KR20150007593A - Method and apparatus for data management of radio resource control layer in wireless communication system - Google Patents

Abstract

Provided are a method and an apparatus for data management of a radio link control layer in a wireless communication system. According to the present invention, the method comprises: determining, by an MAC layer, the size of a transport block to be allocated to each sub-frame; determining flow control request information which is reported to a PDCP layer having dual connectivity in a master base station based on the size of the transport block and data amount information which the MAC layer requests to an RLC layer; and transferring the flow control request information to the master base station. The flow control request information includes information on the amount of data transmitted through the base station among the total amount of data to be transmitted through a radio bearer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for managing data in a wireless connection control layer in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to information transmission for operating data in a wireless connection control layer for terminals connected to a plurality of base stations.

A terminal may perform wireless communication through one or more base stations of the base stations constituting at least one serving cell. This is called dual connectivity. In other words, a dual connection may be referred to as an operation in which a terminal consumes radio resources provided by at least two or more different network points. Here, at least two or more different network points may be physically or logically divided into a plurality of base stations, one of which is referred to as a master eNB and the other as a secondary eNB. The master base station and the secondary base station are connected as a backhaul during the RRC connected mode (RRC connected).

At this time, the master base station controls data flow or security according to a Packet Data Convergence Protocol (PDCP) for data transmitted to a secondary base station through a radio bearer (RB). Also, in the dual connection, the master base station is a base station that can configure the S1-MME interface with the MME. Accordingly, the master base station can terminate at least the S1-MME and serve as a mobility anchor for the core network.

A Radio Link Control (RLC) layer in the RB is configured in the form of a sub-entity for each eNB or an entity for multiple base stations . 1) A sub-entity for each base station is a sub-entity defined in the RLC layer in the RB served by a plurality of base stations. And the RLC layer can be used independently in each base station. Here, the sub-entity is not limited to being referred to as an entity sub-structure and can be treated as an entity. 2) An entity for a plurality of base stations is a single entity existing in an RB served by a plurality of base stations. A master RLC layer is located in the master base station and a slave RLC layer is located in the secondary base station. 3) For the RLC layer in a single RB served by a plurality of base stations, a master RLC layer may be defined in the master base station and a slave RLC layer may be defined in the secondary base station. At this time, a basic RLC function is implemented in the master RLC, and a segmentation / concatenation function in the slave RLC layer is implemented only for the downlink transmission data.

The secondary base station transmits data received from the PDCP layer or the master RLC layer in the single RB of the master base station to the terminal through the RLC layer or transmits the data to the terminal through the slave RLC layer, MAC layer, and PHY layer. At this time, the data in the single RB is distributed according to the radio resource amount or the transmission rate allocated to the corresponding terminal for each of a plurality of base stations defined in the RB.

According to the present invention, in order to support data flow control for distributing data in a single RB among base stations, a MAC layer and a layer responsible for flow control, for example, RLC / PDCP layer It is required that the information for data operation be exchanged between them.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method and a system for controlling a master cell of a master cell in a service area of a master cell, While supporting additional data services over the secondary cell while maintaining wireless connectivity and data services.

Another aspect of the present invention is to provide a data operation method and apparatus for a wireless connection control layer for a dual-connected terminal.

Another aspect of the present invention is to provide a method and apparatus for transmitting data for data operation of a wireless connection control layer for a dual-connected terminal.

Another aspect of the present invention is to provide a data flow control method and apparatus for distributing data in the radio bearer by configuring a bearer split for a plurality of base stations by a radio bearer.

According to an aspect of the present invention, there is provided a method of operating a base station in a wireless communication system, the method comprising: determining a size of a transport block to be allocated to each subframe in a MAC layer; Determining flow control request information to be reported to the PDCP layer of the dual-connected master base station based on the amount of data requested to the RLC layer in the master base station, and transmitting the flow control request information to the master base station.

According to another aspect of the present invention, in a wireless communication system, a base station operating data for a dual-connected terminal determines a size of a transport block to be allocated to each subframe in the MAC layer, And a control unit for determining flow control request information to be reported to the PDCP layer of the dual connected master base station based on the amount of data requested from the MAC layer to the RLC layer and a control unit for transmitting the flow control request information to the master base station And the flow control request information includes information on the amount of data to be transmitted through the base station among the total amount of data to be transmitted through the radio bearer.

According to the present invention, information for controlling data flow in a bearer split structure can be exchanged between a plurality of base stations, thereby supporting a dual connected terminal.

1 shows a wireless communication system to which the present invention is applied.
2 is a block diagram illustrating a wireless protocol structure for a user plane.
3 is a block diagram illustrating a wireless protocol structure for a control plane.
4 is a diagram showing an outline of an example of an RLC sublayer model to which the present invention is applied.
FIG. 5 shows an example of a dual connection situation of a terminal applied to the present invention.
6 to 8 show an example of a case where the terminal establishes a dual connection with the secondary base station and the master base station.
FIG. 9 is a flowchart illustrating an example of a method of operating data of a radio access control layer according to the present invention.
FIG. 10 is a block diagram showing an example of a device for operating data of a radio link control layer 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 E-UMTS system (Evolved-Universal Mobile Telecommunications System). The E-UMTS system may be an Evolved-UMTS Terrestrial Radio Access (E-UTRA) or a Long Term Evolution (LTE) or an LTE-A (advanced) system. The wireless communication system can be classified into a Code Division Multiple Access (CDMA), a Time Division Multiple Access (TDMA), a Frequency Division Multiple Access (FDMA), an Orthogonal Frequency Division Multiple Access (OFDMA), a Single Carrier- , OFDM-TDMA, and OFDM-CDMA.

1, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) includes a base station (UE) 10 providing a control plane (CP) and a user plane (UP) (Evolved NodeB: eNB).

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 a base station (BS), a base transceiver system (BTS), an access point, a femto-eNB, , A pico-eNB, a home eNB, a relay, and the like. The base stations 20 are physically connected through an optical cable or a digital subscriber line (DSL), and can exchange signals or messages with each other through the X2 interface. In the following, the description of the physical connection is omitted and the description of the logical connection is omitted. As described above, the base station 20 communicates with the S-GW (Serving Gateway) through the MME (Mobility Management Entity) and the S1-U through the S1-MME through the EPC (Evolved Packet Core) do. The S1-MME interface exchanges context information of the terminal 10 with information for supporting the mobility of the terminal 10 by exchanging signals with the MME. And sends and receives data to be served to the S-GW and 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 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), and the traffic flow from the wireless link connecting the terminal 10 to the base station 20 to the PDN connecting to the service entity can be referred to as IP (Internet Protocol).

A wireless interface between a terminal and a base station is called a " Uu interface ". The layers of the radio interface protocol between the UE and the network are divided into a first layer L1 and a second layer L2 defined in a 3rd Generation Partnership Project (3GPP) series communication system (UMTS, LTE, LTE- ), And a third layer (L3). Among them, 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 at the third layer exchanges RRC messages, And the network.

FIG. 2 is a block diagram illustrating a radio protocol architecture for a user plane, and FIG. 3 is a block diagram illustrating a radio 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 a transport channel. The transmission channel is classified according to how data is transmitted through the air interface.

Also, data is transferred over the physical channel between different physical layers (i. E., Between the physical layer of the transmitter and the receiver). The physical channel can be modulated by an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and uses time, frequency, and space generated by a plurality of antennas as radio resources.

For example, a physical downlink control channel (PDCCH) of a physical channel notifies a UE of resource allocation of a paging channel (P-SCH), a downlink shared channel (DL-SCH), hybrid automatic repeat request (HARQ) The PDCCH may carry an uplink scheduling grant informing the UE of the resource allocation of the uplink transmission. Also, 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, PHICH (Physical Hybrid ARQ Indicator Channel) carries HARQ ACK / NAK signal in response to uplink transmission. Also, a physical uplink control channel (PUCCH) carries uplink control information such as HARQ ACK / NAK, scheduling request and CQI for downlink transmission. Also, a physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH). The PUSCH may include CSI (channel state information) information, such as HARQ ACK / NACK and CQI, if necessary, according to the setup and request of the base station.

The MAC layer can perform multiplexing or demultiplexing into a transport block provided on a physical channel on a transport channel of a MAC SDU (service data unit) belonging to a logical channel and a mapping between a logical channel and a transport channel. The MAC layer provides service to the 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.

For example, services provided from the MAC layer to the upper layer include data transfer or radio resource allocation.

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).

Unconfirmed mode generally configures real-time data transmission, such as data streaming or Voice over Internet Protocol (VoIP), and is a mode that focuses on speed rather than reliability of data. On the other hand, the acknowledged mode is a mode that focuses on the reliability of data and is suitable for data transmission which is less sensitive to large data transmission or transmission delay. The BS determines the mode of the RLC in the RB corresponding to each EPS bearer based on Quality of Service (QoS) information of each EPS bearer connected to the UE, and configures parameters in the RLC to satisfy the QoS.

RLC SDUs are supported in various sizes, and may be supported on a byte basis, for example. RLC protocol data units (RLC PDUs) are defined only when a transmission opportunity is notified from a lower layer (e.g., the MAC layer), and when the transmission opportunity is notified, the RLC PDUs are delivered to a lower layer. The transmission opportunity may be notified 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. The RLC layer will be described in detail with reference to FIG.

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 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 (Non-Access Stratum) message in the control plane, and the DRB is used as a path for transmitting the user data in the user plane.

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 OFDM 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.

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

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

The UM RLC entity 400 may be configured to receive or transmit RLC PDUs over logical channels (e.g., DL / UL DTCH, MCCH, or MTCH). The UM RLC entity may also carry or receive a UMD PDU (Unacknowledged Mode Data PDU).

A UM RLC entity is composed of a transmitting UM RLC entity or a receiving UM RLC entity.

The transmitting UM RLC entity receives the RLC SDUs from the upper layer and transmits the RLC PDUs to the peer receiving UM RLC entity through the lower layer. When a transmitting UM RLC entity configures UMD PDUs from RLC SDUs, when a specific transmission opportunity is notified by a lower layer, RLC SDUs are segmented or concatenated to determine the total size of RLC PDUs indicated by the lower layer UMD PDUs are configured to be within the UMD PDU, and the relevant 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 UMD PDUs, the receiving UM RLC entity detects whether the UMD PDUs are received in duplicate, discards the duplicated UMD PDUs, and if the UMD PDUs are received out of sequence Reordering the order of the UMD PDUs, detecting the loss of UMD PDUs in the lower layer to avoid excessive rearrangement delays, reassembling the RLC SDUs from the rearranged UMD PDUs , Delivers the reassembled RLC SDUs to an upper layer in an ascending order of an RLC SN (sequence number), and transmits a UMD PDU that can not be reassembled into an RLC SDU due to a UMD PDU loss belonging to a specific RLC SDU in a lower layer Can be discarded. Upon RLC re-establishment, the receiving UM RLC entity reassembles the RLC SDUs from the received UMD PDUs out of sequence, if possible, and passes them to the upper layer, and the remaining UMD PDUs that could not be reassembled into RLC SDUs Discard all, initialize the associated state variables and stop the associated timers.

Meanwhile, the AM RLC entity 440 may be configured to receive or transmit RLC PDUs on a logical channel (e.g., DL / UL DCCH or DL / UL DTCH). The AM RLC entity transmits or receives an AMD PDU or an ADM PDU segment and forwards or receives an RLC control PDU (e.g., a STATUS PDU).

The AM RLC entity 440 forwards the STATUS PDUs to the peer AM RLC entity to provide positive and / or negative acknowledgment (ACK) information for the RLC PDUs (or portions thereof). This can be called STATUS reporting. A polling procedure from the peer AM RLC entity may be followed to trigger STATUS reporting. That is, the AM RLC entity may poll the peer AM RLC entity to trigger a STATUS report at the corresponding peer AM RLC entity.

If STATUS reporting is triggered and the blocking timer (t-StatusProhibit) is not running or has expired, the STATUS PDU is sent on the next transmission opportunity. Therefore, the UE estimates the size of the STATUS PDU and considers the STATUS PDU as data available for transmission in the RLC layer.

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 transmits the RLC PDUs to the peer AM RLC entity through the lower layer. The transmitter of the AM RLC entity 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 noticed by the lower layer, when constructing AMD PDUs from the RLC SDUs and construct concatenated AMD PDUs. The transmitter of the AM RLC entity supports retransmission (ARQ) 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 notified by the lower layer, the AM RLC entity transmits the RLC data PDUs as AMD PDU segments Re-segment.

At this time, the number of re-segmentations is not limited. When the transmitter of the AM RLC entity creates AMD PDUs from RLC SDUs received from the upper layer or creates 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 through the lower layer.

When receiving the RLC data PDUs, the receiver of the AM RLC entity detects whether the RLC data PDUs are received in duplicate, discards the duplicated RLC data PDUs, and discards the RLC data PDUs out of sequence Reorder the order of the RLC data PDUs, detect loss of RLC data PDUs occurring in the lower layer, request retransmission to the peer AM RLC entity, and reassemble the RLC SDUs from the rearranged RLC data PDUs reassembles the reassembled RLC SDUs and delivers the reassembled RLC SDUs to the upper layer in the reassembled sequence.

At the time of RLC resetting, the receiver of the AM RLC entity reassembles the RLC SDUs from the received RLC data PDUs out of the sequence if possible, transfers the RLC SDUs to the upper layer, and removes all remaining RLC data PDUs that can not be reassembled into RLC SDUs Discard related events, initialize related state variables and stop associated timers.

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

The transfer of upper layer PDUs ARQ (error correction through ARQ), only for AM data transmission (only for AM data transfer); Concatenation, segmentation and reassembly of RLC SDUs, only for UM and AM data transfer (only for UM and AM data transfer). Re-segmentation of RLC data PDUs. Only for AM data transmission. Reordering of RLC data PDUs. Only for UM and AM data transfer. Duplicate detection. Only for UM and AM data transfer. RLC SDU discard (RLC SDU discard). Only for UM and AM data transfer. RLC re-establishment (RLC re-establishment) Protocol error detection. Only for AM data transmission.

Meanwhile, one of a plurality of physical or logical base stations is defined as a master base station (also referred to as a central base station, an anchor base station, or a serving base station) and a remaining one (or more) (Also referred to as a small base station, an assisting base station, or a non-serving base station). For example, the macro base station may be the master base station, and the small base station may be the secondary base station.

FIG. 5 shows an example of a dual connection situation of a terminal applied to the present invention.

5, a case where a terminal 550 located in a service area of a master cell in a master base station 500 enters an over-laid area overlapped with a service area of a secondary cell in the secondary base station 510 .

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

Accordingly, the user data arriving at the master cell can be delivered to the terminal through the secondary cell. Specifically, the F2 frequency band is allocated to the master base station, and the F1 frequency band is allocated to the secondary base station. The terminal can receive the service from the master base station through the frequency band F2 and receive the service from the secondary base station through the frequency band F1. In the above example, the master base station uses F2 and the secondary base station uses F1 frequency band. However, the present invention is not limited to this, and both the master base station and the secondary base station may use the same frequency band F1 or F2.

6 to 8 show an example of a case where the terminal establishes a dual connection with the secondary base station and the master base station. In particular, FIGS. 7 and 8 are bearer split cases serving through the master base station and the secondary base station in a single RB. The bearer split can be referred to as multi-flow, multiple node (eNB) transmission, inter-eNB carrier aggregation, and the like. Of course, the present invention does not exclude the case where the present invention is not a bearer split.

6, the master base station includes the PDCP, RLC, MAC, and PHY layers, and the secondary base station includes the 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. In this case, the Xn interface protocol may be an X2 interface protocol defined between base stations in the LTE system. There are only two PDCP layers in the master base station, and each PDCP layer is connected to a different RLC layer. In particular, the PDCP layer of the master base station and the RLC layer of the secondary base station are connected to "# 2 RB (second RB) ".

The example of FIG. 6 is also referred to as an independent RLC type or a single RLC entity type.

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

The PDCP layer of the master base station is connected to the RLC layer of the secondary base station using the Xn interface protocol. At this time, 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 is referred to as a # 1 sub-entity (first sub-entity) and the RLC layer of the secondary base station is referred to as a # 2 sub-entity (second sub-entity). Here, the sub-entity is divided into a one-to-one matching of transmission and reception. The sub-entity may be referred to as an entity. The RLC layer exists in a duplicate form. Each sub-entity is independent but there are two sub-entities (# 1 sub-entity and # 2 sub-entity) in one RB (i.e., # 1 RB).

In this case, the RLC parameters must be separately configured for the RLC-AM # 1 sub-entity and the RLC-AM # 2 sub-entity, respectively. Because the delay times that occur when data to be served through each RLC-AM sub-entity are transmitted to the UE may differ from each other, the timer values to be set in consideration of the delay time for each of the sub- Because they can be different from each other. If the delay time of the data transmitted through each of the sub-entities is the same, the values of the timers to be set for each of the sub-entities may be the same. This may be determined at the master base station and may be determined at the secondary base station or at the network including the master base station and the secondary base station. Therefore, the data to be transmitted through the PDCP in the same RB can be transmitted through one sub-entity of the RLC-AM # 1 sub-entity or the RLC-AM # 2 sub-entity. Here, an identifier for distinguishing between which sub-entities the data is transmitted by the terminal receiving the data may be further transmitted.

The example of FIG. 7 is also referred to as a sub-entity RLC type in the split case. However, the example of FIG. 7 does not necessarily apply to the bearer split.

8, the master BS includes a PDCP, an RLC, a MAC, and a PHY layer, and a secondary BS includes an RLC, a MAC, and a PHY layer. The RLC layer of the master base station is connected to the RLC layer of the secondary base station using the Xn interface protocol.

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 (i.e., RB # 1). At this time, the RLC layer of the master base station is referred to as a master RLC layer, and the RLC layer of the secondary base station is referred to as a slave RLC layer.

In the case of downlink, further division of the AMD / UM PDU of the slave RLC layer of the UE is possible. The partitioning operation of the slave RLC includes operations of binding a plurality of RLC PDUs or grouping AMD PDU segments divided in the master RLC. Also, the AMD / UM PDU of the slave RLC layer of the base station can be concatenated.

In the case of the uplink, data received through the slave RLC layer is forwarded to the master RLC layer. If there is no data to be transmitted to the slave RLC layer, the transmission between the UE and the BS may be a single transmission instead of the TDM transmission.

The scheduling of the radio resources is mainly performed by the MAC scheduler, and the situation of the MAC layer of the master base station is different from that of the MAC layer of the secondary base station. The master RLC layer allocates (or splits, connects, or reassociates) a PDU based on the MAC layer of the master base station, and the slave RLC layer performs division or connection based on the MAC layer of the secondary base station.

In the uplink, only one RLC layer exists in the UE. In the downlink, since the MAC layer is divided into two or more different base stations and a difference of downlink radio conditions occurs between the base stations, the RLC layer divides or reassembles in different ways, while in the uplink, Since the slave RLC layer simply forwards the received data to the master RLC layer, the RLC layer that processes the uplink data is only the master RLC layer. Therefore, a dual-connected terminal includes only one RLC layer. Therefore, it is also possible to perform uplink transmission only to the master base station (also referred to as " single uplink ") in view of uplink data transmission (for example, PUSCH).

The example of FIG. 8 is also referred to as a master-slave RLC type in the split case. However, the example of FIG. 8 does not necessarily apply to the bearer split.

Meanwhile, a basic operation of the scheduler applied to the present invention will be described.

The MAC layer in the base station includes at least one dynamic resource scheduler, and the at least one dynamic resource scheduler allocates physical layer resources for DL-SCH and UL-SCH transport channels do.

When a plurality of terminals share resources, the scheduler considers the traffic volume and the QoS requirements of each terminal and associated RBs. The grant (per UE grant) for each terminal is used only to grant transmission right (right) on the UL-SCH. That is, there is no "per UE per RB" grant. This means that only the UL grant on a per-terminal basis exists. That is, there is no physical channel resource allocation scheme that allows UL transmission for a specific RB.

The scheduler may allocate resources in consideration of radio conditions of the terminal identified through measurements made at the base station or measurements reported by the terminal. The scheduler's radio resource allocation is valid in one or more Transmission Time Intervals (TTIs). The resource assignment consists of PRB (Physical Radio Bearer) and MCS (Modulation and Coding Scheme). In addition, an allocation for a time period longer than one TTI may require additional information (e.g., allocation time, allocation repetition factor).

Next, a bearer split applied to the present invention will be described.

Bearer split refers to a structure in which one RB is divided into two flows (or more flows) through a plurality of base stations and transmitted. A bearer split is also referred to as a multi-flow in that information is transmitted through a plurality of flows.

In the case of the bearer split, each base station may include a Packet Data Convergence Protocol (PDCP) layer, a MAC layer, and an RLC layer, but the layer responsible for the flow control is only one base station . If the layer responsible for the flow control is a PDCP layer, the PDCP layer is included only in the master base station.

The MAC layer of the base station in the existing LTE system transmits information on the amount of data to be transmitted to the RLC layer, transmission opportunity, and the like to the RLC layer. The RLC layer constructs an RLC PDU by dividing or combining RLC SDU data received from a PDCP layer located in the same base station based on information received from the MAC layer. Thereafter, the MAC layer receives the RLC PDUs configured in the RLC from the RLC layer in the form of MAC SDUs.

However, in the case of the bearer split, even if the secondary base station RLC layer processes the data according to the data amount requested by the secondary base station MAC layer and the transmission opportunity, information on the amount of data processed by the RLC layer, It is not possible to adaptively adjust the amount of data to be transmitted from the flow control layer to the secondary base station unless it is notified to the master base domestic flow control layer present in the master base. In addition, when the backhaul connection is not ideal, there is a problem that the RLC layer in the secondary base must be accompanied by a delay time when requesting the amount of data to be transmitted to the MAC layer and the transmission opportunity information to the flow control layer in the master base do.

Now, a data operation method and apparatus of a radio link control (RLB) layer in a wireless communication system according to the present invention will be described. A method and apparatus for transferring information between RBs corresponding to one-to-one correspondence with an EPS bearer (i.e., a master base station or a secondary base station) is proposed. In the following embodiments of the present invention, it is assumed that the functions performed in the flow control layer are performed in the PDCP layer or the master RLC layer. However, it does not preclude that the flow control layer can be configured in the master base station separately from the PDCP layer or the master RLC layer.

The secondary base station transfers the data received from the PDCP layer in the single RB of the master base station to the RLC layer (or transfers the data received from the master RLC layer to the slave RLC layer), and transmits the data to the terminal through the MAC layer and the PHY layer. At this time, the data in the single RB is operated to be distributed to the secondary base station and the master base station according to the radio resource amount or the transmission rate that each base station can allocate to the corresponding terminal.

In the present invention, information to be exchanged between a MAC layer and an RLC layer (or a PDCP layer) is defined to support data flow control for distribution of data in a single RB, a method for receiving the information from the MAC layer, We propose an operation method.

Hereinafter, the present invention describes a situation in which a terminal establishes dual connectivity with a secondary cell in a master cell in a master base station and a secondary cell in a secondary base station and configures an RRC (Radio Resource Control) to support the dual connection I suppose. In particular, although a bearer split configuration limited to a single RB is described as an example, the scope of the present invention is not limited thereto, and the present invention can be applied to a bearer split for a plurality of RBs.

At this time, in the case of a control plane (CP) (e.g., the generation and transmission of RRC signaling), a bearer split for a signaling radio bearer may be configured, wherein a user plane The defined bearer split scheme can be equally applied to SRBs defined in the control plane. That is, the configuration method may be the same.

In addition, the terminal according to the present invention may provide information to be distinguished for each RB (i.e., information about whether bearer split is applied or not used in each RB), a plurality of RBs (e.g., a logical channel group)). < / RTI > At this time, the configuration information for each RB is independent from each other. For example, when the first RB includes information (e.g., " MF on ") for configuring the bearer split, the information about the second RB transmitted concurrently with the information about the first RB may include RB flow re- RB flow reconfiguration information (e.g., " MF off ").

The RLC layer in the single RB according to the embodiment of FIG. 6 to FIG. 8 will be described with reference to two exemplary embodiments.

In the first embodiment, a case in which one entity is present in a plurality of base stations and a case in which a sub-entity for each eNB is present in each base station is defined as " Information is transmitted from the slave RLC layer to the master RLC layer, whereas in the second embodiment, the master-slave RLC case is transmitted from the slave RLC layer to the master RLC layer.

≪ First Embodiment: Case where there is one entity in a plurality of base stations and case where sub-entities exist in each base station >

FIG. 9 is a flowchart illustrating an example of a method of operating data of a radio access control layer according to the present invention.

Referring to FIG. 9, the secondary base station determines a " transport block size " to be allocated to each subframe in a MAC layer (hereinafter referred to as a MAC scheduler) (S910).

The MAC layer of the secondary base station (i.e., the MAC scheduler) determines the size of the transport block and the " amount of data information requested to the RLC layer (i.e., the RLC PDU indicated by the lower layer, Flow control request information " to be reported to the PDCP layer (i.e., the PDCP layer of the master base station) based on the " total size of the PDCP layer " The " data amount information " may be set based on a PBR that can be set for each logical channel. When the TB size allocable in this TTI is larger than the sum of the PBRs of all logical channels, The "amount of data information" requested by the layer may be different. Therefore, both parameters can be considered to determine the request information to be transmitted to the PDCP layer (or the layer responsible for flow control (i.e., the new layer in the master base station, not the PDCP layer)). Alternatively, only the size of the transport block or only the " amount of data information " requested by the RLC layer may be used.

The flow control request information may also be referred to as MAC request information as a MAC layer message.

The secondary base station transmits the flow control request information to the master base station (S930). For example, the flow control request information may be transmitted from the secondary base station to the master base station during the downlink transmission, and a signaling protocol configured for exchanging information between the base station and the X2 interface protocol may be used for transmission of the flow control request information. That is, information on the amount of data to be transmitted through the secondary base station among the total data amount to be transmitted through the RB is transmitted to the master base station.

At this time, the generation and transmission of the related information in the secondary base station means that information on the total size of the RLC PDUs indicated by the MAC layer when a specific transmission opportunity is notified to the RLC layer by the lower layer (e.g., MAC layer) Is reported by the MAC layer to the RLC layer when it is reported to the PDCP layer in real time (e.g., " immediately upon receipt of the flow control request information ") or by a lower layer Information on the total size of the RLC PDUs is periodically reported to the PDCP layer, or when a specific transmission opportunity is notified to the RLC layer by a lower layer (e.g., MAC layer) Information on the total size of the RLC PDUs indicated by the " information on the total size of the RLC PDUs " is periodically filtered through a predetermined filtering method (for example, IIR (infinite impulse response) Lt; RTI ID = 0.0 > PDCP < / RTI >

The following equation shows an example of the IRR filter method.

Here, t is the current time, alpha is the " size of transport block " or " data amount information " generated at that time, and throughput "to be.

In one embodiment (Embodiment 1-1), the flow control request information may include " total size of RLC PDUs indicated by a lower layer when a specific transmission opportunity is notified by a lower layer ". This is because RLC PDUs are defined only when a transmission opportunity is notified from a lower layer (e.g., MAC layer), and RLC PDUs can be delivered to a lower layer when the transmission opportunity is notified. That is, the flow control request information may include the amount of data requested by the MAC layer to the RLC layer.

In another embodiment (embodiment 1-2), the flow control request information may include a data forwarding indicator.

For example, the data forwarding indicator may be an indicator for requesting data transmission or data transmission suspension (hereinafter referred to as a "data transmission / transmission stop request indicator"). That is, the secondary base station periodically evaluates " information on the total size of RLC PDUs indicated by the MAC layer, the specific transmission opportunity of which is notified to the RLC layer by the MAC layer " And transmits to the master base station an indicator for requesting suspension of transmission.

At this time, the evaluation is performed based on the situation of receiving the current data and the measured value (for example, the periodic report of the PDCP layer or the average value taken for a predetermined time period in the " (E.g., a value obtained by periodically reporting a value filtered during a predetermined time interval through a filtering method of the IHR filtering method).

As another example, the data forwarding indicator may be an indicator requesting a change in the amount of data (e.g., increase or decrease) (hereinafter, referred to as a "amount of data change request indicator"). That is, the secondary base station periodically evaluates the information on the total size of the RLC PDUs indicated by the MAC layer, the specific transmission opportunity of which is notified to the RLC layer by the MAC layer, for a certain period of time and periodically changes the amount of data to the PDCP layer Yes, increase or decrease) to the master base station.

At this time, the evaluation is performed based on the situation of receiving the current data and the measured value (for example, the periodic report of the PDCP layer or the average value taken for a predetermined time period in the " (E.g., a value obtained by periodically reporting a value filtered during a predetermined time interval through a filtering method of the IHR filtering method).

Meanwhile, the data amount change request indicator may indicate a relative amount based on the data amount received at the RLC layer in the current secondary base station. For example, the data amount change request indicator indicates '000' if the current amount of data to be received is maintained, '001' if the current amount of data to be received is reduced to 1/2 of the current amount of received data, / 4 ", and " 011 " in the case of decreasing to the minimum data amount. Alternatively, the data amount change request indicator may be set to '101' to increase the amount of data currently received, '110' to increase the data amount to four times the current amount of data to be received, 111 ". Alternatively, the data amount change request indicator may be defined as '0' if the amount of data currently received is maintained, or '1' if the data amount is to be reduced to a minimum amount of data.

As another example (Embodiment 1-3), the flow control request information may include a buffer information indicator generated based on state information of a buffer in the secondary base station. Through this, it is possible to calculate a value effective for traffic distribution, while being less affected by fluctuations of radio resources sensitive to changes with time.

For example, the buffer information indicator may be generated based on a data processing time (or a residence time in a buffer) or a loss rate (or a data rate dropped in a buffer).

The buffer may be in bearer split form. Alternatively, the buffer may be a buffer in the RLC layer configured for a single RB. Alternatively, the buffer may be at least one of buffers existing in all layers below the RLC in the RB.

The buffer information indicator may be an indicator for requesting data transmission or data transmission stop, or an indicator for requesting a change in amount of data (e.g., increase or decrease).

At this time, the secondary base station periodically evaluates " information on the total size of RLC PDUs indicated by the MAC layer that a specific transmission opportunity is notified to the RLC layer by the MAC layer " for a predetermined time period, periodically transmits data to the PDCP layer, And transmits to the master base station an indicator for requesting suspension of transmission.

At this time, the evaluation is performed based on the situation of receiving the current data and the measured value (for example, the periodic report of the PDCP layer or the average value taken for a predetermined time period in the " (E.g., a value obtained by periodically reporting a value filtered during a predetermined time interval through a filtering method of the IHR filtering method).

As another example (1-4), the flow control request information includes information such as processing delay / loss rate / data throughput generated based on state information of a buffer in the secondary base station .

The processing delay may mean a data processing time or a residence time in a buffer. The loss rate may refer to the data rate dropped in the buffer.

The buffer may be in bearer split form. Alternatively, the buffer may be a buffer in the RLC layer configured for a single RB. Alternatively, the buffer may be at least one of buffers existing in all layers below the RLC in the RB.

≪ Second embodiment Master-slave RLC scheme >

The flow control request information is not related to transmission from the RLC layer in the secondary base station to the PDCP layer in the master base station but to the transfer from the slave RLC layer in the secondary base station to the master base RLC layer in the master base station.

The secondary base station determines the " size of the transport block " to be allocated to each subframe in the MAC scheduler.

The secondary base station (i.e., the MAC scheduler) determines the size of the transport block and the amount of data requested to the slave RLC layer (i.e., the total number of RLC PDUs indicated by the lower layer when a specific transmission opportunity is notified by the lower layer) Size ") " to be reported to the master RLC layer.

The secondary base station transmits the flow control request information to the master base station. For example, the flow control request information may be transmitted from the secondary base station to the master base station during the downlink transmission, and a signaling protocol configured for exchanging information between the base station and the X2 interface protocol may be used for transmission of the flow control request information. That is, information on the amount of data to be transmitted through the RB and transmitted through the secondary base station is transmitted to the master base station.

FIG. 10 is a block diagram showing an example of a device for operating data of a radio link control layer according to the present invention.

Referring to FIG. 10, the secondary base station may include a control unit 1005 and a transmission unit 1010. For example, the controller 1005 may be a processor, and the transmitter 1010 may be an antenna.

The controller 1005 may include a MAC scheduler.

The controller 1005 determines a " transport block size " to be allocated to each subframe in the MAC layer (hereinafter referred to as a MAC scheduler).

The control unit 1005 determines the size of the transport block and the amount of data (i.e., the total size of the RLC PDUs indicated by the lower layer when a specific transmission opportunity is notified by the lower layer) requested by the RLC layer Flow control request information " to be reported to the PDCP layer (i.e., the PDCP layer of the master base station).

The transmitting unit 1010 transmits the flow control request information to the master base station. For example, the flow control request information may be transmitted from the secondary base station to the master base station during the downlink transmission, and a signaling protocol configured for exchanging information between the base station and the X2 interface protocol may be used for transmission of the flow control request information. That is, information on the amount of data to be transmitted through the secondary base station among the total data amount to be transmitted through the RB is transmitted to the master base station.

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 (14)

A method of operating a base station in a wireless communication system,
Determining a transport block size to be allocated to each subframe in the MAC layer;
Determining flow control request information to be reported to a PDCP layer of a dual connected master BS based on the size of the transport block and the amount of data requested to the RLC layer in the MAC layer;
And forwarding the flow control request information to the master base station. The method according to claim 1,
Wherein the flow control request information is delivered using a signaling protocol configured for X2 interface protocol or BTS information exchange during downlink transmission. The method according to claim 1,
Wherein the flow control request information includes information about an amount of data to be transmitted through the base station among a total amount of data to be transmitted through a radio bearer. The method according to claim 1,
Wherein the flow control request information includes a total size of RLC PDUs indicated by a lower layer when a specific transmission opportunity is notified by a lower layer. 5. The method of claim 4,
Wherein the flow control request information includes an average value of a total size of RLC PDUs indicated by a lower layer during a certain time interval when the lower layer reports a specific transmission opportunity. 5. The method of claim 4,
Wherein the flow control request information comprises a value filtered over a predetermined time interval through a predetermined filtering scheme for a total size of RLC PDUs indicated by a lower layer when a lower layer indicates a specific transmission opportunity. The method according to claim 6,
Wherein the predetermined filtering scheme is IIR filtering. The method according to claim 1,
Wherein the flow control request information comprises an indicator data transmission / transmission stop request indicator requesting data transmission or data transmission suspension. The method according to claim 1,
Wherein the flow control request information comprises a data amount change request indicator requesting a data amount change. The method according to claim 1,
Wherein the flow control request information comprises a buffer information indicator generated based on state information of a buffer in the base station. 11. The method of claim 10,
Wherein the buffer information indicator is generated based on a data processing time or loss rate. The method according to claim 1,
Wherein the flow control request information includes at least one of a processing delay, a loss rate, and a data throughput based on state information of a buffer in the base station. The method according to claim 1,
Wherein the flow control request information is communicated through the MAC layer. A base station for operating data for a dual-connected terminal in a wireless communication system,
The MAC layer determines a size of a transport block to be allocated to each subframe and a size of the transport block and a size of a PDCP layer Which is information to report on the flow control request information; And
And a transmitting unit for transmitting the flow control request information to the master base station,
Wherein the flow control request information includes information on an amount of data to be transmitted through the base station among a total amount of data to be transmitted through a radio bearer.

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