KR20180016249A - Handover method - Google Patents

Abstract

The present invention relates to a handover method which allows a terminal to reduce or eliminate a data disconnection time when performing a handover from a source base station to a target base station. The handover method comprises the following steps of: the terminal receiving a handover command including uplink setting information from the source base station; the terminal transmitting a handover indication message to the source base station as an uplink semi-persistent scheduling (SPS) resource indicated by uplink SPS setting information while maintaining a connection with the source base station; the terminal disconnecting the connection with the source base station, after transmitting the handover indication message; and the terminal accessing the target base station.

Description

[0001] HANDOVER METHOD [0002]

The present invention relates to a handover method.

In a wireless communication system, when a terminal moves and a handover occurs, a data disconnection time occurs in which the terminal disconnects from the source base station and fails to receive data while connecting to the target base station. If the handover execution fails or a radio link error occurs during the handover, the data disconnection time becomes larger.

According to an exemplary embodiment of the present invention, when the MS handover from the source BS to the target BS, the data disconnection time can be reduced or eliminated. Also, in the dual connection scheme, the data disconnection time can be reduced or eliminated when the mobile station handover from the source secondary base station to the target secondary base station.

According to an embodiment of the present invention, a handover method of a terminal is provided. The handover method includes: receiving a handover command including uplink semi-persistent scheduling (SPS) setting information from a source base station; maintaining a connection with the source base station, Transmitting a handover indication message to the source base station using the uplink SPS resource indicated by the SPS setting information, disconnecting the source base station after transmitting the handover indication message, .

According to another embodiment of the present invention, a handover method of a terminal is provided. The handover method includes: receiving a secondary base station change command including uplink SPS configuration information from a master base station; receiving a downlink SPS setup information from the master base station, Sending a secondary base station change indication message to the source secondary base station as an SPS resource, disconnecting the source secondary base station after transmitting the secondary base station change indication message, and accessing the target secondary base station do.

According to an exemplary embodiment of the present invention, when the MS handover from the source BS to the target BS, the data disconnection time can be reduced or eliminated. Also, in the dual connection scheme, the data disconnection time can be reduced or eliminated when the mobile station handover from the source secondary base station to the target secondary base station.

1 is a diagram schematically illustrating a wireless communication system according to an embodiment of the present invention.
2A and 2B are diagrams illustrating handover in a wireless communication system according to an embodiment of the present invention.
3A and 3B are diagrams illustrating handover in a wireless communication system according to another embodiment of the present invention.
4 and 5 are diagrams illustrating a handover procedure in a conventional wireless communication system.
6a. 6B, 6C, 7, and 8 are views illustrating a handover method according to an embodiment of the present invention.
9, 10, 11, 12A, 12B, 13, 14, and 15 are diagrams illustrating a handover method, particularly a secondary base station changing method, according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, a terminal may be referred to as a user equipment (UE), a mobile station (MS), a mobile terminal (MT), an advanced mobile station (AMS) a high reliability mobile station (HR-MS), a subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a machine type communication device MTC device or the like and may include all or some of the functions of UE, MS, MT, AMS, HR-MS, SS, PSS,

Also, a base station (BS) includes a Node B, an evolved Node B, an eNB, a gNB, an advanced base station (ABS), a high reliability base station (BS), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) a relay station (RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, a high reliability relay station , HR-RS, a femto BS, a home Node B, a HNB, a pico BS, a macro BS, a micro base station (BS) the BS may be referred to as an NB, eNB, gNB, ABS, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR- There's also an included feature.

The expressions described in the singular may be interpreted as singular or plural unless an explicit expression such as "a" or "a" is used.

The wireless communication system according to the embodiment of the present invention can be applied to various wireless communication networks. For example, the wireless communication system may be applied to current wireless access technology (RAT) based wireless communication networks or 5G and later wireless communication networks. 3GPP is developing a new RAT-based 5G standard that satisfies the IMT-2020 requirements. This new RAT is called NR (New Radio). In the embodiment of the present invention, an NR-based wireless communication system will be described as an example for convenience of explanation, but the embodiment of the present invention is not limited thereto and can be applied to various wireless communication systems.

1 is a diagram schematically illustrating a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 1, a wireless communication system includes a plurality of base stations 110 and a plurality of terminals 120.

The base station 110 transmits a control channel indicating a downlink data channel and a resource region through which the corresponding downlink data channel is transmitted. The terminal 120 receives the control channel, identifies the resource region, receives the downlink data channel in the corresponding resource region, and decodes the data to be transmitted by the corresponding base station 110. The terminal 120 transmits the uplink data channel, and the base station 110 receives the uplink data channel and decodes the data to be transmitted by the terminal 120. In this case, the UE can confirm a resource region to transmit the uplink data channel through the control channel received from the base station 110.

The base station 110 includes a processor 111 and transceivers 112 and 113 and the transceiver includes a transmitter 112 and a receiver 113. The processor 111, the transmitter 112, and the receiver 113 may each be formed of physical hardware. The transmitter 112 and the receiver 113 may be formed of one hardware (e.g., chip). The processor 111, the transmitter 112, and the receiver 113 may all be formed of one hardware (e.g., chip).

The processor 111 implements an upper layer 111a and a physical layer 111b and executes commands necessary for the operation of the base station 110 and controls operations of the transmitter 112 and the receiver 113 . The transmitter 112 transmits the signal received from the physical layer 111b to the terminal 120 through the antenna and the receiver 113 receives the signal from the terminal 120 through the antenna and transmits the signal to the physical layer 111b do. Similarly, the terminal 120 includes a processor 121 and transceivers 122 and 123, and the transceiver includes a transmitter 122 and a receiver 123. The processor 121, the transmitter 122, and the receiver 123 may each be formed of physical hardware. The transmitter 122 and the receiver 123 may be formed of one piece of hardware (e.g., a chip). The processor 121, the transmitter 122, and the receiver 123 may all be formed of one hardware (e.g., chip).

The processor 121 implements the upper layer 121a and the physical layer 121b and executes commands necessary for the operation of the terminal 120 and controls the operations of the transmitter 112 and the receiver 113 . The transmitter 122 transmits the signal received from the physical layer 121b to the base station 110 via the antenna and the receiver 123 receives the signal from the base station 110 through the antenna and transmits the signal to the physical layer 121b do. The transmitter 122 and the receiver 123 may exchange signals with other terminals 120. [

2A and 2B are diagrams illustrating handover in a wireless communication system according to an embodiment of the present invention.

Referring to FIGS. 2A and 2B, when the source base station 210 determines handover, it transmits a handover command to the terminal 230 (S210). In order to perform handover, the terminal 230 determines a handover execution time while maintaining connection with the source base station 210 (S220), and performs handover based on the handover execution time (S230). In one embodiment, the terminal 230 disconnects from the source base station 210 based on the handover execution time and can access the target base station 220 (S230). For example, the terminal 230 transmits a handover indication message (Handover Indication) to the source base station 210 at the time of execution of the handover, disconnects the connection with the source base station 210 after transmitting the handover indication message . In another embodiment, the terminal 230 accesses the target base station 220 at the time of handover execution and disconnects the source base station 210 (S230). The source base station 210 may also forward data to the target base station 220.

3A and 3B are diagrams illustrating handover in a wireless communication system according to another embodiment of the present invention.

3A and 3B, when the master base station 310 determines to change the secondary base station in the dual connectivity configuration, it transmits a secondary base station change command (SeNB Change Command) to the terminal 330 (S310) . In order to change the secondary base station, the terminal 330 determines the execution timing of the secondary base station change while maintaining the connection with the source secondary base station 321 (S320), and changes the secondary base station , Handover) (S330). In one embodiment, the terminal 330 disconnects from the source secondary base station 321 based on the execution timing of the secondary base station change and can access the target secondary base station 322 (S330). For example, the terminal 330 transmits a secondary base station change indication message (SeNB Change Indication) to the source secondary base station 321 directly or via the master base station 310 to the source secondary base station 321, The connection with the source secondary base station 321 can be disconnected after transmitting the indication message. In another embodiment, the terminal 330 may access the target secondary base station 322 and disconnect the source secondary base station 321 at the time of performing the secondary base station change. The source secondary base station 321 also forwards the data to the target secondary base station 322 via the master base station 310.

4 and 5 are diagrams illustrating a handover procedure in a conventional wireless communication system. 4 and 5 illustrate a handover procedure in an LTE system among existing wireless communication systems. FIG. 5 illustrates a handover from a source secondary base station to a target secondary base station in a dual connection structure (i.e., ) Procedure.

Referring to FIG. 4, the source base station 210 configures a terminal measurement procedure (S405). That is, the source base station 210 transmits a measurement control message to the terminal 230 (S405). Accordingly, the terminal 230 measures the signal strength of the neighboring base stations and reports the measurement result to the source base station 210 through a measurement report message (S410). The source base station 210 determines handover based on the measurement report and the radio resource management (RRM) information managed by the source base station 210 (S415).

When the handover is determined, the source base station 210 proceeds with a handover preparation procedure (S420, S425, and S430).

Specifically, the source base station 210 transmits a handover request to the target base station 220 and transmits information necessary for handover preparation in the target base station 220 (S420). The target BS 220 performs admission control to reserve resources (S425), and transmits information about the resources prepared for the handover to the source BS 210 through a handover request ACK message. (S430).

Next, a handover execution procedure is performed (S435, S440, S445, S450).

The source base station 210 having prepared the handover with the target base station 220 transmits a handover command to the terminal 230 to instruct the terminal to perform handover (S435). The handover command is transmitted through an RRC connection reconfiguration message. The terminal 230 receiving the RRC connection reconfiguration message detaches from the previous cell, i.e., the source base station 210, and starts to synchronize with the new cell, i.e., the target base station 220, for connection. In this case, the terminal 230 stops transmitting and receiving packets with the source base station 210, and a handover interruption time starts.

After transmitting the RRC connection reconfiguration message, the source base station 210 buffers the packet received from the gateway and forwards it to the target base station 220. In addition, the source base station 210 transmits a sequence number (SN) status message to the target base station 220 (S440). The SN state delivery message may include a packet to be transmitted to the terminal 230 and a sequence number of a packet to be received from the terminal. For example, the SN status delivery message may include an uplink PDCP SN reception status (uplink packet data convergence protocol (SN) receiver status) and a downlink PDCP SN transmission status (downlink PDCP SN transmission status). The target base station 220 buffers packets received from the source base station 210.

After receiving the RRC connection reconfiguration message, the terminal 230 performs synchronization with the target base station 220 and accesses the target base station 220 via a random access channel (RACH) (S445). Target base station 220 transmits uplink allocation and timing advance to RACH response (RAR) (S450). Accordingly, if the terminal 230 successfully accesses the target BS 220, the MS 230 transmits a handover complete message to the target BS 220 (S455). The handover complete message is transmitted through the RRC connection reconfiguration complete message. The target BS 220 transmits the buffered downlink packet to the MS 230. When the MS 230 transmits the uplink packet, the target BS 220 receives the uplink packet and transmits the packet to the gateway 230 do.

Next, a handover completion procedure is performed (S460, S465, S470, S475, S480, S485, S490, S495).

The target base station 220 transmits a path switch request message to a mobility management entity (MME) to notify that the UE has changed the cell (S460). The MME sends a modify bearer request message to the gateway (S465). The gateway switches the downlink data path to the target base station 220 and transmits an end marker on the old path to the source base station 210 (S470). Accordingly, packets are exchanged through the path of the gateway and the target base station 220, which are newly constructed by the switch procedure. The source base station 210 also delivers an end marker to the target base station 220.

The gateway sends a modify bearer response message to the MME in response to the bearer change request message (S475). The MME transmits a path switch request ACK message to the target BS 220 in response to the path switch request message (S480). After receiving the path switch request acknowledgment, the target base station 220 sends a UE context release message to notify the source base station 210 of the handover success and trigger the release of the resource by the source base station 210 (S485). Upon receiving the UE context release message, the source base station 210 releases resources related to the terminal context (S490).

4, the messages of steps S405, S410, S420, S430, S435, S440, S455, S460, S465, S475, S480 and S485 may be sent with L3 (layer 3) signaling, Can be transmitted in L1 / L2 (layer 1 / layer 2) signaling.

In this conventional handover procedure, the source base station 210 transmits a handover command to the terminal 230, stops data transmission to the terminal, and transmits data to the target base station 220. After receiving the handover completion from the terminal 230, the target base station 220 starts data transmission to the terminal. Therefore, from when the source base station 210 stops transmitting data to the terminal 230 while transmitting the handover command to the time when the target base station 220 starts data transmission to the terminal 230 after receiving the handover completion May be the data disconnection time.

5, the master base station 310 transmits a secondary base station addition request (SeNB) addition request message to the target secondary base station 322 to inform the target secondary base station 322 of the terminal 330) by initiating a change of the secondary base station (S505). The target secondary base station 322 transmits a secondary base station addition request acknowledgment (SeNB addition request ACK) message to the master base station 310 in response to the secondary base station addition request (S510).

If the resource allocation of the target secondary base station 322 is successful, the master base station 310 transmits a secondary base station release request message (SeNB release request) message to the source secondary base station 321 to start releasing resources of the source secondary base station 321 (S515). If data forwarding is required, the master base station 310 provides the data forwarding address to the source secondary base station 321. The master base station 310 transmits an RRC connection reconfiguration message (i.e., a secondary base station change command) to the terminal 330 so that the terminal 330 can apply a new secondary base station configuration to the master base station 310 And then instructs a new configuration (i.e., secondary base station change) (S520). In response to the RRC connection reconfiguration message, the SS 330 transmits an RRC connection reconfiguration complete message to the master base station 310 (S525).

If the RRC connection reconfiguration procedure is successful, the master base station 310 transmits a message of completion of the secondary base station reconfiguration to the target secondary base station 322 (S530). The terminal 330 synchronizes with the target secondary base station 322 and performs a random access procedure (S535).

Upon receiving the secondary base station release request message, the source secondary base station 321 suspends data transmission to the terminal 330 and transmits an SN status transfer message to the target secondary base station 322 via the master base station 310. [ (S540a, S540b). The source secondary base station 321 buffers the packet transmitted from the gateway 340 and forwards the packet to the target secondary base station 322 via the master base station 310 in step S545. Data forwarding may be initiated after the source secondary base station 321 receives the secondary base station release request message.

Next, the master base station 310 triggers the path update to complete the handover, i.e., the secondary cell change. To this end, the master base station 310 transmits an E-RAB modification indication message to the MME 350 in step S550, and the MME 350 transmits bearer modification information to the gateway 340, Message (S555). A radio access bearer (RAB) is exemplified by an E-RAB (EUTRAN) (evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (RAB)). The gateway 340 receiving the bearer change message transmits an end marker packet on the old path to the source secondary base station 321 and the end marker packet is transmitted to the target secondary base station 322 via the master base station 310 (S560). The gateway 340 also switches the route to the target secondary base station 322 (S565). Data can be exchanged through the path between the newly configured gateway 340 and the target secondary base station 322 by the switch procedure.

The MME 350 transmits an E-RAB bearer confirmation message to the master base station 310 in response to the E-RAB change indication message at step S570. The master base station 310 transmits the E- (UE Context Release) message to notify the source secondary base station 321 of the success of the handover (S575).

In this conventional handover procedure, the source secondary base station 321 stops transmitting data to the terminal while receiving the secondary base station release request message, and forwards the data to the target secondary base station 322 via the master base station 310 do. The terminal 330 performs a random access procedure to the target secondary base station 322 to complete the handover, that is, the secondary cell change. Therefore, the time from when the source secondary base station 321 receives the secondary base station release request message to stop the data transmission to the terminal 330 to when the terminal 330 completes the random access procedure to the target secondary base station 322 This can be a data disconnect time.

Hereinafter, a handover method capable of reducing the data disconnection time will be described with reference to FIGS. 6A to 15. FIG.

6A, 7, and 8 are views illustrating a handover method according to an embodiment of the present invention.

Referring to FIG. 6A, the source base station 210 transmits a handover request message to the target base station 220 (S610). In some embodiments, prior to transmitting the handover request message, the handover decision procedure of the source base station 210 may be performed. In one embodiment, as described with reference to FIG. 4, the source base station 210 may determine a handover through a terminal measurement procedure (S405, S410, S415). In some embodiments, the handover request message may include information needed to prepare the handover at the target base station 220. In some embodiments, if the resource can be acknowledged by the target base station 220, the target base station 220 may perform admission control in dependence on the received information to increase the likelihood of successful handover have. In some embodiments, the target base station may configure the requested resources according to the received information and may include a terminal identifier (e.g., C-RNTI) and a random access channel (RACH) ) The preamble can be reserved.

After preparing the handover, the target BS 220 transmits a Handover Request Ack message to the source BS 210 (S620). In some embodiments, the handover request confirmation message may include a container to be sent to the terminal 230 in an RRC message to perform a handover. In one embodiment, the container may include a new terminal identifier (e.g., C-RNTI), a target base station security algorithm identifier for the selected security algorithm, a dedicated RACH preamble, and possibly other parameters. The source base station 210 having prepared the handover with the target base station 220 transmits a handover command to the terminal 230 to instruct the terminal to perform handover (S630). The handover command may be transmitted through an RRC message, i.e., an RRC Connection Reconfiguration message. In some embodiments, the RRC connection reconfiguration message may include mobility control information. In one embodiment, the RRC connection reconfiguration message may further include necessary parameters such as a new terminal identifier (e.g., C-RNTI), a target base station security algorithm identifier, and a dedicated RACH preamble. In some embodiments, the connection with the source base station 210 may be maintained until the terminal 230 performs the initial uplink transmission to the target base station 220.

The terminal 230 determines a handover execution time in a state of maintaining connection with the source base station 210, and performs handover based on the handover execution time. In some embodiments, if the terminal 230 is connectable to only one base station, the terminal 230 maintains a connection with the source base station 210 and transmits a handover indication to the source base station 210. [ Message (S640a), and performs handover (S650). After transmitting the handover indication message, the terminal 230 disconnects from the source base station 210, separates it from the source base station 210, and starts a connection with the target base station (S650). In one embodiment, the terminal 230 may transmit a handover indication message at the time of handover execution. For example, the UE 230 may determine a handover execution time in consideration of a physical random access channel (PRACH) configuration. In some embodiments, the terminal 230 may disconnect from the source base station 210 after receiving an acknowledgment (ACK) for the handover indication message from the source base station 210. In this case, the source base station 210 may determine that the terminal 230 transmits the ACK for the handover indication message as the handover point of the terminal 230.

In another embodiment, if the UE 230 does not receive a response to the handover indication message, i.e., ACK, the UE 230 can not establish a connection with the source BS 210 regardless of the response to the handover indication message. You can hang up. In another embodiment, if the terminal 230 can not transmit a handover indication message due to a bad channel environment, the terminal 230 may immediately perform a handover to the target base station 220 (i.e., the terminal 230 May terminate the connection with the source base station 210 at the time of the handover execution). In this case, the source base station 210 can infer the handover point of the terminal 230 based on the handover command transmitted to the terminal 230. For example, after the source base station 210 transmits a handover command to the terminal 230, if there is no data, control information or signal received from the terminal 230 for a predetermined time, the terminal 230 performs a handover It can be judged that it has been executed.

In some embodiments, the source base station 210 having received the handover indication message may transmit a handover indication message to the target base station 220 to inform the terminal of an immediate handover execution (S640b).

Upon receiving the handover instruction, the source base station 210 stops data transmission to the terminal 230 and may start forwarding data to the target base station 220 (S660). In some embodiments, as soon as the source base station 210 receives a handover indication message from the terminal 230 or transmits a handover indication message to the target base station 220, data forwarding may be initiated. In addition, the source base station 210 transmits an SN status transfer message to the target base station 220 (S660). In some embodiments, the SN state delivery message may include a packet to be sent to the terminal 230 and a sequence number value of the packet to be received from the terminal. In one embodiment, the SN state delivery message may include an uplink PDCP SN reception status (uplink Packet Data Convergence Protocol) SN receiver status and a downlink PDCP SN transmission status.

The UE 230 performs an access procedure such as a random access procedure to perform connection with the target BS 220 in steps S670 and S680 and then performs handover to the target BS 220 handover complete message (S690). The handover complete message may be transmitted via the RRC Connection Reconfiguration Complete message. In some embodiments, for access to the target base station 220, the terminal 230 performs synchronization with the target base station 220 and accesses the target base station 220 via the RACH (S670). The target base station 220 may transmit uplink allocation and timing advance to the RACH response (RAR) (S680).

In some embodiments, after the handover completion is delivered to the target base station 220, a handover completion procedure may be performed between the source base station 210, the target base station 220, the MME, and the gateway. In one embodiment, a handover completion procedure (S460, S465, S470, S475, S480, S485, S490, S495) may be performed as described with reference to FIG.

In this manner, instead of stopping the data transmission immediately after the source base station 210 transmits the handover command, the terminal stops the data transmission after receiving the handover instruction transmitted after determining the handover execution time, It is possible to eliminate the handover disconnection time until the handover execution time is determined after receiving the handover command.

Referring to FIG. 7, the terminal 230 can perform an access procedure to another base station while communicating with one base station. In this case, after the terminal 230 receives the handover command (S630), the terminal 230 can transmit the data forwarding request message to the source base station 210 while maintaining the connection with the source base station 210 (S631a). In one embodiment, the terminal 230 may send a data forwarding request message to the target base station 220 at the time of accessing the access procedure, for example, a random access procedure. Upon receiving the data forwarding request message, the source base station 210 starts data forwarding to the target base station 220 and continues data transmission to the terminal 230 (S631b).

The terminal 230 that has transmitted the data forwarding request message starts connection with the target base station 220 (S651a). The terminal 230 determines a handover execution time and performs a handover by performing an access procedure, for example, a random access procedure to the target base station 220 at a handover execution time (S671, S681). After the access procedure is completed, the terminal 230 transmits a handover indication message to the source base station 210 (S641a). In some embodiments, the source base station 210 receiving the handover indication message may forward the handover indication message to the target base station 220 (S641b). Upon receiving the handover indication message, the source base station 210 continues data forwarding to the target base station 220 and stops data transmission to the terminal 230 (S661). In addition, the source base station 210 transmits an SN status transfer message to the target base station 220 (S661). In another embodiment, the terminal may send a handover indication to the source base station 210 just prior to starting the access procedure.

After transmitting the handover indication message, the terminal disconnects from the source base station 210 and separates from the source base station 210 (S651b). The terminal 230 transmits a handover complete message to the target base station 220 upon completion of the access procedure (S691). The handover complete message may be transmitted via the RRC connection reconfiguration complete message.

In some embodiments, the data forwarding request procedures (S631a, S631b) may be omitted. For example, if there is little interface delay between base stations, the data forwarding request procedure can be skipped. In this case, the data forwarding may be started after the source base station 210 receives the handover indication message.

In some embodiments, the remaining operations may be performed as described with reference to FIG. 6A.

In this manner, since the connection with the source base station 210 is terminated after the terminal 230 completes the access procedure, the data disconnection time can be eliminated.

Referring to FIG. 8, in some embodiments, the terminal 230 may be connected to two or more base stations to enable communication. In this case, unlike the embodiment described with reference to FIG. 7, after the handover is completed and the terminal 230 transmits a handover completion message to the target base station 220 (S692) An instruction message can be transmitted (S642a). The handover completion can be delivered via the RRC connection reconfiguration complete message. That is, when the handover execution is completed and the terminal 230 first receives data from the target base station 220, it can transmit a handover indication message to the source base station 210. In some embodiments, the source base station 210 having received the handover indication message may forward the handover indication message to the target base station 220 (S642b). After transmitting the handover indication, the terminal disconnects from the source base station 210 and separates from the source base station 210 (S652).

Upon receiving the handover instruction, the source base station 210 continues data forwarding to the target base station 220 and stops data transmission to the terminal (S662). In addition, the source base station 210 transmits an SN status transfer message to the target base station 220 (S662). In another embodiment, the terminal may send a handover indication to the source base station 210 just prior to starting the access procedure. In yet another embodiment, the terminal may send a handover indication to the source base station 210 just before sending the RRC connection reconfiguration complete message to the target base station.

In some embodiments, the remainder of the operation may be performed as described with reference to Figures 6A and 7.

In this manner, since the connection with the source base station 210 is terminated after the terminal 230 completes the access procedure, the data disconnection time can be eliminated.

In some embodiments, the SN state delivery message may include an uplink SN state delivery message indicating the state of the uplink data and a downlink SN state delivery message indicating the state of the downlink data.

In one embodiment, in FIG. 7 or 8, when the source base station 210 receives the data forwarding request message (S631a) and forwards the data to the target base station 220, it may forward the uplink SN state forwarding message (S631b). In addition, after receiving the handover indication message (S641, S642) or after receiving the end marker, the source base station 210 may transmit the downlink SN state delivery message to the target base station 220 (S661, S662).

7 or 8, the source base station 210 receives the handover indication message (S641, S642), and then transmits the data forwarding request message to the target base station 220 When data is forwarded, an uplink SN state delivery message can be delivered (S661, S662). In addition, after receiving the handover indication message (S641, S642) or after receiving the end marker, the source base station 210 may transmit the downlink SN state delivery message to the target base station 220 (S661, S662).

Next, a modification to the embodiment described with reference to Figs. 6A, 7 and 8 will be described with reference to Figs. 6B and 6C. 6B and 6C, a modification of the handover method of FIG. 6A is described, but this modification may be applied to the embodiments described with reference to FIGS. 7 and 8. FIG.

6B and 6C are views showing a handover method according to another embodiment of the present invention, respectively.

In the embodiment described with reference to FIG. 6A, FIG. 7 or FIG. 8, when the terminal 230 transmits a handover indication message to the source base station 210, the source base station 210 determines that the terminal 230 has received the handover indication The uplink resource can be allocated so that the message can be transmitted. In order to allocate uplink resources, the UE 230 transmits a scheduling request (SR) to the source BS 210, and the source BS 210 transmits an uplink grant of the downlink control channel The uplink resource can be allocated to the terminal. There is an error probability of the downlink control channel at the cell boundary, and it takes time for the SR procedure, so there may be a problem in transmitting the handover signaling message fast.

In some embodiments, a handover indication message may be sent utilizing semi-persistent scheduling (SPS) resources. 6B, when the source base station 210 transmits a handover command, that is, an RRC connection reconfiguration message (S633), the source base station 210 sets the uplink SPS resource by transmitting the uplink SPS setting (SPS-ConfigUL) . In one embodiment, the RRC connection reconfiguration message may include uplink SPS configuration information. The terminal 230 receiving the uplink SPS setup information can transmit a handover indication message from the SPS resource indicated by the uplink SPS configuration. As described above, since the procedure for allocating the UL resource to the UE 230 through the SR procedure is not performed, the UE 230 can quickly transmit the handover indication message.

In one embodiment, the uplink SPS configuration information may follow the SPS-ConfigUL defined in the SPS-Config information element of 3GPP TS 36.331.

In one embodiment, the source base station 210 may activate the uplink SPS configuration in order for the terminal 230 to use the uplink SPS resources. The source base station 210 may explicitly activate the uplink SPS setting through a downlink assignment. The downlink allocation may be transmitted through a downlink control channel, for example, a physical downlink control channel. In this case, when the UE 230 receives the RRC connection reconfiguration message and receives the downlink allocation, the UE 230 regards the uplink SPS resource as active and can transmit the handover indication message using the uplink SPS resource. In another embodiment, the source base station 210 may implicitly activate the uplink SPS setting when transmitting an RRC connection reconfiguration message. In this case, when the MS 230 receives the RRC connection reconfiguration message, the MS 230 considers that the uplink SPS resource is active and transmits the handover indication message using the uplink SPS resource. As described above, by activating the uplink SPS resource at the time of transmitting the handover indication message, the uplink SPS resource may not be wasted.

In some embodiments, the random access procedure (S670, S680, S671, S681) may be omitted in the embodiment described with reference to Fig. 6A, Fig. 7 or Fig. In this case, as shown in FIG. 6C, the terminal 230 can access the target base station 220 by synchronizing with the target base station 220 without a random access procedure. In one embodiment, the random access procedure may be omitted if the terminal 230 knows the timing advance in advance, or if the accuracy of the timing advance is not a concern. In another embodiment, if the terminal 230 pre-calculates the timing advance of the target cell via pre-synchronization, the random access procedure may be omitted. In another embodiment, if the terminal 230 is able to infer the timing advance of the target cell according to the downlink reception of the source cell and the target cell, the random access procedure may be omitted. In this manner, when the random access procedure is omitted, the data disconnection time that may be caused by the random access procedure can be eliminated. In the future, the handover not performing the random access procedure is referred to as "RACH-less HO ".

In some embodiments, when the RACH-less HO is set, the source base station 210 transmits the handover command, i.e., the RRC connection reconfiguration message (S634), the uplink SPS setting (SPS-ConfigUL ) Information. In one embodiment, the RRC connection reconfiguration message may include uplink SPS configuration information of the target base station 220. In this case, as described with reference to FIG. 6B, the RRC connection reconfiguration message may further include uplink SPS configuration information of the source base station 210 so that the terminal 230 can transmit a handover indication message. Upon receiving the uplink SPS setting information of the target BS 220, the MS 230 may transmit a handover completion message, i.e., an RRC connection reconfiguration completion message, to the SPS resource indicated by the uplink SPS setting. Since the procedure for allocating the uplink resource to the UE 230 through the SR procedure or the random access procedure is not performed, the UE 230 can quickly transmit the RRC connection reconfiguration completion message.

In one embodiment, the uplink SPS configuration information of the target base station 220 may follow the SPS-ConfigUL defined in the SPS-Config information element of 3GPP TS 36.331.

In one embodiment, the target BS 220 transmits uplink SPS configuration information to the source BS 210 so that the source BS 210 can forward the uplink SPS configuration information of the target BS 220 to the MS 230 . In this case, the target BS 220 may transmit the uplink SPS configuration information through the handover request confirmation message.

In one embodiment, the target base station 220 may activate the uplink SPS settings in order for the terminal 230 to use the uplink SPS resources of the target base station 220. The target base station 210 can explicitly activate the uplink SPS setting of the target base station 220 through the downlink allocation. In another embodiment, the target base station 220 may implicitly activate the uplink SPS setting of the target base station 220 when receiving a handover indication message from the source base station 210.

The SPS resource utilization method described with reference to FIG. 6B or FIG. 6C may be applied to the embodiment described with reference to FIG. 7 or FIG.

An embodiment in which the data disconnection time due to handover (i.e., secondary base station change) in the following dual connection configuration can be reduced will be described with reference to Figs. 9 to 15. Fig.

9, 10 and 11 are views showing a handover method according to another embodiment of the present invention.

In some embodiments, control message transmission from the terminal 330 to the source secondary base station 321 may be possible. In this case, a handover method to be described with reference to Figs. 9 to 11 can be used. For example, the UE 330 may transmit a control message using an L2 (Layer 2) MAC control element or a control message using an L3 (layer 3) message.

Referring to FIG. 9, the master base station 310 transmits a secondary base station addition request (SeNB addition request) message to the target secondary base station 322 (S910). The target secondary base station 322 transmits a secondary base station addition request acknowledgment message to the master base station 310 (S920). In some embodiments, the secondary base station addition request message may comprise a secondary cell group (SCG) configuration of the previous secondary base station. In some embodiments, if forwarding is required, the target secondary base station 322 may provide the forwarding address to the master base station (S920).

Next, the master base station 310 transmits an RRC connection reconfiguration message to the terminal 330 to instruct the new configuration so that the terminal 330 can apply a new secondary base station configuration (i.e., (S930). After receiving the RRC connection reconfiguration message, the terminal 330 maintains a connection with the source secondary base station 321 until the secondary base station change is executed. In some embodiments, the source secondary base station 321 may continue to transmit downlink data to the terminal 330 until the terminal 330 performs the initial uplink transmission to the target secondary base station 322.

The terminal 330 transmits an RRC connection reconfiguration complete message to the master base station 310 (S940). If the RRC connection reconfiguration is successful, the master base station 310 transmits a message to the target secondary base station 322 to notify the target secondary base station 322 of the completion of the secondary base station reconfiguration (SNB reconfiguration complete) (S950).

The terminal 330 determines the execution timing of the secondary base station change while maintaining connection with the source secondary base station 321 and performs the secondary base station change based on the execution timing of the secondary base station change. In some embodiments, if the terminal 330 can only connect to one secondary base station, the terminal 330 determines a secondary base station change execution time and sends a secondary base station change indication (SeNB change indication) to the source secondary base station 321. [ (S960). In one embodiment, the terminal 330 may transmit a secondary base station change indication message at the time of execution of the secondary base station change. Therefore, the secondary base station change indication message can inform the source secondary base station 321 of the immediate secondary base station change execution of the terminal. For example, the terminal 330 can determine the time point at which the secondary base station change is performed in consideration of the PRACH configuration of the target secondary base station cell. In some embodiments, the terminal 330 may disconnect the source secondary base station 321 after receiving an ACK for the secondary base station change indication message from the source secondary base station 321. In this case, the source secondary base station 321 can determine that the terminal 330 transmits the ACK for the secondary base station change indication message as the secondary base station change point of the terminal 330.

In other embodiments, if the terminal 330 does not receive a response to the secondary base station change indication message, i.e., an ACK, the terminal 330 transmits the secondary base station change indication message to the source secondary base station 321 Can be disconnected. In another embodiment, if the terminal 330 can not transmit a secondary base station change indication message due to a bad channel environment, the terminal 330 may immediately perform a secondary base station change to the target secondary base station 322 (i.e., , The terminal 330 can immediately disconnect the source secondary base station 321 at the time of execution of the secondary base station change). In this case, the source base station 321 can infer the change point of the secondary base station of the terminal 330. For example, the source secondary base station 321 may determine that the terminal 330 has changed the secondary base station if there is no data, control information, or signal received from the terminal 330 for a predetermined time.

9, after the master base station 310 transmits a secondary base station reconfiguration completion message to the target secondary base station 322 (S950), the terminal 330 transmits a secondary base station change order message to the source secondary base station 321 (S960), the order of execution of steps S950 and S960 is not limited to this. For example, steps S950 and S960 may be executed simultaneously, and step S950 may be executed after step S960 is executed.

After transmitting the secondary base station change indication message in step S960, the terminal 330 disconnects from the source secondary base station 321 and disconnects from the source secondary base station 321 in step S970a. Connection is started (S970b). Upon receiving the secondary base station change instruction, the source secondary base station 321 stops data transmission to the terminal 330 and starts data forwarding to the target secondary base station 322 via the master base station 310 (S980a, S980b ). In some embodiments, data forwarding may be initiated as soon as the source secondary base station 321 receives the secondary base station change indication message. In addition, the source secondary base station 321 transmits an SN status transfer message to the target secondary base station 322 via the master base station 310 (S980a, S980b). The terminal 330 synchronizes with the target secondary base station 322 and performs an access procedure with the target secondary base station 322, for example, a random access procedure, for connection with the target secondary base station 322 (S990) . Although FIG. 9 shows that the random access procedure is performed after starting data forwarding (S980a, S980b) (S990), the order of execution of steps S980a, S980b, and S990 is not limited to this. For example, steps S980a, S980b and S990 may be executed simultaneously, and steps S980a and S980b may be executed after step S990 is executed.

In some embodiments, after the secondary base station change is performed to the target secondary base station 322, a path update procedure is performed between the master base station 310, the source secondary base station 321, the target secondary base station 322, the MME and the gateway . In one embodiment, route update procedures (S555, S560, S565, S570, S575, S580) may be performed as described with reference to FIG.

In this manner, the source secondary base station 321 does not stop the data transmission to the terminal 330 before the master base station 310 transmits the RRC connection reconfiguration message, but after the terminal 330 determines the execution point of the secondary base station change The data transmission is stopped after receiving the transmitted secondary base station change instruction, so that the handover disconnection time can be reduced.

Referring to FIG. 10, the terminal 330 can perform an access procedure, for example, a random access procedure, to another secondary base station while communicating with one secondary base station. In this case, after receiving the RRC connection reconfiguration message (secondary base station change command) (S930), the terminal 330 maintains the connection with the source secondary base station 321 and transmits a data forwarding request message to the source secondary base station 321 (S931). In one embodiment, the terminal 330 may send a data forwarding request message at the time of performing the random access procedure to the target secondary base station 322. Upon receiving the data forwarding request message, the source secondary base station 321 starts data forwarding to the target secondary base station 322 via the master base station 310 and continues data transmission to the terminal 330 (S931a, S931b).

The terminal 330 that has transmitted the data forwarding request message starts connection with the target secondary base station 322 (S971b). The terminal 330 determines the execution timing of the secondary base station change and performs the random access procedure to the target secondary base station 322 at the time of execution of the secondary base station change to execute the secondary base station change (S991). After the random access procedure is completed, the terminal 330 transmits a secondary base station change instruction message to the source secondary base station 321 (S961). Upon receiving the secondary base station change indication message, the source secondary base station 321 stops data transmission to the terminal 330 and continues data forwarding to the target secondary base station 322 (S981a, S981b). In addition, the source secondary base station 321 transmits an SN status transfer message to the target secondary base station 322 via the master base station 310 (S981a, S981b). In another embodiment, the terminal 330 may send a secondary base station change indication message to the source secondary base station 321 just prior to starting the random access procedure.

After transmitting the secondary base station change instruction, the terminal 330 disconnects from the source secondary base station 321 and disconnects from the source secondary base station 321 (S971a). In step S941, the MS 330 transmits an RRC connection reconfiguration completion message to the master BS 310 in step S941. The MS 330 transmits the RRC connection reconfiguration completion message to the target secondary BS 322 And transmits a secondary base station reconfiguration completion message (S951).

In some embodiments, the remaining operations may be performed as described with reference to FIG.

In some embodiments, the data forwarding request procedures (S931, S931a, S931b) may be omitted. For example, if there is little interface delay between base stations, the data forwarding request procedure can be skipped. In this case, the data forwarding may be started after the source secondary base station 321 receives the handover indication message.

In this way, since the connection with the source secondary base station 321 is disconnected after the terminal 330 completes the access procedure, the data disconnect time can be eliminated.

Referring to FIG. 11, the terminal 330 may be connected to two or more secondary base stations to enable communication. In this case, unlike the embodiment described with reference to FIG. 10, the terminal 330 performs an access procedure (S991) and transmits an RRC connection reconfiguration complete message (i.e., completion of secondary base station change) to the master base station 310 (S942), the secondary base station change instruction message can be transmitted to the source secondary base station 321 (S962). Upon receiving the connection reconfiguration completion message, the master base station 310 transmits the secondary base station reconfiguration completion message to the target secondary base station 322 (S952). That is, when the execution of the secondary base station change is completed and the terminal 330 first receives data from the target secondary base station 332, the secondary base station change request message can be transmitted to the source secondary base station 321. After transmitting the secondary base station change instruction, the terminal disconnects from the source secondary base station 321 and disconnects from the source secondary base station 321 (S972). Upon receiving the secondary base station change instruction, the source secondary base station 321 stops data transmission to the terminal 330 and continues data forwarding to the target secondary base station 322 (S982a, S982b). In addition, the source secondary base station 321 transmits an SN status transfer message to the target secondary base station 322 via the master base station 310 (S982a, S982b). In another embodiment, the terminal 330 may send a secondary base station change indication to the source secondary base station 321 just prior to starting the access procedure. In yet another embodiment, the terminal 330 may send a secondary base station change indication to the source secondary base station 321 just before sending the RRC connection reconfiguration complete message to the target secondary base station 322.

In some embodiments, the remaining operations may be performed as described with reference to Figures 9 and 10. [

In this way, since the connection with the source secondary base station 321 is disconnected after the terminal 330 completes the access procedure, the data disconnect time can be eliminated.

In some embodiments, the SN state delivery message may include an uplink SN state delivery message indicating the state of the uplink data and a downlink SN state delivery message indicating the state of the downlink data.

10 or 11, when the source secondary base station 321 receives the data forwarding request message (S931) and forwards the data to the target secondary base station 322, it transmits an uplink SN state forwarding message (S931a, S931b). In addition, after receiving the secondary base station change instruction message (S961, S962) or after receiving the end marker, the source secondary base station 321 can transmit the downlink SN state delivery message to the target secondary base station 322 (S981a, S981b, S982a, S982b).

10 or 11, the source secondary base station 321 receives the secondary base station change request message (S961, S962), and then transmits the data forwarding request message to the target secondary base station 322, the uplink SN state delivery message can be delivered (S981a, S981b, S982a, S982b). In addition, after receiving the secondary base station change instruction message (S961, S962) or after receiving the end marker, the source secondary base station 321 can transmit the downlink SN state delivery message to the target secondary base station 322 (S981a, S981b, S982a, S982b).

In some embodiments, control message transmission from the terminal 330 to the source secondary base station 321 may not be possible. In this case, the handover method described with reference to Figs. 12A to 15 can be used. For example, when the terminal 330 transmits a control message using the L3 (layer 3) message, it may be possible to transmit the L3 message only to the master base station 310. [

12A, 13, 14, and 15 are diagrams illustrating a handover method according to another embodiment of the present invention.

12A, when the terminal 330 can connect to only one secondary base station, the terminal 330 transmits an RRC connection reconfiguration complete (RRC connection reconfiguration complete) message to the master base station 310 at the time of performing the secondary base station change, ) Message to the master base station 310 (S943). The master base station 310 having received the RRC connection reconfiguration completion message transmits a SeNB reconfiguration complete message to the target secondary base station 322 in step S953 and transmits a secondary base station change instruction SeNB change indication message (S963). Therefore, the secondary base station change indication message can inform the source secondary base station 321 of the immediate secondary base station change execution of the terminal. For example, the terminal 330 can determine the execution timing of the secondary base station change considering the PRACH configuration of the target secondary base station cell. 12A, after the master base station 310 transmits a secondary base station reconfiguration completion message to the target secondary base station 322 (S953), the terminal 330 transmits a secondary base station change order message to the source secondary base station 321 (S963), the order of execution of steps S953 and S963 is not limited to this. For example, steps S953 and S963 may be executed simultaneously, and step S953 may be executed after step S963 is executed.

In some embodiments, the terminal 330 may separately transmit a secondary base station change indication message to the master base station 310. The master base station 310 having received the secondary base station change instruction message from the terminal 330 may forward the message to the source secondary base station 310 (S963).

After transmitting the RRC connection reconfiguration completion message (S943), the terminal 330 disconnects from the source secondary base station 321 and separates from the source secondary base station 321 (S970).

In some embodiments, the remaining operations may be performed as described with reference to FIG.

13, when the terminal 330 can connect to only one secondary base station, the terminal 330 transmits a secondary base station change indication (SeNB change indication) to the master base station 310 at the time of performing the secondary base station change, (S964a), and the master base station 310 having received the message transmits the secondary base station change instruction message to the source secondary base station 321 (S964b). Therefore, the secondary base station change indication message can inform the source secondary base station 321 of the immediate secondary base station change execution of the terminal. For example, the terminal 330 can determine the execution timing of the secondary base station change considering the PRACH configuration of the target secondary base station cell.

Upon receiving the secondary base station change instruction, the source secondary base station 321 stops data transmission to the terminal 330 and starts data forwarding to the target secondary base station 322 via the master base station 310 (S980a, S980b ). The source secondary base station 321 transmits an SN status transfer message to the target secondary base station 322 via the master base station 310 (S980a, S980b). After transmitting the secondary base station change instruction message (S964a), the terminal 330 disconnects from the source secondary base station 321 and disconnects from the source secondary base station 321 (S970a). Also, the terminal 330 performs an access procedure with the target secondary base station 322, for example, a random access procedure (S990).

After completing the access procedure (S990), the SS 330 transmits an RRC connection reconfiguration complete message to the master base station 310 (S944), and transmits the RRC connection reconfiguration complete message to the master base station 310 transmits a secondary base station reconfiguration complete message (SeNB reconfiguration complete) message to the target secondary base station 322 (S954).

In some embodiments, the remaining operations may be performed as described with reference to FIG.

12A or 13, even if the terminal 330 can not directly transmit the control message to the source secondary base station 321, the source secondary base station 321 transmits the control message to the secondary base station 321 via the master base station 310. [ A change instruction message can be transmitted. The source secondary base station 321 does not stop the data transmission to the terminal 330 before the master base station 310 transmits the RRC connection reconfiguration message but the data transmission after the terminal 330 determines the execution point of the secondary base station change The handover disconnection time can be reduced.

Referring to FIG. 14, the terminal 330 can perform an access procedure, for example, a random access procedure, to another secondary base station while communicating with one secondary base station. In this case, after the terminal 330 receives the RRC connection reconfiguration message (secondary base station change command) (S930), the terminal 330 maintains the connection with the source secondary base station 321 and transmits a data forwarding request message to the master base station 310 (S935a), and the master base station 310 having received the data forwarding request message can forward the data forwarding request message to the source secondary base station 321 (S935b). In one embodiment, the terminal 330 may send a data forwarding request message at the time of performing the random access procedure to the target secondary base station 322. Upon receiving the data forwarding request message, the source secondary base station 321 starts data forwarding to the target secondary base station 322 via the master base station 310 and continues data transmission to the terminal 330 (S931a, S931b).

The terminal 330 that has transmitted the data forwarding request message performs the random access procedure to the target secondary base station 322 to perform the secondary base station change (S991). After completing the random access procedure, the terminal 330 transmits a secondary base station change indication message to the master base station 321 (S965a), and the master base station 321 receives the secondary base station change indication message from the source secondary base station 321 (S965b). Upon receiving the secondary base station change indication message, the source secondary base station 321 stops data transmission to the terminal 330 and continues data forwarding to the target secondary base station 322 (S981a, S981b). In addition, the source secondary base station 321 transmits an SN status transfer message to the target secondary base station 322 via the master base station 310 (S981a, S981b). In another embodiment, the terminal 330 may send a secondary base station change indication message to the source secondary base station 321 just prior to starting the random access procedure.

After transmitting the secondary base station change instruction, the terminal 330 disconnects from the source secondary base station 321 and disconnects from the source secondary base station 321 (S971a). In some embodiments, the remaining operations may be performed as described with reference to Figures 9 and 10. [

In this manner, even when the terminal 330 can not directly transmit the control message to the source secondary base station 321, the data forwarding request message and the secondary base station change request message are transmitted to the source secondary base station 321 through the master base station 310 Lt; / RTI > In addition, since the terminal 330 disconnects the source secondary base station 321 after completing the access procedure, the data disconnection time can be eliminated.

Referring to FIG. 15, the terminal 330 may be connected to two or more secondary base stations to enable communication. In this case, unlike the embodiment described with reference to FIG. 14, when the terminal 330 performs the access procedure (S991) and transmits the RRC connection reconfiguration complete message (i.e., the completion of the secondary base station change) to the master base station 310 Thereafter, in step S942, the secondary base station change instruction message may be transmitted to the master base station 310 (S966a). Upon receiving the RRC connection reconfiguration completion message, the master base station 310 transmits a secondary base station reconfiguration completion message to the target secondary base station 322 (S952). That is, when the terminal 330 has received the data from the target secondary base station 332 for the first time after the execution of the secondary base station change is completed, the secondary base station change request message can be transmitted to the master base station 310. The master base station 310 having received the secondary base station change instruction message transmits it to the source secondary base station 321 (S966b). After transmitting the secondary base station change instruction, the terminal disconnects from the source secondary base station 321 and separates from the source secondary base station 321 (S972).

Upon receiving the secondary base station change instruction, the source secondary base station 321 stops data transmission to the terminal 330 and continues data forwarding to the target secondary base station 322 (S982a, S982b). In addition, the source secondary base station 321 transmits an SN status transfer message to the target secondary base station 322 via the master base station 310 (S982a, S982b). In another embodiment, the terminal 330 may send a secondary base station change indication to the source secondary base station 321 just prior to starting the access procedure. In yet another embodiment, the terminal 330 may send a secondary base station change indication to the source secondary base station 321 just before sending the RRC connection reconfiguration complete message to the target secondary base station 322.

In some embodiments, the remaining operations may be performed as described with reference to Figures 9 and 10. [

In this manner, even when the terminal 330 can not directly transmit the control message to the source secondary base station 321, the data forwarding request message and the secondary base station change request message are transmitted to the source secondary base station 321 through the master base station 310 Lt; / RTI > In addition, since the terminal 330 disconnects the source secondary base station 321 after completing the access procedure, the data disconnection time can be eliminated.

Next, a modified example of the embodiment described with reference to Figs. 9, 10, 11, 12A, 13, 14, and 15 will be described with reference to Fig. 12B. 12A and 12B, a modification of the handover method of FIG. 12A is described. However, this modification may be applied to the embodiments described with reference to FIGS. 9, 10, 11, 13, 14, and 15. FIG.

12B is a diagram illustrating a handover method according to another embodiment of the present invention.

In the embodiment described with reference to FIGS. 9, 10, 11, 12A, 13, 14, or 15, the terminal 330 may transmit a secondary base station change indication message using SPS resources. 12B, the master base station 310 transmits uplink SPS resources by transmitting uplink SPS configuration information (SPS-ConfigUL) information when transmitting a secondary base station change command, i.e., an RRC connection reconfiguration message (S937) Can be set. In one embodiment, the RRC connection reconfiguration message may include uplink SPS configuration information. Upon receiving the uplink SPS configuration information, the SS 330 can transmit a handover indication message from the SPS resource indicated by the uplink SPS configuration (S967). Since the procedure for allocating the uplink resources to the SS 330 is not performed through the SR procedure, the SS 330 can quickly transmit the secondary BS change indication message.

In some embodiments, the SS 330 may transmit a secondary base station change completion message, i.e., an RRC connection reconfiguration completion message, using the uplink SPS resource (S943).

9, 10 or 11, when the terminal 330 transmits a secondary base station change indication message to the source secondary base station 321, the uplink SPS resource is transmitted to the source secondary base station 321 ) ≪ / RTI > In another embodiment, when the terminal 330 transmits a secondary base station change indication message to the master base station 310 as shown in FIGS. 12A, 13, 14, or 15, the uplink SPS resource is transmitted to the master base station 310). ≪ / RTI >

In one embodiment, the uplink SPS configuration information may follow the SPS-ConfigUL defined in the SPS-Config information element of 3GPP TS 36.331.

In one embodiment, the master base station 310 may activate the uplink SPS configuration in order for the terminal 330 to use the uplink SPS resources. The master base station 310 can explicitly activate the uplink SPS setting through downlink allocation. In this case, when the UE 330 receives the RRC connection reconfiguration message and receives the downlink allocation, it may consider the uplink SPS resource to be active and transmit the secondary base station change indication message using the uplink SPS resource. In another embodiment, the master base station 310 may implicitly activate the uplink SPS setting when transmitting an RRC connection reconfiguration message. In this case, when the terminal 330 receives the RRC connection reconfiguration message, it may regard the uplink SPS resource as active when transmitting the secondary base station change indication message and may transmit the handover indication message using the uplink SPS resource . As described above, the uplink SPS resources are not wasted by activating the uplink SPS resources at the time of transmitting the secondary BS change indication message.

The SPS resource utilization method described with reference to FIG. 12B may be applied to the embodiments described with reference to FIGS. 9, 10, 11, 13, 14, or 15. FIG.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (1)

A handover method of a terminal,
Receiving a handover command including uplink semi-persistent scheduling (SPS) setting information from a source base station,
Transmitting a handover indication message to the source base station from the uplink SPS resource indicated by the uplink SPS configuration information while maintaining a connection with the source base station,
Disconnecting the connection with the source base station after transmitting the handover indication message, and
Accessing the target base station
/ RTI >

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