KR20140080193A - Method and apparatus of controling bearer extension in heterogeneous network wireless communication system - Google Patents

Abstract

The present invention relates to a method for controlling a bearer extension in a heterogeneous network wireless communication system and an apparatus thereof. Disclosed in the present invention is a method for releasing a bearer extension by means of a terminal, the method including the following steps: receiving, from a macro base station, an uplink transmission initiation information, which indicates the initiation of uplink transmission by using an EPS bearer of a macro cell between the macro base station and the terminal, while performing transmission and reception between a small base station and the terminal by using an extended EPS bearer; and resuming the transmission and the reception by using the EPS bearer of the macro cell based on the indication by the uplink transmission initiation information. By using the EPS bearer of an existing macro cell and without generating a new EPS bearer for the macro base station, quick and uninterrupted service can be provided.

Description

TECHNICAL FIELD [0001] The present invention relates to a bearer extension control method, and more particularly, to a bearer extension control method and apparatus for a bearer extension control method in a heterogeneous network wireless communication system.

[0001] The present invention relates to wireless communication, and more particularly, to a method and apparatus for wireless communication in which data on a user plane is provided using an extended EPS bearer and data on a control plane is provided using an EPS bearer of a macrocell, To an apparatus and method for providing data of a user plane using an EPS bearer of a macro cell again when moving to the area of only the original macrocell.

A multiple component carrier system refers to a wireless communication system capable of supporting carrier aggregation. Carrier aggregation is a technique for efficiently using a fragmented small band, in which one base station bundles a plurality of physically continuous or non-continuous bands in the frequency domain to use a logically large band So as to achieve the same effect as the above. Multi-element carrier systems support multiple component carriers (CCs) that are distinct in the frequency domain. The element carrier includes an uplink element carrier used in the uplink and a downlink element carrier used in the downlink. A DL serving as a serving cell may be formed by combining a downlink component carrier and an uplink component carrier. Or one serving cell may be composed of only the downlink component carrier.

In certain areas, such as a hotspot inside a cell, there is a particularly high demand for communication, and in certain areas, such as the cell edge or coverage hole, the reception sensitivity of the radio wave may be reduced. 2. Description of the Related Art As wireless communication technology has developed, small cells in a macro cell, for example, a pico cell, have been used for the purpose of enabling communication in an area such as a hot spot, a cell boundary, A pico cell, a femtocell, a micro cell, a remote radio head (RRH), a relay, and a repeater are installed together. Such a network is called a heterogeneous network (HetNet). In a heterogeneous network environment, a macro cell is a large cell with a large coverage and a small cell such as a femtocell and a picocell is a small cell. In a heterogeneous network environment, coverage overlap occurs between a plurality of macro cells and small cells.

A terminal connected to a network can perform communication with an arbitrary cell according to a channel environment or a moving state, and can perform a cell change. In case of cell change, a handover can be performed to solve a problem of call drop occurring when moving to an adjacent cell. Handover refers to a process of moving from a current communication service area (hereinafter, referred to as a source cell) to a neighboring communication service area (hereinafter, referred to as a target cell) traffic channel to maintain a constant call state. That is, a terminal communicating with a specific base station is linked to another adjacent base station (hereinafter referred to as a target base station) when the signal strength at the specific base station (hereinafter referred to as a source base station) becomes weak . For example, a terminal may disconnect from a macro cell and connect to another macro cell or picocell due to deterioration of a channel state in a state of being connected to a macro cell. Or, as the terminal moves while connected to the macro cell, it can disconnect from the macro cell and connect to another macro cell or picocell.

A terminal may perform wireless communication through any one of base stations constituting at least one serving cell. In a heterogeneous network environment, a mobile station having a connection with a base station constituting a macro cell has good signal quality of other base stations constituting a small cell, and even when a radio resource utilization rate is low, . Also, even if a terminal is connected to a base station constituting a small cell through a handover procedure or the like, the coverage of the small cell is relatively small, so that handover frequently occurs according to the movement of the terminal. This is true even if the terminal supports multi-element carriers. Accordingly, there is a need for a technique for efficiently distributing data in a small cell without handover procedures in a heterogeneous network environment, in which an excessive load or load requiring a specific QoS is required.

In particular, when the data of the user plane is provided using the extended EPS bearer and the data of the control plane is provided using the EPS bearer of the macro cell, when the terminal moves out of the small cell area and moves back to the original macro cell area , And an apparatus and a method for providing user plane data using an EPS bearer of a macrocell again.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for switching from a bearer extension mode to a normal mode in a wireless communication system.

Another object of the present invention is to provide a cell planning method for efficiently transmitting data to a mobile station without causing an unnecessary load on the cell in a heterogeneous network environment.

Another aspect of the present invention is to efficiently transmit data to an extended radio bearer (RB) to a mobile station.

Another aspect of the present invention is to provide a method and apparatus for providing data on a control plane by using an EPS bearer and providing data on a control plane using an EPS bearer of a macro cell, And an apparatus and a method for providing data of a user plane by using an EPS bearer of a macro cell again when moving.

Another technical object of the present invention is to prevent frequent handover of a terminal and seamlessly provide data.

According to an aspect of the present invention, there is provided a method for releasing a bearer extension by a terminal in a heterogeneous network system including a macro base station (Macro eNB) and a small base station (Small eNB). The method includes initiating an uplink transmission using an EPS bearer of a macro cell between the macro base station and the terminal during transmission and reception using an extended EPS (Evolved Packet System) bearer between the small base station and the terminal Receiving from the macro base station the uplink transmission start information (BasicULTxStartInfo) instructing the MAC base station to resume transmission and reception using the EPS bearer of the macro cell based on the indication of the uplink transmission start information do.

According to another aspect of the present invention, there is provided a terminal for releasing a bearer extension in a heterogeneous network system including a macro base station and a small base station. The UE transmits an uplink transmission request for starting uplink transmission using the EPS bearer of the macrocell between the macro base station and the terminal while performing transmission and reception using the extended EPS bearer between the small base station and the terminal And a terminal processor for resuming transmission and reception using the EPS bearer of the macro cell based on the instruction of the uplink transmission start information.

When the UE using the extended EPS bearer moves beyond the coverage of the small cell and moves to the coverage of the previous macro cell, the EPS bearer of the original macro cell is used instead of generating the new EPS bearer for the macro base station, It is possible to provide a service which is not available.

1 shows a wireless communication system to which the present invention is applied.
2 is a block diagram illustrating a radio protocol architecture for a user plane.
3 is a block diagram illustrating a wireless protocol structure for a control plane.
FIG. 4 shows a structure of a bearer service in a wireless communication system to which the present invention is applied.
FIG. 5 is a diagram schematically illustrating the concept of a heterogeneous network composed of a macro base station, a femto base station, and a pico base station according to the present invention.
6 is a conceptual diagram illustrating a connection configuration between a macro base station and a small base station according to the present invention.
7 is a conceptual diagram illustrating a connection configuration between a macro base station and a small base station according to another example of the present invention.
8 is a flowchart illustrating signaling between a terminal, a macro base station, and a small base station according to an exemplary embodiment of the present invention.
9 is a flowchart illustrating an operation of a terminal according to an exemplary embodiment of the present invention.
10 is an operation flowchart of a macro base station according to an example of the present invention.
11 is a flowchart of an operation of a small base station according to an example of the present invention.
12 is a block diagram illustrating a terminal, a macro base station, and a small base station according to the present invention.

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

In addition, the present invention will be described with respect to a wireless communication network. The work performed in the wireless communication network may be performed in a process of controlling a network and transmitting data by a system (e.g., a base station) Work can be done at a terminal connected to the network.

1 shows a wireless communication system to which the present invention is applied. This may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may be called LTE (Long Term Evolution) or LTE-A (advanced) system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

On the other hand, there is no limitation on a multiple access technique applied to a wireless communication system. (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA , OFDM-CDMA, and the like.

Here, TDD (Time Division Duplex) scheme in which uplink and downlink transmission are transmitted using different time periods or FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies may be used .

Referring to FIG. 1, an E-UTRAN includes a base station (BS) 20 that provides a control plane and a user plane to a user equipment (UE) 10. The terminal 10 may be fixed or mobile and may be referred to by other terms such as a mobile station (MS), an advanced MS (MS), a user terminal (UT), a subscriber station (SS) .

The base station 20 generally refers to a station that communicates with the terminal 10 and includes an evolved NodeB (eNodeB), a Base Transceiver System (BTS), an access point, a femto-eNB, A pico-eNB, a home eNB, a relay, and so forth. The base station 20 may provide at least one cell to the terminal. The cell may mean a geographical area where the base station 20 provides communication services, or may refer to a specific frequency band. A cell may denote a downlink frequency resource and an uplink frequency resource. Or a cell may mean a combination of a downlink frequency resource and an optional uplink frequency resource.

The base stations 20 may be interconnected via an X2 interface. The base station 20 is connected to an S-GW (Serving Gateway) through an MME (Mobility Management Entity) and an S1-U through an EPC (Evolved Packet Core) 30, more specifically, an S1-MME through an S1 interface. The S1 interface exchanges OAM (Operation and Management) information to support the movement of the terminal 10 by exchanging signals with the MME.

The EPC 30 includes an MME, an S-GW, and a Packet Data Network-Gateway (P-GW). The MME has information on the connection information of the terminal 10 and the capability of the terminal 10. This information is mainly used for managing the mobility of the terminal 10. [ The S-GW is a gateway having an E-UTRAN as an end point, and the P-GW is a gateway having a PDN (Packet Data Network) as an end point.

The E-UTRAN and the EPC 30 may be combined to form an EPS (Evolved Packet System). The traffic flow from the wireless link to the base station 20 to the PDN, (Internet Protocol).

The wireless interface between the terminal and the base station is called a Uu interface. The layers of the radio interface protocol between the UE and the network are classified into L1 (first layer), L1 (second layer), and the like based on the lower three layers of the Open System Interconnection (OSI) A physical layer belonging to a first layer provides an information transfer service using a physical channel, and a physical layer (physical layer) An RRC (Radio Resource Control) layer located at Layer 3 controls the radio resources between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the BS.

2 is a block diagram illustrating a radio protocol architecture for a user plane. 3 is a block diagram illustrating a wireless protocol structure for a control plane. The user plane is a protocol stack for transmitting user data, and the control plane is a protocol stack for transmitting control signals.

2 and 3, a physical layer (PHY) provides an information transfer service to an upper layer using a physical channel. The physical layer is connected to a medium access control (MAC) layer, which is an upper layer, through a transport channel. Data is transferred between the MAC layer and the physical layer through the transport channel. The transport channel is classified according to how the data is transmitted through the air interface. Data is transferred between the different physical layers, that is, between the transmitter and the physical layer of the receiver through a physical channel. The physical channel can be modulated by an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and uses time and frequency as radio resources. There are several physical control channels. The physical downlink control channel (PDCCH) informs the UE of resource allocation of a paging channel (PCH), a downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to the DL-SCH. The PDCCH may carry an uplink scheduling grant informing the UE of the resource allocation of the uplink transmission. A physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs and is transmitted every subframe. PHICH (Physical Hybrid ARQ Indicator Channel) carries HARQ ACK / NAK signal in response to uplink transmission. A physical uplink control channel (PUCCH) carries uplink control information such as HARQ ACK / NAK, scheduling request and CQI for downlink transmission. A physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH).

The function of the MAC layer includes a mapping between a logical channel and a transport channel and a multiplexing / demultiplexing into a transport block provided as a physical channel on a transport channel of a MAC SDU (service data unit) belonging to a logical channel. The MAC layer provides a service to a Radio Link Control (RLC) layer through a logical channel. The logical channel can be divided into a control channel for transferring control area information and a traffic channel for transferring user area information.

The function of the RLC layer includes concatenation, segmentation and reassembly of the RLC SDUs. In order to guarantee various QoS (Quality of Service) required by a radio bearer (RB), the RLC layer includes Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode , And AM). AM RLC provides error correction via automatic repeat request (ARQ).

The functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include transmission of user data, header compression and ciphering. The function of the Packet Data Convergence Protocol (PDCP) layer in the user plane includes transmission of control plane data and encryption / integrity protection.

The RRC layer is responsible for the control of logical channels, transport channels and physical channels in connection with the configuration, re-configuration and release of RBs. RB means a logical path provided by a first layer (PHY layer) and a second layer (MAC layer, RLC layer, PDCP layer) for data transmission between a UE and a network. The configuration of the RB means a process of defining characteristics of a radio protocol layer and a channel to provide a specific service, and setting each specific parameter and an operation method. The RB may be further classified into an SRB (Signaling RB) and a DRB (Data RB). The SRB is used as a path for transmitting the RRC message and the NAS message in the control plane, and the DRB is used as a path for transmitting the user data in the user plane.

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

When there is an RRC connection between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in an RRC connected state. Otherwise, the UE is in an RRC idle state do.

The downlink transmission channel for transmitting data from the network to the terminal includes a BCH (Broadcast Channel) for transmitting system information and a downlink SCH (Shared Channel) for transmitting user traffic or control messages. In case of a traffic or control message of a downlink multicast or broadcast service, it may be transmitted through a downlink SCH, or may be transmitted via a separate downlink MCH (Multicast Channel). Meanwhile, the uplink transmission channel for transmitting data from the UE to the network includes a random access channel (RACH) for transmitting an initial control message and an uplink SCH (Shared Channel) for transmitting user traffic or control messages.

A logical channel mapped to a transport channel is a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), a multicast traffic Channel).

A physical channel is composed of a plurality of subcarriers in a frequency domain and a plurality of symbols in a time domain. One sub-frame is composed of a plurality of OFDM symbols in the time domain. One subframe is composed of a plurality of resource blocks, and one resource block is composed of a plurality of symbols and a plurality of subcarriers. Also, each subframe may use specific subcarriers of the specific symbols (e.g., the first symbol) of the corresponding subframe for PDCCH (Physical Downlink Control Channel). The transmission time interval (TTI), which is the unit time at which data is transmitted, is 1 ms corresponding to one subframe.

In order for a terminal to transmit user data (e.g., IP packets) to an external Internet network or to receive user data from an external Internet network, it is necessary for the terminal to exist between the mobile communication network entities existing between the terminal and the external Internet network. The resource must be assigned to multiple paths. A path in which resources are allocated between mobile communication network entities and data transmission / reception is possible is called a bearer.

FIG. 4 shows a structure of a bearer service in a wireless communication system to which the present invention is applied.

Referring to FIG. 4, an end-to-end service is provided between a terminal and an Internet network. Here, the term end-to-end service means a service (EPS Bearer) between a terminal and a P-GW and a service requiring an external bearer to the P-GW and the outside for an Internet network and a data service. Here, the external path is a bearer between the P-GW and the Internet network.

In order for the UE to transmit data to the external Internet network, the UE transmits data to the eNB through the RB on the radio. The base station then transmits the data to the S-GW through the S1 bearer. The S-GW delivers the data to the P-GW through the S5 / S8 bearer and finally to the destination in the P-GW and the external internet network through the external bearer.

Likewise, in order for data to be transmitted from the external Internet network to the mobile station, the mobile station can transmit data to the mobile station via the bearers in the reverse direction.

As described above, in the wireless communication system, each bearer is defined for each interface to ensure independence between interfaces. The bearer on each interface is described in more detail as follows.

The bearer provided by the wireless communication system is collectively referred to as an evolved packet system (EPS) bearer. The EPS bearer is a delivery path established between the UE and the P-GW to transmit IP traffic with a specific QoS. The P-GW may receive an IP flow from the Internet or may transmit an IP flow over the Internet. Each EPS bearer is set with QoS decision parameters indicating the characteristics of the propagation path. An EPS bearer may be configured for one or more UEs, and one EPS bearer uniquely represents a concatenated value of one E-RAB and one S5 / S8 bearer.

The S5 / S8 bearer is the bearer of the S5 / S8 interface. Both S5 and S8 are bearers present at the interface between the S-GW and the P-GW. S5 interface exists when the S-GW and P-GW belong to the same service provider. The S8 interface belongs to the Visited PLMN roaming S-GW and the P- RTI ID = 0.0 > PLMN). ≪ / RTI >

The E-RAB uniquely represents the concatenation of the S1 bearer and its corresponding RB. When there is one E-RAB, a one-to-one mapping is established between the corresponding E-RAB and one EPS bearer. That is, one EPS bearer corresponds to one RB, S1 bearer, and S5 / S8 bearer, respectively. The S1 bearer is the bearer at the interface between the base station and the S-GW.

RB means two kinds of data RB (Data Radio Bearer: DRB) and signaling RB (Signaling Radio Bearer: SRB). In the present invention, RB is expressed as RB to be. Therefore, the RB that is expressed separately is distinguished from the signaling radio bearer (SRB). RB is a path through which user plane data is transmitted, and SRB is a path through which control plane data such as an RRC layer and a NAS control message are transmitted. There is a one-to-one mapping between RB, E-RAB and EPS bearer.

EPS bearer types have a default bearer and a dedicated bearer. When a terminal accesses a wireless communication network, an IP address is allocated, a PDN connection is created, and a default EPS bearer is simultaneously created. That is, the default bearer is created the first time a new PDN connection is created. If a user uses a service (eg, the Internet) via a default bearer and uses a service (eg, VoD, etc.) that is not properly provided with QoS as the default bearer, A dedicated bearer is created. In this case, the dedicated bearer can be set to a different QoS from the bearer that has already been set. The QoS decision parameters applied to the dedicated bearer are provided by the Policy and Charging Rule Function (PCRF). When generating the dedicated bearer, the PCRF can receive the subscription information of the user from the Subscriber Profile Repository (SPR) and determine QoS determination parameters. Up to 15 dedicated bearers can be created, for example, up to 15, and in the LTE system, four out of the 15 are not used. Therefore, up to 11 dedicated bearers can be created.

The EPS bearer includes QoS Class Identifier (QCI) and Allocation and Retention Priority (ARP) as basic QoS decision parameters. EPS bearer is divided into GBR (Guaranteed Bit Rate) bearer and non-GBR bearer according to QCI resource type. The default bearer is always a non-GBR bearer, and the dedicated bearer can be configured as a GBR or non-GBR bearer. In addition to QCI and ARP, the GBR type bearer has GBR and MBR (Maximum Bit Rate) as QoS decision parameters. After QoS defined by the wireless communication system as a whole is defined as an EPS bearer, QoS is determined for each interface. Each interface establishes a bearer according to the QoS it should provide.

Hereinafter, a heterogeneous network will be described.

Simple cell segmentation of macro cells and micro cells makes it difficult to meet the growing demand for data services. Therefore, it is possible to operate the data service for small indoor and outdoor areas by using small cells such as pico cell, femto cell and wireless relay. Although the use of the small cells is not particularly limited, in general, the picocell can be used for a communication shadow area that is not covered only by a macrocell, an area where data service is required in a large amount, a so-called hot spot or a hotzone . A femto base station (femto eNB) can be generally used in an indoor office or a home. In addition, the wireless relay can compensate for the coverage of the macrocell. By configuring a heterogeneous network, not only the shadow areas of the data service can be eliminated, but also the data transmission speed can be increased.

FIG. 5 is a diagram schematically illustrating the concept of a heterogeneous network composed of a macro base station, a femto base station, and a pico base station according to the present invention. 5 illustrates a heterogeneous network composed of a macro base station, a femto base station, and a pico base station, but the heterogeneous network may include a micro, a relay, or another type of base station. In the present invention, the base station may include the macro base station, the femto base station, the pico base station, the micro base station, the relay, and other types of base stations described above.

Referring to FIG. 5, a macro base station 510, a femto base station 520, and a pico base station 530 are operated together in a heterogeneous network. The macro base station 510, the femto base station 520, and the pico base station 530 provide macrocells, femtocells, and picocells, which are their own cell coverage, to the terminal.

The femto base station 520 is a low power wireless access point, for example, a base station for ultra small mobile communication used in a room such as a home or an office. The femto base station 520 can access the mobile communication core network using a home or office DSL or cable broadband. The femto base station 520 may support a self-organization function. Self-organization functions are classified into self-configuration, self-optimization, and self-monitoring.

The femtocell can distinguish registered users from unregistered users and allow access only to registered users. (CSG), and the open user group (hereinafter referred to as "OSG ") is a group that allows access to only a registered user, and a cell that allows access only to registered users is called a closed group . It is also possible to operate these two methods in combination.

A base station that provides a femtocell service is called a home NodeB (HNB) or a home eNodeB (HeNB) in 3GPP. The femto base station 520 basically aims to provide a service specialized only to the members belonging to the CSG. In terms of providing the service, when the femto base station 520 provides services only to the CSG group, the cell provided by the femto base station 520 is referred to as a CSG cell.

Each CSG has a unique identifier, which is referred to as a CSG identity. A terminal can have a list of CSGs belonging to itself as a member. Such a CSG list is also called a whitelist. It is possible to confirm which CSG the CSG cell supports by reading the CSG ID included in the system information. The terminal that has read the CSG ID is regarded as a cell that can access the cell only when it is a member of the corresponding CSG cell, that is, when the CSG corresponding to the CSG ID is included in its own CSG whitelist.

The types of picocells provided by the pico base station 530 are called "coverage hole picocells" (hereinafter referred to as "coverage hole picocells") and "picocells for hot spots" Quot;).

The Coverage Hole Pico cell is used when a terminal can not transmit / receive data through a macro cell and a terminal transmits / receives data via a pico cell instead of a macro cell. A hotspot picocell is a device in which a terminal transmits and receives data through a picocell in place of a macrocell in order to reduce the load of the macrocell, although the terminal can transmit and receive data through the macrocell. Hot spots may also refer to areas where the population is flooded or residential, or where demand traffic is high. Generally, a hot spot region may occur irrespective of an electro-magnetic field. In this case, the pico-cell may be divided into two types, i.e., an intra-frequency pico cell and an inter-frequency pico cell. .

An intra-frequency picocell refers to a picocell that uses the same frequency band as a macrocell. By reusing the same frequency resources in spatially separated areas, the same radio resources as the macro cells can be secured within the pico cell coverage. A picocell for most coverage holes corresponds to an intra-frequency picocell.

An inter-frequency picocell is a picocell that uses a different frequency band from a macrocell. When the signal of the macro cell received in the hot spot region is strong, the performance degradation due to the interference problem between the pico cell and the macro cell may occur. And can be used when a hot spot exists at a position close to the center of the macro cell.

Generally, small cell is advantageous compared to macro cell in terms of throughput that can be provided for a single terminal because it serves a small area compared to a macro cell. However, in the current wireless communication system, once a terminal connected to a macro cell is located in a service area of a small cell, it can not receive service from a small cell without performing a handover. Also, in the case where the mobile station is moving, even if the mobile station is connected to the small cell through handover or the like, the coverage of the small cell is small, so handover frequently occurs, which is not preferable from the viewpoint of network efficiency.

Hereinafter, the embodiments of the present invention will be described in detail with reference to the embodiments of the present invention, and the embodiments of the present invention can be applied to a heterogeneous network system including a macro cell and a small cell.

One embodiment includes a method of supporting data service or load distribution through a small cell while maintaining an EPS bearer including a wireless connection between a terminal and a macro cell in a heterogeneous network system. For example, the method can be applied when the terminal connected to the macro cell is located in an over-laid area with a service area of a macro cell and a service area of a small cell. This method is referred to as a procedure for configuring multiple wireless connections. Alternatively, the method may be referred to as an extended bearer establishment procedure or a bearer extension procedure.

More specifically, in the bearer extension mode, the control plane (RRC layer, NAS) for the terminal is provided by the macrocell and the user plane is provided by the EPS bearer of the small cell.

Therefore, in the small cell area existing in the overlaid area with the macro cell, the terminal can receive the downlink signal from the small cell without handover or transmit the uplink signal to the small cell in the state of being connected to the macro cell have. Here, the downlink signal includes data of a user plane transmitted in downlink and the uplink signal includes data of a user plane transmitted in uplink. The data of the control plane is transmitted and received through the macro cell.

The extended bearer establishment procedure or the bearer extension procedure includes negotiating an extended bearer setup between a macro base station and a small base station, a macro base station used to create an RB between the small base station and the mobile station and suspend the uplink transmission, And performing a second RRC signaling between the macro base station and the UE, which is used for allowing uplink transmission to the small base station when the bearer extension is completed, have.

6 is a conceptual diagram showing a connection configuration between a macro base station and a small base station according to an example of the present invention.

Referring to FIG. 6, data is transmitted from the packet data network 600 to the P-GW 605, and the data is transmitted to the macro base station 620 via the S-GW 610. The QoS for the data may be set to a certain level. The MAC base station 620 and the terminal 640 are configured with an EPS bearer of a macro cell.

The macro base station 620 includes an RRC entity 621, a PDCP entity 622, an RLC entity 623, a MAC entity 624, and a PHY layer 625. The structure and operation of each of the above entities include the contents described in Figs. 2 and 3. The small base station 630 includes a PDCP entity 632, an RLC entity 633, a MAC entity 634, and a PHY layer 635.

In a normal mode without bearer extension, the macro base station 620 receives the data at the PDCP entity 622, processes the data based on control by the RRC entity 621, 623, the MAC entity 624, and the PHY layer 625 to the terminal 640. Although not shown in the drawing, the terminal 640 also has entities that form the EPS bearer of the macrocell. The RCP entity 622, the RRC entity 621, the RLC entity 623, the MAC entity 624, and the PHY layer 625 of the macro base station 620, the PDCP entity, the RRC entity, the RLC entity 622, , A MAC entity and a PHY layer exist on the terminal 640 side.

On the other hand, when the terminal 640 exists in the macro cell only area and moves to the overlapped small cell area, if the amount of traffic is large in the macro cell or if the user terminal needs to receive good quality (QoS) user data The extended EPS bearer for the small base station 630 and the terminal 640 can be generated. The generation of the extended EPS bearer is performed by the above-described extended bearer setup procedure. The operation mode of the small base station 630 and the terminal 640 after the extended EPS bearer is generated is called a bearer extension mode.

In the bearer extension mode, the S-GW 610 can forward the data to the PDCP entity 632 of the small base station 630 through the backhaul network. The RLC entity 633 of the small base station 630 transmits the packet to the terminal 640 via the MAC entity 634 and the PHY layer 635. [ Although not shown in the drawing, entities that form an extended EPS bearer are also created in the terminal 640. The PDCP entity 632, the RLC entity 633, the MAC entity 634, and the PHY layer 635 of the small base station 630, the PDCP entity, the RRC entity, the RLC entity, the MAC entity, and the PHY layer 635, Is present on the terminal 640 side.

In this case, the terminal 640 can receive a service through the EPS bearer of the small base station 630 that the terminal 640 has been provided with the EPS bearer of the macro base station 620. Here, the control plane (RRC layer, NAS) for the terminal is provided by the macrocell and the user plane is provided by the extended cell bearer of the small cell.

When the UE 640 using the extended EPS bearer moves beyond the coverage of the small cell to the coverage of only the previous macrocell and generates a new EPS bearer for the macro base station 620, It can be a burden to management. In this case, the method of reusing the EPS bearer of the macro cell as shown in FIG. 7 is effective according to the present embodiment.

7 is a conceptual diagram illustrating a connection configuration between a macro base station and a small base station according to another example of the present invention.

Referring to FIG. 7, a terminal 740 located in a superposed area of a macro cell and a small cell transmits and receives data of a control plane (RRC layer, NAS) using an EPS bearer of a macro cell, Data can be transmitted and received using the extended EPS bearer. The downlink data transmission path using the EPS bearer of the macro cell is the packet data network 700 to the P-GW 705 to the S-GW 710 to the RRC entity 721 to the PDCP entity 722, ≫ RLC entity 723 -> MAC entity 724 -> PHY layer 725. The downlink data delivery path using the extended EPS bearer is transmitted from the packet data network 700 to the P-GW 705 to the S-GW 710 to the PDCP entity 732 to the RLC entity 733, > MAC entity 734 -> PHY layer 735. FIG. 7 shows only the data transmission in the downlink direction by arrows, but the technical contents of FIG. 7 can also be applied to the data transmission in the uplink direction as well.

At this time, if the terminal 740 moves to the macro cell only area, the terminal 740 can not receive or transmit data on the small cell. In this case, since the EPS bearer of the macro cell does not carry data of the user plane but exists in the past, the EPS bearer of the existing macro cell carries the user plane data instead of generating the new EPS again at the macro base station 720 It is efficient to use again.

For this, even though the macro base station 720 is instructed to change the EPS bearer of the macro cell to a usable state, the UE 740 can quickly reuse the EPS bearer of the macro cell.

8 is a flowchart illustrating signaling between a terminal, a macro base station, and a small base station according to an exemplary embodiment of the present invention. The terminal can move from the superposed area of the macro cell operated by the macro base station and the small cell operated by the small base station to the area of only the macro cell as shown in FIG.

Referring to FIG. 8, the mobile station measures the signal strength of the small cell and transmits a measurement report to the macro base station when the measured signal strength satisfies a specific criterion (S800). For example, if the measured signal strength meets a certain criterion, the signal strength of the small cell must be smaller than the signal strength of the macrocell, or the signal of the small cell must be smaller than the threshold.

The macro base station determines to use the EPS bearer of the macro cell to transmit and receive data on the user plane (S805). An example of a criterion that the macro base station determines to use the EPS bearer of the macro cell includes a case where the signal of the small cell becomes weaker than the threshold value. Another example of a criterion that a macro base station determines to use an EPS bearer of a macro cell includes a case where the load of a macro cell is no longer high and the need to use an extended EPS bearer of a small cell is eliminated.

If the macro base station decides to use the EPS bearer of the macro cell instead of the extended EPS bearer, the macro base station transmits the uplink transmission using the EPS bearer of the macro cell, which has been suspended before the release of the extended EPS bearer (ULTxStartInfo) indicating the start of the RRC connection reconfiguration message to the UE (S810). The present embodiment is not limited to the case where the uplink transmission start information is transmitted in the first RRC connection reconfiguration message. That is, the uplink transmission start information may be independently transmitted separately from the first RRC connection reconfiguration message.

In addition to the UL transmission start information, the first RRC connection reconfiguration message may further include at least one of a UE ID, an EPS bearer ID of a macro cell, an identifier of an extended EPS bearer, and UL Tx reservation information (ULTxSuspendInfo).

The terminal identifier is an identification number for identifying the terminal, and may include a Cell-Radio Network Temporary Identifier (C-RNTI), an International Mobile Subscriber Identity (IMSI), a Globally Unique Temporary Identity (GUTI)

The EPS bearer identifier of the macro cell is information for identifying the EPS bearer of the macro cell formed between the macro base station and the UE.

The extended EPS bearer identifier is information for identifying the extended EPS bearer formed between the small base station and the UE.

The UL Tx reservation information (ULTxSuspendInfo) is information indicating that the uplink transmission using the extended EPS bearer is suspended. In other words, the first RRC connection reconfiguration message may include UL Tx reservation information meaning that the UE does not perform uplink transmission using the extended EPS bearer.

The MS transmits a first RRC connection reconfiguration completion message to the macro base station indicating that the wireless configuration has been changed based on the first RRC connection reconfiguration message (S815).

The UE stops using the extended EPS bearer in the uplink transmission according to the UL Tx reservation information (ULTxSuspendInfo), and uses the EPS bearer in the macrocell when transmitting or receiving the user plane data according to the UL transmission start information (ULTxStartInfo) (S820).

The macro base station transmits a Bearer Extension Release message to request release (or deletion) of the extended EPS bearer, and notifies the use of the EPS bearer of the macro cell (S825). The X2 interface may be used for delivery of the bearer extension release message. The bearer extension release message may include at least one of a terminal identifier, an EPS bearer identifier of a macro cell, and an extended EPS bearer identifier.

Upon receiving the bearer extension cancel message, the small base station can recognize that the EPS bearer of the macro cell of the macro base station is to be replaced with the extended EPS bearer. Accordingly, the small base station deletes the extended EPS bearer so as not to use the core network such as MME, S-GW, and P-GW (S830). Then, the core network changes or routes the path of the user data, which is input from the PDN to the P-GW, to the EPS bearer of the macro cell.

If the extended EPS bearer is deleted, the small base station transmits a bearer extension release complete message to the macro base station (S835). Thus, the small base station can transmit the user data, which is input to the P-GW from the PDN toward the mobile station, using the EPS bearer of the future macro cell and inform the macro base station of the fact. In addition, the bearer extension release complete message informs that the radio configuration of the small base station for the mobile station is released. The bearer extension cancellation completion message may include at least one of a terminal identifier, an EPS bearer identifier of a macro cell, and an extended EPS bearer identifier, for example. The bearer extension cancellation completion message may also mean disabling (or deactivating) the use of the extended EPS bearer, for example, an inactive EPS bearer context request message received from the core network.

In step S840, the macro base station transmits a second RRC connection reconfiguration message to the UE indicating the release of the radio configuration including the RB mapped to the extended EPS bearer. This is because the radio configuration or extended EPS bearer required for the small cell's wireless access service is released and the corresponding RB must be released.

The MS releases the RB corresponding to (or mapped to) the extended EPS bearer based on the second RRC connection reconfiguration message, and transmits a second RRC connection reconfiguration complete message indicating that the RB is completed (S845).

The macro base station transmits an RRC connection reconfiguration completion indicator to the small base station, and notifies the small base station that the mobile station has released or deleted the radio resource configuration including the RB corresponding to the extended EPS bearer in operation S850.

If the macro base station transmits only a simple instruction to the UE to change the state of the macro bearer to use the EPS bearer, the UE can quickly reuse the EPS bearer of the macro cell existing in the past, Can be provided.

9 is a flowchart illustrating an operation of a terminal according to an exemplary embodiment of the present invention.

Referring to FIG. 9, the UE transmits a measurement report to the macro base station (S900). For example, if the measured signal strength meets a certain criterion, the signal strength of the small cell must be smaller than the signal strength of the macrocell, or the signal of the small cell must be smaller than the threshold.

If it is determined by the macro base station to use the EPS bearer of the macro cell in place of the extended EPS bearer, the UE transmits the uplink transmission using the EPS bearer of the macro cell that has been suspended before the release of the extended EPS bearer From the macro base station, a first RRC connection reconfiguration message including uplink transmission start information (ULTxStartInfo) instructing to start the RRC connection reconfiguration message (S905). The present embodiment is not limited to the case where the uplink transmission start information is received in the first RRC connection reconfiguration message. That is, the uplink transmission start information may be independently received separately from the first RRC connection reconfiguration message.

In addition to the UL transmission start information, the first RRC connection reconfiguration message may further include at least one of a UE ID, an EPS bearer ID of a macro cell, an identifier of an extended EPS bearer, and UL Tx reservation information (ULTxSuspendInfo).

The terminal identifier is an identification number for identifying the terminal, and may include a Cell-Radio Network Temporary Identifier (C-RNTI), an International Mobile Subscriber Identity (IMSI), a Globally Unique Temporary Identity (GUTI)

The EPS bearer identifier of the macro cell is information for identifying the EPS bearer of the macro cell formed between the macro base station and the UE.

The extended EPS bearer identifier is information for identifying the extended EPS bearer formed between the small base station and the UE.

The UL Tx reservation information (ULTxSuspendInfo) is information indicating that the uplink transmission using the extended EPS bearer is suspended. In other words, the first RRC connection reconfiguration message may include UL Tx reservation information meaning that the UE does not perform uplink transmission using the extended EPS bearer.

The MS transmits a first RRC connection reconfiguration completion message to the macro base station indicating that the wireless configuration has been changed based on the first RRC connection reconfiguration message (S910).

The UE stops using the extended EPS bearer in the uplink transmission according to the UL Tx reservation information (ULTxSuspendInfo), and uses the EPS bearer in the macrocell when the user plane data is transmitted or received according to the uplink transmission start information (BasicULTxStartInfo) (S915).

The MS receives a second RRC connection reconfiguration message from the macro base station indicating the release of the radio configuration including the RB mapped to the extended EPS bearer (S920). This is because the radio configuration or extended EPS bearer required for the small cell's wireless access service is released and the corresponding RB must be released.

The MS releases the RB corresponding to (or mapped to) the extended EPS bearer based on the second RRC connection reconfiguration message, and transmits an RRC connection reconfiguration complete message indicating that the RB is completed (S925) to the macro base station.

10 is an operation flowchart of a macro base station according to an example of the present invention.

10, the macro base station receives a measurement report from the terminal when the signal strength of the small cell measured at the terminal satisfies a specific criterion (S1000). For example, if the measured signal strength meets a certain criterion, the signal strength of the small cell must be smaller than the signal strength of the macrocell, or the signal of the small cell must be smaller than the threshold.

The macro base station determines that the EPS bearer of the macro cell is used to transmit and receive data on the user plane (S1005). An example of a criterion that the macro base station determines to use the EPS bearer of the macro cell includes a case where the signal of the small cell becomes weaker than the threshold value. Another example of a criterion that a macro base station determines to use an EPS bearer of a macro cell includes a case where the load of a macro cell is no longer high and the need to use an extended EPS bearer of a small cell is eliminated.

If the macro base station decides to use the EPS bearer of the macro cell instead of the extended EPS bearer, the macro base station transmits the uplink transmission using the EPS bearer of the macro cell, which has been suspended before the release of the extended EPS bearer (ULTxStartInfo) indicating the start of the RRC connection reconfiguration message to the UE (S1010).

In addition to the UL transmission start information, the first RRC connection reconfiguration message may further include at least one of a UE ID, an EPS bearer ID of a macro cell, an identifier of an extended EPS bearer, and UL Tx reservation information (ULTxSuspendInfo).

The terminal identifier is an identification number for identifying the terminal, and may include a Cell-Radio Network Temporary Identifier (C-RNTI), an International Mobile Subscriber Identity (IMSI), a Globally Unique Temporary Identity (GUTI)

The EPS bearer identifier of the macro cell is information for identifying the EPS bearer of the macro cell formed between the macro base station and the UE.

The extended EPS bearer identifier is information for identifying the extended EPS bearer formed between the small base station and the UE.

The UL Tx reservation information (ULTxSuspendInfo) is information indicating that the uplink transmission using the extended EPS bearer is suspended. In other words, the first RRC connection reconfiguration message may include UL Tx reservation information meaning that the UE does not perform uplink transmission using the extended EPS bearer.

Based on the first RRC connection reconfiguration message, the macro base station receives from the terminal a first RRC connection reconfiguration completion message indicating that the UE has changed the wireless configuration (S1015).

The macro base station stops using the extended EPS bearer in the uplink transmission according to the UL Tx reservation information (ULTxSuspendInfo), and when the data of the user plane is transmitted or received according to the uplink transmission start information (BasicULTxStartInfo) And resumes use (S1020).

The macro base station transmits a bearer extension release message to request release (or deletion) of the extended EPS bearer, and notifies the use of the EPS bearer of the macro cell (S1025). The X2 interface may be used for delivery of the bearer extension release message. The bearer extension release message may include at least one of a terminal identifier, an EPS bearer identifier of a macro cell, and an extended EPS bearer identifier.

If the extended EPS bearer is deleted from the small base station and the core network, the macro base station receives a bearer extension release complete message from the small base station (S1030). Accordingly, the macro base station can know that the user data, which is input to the P-GW from the PDN toward the UE, is transmitted using the EPS bearer of the macro cell in the future. The bearer extension cancellation complete message may mean stopping and releasing (or deactivating) the use of the extended EPS bearer, for example an inactive EPS bearer context request message received from the core network.

The macro base station transmits a second RRC connection reconfiguration message to the mobile station indicating the release of the radio configuration including the RB mapped to the extended EPS bearer (S1035). This is because the radio configuration or extended EPS bearer required for the small cell's wireless access service is released and the corresponding RB must be released.

The macro base station releases the RB corresponding to (or mapped to) the extended EPS bearer based on the second RRC connection reconfiguration message, and receives from the terminal an RRC connection reconfiguration complete message indicating that the RB is completed (S1040).

Then, the macro base station transmits an RRC connection reconfiguration completion indicator to the small base station, and notifies the small base station that the terminal also releases or deletes the radio resource configuration including the RB corresponding to the extended EPS bearer (S1045).

11 is a flowchart of an operation of a small base station according to an example of the present invention.

11, the small base station receives a Bearer Extension Release message from the macro base station and requests release (or deletion) of the extended EPS bearer, and confirms that the EPS bearer of the macro cell is to be used (S1100 ). The X2 interface may be used for delivery of the bearer extension release message. The bearer extension release message may include at least one of a terminal identifier, an EPS bearer identifier of a macro cell, and an extended EPS bearer identifier.

Upon receiving the bearer extension release message, the small base station can recognize that the EPS bearer of the macrocell is to be replaced with the extended EPS bearer. Accordingly, the small base station deletes the extended EPS bearer so as not to use the core network together with the core network such as MME, S-GW, and P-GW (S1105). Then, the core network changes or routes the path of the user data, which is input from the PDN to the P-GW, to the EPS bearer of the macro cell.

If the extended EPS bearer is deleted, the small base station transmits a bearer extension release complete message to the macro base station (S1110). Thus, the small base station can transmit the user data, which is input to the P-GW from the PDN toward the mobile station, using the EPS bearer of the future macro cell, and inform the macro base station of the fact. In addition, the bearer extension release complete message informs that the radio configuration of the small base station for the mobile station is released. The bearer extension cancellation completion message may include at least one of a terminal identifier, an EPS bearer identifier of a macro cell, and an extended EPS bearer identifier, for example. The bearer extension cancellation completion message may also mean disabling (or deactivating) the use of the extended EPS bearer, for example an inactive EPS bearer context request message received from the core network.

The small base station receives the RRC connection reconfiguration completion indicator from the macro base station and recognizes that the mobile station has released or deleted the radio resource configuration including the RB corresponding to the extended EPS bearer (S1115).

12 is a block diagram illustrating a terminal, a macro base station, and a small base station according to the present invention.

Referring to FIG. 12, a terminal 1200 includes a terminal receiver 1205, a terminal processor 1210, and a terminal transmitter 1215. The macro base station 1230 includes a macro transmission unit 1235, a macro reception unit 1240, and a macro processor 1245. The small base station 1260 includes a small transmission unit 1265, a small reception unit 1270, and a small processor 1275.

The terminal processor 1210 measures the signal strength of the small cell and generates a measurement report when the measured signal strength meets a certain criterion. The transmitting unit 1215 transmits the measurement report to the macro base station 1230. For example, if the measured signal strength meets a certain criterion, the signal strength of the small cell is smaller than the signal strength of the macrocell, Or the signal of the small cell should be smaller than the threshold value.

When the terminal 1200 exists in the overlapping area of the macro cell and the small cell, the data of the control plane (RRC layer, NAS) is transmitted and received using the EPS bearer of the macro cell, The bearer can be used to transmit and receive.

At this time, when the terminal 1200 moves to the area of only the macro cell, the terminal 1200 receiving or transmitting data on the small cell is more inefficient than transmitting and receiving data on the macro cell. In this case, since the EPS bearer of the macro cell does not carry data of the user plane but exists in the past, the EPS bearer of the existing macro cell carries the user plane data instead of creating the new EPS again at the macro base station 1230 It is efficient to use again.

Accordingly, the macro processor 1245 determines to use the EPS bearer of the macro cell to transmit and receive data in the user plane. An example of a criterion by which the macro processor 1245 determines to use the EPS bearer of a macrocell includes a case where the signal of the small cell is weakened below a threshold value. Another example of a criterion by which the macro processor 1245 determines to use the EPS bearer of a macrocell includes the case where the load of the macrocell is no longer high and the need to use the small cell's expanded EPS bearer is eliminated.

If the macro processor 1245 decides to use the EPS bearer of the macro cell instead of the extended EPS bearer, the macro processor 1245 may determine that the EPS bearer of the macro cell that was inactive prior to releasing (or deleting) And transmits a first RRC connection reconfiguration message including the uplink transmission start information to the macro transmission unit 1235. The macro transmission unit 1235 transmits the first RRC connection reconfiguration message including the uplink transmission start information to the macro transmission unit 1235. [ Then, the macro transmitting unit 1235 transmits the first RRC connection reconfiguration message to the terminal 1200. The present embodiment is not limited to the case where the uplink transmission start information is transmitted in the first RRC connection reconfiguration message. That is, the uplink transmission start information may be independently transmitted separately from the first RRC connection reconfiguration message.

In addition to the UL transmission start information, the first RRC connection reconfiguration message may further include at least one of a UE ID, an EPS bearer ID of a macro cell, an identifier of an extended EPS bearer, and UL Tx reservation information (ULTxSuspendInfo).

The terminal identifier is an identification number for identifying the terminal, and may include a Cell-Radio Network Temporary Identifier (C-RNTI), an International Mobile Subscriber Identity (IMSI), a Globally Unique Temporary Identity (GUTI)

The EPS bearer identifier of the macro cell is information for identifying the EPS bearer of the macro cell formed between the macro base station 1230 and the terminal 1200.

The extended EPS bearer identifier is information for identifying the extended EPS bearer formed between the small base station 1260 and the terminal 1200.

The UL Tx reservation information (ULTxSuspendInfo) is information indicating that the uplink transmission using the extended EPS bearer is suspended. In other words, the first RRC connection reconfiguration message may include UL Tx reservation information meaning that the UE does not perform uplink transmission using the extended EPS bearer.

The terminal processor 1210 changes the wireless configuration based on the first RRC connection reconfiguration message and generates a first RRC connection reconfiguration completion message indicating that the change is completed and sends the message to the terminal transmission unit 1215. [ Then, the terminal transmission unit 1215 transmits the first RRC connection reconfiguration completion message to the macro base station 1230.

The terminal processor 1210 stops using the extended EPS bearer in the uplink transmission according to the UL Tx reservation information (ULTxSuspendInfo), and transmits the control plane data and the user plane data in accordance with the uplink transmission start information (BasicULTxStartInfo) Upon reception, the use of the EPS bearer of the macro cell is resumed.

The macro processor 1245 generates a bearer extension release message and the macro transmission unit 1235 transmits the bearer extension release message to the small base station 1260 to release (or delete) the extended EPS bearer And notifies the use of the EPS bearer of the macro cell. The X2 interface may be used for delivery of the bearer extension release message. The bearer extension release message may include at least one of a terminal identifier, an EPS bearer identifier of a macro cell, and an extended EPS bearer identifier.

When the small reception unit 1270 receives the bearer extension release message, the small processor 1275 can recognize that the EPS bearer of the macro cell of the macro base station 1230 is to be replaced with the extended EPS bearer. Accordingly, the small processor 1275 deletes the extended EPS bearer so as not to use the core network such as the MME, the S-GW, and the P-GW. Then, the small processor 1275 changes or routes the path of the user data to be transferred from the PDN to the P-GW through the EPS bearer of the macro cell.

When the extended EPS bearer is deleted, the small processor 1275 generates a bearer extension release complete message, and the small transmitting unit 1265 transmits the bearer extension cancel complete message to the macro base station 1230 . Accordingly, the small base station 1260 can transmit the user data, which is input to the P-GW from the PDN toward the mobile station, using the EPS bearer of the future macro cell and inform the macro base station 1230 of the fact. In addition, the bearer extension release complete message informs that the radio configuration of the small base station 1260 for the UE 1200 is released. The bearer extension cancellation completion message may include at least one of a terminal identifier, an EPS bearer identifier of a macro cell, and an extended EPS bearer identifier, for example. The bearer extension cancellation completion message may also mean disabling (or deactivating) the use of the extended EPS bearer, for example an inactive EPS bearer context request message received from the core network.

Upon confirming the bearer extension cancellation completion message, the macro processor 1245 generates a second RRC connection reconfiguration message indicating the release of the radio configuration including the RB mapped to the extended EPS bearer, and sends the message to the macro transmission unit 1235. The macro transmitting unit 1235 transmits a second RRC connection reconfiguration message to the terminal 1200. This is because the radio configuration or extended EPS bearer required for the small cell's wireless access service is released and the corresponding RB must be released.

When the terminal receiver 1205 receives the second RRC connection reconfiguration message and sends the second RRC connection reconfiguration message to the terminal processor 1210, the terminal processor 1210 transmits the RRC connection reconfiguration message to the terminal processor 1210 based on the second RRC connection reconfiguration message, And generates a second RRC connection reconfiguration complete message indicating that it has completed. Then, the terminal transmission unit 1215 transmits a second RRC connection reconfiguration completion message to the macro base station 1230.

The macro processor 1245 generates an RRC connection reconfiguration completion indicator and sends it to the macro transmission unit 1235. The macro transmission unit 1235 transmits an RRC connection reconfiguration completion indicator to the small base station 1260, To the small base station 1260 that the radio resource configuration including the RB corresponding to the extended EPS bearer is released or deleted.

When the macro BS 1230 transmits only a simple instruction to the UE 1200 to change the state of the macro bearer to the available state, the UE 1200 can quickly reuse the EPS bearer of the macro cell, And a seamless service can be provided.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (6)

A method for releasing a bearer extension by a terminal in a heterogeneous network system including a macro base station (Macro eNB) and a small base station (Small eNB)
And an EPS bearer of the macrocell between the macro base station and the terminal during the transmission and reception using the extended EPS (Evolved Packet System) bearer between the small base station and the terminal, Receiving link transmission start information (BasicULTxStartInfo) from the macro base station; And
And resuming transmission and reception using the EPS bearer of the macro cell based on the indication of the uplink transmission start information. The method according to claim 1,
Receiving uplink transmission reservation information (ULTxSuspendInfo) indicating suspension of uplink transmission using the extended EPS bearer from the macro base station; And
And stopping transmission and reception using the extended EPS bearer based on the indication of the uplink transmission reservation information. The method according to claim 1,
Receiving an RRC connection reconfiguration message from the macro base station indicating a radio configuration associated with the extended EPS bearer and a release of a radio bearer (RB);
Releasing the radio configuration and the radio bearer based on the RRC connection reconfiguration message; And
And transmitting an RRC connection reconfiguration completion message to the macro base station. A terminal for releasing a bearer extension in a heterogeneous network system including a macro base station and a small base station,
Uplink transmission start information for instructing to start uplink transmission using the EPS bearer of the macrocell between the macro base station and the terminal during transmission and reception using the extended EPS bearer between the small base station and the terminal A terminal receiving unit receiving from the macro base station; And
And a terminal processor for resuming transmission and reception using the EPS bearer of the macro cell based on the indication of the uplink transmission start information. 5. The method of claim 4,
The UE receiver receives uplink transmission reservation information indicating reservation of uplink transmission using the extended EPS bearer from the macro base station,
Wherein the terminal processor stops transmission and reception using the extended EPS bearer based on the indication of the uplink transmission reservation information. 5. The method of claim 4,
Wherein the terminal receiver receives from the macro base station an RRC connection reconfiguration message indicating a radio configuration associated with the extended EPS bearer and a release of a radio bearer, and the terminal processor, based on the RRC connection reconfiguration message, Release the bearer,
Further comprising a terminal transmission unit for transmitting an RRC connection reconfiguration completion message to the macro base station.

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