KR102322495B1 - method and apparatus for transmitting and receiving system information in mobile communication system - Google Patents

Abstract

Through the steps of establishing a connection with the primary base station, and receiving an RRC connection reconfiguration message including system information of the SCG cell controlled by the secondary base station connected to the primary base station by non-ideal backhaul from the primary base station, the secondary base station Control by a primary base station through a method of receiving system information of A method is provided for sharing a frame offset between an MCG that is used and an SCG controlled by a secondary base station connected to a primary base station and a non-ideal backhaul.

Description

Method and apparatus for transmitting and receiving system information in a mobile communication system {method and apparatus for transmitting and receiving system information in mobile communication system}

The present invention relates to a method and apparatus for transmitting and receiving system information in a dual connectivity mobile communication system in which both a primary base station and a secondary base station are connected to a mobile terminal.

^{3GPP LTE / SAE (3 rd generation} partnership project long term evolution / system architecture evolution) under way in the standardization of improved small cell (small cell enhancement, SCE) technology. Small cell enhancement technology is a technology that densely arranges small cells in multiple layers in a macro cell-based cellular network and increases the capacity of a wireless network through close cooperation between macro cell base stations and small cell base stations. The purpose of the small cell enhancement technology is to accommodate explosively increasing traffic by increasing spectral efficiency per unit area by densely arranging high-density small cells, to secure coverage essential for mobile communication, and to enable efficient mobility management. To achieve this purpose, 3GPP RAN (radio access network) is a small cell in E-UTRA (evolved-UMTS terrestrial radio access) and E-UTRAN (evolved-UMTS terrestrial radio access network) scenarios and requirements for improvement. was discussed, and a physical layer and upper layer study item (SI) for small cell improvement was approved at the RAN meeting in December 2012.

For small cell improvement of cellular network considered in 3GPP, three scenarios related to small cell deployment, spectrum, traffic, and compatibility with previous standards were defined, and technical issues and solutions for the defined scenario were discussed. Scenario 1 is a scenario in which the macro cell and the small cell use the same frequency in a structure in which the macro cell and the small cell overlap. Scenario 2 is a scenario in which the macro cell and the small cell use different frequencies in a structure in which the macro cell and the small cell overlap. Scenario 3 is a scenario in which only small cells arranged in a structure in which macro cells and small cells do not overlap are used.

Based on the above scenario, 3GPP reviewed several element technologies for improving the performance of mobile communication networks according to the introduction of high-density small cells through the study item period. 12 Presented as a representative element technology for small cell improvement. In dual connectivity, one UE is provided with a service using radio resources provided by two or more different network access points connected by non-ideal backhaul.

An object of the present invention is to provide a method for transmitting and receiving system information of a secondary cell group in an environment in which frame synchronization between a cell included in a primary base station and a cell included in a secondary base station is not guaranteed.

According to an embodiment of the present invention, there is provided a method for a terminal to receive system information of a secondary base station. The method for receiving system information includes the steps of establishing a connection with a primary base station, and a radio including system information of a cell of a secondary cell group (SCG) controlled by a secondary base station connected to the primary base station through a non-ideal backhaul and receiving a radio resource control (RRC) connection reconfiguration message from the primary base station.

In the system information reception method, the RRC connection reconfiguration message may be a message transmitted after the primary base station determines to modify a cell included in the SCG.

In the system information receiving method, the RRC connection reconfiguration message may be a message transmitted after the secondary base station determines to update the system information.

In the system information receiving method, the RRC connection reconfiguration message may include information on a time point at which the system information is applied.

The method for receiving system information may further include performing an additional procedure for a cell included in the SCG based on the system information, and transmitting an RRC connection reconfiguration complete message to the primary base station. .

The step of performing the additional procedure in the method for receiving system information may include applying the system information based on information about a time point at which the system information is applied.

According to another embodiment of the present invention, a terminal for receiving system information of a secondary base station is provided. The terminal includes at least one processor, a memory, and a wireless communication unit, wherein the at least one processor executes at least one program stored in the memory to establish a connection with a main base station, and a non-ideal bag with the main base station Receiving a radio resource control (RRC) connection reconfiguration message including system information of a cell of a secondary cell group (SCG) controlled by a single connected secondary base station from the primary base station carry out

The RRC connection reconfiguration message in the terminal may be a message transmitted after the primary base station determines a modification request for a cell included in the SCG.

The RRC connection reconfiguration message in the terminal may be a message transmitted after the secondary base station determines to update system information.

In the terminal, the RRC connection reconfiguration message may include information about a time when system information is applied.

In the terminal, at least one processor executes at least one program, performs an additional procedure for a cell included in the SCG based on system information, and sends an RRC connection reconfiguration complete message to the main base station. The step of transmitting may be further performed.

When performing the step of performing the additional procedure in the terminal, the at least one processor may perform the step of applying the system information based on the information about the time when the system information is applied.

According to another embodiment of the present invention, a terminal, a master cell group (MCG) controlled by a master base station (master eNodeB, MeNB) and a secondary base station (secondary eNodeB, SeNB) connected to the main base station through non-ideal backhaul A method of sharing a frame offset between secondary cell groups (SCG) controlled by is provided. The frame offset sharing method includes the steps of measuring a system frame number (SFN) and a subframe number (SN) of a cell included in the SCG, and a frame offset determined based on the SFN and the SN. and sharing with a base station or a secondary base station.

The method of sharing a frame offset of the terminal further includes receiving a master information block (MIB) from an auxiliary base station, and the measuring may include measuring the SFN and the SN based on the MIB. can

The sharing in the frame offset sharing method of the UE may include transmitting the SFN and the SN to the primary base station, and receiving the frame offset from the primary base station.

The sharing in the frame offset sharing method of the terminal may include calculating a frame offset based on the SFN and the SN, and transmitting the frame offset to the primary base station.

The step of measuring in the frame offset sharing method of the terminal includes receiving a radio resource control (RRC) connection reconfiguration message including a measurement indication information element for the frame offset from the main base station. can do.

In the frame offset sharing method of the terminal, the RRC connection reconfiguration message may include a radio resource management (RRM) measurement configuration message.

The frame offset sharing method of the terminal further includes the steps of receiving an RRC connection reconfiguration message for addition of a cell included in the SCG from the primary base station, and transmitting an RRC connection reconfiguration complete message to the primary base station. may include

According to another embodiment of the present invention, a primary base station (master eNodeB, MeNB) includes a primary cell group (MCG) controlled by the primary base station and a secondary eNodeB (secondary eNodeB) connected to the primary base station through non-ideal backhaul. A method of sharing a frame offset between secondary cell groups (SCG) controlled by the SeNB is provided. The method for sharing a frame offset of the primary base station includes calculating a frame offset, and transmitting the frame offset to the secondary base station through a cell addition request message (SeNB Addition Request) of the SCG.

The calculating in the method of sharing the frame offset of the primary base station may include receiving a system frame number (SFN) of the secondary base station, and calculating a frame offset based on the SFN.

Receiving in the frame offset sharing method of the primary base station, requesting an operation and management (OAM) server for the SFN of the secondary base station, and receiving the SFN of the secondary base station from the OAM server. can

The receiving in the method for sharing the frame offset of the primary base station includes requesting the SFN of the secondary base station from the secondary base station through an X2 interface between the primary base station and the secondary base station, and receiving the SFN of the secondary base station from the secondary base station. can do.

The method may further include adding a cell included in the SCG based on the frame offset in the method for sharing the frame offset of the primary base station.

The step of performing the frame offset sharing method of the primary base station includes receiving a response message (SeNB Addition Request Acknowledgment) to the addition request message from the secondary base station, and controlling radio resources to user equipment (UE). control, RRC) transmitting a connection reconfiguration message, receiving an RRC connection reconfiguration complete message from the UE, and transmitting a SeNB reconfiguration complete message to the secondary base station may include

In the method of sharing the frame offset of the primary base station, the RRC connection reconfiguration message may include information about the frame offset.

According to an embodiment of the present invention, in a mobile communication network in which a primary base station and a secondary base station are connected by non-ideal backhaul, the primary base station shares the frame offset of the secondary base station with the mobile terminal, thereby efficiently sharing system information of the secondary base station to the mobile terminal. can be sent and received with

1 is a block diagram illustrating a dual connectivity network according to an embodiment of the present invention.
2A and 2B are block diagrams illustrating protocol structures of a control plane and a user plane according to an embodiment of the present invention.
3 is a conceptual diagram illustrating a UE access scenario according to an embodiment of the present invention.
4 is a conceptual diagram illustrating an SFN/SN offset estimation method according to an embodiment of the present invention.
5 is a flowchart illustrating a frame offset sharing method using the SeNB addition procedure according to an embodiment of the present invention.
6 is a flowchart illustrating a frame offset sharing method using a measurement report procedure according to an embodiment of the present invention.
7 is a flowchart illustrating a frame offset sharing method based on a procedure between network function nodes according to an embodiment of the present invention.
8 is a flowchart illustrating a method of transmitting system information of an SCG cell according to an embodiment of the present invention.
9 is a flowchart illustrating a method of transmitting changed system information of an SCG cell according to an embodiment of the present invention.
10 is a conceptual diagram illustrating a method of transmitting changed system information in consideration of transmission delay according to an embodiment of the present invention.
11 is a block diagram illustrating a wireless communication system according to another embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, a terminal is a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS), a high reliability mobile station (HR-MS) ), a subscriber station (subscriber station, SS), a portable subscriber station (PSS), an access terminal (AT), user equipment (UE), etc., and may refer to MT, MS, It may include all or some functions of AMS, HR-MS, SS, PSS, AT, UE, and the like.

In addition, the base station (base station, BS) is an advanced base station (advanced base station, ABS), a high reliability base station (high reliability base station, HR-BS), a Node B (node B), an advanced node B (evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR)-BS, a relay serving as a base station station, RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, and a high reliability relay station (HR) serving as a base station -RS), small base station [femoto base station (femoto BS), home node B (home node B, HNB), home eNodeB (HeNB), pico base station (pico BS), metro base station (metro BS), micro base station (micro BS) ), etc.], etc., may include all or part of the functions of ABS, NodeB, eNodeB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR-RS, small base station, etc. have.

1 is a block diagram illustrating a dual connectivity network according to an embodiment of the present invention.

In FIG. 1 , a master base station (master eNodeB, MeNB) 200 is a main base station that mainly performs control and service for user equipment (UE) 100 in an overlapping cellular network environment, and a secondary eNodeB , SeNB) 300 is an auxiliary base station that provides auxiliary services. X2 is an interface used for close cooperation between the MeNB 200 and the SeNB 300, and interworking with a core network (CN) may be made through an S1-MME interface and an S1-U interface. For control plane interworking between the E-UTRAN and the CN, the MeNB 200 may perform a protocol procedure with a mobility management entity (MME) through S1-MME. The MeNB 200 may consider two types of interworking structures according to the structure of the user plane protocol for user plane interworking between the E-UTRAN and the CN. In the case of user plane protocol structure 1, the MeNB 200 may interwork with a serving gateway (S-GW) to transmit/receive data through dual connectivity. In the case of user plane protocol structure 2, the MeNB 200 and the SeNB 300 may interwork with the S-GW to transmit/receive data through dual connectivity. In this case, the mobile terminal maintains a Uu interface with the MeNB 200 and the SeNB 300 , respectively, and may transmit/receive data through the Uu interface.

2A and 2B are block diagrams illustrating protocol structures of a control plane and a user plane according to an embodiment of the present invention.

2A and 2B illustrate a control plane protocol structure and a user plane protocol structure for supporting dual connectivity based on the network structure shown in FIG. 1 .

First, a control plane protocol structure will be described with reference to FIG. 2A. In the control plane protocol structure, a radio resource control (RRC) protocol layer responsible for radio resource control is located in the MeNB 200 , and the RRC layer is not located in the SeNB 300 . That is, the RRC layer of the MeNB 200 is responsible for the radio resource control function for the cell managed by the MeNB 200 and the SeNB 300 , and can perform the RRC procedure between the SeNB 300 and the UE 100 . .

Next, with reference to FIG. 2B, a user plane protocol structure will be described. The user plane protocol structure can be divided into user plane protocol structure 1 (UP-Alt.1) and user plane protocol structure 2 (UP-Alt.2) according to whether the bearer is split and the user plane protocol arrangement of the SeNB 300. .

In user plane protocol structure 1, the bearer split function is not supported. MeNB 200, packet data convergence protocol (packet data convergence protocol, PDCP) layer, radio link control (radio link control, RLC) layer, media access control (media access control, MAC) layer, and physical (physical, PHY) ) layer is included. The SeNB 300 also includes a PDCP layer, an RLC layer, a MAC layer, and a PHY layer. That is, in the user plane protocol structure of UP-Alt.1, the SeNB 300 includes all the user plane protocol layers of the eNB presented in 3GPP LTE-A.

User plane protocol structure 2 supports the bearer split function. The MeNB 200 includes a PDCP layer, an RLC layer, a MAC layer, and a PHY layer, and the SeNB 300 includes an RLC layer, a MAC layer, and a PHY layer. That is, in the user plane protocol structure of UP-Alt.2, the SeNB 300 includes an RLC layer, a MAC layer, and a PHY layer among the user plane protocol layers of the eNB presented in 3GPP LTE-A. In this case, the user plane protocol used for dual connectivity additionally includes a function for dual connectivity support in addition to the functions of the existing 3GPP LTE-A.

3 is a conceptual diagram illustrating a UE access scenario according to an embodiment of the present invention.

In FIG. 3 , the UE 100 may support dual connectivity and carrier aggregation (CA). The MeNB 200 controls three cells operating in component carrier (CC)1, CC2, and CC3, and the SeNB 300 controls two cells operating in CC4 and CC5. In this case, the three cells operating in CC1, CC2 and CC3 are included in the master cell group (MCG) 210, and the two cells operating in CC4 and CC5 are secondary cell groups (SCG). ) 310 . In addition, the UE may receive a dual connectivity-based service through three cells controlled by the MeNB 200 (three cells operating in CC1, CC2, and CC3).

The UE 100 according to an embodiment of the present invention performs a discovery procedure for a specific cell and receives system information used in the discovered cell. The UE 100 may acquire symbol synchronization and frame synchronization of a discovered cell through a cell discovery procedure, and may acquire a physical cell identifier (PCI) used in the discovered cell. Thereafter, the UE 100 may additionally perform a cell access procedure by receiving system information including bandwidth used in the cell and uplink/downlink configuration information.

In a mobile communication system according to an embodiment of the present invention, two types of system information may be used according to a transmitted channel and a type of information, and each system information may be transmitted to a terminal through an RRC message.

First, a master information block (MIB) includes essential and limited information for system access, and may be transmitted through a broadcast channel (BCH). The MIB may include downlink cell bandwidth information, physical hybrid automatic repeat request indicator channel (PHICH) configuration information, and system frame number (SFN) information.

A system information block (SIB) includes cell-specific information required for system access, and may be transmitted through a downlink-shared channel (DL-SCH). Various SIBs from SIB1 to SIB17 may exist according to the information included.

In a mobile communication network supporting dual connectivity according to an embodiment of the present invention, the MeNB 200 and the SeNB 300 are connected through a non-ideal backhaul, and each eNB may perform a CA function. Therefore, the MeNB 200 and the SeNB 300 can provide services to the UE 100 using a plurality of CCs through the CA function as well as the dual connectivity function, and independent system information for each CC can be used. have.

Referring to FIG. 3 , in a mobile communication network supporting dual connectivity according to an embodiment of the present invention, the group of cells controlled by the MeNB 200 is the MCG 210 , and the cell group controlled by the SeNB 300 is The group is SCG 310 . In addition, in the MCG 210 , a cell used for transmission of a physical uplink control channel (PUCCH) of a cell group (CG) is a primary cell (PCell), and SCG (310) A cell used for transmission of PUCCH of CG is a special primary cell (pSCell).

In a mobile communication network in which dual connectivity is provided according to an embodiment of the present invention, an environment in which synchronization is performed between the MeNB 200 and the SeNB 300 and an environment in which synchronization is not performed may be considered. In an embodiment of the present invention, since the RRC layer of the control plane protocol is located in the MeNB 200, the system information transfer and change procedure of the MeNB 200 may be performed according to the RRC standard procedure, and the SeNB 300 is the RRC Since it does not include a layer, a method of transmitting system information for a cell controlled by the SeNB 300 will be described below. In small cell enhancement (SCE) in which the MeNB 200 and the SeNB 300 are connected through a non-ideal backhaul, the application time of the changed system information in the cell included in the SCG 310 controlled by the SeNB 300 This system performance may be affected, and a change in the system information of the pSCell may affect the uplink configuration of all cells included in the SCG 310 , thereby greatly affecting the performance of the SCG 310 .

In the case of a cell included in the MCG 210 controlled by the MeNB 200 (hereinafter referred to as an 'MCG cell'), the PCell and the SCell are connected through an ideal backhaul, and through the following RRC procedure System information of the MCG cell 210 may be transmitted.

First, the UE 100 may receive system information at the time of access to the PCell. In this case, the UE 100 may acquire system information through reception of the MIB and the SIB after the cell discovery procedure. In addition, the UE 100 may receive system information even when the SCell is added. When the SCell is added, system information of the SCell to be added may be transmitted to the UE 100 through an RRC Connection Reconfiguration message. Thereafter, the UE 100 may add the SCell by using the system information included in the received RRC connection reconfiguration message.

When the system information of the PCell included in the MCG 210 is changed, the UE 100 may receive a paging message periodically to check whether the system information is changed in the PCell of the MCG 210 . When the system information of the SCell included in the MCG 210 is changed, the MeNB 200 may transmit the changed system information to the UE 100 through the RRC connection reconfiguration procedure when the system information is changed. In this case, an information element (IE) included in the RRC connection reconfiguration message may include information about release and addition of the SCell in which system information is changed.

When system information of a cell (hereinafter referred to as an 'SCG cell') included in the SCG 310 controlled by the SeNB 300 is changed, the changed system information may be transmitted to the UE 100 according to the following method.

- Alt.1: How to use the radio access interface (Uu between MeNB/UE) between the MeNB and the UE

In this case, similar to the existing CA, the system information of the SCG cell may be delivered to the UE 100 through the MeNB 200 . The system information is transmitted through the X2 interface between the SeNB 300 and the MeNB 200, and the MeNB 200 receiving the system information from the SeNB 300 goes to the UE 100 through the RRC connection reconfiguration procedure of the SCG cell system. information can be conveyed.

- Alt.2: How to use the radio access interface (Uu between SeNB/UE) between the SeNB and the UE

In this case, the UE 100 may directly access the SeNB 300 to receive broadcast system information.

According to an embodiment of the present invention, in consideration of compatibility with existing standards and complexity issues in the UE 100 , the system information of the SCG cell is transmitted to the UE 100 through a radio access interface between the MeNB 200 and the UE 100 . ) can be transferred.

At this time, when the system information of the SCG cell is transmitted using Alt.1 in a state where the MCG cell and the SCG cell are out of synchronization, the system information used in the SCG cell and the system information used by the UE 100 are used at the time of use. synchronization is required. For example, if the time required for message transmission/reception on X2 is 60 ms, the system information of the SCG cell may be applied at least 60 ms after it is transmitted in the UE 100 . Therefore, the configuration information used for transmission in the UE 100 for a time corresponding to the X2 delay may not match the system information used in the SCG cell. Such discrepancy may affect system performance, and the X2 delay needs to be considered when transmitting system information of the SCG cell. The UE 100 according to an embodiment of the present invention may acquire or share a frame offset between an MCG cell and an SCG cell, and may efficiently receive system information using a frame offset between the MCG cell and the SCG cell. .

A mobile communication system according to an embodiment of the present invention may define a frame as a system frame and a subframe, and use the frame defined in an operation procedure of the system. Representative procedures using the system frame number and subframe number include discontinuous reception (DRX) setting, measurement gap setting, etc., and frame information specific to the UE 100 for each procedure (that is, , system frame number or subframe number, etc.) may be used.

Since the UE 100 providing dual connectivity uses an independent user plane protocol for access to the MeNB 200 or the SeNB 300, the MeNB 200 and the SeNB 300 recognize each other's frame information and If it works, you can get benefits in terms of network performance. For example, in the DRX configuration for reducing battery consumption of the UE 100, when the MeNB 200 and the SeNB 300 perform control at the same time through coordination, the CG of each eNB is independently Higher performance than the case of performing control can be expected.

As described above, since the MCG cell and the SCG cell have independent system frame numbers and subframe numbers, and are not synchronized, the MeNB 200 and the SeNB 300 providing dual connectivity have their own for cooperation with each other. It is necessary to know the offset information for the system frame number and subframe number of . In addition, for the identification or indication of the application time of the system information application of the SCG cell, or for the transmission and application of system information in consideration of the delay of the X2 interface, it is necessary to share the frame offset between the MCG cell and the SCG cell. .

In a mobile communication network in which dual connectivity is provided according to an embodiment of the present invention, the frame offset (system frame offset and sub-frame offset) is obtained based on the measurement of the UE 100 or performed between network function nodes. It can be obtained based on the procedure.

First, a method for obtaining a frame offset based on measurement of the UE 100 will be described. In the method of obtaining a frame offset based on the measurement of the UE 100 , the UE 100 with a dual connectivity function receives the MIB of the SeNB 300 , and the system frame number of the SCG cell and the MCG cell from the received MIB (system) A frame number (SFN) and a subframe number (SN) may be obtained. In this case, the MIB may be transmitted in a physical broadcast channel (PBCH) of the first subframe of all system frames. Accordingly, the UE 100 may receive the MIB of the SeNB 300 to obtain the SFN of the SCG cell, and determine the reception time of the MIB as subframe number 0 (SN0) of the SCG cell. In addition, since the UE 100 may recognize the SFN and SN of the MCG cell at the time when the MIB of the SCG cell is received, it may know both the SFN and SN of the MCG cell and the SCG cell. Therefore, in an embodiment of the present invention, the UE 100 can know the SFN of the MCG cell through the reception time of the MIB (ie, the SN0 of the SCG cell), and based on this, the UE 100 is the MCG 210 and The position of the system frame of the SCG 310 may be inferred.

Since the MCG cell and the SCG cell operate asynchronously with each other, a plurality of SNs among the SNs of the MCG cell may correspond to SN0, which is the time when the UE 100 receives the MIB of the SCG cell, and thus, to SN0 of the SCG cell. The SN of the corresponding MCG cell may be up to two.

4 is a conceptual diagram illustrating an SFN/SN offset estimation method according to an embodiment of the present invention.

Referring to FIG. 4 , the UE 100 may receive the MIB in SFN n of the SCG cell, and know the SFN and SN of the MCG cell corresponding to SN0 (ie, sf(subframe)0) of the SCG cell. In FIG. 4 , SNs of the MCG cell corresponding to SN0 of the SCG cell are sf2 and sf3. Thereafter, information about the SFN and SN of the MCG cell and the SCG cell obtained from the UE 100 may be transmitted to the MeNB 200 and used for offset derivation. In an embodiment of the present invention, the SFN offset between the MCG cell and the SCG cell may be derived through a difference between the SFN of the MCG cell and the SFN of the SCG cell. The SFN of the SCG cell may be derived through Equation 1 below.

And, the difference between the SFN of the MCG cell and the SN included in the SFN of the SCG cell can be known through the SN of the MCG cell corresponding to the time when the MIB of the SCG cell is received (ie, sf0 of the SCG cell).

Next, a method of measuring a frame offset based on a procedure between network functional nodes will be described. A method of measuring a frame offset based on a procedure between network function nodes may be divided into a method by an operation and management (OAM) server and a method through an X2 interface between eNBs.

In the method of obtaining the frame offset through the OAM server, the OAM server requests and receives the SFN/SN from another node requested at a specific time (time t) according to the SFN request received from the specific node, and receives the received SFN/SN. forwarded to the MeNB 200 . To this end, the OAM server may use a global positioning system (GPS), IEEE1588, or a network time protocol (NTP). At this time, the MeNB 200 requests SFN/SN information corresponding to a specific time point (absolute time base) from the OAM server to obtain the SFN/SN of the SeNB 300 providing dual connectivity, and the MeNB 200 The OAM server receiving the request from the SeNB 300 may perform a Query procedure on the SeNB 300 and then transfer the received SFN/SN of the SeNB 300 to the MeNB 200 . Thereafter, the MeNB 200 may obtain the frame offset of the SeNB 300 .

In the method of obtaining the frame offset through the inter-eNB X2 interface, the MeNB 200 requests the SFN/SN from the SeNB 300 at a specific time (time t), and based on this, the frame offset of the SFN/SN may be obtained. have. In this case, the MeNB 200 may use GPS, IEEE1588, NTP, or the like. In order to obtain the SFN/SN of the SeNB 300 that provides dual connectivity, the MeNB 200 requests SFN/SN information corresponding to a specific time point (absolute time-based) from the SeNB 300, and receives the request. When the SeNB 300 performs the measurement procedure and transmits the SFN/SN information obtained as a measurement result to the MeNB 200, the MeNB 200 calculates the frame offset of the SeNB 300 based on the SFN/SN information. can

Hereinafter, a signaling method for sharing a frame offset between an MCG cell and an SCG cell will be described with reference to FIGS. 5 to 7 . The signaling method for sharing the frame offset between the MCG cell and the SCG cell may be performed based on measurement of the UE 100 or may be performed based on a procedure between network function nodes.

First, a signaling method for acquiring and sharing a frame offset based on the measurement of the UE 100 may be divided into a method using a SeNB addition procedure or a SeNB modification procedure, and a method using a measurement report procedure. Since the method of obtaining the frame offset based on the measurement of the UE 100 is to obtain the frame offset between the MCG cell and the SCG cell to which dual connectivity is to be established, it is not performed every time and selectively when necessary according to the instructions of the MeNB 200 can be performed.

5 is a flowchart illustrating a frame offset sharing method using the SeNB addition procedure according to an embodiment of the present invention.

The MeNB 200 considers the radio resource management (RRM) measurement result of the UE 100 and the load of the SCG cell, through the measurement of the UE 100 when adding the SCG cell, the MCG cell and the SCG A frame offset between cells may be obtained and shared with the UE 100 .

First, the MeNB 200 requests the SeNB 300 to add a cell to the SCG (S501). At this time, the MeNB 200 transmits an SCG cell addition request message (SeNB Addition Request) for dual connectivity in consideration of the RRM measurement result of the UE 100 and the load state of the SCG cell.

Thereafter, the SeNB 300 transmits a modification request for addition of a cell to the SCG to the MeNB 200 (S502). That is, the SeNB 300 performs an admission procedure for the SCG cell addition request, and then transmits a response message (SeNB Addition Request Acknowledgment) to the SCG addition request for SCG cell addition to the MeNB 200 . have.

Thereafter, the MeNB 200 instructs the UE 100 to measure a frame offset for a cell that is a target of SCG Addition (S503). The MeNB 200 may instruct the UE 100 to measure the frame offset through the RRC connection reconfiguration message. In this case, the RRC Connection Reconfiguration message may include a measurement indication information element for the frame offset of the SCG cell.

The UE 100 may measure the SCG addition target cell, receive MIB information of the SCG addition target cell, and measure SFN/SN information based thereon ( S504 ). In this case, the UE 100 may measure the SFN/SN information from the MIB information using the method described with reference to FIG. 4 and Equation 1 .

The UE 100 calculates the frame offset of the MCG cell and the SCG cell by using the measured SFN/SN information of the MCG cell and the SCG cell (S505). Then, the UE 100 may report the calculated frame offset to the MeNB 200 through an RRC Connection Reconfiguration Complete message (S506). In this case, the RRC connection reconfiguration complete message may include an information element about the SCG cell frame offset.

At this time, or in another embodiment of the present invention, the UE 100 reports the measured SFN/SN information of the MCG cell and the SCG cell to the MeNB 200, and the MeNB 200 reports the SFN of the MCG cell and the SCG cell. The frame offset of the MCG cell and the SCG cell may be calculated using the /SN information.

Finally, the MeNB 200 transmits the frame offset information to the SeNB 300 through the SeNB reconfiguration response message (SeNB Reconfiguration Complete) (S507). In this case, the SeNB Reconfiguration Complete message may include a frame offset information element.

6 is a flowchart illustrating a frame offset sharing method using a measurement report procedure according to an embodiment of the present invention.

The MeNB 200 may obtain a frame offset between the MCG cell and the SCG cell through the RRM measurement report of the UE 100 and share it with the UE 100 . Referring to FIG. 6 , the MeNB 200 acquires the SFN of the SCG cell using a measurement report through a measurement configuration instructing the UE 100 supporting the dual connectivity function to acquire the SFN of the cell. and may share the obtained SFN information with the UE 100 .

First, the MeNB 200 transmits an RRM measurement configuration message for SFN/SN measurement of the SCG cell to the UE 100 (S601). In this case, the RRM measurement setup message may be included in the RRC connection reconfiguration message, and the RRC connection reconfiguration message may include a measurement indication information element for the frame offset of the SCG cell. Then, the MeNB 200, in order to additionally receive an advanced cell global identifier (ECGI) for the previously measured PCI, the RRM measurement setting for the acquisition of the cell identifier (ECGI) that is the PCI of the cell You can direct it through a message.

Thereafter, the UE 100 transmits a response to the measurement setup message to the MeNB 200 through the RRC connection reconfiguration complete message ( S602 ). Then, the UE 100 performs measurement on the target cell to be added to the SCG cell, receives MIB information of the SCG cell, and measures SFN/SN information through the received MIB (S603). Then, the UE 100 calculates a frame offset between the MCG cell and the SCG cell using the measured SFN/SN information (S604). Thereafter, the UE 100 transmits a measurement report including information on the calculated frame offset to the MeNB 200 ( S605 ). In this case, the measurement report message may include an information element about the frame offset of the SCG cell.

If the MeNB 200 is responsible for calculating the frame offset, the UE 100 reports the measured SFN/SN information to the MeNB 200, and the MeNB 200 uses the reported SFN/SN information to frame the frame. You can calculate the offset.

When the UE 100 is instructed to obtain a cell identifier (ECGI) for PCI, the UE 100 may receive the system information to obtain the ECGI, and then report the obtained ECGI to the MeNB 200 .

Thereafter, the calculated frame offset information may be transmitted from the MeNB 200 to the SeNB 300 through a SeNB Addition Request message (S606). In this case, the SeNB addition request message may include a frame offset information element. Thereafter, based on the shared frame offset, an SCG cell addition procedure is started, in which the SeNB 300 transmits an SCG Addition Request Acknowledgment to the MeNB 200, MeNB 200 sending an RRC connection reconfiguration message to the UE 100, the UE 100 applying the cell-related system information of the SCG, and then transmitting an RRC connection reconfiguration complete message to the MeNB 200, and the MeNB 200 may include transmitting a SeNB Reconfiguration Complete message to the SeNB 300 (S607).

Next, a method in which the frame offset is obtained and shared based on the procedure between the network function nodes is described.

7 is a flowchart illustrating a frame offset sharing method based on a procedure between network function nodes according to an embodiment of the present invention.

To obtain the frame offset shown in FIG. 7 , an OAM server may be used or an X2 interface between the MeNB 200 and the SeNB 300 may be used.

First, a method for obtaining a frame offset between an MCG cell and an SCG cell at a specific time using the OAM server will be described (S701). The MeNB 200 requests the SFN of a specific SeNB 300 corresponding to a specific time point to the OAM server. Upon receiving the request of the MeNB 200 , the OAM server requests the specific SeNB 300 for an SFN value for a specific time point (absolute time). In this case, the specific SeNB 300 may measure the SFN value for a specific time point using GPS, IEEE1588, or NTP. Thereafter, the OAM server may transfer the received SFN to the MeNB 200 , and the MeNB 200 may calculate a frame offset of the SFN based on the SFN received from the OAM server.

Next, a method for obtaining a frame offset between the MCG cell and the SCG cell at a specific time using the X2 interface will be described (S701'). First, the MeNB 200 requests the SeNB 300 for an SFN at a specific time. Upon receiving the request, the SeNB 300 measures the SFN for a specific time point (absolute time) using GPS, IEEE 1588, or NTP, and transmits the measured SFN to the MeNB 200 . The MeNB 200 may calculate a frame offset of the SFN based on the received SFN.

Thereafter, the MeNB 200 transmits the calculated frame offset to the SeNB 300 through an SCG Addition Request message (S702). In this case, the SCG addition message may include a frame offset information element. Thereafter, an addition procedure of the SCG cell may be started based on the shared frame offset, in which the SeNB 300 transmits a SeNB Addition Request Acknowledgment to the MeNB 200, the MeNB 200 ) transmitting an RRC connection reconfiguration message to the UE 100, the UE 100 applying the system information about the cell of the SCG, and then transmitting an RRC connection reconfiguration complete message to the MeNB 200, and the MeNB 200 ) may include transmitting a SeNB Reconfiguration Complete message to the SeNB 300 (S703). In this case, information about the frame offset may be shared with the UE 100 through the RRC connection reconfiguration message.

Hereinafter, a method of transmitting system information of an SCG cell will be described, and the method will be divided into a method of transmitting system information when accessing a specific SCG cell and a method of changing system information upon additional access to a specific SCG cell.

8 is a flowchart illustrating a method of transmitting system information of an SCG cell according to an embodiment of the present invention.

According to an embodiment of the present invention, when an Scell is added to a specific SeNB 300 for dual connectivity, a procedure for changing the SCG cell may be performed. In this case, the cell connected to the SeNB 300 is a pSCell or an SCell, and the UE 100 performs an RRC signaling procedure in the form of a UE-specific dedicated (UE-specific) in order to receive the system information of the cell. can be done That is, the system information of the pSCell or sSCell to be added may be transmitted to the UE 100 via the SeNB 300 and the MeNB 200 .

First, the MeNB 200 transmits a SeNB Modification Request message for SCG cell change to the SeNB 300 (S801). Upon receiving the SeNB change request message from the MeNB 200 , the SeNB 300 transmits the system information as an information element in the form of a container to the MeNB 200 through a SeNB Modification Request Acknowledgment message. (S802). That is, in the system information delivery method according to an embodiment of the present invention shown in FIG. 8 , the system information delivery of the SCG cell may be triggered by the MeNB 200 .

Then, the MeNB 200 inserts an information element for addition of the SCG cell (system information of the SCG cell is included) in the RRC connection reconfiguration message and delivers it to the UE 100 (S803). The UE 100 may perform the SCG cell addition procedure based on the system information of the SCG cell included in the RRC connection reconfiguration message (S804). Thereafter, when the SCG cell is added, the UE 100 transmits an RRC connection reconfiguration complete message to the MeNB 200 ( S805 ), and the MeNB 200 receiving the RRC connection reconfiguration complete message completes the SeNB reconfiguration to the SeNB 300 . A message (SeNB Reconfiguration Complete) is transmitted (S806). The procedure shown in FIG. 5 may be used for a method of transmitting system information upon access to an SCG cell according to another embodiment of the present invention.

9 is a flowchart illustrating a method of transmitting system information of an SCG cell according to another embodiment of the present invention, and FIG. 10 is a conceptual diagram illustrating a method of transmitting changed system information in consideration of transmission delay according to an embodiment of the present invention. am.

The method of delivering the system information of the SCG cell according to another embodiment of the present invention may be applied when the system information used in the SCG cell is changed when the UE 100 is connected to the SCG cell.

If the changed system information is transmitted without considering the use time of the system information between the SCG cell and the UE 100, system performance may be deteriorated, so it is necessary to synchronize the use time of the system information between the SCG cell and the UE 100. .

Accordingly, the SeNB 300 transmits the changed system information to the MeNB 200 in consideration of the time when the system information of the SCG cell is changed and the transmission delay on X2. Referring to FIG. 10 , when the transmission delay (including the backhaul delay and the wireless transmission delay between MeNB/UE) is ΔT _L , the SeNB 300 performs the system information 1000 change at any time before _{ΔT L.} , by sending a system information update message to the MeNB 200 , it is possible to start the SeNB change procedure for system information change.

The changed system information may also be delivered through a dedicated RRC signaling procedure specific to the UE 100 , and the changed system information is delivered to the UE 100 via the SeNB 300 and the MeNB 200 .

First, the SeNB 300 determines to update the system information (S901), and sends the changed system information and SFN/SN information regarding the time when the changed system information is applied, to the MeNB (SeNB Modification Request) through the SeNB Modification Request message. 200) (S902). That is, in the system information delivery method according to another embodiment of the present invention shown in FIG. 9 , the system information delivery of the SCG cell may be triggered by the SeNB 300 .

In addition, the MeNB 200 transmits the changed system information and information about the time when the changed system information is applied to the UE 100 through the RRC connection reconfiguration message (S903). In this case, the RRC connection reconfiguration message transmitted by the MeNB 200 may include an information element for release and addition of the SCell in which the system information is changed. In addition, information about the time when the changed system information is applied may be information about SFN/SN.

Upon receiving the RRC connection reconfiguration message, the UE 100 recognizes the application time to which the changed system information is applied through the received SFN / SN information element, and is included in the release information element and the additional information element of the SCell in consideration of the application time. A system information update operation may be performed using the information (S904). After completing the system information update, the UE 100 transmits an RRC Connection Reconfiguration Complete message to the MeNB 200 (S905), and the MeNB 200 that has received the RRC Connection Reconfiguration Complete message sends the SeNB A SeNB modification response (SeNB Modification confirm) message is transmitted to 300 (S906).

11 is a block diagram illustrating a wireless communication system according to another embodiment of the present invention.

Referring to FIG. 11 , a wireless communication system according to an embodiment of the present invention includes a base station 1110 such as MeNB 200 or SeNB 300 and a terminal 1120 such as UE 100 .

The base station 1110 includes a processor 1111 , a memory 1112 , and a radio frequency unit (RF unit) 1113 . The memory 1112 may be connected to the processor 1111 to store various information for driving the processor 1111 . The wireless communication unit 1113 may be connected to the processor 1111 to transmit and receive wireless signals. The processor 1111 may implement a function, process, or method proposed in an embodiment of the present invention. In this case, in the wireless communication system according to an embodiment of the present invention, the air interface protocol layer may be implemented by the processor 1111 . The operation of the base station 1110 according to an embodiment of the present invention may be implemented by the processor 1111 .

The terminal 1120 includes a processor 1121 , a memory 1122 , and a wireless communication unit 1123 . The memory 1122 may be connected to the processor 1121 to store various information for driving the process 1121 . The wireless communication unit 1123 may be connected to the processor 1121 to transmit and receive wireless signals. The processor 1121 may implement a function, step, or method proposed in an embodiment of the present invention. In this case, in the wireless communication system according to an embodiment of the present invention, the air interface protocol layer may be implemented by the processor 1121 . The operation of the terminal 1120 according to an embodiment of the present invention may be implemented by the processor 1121 .

In an embodiment of the present invention, the memory may be located inside or outside the processor, and the memory may be connected to the processor through various known means. The memory is a volatile or non-volatile storage medium of various types. For example, the memory may include a read-only memory (ROM) or a random access memory (RAM).

As described above, according to an embodiment of the present invention, in a mobile communication network in which a primary base station and a secondary base station are connected by non-ideal backhaul, the primary base station shares the frame offset of the secondary base station with the mobile terminal, thereby efficiently sharing system information of the secondary base station with the mobile terminal. can be passed on to

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improved forms of the present invention are also provided by those skilled in the art using the basic concept of the present invention as defined in the following claims. is within the scope of the right.

Claims (26)

A method in which a terminal shares a frame offset between a master base station (master eNodeB, MeNB) and a secondary base station (secondary eNodeB, SeNB),
Receiving a measurement configuration for the secondary base station through radio resource control (RRC) signaling from the master base station,
Receiving a master information block (MIB) from a primary secondary cell (pSCell) of the secondary base station,
Measuring a system frame number (SFN) of the secondary base station through the MIB, and
Transmitting, to the master base station, a measurement report including frame offset information determined based on the SFN of the secondary base station, corresponding to the measurement configuration received from the master base station
including,
The master base station and the secondary base station provide a dual connectivity (dual connectivity) to the terminal, a frame offset sharing method. In claim 1,
The measurement report further comprises subframe boundary offset information determined based on the subframe timing of the secondary base station with respect to the master base station. In claim 2,
The subframe boundary offset information is determined by a difference between a time when the terminal receives a start subframe from the master base station and a time when the terminal receives a start subframe from the auxiliary base station. In claim 1,
The frame offset information is used for discontinuous reception (DRX) configuration. In claim 1,
The frame offset information is used for measurement gap configuration, the frame offset sharing method. In claim 1,
Receiving an RRC connection reconfiguration message for adding a cell of the secondary base station from the master base station, and
Transmitting an RRC Connection Reconfiguration Complete message to the master base station
A frame offset sharing method further comprising a. In claim 1,
The measurement report further includes radio frame boundary offset information determined based on the subframe timing of the secondary base station with respect to the master base station. In claim 7,
The radio frame boundary offset information is determined by a difference between a time when the terminal receives a start radio frame from the master base station and a time when the terminal receives a start radio frame from the auxiliary base station. A method for a master base station (master eNodeB, MeNB) to share a frame offset between the master base station and a secondary base station (secondary eNodeB, SeNB),
Transmitting the measurement configuration for the secondary base station through radio resource control (RRC) signaling to the terminal, and
Receiving a measurement report including frame offset information determined based on a system frame number (SFN) measured by the terminal in accordance with the measurement configuration
including,
The system frame number is measured by the terminal through a master information block (MIB) received from a primary secondary cell (pSCell), and the master base station and the secondary base station are dually connected to the terminal A method of sharing frame offsets that provides (dual connectivity). In claim 9,
The measurement report further includes subframe boundary offset information determined by the terminal based on the subframe timings of the secondary base station and the master base station. In claim 10,
The subframe boundary offset information is determined by a difference between a time when the terminal receives a start subframe from the master base station and a time when the terminal receives a start subframe from the auxiliary base station. In claim 9,
The frame offset information is used for discontinuous reception (DRX) configuration. In claim 9,
The frame offset information is used for measurement gap configuration, the frame offset sharing method. In claim 9,
The measurement report further includes radio frame boundary offset information determined based on the subframe timing of the secondary base station with respect to the master base station. 15. In claim 14,
The radio frame boundary offset information is determined by a difference between a time when the terminal receives a start radio frame from the master base station and a time when the terminal receives a start radio frame from the auxiliary base station. delete delete delete delete delete delete delete delete delete delete delete

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