KR102318913B1 - Method and apparatus for operating buffer state report in wireless communication system supporting device to device communication - Google Patents

Abstract

A method and apparatus for operating a buffer status report in a wireless communication system supporting inter-terminal communication are provided. A method for operating a buffer status report by a terminal in a wireless communication system supporting device-to-device (D2D) communication includes changing a D2D transmission mode set in the terminal from a first transmission mode to a second transmission mode, and the D2D and, when a buffer state report for data to be transmitted through communication is triggered, canceling the triggered buffer state report, wherein the first transmission mode is received from the base station. The D2D communication may be performed using resources, and the second transmission mode may be a mode for performing the D2D communication using resource pool information for the D2D communication.

Description

Buffer status report operation method and apparatus in a wireless communication system supporting inter-terminal communication

The present invention relates to wireless communication, and in particular, in a wireless communication system supporting device-to-device communication, when a terminal performs inter-terminal communication using a resource allocated from a base station, a buffer state report ) relates to a method and apparatus for operating it.

Device-to-device (D2D) communication is a communication method that has been possible since the days of analog radios, and has a very 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 directly exchange data in a frequency band of the wireless communication system or other bands using the transmission/reception technology of the wireless communication system without going through an infrastructure such as a base station. means This enables the terminal to use wireless communication outside of the area where the wireless communication infrastructure is built, and provides advantages of reducing the network load of the wireless communication system.

For communication between terminals in such a wireless communication system, the base station may schedule resources necessary for terminals existing in in-coverage to transmit data through D2D communication. To this end, the terminal may notify the base station of how much data to be transmitted through D2D communication exists in the buffer in the terminal through a buffer state report.

Meanwhile, in an exceptional case, the UE may transmit D2D data through a resource selected by itself without being allocated a resource required for data transmission through the D2D communication from the base station. However, in this case, if there is an already triggered buffer status report in the terminal, how the terminal operates the triggered buffer status report has not yet been determined, and specific operations and definitions for this have not yet been determined. the current situation.

It is an object of the present invention to provide a method and apparatus for operating a buffer status report for data to be transmitted through communication between terminals in a wireless communication system supporting inter-terminal communication.

Another technical object of the present invention is to provide a method and apparatus by which a terminal can efficiently allocate resources for terminal-to-terminal communication in a wireless communication system supporting terminal-to-terminal communication.

According to an aspect of the present invention, in a method for operating a buffer status report by a terminal in a wireless communication system supporting device-to-device (D2D) communication, the D2D transmission mode set in the terminal is transmitted to the second transmission mode in the first transmission mode. mode change and when a buffer state report for data to be transmitted through the D2D communication is triggered, the step of canceling the triggered buffer state report; The first transmission mode is a mode in which the D2D communication is performed using resources allocated from the base station, and the second transmission mode is a mode in which the D2D communication is performed using resource pool information for the D2D communication. can

According to another aspect of the present invention, in a method for operating a buffer status report by a terminal in a wireless communication system supporting D2D communication, the terminal set to the first transmission mode for performing the D2D communication using the resource allocated from the base station is the D2D Operating in the second transmission mode for performing the D2D communication using resource pool information for communication, and canceling the triggered buffer status report when there is no data to be transmitted through the D2D communication have.

According to the present invention, a terminal that allocates resources for inter-terminal communication during inter-terminal communication in a wireless communication system or a terminal existing within a service range of a base station can efficiently allocate resources for inter-terminal communication.

1 is a diagram illustrating a wireless communication system to which the present invention is applied.
2 is a diagram for explaining the concept of cellular network-based D2D communication applied to the present invention.
3 is a diagram illustrating a process of transmitting a ProSe-BSR to which the present invention is applied.
4 to 8 are flowcharts illustrating a method for operating a buffer status report for communication between terminals by a terminal according to an embodiment of the present invention.
9 is a flowchart illustrating a method for operating a buffer status report for communication between terminals by a base station according to an embodiment of the present invention.
10 is a block diagram illustrating 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 together with the contents of the present invention. In adding reference numerals to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated in different drawings. In addition, in describing the embodiments of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the detailed description thereof will be omitted.

In addition, this specification describes a wireless communication network, and the work performed in the wireless communication network is performed in the process of controlling the network and transmitting data in a system (eg, a base station) having jurisdiction over the wireless communication network, or the corresponding wireless communication network. An operation may be performed in a terminal included in the network.

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

Referring to FIG. 1 , a wireless communication system 10 may provide a communication service between a base station and a terminal. In a wireless communication system, a terminal and a base station may wirelessly transmit and receive data. In addition, the wireless communication system may support device-to-device (D2D) communication between the terminal and the terminal. A wireless communication system supporting D2D communication will be described later.

In the wireless communication system 10 , a base station (BS) 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. A site may include a plurality of regions 15a, 15b, and 15c, which may be referred to as sectors. Each sector 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 .

The base station 11 generally refers to a station that communicates with a UE (User Equipment, 12), an evolved-NodeB (eNodeB), a Base Transceiver System (BTS), an access point (Access Point), a femto base station ( Femto eNodeB), home base station (HeNodeB: Home eNodeB), relay (relay), may be called other terms such as remote radio head (RRH: Remote Radio Head).

The terminal 12 may be fixed or mobile, and may include a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a personal digital assistant (PDA). , a wireless modem, a handheld device, and the like.

The base station 11 may be referred to by various terms such as a megacell, a macrocell, a microcell, a picocell, and a femtocell, depending on the size of coverage provided by the base station. A cell may be used as a term indicating a frequency band provided by a base station, coverage of the base station, or a base station.

Hereinafter, downlink means a communication or communication path from the base station 11 to the terminal 12 , and uplink means a communication or communication path from the terminal 12 to the base station 11 . do. In the 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 .

There is no limitation on the 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, and various multiple access schemes such as OFDM-CDMA can be used. These modulation techniques increase the capacity of the communication system by demodulating signals received from multiple users of the communication system. In addition, a Time Division Duplex (TDD) method transmitted using different times or a Frequency Division Duplex (FDD) method transmitted using different frequencies may be used for uplink transmission and downlink transmission.

The layers of the radio interface protocol between the terminal and the base station are based on the lower three layers of the Open System Interconnection (OSI) model widely known in communication systems, the first layer (L1), the second layer It may be divided into a second layer (L2) and a third layer (L3).

The physical layer belonging to the first layer provides an information transfer service using a physical channel. The physical layer is connected to a media access control (MAC) layer, which is an upper layer, through a transport channel. Data is transmitted through a transport channel between the MAC layer and the physical layer. Transport channels are classified according to how data is transmitted through the air interface. In addition, data is transmitted through a physical channel between different physical layers (ie, between the physical layers of the terminal and the base station). The physical channel may be modulated in an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and uses time and frequency and a space generated by a plurality of antennas as radio resources.

For example, PDCCH (Physical Downlink Control CHannel) among physical channels informs the UE of resource allocation of PCH (Paging CHannel) and DL-SCH (DownLink Shared CHannel) and HARQ (Hybrid Automatic Repeat Request) information related to DL-SCH, An uplink scheduling grant informing the UE of resource allocation of uplink transmission may be carried. In addition, a Physical Control Format Indicator CHannel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs, and is transmitted every subframe. In addition, a Physical Hybrid ARQ Indicator CHannel (PHICH) carries a HARQ ACK/NAK signal in response to uplink transmission. In addition, PUCCH (Physical Uplink Control CHannel) carries uplink control information such as HARQ ACK/NAK, scheduling request, and CQI for downlink transmission. In addition, a Physical Uplink Shared CHannel (PUSCH) carries an UpLink Shared CHannel (UL-SCH). When necessary according to the configuration and request of the base station, the PUSCH may include CSI (Channel State Information) information such as HARQ ACK/NACK and CQI.

The data link layer corresponding to the second layer of the OSI model includes a MAC layer, a Radio Link Control (RLC) layer, and a Packet Data Convergence Protocol (PDCP) layer.

The MAC layer performs multiplexing or demultiplexing to a transport block provided as a physical channel on a transport channel of a MAC SDU (Service Data Unit) belonging to a logical channel and a transport channel and a mapping between a logical channel and a logical channel. can do. The MAC layer provides services to the RLC layer through logical channels. The logical channel can be divided into a control channel for transmitting control domain information and a traffic channel for transmitting user domain information. For example, as services provided from the MAC layer to an upper layer, there is data transfer or radio resource allocation.

The RLC layer may perform concatenation, segmentation, and reassembly of RLC SDUs. The RLC layer has three types of transparent mode, unacknowledged mode, and acknowledged mode to ensure various QoS (Quality of Service) required by radio bearer (RB). operation mode is provided.

The PDCP layer may perform user data transfer, header compression and ciphering, and control plane data transfer and encryption/integrity protection.

The RRC (Radio Resource Control) layer belonging to the third layer of the OSI model is related to configuration, re-configuration, and release of RBs and is responsible for controlling logical channels, transport channels and physical channels. . RB means a logical path provided by the first layer (PHY layer) and the second layer (MAC layer, RLC layer, PDCP layer) for data transfer between the terminal and the network. Configuring the RB means a process of defining the characteristics of a radio protocol layer and a channel to provide a specific service, and setting each specific parameter and operation method. The RB may be divided into a signaling RB (SRB) and a data RB (DRB). The SRB is used as a path for transmitting RRC messages and NAS (Non-Access Stratum) messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane. Hereinafter, simply expressing RB without distinguishing between SRB and DRB means DRB.

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

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

Recently, a method of performing discovery and direct communication between devices in network coverage or out-of-coverage for the purpose of public safety, etc. has been proposed. is being studied. A terminal that transmits a signal based on inter-terminal communication may be defined as a transmitting terminal (Tx UE), and a terminal that receives a signal based on inter-terminal communication 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. Meanwhile, a signal transmitted by the transmitting terminal may be received by two or more receiving terminals.

In the 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, since the terminals transmit data over a relatively short distance, consumption of transmission power and transmission latency of the terminal may be reduced. In addition, from the viewpoint of the entire system, since the existing cellular-based communication and the D2D communication use the same resource, frequency utilization efficiency can be improved.

D2D communication may be divided into a communication method of a terminal located within (in-coverage) of network coverage (base station coverage) and a communication method of a terminal located outside of network coverage (out-of-coverage).

Referring to FIG. 2 , communication between a first terminal 210 located in a first cell and a second terminal 220 located in a second cell, and a third terminal 230 located in the first cell and a first terminal located in the first cluster Communication between the 4 terminals 240 may be D2D communication within network coverage. Communication between the fourth terminal 240 located in the first cluster and the fifth terminal 250 located in the first cluster may be D2D communication outside the network coverage. Here, the fifth terminal 250 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 an out-of-coverage terminal.

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 network coverage may be used for public safety, ultra-low latency service, commercial purpose service, and the like. D2D communication outside of network coverage may be used only for public safety.

As an embodiment of performing D2D communication, the base station 200 may transmit D2D resource allocation information to the first terminal 210 . The first terminal 210 is a terminal located within the coverage of the base station 200 . The D2D resource allocation information may include allocation information on transmission resources and/or reception resources that can be used for D2D communication between the first terminal 210 and another terminal (eg, the second terminal 220 ).

Upon receiving the D2D resource allocation information from the base station, the first terminal 210 may transmit the D2D resource allocation information to the second terminal 220 . The second terminal 220 may be a terminal located outside the coverage of the base station 200 . The first terminal 210 and the second terminal 220 may perform D2D communication based on D2D resource allocation information. Specifically, the second terminal 220 may obtain information about the D2D communication resource of the first terminal 210 . The second terminal 220 may receive data transmitted from the first terminal 210 through a resource indicated by the information on the D2D communication resource of the first terminal 210 .

In D2D communication, a UE may transmit physical layer control data to another UE. However, a separate channel (eg, a physical uplink control channel (PUCCH)) for transmitting physical layer control data in D2D communication may not be defined. When a physical layer control channel is not defined in D2D communication, the UE may use various methods to transmit control data for D2D communication.

Here, physical layer control data for synchronization in D2D communication includes information transmitted through a synchronization channel, and may be provided through, for example, a Physical D2D Synchronization CHannel (PD2DSCH) channel. The physical layer control data for the data communication includes scheduling assignment (SA) information, and may be similar to a PUSCH format for D2D communication or may be provided through the same channel as the PUSCH format. And, in D2D communication, actual traffic data that is distinguished from physical layer control data may be expressed in terms of D2D data.

Additionally, a method for transmitting higher layer control data other than the physical layer in D2D communication may be defined.

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 the terminal can perform D2D communication only when resources for D2D communication are allocated from the base station, and the base station transmits the D2D grant to the transmitting terminal. The D2D grant includes parameter information to be determined by the base station among scheduling assignment (SA) information, which is control information to be secured for D2D data reception in the receiving terminal during D2D communication, resource allocation information for the SA, and the SA. It indicates resource allocation information for the indicated data to the transmitting terminal. The parameter information to be determined by the base station includes resource allocation information for data indicated by the SA, and the like. The D2D grant is transmitted to the transmitting terminal through downlink control information (DCI), and may be transmitted through a PDCCH or an EPDCCH. The D2D grant is control information that is used for D2D purposes through an uplink grant or a D2D-RNTI allocated to each UE. The D2D grant may be expressed as an SA/data grant. The D2D-RNTI is an identifier for performing D2D communication, which may be referred to as a Side Link (SL)-RNTI. The Sidelink refers to a UE to UE interface that performs D2D communication (ProSe direct communication and ProSe Direct Discovery) (Sidelink is defined that UE to UE interface for ProSe direct communication and ProSe Direct Discovery).

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 transmit D2D data by internally selecting a resource to be used from among available radio resources during D2D communication. The terminal 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 the second transmission mode provided from the base station. Only when it exists, it can operate in the second transmission mode only for the specific cell.

However, if the base station does not allow operation in the second transmission mode, that is, there is information indicating that a specific cell in the base station can support D2D, but D2D resource pool information for the second transmission mode is provided from the base station If not, it cannot operate in the second transmission mode. In addition, when D2D resource pool information for the second transmission mode is valid only in the RRC connected mode, the RRC idle (IDLE) mode UE operates in the second transmission mode even if there is D2D resource pool information for the second transmission mode. Can not.

However, when the terminal is located in a non-network service area, that is, in 'Any Cell Selection' mode, which is a case in which a serviceable cell is not selected although an RRC idle mode terminal, the UICC (Universal Subscriber Identity (USIM) of the terminal) Module) The second transmission mode using D2D resource pool information for the second transmission mode stored in the Integrated Circuit Card), etc. or using the D2D resource pool information for the second transmission mode received through the base station in the previous network service area. can operate as

In a wireless communication system, the terminal reports its buffer status to the base station in order to be allocated resources necessary for transmitting uplink data (data to be transmitted to the base station) existing in the buffer in the terminal, and the base station reports the buffer status reported from the terminal. A resource to be allocated to each terminal is scheduled based on the information.

Therefore, when the wireless communication system supports D2D communication, the base station needs to schedule resources required for terminals existing in in-coverage to transmit data through D2D communication. It is necessary to know how much data (hereinafter referred to as D2D data) to be transmitted through D2D communication exists. The terminal may inform the base station of how much data is to be transmitted through D2D communication in the buffer in the terminal through the following procedure.

3 is a diagram illustrating a process in which a terminal transmits a ProSe-BSR to a base station in order to transmit D2D data in a first transmission mode in a wireless communication system according to the present invention.

When data to be transmitted through a D2D link exists in a DRB configured for D2D in a terminal capable of D2D communication in a wireless communication system, a buffer status report (BSR) is triggered (S310). Hereinafter, in the present invention, the BSR for D2D data is referred to as a ProSe-BSR. The ProSe-BSR means a BSR for D2D communication that is distinct from the BSR defined and used in the current wireless communication system.

When ProSe-BSR is triggered, the UE transmits a Scheduling Request (SR) to the base station to induce allocation of resources for transmission of D2D data and ProSe-BSR (S320), and uplink for the SR from the base station A grant (UL grant) is received (S330). Here, the SR is transmitted to the base station through the PUCCH. The SR may be used by sharing the SR used in the existing wireless communication system, or the base station may use a resource additionally allocated for the SR for D2D purpose by distinguishing it from the SR. When defining an SR for D2D use by distinguishing it from the existing SR, the SR may be defined as a ProSe-SR. For convenience of description, SR and ProSe-SR are not distinguished and are collectively referred to as SR.

When an SR is triggered, the SR is pending until canceled. On the other hand, the terminal does not accept all data pending for the uplink grant for transmission, or a MAC PDU (Media Access Control Protocol Data Unit) is configured and the MAC PDU is configured in a buffer state including the last event. In case of including ProSe-BSR, all pending SRs are canceled and a timer (sr-ProhibitTimer) for preventing SRs from being transmitted is stopped.

Specifically, when the SR is triggered and there is no currently pending SR, the UE sets the SR count (SR_COUNTER) value to 0. However, if the SR is pending and there is a valid PUCCH resource to send the SR in this Transmission Time Interval (TTI), this TTI is not part of the measurement gap and sr-ProhibitTimer is not in progress , if the SR_COUNTER value is less than the maximum number of SR transmissions, the SR count value is incremented by 1, and after instructing the physical layer to transmit the SR signal through the PUCCH, sr-ProhibitTimer is started. 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 PUCCH and SRS, and all configured downlink assignments and uplink grants are cleared. Then, the random access procedure is initialized and all pending SRs are canceled.

On the other hand, if the SR is pending but there is no UL-SCH resource available for transmission in any TTI, the UE initializes a random access procedure and cancels all pending SRs. Therefore, the ProSe-BSR may be delivered to the base station through the random access procedure.

Upon receiving the uplink grant for the SR, the terminal transmits the ProSe-BSR to the base station (S340). And when receiving the D2D grant for ProSe-BSR from the base station (S350), the data is transmitted to the target terminal by using the resources allocated for D2D data transmission (S360). As such, the ProSe-BSR is for the UE to notify the serving base station of information on the amount of transmittable data present in the D2D link buffer. In the present invention, as an example, it is illustrated that the ProSe-BSR procedure is performed after SR transmission. However, if the UE receives an uplink grant sufficient to transmit ProSe-BSR before SR transmission, ProSe-BSR transmission may be performed before SR transmission.

The base station configures a periodic BSR timer (periodicBSR-Timer) and a retransmission BSR timer (retxBSR-Timer) for ProSe-BSR through signaling defined in the RRC layer, thereby proSe-BSR procedure for a logical channel in each terminal control A logical channel group (LCG) may be configured in each terminal through optional signaling (optionally configured by RRC signal by eNB), and ProSe-BSR is performed for the LCG.

The LCG is set separately from the LCG that is the target of the BSR for the wireless communication system. For example, it means that the LCG for ProSe-BSR and the LCG for the existing BSR are separately configured.

Here, the LCG, which is the target of the BSR for the wireless communication system, consists of only logical channels (DCCH, DTCH) configured for data transmission of the wireless communication system, and the index of the LC for this can be 0 to 11. have. On the other hand, the LCG, which is the target of the BSR for D2D communication, has only logical channels (PTCH) configured for the D2D data transmission, and the LC index for this is the LC index (0) for the wireless communication system. ~11), may have indices 0 to 11 of the LC for D2D communication.

In addition, the base station may additionally set a periodic timer/retransmission timer for ProSe-BSR, etc. for each terminal separately from the BSR for the wireless communication system through RRC.

The UE configures the ProSe-BSR based on the data buffered in each LCG in the UE. A maximum of four LCGs may be configured in the terminal. The format of the ProSe-BSR includes a short BSR for reporting the buffer status corresponding to one LCG, or a long BSR or truncated BSR for reporting the buffer status corresponding to four LCGs. etc. may exist.

For the ProSe-BSR procedure, the UE must consider a suspended radio bearer (RB) and all non-reserved RBs. ProSe-BSR may be divided into regular ProSe-BSR (ProSe-BSR), Padding ProSe-BSR (ProSe-BSR), and Periodic ProSe-BSR (ProSe-BSR).

In the regular ProSe-BSR, data transmittable to the logical channel included in the LCG exists in the RLC entity or the PDCP entity, or in the uplink transmittable through a logical channel having a higher priority than other logical channels in which transmittable data already exists. Triggered when data becomes available. In addition, the regular ProSe-BSR is triggered even when the retransmission BSR timer for ProSe-BSR expires and the UE has transmittable data in a logical channel in the LCG.

The padding BSR is triggered when an uplink resource and a resource for transmitting a padding BSR for a wireless communication system are allocated and the number of remaining padding bits is equal to or greater than a size for ProSe-BSR transmission.

Alternatively, the padding ProSe-BSR is triggered when uplink resources and resources for BSR transmission for a wireless communication system are allocated and the number of remaining padding bits is equal to or greater than the size for ProSe-BSR transmission.

And, the periodic ProSe-BSR is triggered when the periodic BSR timer for ProSe-BSR expires.

The regular ProSe-BSR and the periodic ProSe-BSR are transmitted in a long ProSe-BSR format when more than one LCG (at least two LCGs) has data to be transmitted in the TTI in which the corresponding ProSe-BSR is transmitted, otherwise (one When only the LCG of ' has data to be transmitted), it can be transmitted in a short BSR format.

The padding ProSe-BSR is equal to or greater than the combined size of the short ProSe-BSR and the short ProSe-BSR subheader in the number of padding bits included in the MAC PDU, but the long ProSe-BSR and the long ProSe-BSR subheader If more than one LCG has data to transmit in the TTI in which the corresponding ProSe-BSR is transmitted, which is smaller than the combined size, a truncated ProSe-BSR for the LCG including the logical channel having the highest priority for data transmission It may be configured and transmitted in a format. Otherwise, it is transmitted in a short ProSe-BSR format. Alternatively, when only the short ProSe-BSR format is possible, the ProSe-BSR format is always transmitted in the short ProSe-BSR format.

On the other hand, when the number of padding bits is equal to or greater than the combined size of the long ProSe-BSR and the long ProSe-BSR subheaders, the padded ProSe-BSR is transmitted in the long ProSe-BSR format. Alternatively, when only the short ProSe-BSR format is possible for the ProSe-BSR format, the short ProSe-BSR format is always transmitted.

Meanwhile, when at least one ProSe-BSR is triggered and not canceled, the UE performs the ProSe-BSR procedure. If the uplink resource for new transmission is allocated for this TTI, the UE instructs the multiplexing and assembly procedure for generation of the ProSe-BSR MAC control element, and starts or Restart, and start or restart the retransmission BSR timer (retxBSR-Timer) for ProSe-BSR. Here, the procedure of starting or restarting the periodic BSR timer for the ProSe-BSR is excluded when a truncated ProSe-BSR is generated. If uplink resources for new transmission are not allocated in this TTI, regular ProSe-BSR is triggered.

In this case, one MAC PDU includes only one ProSe-BSR MAC control element even if multiple ProSe-BSRs are triggered. In addition, when regular ProSe-BSR or periodic ProSe-BSR can be transmitted, it always takes precedence over padding ProSe-BSR. In addition, upon confirming reception of an indicator indicating transmission of new data for all UL-SCHs, the UE restarts the retransmission BSR timer. All triggered BSRs shall be canceled when the BSR is included in the MAC PDU.

The UE transmits one regular or periodic ProSe-BSR in one TTI. Also, according to the present invention, the ProSe-BSR may be transmitted in the same TTI as the BSR of the wireless communication system. For example, the ProSe-BSR for the D2D service and the existing BRS for the general data service may be simultaneously transmitted in the same subframe (TTI). In this case, information classification for the corresponding BSR may be identified through the LCID.

If the UE is requested to transmit multiple MAC PDUs in one TTI, one padding ProSe-BSR may be included in arbitrary MAC PDUs that do not include regular or periodic ProSe-BSR. Accordingly, one padding ProSe-BSR may be included in any MAC PDUs including regular or periodic BSR for a wireless communication system. That is, although the padding BSR has a higher priority than the padding ProSe-BSR, the padding ProSe-BSR may be included first only in an arbitrary MAC PDU including a regular or periodic BSR. This may be included in a case where transmission of a single MAC PDU is requested in one TTI. All ProSe-BSRs always reflect the buffer state after MAC PDUs to be transmitted based on the previously received D2D grant are configured by the UE based on the TTI through which the ProSe-BSR is transmitted. Each LCG reports one buffer status value per one TTI, and the buffer status value is reported through ProSe-BSR for the LCG in all ProSe-BSRs. That is, in the same TTI, one ProSe-BSR value must be transmitted for each LCG, and the buffer status value for the LCG must be the same in all ProSe-BSRs transmitted in the same TTI. On the other hand, it is not allowed for the padding ProSe-BSR to cancel the regular or periodic ProSe-BSR. Padding ProSe-BSR is triggered for a specific MAC PDU, and triggering of the padding ProSe-BSR is canceled when a specific MAC PDU is generated.

However, in the case of the existing wireless communication system, all triggered BSRs can transmit all pending data, but are canceled when an uplink grant that cannot additionally transmit a BSR MAC control element is received. Also, all triggered BSRs are canceled when the BSR is included in the MAC PDU. That is, the existing wireless communication system can cancel the triggered BSR only in the following situations.

1. When the resource secured through the UL grant in the corresponding subframe can accommodate all data to be transmitted in the uplink, but cannot include the BSR MAC CE including the MAC subheader.

In this case, the UE cancels the triggered BSR and transmits all data to be transmitted through the uplink through the uplink.

2. When the BSR is included in the MAC PDU for uplink transmission.

As described above, in D2D communication, the base station needs to schedule resources required for terminals existing in in-coverage to transmit data through D2D communication. How much data (hereinafter, referred to as D2D data) to be transmitted to . However, in an exceptional case (eg, when the terminal cannot maintain an RRC connection state with the base station), the terminal does not allocate resources necessary for data transmission through the D2D communication from the base station, and uses a resource selected by itself to D2D. It should be able to transmit data. For this, the first transmission mode and the second transmission mode may be supported during D2D communication.

However, when the terminal is set to or operates in the second transmission mode, resources for D2D transmission cannot be controlled by the base station. Therefore, the base station must reserve the corresponding resource for D2D transmission. The reserved resource may be determined by the number of terminals capable of operating in the second transmission mode and the expected resource consumption of each terminal.

If the resources reserved for the second transmission mode increase, since the total resources are limited, the amount of resources available for general wireless communication (eg, LTE communication) is reduced, which may affect the overall system transmission rate. can Accordingly, the base station may reduce the number of terminals capable of operating in the second transmission mode in order to reduce the amount of resources reserved for the second transmission mode. To support this, the base station may allow the terminal to operate in the second transmission mode only in exceptional cases.

However, when the D2D transmission mode set in the terminal is changed from the first transmission mode to the second transmission mode, or when the terminal set to the first transmission mode operates in the second transmission mode, the buffer already triggered in the terminal When there is a status report, it has not yet been decided how to operate the triggered buffer status report.

4 to 8 are flowcharts illustrating a method for operating a buffer status report for communication between terminals by a terminal according to an embodiment of the present invention. Hereinafter, with reference to FIGS. 4 to 8 , a buffer triggered when the D2D transmission mode set in the terminal is changed from the first transmission mode to the second transmission mode, or when the terminal set to the first transmission mode operates in the second transmission mode Describes how to operate status reporting.

A terminal supporting D2D communication may perform D2D communication when a user of the terminal configures the terminal to enable D2D communication through a user interface (UI). Alternatively, a network (eg, a D2D server that manages Proximity Services (ProSe) ID and ProSe Application ID of a terminal using D2D communication, a serving base station of the corresponding terminal, etc.) enables the user of the terminal to enable D2D communication It is also possible to finally determine whether D2D communication is possible of the terminal set to do so. That is, the terminal may perform D2D communication only when D2D communication is permitted by the network, even if D2D communication is enabled by the user of the terminal. Information on whether D2D communication is possible may be displayed on the screen of the terminal.

Resources for D2D communication may be allocated by a terminal (hereinafter, cluster head) or a base station in charge of allocating resources for D2D communication during D2D communication. In this case, the UE needs to transmit a BSR for D2D data to the base station or the cluster head when performing D2D communication. 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.

Referring to FIG. 4 as an embodiment, the ProSe-BSR may be triggered by the same triggering condition as that of the existing BSR for uplink data (S410). In this case, for ProSe-BSR, an LCID different from the BSR for existing uplink data may be used. For example, a new LCID for distinguishing a short ProSe-BSR, a truncated ProSe-BSR, and a long ProSe-BSR may be assigned to the ProSe-BSR. Alternatively, one ProSe-BSR format may be used as a BSR for D2D data, and one new LCID indicating this may be used.

When the ProSe-BSR is triggered, the UE may determine whether the D2D transmission mode of the UE is currently set to the second transmission mode (S420). As a result of the check, the UE can cancel the triggered ProSe-BSR if it is set to the second transmission mode (S430), and if it is not set to the second transmission mode, uplink resource allocation based on the ProSe-BSR triggered by the base station The ProSe-BSR MAC CE may be included in the MAC PDU and transmitted to the base station (S440).

As an example, changing the D2D transmission mode of the terminal to the second transmission mode by the base station or in the above-described exceptional case (the case where the timer related to the RRC reset procedure and/or the timer related to the handover is in progress or is started, etc.) When the terminal changes the D2D transmission mode set in the terminal from the first transmission mode to the second transmission mode due to a case of allowing, etc., the terminal deletes all ProSe-BSRs that have been triggered for operation to the first transmission mode. Cancel. Here, the first transmission mode means a mode in which the D2D communication is performed using a resource allocated from the base station, and the second transmission mode is a second transmission mode resource pool information for the D2D communication. It may mean a mode in which the D2D communication is performed using In other words, all triggered ProSe-BSR may be canceled when the D2D communication mode set in the terminal is changed from the first transmission mode to the second transmission mode due to an exceptional case, and the terminal itself or the base station is D2D transmission configured in the terminal It may be canceled when the mode is changed from the first transmission mode to the second transmission mode.

The terminal operating in the first transmission mode and the terminal operating in the second transmission mode receive D2D data in the following D2D resource pool information included in the reception resource pool (commRxPool) and the general common transmission resource pool (commTxPoolNormalCommon) information should be checked. Here, the reception resource pool is information indicating resources that are allowed to be received by the D2D terminal operating in RRC IDLE and Connected mode, and the general common transmission resource pool is information that is allowed to be transmitted by the D2D terminal operating in the RRC IDLE mode. Information indicating resources.

- SA resource pool information

- Data resource pool information (included in the case of a common transmission resource pool, but not included in the case of the resource pool for the first transmission mode among the configuration information of the reception resource pool)

- TDD configuration information (included only when the reception resource pool information is a neighbor cell and operates in TDD)

* Here, transmission resource pool information (commTxPoolExceptional) for an exceptional case defined separately from the resource pool information for the exceptional case may be defined.

All of the resource pool information may be transmitted to all terminals in a corresponding cell through a broadcast channel, and a terminal desiring a D2D communication operation may receive D2D data that the terminal desires to receive from radio resources based on all the resource pool information. Monitoring operation should be performed to receive In the reception resource pool information, there is transmission resource pool information dedicatedly provided by the base station for the transmission operation in the first transmission mode or the second transmission mode only to the terminal operating in the RRC connected mode in the corresponding cell. may be included. The first transmission mode or second transmission mode transmission resource pool information provided exclusively for each cell should be set so that there is no colliding physical resource for each cell in order to avoid mutual interference. In addition, when the resources allocated for ProSe communication are insufficient and conflicting resources occur, the range of mutual interference is limited to the same resource range by making the characteristics of the transmission signals set for each cell, such as the cyclic prefix length, the same. In order to make this possible, cooperation between base stations should be made.

Here, the RRC reset procedure related timer may be a T311 timer, and the handover related timer may be a T304 timer, and may be defined as shown in Tables 1 and 2 below, respectively.

Timer Start Stop At expiry T311 Upon initiating the RRC connection re-establishment procedure Selection of a suitable E-UTRA cell or a cell using another RAT. Enter RRC_IDLE

Timer Start Stop At expiry T304 Reception of RRCConnectionReconfiguration message including the MobilityControl Info or
reception of MobilityFromEUTRACommand message including CellChangeOrder Criterion for successful completion of handover within E-UTRA, handover to E-UTRA or cell change order is met (the criterion is specified in the target RAT in case of inter-RAT) In case of cell change order from E-UTRA or intra E-UTRA handover, initiate the RRC connection re-establishment procedure; In case of handover to E-UTRA, perform the actions defined in the specifications applicable for the source RAT.

Referring to Table 1, the T311 timer is started when an RRC connection re-establishment procedure is started. And, when a suitable Evolved UMTS Terrestrial Radio Access (E-UTRA) cell is selected or a cell using another radio access technology (RAT) is selected, it is stopped. Also, when entering the RRC idle state, it expires. Referring to Table 2, the T304 timer includes an RRC connection reconfiguration message including mobility control information. It is started when receiving or receiving a message including a cell change order (MobilityFromEUTRACommand message). Here, the RRC connection reconfiguration message including the mobility control information may be referred to as a handover command message. That is, the T304 timer is started during handover within the LTE network or inter-RAT handover to the LTE system, and is stopped when the handover is successfully completed.

Meanwhile, when canceling ProSe-BSR, the UE may initialize (reset) a periodic BSR timer (periodic BSR-timer) and a retransmission BSR timer (retxBSR-timer) configured for ProSe-BSR. The periodic BSR timer and retransmission BSR timer configured for the initialized ProSe-BSR may be set to a startable state when the D2D transmission mode of the UE is changed from the second transmission mode to the first transmission mode.

In addition, when the terminal changes the D2D transmission mode set in the terminal from the first transmission mode to the second transmission mode as shown in FIG. 5 ( S510 ), it can be determined whether resource pool information for the second transmission mode exists. There is (S520). Here, when the D2D transmission mode set in the terminal is changed due to an exceptional case, the first transmission mode may be changed to a fallback mode ( S510 ). The fallback mode is defined as the same D2D terminal operation as the second transmission mode, but the resource pool information for the fallback mode includes transmission resource pool information for an exceptional case defined separately from the resource pool information for the exceptional case ( commTxPoolExceptional). Therefore, when the D2D transmission mode set in the terminal is changed from the first transmission mode to the fallback mode, it may be additionally determined whether resource pool information for the fallback mode exists (S520). Here, the resource pool information to be preferentially applied in the fallback mode may be general common transmission resource pool information or transmission resource pool information for exceptional cases. If at least one of the two resource pool information exists, the UE uses all the logical channels configured for the D2D communication between the UEs to prevent ProSe-BSR from being triggered any more (ProSe Communication Traffic Channel (PTCH)). It can be excluded from the triggering target of ProSe-BSR (S530). However, when the two types of resource pool information do not exist, the UE cannot operate in the second communication mode, and thus may suspend data transmission for the PTCH (S540).

Thereafter, as shown in FIG. 6 , the exceptional case is resolved (eg, the timer related to the RRC reset procedure and/or the timer related to the handover is stopped), and the D2D transmission mode set in the terminal is transferred to the first transmission in the second transmission mode. When the mode is changed (S610), the UE may start an initialized periodic BSR timer and a retransmission BSR timer, and may transmit a buffer status report for data to be transmitted through the D2D communication. That is, the normal ProSe-BSR procedure may be restarted (S620).

In the case of handover, after the terminal completes the handover to the target base station (immediately after the T304 timer is stopped), the handover preparation step, that is, the source base station to the target base station, is changed to the first transmission mode and operated immediately. When a handover request message including terminal information including ProSe configuration information such as transmission mode is transmitted and the target base station transmits a message allowing handover based on this to the source base station, ProSe configuration information necessary for operation in the first transmission mode is included. to transmit The configuration information may include D2D-RNTI information to be used by the target base station, ProSe-BSR related configuration information, and SA pool information.

Meanwhile, in another embodiment, as shown in FIG. 7 , when the D2D transmission mode set in the terminal is changed from the first transmission mode to the second transmission mode due to an exceptional case (S710), the terminal may be transmitted through D2D communication. Whether to cancel ProSe-BSR may be determined according to the existence of data. For example, when the D2D transmission mode set in the UE is changed from the first transmission mode to the second transmission mode as the RRC reset procedure related timer and/or the handover related timer is in progress, the UE data to be transmitted through D2D communication ProSe-BSR can be canceled only when does not exist (S720). At this time, all ProSe-BSR timers (periodic BSR timer and retransmission BSR timer) are initialized and may not start until the UE changes the D2D transmission mode to the first transmission mode. Even in this case, the terminal may determine whether resource pool information for the second transmission mode exists. In addition, if the second transmission mode resource pool information exists, all PTCHs may be excluded from the triggering target of the ProSe-BSR, and if the second transmission mode resource pool information does not exist, data transmission for all PTCHs may be stopped.

Meanwhile, in another embodiment, as shown in FIG. 8 , the UE may operate in the second transmission mode while the first transmission mode is set without changing the D2D transmission mode ( S810 ). This may be performed when the base station does not propose the D2D transmission mode of the terminal and/or when at least one of a timer related to an RRC reset procedure and a timer related to a handover is in progress or is started. In this case, even though the terminal can transmit D2D data in the second transmission mode, when receiving a D2D grant from the base station, it transmits the D2D data in the first transmission mode. That is, the terminal may maintain the first transmission mode as the D2D transmission mode. In this case, the UE may not cancel the triggering of ProSe-BSR because it is set to the first transmission mode even if it starts operating in the second transmission mode. However, the terminal may determine whether data to be transmitted through D2D communication exists and, if there is no data to be transmitted through D2D communication, cancel the triggered BSR (S820).

On the other hand, when the UE cannot maintain the RRC connected mode even though the exceptional case is resolved (that is, when the timer for RLF or the timer for handover expires), the D2D transmission mode can be changed to the second transmission mode. . In addition, D2D data may be transmitted based on the secured second transmission mode D2D resource pool information.

Meanwhile, as another embodiment, in the exceptional case, the UE cancels ProSe-BSR through a reset operation of the MAC entity. The reset of the MAC entity may be performed at the request of a higher layer. The MAC entity reset operation includes the following operations.

- Stop all running timers.

- Values of new data indicators (NDIs) for all uplink HARQ processes other than uplink HARQ processes related to PSCH are set to 0.

- If there is a triggered SR and/or ProSe-SR procedure, it is canceled.

- If there is a triggered BSR and/or ProSe-BSR procedure, it is canceled.

- Flush soft buffers for all DL HARQ processes other than DL HARQ processes related to PSCH.

- For each DL HARQ process other than the DL HARQ processes related to PSCH, transmission for any TB received next is considered as a very first transmission.

Here, the ProSe Communication Shared CHannel (PSCH) is a transport channel for D2D data delivered from the MAC layer to the physical layer.

If the exceptional case is caused by the start of the RRC reconfiguration procedure, the UE suspends all DRBs except for the DRBs related to the PTCH, which is a logical channel related to the D2D data transmission, when the RRC reconfiguration procedure starts. If the exceptional case occurs due to the start of the handover procedure (when Mobility Control Information (MCI) is included in the RRC reconfiguration message), the terminal is a logical channel related to the D2D data transmission when the handover procedure starts. RLC and PDCP in all DRBs except for DRBs related to PTCH are re-established (re-establishment).

When the MAC entity for D2D communication is separated from the MAC entity for wireless communication, in the exceptional case, the MAC entity for D2D communication is reset and ProSe-BSR is cancelled.

At this time, the UE in which the exceptional case is in progress does not trigger ProSe-BSR even if transmittable data exists in RLC and PDCP in the DRB related to the PTCH. That is, ProSe-BSR triggering is not the exceptional case and is possible only when the UE is set to operate in the first transmission mode and is in the RRC connected mode.

9 is a flowchart illustrating a method for operating a buffer status report for communication between terminals by a base station according to an embodiment of the present invention.

Referring to FIG. 9 , the base station may transmit a second transmission mode permission message to the first terminal within coverage (S910). Here, the first terminal may be a terminal in which the D2D transmission mode is set to the first transmission mode. Upon receiving the second transmission mode permission message, the first terminal may change the D2D transmission mode to the second transmission mode in the above-described exceptional case.

When the first terminal is changed to the second transmission mode, the base station may receive ProSe-BSR from a second terminal set to the first transmission mode in addition to the first terminal (S920). Then, the base station may allocate a resource for D2D communication to the second terminal based on the received ProSe-BSR (S930), and the second terminal receiving this may perform D2D communication with the target terminal using the allocated resource. have.

As another example, when the UE receives an RRC reconfiguration message including mobility control information (MCI) from the base station, the UE releases the configuration of transmission resources during configuration for ProSe communication operation. This is to indicate that the configuration information for the first transmission mode or the second transmission mode configured by the source base station is no longer valid because the corresponding terminal moves to the target base station through handover.

For the release operation, release information may be included in the configuration information on the transmission resource in the RRC reconfiguration message and transmitted. Alternatively, when the terminal receives an RRC reconfiguration message including mobility control information (MCI) from the base station, it may perform an operation of releasing configuration information for transmission resources in the RRC reconfiguration message by itself.

As described above, when the configuration of the transmission resource for the first transmission mode or the second transmission mode is released, the terminal operates in the second transmission mode when transmitting data using the general common transmission resource pool information received through the system information. do. As described above, instead of configuration information for the first transmission mode or the second transmission mode configured by the source base station released due to the handover operation as described above, the QoS of ProSe communication can be maintained even in the RRC IDLE mode by using the available resources for the ProSe communication transmission resources. .

Alternatively, when the configuration of the transmission resource for the first transmission mode or the second transmission mode is released as described above, the terminal enters the fallback mode when transmitting data using the transmission resource pool information for an exceptional case received through the system information. can work As described above, the configuration information for the first transmission mode or the second transmission mode configured by the source base station is released due to the handover operation as described above, but since the RRC connected mode is maintained, transmission resource pool information for an exceptional case that can be used even in the RRC connected mode. can be used to maintain QoS of ProSe communication.

The transmission resource pool information used at this time may be resource pool information for ProSe communication provided by the target base station to the source base station (the base station that has transmitted the RRC reconfiguration message including the MCI), and the RRC reconfiguration message including the MCI. It may be provided and included in the terminal, and the terminal may perform an operation related to transmission based on the information provided by the target base station.

If there is no transmission resource pool information provided from the target base station or is not provided, the transmission resource pool information in the system information previously received from the source base station may be used.

After the handover is completed, the terminal may maintain the second transmission mode or the fallback mode until it receives and reflects information for configuration of transmission resources during configuration for ProSe communication operation from the target base station.

Alternatively, when the configuration of the transmission resource for the first transmission mode or the second transmission mode is released as described above, the terminal maintains the reception operation but may stop all transmission operations. That is, it can operate in the ProSe transmission stop mode. As described above, because the configuration information for the first transmission mode or the second transmission mode configured in the source base station is released due to the handover operation, the ProSe transmission operation is impossible. This means that only the terminal operating in the RRC connected mode in the source base station is dedicated to the physical resource in the transmission resource pool dedicated by the base station for the transmission operation in the first transmission mode or the second transmission mode and the target base station. (dedicated) This is because, when a collision may occur between physical resources in the transmission resource pool, a ProSe communication signal transmitted based on the transmission resource pool information of the source base station may act as interference with other ProSe communication signals in the target base station. Therefore, in order to remove such an interference factor, the transmission operation is stopped.

After the handover is completed, the terminal may maintain the transmission stop mode until it receives and reflects information for configuration of transmission resources during configuration for ProSe communication operation from the target base station.

Here, the source base station and the target base station may be different base stations or the same base station. In the case of the same base station, the frequency band may or may not be changed due to handover. If the base station or the frequency band does not change despite the handover operation, the base station determines that the RRC parameters between the base station and the terminal do not match each other, or the base station determines that downlink or uplink synchronization is not performed properly, or improves security This is when it is desired to change the key value shared between the base station and the terminal used for this purpose.

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

Referring to FIG. 10 , the wireless communication system supporting inter-terminal communication according to the present invention includes a terminal 1000 and a base station (or cluster head, 1050 ).

The terminal 1000 includes a processor 1005 , a radio frequency (RF) unit 1010 , and a memory 1015 . The memory 1015 is connected to the processor 1005 and stores various information for driving the processor 1005 . The RF unit 1010 is connected to the processor 1005 to transmit and/or receive a radio signal. For example, the RF unit 1010 may receive the second transmission mode permission message and D2D resource allocation information posted herein from the base station 1050 . Also, the RF unit 1010 may transmit an uplink signal such as ProSe-BSR published in this specification to the base station 1050 .

The processor 1005 implements the functions, processes and/or methods proposed herein. Specifically, the processor 1005 causes all steps according to FIGS. 4 to 8 to be performed.

For example, the processor 1005 may include a ProSe-BSR triggering determining unit 1006 , a timer determining unit 1007 , and a canceling unit 1008 . The ProSe-BSR triggering determining unit 1006 determines whether ProSe-BSR is triggered. When the D2D transmission mode of the current terminal is set to the second transmission mode, the tire determination unit 1007 determines whether an RRC reset procedure related timer and/or a handover related timer is in progress. The cancellation unit 1008 cancels all triggered ProSe-BSRs when the timer related to the RRC reset procedure and/or the timer related to the handover is in progress. In this case, the periodic BSR timer (periodic BSR-timer) and the retransmission BSR timer (retxBSR-timer) configured for ProSe-BSR may be reset.

Meanwhile, the processor 1005 may check whether resource pool information for the second transmission mode or resource pool information for the fallback mode exists. If at least one of the two resource pool information exists, all PTCHs configured for the D2D communication between the terminals may be excluded from the triggering target of the ProSe-BSR in order to prevent ProSe-BSR from being triggered any more. have. When the two types of resource pool information do not exist, the processor 1005 may suspend data transmission for the PTCH because it cannot operate in the second communication mode.

Thereafter, when it is determined by the timer determination unit 1007 that the RRC reset procedure related timer and/or the handover related timer has been stopped, the processor 1005 determines that the exceptional case has been resolved and an initialized periodic BSR timer and The retransmission BSR timer can be started and the normal ProSe-BSR procedure can be restarted.

The memory 1015 stores resource pool information for the second transmission mode according to the present specification, information on whether to allow the second transmission mode, and the like, and transmits the second transmission to the processor 1005 according to the request of the processor 1005 . Resource pool information for the mode may be provided.

The base station 1050 includes an RF unit (radio frequency (RF) unit, 1055 ), a processor 1060 , and a memory 1065 . The memory 1065 is connected to the processor 1060 and stores various information for driving the processor 1060 . The RF unit 1055 is connected to the processor 1060 to transmit and/or receive a radio signal. The processor 1060 implements the functions, processes and/or methods proposed herein. In the above-described embodiment, the operation of the base station 1050 may be implemented by the processor 1060 . The processor 1060 generates the second transmission mode permission message posted in this specification, and schedules a resource for D2D communication based on the ProSe-BSR received from the terminal.

For example, the processor 1060 may include a timer value setting unit 1061 , a ProSe-BSR checking unit 1062 , and a D2D resource allocating unit 1063 . The timer value setting unit 1061 sets various timer values described herein. The timer value set by the timer value setting unit 1061 may be transmitted to the terminal through the RF unit 1055 . The ProSe-BSR check unit 1062 may check the ProSe-BSR received from the terminal 1000 . The D2D resource allocator 1063 may allocate resources for D2D communication to the terminal 1000 operating in another first transmission mode based on the ProSe-BSR.

The processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and/or data processing devices. Memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and/or other storage devices. 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 function. A module may be stored in a memory and executed by a processor. The memory may be internal or external to the processor, and may be coupled to the processor by various well-known means.

In the exemplary system described above, the methods are described on the basis of a flowchart as a series of steps or blocks, however, the present invention is not limited to the order of steps, and some steps may occur in a different order or concurrent with other steps as described above. can In addition, those skilled in the art will understand that the steps shown in the flowchart are not exhaustive 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 present invention.

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

Claims (22)

A method of operating a terminal in a wireless communication system, the method comprising:
establishing a radio resource control (RRC) connection with the base station by the terminal;
Receiving configuration information including resource allocation mode information for direct data transmission between the terminal and other terminals from the base station and timer information related to a buffer status report (BSR) for direct data transmission between the terminals ;
determining, by the terminal, a radio link failure (RLF), wherein the RLF is related to a radio connection problem of the RRC connection;
initiating a re-establishment procedure for the RRC connection;
canceling all BSRs for direct data transmission between terminals based on the determined RLF, wherein the canceled BSRs for direct data transmission between terminals are related to direct data transmission between terminals scheduled by the base station;
starting the timer related to the BSR for direct data transmission between the terminals;
A step of performing, by the terminal, direct data transmission between terminals in the exceptional case by selecting a resource for direct data transmission between terminals in the exceptional case based on the information of CommTxPoolExceptional, wherein the CommTxPoolExceptional is the case of the exceptional case Indicating resource pool information for direct data transmission, a method.
According to claim 1,
Starting the timer related to the BSR for direct data transmission between the terminals comprises:
and starting a periodic BSR-timer and a retransmission BSR-timer (retx BSR-timer).
3. The method of claim 2,
Starting the periodic BSR-timer and the retransmission BSR-timer comprises:
stopping the periodic BSR-timer and the retransmission BSR-timer; and
setting timer values of the periodic BSR-timer and the retransmission BSR-timer to 0 (zero).
According to claim 1,
receiving resource selection mode information; and
Including; changing from the resource allocation mode to the resource selection mode based on the determined RLF.
According to claim 1,
determining, by the terminal and based on a determination that the exceptional case occurs, to change from the resource allocation mode to the resource selection mode; and
Selecting a resource for direct data transmission between the terminals in the exceptional case by the terminal in the resource selection mode and based on the resource pool information;
The exceptional case includes a case in which, as the RLF is detected, the establishment of the re-establishment procedure for the RRC connection is started, and a T311 timer related to the re-establishment procedure for the RRC connection is started. Way.
According to claim 1,
Receiving a CommTxPoolExceptional for direct data transmission between the terminals in the exceptional case. Way.
According to claim 1,
Receiving the CommTxPoolExceptional through a broadcast channel from the base station;
According to claim 1,
The CommTxPoolExceptional is included in a system information block (SIB).
In a terminal in a wireless communication system,
wireless transceiver; and
The radio transceiver establishes a radio resource control (RRC) connection with a base station, but resource allocation mode information for direct data transmission between the terminal and another terminal from the base station and a buffer for direct data transmission between the terminals Receive configuration information including timer information related to a status report (buffer status report, BSR),
processor;
The processor is configured to determine a radio link failure (RLF) by the terminal, wherein the RLF is related to a radio connection problem of the RRC connection,
and to start a re-establishment procedure for the RRC connection, and to cancel all BSRs for direct data transmission between terminals based on the determined RLF, and the canceled BSRs for direct data transmission between terminals are It is related to direct data transmission between terminals scheduled by the base station,
The processor is configured to start the timer related to the BSR for direct data transmission between the terminals, and select a resource for direct data transmission between terminals in an exceptional case based on the information of CommTxPoolExceptional. The terminal is configured to perform direct data transmission, wherein the CommTxPoolExceptional indicates resource pool information for direct data transmission in the exceptional case.
10. The method of claim 9,
wherein the processor is configured to start the timer by starting a periodic BSR-timer and a retransmission BSR-timer (retx BSR-timer).
11. The method of claim 10,
wherein the processor is configured to start the periodic BSR-timer and the retransmission BSR-timer,
stopping the periodic BSR-timer and the retransmission BSR-timer,
The terminal is to set timer values of the periodic BSR-timer and the retransmission BSR-timer to 0 (zero).
10. The method of claim 9,
The wireless transceiver is configured to receive resource selection mode information, and to change from the resource allocation mode to the resource selection mode based on the determined RLF.
10. The method of claim 9,
The processor is configured to make a decision to change from the resource allocation mode to the resource selection mode based on the determination that the exceptional case occurs,
configured to select a resource related to direct data transmission between the terminals in the exceptional case based on the resource pool information in the resource selection mode,
The exceptional case includes a case in which, as the RLF is detected, the establishment of the re-establishment procedure for the RRC connection is started, and a T311 timer related to the re-establishment procedure for the RRC connection is started. terminal.
14. The method of claim 13,
The wireless transceiver receives CommTxPoolExceptional for direct data transmission between the terminals in the exceptional case.
15. The method of claim 14,
The wireless transceiver receives the CommTxPoolExceptional through a broadcast channel from the base station,
The CommTxPoolExceptional is included in the system information block (system information block, SIB), the terminal.
A method of operating a terminal in a wireless communication system, the method comprising:
establishing a radio resource control (RRC) connection with the base station by the terminal;
Receiving configuration information including resource allocation mode information for direct data transmission between the terminal and another terminal from the base station;
triggering a buffer status report (BSR) related to direct data transmission between the terminals while the terminal operates in the resource allocation mode;
after the triggering, determining that a timer related to handover of the terminal is running; and
canceling all BSRs for direct data transmission between the terminals based on a determination that a timer related to the handover of the terminal is operating, wherein the canceled BSRs for direct data transmission between the terminals are scheduled by the base station Related to direct data transmission between terminals and the resource allocation mode,
A step of performing, by the terminal, direct data transmission between terminals in the exceptional case by selecting a resource related to direct data transmission between terminals in the exceptional case based on the information of CommTxPoolExceptional, wherein the CommTxPoolExceptional is the exceptional case Indicating resource pool information related to direct data transmission, a method.
17. The method of claim 16,
Receiving at least one of an RRC reconfiguration message or a cell change command message including mobility control information; and
Starting the timer related to handover of the terminal based on the RRC reconfiguration message or the cell change command message.
17. The method of claim 16,
determining whether the handover is complete;
stopping the timer related to the handover of the terminal based on a determination that the handover is completed;
Changing from a temporary resource selection mode to a resource allocation mode based on the stopped timer.
17. The method of claim 16,
receiving resource selection mode information; and
Changing from the resource allocation mode to the resource selection mode based on a determination that the timer related to the handover of the terminal is operating.
17. The method of claim 16,
changing from the resource allocation mode to the resource selection mode by the terminal and based on a determination that the exceptional case occurs; and
selecting the resource related to direct data transmission between terminals in the exceptional case based on the resource pool information by the terminal in the resource selection mode;
The exceptional case includes a case in which the timer related to the handover of the terminal is in operation or has been started.
17. The method of claim 16,
Receiving CommTxPoolExceptional for direct data transmission between terminals in the exceptional case;
17. The method of claim 16,
Receiving the CommTxPoolExceptional through a broadcast channel from the base station;
The CommTxPoolExceptional is included in a system information block (SIB).

Images