, an EMM registered state (EMM-REGISTERED) according to whether a terminal is attached or detached from a network in order to manage mobility of the terminal in a NAS layer located on a control plane of the terminal and the MME. ) And the EMM deregistration state (EMM-DEREGISTERED) can be defined. The EMM-REGISTERED state and the EMM-DEREGISTERED state may be applied to the terminal and the MME.

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

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

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

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

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

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

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

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

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

When a terminal is connected to a packet date network (PDN) (peer entity in FIG. 7), a PDN connection is generated, and the PDN connection may also be called an EPS session. PDN provides service functions such as the Internet or IP Multimedia Subsystem (IMS) through an external or internal IP (Internet protocol) network.

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

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

The E-RAB delivers the packet of the EPS bearer between the terminal and the EPC. If there is an E-RAB, the E-RAB bearer and the EPS bearer are mapped one-to-one. A data radio bearer (DRB) delivers 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. 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 terminal 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 on 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 mapping information between the downlink packet filter and the S5 / S8 bearer in order to bind between the SDF and the S5 / S8 bearer in the downlink.

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

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

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

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

While the terminal uses a service (for example, the Internet, etc.) through the default bearer, the terminal may use an insufficient service (for example, Video 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 when establishing / modifying an EPS session for a terminal and applies it while the EPS session is maintained. This is called PCC (Policy and Charging Control). The PCC rule is determined based on an operator policy (eg, QoS policy, gate status, charging method, etc.).

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

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

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

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

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

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

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

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

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

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

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

FIG. 8A illustrates an ECM-CONNECTED state and FIG. 8B illustrates an ECM-IDLE.

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

As shown in FIG. 8A, in the ECM-CONNECTED state with user traffic, a NAS signaling connection, that is, an ECM connection (that is, an RRC connection and an S1 signaling connection) is established. In addition, an S11 GTP-C (GPRS Tunneling Protocol Control Plane) connection is established between the MME and the SGW, and an S5 GTP-C connection is established between the SGW and the PDN GW.

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

As shown in FIG. 8 (b), in the ECM-IDLE state in which there is no user traffic, the ECM connection (that is, the RRC connection and the S1 signaling connection) is released. However, S11 GTP-C connection between MME and SGW and S5 GTP-C connection between SGW and PDN GW are maintained.

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

9 illustrates an example of a dedicated bearer activation procedure.

9 is a flowchart illustrating a dedicated bearer activation procedure for S5 / S8 based on GPRS Tunneling Protocol (GTP).

First, when a dynamic PCC is deployed, the PCRF transmits a PCC decision provision (QoS policy) message to the PDN GW.

Next, 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.

Next, 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.

Next, 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.

Next, the eNodeB transmits an RRC Connection Reconfiguration (Radio Bearer QoS, Session Management Request, EPS RB Identity) message to the UE.

Next, the UE transmits an RRC Connection Reconfiguration Complete message to the eNodeB to inform radio bearer activation.

Next, 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.

Next, the UE transmits a Direct Transfer (Session Management Response) message to the eNodeB.

Next, the eNodeB transmits an Uplink NAS Transport (Session Management Response) message to the MME.

Next, the MME transmits a Create Bearer Response (EPS Bearer Identity, S1-TEID, User Location Information (ECGI)) message to the Serving GW to inform bearer activation to the Serving GW.

Next, 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.

If a dedicated bearer activation procedure is triggered by a PCC Decision Provision message from the PCRF, the PDN GW indicates to the PCRF whether a requested PCC decision (QoS policy) has been performed.

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).

The procedure of FIG. 10 may be used to deactivate a dedicated bearer or to deactivate all bearers belonging to a PDN address.

If a default bearer belonging to the PDN connection is deactivated, 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 about 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 hand over the terminal based on the measurement report and RRM (Radio Resource Management) information.

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. In addition, the container may further include additional parameters such as connection parameters, SIBs, and the like.

In addition, 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) to minimize handover delay, One of the group 1 may be selected and informed to the handover terminal.

That is, the container may further include information about the dedicated RA signature. In addition, 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.

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.

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.

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-competitive basis if a dedicated RACH preamble is allocated, 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 confirms the handover by sending an RRCConnectionReconfigurationComplete message (C-RNTI) and informs the target base station that the handover process is completed by sending an uplink buffer status report. . 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.

(1) first message transmission

First, 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 (S12010).

(2) receiving the second message

The method of receiving the random access response information is similar to that in the non- contention based random access procedure described above. That is, after the UE transmits the random access preamble as in step S12010, the base station attempts to receive its random access response within the random access response receiving window indicated by the system information or the handover command, and responds. The PDSCH is received through the RA-RNTI information (S12020). Through this, an UL grant, a temporary C-RNTI, a timing synchronization command (TAC), and the like may be received.

(3) third message transmission

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. In addition, the UL grant transmits data (ie, a third message) to the base station (S12030). The third message should include the identifier of the terminal. In the contention-based random access process, the base station cannot determine which UE performs the random access process, because the UE needs to be identified for future collision resolution.

Two methods have been discussed as a method of including the identifier of the terminal. In 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. On the other hand, if a valid cell identifier has not been allocated before the random access procedure, the terminal transmits its own unique identifier (eg, S-TMSI or random ID). In general, the unique identifier is longer than the cell identifier. If the UE transmits data corresponding to the UL grant, it starts a contention resolution timer.

(4) receiving the fourth message

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 for collision resolution. That is, an attempt is made to receive a PDCCH in order to receive a specific message (S12040). 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. Then, in the former case, if the PDCCH is received through its cell identifier before the conflict resolution timer expires, the terminal determines that the random access procedure has been normally performed, and terminates the random access procedure. In the latter case, if the PDCCH is received through the temporary C-RNTI before the conflict resolution timer expires, the data transmitted by the PDSCH indicated by the PDCCH is checked. If a unique identifier is included in the content of the data, the terminal determines that the random access procedure has been normally performed, and terminates the random access procedure.

Hereinafter, the RRC state and the RRC connection method of the UE will be described in detail.

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 referred to as an RRC idle state. 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.

On the other hand, 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 than the cell. That is, the terminal in the RRC idle state is only detected in a large area unit, and must move to the RRC connection state in order to receive a normal mobile communication service such as voice or data.

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. When 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. There are several cases in which a 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 received from E-UTRAN. In one case, the response message may be transmitted.

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

In order to manage mobility of the UE in the NAS layer, two states of EMM-REGISTERED (EPS Mobility Management-REGISTERED) and EMM-DEREGISTERED are defined, and these two states are applied to the UE 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 attach procedure is successfully performed, the UE and the MME are in the EMM-REGISTERED state.

In order to manage a signaling connection between the UE and the EPC, two states are defined, an EPS Connection Management (ECM) -IDLE state and an ECM-CONNECTED state, and these two states are applied to the UE and the MME. When the UE in the ECM-IDLE state establishes an RRC connection with the E-UTRAN, the UE is in the ECM-CONNECTED state.

The MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes an S1 connection with the E-UTRAN. When the terminal is in the ECM-IDLE state, the E-UTRAN does not have context information of the terminal. Accordingly, the UE in the ECM-IDLE state performs UE-based mobility related procedures such as cell selection or cell reselection without receiving a command from the network. On the other hand, when the terminal is in the ECM-CONNECTED state, the mobility of the terminal is managed by the command of the network. In the ECM-IDLE state, if the position of the terminal is different from the position known by the network, the terminal informs the network of the corresponding position of the terminal through a tracking area update procedure.

The following is a description of system information.

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.

According to Section 5.2.2 of 3GPP TS 36.331 V8.7.0 (2009-09) "Radio Resource Control (RRC); Protocol specification (Release 8)", the system information includes a master information block (MIB) and a scheduling block (SB). It is divided into SIB (System Information 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.

In general, services provided by a network to a terminal can be classified into three types as follows. In addition, 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.

1) Limited service: This service provides Emergency call and Tsunami Warning System (ETWS) and can be provided in an acceptable cell.

2) Normal service: This service means a general use for general use, and can be provided in a suitable or normal cell.

3) Operator service: This service means service for network operator. This cell can be used only by network operator and not by general users.

In relation to the service type provided by the cell, the cell types may be classified as follows.

1) Acceptable cell (Acceptable cell): A cell in which the terminal can receive limited service. This cell is a cell which is not barred from the viewpoint of the terminal and satisfies the cell selection criteria of the terminal.

2) Normal cell (Suitable cell): a cell in which 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.

3) Barred cell: A cell that broadcasts information that a cell is a prohibited cell through system information.

4) Reserved cell: A cell that broadcasts information that a cell is a reserved cell through system information.

FIG. 13 illustrates a procedure in which an initially powered-on terminal registers with a network through a cell selection process and then reselects a cell if necessary.

Referring to FIG. 13, the terminal selects a radio access technology (RAT) for communicating with a public land mobile network (PLMN), which is a network to be serviced (S13010). 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).

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) (S13020). 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. After cell selection, 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.

If there is a need for network registration, the terminal performs a network registration procedure (S13030). The terminal registers its information (eg IMSI) in order to receive a service (eg paging) from the network. Whenever a cell is selected, the UE does not register with the accessing network, but registers with the network when the network information received from the system information (eg, Tracking Area Identity; TAI) is different from the network information known to the network. .

The terminal performs cell reselection based on the service environment provided by the cell or the environment of the terminal (S13040). 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 served 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. At this time, in order to prevent the cell from being frequently reselected according to the change of the signal characteristic, a time constraint is placed. The cell reselection procedure will be described later.

The terminal sends an RRC connection request message to the network requesting an RRC connection (S14010). The network sends an RRC Connection Setup message in response to the RRC connection request (S14020). After receiving the RRC connection setup message, the terminal enters the RRC connection mode.

The terminal sends an RRC Connection Setup Complete message used to confirm successful completion of RRC connection establishment to the network (S14030).

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 (S15010). In response to the RRC connection reconfiguration, the terminal sends an RRC connection reconfiguration complete message used to confirm successful completion of the RRC connection reconfiguration to the network (S15020).

The following describes the procedure for the terminal to select a cell in detail.

When the power is turned on or staying in the cell, 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.

Therefore, if the cell provides a radio signal quality of a certain level or more, even if this cell is not the cell providing the best radio signal quality to the terminal, it can be selected during the cell selection process of the terminal.

Now, referring to 3GPP TS 36.304 V8.5.0 (2009-03) "User Equipment (UE) procedures in idle mode (Release 8)", a method and procedure for the UE to select a cell in 3GPP LTE will be described in detail.

There are two main cell selection processes.

First, an initial cell selection process, in which the terminal does not have any prior information on the radio channel. Therefore, the terminal searches all radio channels to find an appropriate cell. In each channel, the terminal finds the strongest cell. Thereafter, if the terminal only finds a suitable cell that satisfies the cell selection criteria, the terminal selects the corresponding cell.

Next, the terminal may select the cell by using the stored information or by using the information broadcast in the cell. Therefore, the cell selection can be faster than the initial cell selection process. The terminal selects a corresponding cell if it finds a cell that satisfies the cell selection criteria. If a suitable cell that satisfies the cell selection criteria is not found through this process, the terminal performs an initial cell selection process.

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 the mobility of the terminal or a change in the wireless environment. 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.

This process is called cell reselection. 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.

In addition to the quality of the 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.

As described above, there is 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 the same center-frequency as 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 using a RAT different from the camping RAT.

The principle of the cell reselection process is as follows.

First, the UE measures the quality of a serving cell and a neighboring cell for cell reselection.

Second, 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. When the terminal receives the dedicated priority, the terminal may also receive a validity time associated with the dedicated priority. When the terminal receives 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. When the validity timer expires, the terminal discards the dedicated priority and applies the public priority again.

For inter-frequency cell reselection, the network may provide the UE with a parameter (for example, frequency-specific offset) used for cell reselection for each frequency.

For intra-frequency cell reselection or inter-frequency cell reselection, the network may provide the UE with a neighboring cell list (NCL) used for cell reselection. This NCL contains cell-specific parameters (eg cell-specific offsets) used for cell reselection.

For intra-frequency or inter-frequency 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.

Hereinafter, RLM (Radio Link Monitoring) will be described.

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 the purpose of monitoring the downlink radio link quality of the PCell and compares it with the 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.

Hereinafter, a radio link failure (RFF) will be described.

The terminal 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 radio link with the serving cell.

If the quality of the serving cell is so low that communication is almost impossible, the terminal determines the current situation as a radio link failure.

If the radio link failure is determined, the UE abandons communication maintenance 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.

(1) First, it may be determined that an RLF has occurred due to a physical channel problem.

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.

(2) It may be determined that RLF has occurred due to MAC Random Access problem.

When the UE performs a random access process in the MAC layer, random access resource selection-> random access preamble transmission-> random access response reception-> contention cancellation It goes 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.

(3) It may be determined that an RLF has occurred due to an RLC maximum retransmission problem.

The UE retransmits an RLC PDU that is not successfully transmitted when using an AM (Acknowledged Mode) RLC in the RLC layer.

However, if the AM RLC retransmits a certain number of times (eg, maxRetxThreshold) for a specific AMD PDU but does not succeed, 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. When RLF is generated in this way, RRC connection reestablishment, which is a procedure for reestablishing RRC connection with eNB, is performed.

The RRC connection reestablishment process, which is performed when RLF occurs, is as follows.

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. There are five serious problems with RRC connections: (1) Radio Link Failure (RLF), (2) Handover Failure, (3) Mobility from E-UTRA, (4) PDCP Integrity PDCP Integrity Check Failure, (5) RRC Connection Reconfiguration Failure.

When one of the above problems occurs, 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.

If a suitable cell is found through the cell selection procedure while the timer T311 is running, the terminal stops T311 and starts a random access procedure to the corresponding cell. However, if a suitable cell is not found until T311 expires, the UE determines that the RRC connection fails and transitions to the RRC_IDLE mode.

Hereinafter, the RRC connection reestablishment procedure will be described in more detail.

Referring to FIG. 16, 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). (S16010). In addition, each sublayer and physical layer are set to a default configuration. During this process, the UE maintains an RRC connection state.

The UE performs a cell selection procedure for performing the RRC connection reestablishment procedure (S16020). 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.

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 (S16030). If it is determined that the selected cell is an appropriate E-UTRAN cell, the UE transmits an RRC connection reestablishment request message to the cell (S16040).

On the other hand, if it is determined through the cell selection procedure for performing the RRC connection re-establishment procedure that the selected cell is a cell using a RAT other than E-UTRAN, the RRC connection re-establishment procedure is stopped, the terminal is in the RRC idle state Enter (S16050).

The terminal may be implemented to complete the cell suitability check within a limited time through the cell selection procedure and the reception of system information of the selected cell. To this end, 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. In LTE specification TS 36.331, 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.

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.

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 reconstructs the PDCP sublayer responsible for security with newly calculated security key values.

Through this, 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 (S16060).

On the contrary, if the RRC connection reestablishment request message is received from the terminal and the request is not accepted, the cell transmits an RRC connection reestablishment reject message to the terminal.

If the RRC connection reestablishment procedure is successfully performed, the cell and the terminal perform the RRC connection reestablishment procedure. Through this, the UE recovers the state before performing the RRC connection reestablishment procedure and guarantees the continuity of the service to the maximum.

This is followed by a description of the reporting of the RLF.

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.

After reestablishing the RRC connection, 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 these events from the MRO assessment of intra-LTE mobility connectivity failure and to write those events back as input to other algorithms.

If the RRC connection reestablishment fails or the UE fails to perform the RRC connection reestablishment, 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 terminal 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 attempted to reestablish.

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.

Time elapsed from last handover initialization to connection failure.

Information indicating whether the connection failure is due to RLF or handover failure.

-Wireless measurements.

-Location of failure.

Upon receiving the RLF failure from the terminal, the eNB 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 connectivity failure and send them back as input to other algorithms.

The measurement and the measurement report will be described below.

In a mobile communication system, mobility support of a terminal is essential. Accordingly, the UE continuously measures the quality of the serving cell and the neighboring cell that provide the current service. The terminal reports the measurement result to the network at an appropriate time, and the network provides the terminal with optimal mobility through handover. This measurement is commonly referred to as radio resource management (RRM) measurement.

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.

When the mobile station determines that the quality of a particular region is very poor through measurement, it may report the location information and the measurement result 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.

In a mobile communication system with a frequency reuse factor of 1, mobility is mostly between different cells in the same frequency band.

Therefore, in order to ensure the mobility of the terminal well, 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. As such, 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. When a service of a communication system is provided through a plurality of frequency bands, in order to guarantee optimal mobility to a terminal, 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.

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. For example, 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.

The terminal receives measurement configuration information from the base station (S17010). A message including measurement setting information is called a measurement setting message. The terminal performs the measurement based on the measurement setting information (S17020). If the measurement result satisfies the reporting condition in the measurement configuration information, the terminal reports the measurement result to the base station (S17030). A message containing a measurement result is called a measurement report message.

The measurement setting information may include the following information.

(1) Measurement object information: Information about an object to be measured by the terminal. 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. For example, 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, and the inter-RAT measurement object is The RAT of the serving cell may indicate a neighboring cell of another RAT.

(2) Reporting configuration information: Information on a reporting condition and a report type regarding when the terminal reports transmission of a measurement result. 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 report cycle or measurement report. The report format is information on what type the terminal configures the measurement result.

(3) 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.

(4) Quantitative configuration information: information on a parameter for setting filtering of a measurement unit, a reporting unit, and / or a measurement result value.

(5) 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.

In 3GPP LTE, the base station may set only one measurement target for one frequency band to the terminal. According to Section 5.5.4 of 3GPP TS 36.331 V8.5.0 (2009-03) "Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Resource Control (RRC); Protocol specification (Release 8)", The events that trigger the report are defined.

If the measurement result of the terminal satisfies the set event, the terminal transmits a measurement report message to the base station.

One of the increasingly important and specific areas of 5G mobile communication technology is reliable communication.

Reliable communication means a new communication service realized through error free transmission or service availability for realizing mission critical services (MCS).

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.

In addition, reliable communications must provide reliable connections for delay-sensitive applications such as traffic safety or for mission-critical machine-type communications (MTCs). do.

In addition, the need for reliable communication is also recognized for medical / emergency response, remote control, and sensing purposes.

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.

That is, the commercial radio technologies (including 3GPP LTE and LTE-A) proposed to date do not guarantee sufficient performance to provide various MCSs in terms of real-time requirements and reliability requirements. .

In addition, a metric called reliability may be 'an evaluation criterion for describing the quality of a radio link connection to satisfy a specific service level'.

In addition, a metric for service availability may be referred to as RLA (Radio Link Availability), and when the quality of experience (QoE) of the UE is expressed in terms of link quality, RLA = Pr (RLQ>). = QoE).

Where RLQ is the measured radio link quality and QoE is the QoE requirements in terms of link quality.

In addition, examples of applicable scenarios of the 5G mobile communication environment for MCSs include the following services.

-Remotely control robotic arms to realize industrial automation, or transport heavy bulk cargo through remote control of automated guided vehicles (AGVs)

-Drone remote control to provide logistics, telemedicine services, and various other public services

-Safety signals that inform hidden vehicles or forward collisions that cannot be securely exchanged between vehicles to provide autonomous driving services or captured by sensors (cameras, radars, etc.) of vehicles. Secure delivery

The above-mentioned services determine another available alternative base station link quickly according to the deterioration of the radio link (serving link) quality of the serving base station, and if the radio link quality of the serving base station is not suitable for MCS, the terminal may replace the corresponding alternative. By quickly switching to the available multilink of the base station, it should be possible to seamlessly receive the service.

Therefore, if it is determined that it is not suitable to receive MCSs by detecting the deterioration of the radio link quality of the serving base station, there is a need for a method of quickly activating another multilink and setting up an MCS bearer through the activated multilink. do.

For this reason, in order to enable reliable communication of 5G, the terminal utilizes all the radio links around itself and instructs to maximize the quality of the radio link according to the situation, thereby providing a radio link outage for providing the MCS. Should be considered as an essential factor.

In addition, in the conventional LTE / LTE-A system, the terminal controls the RLF based on a plurality of Timers.

As we saw earlier, 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 and autonomous vehicle driving. .

Through this, 5G aims to build a high-reliability system that can always receive the MCS without the terminal feels the outage of the radio link.

However, the current LTE / LTE-A system is designed to handle the recovery from the RLF fairly 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 corresponding multilink base stations. There is a problem that it is difficult to secure an available multilink base station for connection switching.

In order to solve this problem, a method for securing a plurality of base station links when a terminal accesses a network has been proposed to have multi-link base stations capable of quickly replacing the channel condition of the serving base station link.

That is, in the conventional method to be described later, 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.

However, in the conventional method, when the terminal does not always receive the MCS, a problem arises in that the terminal unnecessarily establishes multiple connections with the plurality of base stations.

Accordingly, in order to solve this problem, the present specification provides a method of establishing a multi-connection or canceling the established multi-connection only when (1) (RRC Connected) UE wants to receive MCSs as needed.

In addition, when the serving base station link quality of the terminal deteriorates to an unsuitable degree for the MCS, since the continuity of MCS provision may be impaired, (2) RRC with the base station having the highest radio link quality among the alternative base stations secured. It provides a method of activating a connection (eg SRB) to switch to a corresponding base station and quickly setting up an MCS bearer through an alternative base station having an RRC connection enabled.

In addition, the present specification provides a method for periodically tracking uplink synchronization between the terminal and the alternative base stations because the TA previously received from the alternative base stations may be shifted according to the movement of the terminal.

In addition, in the present specification, when the multi-connection is established, the serving base station and at least one alternative base station for the multi-connection allot the terminal identifier (eg, C-RNTI) to the terminal, so that too many terminal identifiers are allocated. There is a problem. That is, in the 5G mobile communication system, since the number of connections that can be secured per terminal for providing a high reliability service will be large, there may be a problem that an identifier allocated to identify the terminal for each connection is unnecessary. It provides a way to solve this.

Hereinafter, the present invention proposes (1) a network indication based multilink (or multi-connection) establishment method, and (2) a mission link service (QMCS) for providing mission critical service (MCS). Threshold definition, (3) multilink activation method and bearer setup method for MCS will be described in order.

The terms used below are defined as follows.

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 multilink.

The serving link indicates a radio link in which the terminal has a connection with a serving base station, and the multilink means a radio link in which the terminal has a connection with a base station other than the serving base station.

The meaning and related operations of the multilink will be described in more detail with reference to FIG. 18 to be described later.

Here, 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 refers to a base station to which the terminal is currently receiving service.

The alternative serving base station refers to a new serving base station that replaces the serving base station when radio link quality deterioration (or degradation) of the serving base station will be described later.

The additional alternative base station refers to an alternative base station in which multilink is additionally found by the terminal except for a preset alternative base station, which will be described later.

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.

In addition, the multilink connection (or configuration) may be represented as a multi-connection, alternative link connection and the like.

In the following description, multilink configuration and alternate link configuration are mixed as necessary.

Multilink definitions and related actions

As defined above, a multi-connection or a multilink includes a serving link and at least one multilink.

The serving link refers to a radio link between a terminal and a serving base station. In general, the serving link has both a signaling radio bearer (SRB) and a data radio bearer (DRB).

The multilink indicates a radio link between the terminal and at least one alternative base station. Only the inactive SRB is set, and the DRB is not set.

The multilink is activated by an activation indication of a terminal or a serving base station, and is a link concept having a state different from a general dormant mode, and may be an event-triggered dormant mode. have.

That is, the terminal having the multi-link of the alternate base station and the SRB inactive state sends an activation instruction directly to the alternate base station or sends an activation request to the serving base station, and continues to sleep in the multi-link until the response is received. .

In addition, the terminal may previously receive the maximum number of information of the number of multilinks that can be connected to the surrounding alternative base station through a broadcast message such as SIB from the serving base station.

In addition, when the terminal does not exceed the maximum number of multilinks that can be set, the UE may additionally set a multilink with an alternative base station that meets a specific condition (QMCS).

멀티링크 설정방법How to set up multilink

First, before looking at the method of allocating a terminal identifier proposed in the present specification, a method for setting a multilink when a terminal accesses a network, a method for setting a network indication based multilink, and setting a multilink according to a link quality value Let's look briefly at how.

The method for setting a multilink when accessing a network relates to a method for setting a multilink with a neighboring base station when a terminal accesses a network.

In this case, when the terminal accesses the network, an initial network access procedure of the terminal, a network access procedure when a mission critical service (MCS, hereinafter referred to as 'MCS') occurs in an idle state, and the like. Can be.

That is, the present invention relates to a method for configuring a multilink with an alternative base station to support MCS when the terminal accesses a network.

In addition, the method of setting up a multilink when accessing the network can be applied to both (1) when there is no need to synchronize synchronization between the terminal and the alternative base station and (2) when synchronization between the terminal and the alternative base station is required.

In this case, when synchronization is not necessary, (1) a 'small cell environment' in which a timing advance (TA) between a terminal and an alternative base station (or a small base station) is almost zero, or (2) This is the case in which new waveform-based asynchronous systems are built.

On the contrary, the method of configuring the network indication based multilink is a method for solving the problem of unnecessarily configuring the multi-connection when the terminal is not always provided with the MCS, and when providing the MCS to the RRC-connected terminal. If necessary, multiple connections can be turned on or off as needed.

The method for configuring the multilink according to the link quality value may set or release the multiple connectivity according to the change of the link quality value indicator indicating the radio link quality of the serving base station or the alternative base station. Unlike the above-described method of setting up a multilink and setting up a network indication-based multilink, the method of setting up a multilink according to a link quality value may be a service or service before the actual radio link quality of the terminal deteriorates. The alternative base station first informs the terminal of the link quality value indicator, thereby enabling the terminal to establish multiple connections before the radio link quality deteriorates.

In this way, 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, inactive (inactive) state with the alternative base station It has a connection of (multilink in inactive state).

The serving link in the active state means that the terminal establishes an active signaling radio bearer (SRB) / active data radio bearer (DRB) with the serving base station, and in the inactive multilink, the terminal configures only an alternative base station and an inactive SRB. It can mean doing.

That is, the inactive SRB may indicate a state in which the UE does not have an alternative base station and DRB configured.

In addition, through the network access, 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. .

On the other hand, the alternative base station for setting the multi-link with the terminal configures the S-GW and S1-U Bearer, but the terminal and the DRB is not set, the E-RAB is not set.

However, in this case as well, the P-GW and the S5 / S8 bearer may be set.

That is, the terminal configures at least one alternative base station and inactive SRB with respect to the MCS, but does not configure the DRB.

As with salpin, 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 in an SRB inactive mode.

That is, the general dormant mode (Dormant Mode) refers to a mode used for power saving of the RRC connected UE.

For example, 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.

In contrast, 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.

Accordingly, the SRB inactive mode may be represented as an event-triggered dormant mode.

As described above, when there are multi-tier / multi-layer base stations in the coverage of the terminal (in-coverage situation), when the terminal determines that the quality of the serving link is not enough to provide the MCS, the serving base station The MCS can be reliably and seamlessly provided by securing a radio link with another base station that can guarantee better radio link quality, that is, an alternative base station.

In addition, the following four modes may be considered according to the active or inactive states of the SRB and DRB of the multilink between the UE and the alternative base station.

1.First Mode: SRB Inactive and DRB Inactive

2. Second Mode: SRB Inactive and DRB Active

3. Third mode: SRB Active and DRB Inactive

4. Fourth Mode: SRB Active and DRB Active

In the methods proposed herein, the first mode, the second mode, and the fourth mode, that is, three cases will be considered.

Specifically, in the first mode (SRB Inactive state / DRB Inactive state), 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.

In the second mode (SRB Inactive state / DRB Active state), the RRC connection of the alternative base station is deactivated, but if there is an alternative base station link that satisfies the degraded link quality value according to the deterioration of the link quality value of the serving base station, the alternative base station By setting the DRB of the serving base station and the alternative base station is a state capable of performing simultaneous transmission.

In the second mode, an EPS bearer that satisfies the QoS for the MCS may be set, and the DRB is set.

The fourth mode (SRB Active state / DRB Active state) 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.

In the fourth mode, an EPS bearer that satisfies the QoS for the MCS may be set, and the DRB is set.

The method proposed in the present specification includes (1) a method in which a UE establishes a multilink in an SRB inactive state with an alternative base station according to a network indication, and (2) a multilink in an SRB inactive state in a DRB active state or an SRB active and DRB active state By activating, and how to quickly set up the MCS bearer.

That is, the method proposed in this specification is to secure a multi-link with an alternative base station other than the serving base station in order to continuously provide mission critical services (MCS) with high reliability to the terminal.

When the terminal detects that the radio link quality with the serving base station is not suitable to support the MCS, the terminal activates the multilink of the alternative base station having the optimal radio link quality among the alternative base stations that have already set up the multilink. By setting the MCS bearer through the corresponding alternative base station quickly (that is, switching the corresponding alternative base station to a new serving base station), it is to ensure the continuity of MCS provision to the terminal.

However, when the multi-connection is established through the above-described method, a terminal identifier (for example, C-RNTI) is allocated to each base station, and thus the terminal identifier is excessively allocated. In this case, when the terminal is not actually provided with the service through the radio link of the corresponding base station, there is a problem that the assigned terminal identifier is not actually used and wasted.

Accordingly, the present invention provides a method and apparatus for solving this problem.

Hereinafter, the terminal identifier will be described using the C-RNTI as an example. However, the present invention is not limited thereto.

자율적 C-Autonomous C- RNTIRNTI 할당 지시자를 이용한 C- C- with assignment indicator RNTIRNTI 할당방법 Assignment method

19 and 20 are flowcharts illustrating an example of a method of allocating a terminal identifier in multilink configuration proposed in the present specification.

19 and 20, in a method of forming a multilink or setting a network indication-based multilink when a network is connected, an alternative base station may autonomously allocate a C-RNTI to a terminal.

That is, in the case of a method of forming a multilink when accessing a network, when a serving base station and an alternative base station are not determined at the time of initial access of a terminal, among the neighboring base stations reported by the terminal to the serving base station, the base stations with good load conditions SRB deactivation indication information and Autonomic Allocation Indication information indicating autonomous allocation of C-RNTI may be transmitted.

In contrast, in the case of a network indication based multilink formation method, when a downlink MCS bearer is configured, among neighbor base stations reported by the UE in the process of establishing a dedicated bearer (eg, E-RAB) to the UE by the MME. SRB deactivation indication information and autonomic allocation indication (Autonomic Allocation Indication) information indicating the autonomous allocation of the C-RNTI can be transmitted to base stations with a good load.

It will be described below in detail.

19 is a flowchart illustrating an example of a method for autonomously allocating a C-RNTI when it is not necessary to synchronize synchronization between a terminal and an alternative base station.

Specifically, the serving base station transmits a load state request message to the alternative base stations (alternative base stations 1 and 2) to determine the current load state of each alternative base station (S19010).

Thereafter, the alternative base stations transmit a load state response message to the serving base station in response to the load state request (S19020).

The load state response message includes load state information indicating the current load state of the alternative base station.

The load state information may be expressed as one of high, medium, and low according to the load state of the alternative base station.

The serving base station receiving the load state information from the alternative base stations transmits a connection request message for requesting a multilink connection with the terminal to the alternative base stations (alternative base stations 1 and 2) (S19030). .

The expression of the connection request message is one example, which may be referred to in various terms such as a multi link request message, an alternative link connection request message, an alternative link securing request message.

The multilink connection request message may include an identifier for identifying a terminal (eg, a UE ID), autonomic allocation instruction (Autonomic Allocation Indication) information, signaling radio bearer (SRB) deactivate indication (Deactivate Indication) information, and the like.

The autonomous allocation indication information indicates an indicator for instructing the alternative base station to autonomously perform C-RNTI allocation.

The SRB deactivate indication information indicates an indicator indicating that the SRB state of the multilink established with the alternative base station is set to inactive (or event-triggered Dormant mode).

Thereafter, the serving base station receives a connection response message from the alternative base stations (alternative base stations 1 and 2) in response to the multilink connection request message (S19040).

The connection response message may also be referred to in other terms as described in the connection request message.

In addition, the connection response message includes information on the alternative base station.

That is, the connection response message may include result (success / failure) information on the multilink connection request, TA tracking indication information for acquiring synchronization between the terminal and the alternative base station, and TA tracking period information.

The TA tracking indication information and the TA tracking period information correspond to information necessary for acquiring synchronization when synchronization between the terminal and the alternative base station does not match due to the movement of the terminal.

Subsequently, the serving base station informs the matters related to the multilink connection establishment, that is, the alternative base stations (alternative base station 1 and 2) through step S19040 to inform that the multilink is established with the alternative base stations (alternative base stations 1 and 2). In operation S19050, an RRC connection reconfiguration message including information received from the mobile station is transmitted to the terminal.

The RRC connection reconfiguration message may further include radio bearer QoS, session management request information, EPS RB ID information, and the like for notifying that the MCS bearer is configured.

Thereafter, the terminal transmits an RRC Connection Reconfiguration Complete message indicating that the multi-link connection establishment for the alternative base stations (alternative base stations 1 and 2) has been completed to the serving base station (S19060).

As shown in FIG. 19, the serving base station continuously maintains the list of alternative base stations and may update the corresponding list as necessary.

The terminal may periodically measure the DL signal quality for the serving base station and the alternative base station.

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 by the serving base station to the terminal when establishing a multilink with the alternative base station.

Thereafter, the terminal notifies the serving base station when the radio link signal quality of the serving base station falls below a threshold value (QMCS), that is, lower than the QMCS value (S19070).

Specifically, 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.

As a result of the check, when the radio link quality of the serving base station is smaller than the QMCS value, the terminal transmits radio link quality worsening (RLQD) indication information to the serving base station (S19070).

Here, 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.

Here, 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.

Subsequently, the terminal selects all of the alternative base stations (or alternative base stations 1 and 2) 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 base stations configured with the multi-link. In step S19080, a link activation request message for requesting multi-link activation is transmitted, and a link activation response message is received in response thereto.

The link activation request message includes UE identifier information (UE ID), load query request indication information for requesting a load status of an alternative base station, and request for C-RNTI allocation. It may include a C-RNTI allocation request indicator.

The link activation response message may include a UE ID, information indicating a load state of an alternative base station.

In each of the alternative base stations, the load state may be expressed as high / medium / low.

Thereafter, the terminal determines or selects an optimal alternative base station (alternative base station 1) to replace the serving base station based on the received link activation response message.

Thereafter, the terminal transmits a link activation confirmation message including information necessary for activation of a multilink connection with the terminal and quick bearer setup to the determined alternative base station (alternative base station 1) (S19090).

Subsequently, the alternative serving base station (candidate base station 2) that receives the link activation confirmation message (candidate base station 2) has a UE ID, UE context information, C-RNTI, and signaling radio bearer (SRB) for identifying the terminal. In step S19100, an RRC connection activation message including deactivate indication information is transmitted to the terminal.

Through the above method, the alternative base stations for which the SRB is activated allocate the C-RNTI to the terminal, and the alternative base station for which the SRB is not activated does not allocate the C-RNTI to the user equipment. Can be prevented from being assigned.

The steps described in FIG. 19 may consist of only some steps or other steps may be added in addition to the steps described in FIG. 19 so that the alternative base stations autonomously perform C-RNTI allocation to the terminal.

20 is a flowchart illustrating an example of a method for autonomously allocating a C-RNTI when it is necessary to synchronize synchronization between a terminal and an alternative base station.

First, since steps S20010 to S20060 are the same as steps S19010 to S19060 of FIG. 19, description thereof will be omitted, and in FIG. 20, only the parts different from those of FIG. 19 will be described in detail. do.

FIG. 20 is a diagram illustrating a multilink configuration method when a terminal needs to synchronize with an alternative base station. The terminal is assigned a dedicated random access preamble allocated from each alternative base station through an RRC connection reconfiguration message. , And performs a random access procedure with each alternative base station.

That is, the terminal receives TA (Timing Advance) information from the alternative base station, but since the TA may be out of place with the alternative base stations to which the multi-link of the Inactive SRB is set according to the movement of the terminal, for this purpose, periodically tracking uplink synchronization This is to make it trackable.

To this end, each alternative base station includes indication information indicating periodic TA tacking in the random access response and period information for the TA tracking and transmits it to the terminal.

Accordingly, 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.

A more detailed description will be made with reference to FIG. 20.

Specifically, after step S20040, the serving base station transmits an RRC connection reconfiguration message including a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2) to the terminal. In operation S20050, the terminal transmits an RRC connection reconfiguration complete message to the serving base station in response to the operation (S20060).

Thereafter, the terminal performs an RACH procedure for synchronizing uplink synchronization with each alternative base station (alternative base station 1 and 2) (S20070, S20080).

That is, the terminal transmits a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2) through the PRACH (S20070).

The terminal receives a random access response including periodic TA tracking indication information and TA tracking period information associated with each alternative base station from each alternative base station (S20080).

Hereinafter, since steps S20090 to S20120 are the same as those of steps S19070 to S19100 of FIG. 19, description thereof will be omitted.

The steps described in FIG. 20 may consist of only some steps or other steps may be added in addition to the steps described in FIG. 20 so that the alternative base stations autonomously perform C-RNTI allocation to the terminal when it is necessary to synchronize. have.

C-C- RNTIRNTI 할당연기 지시자를 이용한 C- C- using the allotment indicator RNTIRNTI 할당 방법 Assignment method

21 and 22 are flowcharts illustrating still another example of a method for allocating a terminal identifier in multilink configuration proposed in the present specification.

21 and 22, in a method of forming a multilink or a network indication-based multilink in a network connection, the alternative base station delays the allocation of the C-RNTI, thereby degrading the radio link quality of the serving base station. Accordingly, at the time of activating a specific alternative base station, the C-RNTI may be allocated from the specific alternative base station.

That is, in the method of forming a multilink when accessing a network, in a situation where a serving base station and an alternative base station are determined at the time of initial access of a terminal, the serving base station is selected from base stations to which SRB deactivation indication information is transmitted due to good load among neighboring base stations. C-RNTI Allocation Defer Indication information indicating a delay of C-RNTI allocation may be received.

In contrast, in the network indication-based multilink formation method, when the downlink MCS bearer is configured, the serving base station is a neighbor base station reported by the terminal in the process of establishing a dedicated bearer (eg, E-RAB) to the terminal by the MME. Among them, C-RNTI Allocation Defer Indication information indicating delay of C-RNTI allocation may be transmitted from base stations to which SRB deactivation indication information is transmitted due to a good load state.

It will be described below in detail.

21 is a flowchart illustrating an example of a method of delaying C-RNTI allocation when it is not necessary to synchronize synchronization between a terminal and an alternative base station.

Specifically, the serving base station transmits a load state request message to the alternate base stations (alternative base stations 1 and 2) to determine the current load state of each alternate base station (S21010).

Thereafter, the alternative base stations transmit a load state response message to the serving base station in response to the load state request (S21020).

The serving base station receiving the load status information from the alternative base stations transmits a connection request message for requesting a multilink connection with the terminal to the alternative base stations (alternative base stations 1 and 2) (S21030). .

The expression of the 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 secure request message.

The multilink connection request message may include an identifier (eg, UE ID) for identifying a terminal, signaling radio bearer (SRB) deactivate indication information, and the like.

Thereafter, the serving base station receives a connection response message from the alternative base stations (alternative base stations 1 and 2) in response to the multilink connection request message (S21040).

In addition, the response message includes C-RNTI Allocation Defer Indication (C-RNTI Allocation Defer Indication) information indicating a delay of C-RNTI allocation, result (success / failure) information for the multilink connection request, and synchronization between the UE and the alternative base station. TA tracking indication information, TA tracking period information, and the like for obtaining the information may be included.

The C-RNTI allocation delay indication information is an indicator indicating that the alternative base stations will postpone allocation of the C-RNTI.

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.

Thereafter, the serving base station transmits an RRC connection reconfiguration message to the terminal in order to inform the matters related to the multilink connection establishment, that is, the multi-link is established with the alternative base stations (alternative base stations 1 and 2) (S21050). ).

The RRC connection reconfiguration message may include delay information indicating whether the alternative base stations have delayed the C-RNTI allocation, information of alternative base stations that have delayed the allocation of the C-RNTI, the TA tracking indication information, TA tracking period information, and the like. It may include.

Thereafter, the terminal transmits an RRC Connection Reconfiguration Complete message to inform the serving base station that the multilink connection establishment for the alternative base stations (alternative base stations 1 and 2) has been completed (S21060).

As illustrated in FIG. 21, the serving base station continuously maintains a list of alternative base stations and may update the corresponding list as necessary.

Since steps S21070 to S21100 are the same as steps S19070 to S19100 of FIG. 19, description thereof will be omitted.

The steps described in FIG. 21 may consist of only some steps for allocating a C-RNTI when the alternative base stations activate the SRB with the UE, or other steps may be added in addition to the steps described in FIG. 21.

22 is a flowchart illustrating an example of a method of delaying C-RNTI allocation when it is necessary to synchronize synchronization between a terminal and an alternative base station.

First, since steps S22010 to S22060 are the same as those of steps S21010 to S21060 of FIG. 21, description thereof will be omitted. In FIG. 22, only the parts different from those of FIG. 21 will be described in detail. do.

21 illustrates a method for configuring a multilink when a terminal needs to synchronize with an alternate base station, and the terminal is assigned a dedicated random access preamble allocated from each alternate base station through an RRC connection reconfiguration message. , And performs a random access procedure with each alternative base station.

This will be described in more detail with reference to FIG. 22.

Specifically, after step S22040, the serving base station transmits an RRC connection reconfiguration message including a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2) to the terminal. In operation S22050, the terminal transmits an RRC connection reconfiguration complete message to the serving base station in response to the operation (S22060).

Thereafter, the terminal performs an RACH procedure for synchronizing uplink synchronization with each alternative base station (alternative base station 1 and 2) (S22070, S22080).

That is, the terminal transmits a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2) through the PRACH (S22070).

The terminal receives a random access response including periodic TA tracking indication information and TA tracking period information associated with each alternative base station from each alternative base station (S22080).

Hereinafter, since steps S22090 to S22120 are the same as those of steps S19070 to S19100 of FIG. 19, description thereof will be omitted.

The steps described in FIG. 22 may consist of only some steps for allocating C-RNTI when the alternative base stations activate SRB with the terminal when it is necessary to synchronize or add other steps in addition to the steps described in FIG. 22 above. Can be.

C-C- RNTIRNTI 회수 지시자 및 C- Recovery indicator and C- RNTIRNTI 유효 타이머를 이용한 C- C- with valid timer RNTIRNTI 할당 방법 Assignment method

23 and 24 are flowcharts illustrating still another example of a method for allocating a terminal identifier in multilink configuration proposed in the present specification.

Referring to FIG. 23 and FIG. 24, when the SRB is not activated in the method of forming a multilink or a network indication-based multilink during network access, the CB-RNTI allocated to the UE may be recovered. .

23 is a flowchart illustrating an example of a method of recovering C-RNTI allocated to a terminal by an alternative base station when it is not necessary to synchronize synchronization between the terminal and the alternative base station.

First, since step S23010 and step S23020 are the same as step S19010 and step S19020 of FIG. 19, description thereof will be omitted.

Subsequently, the serving base station receiving the load state information from the alternative base stations transmits a connection request message for requesting a multilink connection with the terminal to the alternative base stations (alternative base stations 1 and 2) ( S23030).

The multilink connection request message includes an identifier (eg, UE ID) for identifying a terminal, C-RNTI retrieval indication information, signaling radio bearer (SRB) deactivation indication information, and the like. can do.

The C-RNTI recovery indication information is the number of allocated C-RNTI and / or release of RRC connection when the alternative base station allocates the C-RNTI to the terminal and the SRB of the alternative base station is not activated during the C-RNTI valid time. Indicates an indicator indicating.

Thereafter, the serving base station receives a connection response message from the alternative base stations (alternative base stations 1 and 2) in response to the multilink connection request message (S23040).

The connection response message is a result of acquiring (success / failure) information on a multilink connection request, a C-RNTI validity timer indicating a valid time of the C-RNTI, a C-RNTI of an alternative base station, and obtaining synchronization between a terminal and an alternative base station. TA tracking indication information, TA tracking period information, and the like may be included.

In this case, the alternative base stations (alternative base stations 1 and 2) operate the C-RNTI validity timer while transmitting the C-RNTI to the terminal.

Subsequently, the serving base station informs the matters related to the multilink connection establishment, that is, the alternative base stations (alternative base station 1 and 2) through step S23040 to inform that the multilink is established with the alternative base stations (alternative base stations 1 and 2). In operation S23050, an RRC connection reconfiguration message including information received from the SRC is transmitted to the terminal.

Thereafter, the terminal transmits an RRC Connection Reconfiguration Complete message indicating that the multilink connection configuration for the alternative base stations (alternative base stations 1 and 2) has been completed to the serving base station (S23060).

As shown in FIG. 23, the serving base station continuously maintains the list of alternative base stations and may update the corresponding list as necessary.

Subsequently, the alternative base station (alternative base station 1) whose C-RNTI validity timer has expired sends a multi-connection release request message to the serving base station in order to release the number of C-RNTIs allocated to the terminal and to release the RRC connection of the SRB inactive state. It transmits (S23070).

The multi-connection teardown request message may include a number of C-RNTIs and a UE ID indicating a terminal to release the RRC connection.

The serving base station receiving the multi-connection release request message transmits a multi-connection release response message to the alternative base station 1 in response thereto, and the alternative base station 1 performs the number of C-RNTIs allocated to the terminal and the RRC connection. It is released (S23080).

Thereafter, the serving base station transmits an RRC connection reconfiguration message to the terminal to inform the number of C-RNTIs of the alternative base station 1 and the release of the RRC connection (S23090).

In this case, the RRC connection reconfiguration message may include information of the recovered C-RNTI, and information of the alternative base station from which the RRC connection is released.

Thereafter, the terminal transmits an RRC connection reconfiguration complete message to the serving base station in response to the RRC connection reconfiguration message (S23100).

Through such a method, the alternative base stations may recover the C-RNTI allocated to the terminal and allocate the C-RNTI to another terminal, thereby preventing excessive allocation of the C-RNTI.

In another embodiment of the present invention, the alternative base station whose C-RNTI validity timer has expired is allocated through the step (S23070) and the step (S23080) without releasing the RRC connection of the SRB deactivation state with the terminal through the allocated C Only -RNTI can be recovered.

In this case, the UE may be assigned C-RNTI by requesting allocation of C-RNTI while activating an SRB and an SRB which has recovered the C-RNTI.

In addition, the value of the C-RNTI valid timer may vary for each alternative base station according to the load state of the alternative base stations. For example, an alternate base station with a good load may transmit a C-RNTI valid timer having a long value, and an alternate base station with a poor load may transmit a C-RNTI valid timer having a short value.

The steps described in FIG. 23 may consist of only some steps to recover the C-RNTI allocated to the UE by the alternative base stations, or other steps may be added in addition to the steps described in FIG. 23.

24 is a flowchart illustrating an example of a method of recovering C-RNTI allocated to a terminal by an alternative base station when it is necessary to synchronize synchronization between the terminal and the alternative base station.

First, since step S24010 and step S24030 are the same as step S22010 and step S22030 of FIG. 22, description thereof will be omitted.

Thereafter, 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 (S24040).

The connection response message may include result (success / failure) information on a multilink connection request, a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2), and the like.

Subsequently, the serving base station determines information related to the multilink connection establishment, that is, information of the alternate base stations and the dedicated random access preamble to inform that the multi-link is established with the alternative base stations (alternative base stations 1 and 2). An RRC connection reconfiguration message including a message is transmitted to the terminal (S24050).

Thereafter, the terminal transmits an RRC Connection Reconfiguration Complete message indicating that the multilink connection configuration for the alternative base stations (alternative base stations 1 and 2) has been completed to the serving base station (S24060).

Thereafter, the terminal performs an RACH procedure for synchronizing uplink synchronization with each alternative base station (alternative base station 1 and 2) (S24070, S24080).

That is, the terminal transmits a dedicated random access preamble allocated from each alternative base station (alternative base stations 1 and 2) to each alternative base station through the PRACH (S24070).

The mobile station provides C-RNTI valid C-RNTI indicating a valid time of C-RNTI, C-RNTI of each alternative base station, periodic TA tracking indication information related to each alternative base station, and TA tracking period information from each alternative base station. A random access response is received (S24080).

As illustrated in FIG. 24, the serving base station continuously maintains a list of alternative base stations and may update the corresponding list as necessary.

Hereinafter, since steps S24090 to S24120 are the same as those of steps S23070 to S23100 of FIG. 23, description thereof will be omitted.

The steps described in FIG. 24 may consist of only some steps or other steps in addition to the steps described in FIG. 24 to recover the C-RNTI allocated to the terminal by the alternative base stations when it is necessary to synchronize. .

25 to 28, in the method for configuring the multilink based on the radio link quality value indicator, the alternative base station autonomously allocates the C-RNTI or the alternative base station delays the allocation of the C-RNTI. When the SRB is activated or the SRB remains in an inactive state, C-RNTI can be allocated to the terminal when the DRB is activated.

Thereafter, the terminal may request allocation of the C-RNTI while requesting the serving base station to activate the SRB of the alternative base station according to the radio link quality value.

In this case, the C-RNTI allocated to the terminal by the alternative base station according to the change of the radio link quality value indicator (for example, Packet Error Rate (PER)) may be classified as follows.

1) When a serving base station performs line switching to the alternative base station because there is an alternative base station that can replace the link quality value of the serving base station according to the link quality value change indicating the link quality of the serving base station, a new serving C-RNTI of alternate base station to act as base station

2) According to the change of the link quality value of the serving base station, there is an alternative base station that can replace the link quality value of the serving base station, or there is an alternative base station that can supplement the link quality value of the serving base station When the serving base station and the alternate base station performs simultaneous transmission, for link quality degradation of the serving base station,

If there is no alternative base station with better link quality than the serving base station, the C-RNTI of the alternative base station to be further activated;

If there is an alternative base station with better link quality than the serving base station, the C-RNTI of the alternative base station to perform the new serving base station role and the C-RNTI of the alternative base station to be further activated.

3) If there is another alternative base station capable of substituting the link quality value to be degraded by the alternative base station and performing simultaneous transmission, the link quality deterioration of the alternative base station is activated. If there is an alternative base station with better link quality than the alternative base station, the C-RNTI of the alternative base station

It will be described below in detail.

FIG. 25 is a flowchart illustrating an example of a method for autonomously allocating a C-RNTI when a terminal directly requests a multi-link connection to an alternative base station based on a radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S25010). .

In this case, the radio link quality report message may include radio link quality change indication information, which is an indicator indicating that a change in the radio link quality of the serving base station is detected.

Thereafter, the terminal transmits an RRC connection establishment request message to an alternative base station 2 in order to establish a multi link with an adjacent base station (alternative base station 2) (S25020).

The RRC connection establishment request message includes a UE ID for identifying the terminal, multilink indication information which is an indicator for indicating multilink establishment for MCS, and an autonomic allocation indication indicating autonomous allocation of C-RNTI. Information, and SRB deactivation indication information.

The alternative base station 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message in response thereto (S25030).

The RRC connection establishment result message may include accept / fail indication information indicating the multilink establishment result.

Subsequently, the alternative base station 2 has an RRC connection including UE ID for identifying the UE to the base station and acceptance / failure indication information indicating whether to accept the multi-link configuration so as to inform the serving base station whether to establish the multi-link. The setting result indication message is transmitted (S25040).

Then, when the terminal detects that the radio link quality of the serving base station deteriorates, the terminal transmits a multi-link activation message requesting activation of the radio link of the alternative base station to the serving base station (S25050).

In this case, the multi-link activation message may include a C-RNTI allocation indicator for requesting the assignment of the C-RNTI of the alternative base station.

The serving base station receiving the multi-link activation message transmits a link activation request message for requesting activation of a multilink connection with the terminal to an alternative base station (alternative base station 1) having a good load condition among the alternative base stations (S25060). .

In response, the alternative base station 1 transmits a link activation response message including the C-RNTI of the alternative base station to the serving base station, and activates a multilink connection with the terminal (S25070). That is, it activates an inactive SRB.

Thereafter, the serving base station transmits an RRC connection reconfiguration message to inform the terminal that the SRB is activated (S25080). The RRC connection reconfiguration message may include information of the allocated C-RNTI and the alternative base station to which the C-RNTI is allocated.

The steps described in FIG. 25 may consist of only some steps or other steps may be added in addition to the steps described in FIG. 25 so that the alternative base stations autonomously perform C-RNTI allocation to the terminal.

FIG. 26 is a flowchart illustrating an example of a method for autonomously allocating a C-RNTI when a base station requests a multi-link connection to an alternative base station based on a radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S26010). .

The serving base station that has received a change in the radio link quality value of the serving base station from the terminal transmits an RRC connection establishment request message to an alternative base station 2 to establish a multi link with an adjacent base station (alternative base station 2) (S26020). .

The RRC connection request message includes a UE ID for identifying the UE, autonomic allocation indication information indicating autonomous allocation of C-RNTI, and a multilink indication indicating an indicator for multilink setting for MCS. Information, and SRB deactivation indication information.

The alternative base station 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message in response thereto (S26030).

In this case, the RRC connection establishment result message may include accept / fail indication information indicating the multilink establishment result.

Subsequently, the serving base station transmits an RRC connection establishment result indication message including acceptance / failure indication information indicating whether the multi-link establishment is accepted or not to inform whether the multi-link is established between the alternative base station 2 and the terminal. (S26040).

Hereinafter, since steps S26050 to S26080 are the same as those of steps S25050 to S25080 of FIG. 25, description thereof will be omitted.

The steps described in FIG. 26 may consist of only some steps or other steps in addition to the steps described in FIG. 26 so that the alternative base stations autonomously perform C-RNTI allocation to the terminal.

FIG. 27 is a flowchart illustrating an example of a method of delaying allocation of a C-RNTI by a substitute base station when a terminal directly requests a multi-link connection to an alternative base station based on a radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S27010). .

Thereafter, the terminal transmits an RRC connection establishment request message to an alternative base station 2 in order to establish a multi link with an adjacent base station (alternative base station 2) (S27020).

The RRC connection establishment request message may include a UE ID for identifying the terminal, multi link indication information, which is an indicator for indicating a multi link setting for MCS, and SRB deactivation indication information.

The alternative BS 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message in response thereto (S27030).

The RRC connection establishment result message may include acceptance / failure indication information indicating the multi-link establishment result and C-RNTI allocation delay indication information, which is an indicator indicating the C-RNTI allocation delay of the alternative BS 2.

The terminal may know that C-RNTI allocation of the alternative base station 2 is delayed by receiving the RRC connection establishment result message.

Subsequently, the alternative base station 2 has an RRC connection including UE ID for identifying the UE to the base station and acceptance / failure indication information indicating whether to accept the multi-link configuration so as to inform the serving base station whether to establish the multi-link. The setting result indication message is transmitted (S27040).

Hereinafter, since steps S27050 to S27080 are the same as those of steps S25050 to S25080 of FIG. 25, description thereof will be omitted.

The steps described in FIG. 27 may consist of only some steps for allocating a C-RNTI when the alternative base stations activate the SRB with the UE, or other steps may be added in addition to the steps described in FIG. 27.

28 is a flowchart illustrating an example of a method of delaying allocation of a C-RNTI when a serving base station requests a multi-link connection to an alternative base station based on a radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S28010). .

In this case, the radio link quality report message may include radio link quality change indication information that is an indicator indicating that a change in the radio link quality of the serving base station is detected.

The serving base station that has received a change in the radio link quality value of the serving base station from the terminal transmits an RRC connection establishment request message to an alternative base station 2 to establish a multi link with an adjacent base station (alternative base station 2) (S28020). .

The RRC connection request message may include a UE ID for identifying the terminal, multi link indication information that is an indicator for indicating a multi link setting for MCS, and SRB deactivation indication information.

The alternative base station 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message in response (S28030).

In this case, the RRC connection establishment result message may include the acceptance / failure indication information indicating the multi-link establishment result and the C-RNTI allocation delay indication information, which is an indicator indicating the C-RNTI allocation delay of the alternative BS 2.

Subsequently, the serving base station accepts / fails indication information indicating whether the multi-link configuration is accepted by the terminal and informs whether the multi-link is established between the alternative base station 2 and the terminal and the alternative base station 2 delays the C-RNTI allocation. The RRC connection establishment result indication message including the C-RNTI allocation delay information indicating whether or not it is transmitted is transmitted (S28040).

The terminal receiving the connection establishment result indication message may recognize that the multi-link is established with the alternative base station 2, but the allocation of the C-RNTI is delayed.

Hereinafter, since steps S28050 to S28080 are the same as those of steps S25050 to S25080 of FIG. 25, description thereof will be omitted.

The steps described in FIG. 28 may consist of only some steps for allocating the C-RNTI when the alternative base stations activate the SRB with the UE, or other steps may be added in addition to the steps described in FIG. 28.

29 and 30, when the multi-link is set based on the radio link quality value indicator, the alternative base station can transmit the valid time of the C-RNTI allocated to the terminal, the valid time of the C-RNTI If expired, the C-RNTI allocated to the terminal may be recovered.

It will be described below in detail.

29 is a flowchart illustrating an example of a method for recovering a C-RNTI when a terminal directly requests a multi-link connection to an alternative base station based on a radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S29010). .

Thereafter, the terminal transmits an RRC connection establishment request message to the alternative base station 2 in order to establish a multi link with an adjacent base station (alternative base station 2) (S29020).

The RRC connection establishment request message includes a UE ID for identifying the UE, multi-link indication information which is an indicator for indicating multi-link setting for MCS, C-RNTI retrieval indication information, and SRB deactivation indication. May contain information.

The C-RNTI recovery indication information indicates that the number of allocated C-RNTIs and / or RRC connections when the SRB of the alternative base station is not activated during the C-RNTI valid time after the alternative base station 2 allocates the C-RNTI to the UE. Indicates an indicator indicating release.

The alternative base station 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message to the terminal in response (S29030).

The RRC connection establishment result message may include accept / fail indication information indicating the multi-link establishment result, a C-RNTI valid timer indicating the valid time of the C-RNTI and the C-RNTI of the alternative base station 2, and the like.

In this case, the alternative base station 2 may operate the C-RNTI validity timer while allocating the C-RNTI to the terminal.

Subsequently, the alternative base station 2 has an RRC connection including UE ID for identifying the UE to the base station and acceptance / failure indication information indicating whether to accept the multi-link configuration so as to inform the serving base station whether to establish the multi-link. The setting result indication message is transmitted (S29040).

Then, when the terminal detects that the radio link quality of the serving base station deteriorates, the terminal transmits a multi-link activation message requesting activation of the radio link of the alternative base station to the serving base station (S29050).

The serving base station receiving the multi-link activation message transmits a link activation request message for requesting activation of a multilink connection with the terminal to an alternative base station (alternative base station 1) having a good load condition among the alternative base stations (S29060). .

The alternative base station 1 transmits a link activation response message to the serving base station in response to this, and activates a multilink connection with the terminal (S29070). That is, it activates an inactive SRB.

Thereafter, the serving base station transmits an RRC connection reconfiguration message to inform the terminal that the SRB is activated (S29080). The RRC connection reconfiguration message may include information of an alternative base station.

In this case, since the SRB of the alternative base station 2 is not activated, the alternative base station 2 may release the number of C-RNTIs allocated to the UE and release the RRC connection after the C-RNTI validity timer expires.

Through this method, the alternative base station 2 may allocate the recovered C-RNTI to other terminals, thereby preventing excessive allocation of the C-RNTI and efficiently allocating the C-RNTI.

In another embodiment of the present invention, the alternative base station 2 whose C-RNTI validity timer has expired may recover only the allocated C-RNTI without releasing the RRC connection of the SRB deactivation state with the terminal.

The steps described in FIG. 29 may consist of only some steps to recover the C-RNTI allocated to the UE by the alternative base stations, or other steps may be added in addition to the steps described in FIG. 29.

30 is a flowchart illustrating an example of a method of recovering C-RNTI when a base station requests a multi-link connection to an alternative base station based on a radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S30010). .

The serving base station that has received a change in the radio link quality value of the serving base station from the terminal transmits an RRC connection establishment request message to an alternative base station 2 to establish a multi link with an adjacent base station (alternative base station 2) (S30020). .

The RRC connection establishment request message includes a UE ID for identifying the UE, -RNTI Retrieval Indication information, multi-link indication information that is an indicator for indicating multi-link establishment for MCS, and an SRB deactivation indication. May contain information.

The alternative base station 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message in response (S30030).

Subsequently, the serving base station accepts / fails indication information indicating whether the multi-link configuration is accepted by the terminal to inform whether the multi-link is established between the alternative base station 2 and the terminal, the C-RNTI of the alternative base station 2, and the alternative base station. The RRC connection establishment result indicating message including the information is transmitted (S30040).

Hereinafter, since steps S30050 to S30080 are the same as those of steps S29050 to S29080 of FIG. 29, description thereof will be omitted.

The steps described in FIG. 30 may consist of only some steps to recover the C-RNTI allocated to the UE by the alternative base stations, or other steps may be added in addition to the steps described in FIG. 30.

31 and 34, a terminal identifier that can be used in common by a serving base station and an alternative base station in a multi link setup method, a network indication based multi link setup method, or a link quality indicator based multi link setup method for network access The common terminal identifier may be generated and assigned to the terminal.

Specifically, when the serving base station establishes a multi-link with the terminal, the serving base station generates a common terminal identifier (eg, C-RNTI) which is a terminal identifier commonly used by the serving base station and at least one alternative base station for the terminal. By transmitting this, the at least one alternative base station can use the terminal identifier generated by the serving base station for the purpose of identifying the terminal.

In this case, the common BS identifier generated by the serving BS to identify the at least one alternative BS and the MS is defined as MC-RNTI, and the MC-RNTI is generated by a method of Equation 1 or 2 below. Can be.

When generating the MC-RNTI through Equation 1, at least two of a UE ID for identifying the terminal, a C-RNTI assigned to the terminal by the serving base station, and eNB IDs for identifying the at least one alternative base station. Can be created through XOR operation through.

In this case, since the UE ID (or IMSI) is a 15-bit value, in order to generate a 16-bit MC-RNTI, the UE ID (or IMSI) may be converted into a UE ID padded with a leftmost or rightmost pad, and used as the eNB. IDs may be used by truncating Leftmost or Rightmost with 16 bits.

When generating the MC-RNTI through Equation 2, one-way hash function through at least two of a UE ID for identifying the terminal, a C-RNTI assigned by the serving base station to the terminal, and a C-RNTI update counter. Can be generated via

In this case, the C-RNTI Update Counter is a Counter value that increases every time the connection is established / released to the at least one alternative base station, 16-bit MC-RNTI since the UE ID (or IMSI) is a 15-bit value as shown in Equation 1 In order to generate 0, 0 may be converted into a UE ID padded to the left (Leftmost) or the right (Rightmost).

Table 4 below shows an example of use of the MC-RNTI value and associated logical and transport channels.

RNTIRNTI	UsageUsage	Transport ChannelTransport Channel	Logical ChannelLogical Channel
MC-RNTIMC-RNTI	Dynamically Scheduled Unicast TransmissionDynamically Scheduled Unicast Transmission	UL-SCHUL-SCH	DCCH, DTCHDCCH, DTCH
MC-RNTIMC-RNTI	Dynamically Scheduled Unicast TransmissionDynamically Scheduled Unicast Transmission	DL-SCHDL-SCH	CCCH, DCCH, DTCHCCCH, DCCH, DTCH

The MC-RNTI is a method for forming a multilink when a network is connected to a base station that wants to form a multilink due to a good load condition among neighboring base stations reported by the terminal when a serving base station and an alternative base station are determined during initial access. In the method for forming a network indication-based multilink, when the downlink MCS Bearer is configured to the UE, the MME reported by the UE while the dedicated bearer (eg, E-RAB) is established to the UE by the MME. The load condition of the neighboring base stations is good and can be transmitted to the base stations to form a multi-link.

It will be described below in detail.

FIG. 31 shows an example of a method for generating and allocating the MC-RNTI in a method of forming a multilink or a network indication based multilink when a network connection is not necessary.

Specifically, the serving base station transmits a load state request message to the alternative base stations (alternative base stations 1 and 2) to determine the current load state of each alternative base station (S31010).

Thereafter, the alternative base stations transmit a load state response message to the serving base station in response to the load state request (S31020).

The serving base station receiving the load status information from the alternative base stations generates the MC-RNTI through Equation 1 or Equation 2, and multi-links the UE with the alternative base stations (alternative base stations 1 and 2). A connection request message for requesting a request is transmitted (S31030).

The multilink connection request message may include an identifier (eg, a UE ID) for identifying a terminal, the MC-RNTI, signaling radio bearer (SRB) deactivate indication information, and the like.

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).

Thereafter, the serving base station receives a multi-link connection response message in response to the multi-link connection request message from the alternative base stations (alternative base stations 1 and 2) (S31040).

In addition, the multilink connection response message includes information on an alternative base station.

That is, the connection response message may include result (success / failure) information on the multilink connection request, TA tracking indication information for acquiring synchronization between the terminal and the alternative base station, TA tracking period information, and the like.

Subsequently, the serving base station transmits the information related to the multilink connection establishment, that is, the alternative base station (alternative base station 1 and 2) and the alternative base station (alternative base station 1 and 2) through step S31040 to inform that the alternative link is established. In operation S31050, an RRC connection reconfiguration message including information received from the RRC is transmitted to the terminal.

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.

Thereafter, the terminal transmits an RRC Connection Reconfiguration Complete message to inform the serving base station that the multilink connection establishment for the alternative base stations (alternative base stations 1 and 2) has been completed (S31060).

As illustrated in FIG. 31, the serving base station continuously maintains a list of alternative base stations and may update the corresponding list as necessary.

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 by the serving base station to the terminal when establishing an alternative link with the alternative base station.

Thereafter, the terminal notifies the serving base station when the radio link signal quality of the serving base station falls below a threshold value QMCS, that is, lower than the QMCS value (S31070).

As a result of the check, when the radio link quality of the serving base station is smaller than the QMCS value, the terminal transmits radio link quality worsening (RLQD) indication information to the serving base station (S31070).

Subsequently, the terminal selects all of the alternative base stations (or alternative base stations 1 and 2) present in the list (or list) of its own alternative base stations in order to select an optimal alternative base station among the alternative base stations configured with the terminal and the alternative link. In step S31080, a link activation request message for requesting replacement link activation is transmitted, and a link activation response message is received in response thereto.

The Link Activation Request message may include UE ID information and a Load Query Request Indication requesting a load status of an alternative base station.

Thereafter, the terminal transmits a link activation confirmation message including information necessary for activation of the alternate link connection with the terminal and quick bearer setup to the determined alternative base station (alternative base station 1) (S31090).

Subsequently, the alternative serving base station (candidate base station 2) that has received the link activation confirmation message (candidate base station 2) indicates a UE ID, UE context information, and signaling radio bearer (SRB) deactivation indication for identifying the mobile station. In operation S31100, an RRC connection activation message including deactivate indication information is transmitted to the terminal.

Through this method, C-RNTI can be prevented from being excessively allocated by generating and using a terminal identifier commonly used by the serving base station and the alternative base stations.

In another embodiment of the present invention, the serving base station generates the MC-RNTI, and the elements for generating the MC-RNTI and not the MC-RNTI to the alternative base stations and the terminal and the MC-RNTI By informing the method or algorithm for generating, the alternative base station and the terminal can directly generate the MC-RNTI.

In another embodiment of the present invention, the MC-RNTI is a UE ID for identifying the terminal when the MC-RNTI is generated through Equations 1 and 2 described above, and C- assigned by the serving base station to the terminal. In addition to an RNTI, eNB IDs for identifying the at least one alternative base station, and a C-RNTI Update Counter, the serving base station may generate the MC-RNTI by generating a specific RNTI for generating the MC-RNTI.

In this case, the specific RNTI may be generated based on at least one of the elements for generating the MC-RNTI or may be generated based on another element.

In addition, the serving base station may transmit the element for generating the specific RNTI and MC-RNTI to the alternative base station and the terminal to directly generate the MC-RNTI.

32 illustrates an example of a method for generating and allocating the MC-RNTI in a method of forming a multilink or a network indication-based multilink when a terminal needs to synchronize with an alternative base station. Indicates.

First, since steps S32010 to S32040 are the same as those of steps S31010 to S31040 of FIG. 31, description thereof will be omitted. In FIG. 32, only the parts different from those of FIG. 19 will be described in detail. do.

32 illustrates a method for configuring an alternative link when a 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. , And performs a random access procedure with each alternative base station.

That is, the terminal receives the TA (Timing Advance) information from the alternate base station, but since the TA may be out of place with the alternative base station in which the alternative link of the Inactive SRB is set according to the movement of the terminal, for this purpose periodically tracking uplink synchronization This is to make it trackable.

A more detailed description will be made with reference to FIG. 32.

Specifically, after step S32040, the serving base station transmits an RRC connection reconfiguration message including a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2) to the terminal. In operation S32050, the terminal transmits an RRC connection reconfiguration complete message to the serving base station in response to the terminal (S32060).

Thereafter, the terminal performs an RACH procedure for synchronizing uplink synchronization with each alternative base station (alternative base station 1 and 2) (S32070, S32080).

That is, the terminal transmits a dedicated random access preamble allocated from each alternative base station (alternative base station 1 and 2) through the PRACH (S32070).

The terminal receives a random access response including periodic TA tracking indication information and TA tracking period information associated with each alternative base station from each alternative base station (S32080).

Hereinafter, since steps S32090 to S32120 are the same as those of steps S31070 to S31100 of FIG. 31, description thereof will be omitted.

33 to 34, in the method for configuring a multilink based on a radio link quality value indicator, a serving base station generates the MC-RNTI to at least one alternative base station and / or a base station to the MC-RNTI. Can be transmitted.

33 is a flowchart illustrating an example of a method of generating and transmitting the MC-RNTI by a serving base station when a terminal directly requests a multi-link connection to an alternative base station based on a radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S33010). .

Thereafter, the terminal transmits an RRC connection establishment request message to an alternative base station 2 in order to establish a multi link with an adjacent base station (alternative base station 2) (S33020).

The alternative base station 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message to the terminal in response (S33030).

Subsequently, the alternative base station 2 has an RRC connection including UE ID for identifying the UE to the base station and acceptance / failure indication information indicating whether to accept the multi-link configuration so as to inform the serving base station whether to establish the multi-link. The setting result indication message is transmitted (S33040).

After receiving the RRC connection establishment result indication message, the serving base station generates the MC-RNTI through Equation 1 or Equation 2 and transmits the MC-RNTI to the alternative base station 2.

In addition, the serving base station transmits the MC-RNTI to the terminal by including the RRC connection reconfiguration message (S33050).

Then, when the terminal detects that the radio link quality of the serving base station deteriorates, the terminal transmits a multi-link activation message requesting activation of the radio link of the alternative base station to the serving base station (S33060).

The serving base station receiving the multi-link activation message transmits a link activation request message for requesting activation of a multilink connection with the terminal to an alternative base station (alternative base station 1) having a good load condition among the alternative base stations (S33070). .

The alternative base station 1 transmits a link activation response message to the serving base station in response to this, and activates a multilink connection with the terminal (S33080). That is, it activates an inactive SRB.

Thereafter, the serving base station transmits an RRC connection reconfiguration message to inform the terminal that the SRB is activated (S33090). It may include information of at least one alternative base station.

34 is a flowchart illustrating an example of a method for generating and transmitting the MC-RNTI by the serving base station when the base station requests a multi-link connection to an alternative base station based on the radio link quality indicator.

When the radio link quality of the serving base station is changed, the terminal measures the radio link quality of the serving base station and transmits a radio link quality report message to the serving base station to report the radio link quality of the serving base station (S34010). .

The serving base station that has received a change in the radio link quality value of the serving base station from the terminal generates the MC-RNTI through Equation 1 or Equation 2 and sets up a multi-link with an adjacent base station (alternative base station 2). In order to transmit the RRC connection establishment request message to the alternative base station 2 (S34020).

The RRC connection establishment request message may include a UE ID, the MC-RNTI, and SRB deactivation indication information for identifying the terminal.

The alternative base station 2 that has received the RRC connection establishment request message transmits an RRC connection establishment result message in response (S34030).

In this case, the RRC connection establishment result message may include a UE ID for identifying the terminal and acceptance / failure indication information indicating the multi link establishment result.

Subsequently, the serving base station RRC connection establishment result including the MC-RNTI and acceptance / fail indication information indicating whether the multi-link configuration is accepted or not in order to inform whether the multi-link is established between the alternative base station 2 and the terminal. The instruction message is transmitted (S34040).

Hereinafter, since steps S34050 to S34080 are the same as steps S33060 to S33090 of FIG. 33, description thereof will be omitted.

Through the method described with reference to FIGS. 31 to 34, the serving base station and the at least one alternative base station do not allocate a separate C-RNTI to the terminal for multi-connection configuration, and use the MC-RNTI generated by the serving base station. By using in common, excessive allocation of the C-RNTI can be prevented and the C-RNTI can be efficiently allocated.

In this case, whenever a switching of the serving base station occurs or alternate base stations are added / released, a new MC-RNTI should be generated and delivered to the alternate base stations.

Here, 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.

As shown in FIG. 35, the terminal 10 and the base station 20 include processors 3511 and 3351, memories 3512 and 3352, and RF units (transmitter and receiver, communication units 3513 and 3523).

In addition, the base station and the terminal may further include an input unit and an output unit.

The

RF units

3513 and 3523, the processors 3511 and 3351, the input unit, the output unit and the memory 3512 and 3352 are functionally connected to perform the method proposed in the present specification.

The

RF units

3513 and 3523 receive information generated from the PHY protocol (Physical Layer Protocol), transfer the received information to the Radio-Frequency Spectrum, perform filtering, amplification, and the like. Transmit with an antenna. In addition, 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 3511 and 3351 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 3512 and 3352 are connected to a processor to store protocols or parameters for performing the method proposed herein.

The processors 3511 and 3351 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 radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function.

The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

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.

Further, for convenience of description, the drawings are divided and described, but it is also possible to design a new embodiment by merging the embodiments described in each drawing. And, according to the needs of those skilled in the art, it is also within the scope of the present invention to design a computer-readable recording medium having a program recorded thereon for executing the embodiments described above.

The method proposed herein is not limited to the configuration and method of the embodiments described as described above, the embodiments may be a combination of all or part of each embodiment selectively so that various modifications can be made It may be configured.

Meanwhile, 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.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

In the wireless communication system of the present invention, the RRC connection method has been described with reference to an example applied to the 3GPP LTE / LTE-A system. However, the RRC connection method may be applied to various wireless communication systems in addition to the 3GPP LTE / LTE-A system.

Claims

In the method for allocating a terminal identifier in a wireless communication system, the method performed by the serving base station,

Sending a request message for requesting the multi-link configuration with the terminal to at least one alternative base station,

The request message includes a common terminal identifier indicating a terminal identifier commonly used by the serving base station and the at least one alternative base station to identify the terminal;

Receiving a response message from the at least one alternative base station in response to the request message; And

Transmitting the common terminal identifier to the terminal.
The method of claim 1,

Generating, by the serving base station, the common terminal identifier.
The method of claim 1,

The common terminal identifier is generated based on at least two of a terminal ID indicating the terminal, an alternate base station ID indicating the at least one alternative base station, or a C-RNTI indicating a terminal identifier assigned to the terminal by the serving base station. Way.
The method of claim 3, wherein

And when the common terminal identifier is generated based on the terminal ID, '0' is padded on the right or left side of the terminal ID.
The method of claim 3, wherein

When the common terminal identifier is generated based on the neighbor base station ID, a right or left truncated 16 bits long.
The method of claim 1,

Transmitting a load state request message for requesting a load state to the at least one neighboring base station; And

Receiving a load status response message including a current load status to the at least one neighboring base station.
The method of claim 6,

The common terminal identifier is transmitted to an alternative base station having a good current load.
In the method for allocating a terminal identifier in a wireless communication system, the method performed by the serving base station,

Sending a request message for requesting the multi-link configuration with the terminal to at least one alternative base station,

The connection request message includes autonomous allocation indication information instructing at least one alternative base station autonomous allocation of a terminal identifier for identifying the terminal; And

Receiving a response message in response to the connection request message.
The method of claim 8,

Receiving a multi-link activation message requesting activation of the multi-link from the terminal;

Transmitting a link activation request message for requesting multi-link activation with the terminal to the at least one alternative base station specific alternative base station;

Receiving a link activation response message including the terminal identifier from the specific alternative base station; And

Sending the terminal identifier to the terminal.
In the method for allocating a terminal identifier in a wireless communication system, the method performed by the serving base station,

Transmitting a request message for requesting multilink establishment with a terminal to at least one alternative base station;

Receive a response message from the at least one alternative base station in response to the request message,

The response message includes terminal identifier allocation delay indication information indicating a delay of allocation of a terminal identifier for identifying the terminal; And

And at least one of delay information indicating whether the terminal identifier allocation is delayed to the terminal or information of alternative base stations that delay the terminal identifier allocation.
The method of claim 10,

Receiving a multi-link activation message requesting activation of the multi-link from the terminal;

Transmitting a link activation request message for requesting multi-link activation with the terminal to the at least one alternative base station specific alternative base station;

Receiving a link activation response message including the terminal identifier from the specific alternative base station; And

Sending the terminal identifier to the terminal.
In the method for allocating a terminal identifier in a wireless communication system, the method performed by the serving base station,

Sending a request message for requesting the multi-link configuration with the terminal to at least one alternative base station,

The request message includes terminal identifier recovery indication information indicating the number of terminal identifiers;

Receive a response message from the at least one alternative base station in response to the request message,

The response message includes a terminal identifier validity timer indicating the terminal identifier and a valid time of the terminal identifier; And

Transmitting the terminal identifier and the terminal identifier validity timer to the terminal.
The method of claim 12,

Receiving a multi-link release request message indicating that the multilink release request and the terminal identifier have been recovered from a specific alternative base station among the at least one alternative base station;

Transmitting a multi-link release response message to the at least one alternative base station in response to the multi-link release request message; And

And transmitting, to the terminal, base station information including information of the specific base station from which the multi-link is released and the terminal identifier has been recovered.
The serving base station for allocating a terminal identifier in a wireless communication system,

Communication unit for transmitting and receiving a wireless signal with the outside; And

A processor is functionally coupled with the communication unit, wherein the processor includes:

Sending a request message requesting the multi-link configuration with the terminal to at least one alternative base station,

The request message includes a common terminal identifier indicating a terminal identifier commonly used by the serving base station and the at least one alternative base station to identify the terminal,

Receiving a response message from the at least one alternative base station in response to the request message,

And a base station controlling to transmit the common terminal identifier to the terminal.