KR20150109098A - Method and apparatus for transmitting buffer status report in wireless communication system supporting device to device communication - Google Patents

Abstract

A method and apparatus for transmitting a buffer status report in a wireless communications system supporting device to device communications. A method for transmitting a buffer status report in a wireless communications system supporting device to device communications includes a step of performing the triggering of a buffer status report when at least two logical channel groups (LCG) having data to be transmitted exist and at least one LCG has data to be transmitted to the D2D communications of the LCG, a step of producing a truncated buffer status report based on the number of LCG and the amount of uplink resource allocated from and the base station, and a step of transmitting the truncated buffer status report with the format of a media access control (MAC) control factor to the base station. The truncated buffer status report may include the identification information (LCG ID) of the LCG including a logical channel having the highest priority among the logical channels having data to be transmitted to the uplink, and buffer size information corresponding to the LCG including a logical channel having the highest priority.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for transmitting a buffer status report in a wireless communication system supporting inter-

The present invention relates to wireless communication, and more particularly, to a method and apparatus for operating a buffer state report in a wireless communication system supporting device-to-device communication.

D2D (Device to Device) communication is a communication method that has been available since the time of analog radio, and has a very long history. However, D2D communication in a wireless communication system is different from existing D2D communication.

D2D communication in a wireless communication system uses communication technology of the wireless communication system in a frequency band of the wireless communication system or other bands, but does not directly communicate user data between terminals without going through an infrastructure (e.g., a base station) . This provides the advantage of enabling wireless communication in areas other than the limited wireless communication infrastructure and reducing the network load of the wireless communication system.

In order to perform inter-terminal communication in such a wireless communication system, a base station needs to schedule resources required for in-coverage terminals to transmit data through D2D communication. To this end, The amount of data to be transmitted through the D2D communication in the buffer must be reported to the base station via a buffer state report. However, since the existing wireless communication system supports only a form in which the UE transmits a buffer status report for uplink data to the base station, a criterion for transmitting a buffer status report for data to be transmitted through D2D communication is required.

SUMMARY OF THE INVENTION The present invention provides a method for transmitting a buffer status report in a wireless communication system supporting inter-terminal communication.

It is another object of the present invention to provide an apparatus for transmitting a buffer status report in a wireless communication system supporting inter-terminal communication.

Another aspect of the present invention is to provide a method for efficiently allocating resources for communication between terminals in a wireless communication system supporting inter-terminal communication.

According to an aspect of the present invention, in a wireless communication system supporting D2D (Device to Device) communication, a buffer status report transmission method by a terminal includes a logical channel group (LCG: Logical Channel Group) And triggering a buffer status report when at least one LCG among the LCGs has data to be transmitted through the D2D communication, the method comprising the steps of: Generating a truncated buffer status report and transmitting the truncated buffer status report to the base station in the format of a MAC (Media Access Control) control element, wherein the truncated buffer status report includes uplink (LCG ID) of the LCG including the logical channel having the highest priority among the logical channels having the data to be transmitted to the LCG And buffer size information corresponding to the LCG including the logical channel having the highest priority.

According to another aspect of the present invention, there is provided a method of transmitting a buffer status report by a terminal in a wireless communication system supporting D2D communication, comprising the steps of: determining whether there is more than one LCG having data to be transmitted and at least one LCG among the LCGs Generating a truncated buffer status report based on the number of LCGs and an uplink resource amount allocated from a base station, and transmitting the truncated buffer status report to a format of a MAC control element Wherein the truncated buffer status report includes an LCG ID of an LCG including a logical channel having data to be transmitted through the D2D communication and a logical channel having data to be transmitted through the D2D communication, And buffer size information corresponding to the LCG including the buffer size information.

According to another aspect of the present invention, in a wireless communication system supporting D2D communication, a terminal transmitting a buffer status report has at least two LCGs having data to be transmitted, and at least one of the LCGs transmits data A processor for generating a truncated buffer status report on the basis of the number of LCGs and an uplink resource amount allocated from a base station when triggering of the buffer status report is performed; (LCG ID) of an LCG including a logical channel having a highest priority among logical channels having data to be transmitted in an uplink, and a transmitter for transmitting the LCG ID of the highest priority The buffer size information corresponding to the LCG including the logical channel, It may generate a truncated BSR.

According to another aspect of the present invention, in a wireless communication system supporting D2D communication, a terminal transmitting a buffer status report has at least two LCGs having data to be transmitted, and at least one of the LCGs transmits data A processor for generating a truncated buffer status report on the basis of the number of LCGs and an uplink resource amount allocated from a base station when triggering of the buffer status report is performed; (LCG ID) including a logical channel having data to be transmitted in the D2D communication and a logical channel having data to be transmitted in the D2D communication, The buffer status report may be generated using the corresponding buffer size information.

According to another aspect of the present invention, a method for allocating resources for D2D communication by a base station in a wireless communication system supporting D2D communication includes receiving a buffer status report from a terminal, Determining whether there is data to be transmitted in the D2D communication based on at least one of a Logical Channel ID (LCID) and a Logical Channel Group ID (LCG ID); and transmitting the D2D communication And allocating resources for D2D communication to the terminal when it is determined that there is data to be transmitted to the terminal.

According to the present invention, a terminal or a base station allocating resources for inter-terminal communication in an inter-terminal communication can efficiently allocate resources to terminals existing within a service range.

1 is a diagram showing a network structure of a wireless communication system.
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 a structure of a bearer service in a wireless communication system.
5 is a diagram illustrating a process in which a mobile station transmits data to a base station in a wireless communication system.
6 is a diagram illustrating a structure of a Media Access Control (MAC) PDU (Protocol Data Unit) in a wireless communication system.
7 and 8 are diagrams illustrating an example of a MAC subheader in a wireless communication system.
9 is a diagram showing the MAC control element of the buffer status report.
10 is a flowchart illustrating a method of transmitting a buffer status report by a UE according to an embodiment of the present invention.
11 is a flowchart illustrating a method of allocating resources for inter-terminal communication according to an embodiment of the present invention.
12 is a block diagram illustrating a terminal and a base station according to an embodiment of 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 included in the network.

1 is a diagram showing a network structure of a wireless communication system.

FIG. 1 shows a network structure of an evolved-universal mobile telecommunications system (E-UMTS) system as an example of a wireless communication 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.

Referring to FIG. 1, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) includes a Base Station (BS) providing a control plane (CP) and a user plane (UP) (eNB: evolved NodeB, 20).

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) have.

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, or the like. The base stations 20 are physically connected through an optical cable or a DSL (Digital Subscriber Line), and can exchange signals and messages with each other through the X2 or Xn interface. In FIG. 1, for example, the base stations 20 are connected through an X2 interface.

In the following, the description of the physical connection is omitted and the logical connection is described. As shown in FIG. 1, the base station 20 is connected to an evolved packet core (EPC) 30 through an S1 interface. More specifically, the base station 20 is connected to an MME (Mobility Management Entity) through an S1-MME interface and is connected to an S-GW (Serving Gateway) through an S1-U interface. The base station 20 exchanges context information of the MME with the terminal 10 and information for supporting the mobility of the terminal 10 through the S1-MME interface. And sends and receives data to be served to the S-GW and each terminal 10 through the S1-U interface.

Although not shown in FIG. 1, the EPC 30 includes an MME, an S-GW, and a packet data network-gateway (P-GW). The MME has information on the connection information of the terminal 10 and the capability of the terminal 10. This information is mainly used for managing the mobility of the terminal 10. [ The S-GW is a gateway having an E-UTRAN as an end point, and the P-GW is a gateway having a PDN (Packet Data Network) as an end point.

The E-UTRAN and the EPC 30 may be combined to form an EPS (Evolved Packet System). The traffic flow from the wireless link to the base station 20 to the PDN that connects the terminal 10 to the service entity (Internet Protocol).

The wireless interface between the terminal 10 and the base station 20 is referred to as a "Uu interface ". The layers of the radio interface protocol between the terminal 10 and the network are divided into a first layer L1 defined by a 3rd Generation Partnership Project (3GPP) series wireless communication system (UMTS, LTE, LTE-Advanced, etc.) A second layer L2 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, (10) 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 MAC layer (Media Access Control) layer through a transport channel. The data is transmitted between the MAC layer and the physical layer through a transmission channel. The transport channel is classified according to how the data is transmitted over the air interface.

In addition, data is transmitted 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 (DLH), a downlink shared channel (DL-SCH), and Hybrid Automatic Repeat Request (HARQ) And an uplink scheduling grant informing the UE of the resource allocation of the uplink transmission. The Physical Control Format Indicator CHannel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs and is transmitted every subframe. Also, the PHICH (Physical Hybrid ARQ Indicator CHannel) carries HARQ ACK / NAK signals in response to the uplink transmission. Also, the Physical Uplink Control CHannel (PUCCH) carries uplink control information such as HARQ ACK / NAK, scheduling request and CQI for downlink transmission. Also, the Physical Uplink Shared CHannel (PUSCH) carries UL-SCH (Uplink Shared CHannel). If necessary, the PUSCH may include CSI (Channel State Information) information such as HARQ ACK / NACK and CQI 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, there are data transmission or radio resource allocation as services provided from the MAC layer to the upper layer.

The function of the RLC layer includes concatenation, segmentation and reassembly of the RLC SDUs. The RLC layer includes a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (AM) to guarantee various QoSs required by a radio bearer (RB) Acknowledged Mode).

In general, transparent mode is used to set the initial connection.

The unacknowledged mode is for data streaming or real-time data transmission such as Voice over Internet Protocol (VoIP), and is a speed-focused mode rather than a data reliability. 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 base station determines the mode of the RLC in the RB corresponding to each EPS bearer based on the Quality of Service (QoS) information of each EPS bearer connected to the UE and configures the parameters in the RLC so as 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 (PDUs) are defined only when a transmission opportunity from a lower layer (eg, the MAC layer) is notified and forwarded to the 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 functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include delivery of user data, header compression and ciphering, and delivery 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. A radio bearer (RB) refers to 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. RB may be classified into SRB (Signaling RB) and 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.

The non-access stratum (NAS) layer located at the top of the RRC layer performs functions such as session management and mobility management. When there is an RRC connection between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in an RRC connected state. Otherwise, the UE is in an RRC idle state do.

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

4 is a diagram showing a structure of a bearer service in a wireless communication system.

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

When the UE transmits data to the external Internet network, the UE transmits data to the eNB through the RB on the radio. Then, the base station transmits the data received from the terminal to the S-GW through the S1 bearer. The S-GW carries the data received from the base station through the S5 / S8 bearer to the P-GW, and finally the data is transmitted to the destination existing in the P-GW and the external internet network through the external bearer.

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

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

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

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

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

RB means two kinds of data RB (data radio bearer) and signaling RB (signaling radio bearer). However, in the present invention, RB is a DRB provided in a Uu interface to support a user service . Therefore, the RB that is expressed separately is distinguished from the SRB. RB is a path through which user plane data is transmitted, and SRB is a path through which control plane data such as an RRC layer and a NAS control message are transmitted. There is a one-to-one mapping between RB, E-RAB and EPS bearer.

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

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

5 is a diagram illustrating a process in which a mobile station transmits data to a base station in a wireless communication system.

As shown in FIG. 5, when a buffer state report (BSR) is triggered (S510) in response to the presence of data to be transmitted on the uplink, A Scheduling Request (SR) is transmitted in order to induce allocation of a link resource (S520), and an uplink grant (UL grant) to the SR is received from the base station in operation S530.

The SR is transmitted to the base station via the PUCCH. If an SR is triggered, the SR is pended until canceled. The UE can not receive all the data pending for the uplink grant transmission, or the BSR in which a MAC PDU is configured and the MAC PDU is configured in a buffer state including the last generated event If so, cancel all pending SRs and stop the timer (sr-ProhibitTimer) to prevent the SR from being sent.

More specifically, if the SR is triggered and the currently pending SR is not available, the terminal sets the SR count (SR_COUNTER) value to zero. However, if SR is pending and there is a valid PUCCH resource to send an SR at this Transmission Time Interval (TTI) and this TTI is not part of a measurement gap and sr-ProhibitTimer is not in progress If the value of SR_COUNTER is less than the maximum number of transmissions of the SR, increase the SR count value by 1 and instruct the physical layer to transmit the SR signal through the PUCCH and then start the sr-ProhibitTimer. However, if the SR_COUNTER value is greater than or equal to the maximum number of transmissions, the RRC is informed of the release of the PUCCH and SRS and clears all configured downlink allocations and uplink grants. Then, it initializes the random access procedure and cancels all pending SRs.

On the other hand, if the SR is pending but there is no available UL-SCH resource for transmission in any TTI, the UE initializes the random access procedure and cancels all pending SRs.

Upon receiving the uplink grant for the SR, the MS transmits the BSR to the BS (S540). Upon receiving the uplink grant for the BSR from the base station (S550), the base station transmits data using resources allocated for uplink data transmission (S560). The BSR informs the serving BS of information on the amount of transmittable data present in the uplink buffer, and provides support for QoS-aware packet scheduling for the uplink. The BSR procedure is performed after the SR transmission.

The base station controls a BSR procedure for a logical channel in each terminal by configuring a periodic BSR timer and a retransmission BSR timer (retxBSR-Timer) through signaling defined in the RRC layer. A logical channel group (LCG) can be configured with selective signaling, and the BSR can be performed on the LCG.

In a wireless communication system, a UE configures a BSR based on data buffered in each LCG in a UE. A maximum of four LCGs can be configured in a terminal. The BSR format includes a short BSR for reporting buffer status corresponding to one LCG, a long BSR for reporting buffer status corresponding to four LCGs, and a truncated BSR. The format of the BSR will be described in more detail with reference to FIG. 9 to be described later.

For the BSR procedure, the terminal shall consider a suspended radio bearer (RB) and all RBs not reserved.

The BSR can be divided into a general BSR (Regular BSR), a padding BSR (padding BSR), and a periodic BSR (periodic BSR). In general BSR, there is data that can be transmitted to a logical channel included in the LCG exists in the RLC entity or PDCP entity, or there exists uplink data that can be transmitted to a logical channel having a higher priority than other logical channels in which data that can be transmitted exist Triggered. Also, the general BSR is triggered even if the retxBSR-Timer expires and the terminal has data that can be transmitted to the logical channel in the LCG. The padding BSR is triggered when the uplink resources are allocated and the number of padding bits is equal to or greater than the size for the BSR transmission. The periodic BSR is triggered when the periodicBSR-Timer expires.

The general BSR and the periodic BSR are transmitted in a long BSR format when more than one LCG (at least two LCGs) have data to be transmitted in the TTI to which the corresponding BSR is transmitted. Otherwise, if only one LCG has data to be transmitted, It is transmitted in short BSR format.

The padding BSR is equal to or larger than the sum of the BSR having the shortest number of padding bits included in the MAC PDU and the subheader of the short BSR but smaller than the sum of the long BSR and the long BSR's subheader, If more than one LCG has data to transmit, it is transmitted in the truncated BSR format for the LCG that contains the logical channel with the highest priority in the data transmission. Otherwise, it is transmitted in short BSR format. The padding BSR is transmitted in the long BSR format when the number of padding bits is equal to or larger than the sum of the long BSR and the long BSR subheader.

The terminal performs the BSR procedure when at least one BSR is triggered and not canceled. The UE instructs the multiplexing and assembly procedure for generation of the BSR MAC control element if the uplink resource for the new transmission is assigned to this TTI, starts or restarts the periodic BSR-Timer, and starts or restarts the retxBSR-Timer. Here, the procedure for starting or restarting the periodic BSR-Timer is excluded when a short-axis BSR is generated. If the uplink resource for the new transmission is not allocated to this TTI, the normal BSR is triggered.

 The SR is triggered if the uplink grant is not configured or if the normal BSR is not triggered by the presence of transmittable uplink data on a particular logical channel for which SR masking has been set up. That is, SR is triggered when a generic BSR is triggered by a particular logical channel for which SR masking has not been set up.

At this time, one MAC PDU must include only one MAC control element even if a plurality of BSRs are triggered. And, when it is possible to transmit a normal BSR and a periodic BSR, this always takes precedence over the padding BSR. Also, when confirming reception of an indicator for instructing transmission of new data to all UL-SCHs, the terminal restarts the retxBSR-Timer. All triggered BSRs should be canceled upon receipt of an uplink grant that can send all pending data but can not send additional BSR MAC control elements. Also, all triggered BSRs should be canceled when the BSR is included in the MAC PDU.

The UE transmits one normal / periodic BSR in one TTI. If the UE has been requested to transmit a plurality of MAC PDUs in one TTI, one padding BSR may be included in any MAC PDUs not including the normal / periodic BSR. All BSRs always reflect the buffer status after all MAC PDUs are configured in the TTI where the BSR is transmitted. Each LCG reports one buffer status value per TTI, and the buffer status value is reported in all BSRs via the BSR for the LCG. That is, one BSR value should be transmitted for each LCG in the same TTI, and the buffer status value for LCG in all BSRs transmitted in the same TTI should be the same value. On the other hand, padding BSRs are not allowed to cancel normal / periodic BSRs. The padding BSR is triggered for a specific MAC PDU, and the trigger of the padding BSR is canceled when a specific MAC PDU is generated. Hereinafter, the MAC PDU will be described in more detail with reference to FIGS.

FIG. 6 is a diagram illustrating a structure of a MAC PDU (Protocol Data Unit) in a wireless communication system, and FIGS. 7 and 8 are views showing an example of a MAC subheader in a wireless communication system. The MAC PDU may be referred to as a transport block.

6, a MAC header 610, n MAC control elements 620-1,... 620-n, m MAC SDUs 630- 1, ..., 630-m and padding 640 are shown. MAC PDU 600 includes MAC header 610, zero or at least one MAC control element 620-1, ..., 425-n, 0 or at least one MAC SDU 630-1. ..., 630-m, and padding 640, respectively. The sizes of the MAC header 610 and the MAC SDUs 630-1, ..., and 630-m may be variable.

The MAC header 410 includes at least one sub-header 610-1, 610-2, 610-3, 610-4, ..., 610-k, and each subheader 610- 610-1, 610-2, 610-3, 610-4, ..., 610-k are respectively associated with MAC control elements 620-1, ..., 620-n, MAC SDUs 630-1, , 630-m, or padding 640, respectively. The order of the subheaders 610-1, 610-2, 610-3, 610-4, ..., 610-k corresponds to the corresponding MAC control elements 620-1, ..., , 620-n, MAC SDUs 630-1, ..., 630-m, or padding 640.

Each of the subheaders 610-1, 610-2, 610-3, 610-4, ... 610-k includes six fields such as R, R, E, LCID, F and L, R, E, and LCID. The subheader including the four fields is a subheader corresponding to the MAC control elements 620-1, ..., 620-n or the padding 640. The subheader including the six fields includes a MAC SDU 630 -1, ..., 630-m.

The MAC control elements 620-1, ..., 620-n are control messages generated by the MAC layer and are located in front of the MAC SDUs 630-1, ..., 630-m. The MAC SDUs 630-1, ..., and 630-m are the same as the RLC PDUs delivered from the RLC (Radio Link Control) layer. The padding 640 is a predetermined number of bits to be added such that the size of the MAC PDU 600 is constant and is always appended to the end of the MAC PDU 600 except when one byte or two bytes of padding is required. . The terminal ignores the value of the padding 640. The MAC control elements 620-1 to 620-n, the MAC SDUs 630-1 to 630-m, and the padding 640 are collectively referred to as a MAC payload.

7 shows a structure of a MAC subheader including six fields R, R, E, LCID, F and L, and four fields R, R, E and LCID in FIG. The structure of the MAC subheader including the MAC header is shown. Hereinafter, the fields included in the MAC subheader will be described in more detail.

The logical channel ID (LCID) field is a field for identifying a logical channel of a corresponding MAC SDU or identifying a type of a corresponding MAC control element or padding. The length (size) of the LCID field is 5 bits. The LCID field is one MAC SDU included in the MAC PDU, one MAC control element, or one per padding.

The L field is a field for identifying the length of the MAC SDU or the length of a variable-sized MAC control element. The length of the L field is indicated by a format (F: Format) field. . In Fig. 7, for example, the length of the L field is 7 bits and the sub-header is 15 bits.

The F field is a field for identifying the length of the L field, and may have a length of 1 bit. If the length of the MAC SDU or variable size MAC control element is less than 128 bytes, the value of the F field may be set to "0 "; otherwise, it may be set to" 1 ".

The Extension (E) field is a flag that identifies whether other fields are present in the MAC header. When set to "1", there is at least another set of R / R / E / LCID fields. Indicates that the MAC SDU, MAC control element or padding is started in the next byte when set to "0 ".

The R (Reserved) field is a reserved field and is set to "0 ".

9 is a diagram showing the MAC control element of the buffer status report.

Referring to FIG. 9, a MAC control element a of a short BSR and a truncated BSR is composed of one LCG ID field and one buffer size (BS) field corresponding thereto. The MAC control element b of the long BSR is composed of four buffer size fields corresponding to four LCG IDs (# 0 LCG ID to # 3 LCD ID). The BSR format is identified by the value of the logical channel identifier (LCID) contained in the subheader of the MAC PDU. The LCID values for the uplink are shown in Table 1 below.

Index LCID values 00000 CCCH 00001-01010 Identity of the logical channel 01011-11000 Reserved 11001 Extended Power Headroom Report 11010 Power Headroom Report 11011 C-RNTI 11100 Truncated BSR 11101 Short BSR 11110 Long BSR 11111 Padding

The LCG ID field is used to identify a logical channel group in which the buffer status is reported to the base station, and the length of the LCD ID field is 2 bits. The buffer size field is used to identify the total amount of data available in all logical channels in the LCG after all the MAC PDUs to be transmitted during one TTI are constructed. The buffer size field is used to identify the total amount of data available in the RLC layer and the PDCP layer Information. Here, the RLC header and the PDCP header are not considered in the buffer size calculation. The length of the buffer size field is 6 bits. Table 2 shows the values of the buffer size field when the extended BSR size (extendedBSR-size) is not set. Table 3 shows the values of the buffer size field when the extended BSR size is set.

index Buffer size value (bytes) index Buffer size value (bytes) 0 BS = 0 32 1132 <BS <= 1326 One 0 < BS < = 10 33 1326 <BS <= 1552 2 10 <BS <= 12 34 1552 <BS <= 1817 3 12 <BS <= 14 35 1817 <BS <= 2127 4 14 <BS <= 17 36 2127 <BS <= 2490 5 17 <BS <= 19 37 2490 <BS <= 2915 6 19 <BS <= 22 38 2915 <BS <= 3413 7 22 <BS <= 26 39 3413 <BS <= 3995 8 26 <BS <= 31 40 3995 <BS <= 4677 9 31 <BS <= 36 41 4677 <BS <= 5476 10 36 <BS <= 42 42 5476 <BS <= 6411 11 42 <BS <= 49 43 6411 <BS <= 7505 12 49 <BS <= 57 44 7505 <BS <= 8787 13 57 <BS <= 67 45 8787 <BS <= 10287 14 67 <BS <= 78 46 10287 <BS <= 12043 15 78 <BS <= 91 47 12043 <BS <= 14099 16 91 <BS <= 107 48 14099 <BS <= 16507 17 107 <BS <= 125 49 16507 <BS <= 19325 18 125 <BS <= 146 50 19325 <BS <= 22624 19 146 <BS <= 171 51 22624 <BS <= 26487 20 171 <BS <= 200 52 26487 <BS <= 31009 21 200 <BS <= 234 53 31009 <BS <= 36304 22 234 <BS <= 274 54 36304 <BS <= 42502 23 274 <BS <= 321 55 42502 <BS <= 49759 24 321 <BS <= 376 56 49759 <BS <= 58255 25 376 <BS <= 440 57 58255 <BS <= 68201 26 440 <BS <= 515 58 68201 <BS <= 79846 27 515 <BS <= 603 59 79846 <BS <= 93479 28 603 <BS <= 706 60 93479 <BS <= 109439 29 706 <BS <= 826 61 109439 <BS <= 128125 30 826 <BS <= 967 62 128125 <BS <= 150000 31 967 <BS <= 1132 63 BS> 150000

index Buffer size value (bytes) index Buffer size value (bytes) 0 BS = 0 32 4940 <BS <= 6074 One 0 < BS < = 10 33 6074 <BS <= 7469 2 10 <BS <= 13 34 7469 <BS <= 9185 3 13 <BS <= 16 35 9185 <BS <= 11294 4 16 <BS <= 19 36 11294 <BS <= 13888 5 19 <BS <= 23 37 13888 <BS <= 17077 6 23 <BS <= 29 38 17077 <BS <= 20999 7 29 <BS <= 35 39 20999 <BS <= 25822 8 35 <BS <= 43 40 25822 <BS <= 31752 9 43 <BS <= 53 41 31752 <BS <= 39045 10 53 <BS <= 65 42 39045 <BS <= 48012 11 65 < BS < = 80 43 48012 <BS <= 59039 12 80 <BS <= 98 44 59039 <BS <= 72598 13 98 <BS <= 120 45 72598 <BS <= 89272 14 120 <BS <= 147 46 89272 <BS <= 109774 15 147 <BS <= 181 47 109774 <BS <= 134986 16 181 <BS <= 223 48 134986 <BS <= 165989 17 223 <BS <= 274 49 165989 <BS <= 204111 18 274 <BS <= 337 50 204111 <BS <= 250990 19 337 <BS <= 414 51 250990 <BS <= 308634 20 414 <BS <= 509 52 308634 <BS <= 379519 21 509 <BS <= 625 53 379519 <BS <= 466683 22 625 <BS <= 769 54 466683 <BS <= 573866 23 769 <BS <= 945 55 573866 <BS <= 705666 24 945 <BS <= 1162 56 705666 <BS <= 867737 25 1162 <BS <= 1429 57 867737 <BS <= 1067031 26 1429 <BS <= 1757 58 1067031 <BS <= 1312097 27 1757 <BS <= 2161 59 1312097 <BS <= 1613447 28 2161 <BS <= 2657 60 1613447 <BS <= 1984009 29 2657 <BS <= 3267 61 1984009 <BS <= 2439678 30 3267 <BS <= 4017 62 2439678 <BS <= 3000000 31 4017 <BS <= 4940 63 BS> 3000000

In order to report the buffer status, the UE transmits data not included in the RLC data PDU among the RLC SDUs or segments of the RLC SDUs and the data reserved for retransmission in the RLC AM mode among the RLC data PDUs or portions of the RLC data PDU Lt; RTI ID = 0.0 &gt; RLC &lt; / RTI &gt; Additionally, if a STATUS PDU is triggered and the t-StatusProhibit timer is not in progress or has expired, the terminal estimates the size of the STATUS PDU to be transmitted on the next transmission opportunity and also reports the transmittable data in the RLC layer to be included in the buffer status report .

In addition, if the SDU itself has not yet been processed by the PDCP for the SDUs for the PDUs that have not been delivered to the lower layer, or the PDCP control PDUs as well as the PDU processed by the SDU by the PDCP, It is possible to consider the data as transmittable. In addition, if the PDCP entity has previously performed a re-establishment procedure for the RBs mapped to the acknowledged mode of operation of the RLC, the UE has not yet been processed by the PDCP of the SDU, It is possible to consider the PDUs processed by the PDCP layer as data that can be transmitted in the PDCP layer. At this time, if the transfer of the PDUs among the SDUs corresponding to the PDUs transmitted to the lower layer prior to the PDCP re-establishment is received from the PDU status report among the SDUs starting from the first SDU not confirmed from the lower layer The SDUs confirmed to have been successfully delivered through the PDCP status report are excluded.

In the meantime, when the terminal performs D2D communication, the terminal transmits the D2D communication information to the base station in order to schedule resources required for transmitting data in D2D communication to the terminals in- The amount of uplink data to be transmitted in the D2D communication (hereinafter referred to as &quot; D2D data &quot;) must be known in addition to the information on how much the uplink data exists in the buffer. However, the existing wireless communication system supports only the form in which the UE reports the buffer status for the uplink data as described above. Therefore, the present invention proposes a method of reporting the buffer status of D2D data to the base station as follows.

10 is a flowchart illustrating a method of transmitting a buffer status report by a UE according to an embodiment of the present invention.

A terminal supporting D2D communication can perform D2D communication when a user of the terminal sets up the terminal to enable D2D communication through a user interface (UI). Or, a D2D server that manages a ProSe (Proximity Services) ID and a ProSe application ID of a terminal using D2D communication, a serving base station of the terminal, etc.) of a network (for example, It is possible to finally determine whether or not the D2D communication can be performed by the terminal set to be D2D communication. That is, the terminal may perform inter-terminal communication only when the inter-terminal communication of the terminal is permitted by the network even if the terminal is set to enable inter-terminal communication by the user of the terminal. Information on whether or not D2D communication is possible can be displayed on the screen of the terminal.

The resources for D2D communication may be allocated by a terminal (hereinafter, cluster head) or a base station that is responsible for allocating resources for D2D communication in D2D communication. Therefore, when the terminal performs D2D communication, the terminal must transmit the BSR for the D2D data to the base station or the cluster head. Hereinafter, for convenience of explanation, the base station and the cluster head are collectively referred to as a base station.

Meanwhile, a terminal supporting D2D communication can process D2D data and cellular (e.g., LTE) uplink data (hereinafter referred to as uplink data) in one MAC layer. Alternatively, a MAC layer for D2D communication and a MAC layer for cellular communication may exist independently of each other in a terminal supporting D2D communication. Hereinafter, when the D2D data and the uplink data are processed in one MAC layer or the MAC layer for D2D communication and the MAC layer for cellular communication exist independently of each other in the terminal supporting D2D communication, Layer transmits BSR-related information to the MAC layer for cellular communication, and a single BSR message is generated and transmitted in the MAC layer for the cellular communication.

When D2D communication is enabled in the terminal, at least one RB for D2D communication and parameters related to the RB may be configured in the terminal. The RB for D2D communication may be mapped to at least one logical channel (LC) and a logical channel group (LCG).

LC for D2D communication (LC where data to be transmitted by D2D communication exists) can always be set to a fixed value, and LCG for D2D communication can also be set to a fixed value. For example, the LC value may be set to 3 (D2D Voice) and 4 (D2D data), or 10 (D2D data) and 11 (D2D voice). Alternatively, the D2D data may all be set to the same one fixed LC value (3 or 11). Also, LCs for D2D communication may all be included in the same LCG, and the LCG value may be set to a fixed value. In this case, the base station may not separately notify the terminal of the LCG value including LCs for D2D communication. For example, '1' may be used as the LCG value for the D2D communication. The LCG set to the value '1' may not include the LCs corresponding to the RBs configured for wireless communication. The LCG set to the value '1' is for informing the base station through the BSR that data corresponding to the corresponding LCG is data for the D2D, and the LC to be included in the LCG can be set by the base station. On the other hand, the LCG value for D2D communication can also be set by the base station. In this case, the LCs included in the LCG can not be LCs corresponding to the RBs configured for wireless communication.

A terminal supporting D2D communication can report the amount of D2D data present in the buffer and the amount of uplink data to the base station through one BSR. At this time, a short BSR / truncated BSR / long BSR LCID indicating the BSR for reporting the status of the existing UL buffer may be used in the BSR as shown in Table 1. In addition, the value of the buffer size field of the BSR can follow the configuration of Table 2, and when the extended BSR is configured, the configuration of Table 3 can be followed.

The base station can determine whether the buffer size information is for the uplink data or the D2D data based on the LCG value of the BSR. In one example, if a short BSR or truncated BSR is received, the base station may receive a short BSR or truncated BSR based on the LCG ID of the LCG ID field included in the MAC control element of the short BSR or truncated BSR as shown in Figure 9 (a) It can be determined whether the BSR is for the uplink data or the D2D data. In addition, when a long BSR as shown in FIG. 9 (b) is received, the BS determines a buffer size for a predetermined LCG value (for example, LCG 1) among buffer size information (buffer sizes # 1 to # 4) Information (buffer size # 1) as buffer size information for D2D data.

However, as described above, the truncated BSR is equal to or larger than the sum of the BSRs having the shorter number of padding bits included in the MAC PDU and the shorter BSRs, but smaller than the sum of the longer BSRs and the longer BSRs' And the BSR is used only when it has more than one LCG to transmit data in the transmitted TTI. Therefore, only the buffer status for the LCG including the LC having the highest priority among the LCs having the data to be transmitted through the truncated BSR Is reported. Therefore, with the truncated BSR, the base station can not know whether the truncated BSR is transmitted due to the presence of the LCG for the D2D data or the truncated BSR is transmitted due to the presence of the LCG for another uplink data. In addition, the UE may not be able to report the buffer status of the D2D data. For example, when data to be transmitted exists in two LCGs (LCG # 0 and LCG # 1), LCG # 0 corresponds to uplink data, and LCG # 1 corresponds to D2D data, # 0, the BS can not know whether data not reported from the UE (data existing in the LCG # 1) is uplink data or D2D data. Similarly, when data to be transmitted exists in three LCGs (LCG # 0, LCG # 1 and LCG # 2), LCG # 0 and LCG # 2 correspond to uplink data, and LCG # 1 corresponds to D2D data, When reporting the buffer status for the LCG # 0 with the truncated BSR, the BS can not know whether data not reported from the UE (data existing in LCG # 1 and LCG # 2) is uplink data or D2D data.

Therefore, the terminal supporting D2D communication according to the present invention operates as follows to allow the BS to know whether the data not reported from the terminal is uplink data or D2D data, even when transmitting the truncated BSR to the base station .

As shown in FIG. 10, a UE supporting D2D communication has at least one LCG having data to be transmitted, an uplink resource is allocated from the BS, and the number of padding bits to be included in the MAC PDU is equal to the size for BSR transmission If the padding BSR is triggered in step S1010, the base station generates one of a long BSR, a short BSR, and a truncated BSR based on the number of LCGs having data to be transmitted and the amount of uplink resources allocated to the base station in step S1020. The generated BSR is transmitted to the serving BS in the corresponding TTI in the MAC control element format (S 1030).

In this case, if the number of padding bits to be included in the MAC PDU is equal to or greater than the sum of the BSR having the short BSR and the short BSR, If there are two or more LCGs having data to be transmitted in the uplink in the TTI to which the BSR transmits, the LCID is set to the truncated BSR And generates a buffer status report for the LCG including the LC having the highest priority among the LCGs having the data to be transmitted in the uplink, and transmits the buffer status report to the base station in the format of the MAC control element. That is, the UE can generate the truncated BSR considering only the number of LCGs having data to be transmitted in the uplink, without considering the LCG having the D2D data in the TTI to which the BSR is to be transmitted. Since the priority of the D2D data is always lower than that of the uplink data, the BSR information for the uplink data is prioritized.

Meanwhile, according to another embodiment, the MS may have a BSR having a length equal to or greater than a sum of a BSR having a short padding bit number included in a MAC PDU and a subheader of the short BSR based on an uplink resource amount allocated from a BS, If there are two or more LCGs having data to be transmitted and at least one of the LCGs has data to be transmitted in the D2D communication, if the LCG is smaller than the sum of the subheaders of the BSR, then the LCID is set to the truncated BSR, It can generate a buffer status report for the LCG having data and transmit it to the base station in the format of the MAC control element. That is, the LCG including the LC having the highest priority may be an LCG having data to be transmitted in the D2D communication. In this case, the truncated BSR includes buffer size information corresponding to LCG including LC having identification information (LCG ID) of LCG including LC having data to be transmitted through D2D communication and LC having data to be transmitted through D2D communication can do. If D2D communication for public safety is supported, D2D data always precedes uplink data, so BSR for D2D data is transmitted first. In order to support this, the user of the terminal can set the D2D communication for public safety to enable the terminal to perform D2D communication through a user interface (UI), and the set information is transmitted to the base station through RRC signaling Or may be delivered to the MME through a Tracking Area Update (TAU) procedure defined at the NAS layer.

Meanwhile, according to another embodiment, the MS may include a BSR having a length equal to or larger than a sum of a BSR having a shorter number of padding bits included in the MAC PDU and a subheader of the shorter BSR based on the uplink resource amount allocated from the BS, If there is more than one LCG having data to be transmitted and at least one LCG among the LCGs has data to be transmitted in the D2D communication, the LCID is set to the truncated BSR and the uplink is transmitted in the uplink It is possible to generate a buffer status report for the LCG including the LC having the highest priority among the LCs having the data and to transmit it to the base station in the format of the MAC control element. In this case, the truncated BSR corresponds to the LCG including the LC having the highest priority among the LCs having the data to be transmitted in the uplink, and the LCG having the LC having the highest priority The size of the buffer.

At this time, the terminal transmits an LCID including data to be transmitted through D2D communication to the UE by transmitting an LCID identifying the MAC control element as a truncated buffer status report for D2D communication in a subheader corresponding to the MAC control element And informs the base station of its existence. That is, when the base station receives the LCID identifying that it is a truncated buffer status report for D2D communication, it can be confirmed that the LCG having the data to be transmitted through the D2D communication exists in the terminal that transmitted the LCID. For this, an LCID value for uplink as shown in Table 4 below may be used as an example.

Index LCID values 00000 CCCH 00001-01010 Identity of the logical channel 01011-10111 Reserved 11000 Truncated BSR for D2D 11001 Extended Power Headroom Report 11010 Power Headroom Report 11011 C-RNTI 11100 Truncated BSR 11101 Short BSR 11110 Long BSR 11111 Padding

Hereinafter, a case where a MAC layer for D2D communication and a MAC layer for cellular communication exist independently of each other in a terminal supporting D2D communication will be described. In this case, the MAC layer for D2D communication and the MAC layer for cellular communication form a mapping between LC and RB independently of each other. The BS may transmit D2D-related configuration information including the LC and LCG related information to the UE through RRC signaling. The UE applies the D2D-related configuration information only when configuring the MAC layer for D2D communication.

The BSR for D2D communication includes an LCID for identifying a short buffer status report for D2D communication unlike the BSR for cellular communication, an LCID for identifying a truncated buffer status report for D2D communication, and a long buffer status report for D2D communication The LCID identifying can be assigned.

Each MAC layer can be allocated a different SR resource corresponding to each BSR from the BS, and the different SR resource can operate in the same manner as the existing SR resource based on the BSR triggering condition. However, the configuration information for each SR can be configured independently of each other.

11 is a flowchart illustrating a method of allocating resources for inter-terminal communication according to an embodiment of the present invention.

Referring to FIG. 11, in a wireless communication system supporting D2D communication, a base station receives a BSR from a terminal (S1110), and determines whether D2D data exists in the terminal based on the received BSR (S1120). For example, the BS can confirm that the D2D data exists in the MS based on a case where the LCID included in the received BSR indicates a truncated BSR for the D2D. In addition, if the LCG ID included in the received BSR is a preset value for D2D, the BS can confirm that the buffer size information included in the BSR is the buffer size information for the D2D data.

If it is determined that there is data to be transmitted through the D2D communication, the BS can allocate resources for D2D communication to the MS (S1130).

12 is a block diagram illustrating a terminal and a base station according to an embodiment of the present invention.

12, a terminal 1200 includes a processor 1201 and a transmitting unit 1202, and a base station 1250 includes a receiving unit 1251 and a processor 1252. Here, the base station 1250 may be a cluster head.

The processor 1201 of the terminal can provide a user interface (UI) to the user of the terminal 1200 to set the terminal 1200 to enable D2D communication. When the D2D communication is enabled through the user interface, the terminal 1200 can perform D2D communication.

Alternatively, a user of the terminal 1200 may send a D2D (Proximity Service) ID of a terminal using D2D communication and a D2D server that manages a ProSe application ID, a serving base station of the terminal, etc.) It is possible to finally determine whether or not the D2D communication of the terminal 1200 set to enable communication is possible. That is, the terminal 1200 may perform terminal-to-terminal communication only when inter-terminal communication is permitted by the network even if the terminal 1200 is set to enable terminal-to-terminal communication. The terminal processor 1201 can display information on whether D2D communication is possible through a screen (not shown) of the terminal 1200. [

The terminal 1200 can process the D2D data and the uplink data in one MAC layer. The MAC layer for D2D communication and the MAC layer for cellular communication may exist independently of each other in the terminal 1200. [

When D2D communication is enabled in the terminal 1200, at least one RB for D2D communication and parameters related to the RB may be configured in the terminal 1200. [ The RB for the D2D communication may be mapped to at least one LC and LCG.

The LC for D2D communication can always be set to a fixed value, and the LCG for D2D communication can also be set to a fixed value. LCs for D2D communication can all be included in the same LCG, and the LCG value can be set to a fixed value and can be set by the base station. In this case, the base station 1250 may not separately notify the terminal 1200 of an LCG value including LCs for D2D communication. The LCG for D2D communication may not include the LCs corresponding to the RBs configured for wireless communication. The LC to be included in the LCG for the D2D communication can be set by the base station.

The UE 1200 may report the amount of D2D data and the amount of uplink data existing in the buffer to the BS 1250 through one BSR. At this time, the LCID as shown in Table 1 or Table 4 may be used for the BSR. In addition, the value of the buffer size field of the BSR can follow the configuration of Table 2, and when the extended BSR is configured, the configuration of Table 3 can be followed.

The processor 1201 of the terminal performs triggering of the BSR when there are two or more LCGs having data to be transmitted to the terminal 1200 and at least one of the LCGs has data to be transmitted in the D2D communication, And generates a truncated BSR based on the uplink resource amount allocated from the base station. Then, the transmitting unit 1202 transmits the truncated BSR to the base station in the format of the MAC control element.

For example, if the number of padding bits to be included in the MAC PDU is equal to or larger than the sum of the BSRs of the short BSR and the short BSR, the processor 1201 of the MS may be smaller than the sum of the long BSR and the long BSR subheader The LCG having the LC having the highest priority has the data to be transmitted in the uplink, and if there are two or more LCGs having the data to be transmitted in the uplink in the TTI to which the BSR is to be transmitted, And generate a buffer status report for the LCG including the LC having the highest priority.

Meanwhile, the processor 1201 of the UE may compare the length of the long BSR with the length of the long BSR when the number of padding bits included in the MAC PDU is equal to or larger than the sum of the short BSR and the short BSR , If there are two or more LCGs having data to be transmitted and at least one of the LCGs has data to be transmitted in the D2D communication, the LCID is set to the truncated BSR and the buffer status report for the LCG having the data to be transmitted in the D2D communication Can be generated. That is, when an LC having data to be transmitted through D2D communication exists in the terminal, it can always have a higher priority than an LC having data to be transmitted in the uplink. In this case, the truncated BSR includes buffer size information corresponding to LCG including LC having identification information (LCG ID) of LCG including LC having data to be transmitted through D2D communication and LC having data to be transmitted through D2D communication can do.

In addition, the processor 1201 of the UE may have a size equal to or larger than a sum of a BSR having a shorter number of padding bits included in the MAC PDU and a subheader of the shorter BSR, but smaller than a sum of a longer BSR and a subheader of the longer BSR , If there are two or more LCGs having data to be transmitted and at least one LCG of the LCG has data to be transmitted in the D2D communication, the LCID is set to the truncated BSR and the LC having the highest priority among the LCs having data to be transmitted in the uplink 0.0 &gt; LC &lt; / RTI &gt; In this case, the truncated BSR corresponds to the LCG including the LC having the highest priority among the LCs having the data to be transmitted in the uplink, and the LCG having the LC having the highest priority The size of the buffer. In this case, the transmitter 1202 transmits the truncated BSR to the base station in the format of the MAC control element, and based on Table 4 described above, identifies that the MAC control element is a truncated buffer status report for D2D communication The mobile station can inform the base station that there is an LCG having data to be transmitted through the D2D communication to the mobile station.

The receiving unit 1251 of the base station receives the BSR from the transmitting unit 1202 of the terminal 1200. Upon receiving the BSR in the receiver 1251, the processor 1252 of the base station checks whether data to be transmitted through the D2D communication exists in the terminal 1200 based on at least one of the LCID and the LCG ID in the BSR, And allocates resources for D2D communication to the terminal 1200 when it is confirmed that data to be transmitted exists.

In one example, when a short BSR or a truncated BSR is received, the BSR of the base station receives the BSG based on the LCG value of the LCG ID field included in the MAC control element of the short BSR or truncated BSR, (For example, LCG 1) among the buffer size information (buffer sizes # 1 to # 4) when the long BSR is received, (buffer size # 1) as buffer size information for D2D data. Further, when receiving the LCID for D2D, it can be recognized that data to be transmitted through the D2D communication exists in the terminal.

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 . 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 for transmitting a buffer status report by a terminal in a wireless communication system supporting D2D (Device to Device) communication,
Performing triggering of a buffer status report when at least one logical channel group (LCG: Logical Channel Group) having data to be transmitted exists and at least one of the LCGs has data to be transmitted through the D2D communication ;
Generating a trunked buffer status report based on the number of LCGs and an uplink resource amount allocated from a base station; And
Transmitting the truncated buffer status report to the base station in the format of a Media Access Control (MAC)
Lt; / RTI &gt;
The truncated buffer status report may include:
(LCG ID) including the logical channel having the highest priority among the logical channels having the data to be transmitted in the uplink and buffer size information corresponding to the LCG including the logical channel having the highest priority And transmitting the buffer status report. The method according to claim 1,
Further comprising the step of transmitting a Logical Channel ID (LCID) identifying the MAC control element to be a truncated buffer status report for D2D communication. The method according to claim 1,
The terminal,
Wherein the data to be transmitted in the D2D communication and the data to be transmitted in the uplink are processed in one MAC layer. The method according to claim 1,
The logical channel having the data to be transmitted through the D2D communication includes:
Wherein the buffer status report is set to a fixed value. The method according to claim 1,
The logical channel having the data to be transmitted through the D2D communication includes:
Are included in the same LCG set to fixed values. The method according to claim 1,
The terminal,
Wherein the D2D communication is performed when the user of the terminal is set to enable the D2D communication. The method according to claim 1,
The terminal,
Performing D2D communication when the D2D communication is permitted by a user of the terminal and D2D communication of the server managing the D2D communication or the terminal set to enable the D2D communication by the base station is permitted A buffer status report transmission method. A method for transmitting a buffer status report by a terminal in a wireless communication system supporting D2D (Device to Device) communication,
Performing triggering of a buffer status report when at least one logical channel group (LCG: Logical Channel Group) having data to be transmitted exists and at least one of the LCGs has data to be transmitted through the D2D communication ;
Generating a trunked buffer status report based on the number of LCGs and an uplink resource amount allocated from a base station; And
Transmitting the truncated buffer status report to the base station in the format of a Media Access Control (MAC)
Lt; / RTI &gt;
The truncated buffer status report may include:
(LCG ID) including a logical channel having data to be transmitted through the D2D communication and a logical channel having data to be transmitted through the D2D communication. How to send status reports. 9. The method of claim 8,
The terminal,
Wherein the data to be transmitted in the D2D communication and the data to be transmitted in the uplink are processed in one MAC layer. 9. The method of claim 8,
The logical channel in which the data to be transmitted through the D2D communication exists,
Wherein the buffer status report is set to a fixed value. 9. The method of claim 8,
The logical channel in which the data to be transmitted through the D2D communication exists,
Are included in the same LCG set to fixed values. A terminal for transmitting a buffer status report (Buffer Status Report) in a wireless communication system supporting D2D (Device to Device) communication,
If there are two or more logical channel groups (LCGs) having data to be transmitted and at least one of the LCGs has data to be transmitted in the D2D communication, if the triggering of the buffer status report is performed, And generating a trunked buffer status report based on the uplink resource amount allocated from the base station; And
And transmits the truncated buffer status report to the base station in the format of a Media Access Control (MAC)
Lt; / RTI &gt;
The processor comprising:
(LCG ID) including the logical channel having the highest priority among the logical channels having the data to be transmitted in the uplink and buffer size information corresponding to the LCG including the logical channel having the highest priority To generate the truncated buffer status report. A terminal for transmitting a buffer status report (Buffer Status Report) in a wireless communication system supporting D2D (Device to Device) communication,
If there are two or more logical channel groups (LCGs) having data to be transmitted and at least one of the LCGs has data to be transmitted in the D2D communication, if the triggering of the buffer status report is performed, And generating a trunked buffer status report based on the uplink resource amount allocated from the base station; And
And transmits the truncated buffer status report to the base station in the format of a Media Access Control (MAC)
Lt; / RTI &gt;
The processor comprising:
Generates the buffer status report using the buffer size information corresponding to the LCG including the identification information (LCG ID) of the LCG including the logical channel having the data to be transmitted through the D2D communication and the logical channel having the data to be transmitted through the D2D communication To the terminal. A resource allocation method for D2D communication by a base station in a wireless communication system supporting D2D (Device to Device) communication,
Receiving a buffer status report from a terminal;
Whether there is data to be transmitted in the D2D communication based on at least one of logical channel ID (LCID) and logical channel group ID (LCG ID) included in the buffer status report Checking whether or not it is acceptable; And
Allocating a resource for D2D communication to the terminal when it is determined that there is data to be transmitted through the D2D communication to the terminal;
/ RTI &gt; for a D2D communication.

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