KR20170114258A - Methods for performing handover and Apparatuses thereof - Google Patents

Abstract

 The present invention relates to a control method and apparatus for reducing a service interruption delay in a handover process of a mobile communication terminal. One embodiment provides a method for a terminal to perform a handover, the method comprising: receiving a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing a service interruption from a source base station; The method comprising the steps of: maintaining a data transmission / reception operation with a source base station until a preset time, confirming whether a connection failure has occurred with a base station of either a source base station or a target base station, And performing a connection failure processing operation when a connection failure with any one of the base stations fails.

Description

[0001] The present invention relates to a method for performing handover,

 The present invention relates to a control method and apparatus for reducing a service interruption delay in a handover process of a mobile communication terminal.

As communications systems evolved, consumers, such as businesses and individuals, used a wide variety of wireless terminals. In a mobile communication system such as LTE (Long Term Evolution) and LTE-Advanced of the current 3GPP series, a high-speed and large-capacity communication system capable of transmitting and receiving various data such as video and wireless data outside a voice- It is required to develop a technique capable of transmitting large-capacity data in accordance with the above-described method.

In accordance with this demand, a small cell technology for providing communication service to a terminal in a hot spot area where a large number of users gather in a narrow area or a wide coverage area provided by the base station has been developed as well as a base station providing an existing wide coverage have. A terminal can transmit and receive high-speed and large-capacity data through a base station providing a wide coverage and a small-cell base station providing a relatively narrow coverage.

In addition, the wireless communication system provides a handover technique that enables a user to seamlessly transmit and receive various data while moving. However, there is a problem that more frequent handover occurs as the number of small cell base stations increases as described above.

In addition, in a handover operation, a terminal is disconnected from a base station in a process of performing a handover from a source base station to a target base station. This problem is causing inconvenience to users in a situation where the demand for high-speed and high-speed communication is increasing.

In the above-mentioned background, an embodiment of the present invention proposes a method and apparatus for reducing data transmission / reception delay between a terminal and a base station in a handover procedure.

In addition, one embodiment of the present invention proposes a processing method and apparatus for a case where a problem occurs in any one of wireless links to which a terminal has connected during a handover process.

According to an embodiment of the present invention, there is provided a method of performing a handover of a mobile station, the mobile station including a radio resource control (RRC) connection including information indicating a handover mode for reducing a service interruption from a source base station Receiving a reconfiguration message and maintaining a data transmission / reception operation with a source base station up to a preset time when the handover mode is configured, checking whether a connection failure has occurred with any one of a source base station and a target base station; And performing a connection failure processing operation when a connection failure with any one of the source base station and the target base station occurs before a preset time.

According to an embodiment of the present invention, there is provided a method for controlling handover of a terminal in a source base station, the method comprising: transmitting a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode And maintaining a data transmission / reception operation with the terminal until a preset time when the terminal is configured in a handover mode, and receiving connection failure processing information from the terminal in the handover procedure.

According to another aspect of the present invention, there is provided a mobile station for performing handover, the mobile station comprising: a receiver for receiving a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing service interruption from a source base station; Mode is configured, the data transmission / reception operation with the source base station is maintained until a preset time, and it is confirmed whether or not the connection failure with any one of the source base station and the target base station has occurred. And a control unit for performing a connection failure processing operation when a connection failure with any one of the base stations occurs.

According to another aspect of the present invention, there is provided a source base station for controlling handover of a mobile station, comprising: a transmitter for transmitting a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode A control unit for maintaining a data transmission / reception operation with a terminal up to a preset time when the terminal is configured for a handover mode, and a receiver for receiving connection failure processing information in a handover process from the terminal.

As described above, the present embodiments provide the effect of minimizing the data communication interruption in the handover process in the handover process and control the communication interruption of the terminal to be minimized even in the event of a problem in the radio link in the handover process to provide.

1 is a view for explaining operations of a terminal according to an embodiment.
2 is a view for explaining an operation of a source base station according to an embodiment.
FIG. 3 is a diagram illustrating an example of a handover procedure according to an embodiment.
4 is a diagram illustrating another example of a handover procedure according to an embodiment.
5 is a diagram illustrating another example of a handover procedure according to an embodiment.
6 is a diagram illustrating an example of a base station changing procedure of a multi-connectivity terminal according to an exemplary embodiment.
7 is a diagram illustrating another example of a base station changing procedure of a multi-connectivity terminal according to an embodiment.
8 is a diagram for explaining a terminal configuration according to an embodiment.
9 is a diagram for explaining a base station configuration according to an embodiment.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals whenever possible, even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

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

In other words, the MTC terminal in this specification may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category / type for performing LTE-based MTC-related operations. Alternatively, the MTC terminal may support enhanced coverage over the existing LTE coverage or a UE category / type defined in the existing 3GPP Release-12 or lower that supports low power consumption, or a newly defined Release-13 low cost low complexity 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. A wireless communication system includes a user equipment (UE) and a base station (BS, or eNB). The user terminal in this specification is a comprehensive concept of a terminal in wireless communication. It is a comprehensive concept which means a mobile station (MS), a user terminal (UT), an SS (User Equipment) (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 (eNB), a sector, a Site, a BTS A base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell.

That is, the base station or the cell in this specification is interpreted as a comprehensive meaning indicating a partial region or function covered by BSC (Base Station Controller) in CDMA, NodeB in WCDMA, eNB in LTE or sector (site) And covers various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU, and small cell communication range.

Since the various cells listed above exist in the base station controlling each cell, the base station can be interpreted into two meanings. i) the device itself providing a megacell, macrocell, microcell, picocell, femtocell, small cell in relation to the wireless region, or ii) indicating the wireless region itself. i indicate to the base station all devices that are controlled by the same entity or that interact to configure the wireless region as a collaboration. An eNB, an RRH, an antenna, an RU, an LPN, a point, a transmission / reception point, a transmission point, a reception point, and the like are exemplary embodiments of a base station according to a configuration method of a radio area. ii) may indicate to the base station the wireless region itself that is to receive or transmit signals from the perspective of the user terminal or from a neighboring base station.

Therefore, a base station is collectively referred to as a base station, collectively referred to as a megacell, macrocell, microcell, picocell, femtocell, small cell, RRH, antenna, RU, low power node do.

Herein, the user terminal and the base station are used in a broad sense as the two transmitting and receiving subjects used to implement the technical or technical idea described in this specification, and are not limited by a specific term or word. The user terminal and the base station are used in a broad sense as two (uplink or downlink) transmitting and receiving subjects used to implement the technology or technical idea described in the present invention, and are not limited by a specific term or word. Here, an uplink (UL, or uplink) means a method of transmitting / receiving data to / from a base station by a user terminal, and a downlink (DL or downlink) .

There are no restrictions on multiple access schemes applied to wireless communication systems. Various multiple access schemes 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- Can be used. An embodiment of the present invention can be applied to asynchronous wireless communication that evolves into LTE and LTE-Advanced via GSM, WCDMA, and HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000, and UMB. The present invention should not be construed as limited to or limited to a specific wireless communication field and should be construed as including all technical fields to which the idea of the present invention can be applied.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

In systems such as LTE and LTE-Advanced, the uplink and downlink are configured on the basis of one carrier or carrier pair to form a standard. The uplink and the downlink are divided into a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel, a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control Channel (EPDCCH) Transmits control information through the same control channel, and is configured with data channels such as PDSCH (Physical Downlink Shared CHannel) and PUSCH (Physical Uplink Shared CHannel), and transmits data.

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

In this specification, a cell refers to a component carrier having a coverage of a signal transmitted from a transmission point or a transmission point or a transmission / reception point of a signal transmitted from a transmission / reception point, and the transmission / reception point itself .

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

The multi-point transmission / reception point includes a base station or a macro cell (hereinafter referred to as 'eNB'), and at least one mobile station having a high transmission power or a low transmission power in a macro cell area, Lt; / RTI >

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

Hereinafter, a situation in which a signal is transmitted / received through a channel such as PUCCH, PUSCH, PDCCH, EPDCCH, and PDSCH is expressed as 'PUCCH, PUSCH, PDCCH, EPDCCH and PDSCH are transmitted and received'.

In the following description, an indication that a PDCCH is transmitted or received or a signal is transmitted or received via a PDCCH may be used to mean transmitting or receiving an EPDCCH or transmitting or receiving a signal through an EPDCCH.

That is, the physical downlink control channel described below may mean a PDCCH, an EPDCCH, or a PDCCH and an EPDCCH.

Also, for convenience of description, EPDCCH, which is an embodiment of the present invention, may be applied to the portion described with PDCCH, and EPDCCH may be applied to the portion described with EPDCCH according to an embodiment of the present invention.

Meanwhile, the High Layer Signaling described below includes RRC signaling for transmitting RRC information including RRC parameters.

The eNB performs downlink transmission to the UEs. The eNB includes a physical downlink shared channel (PDSCH) as a main physical channel for unicast transmission, downlink control information such as scheduling required for reception of a PDSCH, A physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission in a Physical Uplink Shared Channel (PUSCH). Hereinafter, the transmission / reception of a signal through each channel will be described in a form in which the corresponding channel is transmitted / received.

The term " handover " used herein refers to a technique used when a mobile station changes a base station or a cell, and includes both a signal transmission / reception operation and a signal processing operation between a mobile station, a source base station, and a target base station. In addition, the source base station refers to a base station that establishes a connection for data transmission / reception with the mobile station at the start of the handover procedure. The target base station transmits a target base station to which the mobile station attempts to establish data connection / it means. Hereinafter, a communication target in which a mobile station deviates from a handover procedure will be described as a source base station or a source cell, and a communication target in which a mobile station attempts to establish a wireless connection through a handover procedure will be described as a target base station or a target cell.

In the handover technique, the target base station prepares the handover according to the handover request message from the source base station. The target base station generates an RRC message (for example, an RRCConnectionReconfiguration message including mobilityControlInformation) to be transmitted to the UE in order to perform handover. The target base station sends a handover request acknowledgment (ACKNOWLEDGE) message to the source base station.

 The handover request confirmation message includes a container for carrying an RRC message to be delivered to the terminal for performing handover. The container includes a new C-RNTI, a target eNB security algorithm identifier, a dedicated RACH preamble, a target eNB SIBs, and some other parameters. The RRC message to be transmitted to the UE can be generated by the target BS in the RRC reconfiguration message including the mobility controlInfo and transmitted to the UE through the source BS. The source base station performs integrity protection and ciphering necessary for the RRC message.

Thereafter, the source base station stops the downlink data transmission to the terminal.

After receiving the RRCConnectionReconfiguration message including the mobilityControlInformation, the UE performs synchronization with the target base station and accesses the target cell via the RACH.

The terminal derives the target base station specific key and constructs a selected security algorithm to be used in the target cell. This will be described in more detail as follows.

After receiving the RRCConnectionReconfiguration message including the mobilityControlInformation, if the carrier frequency (carrierFreq) is included, the terminal considers the target PCell as one on the frequency indicated by the carrier frequency with the physical cell identifier indicated by targetPhysCellId. If the carrier frequency (carrierFreq) is not included, the terminal considers the target PCell as one on the frequency of the source PCell with the physical cell identifier indicated by targetPhysCellId.

The terminal starts synchronization on the downlink of the target PCell.

The terminal resets the Master Cell Group (MAC) MAC and, if configured, the Secondary Cell Group (MAC) MAC.

The UE re-establishes the PDCP for all configured RBs (Radio Bearers).

The terminal re-establishes the MCG RLC for all configured RBs (Radio Bearers) and, if configured, the SCG RLC.

The terminal configures the lower layer to consider SCell (s) as inactive if configured.

The UE applies a new UE-Identity to the C-RNTI.

The MS submits the RRC Connection Reconfiguration Complete message to the lower layer for transmission.

The target base station responds with uplink allocation and timing advance (the target eNB responds with UL allocation and timing advance).

When the UE successfully accesses the target cell, the UE transmits an RRCConnectionReconfigurationComplete message (e.g., a RRConnectionReconfigurationComplete message) indicating that the handover for the UE has been completed to the target BS, together with an uplink BSR (Buffer Status Report) C-RNTI). The target base station verifies the C-RNTI included in the RRCConnectionReconfigurationComplete message.

The target base station starts sending data to the terminal.

As described briefly above, in the conventional E-UTRAN technology, a random access has to be performed in order to perform a handover according to cell change. Also, until the UE receives the RRC message and accesses the target cell, and the target cell receives an RRCConnectionReconfigurationComplete message indicating that the handover is completed from the UE, the UE stops data communication with the source base station, The data transmission / reception operation of the terminal is interrupted.

The longer the downtime due to handover on a real wireless network, the more negative the user experience. For example, it is frequent that a downtime due to handover exceeds 50 ms on a wireless network. It is therefore necessary to reduce this delay in order to provide better communication quality.

In this specification, we propose a handover procedure to reduce the service disruption. As an example, there may be a method of maintaining a connection between a terminal and a source base station during the course of a handover procedure. It may also be required that the terminal monitor the source base station link and the target base station link simultaneously. Accordingly, problems may occur in monitoring two base stations (cells).

As described above, in the prior art, a random access has to be performed in order to perform a handover according to a cell change, thereby causing interruption of data transmission for a certain period of time. As a method for reducing this, it is conceivable to maintain the source base station connection during the handover, but this method requires the terminal to simultaneously monitor the source base station link and the target base station link. Accordingly, a problem may occur in one radio link (for example, a target cell or a source cell) in connection with two base stations, and a processing method is required.

 It is an object of the present invention to provide a specific procedure for reducing a data transmission interruption due to a cell change or a base station change. Another object of the present invention is to provide a method and apparatus for efficiently processing a radio link (for example, a target cell or a source cell) when a problem occurs in a state where a connection is established with two cells. In the following description, the source base station and the source cell are described with the same meaning, and the target base station and the target cell are described in the same meaning. Thus, the source base station and the source cell or the target base station and the target cell can be used interchangeably. For convenience of description, the handover in which the UE maintains a connection with the source base station in the handover process will be described as a handover mode for reducing an improved handover or a service interruption.

1 is a view for explaining operations of a terminal according to an embodiment.

Referring to FIG. 1, the UE performs a step of receiving a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing a service interruption from a source base station (S110). The terminal receives a handover command from the source base station. The handover command may be included in the RRC connection reconfiguration message. The RRC connection reconfiguration message may include an RRC container. In one example, the RRC container includes mobility control information, and the mobility control information may include information indicating a handover mode for reducing service interruption. The RRC container may be generated by the target base station and delivered to the terminal via the source base station.

Meanwhile, the RRC connection reconfiguration message may include restriction information for restricting the operation of the terminal when a connection failure with the source base station occurs. For example, the restriction information may include information instructing to deactivate the evaluation operation on the radio quality with the source base station, information instructing the terminal to suspend the RRC IDLE state entry or the RRC connection reestablishment operation until the handover failure time, Information for limiting the number and time of random access or scheduling requests to the base station, and information for limiting measurement reporting transmissions to the source base station.

When the handover mode is configured, the UE maintains a data transmission / reception operation with the source base station until a preset time, and confirms whether a connection failure has occurred with any of the source base station and the target base station (S 120) . The UE may proceed with the procedure of the improved handover mode based on the information indicating the improved handover mode included in the RRC connection reconfiguration message. For example, the UE can maintain the connection with the source BS until the predetermined time in the handover process. The predetermined timing may be a timing at which the random access preamble transmission to the target base station starts, a timing at which the random access response is received from the target base station, a timing at which the random access procedure with the target base station ends, And a time point at which an additional RRC connection reconfiguration message is received from the source base station. The preset time can be stored in advance for improved handover.

In addition, the UE can confirm whether a connection failure has occurred with any one of the source base station and the target base station during the improved handover process. For example, the UE can confirm whether a connection failure has occurred by checking whether the number of random access attempts to the target BS exceeds a preset reference number. As another example, the UE can check whether a random access attempt time to the target base station has exceeded a preset time and whether a connection failure has occurred. The predetermined time may be set using a timer configured in the terminal. For example, the UE may determine that a connection failure with the target BS has occurred when the timer for confirming the connection failure has expired.

Meanwhile, the UE may check whether a connection failure with the source BS occurs during the handover process. For example, the UE can check the connection quality state with the source base station to the reference quality state to determine whether a connection failure with the source base station has occurred.

Meanwhile, if the restriction information is included, the terminal may suspend the connection failure with the source base station without confirming the connection failure to a specific point in time. For example, the terminal may suspend the connection status monitoring with the source base station until the handover is completed, or until random access to the target base station succeeds, or until receiving the random access response information from the target base station.

The UE performs a connection failure processing operation when a connection failure with any one of the source base station and the target base station occurs before a preset time (S130). For example, when the occurrence of a connection failure with the target base station is confirmed, the terminal may perform a connection failure processing operation to transmit information indicating a connection failure to the source base station. In another example, the UE may release the target BS configuration information for handover to the target BS when it is confirmed that the connection failure with the target BS has occurred. As another example, the terminal may not monitor the connection failure with the source base station using the above-described restriction information. As another example, the UE may limit the random access to the scheduling request procedure or the source base station to a specific point in time or a specific number according to the restriction information when a connection failure with the source base station occurs.

In addition, the terminal can perform necessary operations in each failure processing procedure of the source cell connection failure occurrence and the target cell connection failure occurrence described below.

2 is a view for explaining an operation of a source base station according to an embodiment.

2, a method for controlling handover of a terminal in a source base station includes transmitting a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing service interruption to the terminal Step S210 may be performed. The source base station can transmit the RRC container received from the target base station to the mobile station. As described above, the RRC container includes mobility control information and may include information indicating an improved handover mode generated by the target base station. The RRC container is included in the RRC connection reconfiguration message and can be delivered to the UE. The UE receives the RRC connection reconfiguration message and performs the handover procedure according to the improved handover mode.

Meanwhile, the RRC connection reconfiguration message may include restriction information for restricting the operation of the UE when a connection failure with the UE occurs during the handover process. For example, the restriction information may include information for instructing the mobile station to deactivate the evaluation operation on the radio quality with the source base station, information for instructing the terminal to stop performing the RRC IDLE state entry or the RRC connection reestablishment operation until the handover failure time , Information for limiting the number and time of random access or scheduling requests to the source base station, and information for limiting the measurement reporting transmission of the terminal.

In addition, when the handover mode is configured in the terminal, the source base station can perform a step of maintaining the data transmission / reception operation with the terminal up to a preset time (S220). The source base station may proceed with the enhanced handover mode procedure with the terminal based on information indicating an improved handover mode included in the RRC connection reconfiguration message. For example, the source base station can maintain the connection with the terminal until the preset time in the handover process. The predetermined time may be a time at which the UE transmits the random access preamble to the target BS, a time at which the MS receives the random access response from the target BS, a time at which the random access procedure of the MS and the target BS is terminated, A time point at which the MS satisfies the handover condition to the target BS, and a time point at which the MS transmits an additional RRC connection reconfiguration message. The preset time can be stored in advance for improved handover.

The source base station may perform a step of receiving connection failure processing information in a handover process from the terminal (S230). For example, the connection failure processing information may include information indicating a connection failure indicating that the terminal has failed to randomly access the target base station.

In addition, the source base station can perform necessary operations in each failure processing procedure of the source cell connection failure occurrence and the target cell connection failure occurrence described below.

Hereinafter, the connection failure processing operation of the terminal will be described in detail in the case where the connection failure occurs in the radio link of the target cell in the above-described improved handover procedure.

target  How to deal with radio link failure with cell

For convenience of description, a cell associated with a source base station, a source PCell, and a source base station PCell are denoted as source cells, and a cell associated with a target base station, a target PCell, and a target base station PCell are represented as target cells.

And may maintain the source base station connection during handover to reduce service interruption as described above. Thereby allowing data to be transmitted or received via the source cell during handover. Meanwhile, a problem may occur in the target cell radio link according to the movement of the mobile station in the handover process. If a problem occurs in the target cell radio link, handover to the target cell may become impossible. The individual embodiments described below may be used independently or in whole or in part.

1st Example : target  Cell random access  RRC reset on failure Procedure  Start

The UE can apply the improved handover technique by simultaneously configuring the target cell in addition to the source cell in the MAC.

When the UE starts random access to the target cell, the UE can receive a random access problem from the MAC entity.

That is, if the preamble transmission counter exceeds the maximum preamble transmission (If PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1), then if the random access preamble is transmitted on the target cell, the MAC entity may consider the random access unsuccessfully completed .

For example, the MAC entity delivers it to an upper layer (e.g., RRC). The UE can perform the procedure according to the handover failure. For example, one or more operations may be performed, such as storing the handover failure information in the VarRLF-Report and starting the RRC reset procedure.

As another example, the UE can perform the procedure according to the handover failure when the timer started by receiving the RRC message (for example, the T304 timer included in mobilitycontrolInfo or another timer for improved handover) expires. For example, handover failure information may be stored in the VarRLF-Report and the RRC reset procedure initiated.

Second Example : target  Cell random access  Keep source cell connections on failure

The UE can apply the improved handover technique by simultaneously configuring the target cell in addition to the source cell in the MAC.

When the terminal initiates a random access to the target cell, a random access problem can be indicated from the MAC entity.

That is, if the preamble transmission counter exceeds the maximum preamble transmission (If PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1), then if the random access preamble is transmitted on the target cell, the MAC entity may consider the random access unsuccessfully completed . For example, the MAC entity delivers it to an upper layer (e.g., RRC).

The UE can release target cell configuration information (target eNB SIBs, physical layer dedicated configuration information, etc.). If a dual MAC is used to provide improved handover, the terminal may deactivate, deactivate, or reset the target cell MAC.

The terminal maintains / restores the configuration used in the source cell.

The terminal stores the random access failure information in the VarRLF-Report.

Third Example : When a single MAC is configured, information indicating a connection failure (for example, a target cell radio link failure information message) is transmitted to the source base station

The above-described improved handover technique can be provided at a terminal on a single MAC basis.

The UE can apply the improved handover technique by simultaneously configuring the target cell in addition to the source cell in the MAC.

When the terminal initiates a random access to the target cell, the terminal (or RRC) may receive a random access problem from the MAC entity.

That is, if the preamble transmission counter exceeds the maximum preamble transmission (If PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1), the MAC can indicate a random access problem to the upper layer (RRC) if the random access preamble is transmitted on the target cell. At this time, the target cell may be included in the special cell (SpCell).

The terminal may consider the radio link failure for the target cell.

The terminal may initiate a target cell failure information procedure to report a target cell radio link failure.

Upon initiating the target cell failure information procedure, the terminal may perform one or more of the following operations.

- transmits information indicating a connection failure (e.g., a target cell radio link failure information message) to the source base station.

- The terminal may include the failure type information in the information indicating the connection failure. And the failure type information may be set to one of a target cell radio link failure, a random access failure, and a target cell failure.

- The terminal may contain physCellId and quantities information of the best non-serving cell based on RSRP on the relevant serving frequency.

- The terminal may include the best measured cells information and the measured value information on the non-serving frequency for neighboring cell measurement result information.

The UE can release target cell configuration information (target eNB SIBs, physical layer dedicated configuration information, etc.).

The terminal can maintain / recover the configuration used in the source cell.

Fourth Embodiment: When a dual MAC is configured, information indicating a connection failure (for example, a target cell radio link failure information message) is transmitted to the source base station

The above-described improved handover technique can be provided at the terminal on a dual MAC basis.

The UE can apply the improved handover technique by simultaneously configuring the target cell in addition to the source cell in the MAC.

When the terminal initiates a random access to the target cell, the terminal (or RRC) may receive a random access problem from the MAC entity.

That is, if the preamble transmission counter exceeds the maximum preamble transmission (if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1), the MAC can direct the random access problem to the upper layer (RRC) if the random access preamble is transmitted on the target cell. At this time, the target cell may be included in the special cell (SpCell).

The terminal may consider the radio link failure for the target cell.

The terminal may initiate a target cell failure information procedure to report a target cell radio link failure.

Upon initiating the target cell failure information procedure, the terminal may perform one or more of the following operations.

- The terminal suspends / releases all DRBs associated with the target MAC.

- The terminal resets the target MAC. Or the terminal releases / deactivates the target MAC.

- The terminal transmits information indicating a connection failure (for example, a target cell failure information message) to the source base station.

- The terminal contains failure type information. The failure type information is set to either target cell radio link failure, random access failure, or target cell failure.

- The terminal may contain physCellId and quantities information of the best non-serving cell based on RSRP on the relevant serving frequency.

- The terminal may include the best measured cells information and the measured value information on the non-serving frequency for neighboring cell measurement result information.

- The terminal can maintain / recover the configuration used in the source cell

Hereinafter, an individual embodiment in which the UE confirms the source cell radio link failure in the handover process will be described.

How to deal with radio link failure with source cell

The source cell wireless link problem may occur according to the movement of the UE during the handover process. If a source cell radio link problem occurs, data transmission through the source cell may become difficult. The following methods can be used independently or in combination to effectively handle them.

1st Example : Wireless link to source cell Monitoring  How to do it

The downlink radio link quality of the PCell should be monitored so that the physical layer in the terminal indicates the out-of-sync / in-sync state to the upper layer.

The physical layer in the terminal indicates out-of-sync as an upper layer to the radio frame in which the radio link quality is evaluated when the radio link quality is lower than the threshold Qout. If the radio link quality is higher than the threshold value Qin, the physical layer in the terminal instructs the in-sync to the upper layer in the radio frame in which the radio link quality is evaluated.

When a terminal receives an RRC message including information indicating an improved handover from a source base station, the terminal can perform an improved handover procedure.

When the UE receives an RRC message including information indicating an improved handover from the source base station, the UE performs the handover until the handover is completed (or until random access is successfully made to the target cell or an RA response is received from the target cell) ) The terminal can maintain the connection with the source cell. Since the source cell is the PCell of the source base station, the terminal can perform radio link monitoring for the source cell when performing an improved handover.

As described above, in the conventional LTE technology, the handover breaks the source cell and attempts to connect to the target cell. Therefore, the UE receiving the RRC message indicating the handover (for example, the RRC reconfiguration message including the mobility control information) does not need to perform the radio link monitoring for the source cell. According to the prior art, when the UE receives the RRC reconfiguration message including the mobility controlInfo information, the UE starts the T304 timer included in the mobility control information. The UE may receive a timer (e.g., a T300 timer) in response to the connection request message transmission or a timer (e.g., T301 timer) in response to the RRC connection reset request message transmission or a timer (e.g., ), Or wireless link monitoring for PCell was not performed because a connection with PCell was not provided during the operation of a timer (e.g., T311 timer) upon initiation of an RRC connection reset. That is, even when receiving a certain number of consecutive out-of-sync instructions from the lower layer for the PCell (the number of N310 or N310), it does not start a timer (e.g., T310 timer) T300, T301, T304 nor T311 is running: UE shall start timer T310). The terminal receives a further constant number of PCs (a number that is different from N311 or N311) of consecutive in-sync instructions from the lower layer while a timer (e.g., T310 timer) for detecting a radio link failure is operating , The terminal stops the T310 timer. If the T310 timer expires, the UE determines that a radio link failure has been detected. The terminal performs an operation to leave RRC_CONNECTED (an operation to enter RRC IDLE) if AS security has not been activated. Otherwise, the terminal initiates the RRC connection reset procedure. When the radio quality of the source cell deteriorates, the possibility that the mobile station initiates the RRC connection reestablishment procedure increases, and the bad smell due to the connection reestablishment may be larger than the effect of the handover procedure improvement.

In order to improve this, in the present embodiment, it is possible to perform radio link monitoring while performing an improved handover. However, during the handover, it may not fall into the RRC_IDLE for the cell or perform the RRC connection reset procedure until the handover fails (e.g., when the T304 timer expires) .

For example, upon receiving an RRC message including information indicating an improved handover, the UE can perform radio link monitoring. That is, the information indicating the improved handover includes a new timer information element different from the T304 timer, and the terminal can operate a new timer information element when the RRC message is received. The UE may determine that the improved handover has failed if the newly defined timer expires. That is, when the newly defined timer expires, the terminal stores the handover failure information in the VarRLF-Report. In addition, the UE initiates an RRC Connection re-establishment procedure.

As another example, a timer for detecting a radio link failure for a source cell may be defined and handled as a T310 timer for a conventional PCell and other information elements.

As another example, the maximum number of consecutive out-of-sync instructions counted from the lower layer may be defined as N310 and other information elements in order to detect radio link failure for the source cell.

As another example, the maximum number of consecutive in-sync instructions counted from a lower layer for detecting a radio link failure for a source cell can be defined and defined as an information element different from N311, respectively.

If the timer for detecting a radio link failure for the source cell (T310 or the newly defined timer described above) expires, the terminal determines that a radio link failure for the source cell has been detected.

In one example, the terminal may perform one or more of the following operations if a radio link failure for the source cell is detected.

- Reset the MAC entity.

- Stop all running timers. Or stop all running timers except T320 timer, T325 timer and T330 timer.

- Reset the PDCP entity.

- Reset the RLC entity.

- Update the security.

As another example, the terminal may perform one or more of the following operations if a radio link failure to the source cell is detected.

- Limit / suspend / suspend / stop uplink transmissions through the source cell.

- Limit / suspend / suspend / stop random access through the source cell.

- Limit / suspend / suspend / stop scheduling requests through the source cell.

In another example, the terminal may perform one or more of the following operations if a radio link failure for the source cell is detected.

- Reset the MAC entity. Or releases the MAC entity.

- Stop all running timers. Or stop all running timers except T320 timer, T325 timer and T330 timer.

- Release the RLC entity, PDCP entity associated with the source cell, for all configured radio bearers.

- The terminal maintains the RRC Connection.

In another example, the terminal may perform one or more of the following operations if a radio link failure for the source cell is detected.

- Reset the MAC entity.

- Stop all running timers. Or stop all running timers except T320 timer, T325 timer and T330 timer.

- Suspend data transmission for all configured radio bearers.

- The terminal maintains the RRC Connection.

Second Example : Wireless link to source cell Monitoring  How Not to Apply

The downlink radio link quality of the PCell should be monitored so that the physical layer in the terminal indicates the out-of-sync / in-sync state to the upper layer.

The physical layer in the terminal indicates out-of-sync as an upper layer to the radio frame in which the radio link quality is evaluated when the radio link quality is lower than the threshold Qout. If the radio link quality is higher than the threshold value Qin, the physical layer in the terminal instructs the in-sync to the upper layer in the radio frame in which the radio link quality is evaluated.

When the UE receives an RRC message including information indicating an improved handover from the source base station, the UE performs the handover until the handover is completed (or until random access is successfully made to the target cell or an RA response is received from the target cell) ) The terminal can maintain the connection with the source cell.

If radio link monitoring for the source cell is performed, there is a high possibility that the UE will transition to the RRC IDLE state or perform the RRC connection re-establishment procedure. Therefore, when performing an improved handover, the UE can be prevented from applying radio link monitoring to the source cell.

For example, the source base station may instruct the base station to restrict (or suspend or disable, or stop or not apply) wireless link monitoring through higher layer signaling, denoted below as limitations for convenience of illustration.

If the UE receives an upper layer message (e.g., an RRC connection reconfiguration message) including restriction information indicating that the UE should restrict the radio link monitoring (or the RRC connection reconfiguration message) Message), the terminal may not perform radio link monitoring.

In one example, in order to provide an improved handover, the base station may deliver an RRC message including restriction information that instructs the terminal to limit radio link monitoring to the source PCell until handover completion. For example, if the UE maintains a connection with the source BS until the handover is completed, the UE may restrict the radio link monitoring to the source cell until the handover is completed.

As another example, in order to provide an improved handover, the base station may forward an RRC message including restriction information that instructs the terminal to limit the radio link monitoring until the terminal succeeds in random access. For example, if the UE successfully performs random access, it can disconnect the source base station. That is, the UE can disconnect from the source base station through MAC reset, PDCP reset, RLC reset, and the like. In this case, the UE can restrict the radio link monitoring to the source cell until the random access is successful.

 As another example, in order to provide an improved handover, the base station may forward the RRC message including the restriction information indicating to limit the radio link monitoring until the terminal receives the RA Response. For example, the UE can disconnect from the source base station upon receiving the RA Response from the target base station. That is, the UE can disconnect the source base station through MAC reset, PDCP reset, RLC reset, and the like. In this case, the UE can restrict the radio link monitoring to the source cell until receiving the RA Response.

Third Example : Source cell on Uplink  Transfer method

As described above, if radio link monitoring is restricted, the UE can stop downlink radio link monitoring for the source cell. However, according to the movement of the mobile station, the mobile station is in a state where the radio link quality of the source cell is bad (e.g., out-of-sync, radio link quality is lower than the threshold value Qout or wireless link quality is lower than the threshold value Qout) Reaching link failure criteria, etc.). In this case, the terminal may not receive downlink scheduling assignment and / or downlink data transmitted from the source base station. Alternatively, the terminal may not be able to transmit uplink data to the source base station, make a scheduling request for uplink data transmission, or be unable to transmit a buffer status report (BSR).

Meanwhile, a scheduling request procedure is used to request a radio resource for a new uplink transmission to the UE. When the Regular BSR is triggered but the uplink radio resource to transmit the BSR is not available, the scheduling request procedure is started. When a PUCCH for a scheduling request is configured in the UE, a scheduling request via the PUCCH can be transmitted. If not, the terminal performs a random access procedure.

It may not be desirable to retransmit the data or continue to attempt the scheduling request if the UE fails to transmit the uplink data with poor radio link quality of the source cell. Therefore, when applying the improved handover, one or more of the following methods can be applied.

In one example, the RRC message indicating an improved handover may be received (or while the timer is running) to limit the terminal from performing random access to the source cell. Or may limit, suspend or suspend random access to the source cell of the terminal. Specifically, for example, when receiving an RRC message indicating an improved handover (or while a timer is operating), the number of random access attempts to the source cell of the terminal may be limited. Specifically, for example, when receiving an RRC message indicating an improved handover (or while the timer is operating), the terminal can be prevented from performing the transmission of the scheduling request to the source cell. For example, when receiving an RRC message indicating a handover (or during a corresponding timer operation), the number of requests for scheduling requests for the source cell of the UE may be limited. Specifically, for example, when receiving an RRC message indicating an improved handover (or while the timer is operating), the scheduling request attempt is limited through the scheduling request attempt timer for the source cell of the UE It is possible. The source base station may instruct the terminal to include the indication information for that or the restriction information for instructing the terminal to perform this operation in the RRC connection reconfiguration message.

As another example, even if the UE experiences a radio link failure in the source cell, the target cell access attempt may succeed, so that the UE is switched to the RRC IDLE state until the random access fails on the target cell access or before the handover timer expires , The RRC connection reset procedure may not be performed. That is, when the UE detects both a radio link failure (or a specific condition in the source cell) in the source cell and a radio link failure (or a specific condition in the target cell, for example, a random access failure) in the target cell, Stored in the report, and initiating the RRC reset procedure.

In the above description, a processing method when a problem occurs in a radio link with a source cell or a target cell when the mobile station performs an improved handover operation has been described focusing on a specific embodiment.

Hereinafter, the improved handover operation of the terminal will be described in more detail.

Terminal Capability  Improved Information Handover  Instructions

For the RRC Connected terminal, the base station must accurately recognize the terminal capability to provide a suitable configuration for the terminal. Normally, the MME stores UE capability, which consists of UE Radio Access Capability and UE Core Network Capability.

For example, the UE Core Network Capability can be indicated by the UE through NAS signaling (attach procedure, etc.).

As another example, the UE Radio Access Capability can be transferred from the UE to the BS using the UE capability transfer procedure and transferred to the MME through the S1 interface. If the base station sends a UE capability inquiry message to the terminal, the terminal can receive the terminal capability information by responding to the UE capability information.

As another example of this, the UE Radio Access Capability can be indicated to the MME through the NAS signaling (attach procedure, etc.) by the UE and transmitted to the base station via the S1 interface.

If available, the MME transmits UE Radio Access Capability to the base station whenever the UE enters RRC Connected.

The terminal may instruct the base station to provide the terminal capability information indicating that it provides the conventional handover and another improved handover operation. The terminal capability information for the above-described improved handover may indicate whether to provide improved handover for a specific band or for a specific band combination, and may indicate whether to provide improved handover regardless of a band.

And the base station can instruct the terminal to perform the improved handover mode based on this.

The method of applying improved handover in consideration of the terminal capability information of the base station may use the following methods individually or in combination.

1st Example : target  Base station is improved Handover  How to Direct

The source base station may include the handover preparation information in the handover request message and transmit it to the target base station.

For example, the handover request message transmitted from the source base station to the target base station may include the above-described terminal capability information (or information indicating an improved handover mode). For example, information indicating an improved handover mode may be included in the handover preparation information. Or other information. When the target BS supports the improved handover function, the target BS prepares for the handover for the MS. The target base station sends a handover request confirmation message to the source base station.

The handover request confirmation message includes an RRC container to be transmitted to the UE as an RRC message for performing an improved handover. The RRC Container includes a new C-RNTI, a target eNB security algorithm identifier, a dedicated RACH preamble, a target eNB SIBs, and some other parameters. The RRC container described above can be delivered to the UE through an RRC connection reconfiguration message including mobility controlInfo. The target base station may further include information for instructing an improved handover to the RRC message to be transmitted to the terminal. Or the target base station may further include information for instructing the handover request confirmation message to indicate an improved handover.

The source base station performs integrity protection and ciphering necessary for the RRC message.

Upon receiving the RRC message including the information for instructing the improved handover, the UE can perform an improved handover operation.

The MS performs an improved handover operation and then sends an RRC Connection Reconfiguration Complete message to the target BS.

If the RRC message indicating normal handover not including information for instructing an improved handover is received, the terminal can perform a normal handover operation.

Second Example : Source base station is improved Handover  How to Direct

The source base station may include the handover preparation information in the handover request message and transmit it to the target base station.

For example, the handover request message transmitted from the source base station to the target base station may include the above-described terminal capability information (or information indicating an improved handover mode). For example, handover preparation information. Or other information.

If the target base station supports the improved handover function, the target base station prepares for an improved handover. The target base station sends a handover request confirmation message to the source base station.

The handover request confirmation message includes an RRC container to be transmitted to the UE as an RRC message for performing handover. The RRC Container includes a new C-RNTI, a target eNB security algorithm identifier, a dedicated RACH preamble, a target eNB SIBs, and some other parameters. The RRC container may further include information indicating an improved handover mode.

As another example, the handover request message transmitted from the source base station to the target base station may not include the above-described terminal capability information (or information indicating an improved handover mode). The target base station prepares for handover. The target base station sends a handover request confirmation message to the source base station.

The handover request confirmation message includes an RRC container to be transmitted to the UE as an RRC message for performing handover. The RRC Container includes a new C-RNTI, a target eNB security algorithm identifier, a dedicated RACH preamble, a target eNB SIBs, and some other parameters.

The RRC message is a connection RRC reconfiguration message including mobility controlInfo generated by the target base station and transmitted to the terminal through the source base station. The source base station performs integrity protection and ciphering necessary for the RRC message. The source base station may additionally include information for indicating an improved handover mode to the RRC message to be transmitted to the terminal. Or the information indicating the handover request acknowledgment message transmitted by the target base station or the improved handover on the RRC message, the source base station may additionally include information for instructing an improved handover to the RRC message to be transmitted to the terminal have. The source base station may include RRC container information for performing handover received from the target base station in an RRC message to be transmitted to the mobile station.

Upon receiving an RRC message including information for indicating an improved handover mode, the UE can perform an improved handover operation.

That is, the source base station can transmit a confirmation message to the source base station indicating that the mobile station succeeded in receiving the configuration added through the RRC message.

If the RRC message indicating normal handover not including information for instructing an improved handover is received, the terminal can perform a normal handover operation.

Hereinafter, a specific embodiment in which the MS and the BS perform the handover according to the improved handover mode will be described.

improved Handover  step

For example, the target base station may indicate an improved handover.

FIG. 3 is a diagram illustrating an example of a handover procedure according to an embodiment.

Referring to FIG. 3, the source base station 310 determines handover of the terminal 300 based on the measurement report and the RRM information (S300).

The source base station 310 sends a handover request message to the target base station 320 (S310).

Admission control may be performed in the target base station 320 according to the received E-RAB QoS information (S320).

The target base station 320 prepares for handover. Then, the base station 310 transmits a Handover Request Acknowledge message to the source base station 310 (S330). The handover request confirmation message includes an RRC container to be transmitted to the UE 300 as an RRC message for performing a handover.

The source base station 310 sends an RRCConnectionReconfiguration message including mobilityControlInformation to the UE 300 (S340).

The source base station 310 sends an SN STATUS TRANSFER message to the target base station 320 to convey the uplink PDCP SN receiver state and the downlink PDCP SN transmitter state (S350).

Upon receiving the RRCConnectionReconfiguration message including the mobilityControlInformation, the UE 300 performs synchronization with the target BS 320 and accesses the target cell through the RACH (S360). The target base station 320 may respond with uplink allocation and timing advance.

The terminal 300 may control the connection with the source base station 310 according to the random access procedure (S370).

For example, if the terminal 300 successfully accesses the target cell, the terminal 300 can disconnect the source base station 310.

As another example, if the terminal 300 successfully accesses the target cell, the terminal 300 may reconfigure / reset / process the entity connected to the source base station 310. For example, the terminal 300 resets the MCG MAC and, if configured, the SCG MAC. The UE 300 re-establishes PDCP for all the set RBs (Radio Bearers). The UE 300 re-establishes the MCG RLC for all configured RBs (Radio Bearers) and, if configured, the SCG RLC.

As another example, if the terminal 300 successfully accesses the target cell, the terminal 300 may apply the new configuration to the target base station 320. For example, the terminal 300 resets the MCG MAC and, if configured, the SCG MAC. The UE 300 re-establishes PDCP for all the set RBs (Radio Bearers). The UE 300 re-establishes the MCG RLC for all configured RBs (Radio Bearers) and, if configured, the SCG RLC.

The MS 300 sends an RRC Connection Reconfiguration Complete message to the target BS 320 (S380). When sending an RRC Connection Reconfiguration Complete message to the target base station 320, the terminal 300 may send a buffer status report together when possible

By sending a UE Context Release message, the target base station 320 informs the source base station 310 of the success of the HO and can trigger the release of the resource by the source base station 310 (S390).

4 is a diagram illustrating another example of a handover procedure according to an embodiment.

Referring to FIG. 4, the source base station 310 determines handover of the UE 300 based on the measurement report and RRM information (S400).

The source base station 310 sends a handover request message to the target base station 320 (S410).

Admission control may be performed in the target base station 320 according to the received E-RAB QoS information (S420).

The target base station 320 prepares for handover. Then, the base station 310 transmits a Handover Request Acknowledge message to the source base station 310 (S430). The handover request confirmation message includes an RRC container to be transmitted to the UE 300 as an RRC message for performing a handover.

The source base station 310 sends an RRCConnectionReconfiguration message including mobilityControlInformation to the terminal 300 (S440).

The MS 300 confirms that the MS 300 has received the improved handover message through the RRC Connection Reconfiguration Complete message (S445).

The source base station 310 sends an SN STATUS TRANSFER message to the target base station 320 to carry the uplink PDCP SN receiver state and the downlink PDCP SN transmitter state (S450). Alternatively, step S450 may be performed before step S445.

The terminal 300 performs synchronization with the target base station 320 and accesses the target cell through the RACH (S460). The target base station 320 may respond with uplink allocation and timing advance.

The terminal 300 may control the connection with the source base station 310 according to the random access procedure to the target cell (S470).

For example, if the terminal 300 successfully accesses the target cell, the terminal 300 can disconnect the source base station 310.

As another example, if the terminal 300 successfully accesses the target cell, the terminal 300 may reconfigure / reset / process the entity connected to the source base station 310. For example, the terminal 300 resets the MCG MAC and, if configured, the SCG MAC. The UE 300 re-establishes PDCP for all the set RBs (Radio Bearers). The UE 300 re-establishes the MCG RLC for all configured RBs (Radio Bearers) and, if configured, the SCG RLC.

As another example, if the terminal 300 successfully accesses the target cell, the terminal 300 may apply the new configuration to the target base station 320. For example, the terminal 300 resets the MCG MAC and, if configured, the SCG MAC. The UE 300 re-establishes PDCP for all the set RBs (Radio Bearers). The UE 300 re-establishes the MCG RLC for all configured RBs (Radio Bearers) and, if configured, the SCG RLC.

The MS 300 sends an RRC Connection Reconfiguration Complete message to the target BS 320 (S480). Or the terminal 300 transmits an RRC message indicating that the terminal 300 has succeeded in applying the new configuration to the target base station 320 It is also within the scope of the present invention that another term is used as a message containing information for indicating that the application has succeeded in this directed configuration). When sending an RRC Connection Reconfiguration Complete message (or an RRC message indicating successful application of a new configuration) to the target base station 320, the terminal 300 may send a buffer status report together if possible

By sending the UE Context Release message, the target base station 320 informs the source base station 310 of the success of the HO and can trigger the release of the resource by the source base station 310 (S490).

5 is a diagram illustrating another example of a handover procedure according to an embodiment. As an example, this may be the case when the source base station described above indicates an improved handover (or indicates an additional configuration).

Referring to FIG. 5, the source base station 310 determines handover of the terminal 300 based on the measurement report and the RRM information (S500).

The source base station 310 sends a handover request message to the target base station 320 (S510).

Admission control may be performed in the target base station 320 according to the received E-RAB QoS information (S520).

The target base station 320 prepares for handover. Then, the base station 310 transmits a Handover Request Acknowledge message to the source base station 310 (S530). The handover request confirmation message includes an RRC container to be transmitted to the UE 300 as an RRC message for performing a handover.

The source base station 310 sends an RRCConnection reconfiguration message including mobilityControlInformation to the terminal 300 (S540).

The source base station 310 sends an SN STATUS TRANSFER message to the target base station 320 to convey the uplink PDCP SN receiver state and the downlink PDCP SN transmitter state (S550). Alternatively, the step S550 may be performed after the step S560 or S565 described below.

The terminal 300 performs synchronization with the target base station 320 and accesses the target cell through the RACH (S560). The target base station 320 may respond with uplink allocation and timing advance.

For example, the MS 300 confirms that the MS 300 has received an improved handover message through the RRC Connection Reconfiguration Complete message (S565). Or that the terminal 300 has succeeded in random access to the target base station 320. Accordingly, the source base station 310 can stop the transmission of the downlink data to the terminal 300. The source base station 310 may send an SN Status Transfer message to the target base station 320.

As another example, the terminal 300 may transmit an RRC message indicating that the terminal 300 has succeeded in random access to the target base station 320 (denoted by an RA status report for convenience of description, ) Is included in the scope of the present invention as a message containing information for indicating that random access has been successfully completed). Accordingly, the source base station 310 can stop the transmission of the downlink data to the terminal 300. The source base station 310 may send an SN Status Transfer message to the target base station 320. The message transmitted from the source base station 310 to the target base station 320 includes information for indicating that the terminal 300 has succeeded in accessing the target base station 320 (or confirmation information on the information received from the target base station 320) . ≪ / RTI >

The terminal 300 may control the connection with the source base station 310 in accordance with the random access to the target cell (S570).

For example, if the terminal 300 successfully accesses the target cell, the terminal 300 can disconnect the source base station 310.

As another example, if the terminal 300 successfully accesses the target cell, the terminal 300 may reconfigure / reset / process the entity connected to the source base station 310. For example, the terminal 300 resets the MCG MAC and, if configured, the SCG MAC. The UE 300 re-establishes PDCP for all the set RBs (Radio Bearers). The UE 300 re-establishes the MCG RLC for all configured RBs (Radio Bearers) and, if configured, the SCG RLC.

As another example, if the terminal 300 successfully accesses the target cell, the terminal 300 may apply the new configuration to the target base station 320. For example, the terminal 300 resets the MCG MAC and, if configured, the SCG MAC. The UE 300 re-establishes PDCP for all the set RBs (Radio Bearers). The UE 300 re-establishes the MCG RLC for all configured RBs (Radio Bearers) and, if configured, the SCG RLC.

The MS 300 sends an RRC Connection Reconfiguration Complete message to the target BS 320 (S580). Or the terminal 300 transmits an RRC message indicating that the terminal 300 has succeeded in applying the new configuration to the target base station 320 It is also within the scope of the present invention that another term is used as a message containing information for indicating that the application has succeeded in this directed configuration). When sending an RRC Connection Reconfiguration Complete message (or an RRC message indicating successful application of a new configuration) to the target base station 320, the terminal 300 may send a buffer status report together if possible

By sending a UE Context Release message, the target base station 320 informs the source base station 310 of the success of the HO and can trigger the release of the resource by the source base station 310 (S590).

As described above, the present invention has the effect of stably changing the cell or changing the base station by reducing the data transmission interruption time due to the cell change or the base station change. In the embodiments described above, the order may be changed or some steps may be omitted as necessary.

On the other hand, the above-described improved handover can be applied to a terminal constituting a multi-connectivity (for example, dual connectivity). Hereinafter, as an example of an improved handover for reducing a data transmission interruption time due to a cell change or a change of a base station, a dual connectivity-based handover method and a handover method in which a network indicates handover conditions in the terminal, A description will be given of a method of performing over. This method can be applied based on maintaining the connection with the source base station during the handover described above.

Hereinafter, the master base station refers to a base station that makes an RRC connection with a terminal, and the secondary base station provides additional radio resources to the terminal. The terminal can configure dual connectivity with the master base station and the secondary base station.

For example, as the terminal having dual connectivity moves to the coverage edge of the master base station according to the movement, the current master base station can change the role of the current secondary base station and the base station. As another example, the current master base station can change the role of the current secondary base station and the base station according to the state change of the base station, with respect to the terminal configured with dual connectivity. In another example, the base station may wish to perform dual connectivity based mobility control. Handover from the source cell to the target cell is performed based on the dual connectivity, thereby performing the handover that minimizes the interruption. DC (Dual Connectivity) -capable terminal can transmit and receive to both base stations at the same time. Thus, data transmission can be performed with minimal interruption.

Hereinafter, for the sake of convenience of description, a change procedure between a base station and a multi-connectivity-based base station for a multi-connectivity capable terminal or a procedure for providing a dual connectivity-based mobility is referred to as a change procedure between base stations based on an MC (Multi Connectivity). This is for convenience of explanation only and can be replaced with another name.

Based on the change between the MC-based BSs, the MS must change the RRC connection with the existing master BS. For example, an existing secondary base station should be set as a new master base station to change / modify / set / reset / maintain / reconfigure the RRC connection. The existing secondary base station must generate a terminal configuration for operating as a new master base station and instruct it to the terminal.

Hereinafter, a specific method for this will be described. The methods described below may be used individually or in combination / combination. For convenience of description, the source base station, the old master base station, the old MeNB, and the new SeNB are denoted as source base stations in the MC-based base station change as needed. The source cell, source PCell, source MCG, old MCG cell, and old MCG PCell are denoted as source cells, and the target BS, old secondary BS, old SeNB, and new MeNB are denoted as target BSs. Target cell, target PCell, new MeNB cell, target base station PCell, new MCG, new MCG cell, and new MCG PCell are indicated as target cells.

How to send RRC connection confirmation directly to a new master base station

6 is a diagram illustrating an example of a base station changing procedure of a multi-connectivity terminal according to an exemplary embodiment.

Referring to FIG. 6, the source base station 610 determines a change between MC-based base stations (S600).

Source base station 610 issues an inter-base station interface message to send the necessary information to prepare for a change between MC based base stations on the target base station side. The source base station 610 instructs the target base station 620 to include the source base station 610 configuration to be used as a basis for the reconfiguration and the overall terminal 600 capability (S610). The inter-base station interface message for sending the necessary information to prepare for the change between MC based base stations described above includes a target cell ID, a new key value of the target base station 620, an RRC context, an AS-configuration, an E-RAB (or a 5G PDN / 5G radio bearer) context, the physical cell ID of the source cell, and short MAC-I.

The target base station 620 configures required resources according to the received radio bearer QoS information. The target base station 620 prepares for change between the MC-based base stations via L1 / L2. And transmits a request confirmation message to the source base station 610 (S620). The request confirmation message includes container information to be sent to the terminal 600 in an RRC message for performing a change between MC-based base stations. For example, the target base station 620 may include information for instructing the terminal 600 to make a change between MC-based base stations. The target base station 620 provides the Xn DL TNL address information for the source base station 610 split bearer.

If the source base station 610 approves the new configuration, the source base station 610 sends an RRC connection reconfiguration message containing the new radio resource configuration to the terminal 600 (S630).

The terminal 600 applies a new configuration and performs a random access procedure with the target base station (S640). Then, the RRC connection confirmation is transmitted to the previous secondary base station 620 that is a new master base station (S650).

If the received RRC reconnection message includes synchronization indication information to the previous secondary base station cell, the MS 600 performs synchronization with the target BS 620 cell (or the PCcell of the target BS or the PSCell of the target BS 620) . Otherwise, the random access procedure may be omitted.

The concrete operation of the terminal 600 receiving the RRC connection reconfiguration message for instructing the change between the MC-based base station will be described later.

The target base station 620 transmits a path change request message to a core network control plane entity CN-C 640 or an anchor base station if an anchor base station exists, .

The core network control plane entity 640 sends a user plane tunnel / flow / bearer modification request message to the core network user plane entity (CN-U) 630 (S670).

The core network user plane entity 630 switches the downlink data path to the target base station side. The core network user plane entity 630 sends one or more "end-marker" packets to the source base station 610 on the previous path. And may release the user plane resources to the source base station 610.

The core network user plane object 630 sends a user plane tunnel / flow / bearer modification response message to the core network control plane entity 640 (S680).

The core network control plane entity 640 sends a path change request confirmation message to the target base station 620 (690).

Hereinafter, the SN state transmission will be described. For convenience of explanation, the description will be made with reference to FIG. 6, but this also applies to FIG. 7 to be described below. In the prior art, the SN state transmission is performed after the source base station receives the handover request acknowledgment from the target base station or the master base station confirms the completion of the configuration for the dual connectivity configuration from the terminal and instructs the secondary base station to complete the reconfiguration.

However, in the case of changing between MC-based base stations, the DC-capable UE can perform transmission and reception simultaneously to two base stations. Thus, if a target base station connection is created, if a target base station MAC is created and a target base station radio bearer entity is created, data transmission can be performed with minimum interruption through two paths. Otherwise, if the target base station connection has already been created with the secondary connection, the reconfiguration of the source base station radio bearer entity and the target base station radio bearer entity can perform data transmission using the two paths with minimal interruption.

Therefore, the source base station first stops the data transmission and does not need to forward it to the target base station. After reconfiguration of the two radio paths is completed, the SN state transmission is performed, or during the path switching of the core network ) SN state transmission.

For example, in step S680, the source BS receiving the "end-marker" packet from the core network user plane may perform the SN state transmission. Thereby transmitting an uplink PDCP SN receiver state and a downlink PDCP SN transmission state to a radio bearer to which PDCP state preservation is applied. The uplink PDCP SN receiver state may include at least bit map information of the PDCP SN of the first missing UL SDU and the reception state of the out of sequence UL SDUs that the terminal needs to retransmit in the target cell. The downlink PDCP SN transmission state may indicate a next PDCP SN to be allocated to new SDUs for which the target base station does not yet have a PDCP SN. The source base station may perform data forwarding to the target base station.

As another example, the target base station receiving the data from the terminal in S640 or S650 may send a notification message to the source base station. The source base station can perform the SN state transmission. Thereby transmitting an uplink PDCP SN receiver state and a downlink PDCP SN transmission state to a radio bearer to which PDCP state preservation is applied.

MC based mobility control method

7 is a diagram illustrating another example of a base station changing procedure of a multi-connectivity terminal according to an embodiment.

Referring to FIG. 7, the source base station 710 determines a change between MC based base stations (MC based handover) (S700).

The source base station 710 issues an inter-base station interface message to the target base station 720 to send the necessary information to prepare for the change between the MC-based base stations (S710). The source base station 710 directs the target base station 720 to include the source base station 710 configuration to be used as the basis for the reconfiguration and the overall terminal 700 capabilities. The inter-base station interface message for sending the necessary information to prepare for the change between MC based base stations described above includes a target cell ID, a new key value of the target base station 720, an RRC context, an AS-configuration, an E-RAB (or a 5G PDN / 5G radio bearer) context, the physical cell ID of the source cell, and short MAC-I.

The target base station 720 configures required resources according to the received radio bearer QoS information. The target base station 720 prepares for change between the MC-based base stations via L1 / L2. And transmits a request confirmation message to the source base station 710 (S720). The request confirmation message includes a container to be sent to the terminal 700 in an RRC message for performing a change between MC-based base stations. The target base station 720 may provide with the Xn DL TNL address information for the source base station 710 split bearer. The target base station 720 may provide core network interface DL TNL address information for the target BS 720 split bearer. The target base station 720 may configure the SRB between the target base station 720 and the terminal 700 for direct RRC signaling through the air interface between the target base station 720 and the terminal 700. [ To this end, the MS 700 may include the SRB configuration information of the target BS 720 for transmitting the RRC message to the target BS 720.

If the source base station 710 approves the new configuration, the source base station 710 sends an RRC connection reconfiguration message including the new radio resource configuration to the terminal 700 (S730). For example, the source base station 710 may generate and transmit information for instructing the terminal 700 to change between the MC-based base stations.

The terminal 700 applies a new configuration. Then, the RRC connection confirmation is transmitted to the source base station 710 (S740).

The concrete operation of the terminal 700 that has received the RRC connection reconfiguration message instructing the change between the MC-based base station will be described later.

The source base station 710 informs the target base station 720 that the terminal 700 has successfully performed the reconfiguration procedure (S750).

If the received RRC reconnection message includes synchronization indication information to the previous secondary base station cell, the MS 700 performs synchronization with the target BS 720 cell (or the PCcell of the target BS or the PSCell of the target BS 720) (S760). Otherwise, step S760 may be omitted.

The target base station 720 transmits the path change request message to the core network control plane entity 740 or the anchor base station if the anchor base station exists (S770).

The core network control plane entity 740 sends a user plane tunnel / flow / bearer modification request message to the core network user plane entity 730 (S780).

The core network user plane entity 730 switches the downlink data path to the target base station 720 side. The core network user plane entity 730 sends one or more "end-marker" packets to the source base station 710 on the previous path. And may release the user plane resources to the source base station 710.

The core network user plane entity 730 sends a user plane tunnel / flow / bearer modification response message to the core network control plane entity 740 (S790).

The core network control plane entity 740 sends a path change request confirmation message to the target base station 720 (S795).

Hereinafter, the SN state transmission will be described. In the prior art, the SN state transmission is performed after the source base station receives the handover request acknowledgment from the target base station or the master base station confirms the completion of the configuration for the dual connectivity configuration from the terminal and instructs the secondary base station to complete the reconfiguration.

However, in the case of changing between MC-based base stations, the DC-capable UE can perform transmission and reception simultaneously to two base stations. Therefore, if the target base station connection is generated, when the target base station MAC is generated and the target base station radio bearer entity is created, the handover can be performed while minimizing the interruption through the two paths. Otherwise, in a state where the target base station connection is generated by the secondary connection, handover can be performed while minimizing the interruption through reconstruction (or release of the source base station radio resource) of the source base station radio bearer entity and the target base station radio bearer entity.

Therefore, it is possible to perform the SN state transmission after the reconfiguration of the two radio paths is completed, without the source base station first stopping the data transmission and forwarding to the target base station, or after the source base station radio resource release is completed SN state transmission during the release of the core network, or to perform the SN state transmission during the path switch of the core network (or after the path switch of the core network).

For example, the source base station receiving the "end-marker" packet from the core network user plane entity in step S790 described above may perform the SN state transmission. Thereby transmitting an uplink PDCP SN receiver state and a downlink PDCP SN transmission state to a radio bearer to which PDCP state preservation is applied. The uplink PDCP SN receiver state may include at least bit map information of the PDCP SN of the first missing UL SDU and the reception state of the out of sequence UL SDUs that the terminal needs to retransmit in the target cell. The downlink PDCP SN transmission state may indicate a next PDCP SN to be allocated to new SDUs for which the target base station does not yet have a PDCP SN. The source base station may perform data forwarding to the target base station

As another example, the target base station that has received the data from the terminal in S740 may send a notification message to the source base station. The source base station can perform the SN state transmission. Thereby transmitting an uplink PDCP SN receiver state and a downlink PDCP SN transmission state to a radio bearer to which PDCP state preservation is applied.

As another example, the target base station receiving data from the terminal in S740 or S760 may send a notification message to the source base station. The source base station can perform the SN state transmission. Thereby transmitting an uplink PDCP SN receiver state and a downlink PDCP SN transmission state to a radio bearer to which PDCP state preservation is applied.

As another example, the source base station which has received the release instruction from the target base station can instruct the terminal to release the source base station. And the source base station can perform the SN state transmission.

Hereinafter, the operation of the terminal receiving the RRC connection reconfiguration message will be described. It can be applied to the embodiment shown in Fig. 4 or Fig. 5 described above. Also, the present invention can be applied to other embodiments except for FIG. 4 or FIG.

1) source base station target  When the base station Dual Connectivity  If configured

The case where the source base station and the target base station are configured with dual connectivity before receiving the RRC message will be described.

The MS receiving the RRC connection reconfiguration message including the radio resource configuration indicating the change between the MC-based BS performs the following operation.

The MS receiving the information indicating the change between the MC-based BSs can maintain the connection of the source BS until the specific time of the MS.

The MS may consider the target BS cell (PSCell) as PCell at another specific time.

The UE reconfigures the PDCP entity with the target base station security configuration according to the PDCP configuration

The specific point in time or another specific point in time may include receiving an RRC reconfiguration message from the source base station, receiving a RRC message different from the RRC reconfiguration message received from the target base station, receiving a MAC CE from the target base station, After receiving the end market from the core network user plane path switching, it receives from the target base station, receives the PDCP control PDU of the target base station, and receives the end market from the core network user plane entity Reception of specific indication information, reception of a specific indication from the source base station, expiration of a specific timer, security update based on the target base station key, and any terminal operation time.

2) Single source base station Connectivity  If configured - source base station separation Bearer

A description will be given of the case of a terminal composed of a source base station and a single connectivity before receiving an RRC message.

The MS receiving the RRC connection reconfiguration message including the radio resource configuration indicating the change between the MC-based BS performs the following operation.

The MS receiving the information indicating the change between the MC-based BSs can maintain the connection of the source BS until the specific time of the MS.

If the RRC message received by the UE includes a new radio resource configuration for the source BS split bearer, it performs radio resource reconfiguration for the source BS detach bearer.

To this end, if the radio resource configuration for the received source base station split bearer includes a drb-Identity value to be further modified by the target base station and the DRB indicated by the drb-Identity is the MCG DRB (of the source base station) And establishes an RLC entity for the RLC entity.

If the target base station MAC is not part of the current terminal configuration, it creates a target base station MAC entity.

If the (primary) cell configuration of the target base station is included, a primer resister of the target base station is added according to the received configuration information.

The MS performs synchronization with the target base station cell (or the PC cell of the target base station or a specific cell of the target base station that is assumed to be the PSCell with the terminal). The terminal transmits the PRACH to the target base station cell.

The terminal maintains a dual connection with the source base station and the target base station cell and can transmit and receive data, respectively.

The MS may consider the target BS cell as PCell at another specific time.

The UE reconfigures the PDCP entity with the target base station security configuration according to the PDCP configuration.

 The terminal can release the source base station configuration at a specific point in time. For example, the base station can instruct the terminal to the rule / condition for this. In another example, the base station may send information to direct it. The aforementioned rules / conditions may be used to determine a specific threshold for the radio quality of the source cell, a specific timer, a radio link failure of the source cell, a threshold for radio link monitoring of the source cell (e.g., And the RLC entity may fail the retransmission of a certain number or more.

When releasing the source base station configuration, the UE can perform the PDCP data recovery procedure for the radio bearer in the source base station AM RLC mode. For this, when releasing the source base station RLC entity, it may indicate to the PDCP entity information about the PDCP PDUs that could not be successfully transmitted. The PDCP entity can retransmit it via a data recovery procedure.

The above-mentioned specific time point or another specific time point may be determined by receiving an RRC reconfiguration message from the source base station, an initial uplink transmission to the target base station, a RACH preamble transmission to the target base station, a first transmission of the PRACH to the target PCell, Receiving a RRC message different from the RRC reconfiguration message received from the source base station, receiving a MAC CE from the target base station, receiving PDCCH from the target base station, receiving a specific indication from the target base station, Receiving the end market according to the path switching from the target entity, receiving data from the target base station, receiving the PDCP control PDU of the target base station, receiving the specific indication information from the target base station receiving the end market according to the path switching from the core network user plane entity , sauce Specific indication from the station is received, a specific timer expires, after the security update of the target base station based on the key, it may be any one of reconfiguration, and any terminal operating point of the UE PDCP entity of the target base station security configuration.

3) Single source base station Connectivity  If configured - target  Base station separation Bearer

A description will be given of the case of a terminal composed of a source base station and a single connectivity before receiving an RRC message.

The MS receiving the RRC connection reconfiguration message including the radio resource configuration indicating the change between the MC-based BS performs the following operation.

The MS receiving the information indicating the change between the MC-based BSs may allow the MS to maintain the source BS / cell connection until a certain point in time.

If the RRC message received by the MS includes a new radio resource configuration for the target BS split bearer, it performs radio resource reconfiguration for the target BS BS bearer.

If the DRB indicated by the drb-Identity is the MCG DRB (of the source base station), then the target base station is notified of the DRB- And establishes an RLC entity for the RLC entity.

The UE reconfigures the PDCP entity with the target base station security configuration according to the PDCP configuration

If the target base station MAC is not part of the current terminal configuration, it creates a target base station MAC entity.

If the (primary) cell configuration of the target base station is included, a primer resister of the target base station is added according to the received configuration information.

The MS performs synchronization with the target base station cell (or the PCell of the target base station or a specific cell of the target base station). The terminal transmits the PRACH to the target base station cell.

The terminal maintains a dual connection with the source base station and the target base station cell and can transmit and receive data, respectively.

The MS may consider the target BS cell as PCell at another specific time.

The terminal can release the source base station configuration at a specific point in time. For example, the base station can instruct the terminal to the rule / condition for this. In another example, the base station may send information to direct it. The above-mentioned rule / condition is based on a specific threshold for the radio quality of the source cell (such as RRM measurement or beam measurement or CQI measurement value), a specific timer, a radio link failure of the source cell, Value (e.g., out of sync counts), and a retransmission failure of a certain number or more in the source cell RLC entity.

When releasing the source base station configuration, the UE can perform the PDCP data recovery procedure for the radio bearer in the source base station AM RLC mode. For this, when releasing the source base station RLC entity, it may indicate to the PDCP entity information about the PDCP PDUs that could not be successfully transmitted. The PDCP entity can retransmit it via a data recovery procedure.

The above-mentioned specific time point or another specific time point may be a time point for receiving the RRC reconfiguration message from the source base station, the initial uplink transmission to the target base station, the RACH preamble transmission to the target base station, the first transmission of the PRACH to the target PCELL, After receiving an RRC reconfiguration message and another RRC message, receiving a MAC CE from a target base station, receiving a PDCCH from a target base station, receiving a specific indication from a target base station, and switching a path from a core network user plane entity, Receiving a PDCP control PDU from a target base station, receiving a specific indication from a target BS receiving an end market according to a path switching from a core network user plane entity, receiving a specific indication from a source BS, expiring a specific timer, Security Later date, can be any of the reconfiguration of the UE PDCP entity of the target base station security configuration and any terminal operating point.

Hereinafter, a configuration of a source base station and a terminal capable of performing some or all of the operations of the above-described embodiments will be described with reference to the drawings.

8 is a diagram for explaining a terminal configuration according to an embodiment.

8, a UE 800 includes a receiver 830 for receiving a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing a service interruption from a source base station, It is possible to maintain the data transmission / reception operation with the source base station until a preset time, to confirm whether or not a connection failure has occurred with any of the source base station and the target base station, And a controller 810 for performing a connection failure processing operation when a connection failure occurs with one base station.

The receiver 830 receives the handover command from the source base station. The handover command may be included in the RRC connection reconfiguration message. The RRC connection reconfiguration message may include an RRC container. In one example, the RRC container includes mobility control information, and the mobility control information may include information indicating a handover mode for reducing service interruption. The RRC container may be generated by the target base station and delivered to the terminal via the source base station.

In addition, the RRC connection reconfiguration message may include restriction information for restricting the operation of the terminal when a connection failure with the source base station occurs. For example, the restriction information may include information instructing to deactivate the evaluation operation on the radio quality with the source base station, information instructing the terminal to suspend the RRC IDLE state entry or the RRC connection reestablishment operation until the handover failure time, Information for limiting the number and time of random access or scheduling requests to the base station, and information for limiting measurement reporting transmissions to the source base station.

The control unit 810 may proceed with the procedure of the improved handover mode based on the information indicating the improved handover mode included in the RRC connection reconfiguration message. For example, the control unit 810 can maintain the connection with the source base station until the preset time in the handover process. The predetermined timing may be a timing at which the random access preamble transmission to the target base station starts, a timing at which the random access response is received from the target base station, a timing at which the random access procedure with the target base station ends, And a time point at which an additional RRC connection reconfiguration message is received from the source base station. The preset time can be stored in advance for improved handover.

In addition, the controller 810 can check whether a connection failure has occurred with either the source base station or the target base station in the improved handover process. For example, the controller 810 may check whether a connection failure has occurred by checking whether the number of random access attempts to the target base station exceeds a preset reference number. As another example, the controller 810 may check whether a random access attempt time to the target base station has exceeded a predetermined time and whether a connection failure has occurred. The predetermined time may be set using a timer configured in the terminal. For example, the control unit 810 may determine that a connection failure with the target base station has occurred when the timer for confirming the connection failure has expired.

Meanwhile, the controller 810 may check whether a connection failure with the source base station occurs during the handover process. For example, the controller 810 may compare the connection quality state with the source base station to the reference quality state to determine whether a connection failure with the source base station has occurred.

If the restriction information is included, the control unit 810 may suspend the connection failure with the source base station without confirming up to a specific point. For example, the control unit 810 suspends the connection status monitoring with the source base station until the handover is completed, or until random access to the target base station succeeds or until receiving the random access response information from the target base station It is possible.

The control unit 810 may release the target base station configuration information for handover to the target base station when the connection failure with the target base station is confirmed. Or the control unit 810 may not monitor the connection failure with the source base station using the above-described limitation information. Alternatively, the control unit 810 may limit the random access to the scheduling request procedure or the source base station to a specific point in time or a specific number according to the restriction information when a connection failure with the source base station occurs.

In addition, the control unit 810 may control the overall operation of the terminal 800 to perform all or a part of each of the above-described embodiments.

The receiving unit 830 receives downlink control information, data, and messages from the source base station and the target base station through the corresponding channel.

The transmitting unit 820 may transmit information indicating a connection failure to the source base station when it is confirmed that the connection failure with the target base station has occurred. In addition, the transmitter 820 transmits uplink control information, data, and a message to the source base station and the target base station through the corresponding channel.

9 is a diagram for explaining a base station configuration according to an embodiment.

9, the source BS 900 includes a transmitter 920 for transmitting a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing a service disruption to the UE, A control unit 910 for maintaining a data transmission / reception operation with the terminal up to a predetermined time when the over mode is configured, and a reception unit 930 for receiving connection failure processing information in the handover process from the terminal.

The transmitter 920 can transmit the RRC container received from the target base station to the terminal. As described above, the RRC container includes mobility control information and may include information indicating an improved handover mode generated by the target base station. The RRC container is included in the RRC connection reconfiguration message and can be delivered to the UE. The UE receives the RRC connection reconfiguration message and performs the handover procedure according to the improved handover mode.

Meanwhile, the RRC connection reconfiguration message may include restriction information for restricting the operation of the UE when a connection failure with the UE occurs during the handover process. For example, the restriction information may include information for instructing the mobile station to deactivate the evaluation operation on the radio quality with the source base station, information for instructing the terminal to stop performing the RRC IDLE state entry or the RRC connection reestablishment operation until the handover failure time , Information for limiting the number and time of random access or scheduling requests to the source base station, and information for limiting the measurement reporting transmission of the terminal.

The control unit 910 may proceed with the procedure of the enhanced handover mode based on the information indicating the improved handover mode included in the RRC connection reconfiguration message. For example, the control unit 910 may maintain the connection with the terminal until the preset time in the handover process. The predetermined time may be a time at which the UE transmits the random access preamble to the target BS, a time at which the MS receives the random access response from the target BS, a time at which the random access procedure of the MS and the target BS is terminated, A time point at which the MS satisfies the handover condition to the target BS, and a time point at which the MS transmits an additional RRC connection reconfiguration message. The preset time can be stored in advance for improved handover.

In addition, the control unit 910 can control the overall base station 900 operation required to perform each of the above-described embodiments.

The connection failure processing information received by the receiving unit 930 may include information indicating a connection failure indicating that the terminal has failed to randomly access the target base station.

In addition, the transmitting unit 920 and the receiving unit 930 are used to transmit and receive signals, messages, and data necessary for carrying out the present invention to and from the terminal.

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and some of the standard documents is added to or contained in the scope of the present invention, as falling within the scope of the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (24)

A method for a handover of a terminal,
Receiving a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing a service interruption from a source base station;
Maintaining a data transmission / reception operation with the source base station until a predetermined time when the handover mode is configured, and checking whether a connection failure has occurred with any one of the source base station and the target base station; And
And performing a connection failure processing operation when a connection failure with any one of the source base station and the target base station occurs before the preset time. The method according to claim 1,
The predetermined point in time may be,
A time at which a random access response is received from the target base station, a time at which a random access procedure with the target base station ends, a time at which a connection with the source base station is released, A time point at which a handover condition to the base station is satisfied, and a time point at which an additional RRC connection reconfiguration message is received from the source base station. The method according to claim 1,
Wherein the step of verifying whether or not a connection failure with the target base station has occurred,
Based on at least one of the number of random access attempts to the target base station and the random access timer information. The method of claim 3,
Wherein the performing the connection failure processing operation comprises:
And to transmit information indicating a connection failure to the source base station when the occurrence of a connection failure with the target base station is confirmed. The method of claim 3,
Wherein the performing the connection failure processing operation comprises:
And releases the target base station configuration information for handover to the target base station. The method according to claim 1,
The RRC connection reconfiguration message comprises:
And limiting information for limiting operation of the terminal when a connection failure with the source base station occurs. The method according to claim 6,
The restriction information includes:
The RRC IDLE state entry or the RRC connection reestablishment operation to the handover failure time point, information indicating that the random access to the source base station Information for limiting the number and time of access or scheduling requests, and information for limiting measurement reporting transmissions to the source base station. A method for controlling handover of a terminal by a source base station,
Transmitting a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing service disruption to the terminal;
Maintaining a data transmission / reception operation with the terminal until a preset time when the handover mode is configured in the terminal; And
And receiving connection failure processing information from the terminal in the handover process. 9. The method of claim 8,
The predetermined point in time may be,
A time at which the MS transmits a random access preamble to the target BS, a time at which the MS receives a random access response from the target BS, a time at which the MS and the target BS complete the random access procedure, The time point of release, the time point at which the MS satisfies the handover condition to the target BS, and the time point at which the MS transmits an additional RRC connection reconfiguration message. 9. The method of claim 8,
The connection failure processing information includes:
And information indicating a connection failure indicating that the terminal has failed in random access to the target base station. 9. The method of claim 8,
The RRC connection reconfiguration message comprises:
And limit information for limiting an operation of the terminal when a connection failure with the terminal occurs in the handover process. 12. The method of claim 11,
The restriction information includes:
Information for instructing the mobile station to deactivate an evaluation operation on the radio quality with the source base station of the mobile station, information for instructing the mobile station to suspend the RRC IDLE state entry or the RRC connection reestablishment operation until the handover failure time, Information for limiting the number and time of random access or scheduling requests to the UE, and information for limiting the UE's measurement reporting transmission. In a terminal performing handover,
A receiving unit for receiving a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing a service interruption from a source base station; And
Wherein the mobile station maintains a data transmission / reception operation with the source base station by a predetermined time when the handover mode is configured, confirms whether a connection failure has occurred with any one of the source base station and the target base station,
And a controller for performing a connection failure processing operation when a connection failure with any one of the source base station and the target base station occurs before the preset time. 14. The method of claim 13,
The predetermined point in time may be,
A time at which a random access response is received from the target base station, a time at which a random access procedure with the target base station ends, a time at which a connection with the source base station is released, Wherein the mobile station is one of a time point at which a handover condition to the base station is satisfied and a time point at which an additional RRC connection reconfiguration message is received from the source base station. 14. The method of claim 13,
Wherein,
Whether a connection failure has occurred with the target base station based on at least one of the number of random access attempts to the target base station and the random access timer information. 16. The method of claim 15,
Wherein,
And controls to transmit information indicating a connection failure to the source base station when a connection failure with the target base station is confirmed. 16. The method of claim 15,
Wherein,
And releases the target base station configuration information for handover to the target base station to perform the connection failure processing operation. 14. The method of claim 13,
The RRC connection reconfiguration message comprises:
And restriction information for restricting operation of the terminal when a connection failure with the source base station occurs. 19. The method of claim 18,
The restriction information includes:
The RRC IDLE state entry or the RRC connection reestablishment operation to the handover failure time point, information indicating that the random access to the source base station Information for limiting the number and time of access or scheduling requests, and information for limiting transmission of measurement reports to the source base station. A source base station for controlling handover of a terminal,
A transmission unit for transmitting a Radio Resource Control (RRC) connection reconfiguration message including information indicating a handover mode for reducing a service interruption to a terminal;
A control unit for maintaining a data transmission / reception operation with the terminal until a preset time when the handover mode is configured in the terminal; And
And a receiver for receiving connection failure processing information from the terminal in the handover process. 21. The method of claim 20,
The predetermined point in time may be,
A time at which the MS transmits a random access preamble to the target BS, a time at which the MS receives a random access response from the target BS, a time at which the MS and the target BS complete the random access procedure, A release time point, a time point at which the MS satisfies a handover condition to the target BS, and a time point at which an additional RRC connection reconfiguration message is transmitted to the MS. 21. The method of claim 20,
The connection failure processing information includes:
Wherein the source base station includes information indicating a connection failure indicating that the terminal has failed to randomly access the target base station. 21. The method of claim 20,
The RRC connection reconfiguration message comprises:
And restriction information for restricting operation of the terminal when a connection failure with the terminal occurs in the handover process. 24. The method of claim 23,
The restriction information includes:
Information for instructing the mobile station to deactivate an evaluation operation on the radio quality with the source base station of the mobile station, information for instructing the mobile station to suspend the RRC IDLE state entry or the RRC connection reestablishment operation until the handover failure time, , Information for limiting the number and time of random access or scheduling requests to the UE, and information for limiting the UE's measurement reporting transmission.

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