WO2015005741A1 - Method and apparatus for controlling data in radio link control layer in wireless communication system supporting dual connectivity - Google Patents

Abstract

The present invention provides a method of controlling a radio link control (RLC) layer in a network system supporting dual connectivity of a UE with respect to a master eNB and a secondary eNB. In the method, the master eNB transmits a first RLC PDU processed by an RLC layer of the master eNB to the UE, the secondary eNB transmits a second RLC PDU processed by an RLC layer of the secondary eNB to the UE, and at least one of first RLC sorting information, which indicates that the first RLC PDU is processed by the RLC layer of the master eNB, and second RLC sorting information, which indicates that the second RLC PDU is processed by the RLC layer of the secondary eNB, is further transmitted to the UE.

Description

Method and apparatus for controlling data in radio link control layer in wireless communication system supporting dual connectivity

The present invention relates to wireless communication, and more particularly, to a method and apparatus for data control in a radio link control (RLC) layer in a wireless communication system supporting double connectivity.

In particular areas, such as hot spots inside the cell, there is a great demand for communication, and in certain areas such as cell edges or coverage holes, the reception sensitivity of radio waves may be reduced. With the development of wireless communication technology, small cells, such as pico cells, within a macro cell for the purpose of enabling communication in areas such as hot spots, cell boundaries, and coverage holes. (Pico Cell), femto cell (Femto Cell), micro cell (Micro Cell), remote radio head (RRH), relay (relay), repeater (repeater) is installed together. Such a network is called a heterogeneous network (HetNet). In a heterogeneous network environment, a macro cell is a large coverage cell, and a small cell such as a femto cell and a pico cell is a small coverage cell. In a heterogeneous network environment, coverage overlap may occur between the plurality of macro cells and the small cells due to the location and size of the plurality of macro cells and the small cells.

The terminal may configure dual connectivity through two or more base stations among the base stations configuring at least one serving cell. Dual connectivity is an operation in which the terminal consumes radio resources provided by at least two different network points (eg, a master base station and a secondary base station) in a radio resource control connection (RRC_CONNECTED) mode. In this case, the at least two different network points may be connected by non-ideal backhaul.

In this case, one of the at least two different network points may be called a master base station (or a macro base station or an anchor base station), and the other may be called secondary base stations (or small base stations or assisting base stations or slave base stations).

The master base station may manage data flow control and security according to the Packet Data Convergence Protocol (PDCP) for data transmitted to the secondary base station through a radio bearer (RB). It is also a base station to which an S1-MME (mobility management entity) connection may be established.

The Radio Link Control (RLC) layer in the RB is a sub-entity for each eNB or one entity over multiple eNBs or a master-slave entity. It may be configured in the form of. 1) The sub-entities for each base station are sub-entities defined in the RLC layer in the RB serviced by multiple base stations. The RLC layer may be used in a structure in which each base station is independently located. Here, the sub-entity is not limited to being referred to as a substructure of the entity and may be treated the same as the entity. 2) An entity for a plurality of base stations is a single entity that resides in an RB serviced by multiple base stations. A master RLC layer may be used in a structure in which a master RLC layer is located in a master base station and a slave RLC layer is located in a secondary base station. 3) The master-slave entity is a master RLC entity and a slave RLC entity defined at the RLC layer in the RB serviced by multiple base stations. In general, the master RLC entity may be located in the master base station and perform all of the existing RLC functions, and the slave RLC entity may include only some of the functions of the master RLC entity or transmit or receive data to the terminal through the secondary base station. Only additional functions may be included.

The secondary base station transmits the data received to the master base station from the upper network to the master base station and the single base station configured in the secondary base station through the RLC layer (or XLC interface) from the PDCP layer or master RLC layer in the single RB located in the master base station. Entity) or slave RLC layer. The received data is transmitted to the terminal through an RLC layer or slave RLC layer, a medium access control (MAC) layer, and a physical layer (PHY) layer configured in the secondary base station. In addition, the data not transmitted to the secondary base station by the master base station is transmitted to the terminal through the RLC layer, MAC layer, and PHY layer in the master base station. In this case, different data is transmitted through different RLC layers configured in a plurality of base stations defined in the RB including the master base station and the secondary base station, and the amount of different data delivered to the different RLC layers is master. It may be differently assigned by the flow control method in the base station. In order to support different flow control schemes for data in a PDCP layer or a master RLC layer in the master base station, a method for classifying the data is required.

An object of the present invention is to provide a method and apparatus for data control in a radio link control layer in a wireless communication system supporting dual connectivity.

Another technical problem of the present invention is to support different flow control schemes for data in an RLC layer in a wireless communication system supporting dual connectivity.

Another technical problem of the present invention is to perform different control on each RLC layer of a master base station and a secondary base station in a wireless communication system supporting dual connectivity.

Another technical problem of the present invention is to provide a processing method for classifying data for each RLC layer of a master base station and a secondary base station.

According to an aspect of the present invention, radio connection control by the master base station (Radio) in a network system supporting dual connectivity of a master eNB and a secondary eNB to a UE Provides a data management method of the Link Control (RLC) layer. The method includes generating RLC classification information indicating that an RLC packet data unit (PDU) processed in an RLC layer is processed in the RLC layer of the master base station, and transmitting the RLC classification information to the terminal. It is characterized by.

According to another aspect of the present invention, there is provided a data management method in a radio link control (RLC) layer by a secondary base station in a network system supporting dual connectivity of a master base station and a secondary base station to a terminal. The method includes generating RLC classification information indicating that an RLC packet data unit (PDU) processed in an RLC layer is processed in an RLC layer of the secondary base station, and transmitting the RLC classification information to the terminal. It is characterized by.

According to another aspect of the present invention, there is provided a data management method of a radio link control (RLC) layer by a terminal in a network system supporting dual connectivity of a master base station and a secondary base station to a terminal. The method may include receiving at least one of a first RLC PDU (Packet Data Unit) processed at an RLC layer of the master base station and a second RLC PDU processed at an RLC layer of the secondary base station, wherein the first RLC PDU is Acquiring at least one of first RLC classification information indicating processing in an RLC layer of a master base station and second RLC classification information indicating that the second RLC PDU is processed in an RLC layer of the secondary base station, and a first RLC The first RLC PDU recognizes that the first RLC PDU has been processed in the RLC layer of the master base station based on the segmentation information, and the second RLC PDU of the secondary base station based on the second RLC segmentation information. Recognizing that the RLC layer has been processed.

According to the present invention, in a network system in which a master base station and a secondary base station configure dual connectivity to a terminal, data transmission and reception between the master base station and the terminal and the secondary base station and the terminal can be performed smoothly.

The UE may recognize which RLC PDU is received from which base station for one RB in a bearer split environment, and may perform RLC control for downlink and uplink data transmission and reception based on this. .

1 shows a wireless communication system to which the present invention is applied.

FIG. 2 is a block diagram illustrating a radio protocol architecture for a user plane.

3 is a block diagram illustrating a radio protocol structure for a control plane.

4 is a diagram illustrating an outline of an example of an RLC sublayer model to which the present invention is applied.

5 shows an example of a STATUS PDU.

6 shows an example of a dual connection situation of a terminal applied to the present invention.

7 to 10 are examples of a case in which a terminal establishes dual connectivity with a master base station and a secondary base station.

11 shows an example of an RLC header according to the present invention.

12 and 13 illustrate a UMD PDU with a 10 bit SN in accordance with the present invention.

14 is a flowchart illustrating a method of controlling an RLC layer by a master base station according to the present invention.

15 is a flowchart illustrating a method of controlling an RLC layer by a secondary base station according to the present invention.

16 is a flowchart illustrating a method of controlling an RLC layer by a terminal according to the present invention.

17 is a block diagram illustrating a master base station, a secondary base station, and a terminal for RLC layer control in a wireless communication system supporting dual connectivity according to an embodiment of the present invention.

Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings and examples, together with the contents of the present disclosure. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even though they are shown in different drawings. In addition, in describing the embodiments of the present specification, when it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present specification, the detailed description thereof will be omitted.

In addition, the present specification describes a wireless communication network, the operation performed in the wireless communication network is performed in the process of controlling the network and transmitting data in the system (for example, the base station) that is in charge of the wireless communication network, or the corresponding wireless Work may be done at the terminal coupled 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. The E-UMTS system may be an Evolved-UMTS Terrestrial Radio Access (E-UTRA) or Long Term Evolution (LTE) or LTE-A (Advanced) system. Wireless communication systems include Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA (SC-FDMA), and OFDM-FDMA Various multiple access schemes such as OFDM, TDMA, and OFDM-CDMA may be used.

Referring to FIG. 1, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) is a base station providing a control plane (CP) and a user plane (UP) to a user equipment (UE) 10. (20; evolved NodeB: eNB).

The terminal 10 may be fixed or mobile and may be called by other terms such as mobile station (MS), advanced MS (AMS), user terminal (UT), subscriber station (SS), and wireless device (Wireless Device). .

The base station 20 generally refers to a station communicating with the terminal 10, and includes a base station (BS), a base transceiver system (BTS), an access point, and a femto-eNB. It may be called other terms such as a pico base station (pico-eNB), a home base station (Home eNB), a relay (relay). The base stations 20 are physically connected through an optical cable or a digital subscriber line (DSL), and may exchange signals or messages with each other through an X2 interface. Hereinafter, a description of the physical connection will be omitted and replaced with a description of the logical connection. As described above, the base station 20 connects with an Evolved Packet Core (EPC) 30 through the S1 interface, more specifically, a Mobility Management Entity (MME) and an S1-GW (Serving Gateway) through S1-MME. do. The S1-MME interface exchanges signals with the MME to exchange context information of the terminal 10 and information for supporting mobility of the terminal 10. In addition, S-GW and data to be serviced to each terminal 10 through S1-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway (P-GW). The MME has access information of the terminal 10 or information on the capability of the terminal 10, and this information is mainly used for mobility management of the terminal 10. The S-GW is a gateway having an E-UTRAN as an endpoint, and the P-GW is a gateway having a PDN (Packet Data Network) as an endpoint.

Integrating the E-UTRAN and the EPC 30 may be referred to as an EPS (Evoled Packet System), and the traffic flows from the radio link that the terminal 10 connects to the base station 20 to the PDN connecting to the service entity are all IP. It works based on (Internet Protocol).

The radio interface between the terminal and the base station is called a Uu interface. Layers of the radio interface protocol between the terminal and the network are the first layer L1 and the second layer L2 defined in a 3GPP (3rd Generation Partnership Project) series communication system (UMTS, LTE, LTE-Advanced, etc.). ), And may be divided into a third layer L3. Among these, the physical layer belonging to the first layer provides an information transfer service using a physical channel, and the RRC (Radio Resource Control) layer located in the third layer exchanges an RRC message for the UE. Control radio resources between network and network.

FIG. 2 is a block diagram showing a radio protocol architecture for a user plane, and FIG. 3 is a block diagram showing a radio protocol architecture for a control plane. The user plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

2 and 3, a physical layer (PHY) layer provides an information transfer service to a higher 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 transmitted through a transport channel between the MAC layer and the physical layer. Transport channels are classified according to how data is transmitted over the air interface.

In addition, data is transmitted through a physical channel between different physical layers (ie, between physical layers of a transmitter and a receiver). The physical channel may be modulated by an orthogonal frequency division multiplexing (OFDM) scheme and utilizes space generated by time, frequency, and a plurality of antennas as radio resources.

For example, the physical downlink control channel (PDCCH) of the physical channel informs the UE of resource allocation of a paging channel (PCH) and 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 resource allocation of uplink transmission. In addition, a physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs and is transmitted every subframe. In addition, the PHICH (physical hybrid ARQ Indicator Channel) carries a HARQ ACK / NAK signal in response to uplink transmission. In addition, the physical uplink control channel (PUCCH) carries uplink control information such as HARQ ACK / NAK, scheduling request, and CQI for downlink transmission. In addition, a physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH). The PUSCH may include channel state information (CSI) information such as HARQ ACK / NACK and CQI when necessary according to the configuration and request of a base station.

The MAC layer may perform multiplexing or demultiplexing into a transport block provided as a physical channel on a transport channel of a MAC service data unit (SDU) belonging to the logical channel and mapping between the logical channel and the transport channel. The MAC layer provides a service to a Radio Link Control (RLC) layer through a logical channel. The logical channel may be divided into a control channel for transmitting control region information and a traffic channel for delivering user region information.

Functions of the RLC layer include concatenation, segmentation, and reassembly of RLC SDUs. In order to guarantee the various quality of service (QoS) required by the radio bearer (RB), the RLC layer has a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (Acknowledged Mode). Three modes of operation (AM).

The RLC SDUs are supported in various sizes, and for example, may be supported in units of bytes. RLC protocol data units (PDUs) are defined only when a transmission opportunity is notified from a lower layer (eg, MAC layer), and when the transmission opportunity is notified, the RLC PDUs are delivered to the lower layer. The transmission opportunity may be informed with the size of the total RLC PDUs to be transmitted. In addition, the transmission opportunity and the size of the total RLC PDUs to be transmitted may be separately reported. Hereinafter, the RLC layer will be described in detail with reference to FIG. 4.

Functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include delivery of user data, header compression, and ciphering. Functions of the PDCP layer in the user plane include the transfer 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 configuration, re-configuration, and release of RBs. RB means a logical path provided by the first layer (PHY layer) and the second layer (MAC layer, RLC layer, PDCP layer) for data transmission between the terminal and the 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 operation method. The RB may be further classified into a signaling RB (SRB) and a data RB (DRB). The SRB is used as a path for transmitting RRC messages and non-access stratum (NAS) messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

The NAS layer is located above the RRC layer and performs functions such as session management and mobility management.

If 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 it is in an RRC idle state.

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

It is located above the transport channel, and the logical channel mapped to the transport channel is a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic (MTCH). Channel).

The physical channel is composed of several symbols in the time domain and several sub-carriers in the frequency domain. One sub-frame consists of a plurality of OFDM symbols in the time domain. One subframe consists of a plurality of resource blocks, and one resource block consists of a plurality of OFDM symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific symbols (eg, the first symbol) of the corresponding subframe for the physical downlink control channel (PDCCH). The transmission time interval (TTI), which is a unit time for transmitting data, is 1 ms corresponding to one subframe.

4 is a diagram illustrating an outline of an example of an RLC sublayer model to which the present invention is applied.

Referring to FIG. 4, certain RLC entities are classified into different RLC entities according to data transmission schemes. For example, there is a TM RLC entity 400, a UM RLC entity 420, and an AM RLC entity 440.

The UM RLC entity 400 may be configured to receive or forward RLC PDUs over logical channels (eg, DL / UL DTCH, MCCH or MTCH). In addition, the UM RLC entity may deliver or receive a UMD PDU (Unacknowledged Mode Data PDU).

The UM RLC entity consists of a sending UM RLC entity or a receiving UM RLC entity.

The transmitting UM RLC entity receives the RLC SDUs from the upper layer and sends the RLC PDUs to the peer receiving UM RLC entity via the lower layer. When a transmitting UM RLC entity constructs UMD PDUs from RLC SDUs, the total size of the RLC PDUs indicated by the lower layer is segmented or concatenated into RLC SDUs when a particular transmission opportunity is notified by the lower layer. The UMD PDUs are configured to be within and the related RLC headers are included in the UMD PDU.

The receiving UM RLC entity delivers the RLC SDUs to the upper layer and receives the RLC PDUs from the peer receiving UM RLC entity through the lower layer. When the receiving UM RLC entity receives the UMD PDUs, the receiving UM RLC entity detects whether the UMD PDUs have been received in duplicate, discards the redundant UMD PDUs, and when the UMD PDUs are received out of sequence. Reorder the UMD PDUs, detect loss of UMD PDUs in the lower layer to avoid excessive reordering delays, reassemble RLC SDUs from the rearranged UMD PDUs, and In addition, the reassembled RLC SDUs are delivered to an upper layer in an ascending order of an RLC sequence number, and UMD PDUs cannot be reassembled into an RLC SDU due to a loss of UMD PDUs belonging to a specific RLC SDU in a lower layer. Can be discarded. Upon RLC re-establishment, the receiving UM RLC entity will reassemble the RLC SDUs from the received UMD PDUs, if possible, out of sequence and forward them to the higher layer, and the remaining UMD PDUs that could not be reassembled into RLC SDUs are Discard all, initialize the relevant state variables and stop the associated timers.

Meanwhile, the AM RLC entity 440 may be configured to receive or deliver RLC PDUs through logical channels (eg, DL / UL DCCH or DL / UL DTCH). The AM RLC entity delivers or receives AMD (AM data) PDUs or AMD PDU segments, and delivers or receives RLC control PDUs (eg, STATUS PDUs).

AM RLC entity 440 delivers STATUS PDUs to peer AM RLC entities to provide positive and / or negative acknowledgment of RLC PDUs (or portions thereof). This may be called STATUS reporting. A polling procedure may be involved from the peer AM RLC entity to trigger STATUS reporting. That is, an AM RLC entity may poll the peer AM RLC entity to trigger STATUS reporting at its peer AM RLC entity.

If a STATUS report is triggered and the t-StatusProhibit is not running or has expired, the STATUS PDU is sent at the next transmission opportunity. Accordingly, the UE estimates the size of the STATUS PDU and considers the STATUS PDU as data available for transmission in the RLC layer.

5 shows an example of a STATUS PDU.

Referring to FIG. 5, a STATUS PDU includes a STATUS PDU payload and an RLC control PDU header.

The RLC control PDU header includes a Data / Control (D / C) field and a Control PDU Type (CPT) field. The D / C field indicates whether the corresponding RLC PDU is an RLC data PDU or an RLC control PDU. For example, when the D / C field value is 0, it may be interpreted as an RLC control PDU, and when the D / C field value is 1, it may be interpreted as an RLC data PDU. The CPT field indicates the type of the RLC control PDU. For example, when the CPT field value is 000, it may be interpreted as a STATUS PDU.

The STATUS PDU payload starts with the first bit of the RLC control PDU header. The STATUS PDU payload includes an Acknowledgment Sequence Number (ACK_SN) field and an Extentsion bit 1 (E1) field. And the STATUS PDU payload includes zero or more sets of NACK_SN (Negative Acknowledgement SN) field, E1 field, and Extension bit 2 (E2) field. The STATUS PDU payload preferably includes a SOstart (SO (Segment Offset) start) and SOend (SO End) set for each NACK_SN. One to seven padding bits may be included at the end of a STATUS PDU as needed for octet alignment.

The ACK_SN field indicates a sequence number (SN) of a next not received RLC Data PDU, where the RLC Data PDU is not reported as missing in the STATUS PDU. When the transmitter of an AM RLC entity receives a STATUS PDU, all AMD PDUs that do not contain AMD PDUs with SN equal to ACK_SN are interpreted as being received at the peer AM RLC entity. In this case, however, AMD PDUs indicated by NACK_SN in the STATUS PDU or AMD PDUs indicated by NACK_SN, SOstart, and SOend in the STATUS PDU are excluded. That is, AMD PDUs indicated by NACK_SN in a STATUS PDU or portions of AMD PDUs indicated by NACK_SN, SOstart, and SOend in a STATUS PDU are interpreted as not being received at the peer AM RLC entity. For example, the ACK_SN field may be 10 bits long.

The NACK_SN field indicates the SN of an AMD PDU (or a portion of the AMD PDU) that has been detected as lost at the receiver of the AM RLC entity. For example, the NACK_SN field may be 10 bits long.

The E1 field indicates whether the NACK_SN, E1, and E2 sets follow. For example, the E1 field may be configured to be 1 bit in length, and when the E1 field value is 0, the NACK_SN, E1, and E2 sets are not followed. When the E1 field value is 1, the NACK_SN, E1, And E2 followed by a set.

The E2 field indicates whether the S0start and SOend sets follow. For example, the E2 field may be configured to be 1 bit long. If the E2 field value is 0, the SOstart and SOend sets do not follow the corresponding NACK_SN. If the E2 field value is 1, the SOstart and SOend sets indicate the corresponding NACK_SN. It is interpreted as following.

The SOstart field (along with the SOend field) identifies the portion of the AMD PDU that has the same SN as NACK_SN (where NACK_SN is related to SOstart) that has been detected at the receiver of the AM RLC entity. Instruct. In particular, the SOstart field indicates the position of the first byte of the portion of the AMD PDU in bytes within the data field of the AMD PDU. For example, the SOstart field may be configured to have 15 bits in length.

The SOend field indicates the portion of the AMD PDU that has the same SN as NACK_SN (where NACK_SN is related to SOend) detected as a loss at the receiver of the AM RLC entity (along with the SOstart field). In particular, the SOend field indicates the position of the last byte of the portion of the AMD PDU in the bytes in the data field of the AMD PDU. For example, the SOend field may be configured to be 15 bits long.

Meanwhile, the AM RLC entity is composed of a transmitting side and a receiving side.

The transmitter of the AM RLC entity receives the RLC SDUs from the upper layer and sends the RLC PDUs to the peer AM RLC entity via the lower layer. When the transmitter of the AM RLC entity configures AMD PDUs from the RLC SDUs, it subdivides the RLC SDUs to fit within the total size of the RLC PDU (s) indicated by the lower layer when a particular transmission opportunity is notified by the lower layer. (segment) concatenate AMD PDUs. The transmitter of the AM RLC entity supports retransmission (ARQ based) of RLC data PDUs. If the RLC data PDU to be retransmitted does not fit within the total size of the RLC PDU (s) indicated by the lower layer when a particular transmission opportunity is informed by the lower layer, in particular of the RLC data PDU that was transmitted before the total size If the size is large, the AM RLC entity re-segments the RLC data PDU into AMD PDU segments.

At this time, the number of re-segmentation is not limited. When the transmitter of the AM RLC entity creates AMD PDUs from RLC SDUs received from the upper layer or AMD PDU segments from RLC data PDUs to be retransmitted, the relevant RLC headers are included in the RLC data PDU.

The receiver of the AM RLC entity delivers the RLC SDUs to the upper layer and receives the RLC PDUs from the peer AM RLC entity via the lower layer.

When the receiver of the AM RLC entity receives the RLC data PDUs, it detects whether the RLC data PDUs have been received in duplicate, discards the duplicate RLC data PDUs, and receives the RLC data PDUs out of sequence. Reorder the order of RLC data PDUs, detect the loss of RLC data PDUs occurring in the lower layer, request retransmission to the peer AM RLC entity, and reassemble RLC SDUs from the rearranged RLC data PDUs. reassemble, and deliver the reassembled RLC SDUs to a higher layer in sequence.

When resetting the RLC, the receiver of the AM RLC entity, possibly out of sequence, reassembles the RLC SDUs from the received RLC data PDUs and delivers them to the higher layer, all remaining RLC data PDUs that cannot be reassembled into RLC SDUs. Discard it, initialize the relevant state variables and stop the associated timers.

The following table shows an example of services provided to a higher layer by RLC.

Table 1 TM data transfer UM data transfer AM data transfer, including indication of successful delivery of upper layers PDUs

The following table shows an example of services provided in a lower layer (ie, MAC) that an RLC can receive.

TABLE 2 Data transfer Transmission opportunity notification along with the total size of the RLC PDU (s) to be transmitted in the transmission opportunity

The following table shows an example of functions supported by the RLC sublayer.

TABLE 3 Transfer of upper layer PDUs Error correction through ARQ, but only for AM data transfer; Concatenation, segmentation and reassembly of RLC SDUs, but only for UM and AM data transfer. Re-segmentation of RLC data PDUs. Applies only to AM data transmission. Reordering of RLC data PDUs. Applies only to UM and AM data transfers. Duplicate detection. Applies only to UM and AM data transfers. RLC SDU discard. Applies only to UM and AM data transfers. RLC re-establishment Protocol error detection. Applies only to AM data transmission.

On the other hand, for buffer state reporting (BSR) of the MAC, the UE (UE) should consider the following as data available for transmission in the RLC layer. RLC SDUs, or segments of the RLC SDUs, that are not yet included in an RLC data PDU. And RLC data PDUs, or portions of the RLC data PDUs, waiting for retransmission (RLC AM).

Meanwhile, the RLC-Congig information element used in the RRC layer to specify the RLC configuration of the SRBs and the DRBs may include a syntax as shown in the following table. The RLC-Config information element may be included in an RRC message.

Table 4

Referring to Table 4, the maxRetxThreshold field is a parameter for RLC AM and is a maximum retransmission threshold. When the number of retransmissions for a specific RLC PDU reaches the threshold, the UE declares a radio link failure (RLF) and notifies the RRC layer thereof. The value t1 corresponds to retransmission 1 and the value t2 corresponds to retransmission 2.

The pollByte field is a parameter for determining whether a poll can be included in a specific RLC PDU as a parameter for RLC AM. The value kB25 corresponds to 25 kilobytes (kBytes), the value kB50 corresponds to 50 kilobytes, and kBInfinity corresponds to an infinite amount of kilobytes.

The pollPDU field is a parameter for RLC AM that determines whether 'pol' can be included in a specific RLC PDU. The value p4 corresponds to 4 PDUs, the value p8 corresponds to 8 PDUs, and pInfinity corresponds to an infinite number of PDUs.

The sn-FieldLength field indicates the UM RLC SN field size. The value size5 means 5 bits and size10 means 10 bits.

The t-PollRetransmit field is a timer that defines the time to wait for retransmission of a 'pol' transmitted for the purpose of triggering a STATUS report including ACK / NACK information in a peer RLC AM entity. Herein, the method of transmitting the 'pole' is a method of setting the 'p' bit in a specific RLC PDU to '1'. The value ms5 means 5 ms (milliseconds) and the value ms10 means 10 ms.

The t-Reordering field is a parameter of a timer that defines a time to wait for reordering. The value ms0 means 0ms and the value ms5 means 5ms.

The t-StatusProhibit field is a parameter of a timer that defines a time interval for prohibiting STATUS reporting. The value ms0 means 0ms and the value ms5 means 5ms.

Hereinafter, a dual connection situation to which the present invention is applied will be described.

6 shows an example of a dual connection situation of a terminal applied to the present invention.

Referring to FIG. 6, a terminal 650 located in a service area of a cell (hereinafter, referred to as a master cell) in a master base station (macro base station or anchor base station 600) is a secondary base station (small base station or assisting base station). In this case, the mobile station enters an area overlaid with the service area of the cell (hereinafter, referred to as a secondary cell).

In order to support additional data service through the secondary cell in the secondary base station 610 while maintaining the existing wireless connection and data service connection through the master cell in the master base station 600, the network provides a dual connection to the terminal 650. Configure.

Accordingly, the user data arriving at the master base station 600 may be transmitted to the terminal 650 through the secondary cell in the secondary base station 610. Specifically, for example, when the F2 frequency band is assigned to the master cell of the master base station 600, and the F1 frequency band is allocated to the secondary cell of the secondary base station 610, the terminal is a F2 frequency band from the master base station 600 At the same time, the service can be received from the secondary base station 610 through the F1 frequency band. In the above example, the master base station 600 uses F2 and the secondary base station 610 has been described as using the F1 frequency band. However, the present invention is not limited thereto, and both the master base station 600 and the secondary base station 610 have the same F1 or F2 frequency. It is also possible to use bands.

The present invention proposes a method for establishing and operating an inter-base station connection for transmitting user data arriving at a master cell in a master base station to a user equipment through a secondary cell in a secondary base station based on the RLC stage. .

In the present invention, the RRC connection establishment is configured for the PDCP / RLC layer in the process of adding the connection establishment through the cell in the secondary base station (secondary cell) while the RRC connection establishment is through the cell in the master base station (master cell). The case will be described based on the case. In this case, a DRB structure is set for data transmission / reception through a single RB based on the dual connectivity. In the DRB structure, the PDCP / RLC layer is applicable to both the above-described UM (Unacknowledged Mode) and AM (Acknowledged Mode).

7 to 10 are examples of a case in which a terminal establishes dual connectivity with a master base station and a secondary base station. In particular, FIGS. 7 through 10 are bearer split cases serving through a master base station and a secondary base station in a single RB. The bearer split may be referred to as multi-flow, multiple node (eNB) transmission, inter-eNB carrier aggregation, or the like. Of course, the fact that bearer splitting is possible does not exclude the case where the bearer splitting is not.

Referring to FIG. 7, the master base station includes a PDCP, RLC, MAC, and PHY layers, but the secondary base station includes an RLC, MAC, and PHY layers.

The PDCP layer of the master base station is connected to the RLC layer of the secondary base station using the Xn interface protocol through the backhaul. For example, the Xn interface protocol may be an X2 interface protocol defined between base stations in the LTE system.

The PDCP layer of one master base station is connected to both the RLC layer of the master base station and the RLC layer of the secondary base station.

That is, the RLC layer of the master base station may be referred to as # 1 sub-entity, and the RLC layer of the secondary base station may be referred to as # 2 sub-entity. Here, a sub-entity means that transmission and reception are divided into one-to-one matching. The sub-entity may be called an entity. The RLC layer is in duplicate form. Each sub-entity is independent but there are two sub-entities (# 1 sub-entity and # 2 sub-entity) within one RB (ie # 1 RB).

In this case, RLC parameters should be configured separately for the RLC-AM # 1 sub-entity and the RLC-AM # 2 sub-entity, respectively. Because delay time that occurs when data serviced through each RLC-AM sub-entity is delivered to the UE may be different, timer values to be set in consideration of the delay time may be set for each sub-entity. This may be different from each other. If the delay times of data transmitted through each sub-entity are the same, values of timers to be set for each sub-entity may be the same. This may be determined at the master base station, at a secondary base station, or at a network including a master base station and a secondary base station. Thus, data to be delivered via PDCP in the same RB may be transmitted on one sub-entity of either an RLC-AM # 1 sub-entity or an RLC-AM # 2 sub-entity. Here, an identifier may be further transmitted by the terminal that receives the data to identify which sub-entity the data is transmitted through.

The example of FIG. 7 is also called a sub-entity RLC type in a multi-flow case. However, the example of FIG. 7 does not necessarily apply only to multiflow.

Referring to FIG. 8, the master base station includes a PDCP, RLC, MAC, and PHY layers, but the secondary base station includes an RLC, MAC, and PHY layers. The RLC layer of the master base station is connected to the RLC layer of the secondary base station using the Xn interface protocol over the backhaul.

The RLC layer of the secondary base station is connected to the RLC layer of the master base station. Therefore, two base stations are controlled through one RB (that is, RB # 1). In this case, the RLC layer of the master base station is called a master RLC layer, and the RLC layer of the secondary base station is called a slave RLC layer.

In the case of downlink, additional division is possible for the AMD / UM PDU of the slave RLC layer of the UE. The splitting operation of the slave RLC includes a grouping of a plurality of RLC PDUs or a grouping of AMD PDU segments divided in a master RLC. In addition, it is possible to recombine the AMD / UM PDU of the slave RLC layer of the base station.

In the uplink, data received through the slave RLC layer is forwarded to the master RLC layer. If there is no data delivered to the slave RLC layer, the transmission between the terminal and the base station may be a single transmission instead of the TDM transmission.

The MAC scheduler is mainly responsible for scheduling radio resources, and the situation of the MAC layer of the macro base station is different from that of the small base station. The master RLC layer allocates (or splits, concatenates or recombines) PDUs based on the MAC layer of the macro base station, and the slave RLC layer performs partitioning or concatenation based on the MAC layer of the small base station.

In the uplink, only one RLC layer exists from the terminal's point of view. In downlink, since the MAC layer is different and a difference occurs in the radio situation, the UE is partitioned. In the uplink, a dual-connected terminal includes only one RLC layer. In this case, the slave RLC layer of the base station performs only a forwarding function and may perform uplink transmission only to the macro base station (this is called a single uplink). In this case, ACK / NACK of the RLC layer may also be transmitted only to the macro base station.

Although there is only one RLC layer in the terminal position in the uplink in FIG. 8, for example, as in the case of downlink as in FIG. As shown in FIG. 10, even in the downlink, only one RLC layer may be present from the UE's point of view.

8 to 10 may also be referred to as a master-slave RLC type among bearer split cases. However, the example of FIGS. 8 to 10 is not necessarily applied only to bearer splitting.

As described above, the terminal may be dual-connected with the master base station and the secondary base station, and may transmit and receive data in a bearer split format. In the case of a control plane (ie, generation and transmission of RRC signaling), bearer splitting for an SRB (eg, SRB2) may be configured, and in this case, the same manner as in the above-described user plane may be applied. The SRB2 is an SRB capable of transmitting not only an RRC message including logged measurement information but also information about a NAS message together with the RRC message.

The secondary base station transmits data received from the PDCP layer or the master RLC layer in a single RB of the master base station to the terminal through the RLC layer or to the terminal through the slave RLC layer, MAC layer, and PHY layer. In this case, flow control for data in the RLC layer is different according to different RLC configuration information that can be defined in a plurality of base stations defined in the RB. In order to support different flow control schemes for the data in the RLC layer, a method for classifying the data is required.

Hereinafter, the present invention proposes a method of dividing the data to support a bearer splitting scheme for transmitting data through a plurality of RLCs configured of UM or AM in the single RB.

1. When separated by the insertion of a new RLC header field

The data can be distinguished by adding an RLC header field in the RLC layer indicating whether the corresponding data is processed in the master RLC (or RLC # 1 sub-entity) or the slave RLC (or RLC # 2 sub-entity).

11 shows an example of an RLC header according to the present invention.

Referring to FIG. 11, the RLC header includes a master / slave (M / S) field, a slave processing indicator (SPI) field, a framing info (FI) field, an extension bit (E) field, a sequence number (SN) field, and an LSF. (Last Segment Flag) field, and SO (Segment Offset) field. Here, at least one of the E field, the F1 field, and the LSF field may be omitted.

The FI field indicates whether the RLC SDU has been segmented at the beginning and / or at the end of the data field. In particular, the FI field indicates whether the first byte of the data field corresponds to the first byte of the RLC SDU, and whether the last byte of the data field corresponds to the last byte of the RLC SDU. For example, the FI field may be configured to be 2 bits long.

The E field indicates whether the data field follows or the E field and the LI (Length Indicator) field. For example, the E field may be configured to be 1 bit long.

The LI field may indicate the length in bytes of the corresponding data field element present in the RLC data PDU transmitted / received by the UM or AM RLC entity. The first LI present in the RLC data PDU header corresponds to the first data field element present in the data field of the RLC data PDU, and the second LI present in the RLC data PDU header is present in the data field of the RLC data PDU. Corresponding to the second data field element, and so on.

The LSF field indicates whether the segment by the AMD PDU segment or the slave RLC corresponds to the last byte of the AMD PDU or the AMD PDU segment or the UMD PDU.

The SN field indicates a sequence number of a corresponding UMD PDU or AMD PDU. For an AMD PDU segment, the SN field indicates the sequence number of the original AMD PDU that was constructed from the AMD PDU segment. The SN field is incremented by 1 for every UMD PDU or AMD PDU. For example, the SN field may be 10 bits long for the AMD PDU and the AMD PDU segment, and may be 5 bits or 10 bits long for the UMD PDU.

The SO field indicates the position of the AMD PDU segment in bytes within the original AMD PDU. In particular, in some cases, the SO field may indicate the location of the original AMD PDU, or the AMD PDU segment, or the corresponding first byte within the data field of the UMD PDU. For example, the SO field may be configured to be 15 bits long.

On the other hand, as for the length of the bits constituting the SN field and SO field, a bit length from 0 bit to 15 bits may be considered unlike the above examples. The length of the bit may be determined in consideration of at least one of various characteristics such as transmission / reception throughput / base station and available buffer size / service type / network configuration of the corresponding wireless communication system.

The M / S field indicates whether the corresponding RLC PDU is transmitted in the master RLC (or RLC # 1 sub-entity) or the slave RLC (or RLC # 2 sub-entity). In this case, even if there are a plurality of slave RLCs, since a single slave RLC layer of the UE can recognize the parallel reception form, the same can be applied to the plurality of slave RLCs. For example, the M / S field may be configured to have a length of 1 bit. As shown in Table 5, if the field value is 0, it is a master RLC (or RLC # 1 sub-entity). If the field value is 1, the slave RLC (or RLC # 2 sub-entity).

Table 5 Value Description 0 Master RLC One Slave RLC

The SPI field is a field indicating the processing method when the RLC PDU is processed in the slave RLC. For example, the SPI field may be 2 bits long, and is reserved when the field value is 00 as shown in Table 6 below, no procedure when the field value is 01, and segmentation when the field value is 10, If the field value is 11, it may be interpreted as concatenation.

Table 6 Value Description 00 Reserved 01 No process 10 Segmentation 11 Concatenation

Alternatively, the SPI field may be configured to be 1 bit long. In this case, when the field value is 0, it may be interpreted as segmentation, and when the field value is 1, it may be interpreted as concatenation.

On the other hand, when the SPI field value indicates "concatenation", the field interpretation in the header proposed in the present invention may be changed. In more detail, the SN field may be interpreted to mean the number of corresponding concatenated RLC PDUs (or segments). In this case, the SN field may be changed to another field name such as a number of concatenated packets (NCPs). In addition, the SO field may be interpreted as indicating the length of data of the concatenated RLC PDU in the form of bytes. Therefore, in this case, there may be as many SO fields as indicated by the SN field. In this case, the SO field may be changed to another field name such as a volume indicator (VI). Alternatively, the SO field may be interpreted to indicate the position of the n th RLC PDU. In this case, the SO field may be changed to another field name such as a length indicator (LI). When the SPI field value indicates concatenation, the E field, the FI field, and the LSF field may be omitted.

The new RLC header may further include a header including only an M / S field for the RLC PDU or RLC PDU segment processed in the master RLC. In this case, 7 bits other than 1 bit added to configure the M / S field may be set as reserved bits. In addition, a header including an M / S field, an SPI field, an SN field, and an SO field may be further configured for an RLC PDU or an RLC PDU segment processed in a slave RLC. Here, the SN field may not be included in the header added for the RLC PDU or RLC PDU segment processed in the slave RLC.

2. When changing or using existing RLC header field value

In the case of a UMD PDU having a 10-bit length SN, there are three reserved bit (R1) fields in the RLC header. Accordingly, at least one of the R1 fields may be replaced with a sub-Entity Indicator (SEI) to indicate whether the corresponding UMD PDU is data processed in the RLC layer of the master base station or the RLC layer of the secondary base station.

12 and 13 illustrate a UMD PDU with a 10 bit SN in accordance with the present invention. LI may be represented by LI ₁ , LI ₂ ,..., LI _k-1 , LI _k , and FIG. 12 is a case where LI is an odd number (ie, K = 1,3, 5, ...), and FIG. 13 is the case where LI is an even number (i.e., K = 2,4,6, ...).

12 and 13, the SEI field indicates whether the corresponding UMD PDU is data processed by the master base station or the secondary base station. In other words, the SEI field may indicate whether the corresponding UMD PDU is processed in the master RLC (or RLC # 1 sub-entity) or the slave RLC (or RLC # 2 sub-entity). For example, when the SEI field is 1 bit long and the field value is 0, it indicates that the corresponding UMD PDU has been processed in the master RLC (or RLC # 1 sub-entity). When the field value is 1, the corresponding UMB PDU May indicate that it has been processed at a slave RLC (or RLC # 2 sub-entity).

3. When classified by implicit method

Using RRC signaling, it is possible to distinguish whether the corresponding data has been processed in the RLC layer of the master base station or implicitly processed in the RLC layer of the secondary base station. For example, specific SNs processed at the RLC layer of the master base station (ie, master RLC or RLC # 1 sub-entity) or at the RLC layer of the secondary base station (ie, slave RLC or RLC # 2 sub-entity) based on RRC signaling. The terminal can distinguish them. Alternatively, the UE may distinguish that specific data is processed only in the RLC layer of the master base station or the RLC layer of the secondary base station based on the RRC signaling. Such discrimination information may be included in, for example, an RLC-config information element of RRC signaling.

As an example, the master base station or the secondary base station capable of performing RRC signaling may transmit related configuration information to the terminal through RRC signaling for a function including at least one of the following schemes.

TABLE 7 1. Odd / Even SN Based 2. Use only RLC # 1 sub-entities or master RLC 3, use only RLC # 2 sub-entities or slave RLC 4. Segment based on SN with ratio equal to 3: 1/7: 1/15: 1 (using binary based last 2 digits / 3 digits / 4 digits)

14 is a flowchart illustrating a method of controlling an RLC layer by a master base station according to the present invention. In FIG. 14, the master base station and the secondary base station support dual connectivity for the terminal. In FIG. 14, it is assumed that a master base station and a secondary base station have bearer splitting configured for data transmission and reception for one RB. For example, the master base station may be a macro base station, and the secondary base station may be a small base station. However, as an example, the small base station may be the master base station, and the macro base station may be the secondary base station.

Referring to FIG. 14, the master base station generates an RLC PDU in the RLC layer (S1400). The master base station may receive a PDCP PDU (ie, RLC SDU) from the PDCP layer, which is the upper layer in the RLC layer, perform a processing procedure such as partitioning or concatenation based on this, and generate an RLC PDU by attaching an RLC header.

The master base station generates RLC classification information indicating that the RLC PDU is processed in the RLC layer of the master base station (S1410). That is, the RLC classification information indicates that the RLC PDU is processed in the RLC layer of the master base station in a bearer split environment. The RLC classification information may be called first RLC classification information.

For example, the RLC classification information may be a newly added RLC header. For example, the RLC header may include a structure and a field as shown in FIG. 11 described above. Specifically, for example, the RLC header may include an M / S field indicating whether the corresponding RLC PDU is processed in the master RLC or the slave RLC.

As another example, the RLC classification information may be at least one of the first three bits of the RLC header of the UMD PDU when the RLC PDU is a UMD PDU having a 10-bit length SN. For example, as described above with reference to FIGS. 12 and 13, at least one of the first three bits of the RLC header of the UMD PDU is processed in the RLC layer of the secondary base station whether the corresponding UMD PDU is processed in the RLC layer of the master base station. It may include an SEI indicating whether or not.

As another example, the RLC classification information may be transmitted to the terminal through RRC signaling. For example, the RLC classification information may indicate that an RLC PDU of a specific SN is processed in an RLC layer of the master base station. Specifically, for example, the RLC classification information may indicate that RLC PDUs of odd or even SNs are processed in the RLC layer of the master base station. Alternatively, the RLC classification information may indicate that all RLC PDUs are processed only in the RLC layer of the master base station or only in the RLC layer of the secondary base station for the specific data. The RLC classification information may be included in, for example, an RLC-config information element of RRC signaling.

Although S1410 is illustrated as being performed after S1400 in FIG. 14, this is merely an example, and S1410 may be performed before S1400 or may be simultaneously performed.

The master base station transmits the generated RLC PDU to the terminal (S1420). The master base station transmits the generated RLC PDU to the terminal through a lower layer.

The master base station transmits the generated RLC classification information to the terminal (S1430). When the RLC classification information is in the form of the above-described RLC header, the RLC classification information may be transmitted (or included) with the RLC PDU in the S1420 procedure. When the RLC classification information is transmitted through the above-described RRC signaling, the RLC classification information may be transmitted to the terminal separately from the RLC PDU.

Although S1430 is shown as being performed after S1420 in FIG. 14, this is only an example, and S1430 may be performed before S1420 or may be simultaneously performed.

15 is a flowchart illustrating a method of controlling an RLC layer by a secondary base station according to the present invention. In FIG. 15, the master base station and the secondary base station support dual connectivity for the terminal. In FIG. 15, it is assumed that a master base station and a secondary base station have bearer splitting configured for data transmission and reception for one RB.

Referring to FIG. 15, the secondary base station generates an RLC PDU in the RLC layer (S1500). The secondary base station may receive a PDCP PDU from the PDCP layer of the master base station (RLC sub-entity form) in the RLC layer, perform a processing procedure such as partitioning or concatenation based on this, and generate an RLC PDU by attaching an RLC header. Alternatively, the secondary base station receives an RLC PDU (or RLC SDU) from the RLC layer of the master base station in the RLC layer (master-slave RLC type), and performs a processing procedure in the RLC layer based on the header and attaches the header at the secondary base station. RLC PDU may be generated.

The secondary base station generates RLC classification information indicating that the RLC PDU is processed in the RLC layer of the secondary base station (S1510). That is, the RLC classification information indicates that the RLC PDU is processed in the RLC layer of the secondary base station in a bearer split environment. The RLC classification information may be called second RLC classification information.

For example, the RLC classification information may be a newly added RLC header. For example, the RLC header may include a structure and a field as shown in FIG. 11 described above. Specifically, for example, the RLC header may include an M / S field indicating whether the corresponding RLC PDU is processed in the master RLC or the slave RLC. The RLC header may further include an SPI field indicating a processing method when the corresponding RLC PDU is processed in the slave RLC. The RLC header may further include an SN field indicating a sequence number of the RLC PDU and an SO field indicating a position of the AMD PDU segment in bytes when the RLC PDU is an AMD PDU. Meanwhile, when the value of the SPI field indicates concatenation, the SN field is interpreted to mean the number of corresponding concatenated RLC PDUs or segments, and the SO field is interpreted as indicating the length of data of the concatenated RLC PDU. May be

As another example, the RLC classification information may be at least one of the first three bits of the RLC header of the UMD PDU when the RLC PDU is a UMD PDU having a 10-bit length SN. For example, as described above with reference to FIGS. 12 and 13, at least one of the first three bits of the RLC header of the UMD PDU is processed in the RLC layer of the secondary base station whether the corresponding UMD PDU is processed in the RLC layer of the master base station. It may include an SEI indicating whether or not.

As another example, the RLC classification information may be transmitted to the terminal through RRC signaling. For example, the RLC classification information may indicate that an RLC PDU of a specific SN is processed in an RLC layer of the secondary base station. Specifically, for example, the RLC classification information may indicate that RLC PDUs of odd or even SNs are processed in the RLC layer of the secondary base station. Alternatively, the RLC classification information may indicate that all of the RLC PDUs are processed only at the RLC layer of the secondary base station or only at the RLC layer of the master base station for the specific data. The RLC classification information may be included in, for example, an RLC-config information element of RRC signaling.

Although FIG. 15 illustrates that S1510 is performed after S1500, this is merely an example, and S1510 may be performed before S1500 or may be performed simultaneously.

The secondary base station transmits the generated RLC PDU to the terminal (S1520). The secondary base station transmits the generated RLC PDU to the terminal through the lower layer.

The secondary base station transmits the generated RLC classification information to the terminal (S1530). When the RLC classification information is in the form of the aforementioned RLC header, the RLC classification information may be transmitted together with (or included in) the RLC PDU in the S1520 procedure. When the RLC classification information is transmitted through the above-described RRC signaling, the RLC classification information may be transmitted to the terminal separately from the RLC PDU.

Although FIG. 15 shows that S1530 is performed after S1520, this is only an example, and S1530 may be performed before S1520 or may be performed simultaneously.

16 is a flowchart illustrating a method of controlling an RLC layer by a terminal according to the present invention. In FIG. 16, the master base station and the secondary base station support dual connectivity for the terminal. In FIG. 16, it is assumed that a terminal is configured with bearer splitting for data transmission and reception for one RB through a master base station and a secondary base station.

Referring to FIG. 16, the UE receives at least one of a first RLC PDU processed in the RLC layer of the master base station and a second RLC PDU processed in the RLC layer of the secondary base station for one RB (S1600).

The terminal includes at least one of first RLC classification information indicating that the first RLC PDU is processed in the RLC layer of the master base station and second RLC classification information indicating that the second RLC PDU is processed in the RLC layer of the secondary base station. It is obtained (S1610).

For example, the first RLC classification information and the second RLC classification information may be an RLC header of a first RLC PDU and an RLC header of a second RLC PDU. For example, each of the RLC header of the first RLC PDU and the RLC header of the second RLC PDU may include a structure and a field as illustrated in FIG. 11 described above. Specifically, for example, each of the RLC header of the first RLC PDU and the RLC header of the second RLC PDU includes an M / S field indicating whether the corresponding RLC PDU is processed in the master RLC or the slave RLC. can do. The RLC header of the first RLC PDU and the RLC header of the second RLC PDU may include an SN field indicating a sequence number of the corresponding RLC PDU and a location of the AMD PDU segment in bytes when the corresponding RLC PDU is an AMD PDU. It may further include an SO field indicating. The RLC header of the second RLC PDU may further include an SPI field indicating a processing method of the second RLC PDU processed by the slave RLC. Meanwhile, when the value of the SPI field indicates concatenation, the RLC header of the second RLC PDU is interpreted to mean the number of concatenated RLC PDUs or segments, and the SO field corresponds to the concatenated RLC. It can be interpreted as indicating the length of the data of the PDU.

As another example, when each of the first RLC PDU and the second RLC PDU is a UMD PDU having a 10-bit length SN, among the first three bits of the RLC header of the UMD PDU as described above with reference to FIGS. 12 and 13. At least one may include an SEI indicating whether the corresponding UMD PDU is processed in the RLC layer of the master base station or in the RLC layer of the secondary base station. The first RLC classification information and the second RLC classification information may be the respective SEIs.

As another example, the first RLC classification information and the second RLC classification information may be transmitted to the terminal through RRC signaling. For example, the first RLC classification information and the second RLC classification information may indicate that an RLC PDU of a specific SN is processed in an RLC layer of a master base station, and an RLC PDU of another specific SN is processed in an RLC layer of a secondary base station. Can be. Specifically, for example, in the first RLC classification information and the second RLC classification information, RLC PDUs of odd or even SNs are processed in the RLC layer of the master base station, and RLC PDUs of the remaining SNs are processed in the RLC layer of the secondary base station. Can be indicated. Alternatively, the first RLC classification information and the second RLC classification information may indicate that, for specific data, all RLC PDUs are processed only at the RLC layer of the master base station or only at the RLC layer of the secondary base station. In this case, the first RLC classification information and the second RLC classification information may be expressed in one form of information. The first and second RLC classification information may be included in, for example, an RLC-config information element of RRC signaling.

Although FIG. 16 illustrates that S1610 is performed after S1600, this is only an example, and S1610 may be performed before S1600 or simultaneously.

The terminal recognizes that the first RLC PDU has been processed in the RLC layer of the master base station based on at least one of the received first RLC classification information and the second RLC classification information, and the second RLC PDU is determined. In operation S1620, it is recognized that the RLC layer of the secondary base station has been processed. The UE may recognize which RLC PDU is received from which base station for one RB in a bearer split environment, and may perform RLC control for downlink and uplink data transmission and reception based on this.

17 is a block diagram illustrating a master base station, a secondary base station, and a terminal for RLC layer control in a wireless communication system supporting dual connectivity according to an embodiment of the present invention. FIG. 17 illustrates a case in which a terminal has dual connectivity with a master base station and a secondary base station, and transmits and receives a service in a bearer split environment for one RB.

Referring to FIG. 17, the terminal 1700 according to the embodiment of the present invention may configure dual connectivity with the master base station 1730 and the secondary base station 1760. In addition, the terminal 1700 may transmit and receive data to and from the master base station 1730 and the secondary base station 1760 in a bearer split environment for one RB in the dual connection configuration.

The terminal 1700 includes a terminal receiver 1705, a terminal transmitter 1710, and a terminal processor 1720. The terminal processor 1720 performs functions and controls necessary to implement the above-described features of the present invention.

The terminal receiver 1705 may receive data from the master base station 1730 and the secondary base station 1760.

The terminal receiver 1705 receives a first RLC PDU from the master base station 1730 and first RLC classification information indicating that the first RLC PDU has been processed in the RLC layer of the master base station 1730.

In addition, the terminal receiver 1705 receives a second RLC PDU from the secondary base station 1760 and second RLC classification information indicating that the second RLC PDU has been processed in the RLC layer of the secondary base station 1760.

The first RLC classification information and the second RLC classification information may be in the form of a new RLC header, or some field of the existing RLC header may be changed. In this case, the first RLC classification information may be included in the first RLC PDU, and the second RLC classification information may be included in the second RLC PDU. The RLC header may have, for example, the structure and function described above with reference to FIG. 11. Specifically, for example, the RLC header may include an M / S field indicating whether the corresponding RLC PDU is processed in the master RLC or the slave RLC. Alternatively, the RLC header may be an RLC header of a UMD PDU having a 10-bit length SN as described above with reference to FIGS. 12 and 13. In this case, for example, at least one of the first three bits of the RLC header may be an SEI indicating whether the corresponding UMD PDU is processed in the RLC layer of the master base station 1730 or the RLC layer of the secondary base station 1760. .

Alternatively, the first RLC classification information and the second RLC classification information may be included in RRC signaling. In this case, the first RLC classification information and the second RLC classification information may be received separately from the first RLC PDU and the second RLC PDU. In this case, the first RLC classification information and the second RLC classification information may be configured in one form of information (eg, one message and / or one information field). For example, the first RLC classification information and the second RLC classification information are RLC PDUs of a specific SN are processed in the RLC layer of the master base station 1730, and RLC PDUs of other specific SNs are RLC of the secondary base station 1760. It may indicate that processing in the layer. Alternatively, the first RLC classification information and the second RLC classification information may indicate that, for specific data, all RLC PDUs are processed only at the RLC layer of the master base station 1730 or only at the RLC layer of the secondary base station 1760. . The first and second RLC classification information may be included in, for example, an RLC-config information element of RRC signaling.

The terminal processor 1720 recognizes that the first RLC PDU has been processed in the RLC layer of the master base station 1730 based on at least one of the first RLC classification information and the second RLC classification information, and the second RLC. It is recognized that a PDU has been processed at the RLC layer of the secondary base station 1760. Based on this, the terminal processor 1720 generates control information on at least one RLC layer at the terminal 1700, and in a bearer splitting environment between the terminal 1700, the master base station 1730, and the secondary base station 1760. Control data transmission and reception.

The terminal transmitter 1710 performs uplink data transmission in a bearer split environment based on the control information on the RLC layer.

The master base station 1730 includes a master transmitter 1735, a master receiver 1740, and a master processor 1750. The master processor 1750 performs the functions and controls necessary to implement the features of the present invention as described above.

The master processor 1750 generates a first RLC PDU at the RLC layer of the master base station 1730. In addition, the master processor 1750 generates the first RLC classification information indicating that the first RLC PDU has been processed in the RLC layer of the master base station 1730. The first RLC identification information may be in the form of a new RLC header or may be a form in which some fields of the existing RLC header are changed. Alternatively, the first RLC classification information may be included in RRC signaling.

The master transmitter 1735 transmits the generated first RLC PDU and the first RLC classification information to the terminal 1700. If the first RLC classification information is a form in which the new RLC header form or some field of the existing RLC header is changed, the first RLC classification information may be included in the first RLC PDU and transmitted to the UE 1700. have.

In addition, the master transmitter 1735 may transmit the PDCP PDU generated in the PDCP layer to the secondary base station (RLC sub-entity type). Alternatively, the master transmitter 1735 may transmit the RLC PDU (or RLC SDU) generated in the RLC layer to the secondary base station (master-slave RLC type).

The master receiver 1740 may receive uplink data for the master base station 1730 in the bearer split environment from the terminal 1700.

The secondary base station 1760 includes a secondary transmitter 1765, a secondary receiver 1770, and a secondary processor 1780. The secondary processor 1780 performs the functions and controls necessary to implement the features of the present invention as described above.

The secondary processor 1780 generates a second RLC PDU at the RLC layer of the secondary base station 1760.

The secondary receiver 1770 may receive a PDCP PDU from the master base station 1730 (RLC sub-entity form). In this case, the secondary processor 1780 may perform a processing procedure such as division or concatenation based on the PDCP PDU and attach a RLC header to generate a second RLC PDU. Alternatively, the secondary receiver 1770 may receive an RLC PDU (or RLC SDU) from the master base station 1730 (master-slave RLC type). In this case, the secondary processor 1780 may perform a processing procedure in the RLC layer based on the RLC PDU (or RLC SDU) and attach a header to generate a second RLC PDU in the secondary base station.

In addition, the secondary processor 1780 generates the second RLC classification information indicating that the second RLC PDU has been processed in the RLC layer of the secondary base station 1730. The second RLC identification information may be in the form of a new RLC header or may be a form in which some fields of the existing RLC header are changed. Alternatively, the second RLC classification information may be included in RRC signaling.

The secondary transmitter 1765 transmits the generated second RLC PDU and the second RLC classification information to the terminal 1700. If the second RLC classification information is a form in which the new RLC header form or some field of the existing RLC header is changed, the second RLC classification information may be included in the second RLC PDU and transmitted to the terminal 1700. have.

The secondary receiver 1770 may receive uplink data for the secondary base station 1760 from the terminal 1700 in a bearer split environment.

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

Claims (20)

Data of a radio link control (RLC) layer by the master base station in a network system supporting dual connectivity between a master eNB and a secondary eNB for a UE In the management method, Generating RLC classification information indicating that an RLC packet data unit (PDU) processed in an RLC layer is processed in the RLC layer of the master base station; And And transmitting the RLC classification information to the terminal. The method of claim 1, The master base station configures a bearer split for transmitting and receiving data for one RB (Radio Bearer) for the secondary base station and the terminal. The method of claim 1, The RLC classification information includes an RLC header, The RLC header may include a M (Master) / S (Slave) field indicating whether the corresponding RLC PDU is processed in the master RLC or the slave RLC. The master base station and the secondary base station configure a secondary-slave RLC format, the master RLC is an RLC layer of the master base station, and the slave RLC is an RLC layer of the secondary base station. The method of claim 1, The RLC PDU is a UMD PDU (Unacknowledged Mode Data PDU) having a 10-bit sequence number (SN), and at least one of the first three bits of the RLC header of the UMD PDU is processed by the corresponding UMD PDU in the RLC layer of the master base station. Sub-Entity Indicator (SEI) indicating whether or not to be processed in the RLC layer of the secondary base station, And the RLC classification information is the sub entity indicator. The method of claim 1, The RLC classification information is transmitted to the terminal through RRC signaling. The method of claim 5, The RLC classification information transmitted to the terminal through the RRC signaling indicates that the RLC PDU of a specific SN is processed in an RLC layer of the master base station. In a data management method in a radio link control (RLC) layer by a secondary base station in a network system supporting dual connectivity of a master base station and a secondary base station for a terminal, Generating RLC classification information indicating that an RLC packet data unit (PDU) processed in an RLC layer is processed in an RLC layer of the secondary base station; And And transmitting the RLC classification information to the terminal. The method of claim 7, wherein The master base station and the secondary base station, characterized in that for configuring the bearer split for data transmission and reception for one RB, the terminal. The method of claim 7, wherein The RLC classification information includes an RLC header, The RLC header may include an M / S field indicating whether the corresponding RLC PDU is processed in the master RLC or the slave RLC. And the master base station and the secondary base station configure a secondary-slave RLC format, wherein the master RLC is an RLC layer of the master base station, and the slave RLC is an RLC layer of the secondary base station. The method of claim 9, The RLC header further includes a SPI (Slave Processing Indicator) field indicating a processing method when a corresponding RLC PDU is processed in a slave RLC. The method of claim 10, The RLC header further includes an SN field indicating a sequence number of the RLC PDU, and a SO (Segment Offset) field indicating a position of the AMD PDU segment in bytes when the RLC PDU is an AMD Acknowledged Mode Data PDU (AMD PDU). Including, When the value of the SPI field indicates concatenation, the SN field is interpreted to mean the number of concatenated RLC PDUs or segments, and the SO field indicates the length of data of the concatenated RLC PDU. Characterized in that it is interpreted. The method of claim 7, wherein The RLC PDU is a UMD PDU (Unacknowledged Mode Data PDU) having a 10-bit length SN, and at least one of the first three bits of the RLC header of the UMD PDU is whether the corresponding UMD PDU is processed in the RLC layer of the master base station. Sub-Entity Indicator (SEI) indicating whether to be processed in the RLC layer of, And the RLC classification information is the sub entity indicator. The method of claim 7, wherein The RLC classification information is transmitted to the terminal through RRC signaling. The method of claim 13, The RLC classification information transmitted to the terminal through the RRC signaling indicates that the RLC PDU of a specific SN is processed in the RLC layer of the secondary base station. A data management method of a radio link control (RLC) layer by a terminal in a network system supporting dual connection between a master base station and a secondary base station for a terminal, Receiving at least one of a first RLC PDU (Packet Data Unit) processed in an RLC layer of the master base station and a second RLC PDU processed in an RLC layer of the secondary base station; the first RLC PDU of the master base station; Obtaining at least one of first RLC classification information indicating processing at an RLC layer and second RLC classification information indicating that the second RLC PDU is processed at an RLC layer of the secondary base station; And The first RLC PDU recognizes that the first RLC PDU has been processed at the RLC layer of the master base station based on first RLC classification information, and the second RLC PDU is based on the second RLC classification information. And recognizing that it has been processed at the RLC layer of a secondary base station. The method of claim 15, The first RLC PDU and the second RLC PDU are characterized in that based on bearer split (bearer split) for one RB (Radio Bearer). The method of claim 15, The first RLC classification information and the second RLC classification information each include an RLC header of a first RLC PDU and an RLC header of a second RLC PDU. Each of the RLC header of the first RLC PDU and the RLC header of the second RLC PDU includes an M / S field indicating whether the corresponding RLC PDU is processed in the master RLC or the slave RLC. The master base station and the secondary base station configure a secondary-slave RLC format, the master RLC is an RLC layer of the master base station, and the slave RLC is an RLC layer of the secondary base station. The method of claim 17, The RLC header of the second RLC PDU further includes a SPI (Slave Processing Indicator) field indicating a processing method of the second RLC PDU processed by the slave RLC. The method of claim 18, Each of the RLC header of the first RLC PDU and the RLC header of the second RLC PDU may include an SN field indicating a sequence number of the corresponding RLC PDU and a byte unit when the corresponding RLC PDU is an AMD Acknowledged Mode Data PDU (AMD PDU). Further comprising a SO (Segment Offset) field indicating the location of the PDU segment, If the value of the SPI field indicates concatenation, the RLC header of the second RLC PDU is interpreted as meaning the number of the concatenated RLC PDUs or segments, and the SO field is concatenated. A data management method, characterized in that it is interpreted to indicate the length of data of the RLC PDU. The method of claim 15, Each of the first RLC PDU and the second RLC PDU is a UMD PDU (Unacknowledged Mode Data PDU) having a 10-bit length SN, and at least one of the first three bits of the RLC header of each UMD PDU is mastered by the corresponding UMD PDU. A sub-entity indicator (SEI) indicating whether it is processed in the RLC layer of the base station or in the RLC layer of the secondary base station, And the first RLC classification information and the second RLC classification information are the sub-entity indicators.

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