WO2018056718A1

WO2018056718A1 - Method and apparatus for changing connection state of terminal

Info

Publication number: WO2018056718A1
Application number: PCT/KR2017/010406
Authority: WO
Inventors: 홍성표; 최우진
Original assignee: 주식회사 케이티
Priority date: 2016-09-23
Filing date: 2017-09-21
Publication date: 2018-03-29

Abstract

The present disclosure relates to a specific method for changing a connection state of a terminal and an apparatus therefor. More specifically, the present disclosure relates to technology for, when an S1 connection release event occurs in a core network, releasing an RRC connection state of a terminal which is in a light connection state or an RRC-inactive state. One embodiment provides a method for changing a connection state by a terminal, and an apparatus therefor, the method comprising the steps of: configuring a connection state of a terminal as a particular RRC state on the basis of indication information which indicates a state change to a particular RRC state and is received from an anchor base station; receiving, from the anchor base station or a serving base station, an RAN initiation paging message generated due to an S1 connection release of the terminal; transmitting an RRC connection resumption request message for a state change from the particular RRC state to an RRC connection state on the basis of the RAN initiation paging message; and when the state of the terminal is changed to the RRC connection state, receiving an RRC connection release request message from the anchor base station or the serving base station, wherein the particular RRC state is a state that is neither the RRC connection state nor the RRC idle state.

Description

Method and apparatus for changing connection state of terminal

The present disclosure relates to a specific method and apparatus for changing a connection state of a terminal. More specifically, the present invention relates to a technique for releasing an RRC connection state of a terminal when an S1 connection release event of a core network occurs for a terminal in a light connection or RRC inactive state.

As communication systems have evolved, consumers, such as businesses and individuals, have used a wide variety of wireless terminals. Mobile communication systems such as LTE (Long Term Evolution) and LTE-Advanced of the current 3GPP series are high-speed, high-capacity communication systems that can transmit and receive various data such as video and wireless data, beyond voice-oriented services. The development of technology capable of transferring large amounts of data is required.

In addition, due to an increase in terminals using machine type communication (hereinafter, referred to as "MTC" communication), data transmission and reception through a mobile communication system is rapidly increasing. Meanwhile, in case of MTC communication, it is necessary to periodically transmit and receive a small amount of data, and a low power low cost terminal may be used. Therefore, a technique for transmitting and receiving data by a plurality of terminals is required while reducing power consumption.

In particular, in the case of a terminal transmitting a small amount of data periodically or aperiodically, it is necessary to change the RRC connection state in order to transmit a small amount of data. However, in order to change the RRC connection state by the conventional method, the data transmission / reception procedure of the terminal, the base station, the base station, and the core network is very complicated.

This transmission and reception procedure causes a relatively very high data load compared to a small amount of data to be transmitted by the terminal. That is, there is a problem that unnecessary data overload occurs in the RRC connection state change procedure for transmitting a small amount of data. This problem will result in increasing the data load on the entire communication system as more terminals for periodically transmitting a small amount of data.

Therefore, according to such a change in the wireless communication environment, a study on a method and procedure for changing a specific terminal connection state capable of transmitting and receiving a small amount of data without seriously increasing the data load of the entire communication system is required. In particular, when a new RRC state is defined instead of an RRC connection and an RRC idle state, and the UE configures the connection state, the ambiguity caused by the mismatch of the connection state between the UE and the core network entity is recognized. Need to solve.

In the background described above, an embodiment proposes a terminal state change procedure when S1 connection release of a core network is triggered for a terminal configured with a specific RRC state such as a write connection state or an RRC inactive state.

In addition, an embodiment is to propose a method for solving the ambiguity of the UE connection state change in the case of changing the ECM connection state for a UE configured with a specific RRC connection state in which the RRC connection state and the ECM connection state are inconsistent.

In order to solve the above-described problems, an embodiment of the present invention provides a method for changing a connection state of a terminal, based on indication information indicating a state change to a specific RRC state received from an anchor base station, and a connection state of the terminal. A state change from a specific RRC state to an RRC connected state based on a step of configuring to a specific RRC state, receiving a RAN initiated paging message resulting from S1 disconnection of a terminal from an anchor base station or a serving base station, and a RAN initiated paging message Transmitting an RRC connection resumption request message for the RRC connection state and receiving the RRC connection release request message from the anchor base station or the serving base station, wherein the specific RRC state includes an RRC connection state and an RRC connection state; It provides a method characterized in that the state is distinct from the idle state.

Further, an embodiment of the present invention provides a method for changing a connection state of a terminal by a serving base station, receiving an RAN initiated paging request message causing S1 connection release to a terminal having a specific RRC state through an anchor base station; Transmitting a RAN initiation paging message to the terminal based on the RAN initiation paging request message, receiving an RRC connection resumption request message for changing a state from a specific RRC state to an RRC connection state from the terminal, and a terminal context from an anchor base station Receiving a response message and if the terminal is changed to the RRC connection state, and transmitting the RRC connection release request message to the terminal, a specific RRC state is a state that is separated from the RRC connection (Connection) state and the RRC idle state It provides a method characterized in that.

In addition, according to an embodiment of the present invention, a terminal for changing a connection state includes: a control unit configured to configure a connection state of a terminal to a specific RRC state based on indication information indicating a state change to a specific RRC state received from an anchor base station; A RRC connection resumption request message for changing a state from a specific RRC state to an RRC connected state based on a receiving unit receiving the RAN initiated paging message causing the S1 connection release of the terminal from the anchor base station or the serving base station; Including a transmitting unit, but when the receiving unit is changed to the RRC connection state, and further receives the RRC connection release request message from the anchor base station or the serving base station, a specific RRC state is a state that is distinguished from the RRC connection state and the RRC idle state It provides a terminal device characterized in that.

In addition, according to an embodiment, in a serving base station for changing a connection state of a terminal, a receiver for receiving a RAN initiation paging request message causing S1 connection release to a terminal configured with a specific RRC state through an anchor base station and RAN initiation Transmitting the RAN initiation paging message to the terminal based on the paging request message, and if the terminal is changed to the RRC connection state, including a transmitter for transmitting the RRC connection release request message to the terminal, the receiving unit from the anchor base station terminal response response message Receive an RRC connection resume request message for changing the state from the specific RRC state to the RRC connection state from the terminal, the specific RRC state is characterized in that the state is distinguished from the RRC connection (Connection) state and the RRC idle state It provides a serving base station apparatus.

The embodiments described above solve the ambiguity of the UE connection state change that may occur when the core network entity releases the S1 connection of the UE for a specific RRC state UE in which the ECM connection state and the RRC connection state do not match. There is.

1 is a diagram illustrating a message processing procedure according to the conventional LTE technology.

2 is a view for explaining a UE initiated Connection Resume procedure according to the prior art.

3 is a diagram illustrating an S1 connection release procedure of a terminal according to an embodiment.

4 is a diagram illustrating an operation of a terminal according to an exemplary embodiment.

5 is a diagram illustrating an operation of a serving base station according to an embodiment.

6 is a diagram for describing a terminal configuration, according to an exemplary embodiment.

7 is a diagram illustrating a configuration of a serving base station according to an embodiment.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

In the present specification, the MTC terminal may mean a terminal supporting low cost (or low complexity) or a terminal supporting coverage enhancement. In the present specification, the MTC terminal may mean a terminal supporting low cost (or low complexity) and coverage enhancement. Alternatively, in the present specification, the MTC terminal may mean a terminal defined in a specific category for supporting low cost (or low complexity) and / or coverage enhancement.

In other words, in the present specification, the MTC terminal may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category / type for performing LTE-based MTC related operations. Alternatively, in the present specification, the MTC terminal supports enhanced coverage compared to the existing LTE coverage, or supports UE category / type defined in the existing 3GPP Release-12 or lower, or newly defined Release-13 low cost (or lower power consumption). low complexity) can mean UE category / type.

The wireless communication system in the present invention is widely deployed to provide various communication services such as voice, packet data, and the like. The wireless communication system includes a user equipment (UE) and a base station (base station, BS, or eNB). In the present specification, a user terminal is a generic concept meaning a terminal in wireless communication. In addition, user equipment (UE) in WCDMA, LTE, and HSPA, as well as mobile station (MS) in GSM, user terminal (UT), and SS It should be interpreted as a concept that includes a subscriber station, a wireless device, and the like.

A base station or a cell generally refers to a station that communicates with a user terminal, and includes a Node-B, an evolved Node-B, an Sector, a Site, and a BTS. Other terms such as a base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell may be called.

In other words, in the present specification, a base station or a cell is a generic meaning indicating some areas or functions covered by a base station controller (BSC) in CDMA, a Node-B in WCDMA, an eNB or a sector (site) in LTE, and the like. It should be interpreted as, and it is meant to cover all the various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU, small cell communication range.

Since the various cells listed above have a base station for controlling each cell, the base station may be interpreted in two senses. i) the device providing the megacell, the macrocell, the microcell, the picocell, the femtocell, the small cell in relation to the wireless area, or ii) the wireless area itself. In i) all devices which provide a given wireless area are controlled by the same entity or interact with each other to cooperatively configure the wireless area to direct the base station. The eNB, RRH, antenna, RU, LPN, point, transmit / receive point, transmit point, receive point, and the like, according to the configuration of the radio region, become an embodiment of the base station. In ii), the base station may indicate the radio area itself to receive or transmit a signal from the viewpoint of the user terminal or the position of a neighboring base station.

Therefore, megacells, macrocells, microcells, picocells, femtocells, small cells, RRHs, antennas, RUs, low power nodes (LPNs), points, eNBs, transmit / receive points, transmit points, and receive points are collectively referred to as base stations. do.

In the present specification, the user terminal and the base station are two transmitting and receiving entities used to implement the technology or technical idea described in this specification in a comprehensive sense and are not limited by the terms or words specifically referred to. The user terminal and the base station are two types of uplink or downlink transmitting / receiving subjects used to implement the technology or the technical idea described in the present invention, and are used in a generic sense and are not limited by the terms or words specifically referred to. Here, the uplink (Uplink, UL, or uplink) refers to a method for transmitting and receiving data to the base station by the user terminal, the downlink (Downlink, DL, or downlink) means to transmit and receive data to the user terminal by the base station It means the way.

There is no limitation on the multiple access scheme applied to the wireless communication system. Various multiple access techniques such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, OFDM-TDMA, OFDM-CDMA Can be used. One embodiment of the present invention can be applied to resource allocation in the fields of asynchronous wireless communication evolving to LTE and LTE-advanced through GSM, WCDMA, HSPA, and synchronous wireless communication evolving to CDMA, CDMA-2000 and UMB. The present invention should not be construed as being limited or limited to a specific wireless communication field, but should be construed as including all technical fields to which the spirit of the present invention can be applied.

The uplink transmission and the downlink transmission may use a time division duplex (TDD) scheme that is transmitted using different times, or may use a frequency division duplex (FDD) scheme that is transmitted using different frequencies.

In addition, in a system such as LTE and LTE-advanced, a standard is configured by configuring uplink and downlink based on one carrier or a pair of carriers. The uplink and the downlink include a Physical Downlink Control CHannel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel (PHICH), a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control CHannel (EPDCCH), and the like. Control information is transmitted through the same control channel, and data is configured by a data channel such as a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH).

On the other hand, control information may also be transmitted using an enhanced PDCCH (EPDCCH or extended PDCCH).

In the present specification, a cell means a component carrier having a coverage of a signal transmitted from a transmission / reception point or a signal transmitted from a transmission point or a transmission / reception point, and the transmission / reception point itself. Can be.

A wireless communication system to which embodiments are applied may be a coordinated multi-point transmission / reception system (CoMP system) or a coordinated multi-antenna transmission scheme in which two or more transmission / reception points cooperate to transmit a signal. antenna transmission system), a cooperative multi-cell communication system. The CoMP system may include at least two multiple transmission / reception points and terminals.

The multiple transmit / receive point is at least one having a high transmission power or a low transmission power in a macro cell region, which is connected to an eNB or a macro cell (hereinafter referred to as an 'eNB') and wired controlled by an optical cable or an optical fiber to an eNB. May be RRH.

In the following, downlink refers to a communication or communication path from a multiple transmission / reception point to a terminal, and uplink refers to a communication or communication path from a terminal to multiple transmission / reception points. In downlink, a transmitter may be part of multiple transmission / reception points, 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 multiple transmission / reception points.

Hereinafter, a situation in which a signal is transmitted and received through a channel such as a PUCCH, a PUSCH, a PDCCH, an EPDCCH, and a PDSCH may be described in the form of 'sending and receiving a PUCCH, a PUSCH, a PDCCH, an EPDCCH, and a PDSCH.'

In addition, hereinafter, a description of transmitting or receiving a PDCCH or transmitting or receiving a signal through the PDCCH may be used as a meaning including transmitting or receiving an EPDCCH or transmitting or receiving a signal through the EPDCCH.

That is, the physical downlink control channel described below may mean PDCCH or EPDCCH, and may also be used to include both PDCCH and EPDCCH.

In addition, for convenience of description, the EPDCCH, which is an embodiment of the present invention, may be applied to the portion described as the PDCCH, and the EPDCCH may be applied to the portion described as the EPDCCH as an embodiment of the present invention.

Meanwhile, high layer signaling described below includes RRC signaling for transmitting RRC information including an RRC parameter.

The eNB performs downlink transmission to the terminals. The eNB includes downlink control information and an uplink data channel (eg, a physical downlink shared channel (PDSCH), which is a primary physical channel for unicast transmission, and scheduling required to receive the PDSCH. For example, a physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission on a physical uplink shared channel (PUSCH) may be transmitted. Hereinafter, the transmission and reception of signals through each channel will be described in the form of transmission and reception of the corresponding channel.

단말의 연결 상태 천이 절차Connection state transition procedure of terminal

In the conventional mobile communication technology, the terminal and the network state are divided into a terminal idle state and a connected state. The terminal and the network state are consistent. For example, states in the wireless network (E-UTRAN) and the core network (for example, the RRC state and the ECM state) coincide. That is, when the UE transitions to the RRC-IDLE state, the UE enters the ECM-IDLE state. When the UE transitions to the RRC-CONNECTED state, the UE enters the ECM-CONNECTED state. According to the terminal state, in order to transmit data, the terminal in the idle state has to perform a complicated signaling process as shown in FIG. 1. In particular, when a terminal transmits a small amount of data, it becomes a large overhead.

Referring to FIG. 1, the terminal 100 transmits a random access preamble to the base station 110 in order to transmit data by transitioning from the RRC idle state to the RRC connected state (S100). Thereafter, the terminal 100 receives a random access response from the base station 110 (S101), and requests the base station 110 to establish an RRC connection (S102).

The base station 110 sets up the RRC connection setup to the terminal 100 (S103), and the terminal 100 reports completion (S104).

When the RRC connection setup is completed to the terminal 100, the base station 110 transmits an initial terminal message to the MME 120 to request a service (S105). The MME 120 requests the base station 110 for initial context setup (S107). Between steps S105 and S107, the base station 110 may set a measurement configuration by transmitting an RRC connection reconfiguration message to the terminal 100 (S106). When the measurement configuration is completed, the terminal 100 transmits an RRC connection reconfiguration message to the base station 110 (S108).

The base station 110 transmits a secure mode command to the terminal 100 (S109), and receives a response thereto (S110).

Thereafter, the base station 110 transmits an RRC connection reconfiguration message for radio bearer setup to the terminal 100 (S111), and receives a response thereto (S112). The base station 110 transmits a response to the initial context setup to the MME 120 (S113), and the MME 120 transmits a bearer modification request to the gateway 130 (S114).

The terminal 100 transmits a UDP / IP packet to the base station 110 (S115), and the base station 110 transmits the packet to the gateway 130 (S116). The gateway 130 transmits a response to the bearer modification to the MME 120 (S117), and transmits a UDP / IP packet response to the base station 110 (S118). The base station 110 transmits the packet to the terminal 100 (S119).

Through this procedure, the terminal 100 delivers the packet to the core network.

Thereafter, the terminal 100 transmits a measurement report to the base station 120 at the periodic or event occurrence according to the measurement configuration (S120). The base station 120 determines whether to release the terminal 100 based on the measurement report or the deactivation timer (S121). If the RRC connection release of the terminal 100 is determined, the base station 110 requests the terminal context release to the MME 120 (S122). The MME 120 commands the terminal context release to the base station 110 (S123), and the base station 110 instructs the terminal 100 to release the RRC connection accordingly (S124).

After the base station 110 releases the RRC connection of the terminal 100, the base station 110 transmits a response to the MME 120 (S125).

Through this procedure, the RRC connection terminal may transition to the RRC idle state.

As described above, in the prior art, a plurality of signaling procedures are required between the terminal and the base station, the base station, and the core network in order for the terminal to transition from the RRC idle state to the RRC connected state or from the RRC connected state to the RRC idle state. In this procedure, when the UE periodically transmits a small amount of data, overhead occurs continuously. On the other hand, in order to reduce the overhead due to the state transition, the terminal can be kept connected, but in this case, even when there is no data transmission, the network state must be periodically measured according to the measurement configuration, and the unnecessary power such as reporting the measurement result. Consumption may be caused. In addition, when maintaining the RRC connection state, there is a problem in that the handover signaling overhead increases according to the movement of the terminal.

NB-IoT 단말을 위한 연결 상태 천이 프로시져Link State Transition Procedure for NB-IoT Terminals

The narrow band IoT terminal is operated in a fixed state and may be installed at a specific location or located within a specific range. Due to this characteristic, the NB-IoT terminal and the base station support the Suspend / Resume procedure. In the RRC connection release message, the base station may request that the terminal maintains an AS context in the RRC_IDLE state. When the terminal receives the RRC connection release message including the RRC suspend information and transitions to the RRC IDLE state (or before the base station sends the message to the terminal), the base station sends an S1 message requesting the state transition of the terminal to the core network. Send ECM IDLE state.

The RRC connection resume procedure is used for an RRC Connected transition in RRC IDLE where information previously stored in the terminal and the base station is used to resume the RRC connection. When the UE transitions to the RRC Connected state by initiating the RRC connection resume procedure (after the base station sends the RRC connection resume message to the UE), the base station sends an S1 message to the core network requesting the state transition of the UE to the ECM CONNECTED state. Enter

Referring to FIG. 2, the terminal 200 performs a random access procedure with the base station 210 (S200). Thereafter, the terminal 200 initiates an RRC connection resumption procedure with the base station 210 to resume the RRC connection (S210).

The base station 210 transmits an S1-AP terminal context resume request to the MME 215 (S220), and receives an S1-AP terminal context resume response (S230). When the base station 210 receives the terminal context resume response, the base station 210 may change the connection state of the terminal 200 to the RRC connection state by performing an RRC reconfiguration procedure with the terminal 200.

Thereafter, the terminal 200 transmits uplink data to the core network through the base station 210, the MME 215, the serving gateway 220, and the PDN gateway 225. The MME 225 transmits a modification bearer request to the serving gateway 220 (S260), and receives a modification bearer response from the serving gateway 220 (S270).

Through the above procedure, the terminal (eg, the NB-IoT terminal) may transmit and receive data by resuming the RRC connection.

However, even in this case, the RRC connection state and the ECM connection state are made the same, and thus there is a problem in that unnecessary overhead is generated between the base station and the core network. That is, as described above, in the conventional mobile communication technology, there is a signaling overhead problem due to a state transition, and the suspend / resume procedure for the fixed location terminal that can reduce the problem can be applied only to the NB-IoT terminal. . Accordingly, when the terminal leaves the cell (or base station) provided with the previously stored AS context, the terminal had to perform a service request procedure as shown in FIG. 1 to transmit the uplink data. In addition, since the UE transitions from the Suspend state to the Resume state is the same as the transition between the IDLE state and the CONNECTED state, there is a problem of continuously inducing core network signaling (S1 signaling).

In order to solve this problem, a specific procedure for transitioning only the wireless network connection state without core network signaling has been proposed. However, when only the wireless network connection state is changed without the core network signaling, various problems may occur as the base station and the core network recognize the connection state of the corresponding terminal differently.

라이트 커낵션(Light Connection) 상태Light Connection Status

3GPP is working on a light connection state to reduce signaling. The main functions for a lightly connected UE are as follows.

The S1 connection is maintained within the anchor eNB and is active.

Support for RAN initiated paging.

The paging procedure is controlled by the anchor base station.

The RAN based paging area may be configured UE-specifically.

When performing cell selection based mobility, the same mechanism as the cell selection mechanism of RRC IDLE is used.

The terminal AS context is maintained in at least one of the terminal and the anchor base station.

-ECM state in MME is ECM-CONNECTED state.

As described above, in the conventional mobile communication technology, there is a signaling overhead problem due to a state transition, and a study is performed on a specific RRC state (described below as a light connection state for convenience of description) to reduce this. Is being performed. When the terminal configured with the light connection is out of the paging area, the terminal may perform paging update through the corresponding new cell through the cell selection. However, for a UE configured with a light connection, the core network entity may not know the exact state of the light connection terminal. This is because the S1 connection is maintained in the core network entity, and the light connection terminal is also considered as an ECM-CONNECTED state.

In this case, the core network entity may wish to transition the terminal considered to the ECM-CONNECTED state to the ECM-IDLE state for any reason. For example, the MME may release the S1 connection by initiating a detach procedure, for example by an O & M action. Alternatively, the MME may initiate disconnection of the S1 due to various reasons such as authentication failure, CSG subscription data removal, MME load balancing / redistribution, and the like. If the S1 connection is released, then the RRC connection should be released accordingly. However, for some reason on the network, when a core network entity releases an S1 connection to a lightly connected terminal, no method is provided to handle this on the terminal and the network.

The present disclosure devised to solve such a problem is to provide a method for changing a connection state for a terminal configured a specific RRC state, such as a light connection state. In particular, it is an object of the present invention to provide a method for effectively handling the S1 connection of a light connection terminal for any reason on the network for a terminal configured in a specific RRC state.

The embodiments described below may be applied to a terminal, a base station, and a core network entity (MME) using all mobile communication technologies. For example, the present embodiments may be applied not only to a mobile communication terminal to which LTE technology is applied but also to a next generation mobile communication (eg, 5G mobile communication, New-RAT) terminal, a base station, and a core network entity (AMF). Can be. For convenience of description, the base station may refer to an eNode-B of LTE / E-UTRAN, and the base station (CU, DU, or CU) in a 5G wireless network in which a central unit (CU) and a distribution unit (DU) are separated from each other. DU may represent a logical entity), gNB.

For example, the core network entity may represent an MME, which is a control plane core network entity of an EPC, or may represent an AMF, which is a control plane core network entity of 5GC. Hereinafter, for convenience of description, an MME is described as an example of a core network entity, but as described above, it can be applied to all control plane core network entities such as MME and AMF.

In addition, the specific RRC state described herein means a separate RRC state that is distinct from the conventional RRC connected state and RRC idle state. For example, the specific RRC state refers to an RRC state in which the terminal or the base station stores the terminal context and supports the RAN initiated paging operation. That is, the RRC state may be divided into three types: RRC connection, RRC idle, and specific RRC state. The specific RRC state is an arbitrary term for defining a new RRC state including the above-described features, but is not limited to the term. For example, a particular RRC state may be referred to as a write connection state or an RRC inactive state.

In addition, the anchor base station in the present specification means a terminal having a light connection to the terminal, the serving base station means a base station capable of transmitting a paging message to the terminal in the light connection state. For example, the terminal may configure a light connection state under the control of the anchor base station. In addition, the terminal may perform movement in a lightly connected state, and in this case, may leave the coverage of the anchor base station and enter the control area of the new base station. In this case, the serving base station may be a new base station capable of controlling the terminal, such as sending a paging message to the terminal as the terminal moves. If the terminal does not move, the anchor base station may be a serving base station. The terminal may select / reselect a cell provided by the serving base station. That is, the terminal may camp on the cell.

Hereinafter, a specific RRC state will be described as a light connection state, for example, but the same can be applied to the RRC inactive state applied to 5G mobile communication technology. Therefore, in the present specification, a specific RRC state, a light connection state, and an RRC inactive state are used as needed, and the description thereof will be mainly focused on the light connection state.

On the other hand, the terminal configured in a light connection state may be triggered by the cell selection.

When the lightly connected state terminal moves out of a cell associated with the anchor base station configuring the lightly connected state, the anchor base station cannot know the position of the lightly connected state terminal. The anchor base station configures a light connection state to the terminal so that the network tracks the position of the light connection state terminal, and configures a paging area in the terminal, cell-specifically or through cell information (for convenience of description). Denotes a paging area configured by the anchor base station as a paging area, which is merely for convenience of description and other terms of a similar concept are included in the present invention.). For example, the paging area configuration may include information (cell list) of one or more cells about the paging area ID. For example, the cell information may be cell identification information or global cell identification information. The paging area configuration information may include anchor base station identification information and terminal identification information in the anchor base station.

For example, the above-described paging area configuration information may be indicated through a terminal specific RRC reconfiguration message. As another example, the above-described paging area configuration information may be indicated through a terminal specific RRC release message. As another example, the above-described paging area configuration information may be indicated through system information.

According to the cell reselection criteria, if the UE finds a better suitable cell, the UE reselects to that cell. Or reselect and camp on it. If the terminal is out of the configured paging area (eg, if the reselected cell is not included in at least one paging area information configured in the terminal), the lightweight connected terminal should notify the network. For example, a paging area update may be performed. In another example, if the terminal does not leave the configured paging area, the terminal continues the measurement and the cell selection evaluation (evaluation). If the condition for the cell selection is satisfied, the terminal performs cell selection.

Hereinafter, a method of releasing an S1 connection by a core network entity (eg, MME) for a lightly connected terminal will be described. The methods described below can be used individually or in any combination.

For convenience of description, the present embodiment will be described based on a method of releasing the S1 connection for load balancing between MMEs, but this is only for understanding, and the core network entity (for example, The connected 5G core network control entity, the MME in the ECM-CONNECTED state, may be applied in all cases of disconnecting the S1 connection. That is, S1 disconnection including load balancing TAU required for load balancing is one example and is not limited thereto.

First, the load balancing (redistribution) function between MMEs will be described. For example, there may be a case in which one MME is removed from one MME pool area for operational maintenance. As such, if a load balancing / rebalancing function between MMEs is needed for any reason, the load balancing / rebalancing function between MMEs makes it possible to move a terminal registered in one MME to another MME. The base station may have a pre-adjusted load balancing parameter. For example, if all subscribers have been removed from the MME, the weighting factor may be set to zero. Load redistribution may offload all subscribers or portions of all subscribers. In order to offload the ECM-CONNECTED mode UE, the MME may initiate an S1 release procedure including load balancing TAU required for load balancing. Through this, the S1 connection and the RRC connection are released. The terminal then initiates a TAU. However, the terminal does not provide S-TMSI or GUMMEI to the base station in the RRC configuration (The S1 and RRC connections are released and the UE initiates a TAU but provides neither the S-TMSI nor the GUMMEI to eNodeB in the RRC establishment). For example, IMSI may be used as a terminal identifier in an RRC configuration process. Accordingly, the UE performs a TAU with another MME other than the MME indicating load balancing.

According to the procedure described above, the terminal may be configured to transition to a specific RRC state including a light connection state. When the S1 release procedure is initiated by the core network entity when the terminal is configured in a light connection state, the anchor base station needs to release the RRC connection of the terminal. For example, if the load redistribution function is triggered by the MME for a lightly connected terminal, an S1 release procedure including load balancing TAU required for load balancing may be initiated. After the anchor base station receives an S1 release message (for example, a UE Context Release Command message) including TAU request indication for load balancing (eg, UE Context Release Command message), various embodiments of the present invention will be applied. Can be. Each embodiment below may be applied independently or in part / in any combination.

First embodiment: A method of releasing RRC connection after transitioning a terminal to an RRC connected state .

Referring to FIG. 3, the core network entity (eg, MME, 304) transmits an S1 release request message (eg, a UE Context Release Command message) to the anchor base station 303 (S310). The S1 release request message may include load balancing TAU required for load balancing.

When the anchor base station 303 receives the S1 release request message for the lightweight connection terminal 301, the anchor base station 303 may mark RAN based paging (or RAN initiated paging, RAN based paging or RAN initiated paging below). It is started. If the load balancing TAU required for load balancing is included in the S1 release request message, the anchor base station 303 may store or buffer it. The anchor base station 303 transmits a message (a message for downlink data notification or a RAN based paging message) to instruct paging to another base station 302 in the paging area (S320).

Upon receiving the paging request from the anchor base station 303, the new base station 302 broadcasts the paging message to the terminal 301 (S330).

Upon receiving the paging message, the lightweight connection terminal 301 transmits an RRC resumption request message to transition to the RRC connection state (S340). For convenience of explanation, the RRC connection resumption request procedure will be described by way of example. However, this is merely an example and other procedures described separately may be used.

For example, the new base station 302 may perform a procedure for extracting / interrogate / fetch / retrieve / get the terminal AS context (S350). The new base station 302 receives a terminal AS context from the anchor base station 303. For example, it receives a terminal context response message. As another example, if the RAN based paging is due to an S1 release request, the new base station 302 may not perform a procedure for extracting / interrogate / fetch / retrieve / get the terminal AS context. As another example, if RAN-based paging is due to TAU required load balancing for load balancing, the new base station 302 may establish a procedure for extracting / interrogate / fetch / retrieve / get UE AS context. It may not be performed. As another example, if RAN based paging is for RRC disconnection, the new base station 302 may not perform a procedure for extracting / interrogate / fetch / retrieve / get UE AS context.

The new base station 302 transmits an RRC connection resumption message to the terminal 301 (S360).

The terminal 301 transmits an RRC connection resumption completion message to the new base station 302 (S370).

For example, the new base station 302 performs a path switch procedure for changing a path with the core network control entity (MME) 304 (S380).

As another example, if the RAN based paging is due to an S1 release request, the new base station 302 may not perform a path switch procedure for changing a path with the core network control entity (MME) 304.

As another example, if RAN-based paging is due to TAU required load balancing for load balancing, the new base station 302 performs a route switch procedure for changing the path with the core network control entity (MME) 304. You may not.

As another example, if RAN based paging is for RRC disconnection, the new base station 302 may not perform a path switch procedure for changing the path with the core network control entity (MME) 304.

Meanwhile, the core network control entity (MME) 304 performs a bearer modification procedure with the core network data entity (SGW) 305 (S390). As another example, if RAN based paging is due to an S1 release request, S390 may not be performed. As another example, if the RAN based paging is due to TAU request indication for load balancing (Load balancing TAU required), S390 may not be performed. As another example, if RAN based paging is for RRC disconnection, S390 may not be performed.

The new base station 302 releases the terminal context of the anchor base station 303 (S395). As another example, if RAN based paging is due to an S1 release request, S395 may not be performed. As another example, if the RAN based paging is due to TAU request information for load balancing (Load balancing TAU required), S395 may not be performed. As another example, if RAN-based paging is for RRC disconnection, S395 may not be performed.

Meanwhile, after the step S370 of FIG. 3, the new base station 302 may transmit an RRC connection release message to the terminal 301 that releases TAU request indication information (load balancing TAU required) for load balancing. . In this case, S380 to S395 of FIG. 3 are not performed. Or S395 is performed after step S370. To this end, the anchor base station 303 may transmit an X2 message including load balancing TAU required for load balancing to the new base station 303. For example, when the anchor base station 303 transmits a paging request message to the serving base station 302 (S320) or when transmitting a terminal context response message (S350), the TAU request indication information for load balancing is transmitted. It may be.

The terminal 301 receiving the RRC connection release message resets the MAC when leaving the RRC connection. Stop the timer. Release all radio resources including RLC entity, MAC configuration and associated PDCP entity for all configured radio bearers. In addition to the cause of the release, the upper layer indicates that the RRC connection has been released.

On the other hand, when the cause of RRC connection release is TAU request indication information for load balancing, the terminal 301 starts the TAU. However, no S-TMSI or GUMMEI is provided to the

base stations

302 and 303 in the RRC configuration. For example, IMSI may be used as a terminal identifier in an RRC configuration process. When the terminal 301 does not provide S-TMSI or GUMMEI in the RRC configuration, the

base stations

302 and 303 select the MME based on weight factors of MMEs in the pool. The selected new MME performs a TAU response with the terminal 301.

For another example, after the step S395, the new base station 302 may transmit an RRC connection release message to the terminal 301, which releases the load balancing TAU required for load balancing. To this end, the anchor base station 303 may transmit an X2 message including load balancing TAU required for load balancing to the new base station 302. In this case, the X2 message may be delivered after step S395.

When the terminal 301 leaves the RRC connection, it resets the MAC. Stop the timer. Release all radio resources including RLC entity, MAC configuration and associated PDCP entity for all configured radio bearers. In addition to the cause of the release, the upper layer indicates that the RRC connection has been released.

The terminal 301 initiates a TAU. However, no S-TMSI or GUMMEI is provided to the

base stations

As described above, in this embodiment, the RRC connection release procedure is performed after the state transition from the light connection state of the terminal to the RRC connection state. For example, when the core network entity performs the S1 connection release for the UE in the light connection state, the anchor base station performs the RRC resumption procedure by paging the light connection terminal through the serving base station as necessary. When the RRC connection is performed according to the RRC resumption procedure, the RRC release procedure is performed to finally complete the RRC release.

In the above description, the light connection terminal receives the paging through the serving base station according to the movement after the light connection configuration. However, when the light connection terminal does not perform the movement, the anchor base station serves as the serving base station and paging to the terminal. And RRC resumption procedure with the UE. In this case, the anchor base station may perform an RRC release request to the terminal.

Hereinafter, operations of the terminal and the base station performing the above-described embodiment will be described in more detail with reference to the accompanying drawings.

Referring to FIG. 4, the terminal may perform the step of configuring the connection state of the terminal to the specific RRC state based on the indication information indicating the state change to the specific RRC state received from the anchor base station (S400). Here, the specific RRC state is a state distinguished from the RRC connection state and the RRC idle state, and stores the terminal context of the terminal and stores a light connection state or an RRC inactive state supporting the RAN initiated paging operation. it means.

For example, when the terminal is instructed to configure the light connection state from the anchor base station, it may be configured by changing the connection state of the terminal from the RRC connection state to the light connection state. Specifically, the terminal stores the terminal context and sets the necessary configuration for supporting the RAN initiated paging operation. The terminal configures a light connection state and maintains an idle state at the RAN level, but may be configured as an ECM-connected state.

The terminal may perform a step of receiving a RAN initiation paging message caused by the release of the terminal S1 from the anchor base station or the serving base station (S410). When the terminal is configured in a specific RRC state such as a light connection state, the core network entity recognizes the state of the terminal as an ECM-Connected state. Therefore, the core network entity needs to release the S1 connection of the corresponding terminal for any reason.

In this case, the terminal may receive the RAN start paging message from the serving base station when the anchor base station or the serving base station is configured differently from the anchor base station. For example, the RAN initiation paging message may include cause information causing S1 connection release. In order to receive the paging message of the terminal, the core network entity may request release of S1 connection to the terminal configured to a specific RRC state to the anchor base station. The anchor base station may directly transmit the RAN initiation paging message to the terminal to release the S1 connection of the terminal, or may transfer a paging request message to the serving base station of the terminal when the terminal moves. The serving base station broadcasts a paging message to the terminal according to the paging request message.

The UE may perform an operation of transmitting an RRC connection resumption request message for changing a state from a specific RRC state to an RRC connection state based on the RAN initiation paging message (S420). For example, the terminal receiving the paging message may perform a connection state transition operation to the RRC connected state to a specific RRC state. In order to transition from a specific RRC state to an RRC connected state, the terminal performs an RRC connection resumption procedure.

For example, the terminal transmits an RRC connection resumption request message to the base station that has received the paging message. That is, the terminal transmits an RRC connection resumption request message requesting the RRC connection resumption to the serving base station or the anchor base station. The serving base station may receive a terminal context response message from the anchor base station to resume the RRC connection. Meanwhile, the terminal context response message may include cause information causing S1 connection release.

The terminal receives the RRC connection resume message from the base station and performs a connection state transition operation from the specific RRC state to the RRC connection state. For example, the UE resumes the SRB and the DRB suspended in the specific RRC state and configures the RRC connected state using the stored UE context.

When the UE is changed to the RRC connection state, it may perform the step of receiving the RRC connection release request message from the anchor base station or the serving base station (S430). For example, when the UE completes the transition state from the specific RRC state to the RRC connected state, the UE transmits an RRC resumption completion message to the base station. When the base station receives the RRC resumption completion message from the terminal, it can confirm that the terminal is configured in the RRC connection state.

The terminal may receive an RRC connection release request message from the anchor base station or the serving base station. For example, the RRC connection release request message may include information on the cause of the S1 connection release transmitted from the core network entity (eg, MME) to the anchor base station. In more detail, the information on the cause of the S1 connection release may include tracking area update (TAU) request indication information for load distribution. In addition, the information on the cause of the S1 connection release may include various cause information that causes the core network entity to release the S1 connection of the terminal, there is no limitation.

As described above, the S1 connection release cause information may be received by the terminal in step S410, or may be received by the terminal in step S430. Alternatively, the data may be received in duplicate through steps S410 and S430.

When the RRC connection release message is received, the terminal performs a procedure for changing the connection state of the terminal from the RRC connection state to the RRC idle state.

On the other hand, when the mobile station is separated from the anchor base station and the serving base station by moving in a specific RRC state, the anchor base station includes information on the cause of the S1 connection release to the serving base station to release the S1 connection to the terminal in the specific RRC state It may carry a RAN initiated paging request message. The paging request message may be delivered through an X2 interface, which is an interface between the anchor base station and the serving base station.

Through the above operation, the UE in a specific RRC state may perform the RRC release after the transition to the RRC connected state, steps S380 to S395 in FIG. 3 may be omitted as necessary.

Referring to FIG. 5, the serving base station may perform a step of receiving a RAN initiation paging request message causing S1 connection release for a terminal having a specific RRC state through the anchor base station (S500). Here, the specific RRC state is a state distinguished from the RRC connection state and the RRC idle state, and stores the terminal context of the terminal and stores a light connection state or an RRC inactive state supporting the RAN initiated paging operation. it means. That is, the UE may configure a specific RRC state to maintain an idle state at the RAN level, but may be configured as an ECM-connected state.

When the terminal is configured in a specific RRC state such as a light connection state, the core network entity recognizes the state of the terminal as an ECM-Connected state. Therefore, the core network entity needs to release the S1 connection of the corresponding terminal for any reason. In this case, the core network entity may transmit a message requesting release of the S1 connection to the anchor base station.

When the anchor base station receives a release request message for releasing the S1 connection of the terminal from the core network entity, the anchor base station transmits a paging request message for releasing the S1 connection to the serving base station of the corresponding terminal.

The serving base station may receive a RAN initiated paging request message from the anchor base station causing the S1 disconnection. For example, the RAN initiated paging request message may include information on the cause of the S1 connection release. Specifically, the information on the cause of the S1 connection release may include tracking area update (TAU) request indication information for load distribution. In addition, the information on the cause of the S1 connection release may include various cause information that causes the core network entity to release the S1 connection of the terminal, there is no limitation. The RAN initiation paging request message may be delivered via an X2 interface between the anchor base station and the serving base station.

The serving base station may perform the step of transmitting the RAN initiation paging message to the terminal based on the RAN initiation paging request message (S510). When the serving base station receives the paging request from the anchor base station, the serving base station may transmit a paging message for the terminal configured in a specific RRC state. For example, the paging message may be broadcast and delivered.

The serving base station may perform a step of receiving an RRC connection resumption request message for changing a state from a specific RRC state to an RRC connected state from the terminal (S520). The terminal receiving the paging message may perform an RRC connection resumption procedure for the state transition from the specific RRC state to the RRC connected state. The serving base station receives an RRC connection resumption request message for resuming the RRC connection from the terminal, and performs an operation for transitioning the connection state of the corresponding terminal to the RRC connection state.

To this end, the serving base station may receive a terminal context response message from the anchor base station (S525). For example, the serving base station receives the terminal context response message from the anchor base station to resume the RRC connection. The terminal context response message may include cause information that causes the release of the S1 connection.

The serving base station may transmit an RRC connection resume message to the terminal. The serving base station may receive an RRC connection resumption completion message from the terminal when the terminal transitions to the RRC connection state according to the RRC connection resumption message. Through this, the UE of a specific RRC state completes the connection state transition procedure to the RRC connected state.

If the serving base station is changed to the RRC connection state, the serving base station may perform the step of transmitting an RRC connection release request message to the terminal (S530). When the serving base station receives the RRC connection resumption completion message and confirms that the corresponding UE is changed to the RRC connection state, the serving base station may transmit an RRC connection release message to the UE.

The RRC connection release request message may include information on the cause of the S1 connection release transmitted from the core network entity to the anchor base station. For example, the information on the cause of the S1 disconnection may include tracking area update (TAU) request indication information for load distribution.

The serving base station transitions the terminal from the RRC connected state to the RRC idle state according to the RRC connection release procedure.

Through the above operation, the UE in a specific RRC state transitions to the RRC connected state and then the connected state transitions to the RRC release state.

Hereinafter, various embodiments will be described with respect to a method of releasing S1 connection, a method of delivering S1 connection release information, etc. of a terminal in a specific RRC state through a procedure different from the above-described procedure. Embodiments described below may be performed independently, or may be performed in combination with the above-described operations. However, hereinafter, for convenience of understanding, the TAU request for load balancing is explained as a reason for disconnection of the S1, but the present invention is not limited thereto. In addition, the MME is described as an example of a core network entity, but various core network entities such as 5G core network entities may be applicable.

Second embodiment: A method for including S1 disconnection cause information in a RAN based paging request message .

For example, when an anchor base station receives an S1 release request message (eg, a UE Context Release Command message) including load balancing TAU required, the anchor base station receives all relevant signaling and user data. The transmission resource can be released. In addition, the MME may respond with an S1 release complete message (eg, a UE Context Release Complete message).

The anchor base station may trigger RAN initiated paging.

The anchor base station may transmit a paging message on a cell associated with the anchor base station in the paging area configured by the anchor base station. The anchor base station receiving the S1 release request message including load balancing TAU required for load balancing from the MME may transmit a paging message.

The anchor base station may transmit a paging message on a cell associated with another base station and the anchor base station in the paging area configured by the anchor base station. To this end, the anchor base station may instruct paging to the base station (for example, the serving base station). The paging request message transmitted by the anchor base station to the base station may include TAU request indication information for load balancing. For example, when there is an X2 interface between the anchor base station and the corresponding base station, it may include load balancing TAU required for load balancing on the X2 interface paging request message. In another example, when there is no X2 interface between the anchor base station and the base station, the S1 interface paging request message through the MME (anchor base station-> MME S1 interface paging request message, MME-> corresponding base station S1 interface paging indication message) on May include load balancing TAU required for load balancing. For another example, the paging request message transmitted by the anchor base station to the corresponding base station may include cause information. For example, cause information can be set to load balancing TAU required. Or it may be set to, for example, indication information included in the S1 message or cause information set by the anchor base station.

A base station that receives a paging request message including load balancing TAU required for load balancing to an anchor base station may transmit a paging message.

The terminal transmits an RRC connection resume request message to the base station to transition to the connected state. The base station transmits an RRC connection resume message (or RRC connection setup message) to the terminal.

If the terminal receives the RRC connection setup message (or RRC connection resume message) in response to the RRC connection resumption request, the terminal may perform one or more of the following operations.

The terminal may discard the stored terminal AS context and the resume identifier.

The terminal may indicate to the upper layer that the RRC connection resumption has fallen.

Upon receiving the RRC connection resumption message (or RRC connection setup message), the UE may transmit an RRC connection resumption complete message (or an RRC connection setup complete message) to the base station.

The base station transmits an RRC connection release message to the terminal with release balancing of TAU request indication information (load balancing TAU required) for load balancing.

When the terminal leaves the RRC connection, it resets the MAC. Stop the timer. Release all radio resources including RLC entity, MAC configuration and associated PDCP entity for all configured radio bearers. In addition to the cause of the release, the upper layer indicates that the RRC connection has been released.

The terminal initiates a TAU. However, it does not provide S-TMSI or GUMMEI to the base station in the RRC configuration. For example, IMSI may be used as a terminal identifier in an RRC configuration process. When the terminal does not provide S-TMSI or GUMMEI in the RRC configuration, the base station selects the MME based on weight factors of the MMEs in the pool. The selected MME performs a TAU response with the terminal.

Third embodiment: A method of setting up an RRC connection without UE context extraction for an RRC connection resumption request .

For example, when an anchor base station receives an S1 release request message (eg, a UE Context Release Command message) including load balancing TAU required, the anchor base station receives all relevant signaling and user data. The transmission resource can be released. The S1 release complete message (for example, UE Context Release Complete message) may be responded to the core network entity.

The anchor base station may trigger RAN initiated paging.

The anchor base station may transmit a paging message on a cell associated with the anchor base station in the paging area configured by the anchor base station. For example, an anchor base station that receives an S1 release request message including load balancing TAU required from an MME for load balancing may transmit a paging message.

The anchor base station may transmit a paging message on a cell associated with another base station (serving base station) and another anchor base station in the paging area configured by the anchor base station. To this end, the anchor base station may instruct paging to the corresponding base station. The paging request message transmitted by the anchor base station to the base station may include TAU request indication information for load balancing. For another example, the paging request message transmitted by the anchor base station to the corresponding base station may include cause information. For example, cause information may be set to load balancing TAU required. As another example, it may be set to indication information included in the S1 message or cause information set by the anchor base station.

The terminal transmits an RRC connection resumption request message (or RRC connection request message) to the base station to transition to the connected state.

For example, if a corresponding base station receives a paging request message including load balancing TAU required for load balancing to an anchor base station and performs paging to a terminal to receive an RRC connection resumption request message, the corresponding base station is RRC The connection setup message can be delivered to the terminal. The RRC connection setup message may include load balancing TAU required for load balancing.

If the UE receives an RRC connection setup message including load balancing TAU required for load balancing in response to the RRC connection resumption request, the UE may perform one or more of the following operations.

The terminal may perform an operation leaving the RRC connection state.

The UE may indicate to the upper layer that the RRC connection has been released.

The terminal initiates a TAU. However, it does not provide S-TMSI or GUMMEI to the base station in the RRC configuration. For example, IMSI may be used as a terminal identifier in an RRC configuration process. When the terminal does not provide S-TMSI or GUMMEI in the RRC configuration, the base station selects the MME based on weight factors of the MMEs in the pool. The selected new MME performs a TAU response with the terminal.

Fourth embodiment: Method of including S1 disconnection cause information in a message including a terminal context .

For example, when an anchor base station receives an S1 release request message (eg, a UE Context Release Command message) including load balancing TAU required for load balancing, the anchor base station receives all relevant signaling and user data transmission resources. Can be terminated. The S1 release complete message (for example, UE Context Release Complete message) may be responded to the core network entity.

An anchor base station receiving an S1 release request message including load balancing TAU required for load balancing from the MME stores / buffers / maintains / corresponds to the load balancing TAU required for load balancing. You can set a variable.

The anchor base station may trigger RAN initiated paging.

The anchor base station may transmit a paging message on a cell associated with the anchor base station in the paging area configured by the anchor base station.

The anchor base station may transmit a paging message on a cell associated with another base station and the anchor base station in the paging area configured by the anchor base station. To this end, the anchor base station may instruct paging to the corresponding base station (serving base station). For example, when there is an X2 interface between the anchor base station and the corresponding base station, the X2 interface paging request message may be transmitted. In another example, when there is no X2 interface between the anchor base station and the base station, the S1 interface paging request message through the MME (anchor base station-> MME S1 interface paging request message, MME-> corresponding base station S1 interface paging indication message) Can transmit

The serving base station that has received the paging request message to the anchor base station may transmit a paging message.

The terminal transmits an RRC connection resumption request message (or RRC connection request message) for transitioning to the connected state to the corresponding serving base station.

The serving base station transmits an RRC connection resumption message to the terminal.

The serving base station requests and receives the terminal (AS) context information from the anchor base station to resume the RRC connection to the terminal. If there is no inter-base station interface (X2 interface) between the new base station and the anchor base station, the terminal (AS) context request information is transmitted to the old anchor base station through the MME and the terminal (AS) from the previous anchor base station through the MME. A context response can be received.

The above-described anchor base station may include load balancing TAU required for load balancing on the terminal (AS) context response message. That is, upon receiving the terminal context request of the serving base station, the anchor base station may transmit the terminal context response message to the serving base station by including information on the cause of the S1 connection release.

For example, the above-described terminal (AS) context information request message transmission of the serving base station and the terminal (AS) context information response message reception of the serving base station from the anchor base station receive an RRC connection request message / RRC connection resumption request message from the terminal. May be initiated. For example, the RRC connection resume message in response to the RRC connection resume request message is a dedicated control channel (DCCH) logical channel through the SRB1 bearer. Therefore, since UE-specific AS context is required, it may proceed between the RRC connection resume request reception and the RRC connection resume response.

As another example, the above-described terminal (AS) context information request message transmission of the serving base station and the terminal (AS) context information response message reception of the serving base station from the anchor base station receive an RRC connection setup complete message / RRC connection resumption complete message from the terminal. And may be initiated.

As another example, the above-described terminal (AS) context information request message transmission of the serving base station and the terminal (AS) context information response message reception of the serving base station from the anchor base station transmit and initiate an RRC connection setup message / RRC connection resume message to the terminal. Can be.

Since the S1 connection is released, the path switch request / response through the MME and / or the base station does not need to release the context to the anchor base station. Alternatively, when the anchor base station transmits the information to the serving base station by including the information on the cause of the S1 connection release in the terminal context response message, the anchor base station releases the terminal context of the terminal.

The UE that has received the RRC connection setup message / RRC connection resume message may transmit an RRC connection setup complete message / RRC connection resume complete message to the base station.

Embodiment 5: A method for including S1 disconnect cause information in a paging message on an interface between a terminal and a base station .

For example, when an anchor base station receives an S1 release request message (eg, a UE Context Release Command message) including load balancing TAU required for load balancing, the anchor base station receives all relevant signaling and user data transmission resources. Can be terminated. In addition, the MME may respond with an S1 release complete message (eg, a UE Context Release Complete message).

The anchor base station may trigger RAN initiated paging.

The anchor base station may transmit a paging message on a cell associated with the anchor base station in the paging area configured by the anchor base station. The anchor base station receiving the S1 release request message including load balancing TAU required for load balancing from the MME may transmit a paging message. The paging message transmitted by the anchor base station on the cell associated with the anchor base station may include load balancing TAU required for load balancing.

The anchor base station may transmit a paging message on a cell associated with another base station (serving base station) and another anchor base station in the paging area configured by the anchor base station. To this end, the anchor base station may instruct paging to the corresponding base station. The paging request message transmitted by the anchor base station to the base station may include TAU request indication information for load balancing. For example, when there is an X2 interface between the anchor base station and the corresponding base station, it may include load balancing TAU required for load balancing on the X2 interface paging request message. In another example, when there is no X2 interface between the anchor base station and the corresponding base station, on the S1 interface paging request message through the MME (anchor base station-> MME S1 interface paging request message, MME-> corresponding base station S1 interface paging indication message). It may include load balancing TAU required for load balancing. For another example, the paging request message transmitted by the anchor base station to the corresponding base station may include cause information. For example, cause information may be set to load balancing TAU required. As another example, it may be set to indication information included in the S1 message or cause information set by the anchor base station.

The base station receiving the paging request message including the load balancing TAU required from the anchor base station for load balancing (TAU required) is a paging message (or CCCH message, a message transmitted through SRB0, paging message below for convenience of description) Can be sent).

For example, the paging message transmitted by the base station on the cell associated with the base station may include load balancing TAU required for load balancing. As another example, the paging message transmitted by the base station on the cell associated with the base station may include cause information. For example, cause information may be set to load balancing TAU required. As another example, it may be set to indication information included in the S1 message or cause information set by the anchor base station.

The UE that receives the load balancing TAU required for load balancing

Disconnect RRC.

Sixth Embodiment: Method of Including S1 Disconnection Cause Information in the RRC Connection Reject Message .

For example, when an anchor base station receives an S1 release request message (eg, a UE Context Release Command message) including load balancing TAU required for load balancing, the anchor base station receives all relevant signaling and user data transmission resources. Can be terminated. The S1 release complete message (eg, UE Context Release Complete) message may be responded to the core network entity.

The anchor base station may trigger RAN initiated paging.

The anchor base station may transmit a paging message on a cell associated with the anchor base station in the paging area configured by the anchor base station. The anchor base station that receives the S1 release request message including load balancing TAU required from the core network entity for load balancing TAU required may transmit a paging message.

The anchor base station may transmit a paging message on a cell associated with another base station and the anchor base station in the paging area configured by the anchor base station. To this end, the anchor base station may instruct paging to the corresponding base station (serving base station). The paging request message transmitted by the anchor base station to the base station may include TAU request indication information for load balancing. For example, when there is an X2 interface between the anchor base station and the corresponding base station, it may include load balancing TAU required for load balancing on the X2 interface paging request message. In another example, when there is no X2 interface between the anchor base station and the base station, the S1 interface paging request message through the MME (anchor base station-> MME S1 interface paging request message, MME-> corresponding base station S1 interface paging indication message) May include load balancing TAU required for load balancing. For another example, the paging request message transmitted by the anchor base station to the corresponding base station may include cause information. For example, cause information may be set to load balancing TAU required. As another example, it may be set to indication information included in the S1 message or cause information set by the anchor base station.

For another example, as in the above-described fourth embodiment, the TAU request indication information for load balancing may be included in the terminal context message.

A base station (or a base station receiving a paging request message) that receives a paging request message including load balancing TAU required for load balancing to an anchor base station may transmit a paging message to the terminal.

When the base station receives the RRC connection resumption request message (or RRC connection request message) from the terminal, (if the base station receives / store / buffer / TAU request indication information (load balancing TAU required) for load balancing to the terminal If the maintenance / corresponding variable is set, the base station transmits an RRC connection reject message to the terminal. The RRC connection reject message may include load balancing TAU required for load balancing. Although shown as an RRC connection rejection message for convenience of description, this means any RRC message that rejects / releases / confirms / setups / resumes / reconfigures an RRC connection resumption request.

The terminal resets the MAC and releases the MAC configuration.

If the UE receives an RRC connection rejection message including load balancing TAU required for load balancing, the UE informs the upper layer of the rejection of the RRC connection by TAU request indication for load balancing.

Embodiment 7: The method includes the S1 connection release reason information in the RRC connection resume message .

The anchor base station may trigger RAN initiated paging.

The anchor base station may transmit a paging message on a cell associated with another base station and the anchor base station in the paging area configured by the anchor base station. To this end, the anchor base station may instruct paging to the corresponding base station. The paging request message transmitted by the anchor base station to the base station may include TAU request indication information for load balancing. For example, when there is an X2 interface between the anchor base station and the corresponding base station, it may include load balancing TAU required for load balancing on the X2 interface paging request message. In another example, when there is no X2 interface between the anchor base station and the base station, on the S1 interface paging request message through the MME (anchor base station-> MME S1 interface paging request message, MME-> corresponding base station S1 interface paging indication message). It may include load balancing TAU required for load balancing. For another example, as in the above-described fourth embodiment, the TAU request indication information for load balancing may be included in the terminal context message.

A base station (or serving base station) that receives a paging request message including load balancing TAU required for load balancing to an anchor base station may transmit a paging message to the terminal.

When the base station receives the RRC connection resumption request message / RRC connection request message from the terminal, (if the base station receives / store / buffer / maintain / load balancing TAU required for load balancing for the terminal) If the corresponding variable is set, the base station may transmit the TAU request indication information (load balancing TAU required) for load balancing in the RRC connection resume message (or RRC message in response to the RRC connection resume request) to the terminal.

Upon receiving load balancing TAU required for load balancing, the UE may perform one or more of the following operations.

-Disconnect RRC.

When the terminal leaves the RRC connection, it resets the MAC.

-Stop the timer.

Release all radio resources including RLC entity, MAC configuration and associated PDCP entity for all configured radio bearers.

Inform the upper layer of the load balancing TAU required for load balancing.

Eighth Embodiment: A method of sending terminal AS context information together when sending a paging request message .

If the UE leaves the cell associated with the anchor base station when the RAN-based paging procedure is performed, the terminal performs paging through the cell associated with the serving base station. In this case, the terminal AS context is required on the RRC connection establishment / RRC connection resumption procedure performed subsequent to paging. When the RAN-based paging procedure is performed to reduce signaling, the anchor base station may send a terminal AS context to the serving base station. For example, when there is an X2 interface between the anchor base station and the corresponding base station, the terminal may include the terminal AS context on the X2 interface paging request message. In another example, when there is no X2 interface between the anchor base station and the base station, the S1 interface paging request message through the MME (anchor base station-> MME S1 interface paging request message, MME-> corresponding base station S1 interface paging request message) on the It can transmit by including the terminal AS context. For another example, it may respond with the AS context information needed to configure SRB1.

In addition to the first to eighth embodiments described above, it is possible to perform load balancing between MMEs when originating signaling or originating data is generated from the terminal. Alternatively, only release of the S1 connection may be performed. For this purpose, the anchor base station maintains the above-described load balancing TAU required for load balancing, and when the originating signaling or the originating data is generated, the base station may select the MME based on weight factors of MMEs in the pool. . The selected new MME may perform a TAU response with the terminal.

Alternatively, the serving base station (or anchor base station) may broadcast load balancing TAU required for load balancing through the system information. Through this, the terminals in the base station may perform load balancing between MMEs.

The core network entity may release the S1 connection for a terminal configured in a specific RRC state independently or in combination with the various embodiments described above. In addition, the UE may release the RRC connection according to the release of the S1 even in a specific RRC state.

Meanwhile, a description will be given of a non-access stratum (NAS) state and a light connection state transition method of a terminal. The following methods can be used individually or in combination.

* -When the NAS recognizes a light connection (terminal NAS: ECM-CONNECTED, terminal AS: RRC-IDLE)

For example, when a light connection is configured to the terminal through the RRC signaling, the RRC of the terminal may inform it to the NAS. In this case, the NAS of the terminal may consider the terminal as an ECM-CONNECTED but RRC-IDLE state. Alternatively, the NAS of the terminal can be seen that the light connection state. The NAS of the terminal maintains the NAS context.

When the NAS signaling or the MO data is triggered, the NAS / higher layer may instruct the RRC to transition to the connected state through the stored AS context.

In the Suspend / Resume procedure for a conventional NB-IoT terminal, an RRC Connection Resume Request is initiated by an indication of a higher layer. In resuming an RRC connection according to an indication of a higher layer, the resume cause included in the RRC Connection Resume Request message (resumeCause-r13) has one of the following establishment causes (EstablishmentCause-NB-r13).

EstablishmentCause-NB-r13 :: = ENUMERATED {mt-Access, mo-Signalling, mo-Data, mo-ExceptionData, spare4, spare3, spare2, spare1}

If it is to transition the light connected terminal to the connected state, the base station (serving base station) should be aware of the cause in order to extract the terminal AS context from the anchor base station. For example, the upper layer and / or the RRC Connection Resume Request message may be indicated by using one of spare values of the establishment cause (EstablishmentCause-NB-r13) for indicating the resume cause (ruseCause-r13). Can be.

As another example for distinguishing and indicating this, the upper layer and / or the RRC Connection Resume Request message may define and indicate a field different from the resume cause (resumeCause-r13). Through this, the base station is a terminal AS from the anchor base station to transition to the connection state that the corresponding resumption cause is mt-Access, mo-Signalling, mo-Data, mo-ExceptionData and that the resume request message is triggered light You can see that it is instructed to extract the context. As another example for distinguishing and indicating this, the higher layer and / or the RRC Connection Resume Request message may be used to transition a connection terminal in which the cause of establishment on the existing resume cause (resumeCause-r13) and the corresponding resume request message have been triggered to the connected state. In this case, a field indicating that the terminal AS context is extracted from the anchor base station may be defined and indicated.

-When the NAS recognizes a light connection (terminal NAS: ECM-IDLE, terminal AS: RRC-IDLE)

As another example, when a light connection is configured to the terminal through RRC signaling, the RRC of the terminal may inform this to the NAS. For example, RRC can send information to the NAS indicating light connectivity. In this case, the NAS of the terminal may consider the terminal as the ECM-IDLE, RRC-IDLE state. It can be seen that the terminal is in a light connection state. Alternatively, the NAS of the terminal can be seen that the light connection state.

The NAS of the terminal may perform one or more of the following operations.

The terminal maintains a NAS context.

The terminal stores the NAS context.

-The terminal releases the NAS context, but stores it. When NAS signaling or MO data is triggered in the terminal, it reuses, resumes, recovers, maintains, and invokes it.

The terminal suspends the NAS context. When NAS signaling or MO data is triggered in the terminal, it reuses, resumes, recovers, maintains, and invokes it.

When the NAS signaling or MO data is triggered, the NAS / upper layer is delivered to the RRC. The RRC may be made to transition to a connected state through a maintained / stored AS context.

In the Suspend / Resume procedure for a conventional NB-IoT terminal, an RRC Connection Resume Request is initiated by an indication of a higher layer. In resuming the RRC connection when instructed by a higher layer, the resume cause included in the RRC Connection Resume Request message (resumeCause-r13) has one of the following establishment causes (EstablishmentCause-NB-r13).

If it is to transition the light connected terminal to the connected state, the base station should be aware of the cause in order to extract the terminal AS context from the anchor base station. For example, the upper layer and / or the RRC Connection Resume Request message may be indicated by using one of spare values of the establishment cause (EstablishmentCause-NB-r13) for indicating the resume cause (ruseCause-r13). Can be.

-If the NAS does not recognize the light connection status (terminal NAS: ECM- CONNECTED, terminal AS: RRC-IDLE)

As another example, when a light connection is configured to the terminal through the RRC signaling, the RRC of the terminal may not notify this to the NAS. In this case, the NAS of the terminal considers the terminal to be in the ECM-CONNECTED state. The AS (or RRC) of the terminal may be considered as an RRC-IDLE state. It can be seen that the terminal (or AS or RRC of the terminal) is in a light connection state. When NAS signaling or MO data is triggered, the NAS / higher layer forwards it to the corresponding SRB or DRB. When data is transmitted to the SRB / DRB, the RRC can be made to transition to the connected state through the maintained / stored AS context.

Hereinafter, an uplink signal transmission method of a lightly connected state terminal will be described. For example, the uplink signal may be data, signaling, a response to paging, a signal for transitioning the RRC connection state, and the like.

When there is uplink data / signaling to be transmitted by the UE configured with the light connection (for MO data or MO signaling) or when the UE configured with the light connection receives paging, the UE may switch to the RRC connected state in the corresponding cell. .

-How to use RRC Connection request message

The terminal may transmit the RRC Connection request message to the base station through a common control channel (for example, CCCH).

If the transition from the light connection state to the connection state is triggered by the upper layer, and if the upper layer provided the S-TMSI, the value received from the upper layer may be set as the terminal identifier (ue-Identity).

If a transition from the light connection state to the connection state is triggered in the AS, the terminal identifier may set a stored value received from the base station. This will be described later.

If a transition from the light connection state to the connection state is triggered by the upper layer, then a value of establishmentcause corresponding to the information received from the upper layer can be set.

For example, the terminal may add information indicating a transition from the light connection state to the connection state.

If a transition from a light connection to a connection is triggered by a higher layer, you can set a value for establishmentcause that corresponds to the information received from the higher layer.

If the transition from the light to the connected state is triggered in the AS, you can set the value to indicate the transition from the light to the connected state as the setting cause.

As another example, the UE may add information indicating a transition from the light connection state to the connection state to the RRC Connection setup complete message.

-How to use RRC Connection re-establishment Request message

The terminal may transmit the RRC Connection Reset Request message to the base station through a common control channel (for example, CCCH).

The terminal sets the C-RNTI used in the cell indicating the light connection state to c-RNTI.

The terminal sets the physical cell identifier in the cell indicating the light connection state to phyCellId.

The terminal may set a value indicating a transition cause (reestablishmentsCause) from the light connection state to the connection state.

As another example, if a transition from the light connection state to the connection state is triggered in the AS, the terminal identifier may set a stored value received from the base station. This will be described later.

-How to use RRC Connection resume Request message

The terminal may transmit an RRC Connection Resumption Request message to the base station through a common control channel (eg, CCCH).

The terminal identifier may set a stored value received from the base station. This will be described later.

If the transition from the light connection state to the connection state is triggered by the upper layer, it is possible to set the restart / setting cause value corresponding to the information received from the upper layer.

As another example, the UE may add information indicating a transition from the light connection state to the connection state to the RRC Connection resume complete message.

-How to use new RRC Connection request message using common control channel

The terminal may transmit a new RRC Connection request message to the base station through a common control channel (for example, CCCH).

As another example, the UE may add information indicating a transition from a light connection state to a connection state to a new RRC Connection setup complete message.

Meanwhile, the light connection state terminal identification information will be described below.

The cell selection may be triggered by the movement of a lightly connected terminal. Therefore, even when a light connection terminal moves, it must be able to identify the terminal in the network. In addition, when the terminal moves, in order to query / fetch / interrogate the terminal context for the terminal and process the base station identification information and / or cell identification information configured in a light connection state of the terminal may be required. In order to effectively perform the state transition and data transmission for the terminal, the following information may be used individually or in combination as a light connection state terminal identification information.

A method for storing terminal identification information of a core network as terminal identification information.

The terminal identification information of the core network includes a core network entity code and identification information temporarily assigned by the core network entity. Therefore, the terminal can be uniquely identified within the core network entity.

A method for storing cell identification information and wireless network identification information as terminal identification information.

If a cell in the network can be uniquely identified through the cell identification information, the terminal can be uniquely identified by combining the cell identification information and the wireless network identification information assigned by the base station accommodating the cell.

-A method for storing base station identification information and wireless network identification information as terminal identification information .

If the base station in the network can be uniquely identified through the base station identification information, the terminal can be uniquely combined with the base station identification information and the wireless network identification information assigned by the base station. For example, this may be a resume identifier.

A method of storing CU identification information and wireless network temporary identification information as terminal identification information .

If the CU in the network can be uniquely identified through the CU identification information, the terminal can be uniquely combined with the CU identification information and the wireless network temporary identification information temporarily allocated by the CU.

By using each of the embodiments described above, an efficient signaling processing method of a terminal configured with a specific RRC state such as a light connection state may be provided. In addition, when S1 disconnection is triggered for a UE configured to a specific RRC state, it may provide an effect of clarifying operations of the BS and the UE.

Referring to FIG. 6, the terminal 600 for changing a connection state may include a control unit configured to configure the connection state of the terminal to a specific RRC state based on the indication information indicating a state change to a specific RRC state received from the anchor base station. 610 for receiving a RAN initiation paging message from the anchor base station or the serving base station that causes the UE to release the S1 connection, and for changing the state from the specific RRC state to the RRC connected state based on the RAN initiation paging message. It may include a transmitter 620 for transmitting the RRC connection resumption request message.

When the receiver 630 changes to the RRC connected state, the receiver 630 may further receive an RRC connection release request message from the anchor base station or the serving base station.

Meanwhile, a specific RRC state is a state distinguished from an RRC connection state and an RRC idle state, and stores a terminal context of a terminal and stores a light connection state or an RRC inactive state supporting the RAN initiated paging operation. it means.

For example, the receiver 630 may receive an instruction to configure a light connection state from the anchor base station, and the control unit 610 may be configured by changing the connection state of the terminal from the RRC connection state to the light connection state. In detail, the controller 610 stores a terminal context and sets a required configuration for supporting a RAN initiated paging operation.

The RRC connection release request message received by the receiver 630 may include information on the cause of S1 connection release transmitted from the MME to the anchor base station. For example, the information on the cause of the S1 connection release may include tracking area update (TAU) request indication information for load distribution.

As described above, when receiving the RAN initiated paging message from the serving base station, the serving base station receives from the anchor base station a RAN initiated paging request message or a terminal context response message including information on the cause of the S1 disconnection via the X2 interface. can do.

In addition, the controller 610 controls the overall operation of the terminal to efficiently solve the S1 connection release triggered for any reason on the network for the terminal configured to a specific RRC state required to perform the above-described embodiments do.

The transmitter 620 and the receiver 630 are used to transmit and receive signals, messages, and data necessary for performing the above-described embodiments with a serving base station, an anchor base station, or a core network entity.

Referring to FIG. 7, a serving base station 700 for changing a connection state of a terminal receives a RAN initiation paging request message that causes S1 connection release for a terminal having a specific RRC state through an anchor base station. And a transmitter 720 transmitting the RAN initiation paging message to the terminal based on the RAN initiation paging request message and transmitting the RRC connection release request message to the terminal when the terminal is changed to the RRC connection state.

In addition, the receiver 730 may receive an RRC connection resumption request message for changing a state from a specific RRC state to an RRC connection state from the terminal. In addition, the receiving unit 730 may receive a terminal context response message from the anchor base station. Meanwhile, a specific RRC state is a state distinguished from an RRC connection state and an RRC idle state, and stores a terminal context of a terminal and stores a light connection state or an RRC inactive state supporting the RAN initiated paging operation. it means.

For example, the RRC connection release request message may include information on the cause of the S1 connection released from the MME to the anchor base station. The information on the cause of the S1 connection release may include tracking area update (TAU) request indication information for load distribution.

The receiver 730 may receive a RAN initiation paging request message or a terminal context response message including information on the cause of the S1 connection release through the X2 interface.

The controller 710 controls the overall operation of the base station 700 to efficiently solve the S1 connection release is triggered for any reason on the network for the terminal configured to a specific RRC state required to perform the above-described embodiments of the present invention. do.

The transmitter 720 and the receiver 730 are used to transmit and receive signals, messages, and data necessary for performing the above-described embodiments with an anchor base station, a terminal, or a core network entity.

The standard contents or standard documents mentioned in the above embodiments are omitted to simplify the description of the specification and form a part of the present specification. Therefore, the addition of the contents of the standard and part of the standard documents to the specification or the description in the claims should be construed as falling within the scope of the present invention.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

CROSS-REFERENCE TO RELATED APPLICATIONCROSS-REFERENCE TO RELATED APPLICATION

This patent application is related to the patent application No. 10-2016-0122507 filed in Korea on September 23, 2016 and the patent application No. 10-2017-0118911 filed in Korea on September 15, 2017. Priority is claimed under section (a) (35 USC § 119 (a)), all of which is incorporated by reference in this patent application. In addition, if this patent application claims priority for the same reason for countries other than the United States, all its contents are incorporated into this patent application by reference.

Claims

In the method for the terminal to change the connection state,

Configuring the connection state of the terminal to the specific RRC state based on the indication information indicating the state change to the specific RRC state received from the anchor base station;

Receiving a RAN initiation paging message caused by S1 disconnection of the terminal from the anchor base station or serving base station;

Transmitting an RRC connection resumption request message for changing a state from the specific RRC state to an RRC connected state based on the RAN initiation paging message; And

Receiving an RRC connection release request message from the anchor base station or the serving base station when the change to the RRC connection state,

The specific RRC state,

And a state distinct from the RRC connection state and the RRC idle state.
The method of claim 1,

The specific RRC state,

The terminal context of the terminal is stored, characterized in that the RRAN Inactive state or a write connection state that supports the RAN initiated paging operation.
The method of claim 1,

The RRC connection release request message,

And information on the cause of the S1 connection released from the MME to the anchor base station.
The method of claim 3, wherein

Information on the cause of the S1 connection release,

A tracking area update (TAU) request indication information for load distribution.
The method of claim 1,

When receiving the RAN initiation paging message from the serving base station, the serving base station receives from the anchor base station a RAN initiation paging request message or a terminal context response message including information on the cause of the S1 connection release through an X2 interface. Characterized in that.
In the serving base station to change the connection state of the terminal,

Receiving a RAN initiation paging request message causing S1 connection release for a terminal having a specific RRC state configured through an anchor base station;

Transmitting a RAN initiation paging message to the terminal based on the RAN initiation paging request message;

Receiving an RRC connection resumption request message for changing a state from the specific RRC state to an RRC connection state from the terminal;

Receiving a terminal context response message from the anchor base station; And

If the terminal is changed to the RRC connection state, including the step of transmitting an RRC connection release request message to the terminal,

The specific RRC state,

And a state distinct from the RRC connection state and the RRC idle state.
The method of claim 6,

The specific RRC state,

The terminal context of the terminal is stored in the anchor base station, characterized in that the RRAN inactive (RRC Inactive) state or the right connection state to support the RAN initiated paging operation.
The method of claim 6,

The RRC connection release request message or the terminal context response message,

And information on the cause of the S1 connection released from the MME to the anchor base station.
The method of claim 8,

Information on the cause of the S1 connection release,

A tracking area update (TAU) request indication information for load distribution.
The method of claim 6,

The RAN start paging request message,

And information on the cause of the S1 connection release and is received through an X2 interface.
In the terminal for changing the connection state,

A controller configured to configure a connection state of the terminal to the specific RRC state based on the indication information indicating a state change to the specific RRC state received from the anchor base station;

A receiving unit for receiving a RAN initiation paging message caused by S1 connection release of the terminal from the anchor base station or the serving base station; And

A transmitter for transmitting an RRC connection resumption request message for changing a state from the specific RRC state to an RRC connection state based on the RAN initiation paging message;

The receiving unit,

When the RRC connected state is changed, further receiving an RRC connection release request message from the anchor base station or the serving base station,

The specific RRC state,

The terminal characterized in that the state is distinct from the RRC connection (Connection) state and the RRC idle (Idle) state.
The method of claim 11,

The specific RRC state,

The terminal context of the terminal is stored, the terminal characterized in that the RRAN inactive (Write Connection state) or the RRC Inactive (Inactive) state that supports the RAN initiated paging operation.
The method of claim 11,

The RRC connection release request message,

The terminal characterized in that it comprises information on the cause of the S1 connection released from the anchor base station from the MME.
The method of claim 13,

Information on the cause of the S1 connection release,

And a tracking area update (TAU) request indication information for load distribution.
The method of claim 11,

When receiving the RAN initiation paging message from the serving base station, the serving base station receives from the anchor base station a RAN initiation paging request message or a terminal context response message including information on the cause of the S1 connection release through an X2 interface. Terminal, characterized in that.
In the serving base station for changing the connection state of the terminal,

Receiving unit for receiving the RAN start paging request message caused by the release of the S1 connection to the terminal configured a specific RRC state through the anchor base station; And

A transmitter for transmitting a RAN initiation paging message to the terminal based on the RAN initiation paging request message and transmitting an RRC connection release request message to the terminal when the terminal is changed to the RRC connection state;

The receiving unit,

Receiving a terminal context response message from the anchor base station,

Receiving an RRC connection resumption request message for changing a state from the specific RRC state to an RRC connection state from the terminal;

The specific RRC state,

And a serving base station, wherein the serving base station is distinguished from the RRC connection state and the RRC idle state.
The method of claim 16,

The specific RRC state,

The serving base station of the terminal is stored in the anchor base station, the serving base station, characterized in that the RRC inactive (Write Connection state or inactive) state that supports the paging operation.
The method of claim 16,

The RRC connection release request message or the terminal context response message,

Serving base station, characterized in that it includes information on the cause of the S1 connection released from the anchor base station from the MME.
The method of claim 18,

Information on the cause of the S1 connection release,

A serving base station comprising tracking area update (TAU) request indication information for load distribution.
The method of claim 16,

The RAN start paging request message,

And serving information on the cause of the S1 connection release and being received through an X2 interface.