KR102248331B1 - Method and apparatus for operating truncated buffer state report in wireless communication system supporting device to device communication - Google Patents

Abstract

A method and apparatus for operating a disconnected buffer status report in a wireless communication system supporting communication between terminals are provided. In a wireless communication system that supports device-to-device (D2D) communication, a method of operating a buffer state report (BSR) by a terminal is the step of receiving uplink resource allocation information from a base station, and a target for transmitting D2D data. It may include configuring a truncated BSR including buffer status information for at least one group according to the priority of each group, and transmitting the truncated BSR to the base station.

Description

A method and device for reporting the disconnected buffer status in a wireless communication system that supports communication between terminals {METHOD AND APPARATUS FOR OPERATING TRUNCATED BUFFER STATE REPORT IN WIRELESS COMMUNICATION SYSTEM SUPPORTING DEVICE TO DEVICE COMMUNICATION}

The present invention relates to wireless communication, and in particular, in a wireless communication system supporting device to device communication, when a method in which resources used for communication between terminals are controlled by a network is used, a truncated buffer status report is used. It relates to a method and apparatus for operating a (truncated buffer state report).

Device to Device (D2D) communication is a communication method that has been possible since the days of analog radios, and has a long history. However, D2D communication in a wireless communication system is differentiated from existing D2D communication. D2D communication in a wireless communication system is a communication in which terminals geographically close to each other use the transmission/reception technology of the wireless communication system in the frequency band of the wireless communication system or in a band other than that of the wireless communication system, but directly exchange data without going through an infrastructure such as a base station. Means. This allows the terminal to use wireless communication outside the area where the wireless communication infrastructure is established, and provides an advantage of reducing the network load of the wireless communication system.

For inter-terminal communication in such a wireless communication system, the base station provides resources necessary for terminals existing in coverage to transmit data through a sidelink defined as an inter-terminal interface for D2D communication. Can be scheduled. To this end, the terminal may inform the base station of how much of the amount of data to be transmitted through the sidelink exists in the buffer in the terminal through a buffer state report (BSR). At this time, when the UE is not sufficient to send the buffer status information generated based on the amount of data that can be transmitted to all targets for which the UE intends to perform D2D communication through the sidelink, the uplink resource allocated from the base station is insufficient. , Transmitting a truncated BSR including information on at least one or more of the targets for D2D communication through the sidelink, but not all targets, but only some targets. However, in the BSR for D2D communication, the priority to be included in the uplink resource is set lower than the BSR for wireless communication between the terminal and the base station and a power headroom report (PHR). For this reason, the amount of uplink resources required for BSR transmission for D2D communication by the base station may be less than the amount of uplink resources required for BSR transmission for D2D communication determined by information generated by the UE and priority. Therefore, a case in which the uplink resource allocated from the base station is not sufficient to send the BSR for D2D communication may occur continuously, and thus, the situation of transmitting the BSR for the truncated form of D2D communication will occur continuously. I can. If the BSR operation method that does not take this case into account is applied to D2D communication, there is a problem in that buffer status information for a specific target cannot be continuously transmitted.

An object of the present invention is to provide a method and apparatus for operating a truncated buffer status report in a wireless communication system supporting communication between terminals.

According to an aspect of the present invention, a method of operating a buffer state report (BSR) by a terminal in a wireless communication system supporting device-to-device (D2D) communication receives uplink resource allocation information from a base station. The steps of, configuring a truncated BSR including buffer status information for at least one group according to the priority of each group to which the D2D data is to be transmitted, and transmitting the truncated BSR to the base station. Can include.

According to another aspect of the present invention, a method of operating a buffer status report by a base station in a wireless communication system supporting communication between terminals includes transmitting uplink resource allocation information to a terminal, and for each group of targets to transmit D2D data from the terminal. Receiving a truncated BSR including buffer status information for at least one group according to the priority, recognizing the priority of each group to which the D2D data set in the terminal is transmitted based on the truncated BSR, and It may include the step of allocating resources for D2D communication to the terminal.

According to the present invention, a terminal or a base station that allocates resources for communication between terminals in a wireless communication system can efficiently receive information on a buffer state.

1 is a diagram showing a wireless communication system to which the present invention is applied.
2 is a diagram illustrating an example of a MAC sub-header in a wireless communication system.
3 is a diagram illustrating a MAC control element of a buffer status report in a wireless communication system.
4 is a diagram for explaining the concept of D2D communication based on a cellular network applied to the present invention.
5 is a diagram showing a format of a ProSe-BSR according to an embodiment of the present invention.
6 is a diagram illustrating a truncated ProSe-BSR transmission method according to an embodiment of the present invention.
7 is a diagram illustrating a truncated ProSe-BSR transmission method according to another embodiment of the present invention.
8 is a diagram illustrating a method of operating a truncated ProSe-BSR by a terminal according to an embodiment of the present invention.
9 is a diagram illustrating a method of operating a truncated ProSe-BSR by a base station according to an embodiment of the present invention.
10 is a block diagram showing a wireless communication system according to an embodiment of the present invention.

Hereinafter, in the present specification, contents related to the present invention will be described in detail through exemplary drawings and embodiments along with the contents of the present invention. In adding reference numerals to constituent elements in each drawing, it should be noted that the same constituent elements are given the same reference numerals as much as possible even if they are indicated on different drawings. In addition, in describing an embodiment of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present specification, a detailed description thereof will be omitted.

In addition, this specification describes a wireless communication network, and operations performed in the wireless communication network are performed in the process of controlling the network and transmitting data in a system (for example, a base station) in charge of the wireless communication network, or The operation may be performed at a terminal included in the network.

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

The network structure shown in FIG. 1 may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may include a Long Term Evolution (LTE), an LTE-A (advanced) system, and the like.

Referring to FIG. 1, in a wireless communication system 10, a base station (BS) 11 and a user equipment (UE) 12 may transmit and receive data wirelessly. In addition, the wireless communication system 10 may support device-to-device (D2D) communication. A wireless communication system supporting D2D communication will be described later.

In the wireless communication system 10, the base station 11 may provide a communication service to a terminal existing within the transmission coverage of the base station through a specific frequency band. The coverage serviced by the base station may also be expressed in terms of a site. The site may include a plurality of areas 15a, 15b, and 15c, which may be referred to as sectors. Each of the sectors included in the site may be identified based on a different identifier. Each of the sectors 15a, 15b, and 15c may be interpreted as a partial area covered by the base station 11.

Base station 11 generally refers to a station communicating with the terminal 12, eNodeB (evolved-NodeB), BTS (Base Transceiver System), access point (Access Point), femto base station (Femto eNodeB), in-home A base station (HeNodeB: Home eNodeB), a relay (relay), a remote radio head (RRH: Remote Radio Head) may be referred to as other terms.

The terminal 12 may be fixed or mobile, and may be a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, or a personal digital assistant (PDA). , Wireless modem, handheld device, etc. may be referred to as other terms.

The base station 11 may be referred to in various terms such as a mega cell, a macro cell, a micro cell, a pico cell, and a femto cell, depending on the size of coverage provided by the corresponding base station. The cell may be used as a term indicating a frequency band provided by a base station, coverage of a base station, or a base station.

Hereinafter, downlink refers to a communication or communication path from the base station 11 to the terminal 12, and uplink refers to a communication or communication path from the terminal 12 to the base station 11 do. In downlink, the transmitter may be a part of the base station 11 and the receiver may be a part of the terminal 12. In the uplink, the transmitter may be a part of the terminal 12 and the receiver may be a part of the base station 11.

Meanwhile, there is no limitation on a multiple access technique applied to the wireless communication system 10. For example, Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA (SC-FDMA), OFDM-FDMA , OFDM-TDMA, OFDM-CDMA, such as various multiple access techniques can be used. In addition, for uplink transmission and downlink transmission, a time division duplex (TDD) scheme transmitted using different times or a frequency division duplex (FDD) scheme transmitted using different frequencies may be used.

2 is a diagram illustrating an example of a MAC sub-header in a wireless communication system, and FIG. 3 is a diagram illustrating a MAC control element of a buffer status report. Hereinafter, a buffer state report (BSR) transmitted by the terminal to the base station for uplink transmission will be described with reference to FIGS. 2 and 3.

Layers of the radio interface protocol between the terminal and the network are the first layer (L1) and the second layer defined in the 3rd Generation Partnership Project (3GPP) series of wireless communication systems (UMTS, LTE, LTE-Advanced, etc.) It can be divided into (L2) and a third layer (L3).

The physical layer belonging to the first layer (L1) provides an information transfer service to the upper layer, the media access control (MAC) layer, using a physical channel, and the third layer The Radio Resource Control (RRC) layer located at controls radio resources between the terminal and the network by exchanging RRC messages. The MAC layer is a mapping between a logical channel (LC) and a transport channel, and multiplexing or demultiplexing into a transport block provided as a physical channel on a transport channel of a MAC Service Data Unit (SDU) belonging to the logical channel. You can do it.

The base station controls the BSR procedure for a logical channel within each terminal through signaling defined in the RRC layer. In this case, a logical channel group (LCG) may be configured through selective signaling, and BSR may be performed for the LCG. In other words, in the wireless communication system, the terminal may configure the BSR based on data buffered in each LCG in the terminal. A maximum of 4 LCGs may be configured in the terminal.

The format of the BSR includes a short BSR for reporting the buffer status corresponding to one LCG, a long BSR for reporting the buffer status corresponding to four LCGs, and a truncated BSR. In addition, the BSR may be classified into a regular BSR (BSR), a padding BSR (Padding BSR), and a periodic BSR (BSR).

General BSR triggers when there is uplink data that can be transmitted in a logical channel included in the LCG, or when there is uplink data that can be transmitted in a logical channel that has a higher priority than other logical channels that already have transmittable data. (triggering). The padding BSR is triggered when uplink resources are allocated and the number of padding bits is equal to or larger than the size for BSR transmission. The periodic BSR is triggered when the periodic BSR-Timer has expired.

Normal BSR and periodic BSR are transmitted in a long BSR format when more than one LCG (at least two or more LCGs) have data to be transmitted in a transmission time interval (TTI) in which the corresponding BSR is transmitted, and otherwise (one If only the LCG of has data to be transmitted), it is transmitted in a short BSR format. The padding BSR is equal to or larger than the sum of the short BSR and the subheader of the short BSR with the number of padding bits included in the MAC PDU (Protocol Data Unit), but is smaller than the combined size of the long BSR and the subheader of the long BSR, and corresponds to When more than one LCG has data to be transmitted in the TTI in which the BSR is transmitted, the LCG including the logical channel having the highest priority for data transmission is transmitted in the truncated BSR format. In other cases, that is, when the corresponding BSR is transmitted for one LCG in the transmitted TTI, it is transmitted in a short BSR format. Meanwhile, the padding BSR is transmitted in a long BSR format when the number of padding bits is equal to or larger than the sum of the long BSR and the subheader of the long BSR.

These BSRs are included in the MAC PDU and transmitted to the base station, and one MAC PDU includes only one MAC control element even if multiple BSRs are triggered. Here, the MAC PDU may include a MAC header, a MAC control element, a MAC Service Data Unit (SDU), and padding. The MAC header includes at least one subheader, and each subheader corresponds to a MAC control element, MAC SDU, or padding, respectively. The MAC sub-header includes six fields (R, R, E, LCID, F, L) as shown in Figs. 2(a) and 2(b), or as shown in Fig. 2(c). It includes four fields (R, R, E, LCID).

The logical channel identification information (LCID: Logical Channel ID) field is a field that identifies a logical channel of a corresponding MAC SDU or a corresponding MAC control element or a type of padding, and the length (L: Length) field is a corresponding field. This field identifies the length of the MAC SDU or the length of a variable-sized MAC control element. The F field is a field that identifies the length of the L field, the E: Extension field is a field that identifies whether other fields exist in the MAC header, and the R (Reserved) field is a reserved field and is set to "0". do.

Referring to FIG. 3(a), the MAC control element of a short BSR and a truncated BSR consists of one LCG ID field and one corresponding buffer size (BS) field. And, referring to FIG. 3(b), the MAC control element of a long BSR consists of four buffer size fields corresponding to four LCG IDs (#0 LCG ID to #3 LCD ID). The format of the BSR is identified by the value of the logical channel identifier (LCID) included in the sub-header of the MAC PDU. As an example, LCID values for 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

In Figure 3(a), the LCG ID field is for identifying the logical channel group in which the buffer status is reported to the base station, and the buffer size field is used in all logical channels in the LCG after all MAC PDUs to be transmitted during one TTI are constructed. To identify the total amount of data available.

4 is a diagram for explaining the concept of D2D communication based on a cellular network applied to the present invention.

D2D communication may refer to a technology for directly transmitting and receiving data between terminals. Hereinafter, in an embodiment of the present invention, it is assumed that the terminal supports D2D communication. In addition, D2D may be replaced by a proximity-based service (Proximity based Service, hereinafter referred to as ProSe) or an expression called ProSe-D2D. The use of the term ProSe for D2D means that the meaning of directly transmitting and receiving data between terminals is not changed, but that the meaning of a proximity-based service can be added. In addition, the radio interface between terminals in which the D2D communication is performed is defined as a sidelink.

Recently, a method of performing discovery and direct communication between devices in network coverage (in-coverage) or out-of-coverage (out-of-coverage) for the purpose of public safety, etc. It is being studied. A terminal that transmits a signal based on communication between terminals may be referred to as a transmitting terminal (Tx UE), and a terminal that receives a signal based on communication between terminals may be defined as a receiving terminal (Rx UE). The transmitting terminal may transmit a discovery signal, and the receiving terminal may receive the discovery signal. The roles of the transmitting terminal and the receiving terminal may be changed. The signal transmitted by the transmitting terminal may be received by two or more receiving terminals.

In a cellular system, when terminals in close proximity perform D2D communication, the load of the base station may be distributed. In addition, when adjacent terminals perform D2D communication, the terminals transmit data over a relatively short distance, and thus the consumption of transmission power and transmission delay of the terminal may be reduced. In addition, from the perspective of the entire system, since the existing cellular-based communication and D2D communication use the same resource, the frequency utilization efficiency can be improved.

D2D communication can be divided into a communication method of a terminal located in network coverage (in-coverage) and a communication method of a terminal located out of network coverage (out-of-coverage). In FIG. 4, communication between a first terminal 410 located in a first cell and a second terminal 420 located in a second cell, a third terminal 430 located in a first cell and a fourth terminal located in a first cluster Communication between 440 may be D2D communication within network coverage. Communication between the fourth terminal 440 located in the first cluster and the fifth terminal 450 located in the first cluster may be D2D communication outside of network coverage. Here, the fifth terminal 450 may operate as a cluster head (CH) of the first cluster. Here, the cluster head means a terminal in charge of allocating resources. The cluster header may include an independent synchronization source (ISS) for synchronization of a terminal located outside of network coverage.

D2D communication may be divided into a discovery procedure for performing discovery for communication between terminals and a direct communication procedure for transmitting and receiving control data and/or traffic data between terminals. D2D communication can be used for various purposes. For example, D2D communication within a network coverage based on a commercial frequency can be used for public safety, ultra-low latency services, commercial services, and the like. If it can be determined that the terminal is out of the network coverage based on the commercial frequency, for example, the signal strength received from all base stations is less than a predetermined threshold value stored in the terminal and predefined in the wireless communication system for a predetermined time or longer. If maintained for a while, D2D communication can be used only for public safety. However, in the case of based on a frequency for public safety, D2D communication can be used only for public safety regardless of network coverage.

As an embodiment of performing D2D communication, the base station 400 may transmit D2D resource allocation information to the first terminal 410. The first terminal 410 is a terminal located within the coverage of the base station 400. The D2D resource allocation information may include allocation information for transmission resources and/or reception resources that can be used for D2D communication between the first terminal 410 and another terminal, that is, the second terminal 420.

Upon receiving the D2D resource allocation information from the base station, the first terminal 410 may transmit the D2D resource allocation information to the second terminal 420. The second terminal 420 may be a terminal located outside the coverage of the base station 400. The first terminal 410 and the second terminal 420 may perform D2D communication based on D2D resource allocation information. Specifically, the second terminal 420 may acquire information on the D2D communication resource of the first terminal 410. The second terminal 420 may receive data transmitted from the first terminal 410 through a resource indicated by information on the D2D communication resource of the first terminal 410.

On the other hand, a terminal that supports D2D communication (hereinafter referred to as a D2D terminal) connects to the D2D management server and successfully completes the D2D operation authentication procedure and is assigned an identifier (ID)(s) to be used for D2D operation. You can do it. The identifiers may include a source ID of the terminal, a destination ID for a group in which the terminal is included, and a destination ID for another group through which the terminal can perform D2D communication. In addition, the D2D terminal may perform D2D communication when the user of the corresponding terminal configures the corresponding terminal to enable D2D communication through a user interface (UI). If the D2D terminal is located within a cellular service area, that is, when it can receive and recognize a signal transmitted by the base station for cellular service, the base station is assigned an ID(s) to be used during D2D operation and is configured to enable D2D communication. D2D communication can be performed only when a message including information allowing D2D operation is transmitted. Here, the information allowing the D2D operation may be defined as whether a system information block (SIB) including configuration information for each of communication and discovery during the D2D operation is transmitted from the base station.

Resources for D2D communication may be allocated by a terminal (hereinafter, a cluster head) or a base station in charge of allocating resources for D2D communication during D2D communication. In this case, when performing D2D communication, the UE must transmit a BSR for D2D data to the base station or the cluster head. Hereinafter, for convenience of description, the base station and the cluster head are collectively referred to as a base station. In addition, the BSR for D2D data is referred to as ProSe-BSR. In addition, the cellular network can be replaced by the term WAN (Wide Area Network). The ProSe-BSR uses an LCID different from the LCIDs assigned to the BSR for the WAN.

Meanwhile, during D2D communication, the terminal may operate in a first transmission mode and a second transmission mode. The first transmission mode is a mode in which D2D communication can be performed only when the terminal is allocated resources for D2D communication from the base station, and the base station transmits a D2D grant to the transmitting terminal. The D2D grant is based on parameter information to be determined by a base station among control information to be secured for D2D data reception by a receiving terminal during D2D communication, resource allocation information for the SA, and the SA. Resource allocation information for the indicated data is instructed to the transmitting terminal. The parameter information to be determined by the base station includes resource allocation information for data indicated by the SA. The D2D grant is delivered to a transmitting terminal through downlink control information (DCI), and the DCI may be delivered through a physical downlink control channel (PDCCH) or an extended PDCCH (EPDCCH). Here, the D2D grant may be referred to as a sidelink grant (SL grant).

On the other hand, the second transmission mode is a mode in which the terminal can perform D2D communication regardless of the instruction of the base station, and the terminal can use radio resources (e.g., time, frequency, space, etc.) as the second transmission mode during D2D communication. ), D2D data can be transmitted by internally selecting a resource to be used. The UE has information indicating that a specific cell in the base station can support D2D through SIB (System Information Block)/dedicated signaling and D2D resource pool information for a second transmission mode provided from the base station. Only when present, the specific cell can operate in the second transmission mode. However, if the base station does not allow operation in the second transmission mode, that is, information indicating that a specific cell in the base station can support D2D is present, D2D resource pool information for the second transmission mode is provided from the base station. If not, the terminal cannot operate in the second transmission mode.

However, if the terminal is located in a non-network service area, the D2D resource pool information for the second transmission mode stored in the UICC (Universal Subscriber Identity Module (USIM) Integrated Circuit Card) of the terminal is used, or the previous network It is possible to operate in the second transmission mode by using the D2D resource pool information for the second transmission mode received through the base station in the service area.

When operating in the first transmission mode, the D2D terminal may inform the base station of how much data to be transmitted through D2D communication exists in the buffer through the following ProSe-BSR.

5 is a diagram showing a format of a ProSe-BSR according to an embodiment of the present invention.

The BSR cut from the WAN contains only information on one LCG with the highest priority. In terms of QoS (Quality of Service), the information on the LCG set as the highest priority by the base station is the information the base station needs most, and the base station knows that there is uplink data for other LCGs in addition to the corresponding LCG. This is to do. This is because the truncated BSR could only be generated by the padding BSR, so the base station can know the amount of uplink resources including the BSR for all LCGs through the general or periodic BSR included in the uplink transmission data transmitted to the corresponding TTI. Because there was. This is because the transmission priority of the general/periodic BSR has the highest priority except for data including C-RNTI and information on a common control channel (CCCH). However, the ProSe-BSR may include information on a destination capable of transmitting ProSe data through a sidelink, apart from information on the LCG. The object may be composed of one or more terminals. Therefore, it is defined as a group destination. Hereinafter, for simplification of the name, the group object is referred to as a'group'.

FIG. 5 shows, as an example, a MAC control element of the ProSe-BSR. The ProSe-BSR MAC control element is configured as shown in FIG. 5(a) when the number of groups (N) included in the ProSe-BSR is an even number, and configured as shown in FIG. 5(b) when the number is odd. When the number of groups included in the ProSe-BSR is odd, four reserved bits may be included. Here, the group index is a value for identifying a group (ProSe destination group) to which ProSe data is to be transmitted, and has a length of 4 bits. This value is set as the index of the destination ID reported by the terminal in RRC signaling. For example, when the terminal transmits a ProSe destination information list (ProseDestinationInfoList) including a ProSe destination ID having a length of 24 bits to the base station, the base station has a group index of 0 in the order listed (e.g., in descending order). It is interpreted as being mapped from up to 15. The LCG ID is to identify the logical channel group for which the buffer status is reported to the base station, and the buffer size field is the total of data available in all logical channels in the LCG after all MAC PDUs to be transmitted during one TTI are constructed. To discern sheep.

Meanwhile, in the ProSe-BSR, the priority included in the uplink resource is set after the BSR for the WAN. Therefore, if there are multiple groups when transmitting ProSe-BSR (IDs for up to 16 groups can be configured), and the uplink resource allocation for the WAN is not sufficient to send the ProSe-BSR, the truncated form A situation in which ProSe-BSR is continuously transmitted may occur. This is because the priority to be included in the uplink resource of ProSe-BSR is following information indicating the Cell Radio-Network Temporary Identifier (C-RNTI), Common Control Channel (CCCH) information, BSR for WAN, and PHR information for WAN. This is because, when such information occurs, uplink resources are first allocated to them. In addition, there may be a case where the maximum amount of resources that can be allocated by the scheduler is limited according to the uplink load condition of the corresponding serving cell.

For this reason, there may be a case in which the amount of uplink resources allocated to the terminal cannot continuously include all ProSe-BSR information. Therefore, since the truncated ProSe-BSR can be continuously configured and transmitted, there is a problem that information on a specific target may not be continuously transmitted if the buffer status information for as many targets as possible is simply included in the ProSe-BSR. . Accordingly, in the present specification, a truncated ProSe-BSR transmission method in consideration of equity and priority for each ProSe group is provided as in the following embodiments.

6 is a diagram illustrating a truncated ProSe-BSR transmission method according to an embodiment of the present invention.

As an embodiment, the priority of buffer status information for groups to be included in the ProSe-BSR by the UE may be the same for all groups. In other words, all groups may be included in the ProSe-BSR with the same priority. Whether the terminal includes buffer status information for which group is included in the initially truncated ProSe-BSR is a priority set based on the QoS parameters of the data contained in each group or other criteria such as D2D transmission priority for each group set by the terminal. Can be determined. However, in this case, if the ProSe-BSR to be transmitted immediately next after the immediately truncated ProSe-BSR is transmitted is the truncated ProSe-BSR, the UE selects the group to be included in the truncated ProSe-BSR to be transmitted next. At least one or more groups not included in the truncated ProSe-BSR transmitted immediately before may be included first. If all groups not included in the truncated ProSe-BSR transmitted immediately before are included, but the remaining uplink resources may include buffer status information for the additional group, the truncated ProSe-BSR that was transmitted previously Buffer status information for the included group may be additionally included.

As an example, referring to FIG. 6, a case in which N groups are configured in a terminal is illustrated. 6, when information on the buffer status of m groups is transmitted through the first truncated ProSe-BSR (Truncated ProSe-BSR #1), immediately after the first truncated ProSe-BSR is transmitted Next, when the second truncated ProSe-BSR (Truncated ProSe-BSR #2) is transmitted, the group corresponding to the buffer status information from m+1 to N is more than the group corresponding to the previously transmitted m buffer status information. It can have a high priority. Therefore, if the second truncated ProSe-BSR can include buffer status information for k groups, the second truncated ProSe-BSR includes buffer status information for groups ranging from m+1 to m+k. May be included. Here, the m, k, and N values are not related to the group index and refer to the number of groups arbitrarily set for explanation. To this end, when configuring the truncated ProSe-BSR, the terminal can check whether the truncated ProSe-BSR has been transmitted immediately before. If the truncated ProSe-BSR that was truncated immediately before is transmitted, the priority may be increased so that a group not included in the immediately truncated ProSe-BSR is included in the truncated ProSe-BSR to be transmitted this time.

7 is a diagram illustrating a truncated ProSe-BSR transmission method according to another embodiment of the present invention.

As another embodiment, the priority to be included in the ProSe-BSR may be set by the UE for sidelink resource allocation or may be determined according to a group priority determined by a destination ID value. Here, the priority for each group for the sidelink resource allocation may be directly set by the terminal or may be set based on the priority for each LCG. As an example, when the priority for inclusion in the ProSe-BSR is set based on the priority for each LCG, the group #1 corresponding to the LCG including the LC having the highest priority and the third priority has a second priority. Branches may be included in the ProSe-BSR with a higher priority than group #2 for the LCG including the LC. Here, the priority for each group determined by the destination ID value may be set to have a higher priority as the destination ID value decreases, and the D2D-related application program in the terminal communicating with the D2D authentication server The priority for each group for sidelink resource allocation may be determined according to the priority set based on the information received through the application program according to the priority for each destination ID set by the application program.

In this case, if the ProSe-BSR to be transmitted immediately next after the immediately truncated ProSe-BSR is transmitted is the truncated ProSe-BSR, the group to be included in the truncated ProSe-BSR to be transmitted next is the current ProSe-BSR. At this point, the group having the highest priority to be included in the ProSe-BSR is preferentially included in the truncated ProSe-BSR to be transmitted next, regardless of whether it is included in the truncated ProSe-BSR transmitted immediately before, and then transmitted immediately before the above. Groups not included in the truncated ProSe-BSR may be included in the truncated ProSe-BSR to be transmitted next.

For example, FIG. 7 illustrates a case in which information on buffer states of m groups is transmitted through a first truncated ProSe-BSR (Truncated ProSe-BSR #1). As shown in FIG. 7, the index of the group having the highest priority at the _{time point (T 1} ) at which the first truncated ProSe-BSR (Truncated ProSe-BSR #1) is generated is A, and the first truncated ProSe-BSR If m number of buffer status information can be included in the first truncated ProSe-BSR, the buffer status information for the group index A may be preferentially included and transmitted.

Thereafter, when a situation in which the second truncated ProSe-BSR (Truncated ProSe-BSR #2) is transmitted at the next time point (T _{2) after the first truncated ProSe-BSR is transmitted occurs, it has the highest priority.} If the group index is B and the buffer status information for the group index B is p, and k buffer status information can be included in the second truncated ProSe-BSR, the second truncated ProSe-BSR contains the current ProSe- At the time when the BSR is generated (T ₂ ), p buffer status information for the group index B having the highest priority is included first, and then kp buffers for groups not included in the first truncated ProSe-BSR State information may be included in the second truncated ProSe-BSR.

In this case, when configuring the truncated ProSe-BSR, the terminal checks whether the truncated ProSe-BSR has been transmitted immediately before, and if the truncated ProSe-BSR has been transmitted immediately before, the terminal has the highest priority at the current point in time. While the buffer status information for the next transmitted ProSe-BSR is firstly included in the truncated ProSe-BSR, the priority of the group not included in the immediately truncated ProSe-BSR other than the highest priority group may be adjusted upward.

Meanwhile, as another embodiment, the priority to be included in the ProSe-BSR may be determined according to a ProSe-BSR priority allocation value based on a group priority for ProSe resource allocation. Here, the priority for each group for the ProSe resource allocation may be set as a quantitative parameter. The ProSe-BSR priority allocation value adjusted by the quantitative parameter does not affect the priority of each group for the ProSe resource allocation. The priority for each group for the ProSe resource allocation may be directly set by the terminal or may be set based on the priority for each LCG. For example, the quantitative parameter may have a range of 1 to x. Where x is a positive integer. For example, x may be 4, 8, or 16. The ProSe-BSR priority allocation value may be adjusted to a value of -y when the truncated ProSe-BSR is included. Here, the y value is a natural number and is always smaller than x.

In this case, when configuring the truncated ProSe-BSR, the terminal checks whether the truncated ProSe-BSR has been transmitted immediately before, and if the truncated ProSe-BSR has been transmitted immediately before, the truncated ProSe-BSR transmitted immediately before the truncated ProSe-BSR is transmitted. The priority for the group included in the BSR may be lowered by the ProSe-BSR priority allocation value. That is, the priority for the group included in the truncated ProSe-BSR transmitted immediately before can be adjusted down.

On the other hand, as another embodiment, the priority to be included in the general/periodic ProSe-BSR is based on the time when the transmittable data for each group is generated by the terminal or in a random manner or for the aforementioned ProSe resource allocation. Although this may be determined according to the directly set or destination ID-based priority for each group, the priority for inclusion in the truncated ProSe-BSR must be set based on the priority for each group for ProSe resource allocation. Because, in the case of transmitting a truncated ProSe-BSR that does not include buffer status information for all groups, the quality of service and the urgency of D2D communication by transmitting the buffer status information for the group that the UE wants to transmit first in D2D communication to the base station. Because it can meet. Accordingly, since the base station does not have information on the priority of each group of the terminal, the base station can recognize the priority of each group set by the terminal according to the order of group information included in the truncated ProSe-BSR.

8 is a diagram illustrating a method of operating a truncated ProSe-BSR by a terminal according to an embodiment of the present invention.

In a wireless communication system supporting D2D communication, the D2D terminal may transmit a list of identifiers of targets for transmitting D2D data to the base station using an RRC message when operating in the first transmission mode. Thereafter, as shown in FIG. 8, when the D2D terminal receives the uplink resource allocation information from the base station through the D2D grant (S810), the uplink resource allocated through the uplink resource allocation information is all targets for transmitting D2D data. When it is difficult to report the buffer status information for D2D data, a truncated ProSe-BSR including buffer status information for at least one group is configured according to the priority of each group to which the D2D data is to be transmitted (S820), and the D2D data is transmitted. The priority of each group of the target is readjusted (S830). Then, the configured truncated ProSe-BSR is transmitted to the base station. Here, the step of re-adjusting the priority of each group to which the D2D data is to be transmitted is shown to be performed after the truncated ProSe-BSR is configured, but if the truncated ProSe-BSR is triggered as necessary, the truncated ProSe-BSR It may be performed when it is confirmed that a situation in which the generated ProSe-BSR is continuously generated has occurred.

In order to adjust the priority for each group of targets to transmit D2D data, the D2D terminal may, for example, check whether the format of the BSR transmitted immediately before the configuration of the truncated ProSe-BSR is a truncated ProSe-BSR. If the format of the ProSe-BSR transmitted immediately before the configuration of the truncated BSR is the truncated ProSe-BSR, the D2D terminal may adjust the priority for each group of the target to which the D2D data is transmitted.

For example, the D2D terminal increases the priority of a group not included in the truncated ProSe-BSR transmitted immediately before, so that the group not included in the truncated ProSe-BSR transmitted immediately before is preferentially transmitted at this time. It can be included in the ProSe-BSR. Alternatively, the priority of the group included in the truncated ProSe-BSR transmitted immediately before is down-adjusted, so that the group not included in the truncated ProSe-BSR transmitted immediately before is preferentially assigned to the truncated ProSe-BSR to be transmitted this time. Can be included. In this case, a group having the highest priority among the groups to which the D2D data is to be transmitted may be included in the first truncated BSR. In this case, the priority for including each group in the truncated BSR may be determined according to the priority for each group for ProSe resource allocation. The priority for each group for the ProSe resource allocation may be directly set by the D2D terminal or may be set based on the priority for each LCG set by the base station. Alternatively, it may be set based on the priority of each group determined by the destination ID value. Here, the priority for each group for the ProSe resource allocation may be set as a quantitative parameter. When the priority of each group for the ProSe resource allocation is directly set by the D2D terminal, the priority of each group to be included in the truncated ProSe-BSR depends on whether or not it is included in the transmitted ProSe-BSR transmitted immediately before. May not be affected accordingly. In this case, the base station may recognize the priority between groups set by the terminal according to the order of the groups included in the truncated ProSe-BSR transmitted by the D2D terminal.

9 is a diagram illustrating a method of operating a truncated ProSe-BSR by a base station according to an embodiment of the present invention.

Hereinafter, the operation of the base station will be described with reference to FIG. 9 in the case where the priority for inclusion in the truncated ProSe-BSR is determined by the terminal in which the target group to transmit D2D data is determined. In this case, the priority for the group to be included in the truncated ProSe-BSR may not be affected depending on whether it is included in the truncated ProSe-BSR. That is, the priority to be included in the truncated ProSe-BSR may not be adjusted depending on whether it is included in the truncated ProSe-BSR.

Referring to FIG. 9, in a wireless communication system supporting D2D communication, a base station may receive a list of an identifier of a target to transmit D2D data from a D2D terminal through an RRC message (S910). Thereafter, the base station may transmit uplink resource allocation information to the D2D terminal through the D2D grant (S920), and according to the priority of each group of targets to transmit D2D data based on the uplink resource allocation information from the D2D terminal. The configured truncated BSR may be received (S930). Based on the truncated BSR, the base station may recognize the priority for each group of targets to transmit D2D data set in the D2D terminal (S940), and accordingly, allocate resources for D2D communication to the D2D terminal (S950). ).

10 is a block diagram showing a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 10, a wireless communication system supporting communication between terminals according to the present invention includes a terminal 1000 and a base station (or cluster head) 1100.

The terminal 1000 includes a processor 1010, a radio frequency (RF) unit 1020, and a memory 1030. The memory 1030 is connected to the processor 1010 and stores various information for driving the processor 1010. The RF unit 1020 is connected to the processor 1010 and transmits and/or receives a radio signal. For example, the RF unit 1020 may receive D2D resource allocation information posted in this specification from the base station 1100. In addition, the RF unit 1020 may transmit an uplink signal such as the truncated ProSe-BSR published in this specification to the base station 1100.

The processor 1010 implements the functions, processes and/or methods proposed in this specification. Specifically, the processor 1005 allows all steps according to FIGS. 6 to 8 to be performed.

For example, the processor 1010 may include a determination unit 1011 and a configuration unit 1012. The determination unit 1011 may determine whether the truncated ProSe-BSR is continuously configured or transmitted. To this end, when the truncated BSR is configured, the determination unit 1011 may check whether the format of the ProSe-BSR transmitted immediately before is the truncated ProSe-BSR. The configuration unit 1012 configures the truncated ProSe-BSR including buffer status information for at least one group according to the priority of each group to which the D2D data is to be transmitted. For example, when it is determined that the ProSe-BSR truncated by the determination unit 1011 is continuously transmitted, the configuration unit 1012 prioritizes the group not included in the truncated ProSe-BSR transmitted immediately before. By upward adjustment, a group not included in the truncated ProSe-BSR transmitted immediately before may be preferentially included in the truncated ProSe-BSR to be transmitted this time. Alternatively, the priority of the group included in the truncated ProSe-BSR transmitted immediately before is down-adjusted, so that the group not included in the truncated ProSe-BSR transmitted immediately before is preferentially assigned to the truncated ProSe-BSR to be transmitted this time. Can be included.

In addition, in a situation in which the truncated ProSe-BSR is continuously transmitted, the configuration unit 1012 may make a group having the highest priority among the groups to which the D2D data is to be transmitted is preferentially included in the truncated ProSe-BSR. . In this case, the priority for including each group in the truncated ProSe-BSR may be determined according to the priority for each group for ProSe resource allocation. The priority for each group for the ProSe resource allocation may be directly set by the D2D terminal, may be set based on a priority for each LCG set by the base station, or may be set based on a destination ID. Here, the priority of each group for the ProSe resource allocation may be adjusted by a quantitative parameter.

For example, the determination unit 1011 may include a transmission time determination unit and a priority determination unit. If it is determined that the information on the buffer status of m groups has been transmitted through the first truncated ProSe-BSR at the first point in time, the transmission point determination unit At point 2, it may be determined whether the second truncated ProSe-BSR is transmitted. When the second truncated ProSe-BSR is transmitted at the second point in time, the priority determination unit corresponds to the m number of buffer status information transmitted at the first point in time. It can be determined that it has a higher priority than the group. In this case, if the second truncated ProSe-BSR can include k buffer status information, the configuration unit 1012 is a group in which the second truncated ProSe-BSR is in the range m+1 to m+k. It can be configured to include buffer status information for. In addition, the configuration unit 1012 may be configured to preferentially include buffer state information for a group having the highest priority at the time when the second truncated ProSe-BSR is configured.

The memory 1030 may store uplink resource information and information on a truncated ProSe-BSR according to the present specification, and provide the same to the processor 1010 according to the request of the processor 1010.

The base station 1100 includes a radio frequency (RF) unit 1110, a processor 1120, and a memory 1130. The memory 1130 is connected to the processor 1120 and stores various information for driving the processor 1120. The RF unit 1130 is connected to the processor 1120 and transmits and/or receives a radio signal. The processor 1120 implements the functions, processes, and/or methods proposed in this specification. In the above-described embodiment, the operation of the base station 1100 may be implemented by the processor 1120. The processor 1120 generates the D2D grant published in this specification, and schedules resources for D2D communication based on the truncated ProSe-BSR received from the terminal 1000.

For example, the processor 1120 may include an allocation unit 1121 and a verification unit 1122. The allocator 1121 may allocate uplink resources to the terminal 1000. Upon receiving the ProSe-BSR from the terminal 1000, the verification unit 1122 may check the priority of each group of targets to transmit D2D data set in the terminal 1000 based on this.

As an example, when the truncated ProSe-BSR is received from the terminal 1000, the verification unit 1122 checks the reception time of the truncated ProSe-BSR, and the order of group information included in the truncated ProSe-BSR corresponds to It may be recognized that the priority for each group is set by the terminal for each group at the time point (the order of groups in which the terminal prefers to transmit D2D data at the time point). In this case, the allocator 1121 may allocate uplink resources required at the time point to the terminal 1000 according to the priority for each group set by the terminal at the time point.

The processor may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and/or a data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and/or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the present embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) that performs the above-described functions. Modules are stored in memory and can be executed by a processor. The memory may be inside or outside the processor, and may be connected to the processor through various well-known means.

Claims (14)

In a method of operating a buffer state report (BSR) by a terminal in a wireless communication system supporting device-to-device (D2D) communication,
Receiving uplink resource allocation information from a base station;
Configuring a truncated (truncated) BSR including buffer status information for at least one group according to the priority of each group to which the D2D data is to be transmitted; And
And transmitting the truncated BSR to the base station,
Here, in the truncated BSR, the index value of the logical channel identification information (LCID: Logical Channel ID) field for indicating the truncated BSR is set to '11100', and the highest priority is given to the data transmission. Control of a length of 4 bits to identify a logical channel group (LCG) including a logical channel having a priority
A method of operating a buffer status report comprising element information.
The method of claim 1,
Before the step of receiving the uplink resource allocation information,
Further comprising the step of transmitting a list of the identifier of the target to transmit the D2D data to the base station using a Radio Resource Control (RRC) message,
Wherein the list includes a destination information list (ProseDestinationInfoList) to transmit D2D data by the terminal.
The method of claim 1,
The step of configuring the truncated BSR,
And checking whether the format of the transmitted BSR immediately before the configuration of the truncated BSR is a truncated BSR. The method of claim 3,
The step of configuring the truncated BSR,
And if the format of the BSR transmitted immediately before the configuration of the truncated BSR is a truncated BSR, adjusting the priority of each group to which the D2D data is to be transmitted. The method of claim 4,
The step of adjusting the priority of each group to which the D2D data is to be transmitted,
And increasing the priority of a group not included in the truncated BSR transmitted immediately before. The method of claim 4,
The step of adjusting the priority of each group to which the D2D data is to be transmitted,
And lowering the priority of the group included in the truncated BSR transmitted immediately before. The method of claim 4,
The priority of each group to which the D2D data is to be transmitted is,
A method of operating a buffer status report, characterized in that it is set based on a priority for each logical channel group set by the base station. The method of claim 1,
A method of operating a buffer status report, characterized in that a group having the highest priority among the groups to which the D2D data is to be transmitted is first included in the truncated BSR. The method of claim 2,
The destination information list (ProseDestinationInfoList), a buffer status report operating method, characterized in that including a ProSe destination ID having a length of 24 bits.
The method of claim 2,
Wherein the destination information list is mapped to a group index from 0 to a maximum of 15 of the 4-bit length for identifying the LCG in descending order.
In a method of operating a buffer state report (BSR) by a base station in a wireless communication system supporting device-to-device (D2D) communication,
Transmitting uplink resource allocation information to a terminal;
Receiving a truncated (truncated) BSR including buffer status information for at least one group according to the priority of each group to which the D2D data is to be transmitted from the terminal;
Recognizing a priority for each group of targets to transmit D2D data set in the terminal based on the truncated BSR; And
Including the step of allocating resources for D2D communication to the terminal,
Here, in the truncated BSR, the index value of the logical channel identification information (LCID: Logical Channel ID) field for indicating the truncated BSR is set to '11100', and the highest priority is given to the data transmission. Control of a length of 4 bits to identify a logical channel group (LCG) including a logical channel having a priority
A method of operating a buffer status report comprising element information.
The method of claim 11,
Before the step of transmitting the uplink resource allocation information,
Receiving a list of the identifiers of the target to which the D2D data is to be transmitted from the terminal through a Radio Resource Control (RRC) message,
Wherein the list includes a destination information list (ProseDestinationInfoList) to transmit D2D data by the terminal.
The method of claim 12,
The destination information list (ProseDestinationInfoList), a buffer status report operating method, characterized in that including a ProSe destination ID having a length of 24 bits.
The method of claim 12,
Wherein the destination information list is mapped to a group index from 0 to a maximum of 15 of the 4-bit length for identifying the LCG in descending order.

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