KR20150113777A - Method and appratus of trasmitting data in device-to-device communications - Google Patents

Abstract

The present invention provides a method for transmitting data when device-to-device (D2D) communications is performed in a wireless communications system. According to the present invention, a terminal can perform D2D data communications even when access to a base station is blocked. The method includes the steps of: sensing a trigger of random access in a sleep mode; determining whether the random access is triggered by D2D communications; and selecting a resource for D2D communications to perform the D2D communications.

Description

Field of the Invention [0001] The present invention relates to a method and apparatus for data transmission in terminal-to-terminal communication,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system and, more particularly, to a wireless communication system in a 3GPP (Third Generation Partnership Project) system (e.g., LTE (Long Term Evolution) (Hereinafter referred to as " D2D ") communication.

Recently, wireless communication technology has developed rapidly, and communication system technology has evolved accordingly. Of these, 3GPP's UMTS (Universal Mobile Telecommunications System) system is a representative third generation mobile communication technology, and 4th generation mobile communication technology The system that receives the light is an LTE system.

1 is a diagram showing a structure of the LTE system to which the present invention is applied.

Referring to FIG. 1, a radio access network of an LTE system includes an Evolved Node B (hereinafter, referred to as an ENB, a Node B or a base station) 105, a MME (Mobility Management Entity) And an S-GW 130 (Serving-Gateway). A user equipment (UE) 135 accesses the external network through the ENBs 105 to 120 and the S-GW 130.

In FIG. 1, the ENBs 105 to 120 correspond to the existing node B of the UMTS system. The ENB is connected to the UE 135 via a radio channel and plays a more complex role than the existing Node B. In the LTE system, since all user traffic including a real-time service such as Voice over IP (VoIP) over the Internet protocol is serviced through a shared channel, status information such as buffer status, available transmission power status, And the ENBs 105 to 120 take charge of the scheduling. One ENB normally controls a plurality of cells. For example, in order to realize a transmission rate of 100 Mbps, an LTE system uses Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology, for example, at a bandwidth of 20 MHz. In addition, Adaptive Modulation and Coding (AMC) scheme is used to determine a modulation scheme and a channel coding rate in accordance with a channel state of a UE. The S-GW 130 is a device for providing a data bearer, and generates or removes a data bearer under the control of the MME 145. The MME is a device that performs various control functions as well as a mobility management function for a terminal, and is connected to a plurality of base stations.

2 is a diagram illustrating a wireless protocol structure in the LTE system to which the present invention is applied.

Referring to FIG. 2, the wireless protocol of the LTE system includes Packet Data Convergence Protocols (PDCP) 205 and 240, RLC (Radio Link Control) 210 and 235, and MAC (Medium Access Control) 215 and 230 in the UE and the ENB, respectively. The PDCP (Packet Data Convergence Protocol) 205 and 240 are responsible for operations such as IP header compression / decompression and Radio Link Control (RLC) 210 and 235 are PDCP PDU ) To an appropriate size. The MACs 215 and 230 are connected to a plurality of RLC layer devices configured in a terminal, multiplex RLC PDUs into MAC PDUs, and demultiplex RLC PDUs from MAC PDUs. The physical layers 220 and 225 perform channel coding and modulation on the upper layer data, transmit them to a wireless channel by making OFDM symbols, demodulate OFDM symbols received through a wireless channel, channel-decode and transmit the OFDM symbols to an upper layer . Also, in the physical layer, HARQ (Hybrid ARQ) is used for additional error correction. In the receiving end, transmission of the packet transmitted from the transmitting end is carried out with 1 bit. This is called HARQ ACK / NACK information. The downlink HARQ ACK / NACK information for uplink transmission is transmitted through a PHICH (Physical Hybrid-ARQ Indicator Channel) physical channel, and the uplink HARQ ACK / NACK information for downlink transmission includes a Physical Uplink Control Channel (PUCCH) (Physical Uplink Shared Channel) physical channel.

At present, the data usage of users has increased due to the spread of smart phones, and mobile communication network operators provide data service to subscribers by installing the latest LTE system described above in order to cope with the explosion of data. However, the demand for data transmission still increases and the need for the development of new technologies is emerging. Accordingly, an attempt has been made to define a technology for performing a device-to-device (hereinafter referred to as D2D) communication between a terminal and a terminal without going through a base station in the current 3GPP standards body.

On the other hand, when performing D2D communication, the radio resources share the radio resources used between the existing base station and the terminal. Therefore, there are two ways to avoid this.

The first method is a method of requesting allocation of resources to a base station for data transmission in D2D communication (hereinafter, this method is referred to as 'D2D transmission first method'). That is, the base station concentrates the requests for all the radio resources and allocates all the resources to the base station. Therefore, this scheme is a scheme that can be utilized when the terminal is within the coverage of the base station, that is, the base station's signal.

FIG. 3 is an exemplary flowchart for this. In FIG. 3, the terminal 1 (301) generates data to be sent to the terminal 2 (303) (311). In this example, as described above, the terminal 1 is allocated by the base station 305 with resources for sending data to the terminal 2. Therefore, a request for resource allocation for D2D communication is made to the base station. If resources that can be transmitted to the base station have not been allocated, the terminal 1 performs a random access procedure to the base station 313 and requests resources for communication with the terminal 2 with the resources allocated thereto through the random access procedure 315. In such a case, the UE operates in a radio resource control (RRC) idle state (RRC_IDLE) in which the UE is not connected to the base station. (RRC_CONNECTED), which is connected to the base station. When a resource to be transmitted to the base station is allocated, the base station directly requests a resource for communication with the base station 2 (315).

Herein, the RRC_IDLE state may indicate a state where a connection between a base station and a radio resource control (RRC) layer is not established. In this state, the terminal and the base station can not transmit / receive unicast data with each other.

Meanwhile, the RRC_CONNECTED state may indicate that the terminal attempts to access the base station and a connection with the RRC layer is established. In this state, the terminal and the base station can transmit and receive unicast data with each other.

Meanwhile, a method of reporting the amount of data to be transmitted (buffer status report, Buffer Status Report) accumulated in the current buffer may be used as a method of requesting the resource. It is applicable both in the example. Resources for D2D communication are allocated from the base station (317), and the terminal 1 can transmit and receive data to and from the terminal 2 exclusively from the allocated resources (319).

The second scheme is to acquire the resources set for D2D communication for data transmission in the D2D communication by competing with the D2D terminals (hereinafter referred to as 'D2D transmission second scheme'). That is, the utilization of the radio resources is distributed to each D2D UEs without a center device like a base station. Unlike the first method of D2D transmission, the present method has a merit that the device structure is simple, although there is no device that is the center of resource allocation, so that a collision may occur during data transmission. Accordingly, this scheme is a scheme that can be utilized when the terminal does not reach the signal of the base station, that is, the base station is out of coverage.

Fig. 4 is an exemplary flowchart for this. In FIG. 4, the terminal 1 (401) generates data to be sent to the terminal 2 (403) (411). Thereafter, the UE performs a radio resource acquisition competition with other D2D terminals in the resource allocated for D2D communication, excluding the resources allocated for communication with the base station and the terminals among all the radio resources, (413), and transmits the data to the acquired resource (415). In the acquisition competition method, a method of detecting a current channel is empty and, if it is determined that the channel is empty, a method of starting data transmission can be used.

On the other hand, when the number of users accessing the cell becomes too large, the access point can block connection of terminals in a cell that desires to access the base station using Access Class Barring (ACB) technique. In the ACB scheme, a base station broadcasts accessibility probability information to terminals in a cell, generates a random number when a terminal attempts to access, and is disconnected when the random number is greater than the accessibility probability information Method.

On the other hand, when the ACB scheme and the D2D transmission first scheme are used at the same time, the terminal can not perform the D2D communication because the connection is blocked despite attempting to utilize resources of the D2D communication, I need a plan.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a wireless communication system in which when a D2D communication is performed in a cellular network (e.g., 4G network such as LTE) It provides a way to perform D2D communication.

The following measures are suggested as means for solving the present invention.

Example 1:

- When the random access is triggered in the sleep mode terminal,

- If the random access transmission is blocked by the ACB scheme,

- Also, if the random access has been triggered by data generation for D2D communication or by service initiation (i.e. if it is due to the D2D transmission first scheme);

o Performs the random access procedure, selects a resource for the D2D data transmission (e.g., utilizes the D2D transmission second scheme), and performs D2D data transmission

- If not;

o Perform random access to the base station after ACB blocking is terminated.

Example 2:

- When the random access is triggered in the sleep mode terminal,

- If the random access has been triggered by data generation for D2D communication or by service initiation (i.e. if it is due to the D2D transmission first scheme described above);

o D2D communication, it is determined whether or not the connection is blocked by using the ACB parameter which is separately defined and transmitted,

- If not;

o Check whether connection is blocked using existing ACB parameter,

Example 3:

- When the random access is triggered in the sleep mode terminal,

- If the random access has been triggered by data generation for D2D communication or by service initiation (i.e. if it is due to the D2D transmission first scheme)

- If the ACB technique or other reasons do not successfully perform the random access procedure for a predetermined time;

o It is regarded that the connection of the corresponding cell is barred and is not regarded as a cell (re-selection) candidate until a specific time or a specific event occurs,

o Selecting (re) another cell supporting the out-of-cell D2D to perform a random access procedure

Using the proposed method, the terminal can perform terminal-to-terminal data communication even when the access to the base station is blocked.

1 is a diagram showing the structure of an LTE system to which the present invention is applied;
2 is a diagram illustrating a wireless protocol structure in an LTE system to which the present invention is applied;
FIG. 3 is a diagram illustrating an example of a request for allocation of resources to a base station for data transmission in D2D communication.
FIG. 4 is a diagram illustrating an example of a method of acquiring resources determined for D2D communication for data transmission in D2D communication by competing D2D terminals
5 is a diagram illustrating a message flow according to the first embodiment of the D2D data transmission method proposed by the present invention.
6 is a diagram illustrating an example of the operation sequence of a terminal to which the D2D data transmission method embodiment 1 proposed by the present invention is applied
7 is a diagram illustrating a message flow according to the second embodiment of the D2D data transmission method proposed by the present invention.
FIG. 8 is a diagram illustrating an operation sequence of a terminal to which the second embodiment of the D2D data transmission method proposed by the present invention is applied
9 is a diagram illustrating a message flow according to a third embodiment of the D2D data transmission method proposed by the present invention.
10 is a diagram illustrating an operation sequence of a terminal to which the D2D data transmission method embodiment 3 proposed by the present invention is applied
11 is a diagram illustrating a message flow according to the fourth embodiment of the D2D data transmission method proposed by the present invention.
12 is a diagram illustrating an example of the operation sequence of a terminal to which the fourth embodiment of the D2D data transmission method proposed by the present invention is applied
13 is a block diagram illustrating a configuration of a terminal according to an embodiment of the present invention.
14 is a block diagram illustrating a configuration of a base station according to an embodiment of the present invention.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

For convenience of explanation, the present invention is described on the basis of an LTE system as an example of a cellular network, but can also be applied to other cellular networks (e.g., UMTS).

FIG. 5 is a diagram illustrating a message flow according to the first embodiment of the D2D data transmission method proposed by the present invention.

In the drawing, it is assumed that the terminal 1 (501) is in the aforementioned RRC sleep state and directly sends data to the second terminal (503) using D2D communication. It is also assumed that the terminal 1 is located within the coverage of the base station 505 and uses a scheme of allocating resources for D2D communication from the base station, that is, using the above-mentioned D2D transmission first scheme.

The terminal 1 (501) in the sleep mode generates data to be transmitted (511). For example, it may occur due to a call, a photograph, a file, or the like.

The UE 1 may receive the ACB parameter described above from the BS 505 before or after the data to be transmitted is generated (513). The ACB parameter may not be transmitted depending on the base station.

If the ACB parameter is transmitted from the base station 505, the terminal 1 determines whether to block the connection in the above-described manner (515). That is, the base station broadcasts the accessibility probability information and the access blocking time (ACB parameter) to the terminals in the cell, generates a random number when the terminal attempts to connect, and if the random number is larger than the accessibility probability information It is determined that the connection is blocked by the connection blocking time. In the present invention, the connection probability information comparison may be performed once after the terminal is judged to be disconnected, or the terminal may be judged to be disconnected even if it is interrupted for a predetermined number of times or for a predetermined time It can be judged that it is blocked. The predetermined number of times or a predetermined time may be transmitted by the base station together with the ACB parameter or may be a fixed value defined in the standard.

If it is determined that the connection is blocked, the terminal determines whether the data to be transmitted is data to be transmitted to the base station or generated due to data generation for D2D communication or service start (517).

If the data is to be transmitted to the base station, the data transmission is interrupted during the connection blocking time.

However, in case of data for D2D communication, although the terminal 1 is located in the coverage of the current base station, the terminal does not make a resource request to the base station in order to transmit data but transmits radio resources for D2D data transmission (519) (521), and performs D2D data transmission (523). As a method for selecting the radio resource to be transmitted by itself, a method of detecting whether there is another terminal using the current radio resource (carrier sensing) or a method of transmitting the resource allocation information for the D2D terminals transmitted by the D2D terminal, (D2D scheduling assignment information) can be utilized.

Even in the case where the terminal uses the method of selecting the radio resource to be transmitted by itself, the terminal can change the ACB parameter transmitted by the base station or change the system information broadcasted to the terminals in the cell by the base station , It is determined whether or not the access is blocked again, and a random access is performed to the base station to attempt data transmission.

In addition, when the terminal performs the random access procedure for the resource request for D2D data transmission to the base station, the random access procedure may fail or be delayed. For example, many terminals performing random access at the same time fail to succeed in the random access procedure, or may receive commands from the base station to perform connection later due to a large number of terminals. In the case of failure or delay as described above, the UE may use a method of determining whether the UE data is D2d data and selecting the radio resource to be transmitted by itself, as described above.

Meanwhile, in the above example, the UE determines whether the access is blocked or not, and then determines the data type (that is, data to be transmitted to the base station or data to be transmitted to the D2D). However, the order may be changed. That is, it is possible to first check the data type and then check whether or not the connection is blocked. If the data type is D2D data, the terminal directly selects the radio resource for D2D data transmission Method can be used.

6 is a diagram illustrating an operation sequence of a terminal to which the first embodiment of the D2D data transmission method proposed by the present invention is applied.

The terminal in the sleep mode generates data to be transmitted (601). For example, it may occur due to a call, a photograph, a file, or the like.

If there is an ACB parameter received from the base station before or after the data to be transmitted is generated (step 603), the mobile station performs a random access procedure to the base station (step 621), and transmits data to the base station (623).

However, if the received ACB parameter exists, it is determined whether the connection is blocked using the above-described method (605). As described with reference to FIG. 5, the terminal can determine whether the connection is blocked even after the connection probability information comparison is performed once or after the connection is made, or even if the connection is blocked for a predetermined number of times or for a predetermined period of time. The predetermined number of times or a predetermined time may be received from the base station together with the ACB parameter, or a fixed value defined in the specification may be used. If it determines that the connection is not blocked, the terminal performs a random access procedure to the base station (621) and may transmit data to the base station (623).

However, if it is determined that the data is blocked, the terminal determines whether the data to be transmitted is data to be transmitted to the base station or data for D2D communication (607).

If the data is to be transmitted to the base station, the data transmission is interrupted for the connection cutoff time and terminated (631).

However, if it is due to data for D2D communication, the terminal itself selects a radio resource for D2D data transmission (609) and performs D2D data transmission (611). As a method for selecting the radio resource to be transmitted by itself, a method of detecting whether there is another terminal using the current radio resource (carrier sensing) or a method of transmitting the resource allocation information for the D2D terminals transmitted by the D2D terminal, (D2D scheduling assignment information) can be utilized.

7 is a diagram illustrating a message flow according to a second embodiment of the D2D data transmission method proposed by the present invention.

In the drawing, it is assumed that the terminal 1 701 is in the above-mentioned RRC sleep state and directly sends data to the second terminal 703 using D2D communication. It is also assumed that the terminal 1 is located within the coverage of the base station 705 and uses resource allocation for D2D communication from the base station, i.e., the D2D transmission first scheme described above.

The terminal 1 701 in the sleep mode generates data to be transmitted (711). For example, it may occur due to a call, a photograph, a file, or the like.

The terminal 1 may receive ACB parameters for the D2D communication proposed in the present invention and the existing ACB parameters from the base station 705 before or after the data to be transmitted is generated (713). The ACB parameter may not be transmitted depending on the base station.

If the ACB parameter is present, the UE determines whether data to be currently transmitted is data to be transmitted to the BS or data for D2D communication (715).

If the data is transmitted to the base station, the terminal determines whether to block the connection using the existing ACB parameter.

If the data is for D2D communication, the terminal determines whether to block the connection using the ACB parameter for D2D communication proposed in the present invention (717). Accordingly, if the connection is not blocked, the terminal performs a random access procedure to the base station (719). If the random access procedure is successful, the terminal 1 requests a base station for a radio resource for communication with the terminal 2 (721). Thereafter, when a radio resource for communication with the terminal 2 is allocated to the terminal 2 (723), the terminal 1 transmits data to the terminal 2 (725).

In the above example, ACB parameters for D2D are separately described. However, other types of embodiments may also exist. In a further embodiment, for example, the base station may, in addition to the existing ACB parameter, send an indicator indicating that it is not necessary to perform a blocking check for D2D communication, instead of the ACB parameter for the proposed D2D communication . If the indicator is transmitted, the terminal can immediately perform random access without judging 717 whether or not the access is blocked.

In addition, in a further embodiment, even in the case of using only the existing ACB parameter, when the terminal uses D2D communication for public safety or the like, the terminal may change the current connection type to avoid the connection blocking procedure have. For this purpose, the UE does not use the Access Class (AC) number between 0 and 9 uniquely assigned to the UE used for transmitting the normal data, Can be used.

Further, the second embodiment and the first embodiment may be used at the same time. For example, if it is determined that the connection is not blocked through the above method of the terminal and the random access procedure is performed but the terminal fails or is delayed, the terminal determines whether the data is D2D data, A method of selecting a radio resource to be transmitted by itself may be used.

8 is a diagram illustrating an operation sequence of a terminal to which the second embodiment of the D2D data transmission method proposed by the present invention is applied.

The terminal in the sleep mode generates data to be transmitted (801). For example, it may occur due to a call, a photograph, a file, or the like.

If there is an ACB parameter received from the base station before or after the data to be transmitted is generated (step 803).

If there is no received ACB parameter, the random access procedure is performed to the base station (821), and the data can be transmitted to the base station (823).

If the received ACB parameter is present, the UE determines whether data to be currently transmitted is data to be transmitted to the base station or data for D2D communication (805).

If the data is to be transmitted to the base station, the terminal determines whether to block the connection using the existing ACB parameter (807). If the data is blocked (809), the terminal blocks the connection for the corresponding time and ends (831) If not blocked (809), a random access procedure is performed to the base station (821) and data is transmitted to the base station (823).

If the data is for D2D communication, the terminal determines whether the connection is blocked using the ACB parameter for D2D communication proposed in the present invention (811). If the data is blocked (813) (811), a random access procedure is performed to the base station (825), a random access procedure is performed to the base station to request a radio resource for D2D communication, And transmits the data to the corresponding resource (827).

FIG. 9 is a diagram illustrating a message flow according to a third embodiment of the D2D data transmission method proposed by the present invention.

In the present example, it is assumed that the terminal 1 (901) is in the RRC sleep state described above and directly sends data to the terminal 2 (903) using D2D communication. It is also assumed that the terminal 1 is located within the coverage of the base station 905 and uses a scheme of allocating resources for D2D communication from the base station, that is, using the above-mentioned D2D transmission first scheme.

The terminal 1 (901) in the sleep mode generates data to be transmitted (911). For example, it may occur due to a call, a photograph, a file, or the like.

The terminal 1 may receive the above-described ACB parameter from the base station 905 before or after the data to be transmitted is generated (913).

If the ACB parameter is received, the terminal determines whether the connection is established (915). If the ACB parameter is determined to be disconnected, the terminal determines whether the connection is blocked, A cell is selected (919), and a cell selection or cell reselection procedure is performed (919) to select another cell. The predetermined time may be transmitted by the base station together with the ACB parameter, or may use a fixed value defined in the specification. The predetermined event may be, for example, when data to be sent to the base station occurs. In addition, the cell selection or cell reselection procedure conforms to the contents of the 3GPP TS 36.304 standard.

Thereafter, the terminal selects a new cell or a base station (base station 2 (907) in this example). The base station 2 may operate at the same frequency as the base station 1 or may operate at a different frequency. If the selected base station transmits an ACB parameter (921), the terminal determines whether to block access (923). If the selected base station does not block the access, the random access procedure is performed to the base station (925) The base station requests resources for communication with the terminal 2 (927). Thereafter, when a resource for communication with the terminal 2 is allocated from the base station (929), data is transmitted to the terminal 2 (931).

10 is a diagram illustrating an operation sequence of a terminal to which the D2D data transmission method embodiment 3 proposed by the present invention is applied.

The terminal in the sleep mode generates data to be transmitted (1001). For example, it may occur due to a call, a photograph, a file, or the like.

It is determined whether the ACB parameter received from the base station exists before or after the data to be transmitted is generated (step 1003).

If the received ACB parameter does not exist, or if it is determined that the ACB parameter is present but the connection is not blocked, a random access procedure is performed to the base station (1021) and a data or resource request message can be transmitted to the base station (1023) .

However, if it is determined that the received ACB parameter exists and the connection is blocked (1005), the UE selects a cell (re-selection) for the corresponding base station for a predetermined time or until a predetermined event occurs (1007), cell selection or cell reselection is performed to select another cell (1009). The predetermined time may be transmitted by the base station together with the ACB parameter, or may use a fixed value defined in the specification. The predetermined event may be, for example, when data to be sent to the base station occurs. In addition, the cell selection or cell reselection procedure conforms to the contents of the 3GPP TS 36.304 standard.

11 is a diagram illustrating a message flow according to a fourth embodiment of the D2D data transmission method proposed by the present invention.

In this example, it is assumed that the first terminal 1101 is in the RRC sleep state or the RRC connection state and directly transmits data to the second terminal 1103 using D2D communication. It is also assumed that the terminal 1 is located within the coverage of the base station 1105 and uses a scheme of allocating resources for D2D communication from the base station, i.e., the above-mentioned D2D transmission first scheme.

The terminal 1 1101 generates data to be transmitted (1111). For example, it may occur due to a call, a photograph, a file, or the like. More specifically, the following situation may occur.

- When D2D data to be transmitted reaches the buffer (or D2D data to be transmitted is generated on a logical channel (LCH) set for D2D communication); or

- When the terminal in the RRC sleep state starts to perform the random access procedure (or starts to perform the RRC connection establishment procedure or transmits the random access preamble) when D2D data to be transmitted occurs and the random access procedure is performed; or

- When the UE in the RRC connection state generates D2D data to be transmitted and the scheduling request transmission procedure is triggered (or the corresponding scheduling request is transmitted) to transmit the generated D2D data; or

- (Or a random access preamble is transmitted) (in this case, the UE does not set a separate resource so that the UE can send a scheduling request), D2D data to be transmitted is generated by the UE in the RRC connection state,

In the above situation, the terminal starts the timer T1 (tentative name) proposed by the present invention (1113). The timer T1 may be broadcast by being included in a system information block or the like by the base station or may be set to be dedicated by using a separate RRC layer message (for example, an RRC Connection Reconfiguration message) Value can be used.

Meanwhile, the terminal 1 may receive the above-described ACB parameter from the base station 1105 before or after the data to be transmitted is generated (1115).

If the ACB parameter is received, the UE determines whether the connection is established (1117). If the ACB parameter is determined to be disconnected, the UE can not transmit a resource request message for D2D communication.

Meanwhile, if the terminal 1 can not successfully transmit a message (Buffer Status Report) indicating the buffer status of the D2D data to the base station until the timer T1 expires, the terminal 1 transmits the D2D data that caused the timer T1 to the base station If not, the terminal starts the timer T2 proposed by the present invention (1119). The timer T2 may be broadcast by being included in a system information block or the like by the base station or may be set to be dedicated by using a separate RRC layer message (for example, an RRC Connection Reconfiguration message) Value can be used.

When the timer T2 starts, although the UE 1 is located in the coverage of the current BS, the UE selects a radio resource for D2D data transmission without requesting a base station to transmit data, ) 1123 performs D2D data transmission (1125). As a method for selecting the radio resource to be transmitted by itself, a method of detecting whether there is another terminal using the current radio resource (carrier sensing) or a method of transmitting the resource allocation information for the D2D terminals transmitted by the D2D terminal, (D2D scheduling assignment information) can be utilized. The radio resource is a separately allocated resource for selecting a radio resource to be used by the mobile station as described above. The radio resource may be broadcasted by a system information block or may be dedicatedly allocated using an RRC layer message for each mobile station, Or fixed resources defined in the communication standard can be used.

The UE selects a radio resource for D2D data transmission by itself (1121) (1123) and performs D2D data transmission until the timer T2 expires (1125).

Thereafter, when the timer T2 ends and data to be transmitted by the terminal is generated 1131, the timer T1 is started in the same manner as described above (1133). When the terminal operates in the RRC sleep state, (1135) whether or not it is blocked (1137).

If the terminal 1 successfully transmits a message (Buffer Status Report) indicating the buffer status of the D2D data to the base station until the timer T1 expires 1141 or if the D2D data causing the timer T1 to start is transmitted If it is transmitted to the base station (1145), the terminal stops the timer T1 and performs D2D data communication by receiving the resource allocation from the base station using the above-mentioned D2D transmission first scheme.

12 is a diagram illustrating an example of the operation sequence of a terminal to which the fourth embodiment of the D2D data transmission method proposed by the present invention is applied.

If the UE generates data to be transmitted 1203, that is, more specifically, if the following situation occurs, the UE starts a timer T1 (1205).

- When D2D data to be transmitted reaches the buffer (or D2D data to be transmitted is generated on a logical channel (LCH) set for D2D communication); or

- When the terminal in the RRC sleep state starts to perform the random access procedure (or starts to perform the RRC connection establishment procedure or transmits the random access preamble) when D2D data to be transmitted occurs and the random access procedure is performed; or

- When the UE in the RRC connection state generates D2D data to be transmitted and the scheduling request transmission procedure is triggered (or the corresponding scheduling request is transmitted) to transmit the generated D2D data; or

- (Or a random access preamble is transmitted) (in this case, the UE does not set a separate resource so that the UE can send a scheduling request), D2D data to be transmitted is generated by the UE in the RRC connection state,

If the UE has successfully transmitted a message (Buffer Status Report) indicating the buffer status of the D2D data to the BS until the timer T1 expires, the UE transmits the D2D data that caused the timer T1 to the BS In operation 1205, the UE stops the timer T1 in operation 1207 and determines to perform D2D data communication in response to the resource allocation from the base station using the D2D transmission scheme described above in operation 1219. (1221).

On the other hand, if the UE fails to successfully transmit a message (Buffer Status Report) indicating the buffer status of the D2D data to the base station until the timer T1 expires, or transmits the D2D data that caused the timer T1 to the base station If not, the terminal starts the timer T2 proposed by the present invention (1211).

When the timer T2 starts, the terminal itself selects a radio resource for D2D data transmission (1213) without requesting a base station to transmit data, although the terminal is located in the coverage of the current base station, D2D data transmission is performed (1215). As a method for selecting the radio resource to be transmitted by itself, a method of detecting whether there is another terminal using the current radio resource (carrier sensing) or a method of transmitting the resource allocation information for the D2D terminals transmitted by the D2D terminal, (D2D scheduling assignment information) can be utilized. The radio resource is a separately allocated resource for selecting a radio resource to be used by the mobile station as described above. The radio resource may be broadcasted by a system information block or may be dedicatedly allocated using an RRC layer message for each mobile station, Or fixed resources defined in the communication standard can be used.

Thereafter, the UE selects a radio resource for D2D data transmission itself (1213) and performs D2D data transmission until the timer T2 expires (1215).

Thereafter, if the timer T2 is terminated, the procedure is terminated (1221). If the D2D data to be transmitted by the terminal occurs, the procedure is restarted (1201) to determine how to transmit the D2D data .

Through the above method, the terminal can perform the terminal-to-terminal data communication even when the access to the base station is blocked

13 is a block diagram illustrating a configuration of a terminal according to an embodiment of the present invention.

13, a terminal according to an embodiment of the present invention includes a transmitter / receiver 1305, a controller 1310, a multiplexer / demultiplexer 1320, a control message processor 1335, and an upper layer processor 1325, (1330).

The transceiver 1305 receives data and a predetermined control signal on a forward channel of a serving cell, and transmits data and a predetermined control signal on a reverse channel. When a plurality of serving cells are set, the transmitting and receiving unit 1305 performs data transmission and reception and control signal transmission and reception through the plurality of serving cells.

The multiplexing and demultiplexing unit 1320 multiplexes the data generated in the upper layer processing units 1325 and 1330 and the control message processing unit 1335 or demultiplexes the data received in the transmission and reception unit 1310 and transmits the multiplexed data to the upper layer processing unit 1325 ) 1330 and the control message processing unit 1335, respectively.

The control message processing unit 1335 processes the control message received from the base station and takes necessary actions.

The upper layer processing units 1325 and 1330 may be configured for each service and may process data generated in user services such as FTP (File Transfer Protocol) and VoIP (Voice over Internet Protocol) Or processes the data transmitted from the multiplexing and demultiplexing unit 1315 and transfers the processed data to a service application of an upper layer.

The control unit 1310 checks the scheduling command, for example, the uplink resource allocation information received through the transmission / reception unit 1305, and multiplexes the uplink resource allocation information with the transmission / reception unit 1305 so that uplink transmission is performed at an appropriate time, And controls the multiplexing unit 1315.

In the present invention, when the data to be transmitted is received from the upper layer devices 1325 and 1330, the terminal in the sleep mode determines whether or not the connection is blocked from the control message processor 1335, Accordingly, the connection method is changed, connection determination is performed, or another cell is selected or reselected by using the method described in the above-described first, second, or third embodiment.

14 is a block diagram showing the configuration of a base station according to an embodiment of the present invention. The base station apparatus of FIG. 14 includes a transmitting and receiving unit 1405, a control unit 1410, a multiplexing and demultiplexing unit 1420, a control message processing unit 1435 ), Upper layer processing units 1425 and 1430, and a scheduler 1415.

The transmission / reception unit 1405 transmits data and a predetermined control signal to the downlink carrier wave, and receives data and a predetermined control signal on the uplink carrier wave. When a plurality of carriers are set, the transmission / reception unit 1405 performs data transmission / reception and control signal transmission / reception with the plurality of carriers.

The multiplexing and demultiplexing unit 1420 multiplexes data generated in the upper layer processing units 1425 and 1430 or the control message processing unit 1435 or demultiplexes the data received in the transmission and reception unit 1405 and transmits the multiplexed data to an appropriate upper layer processing unit 1425 ) 1430, the control message processing unit 1435, or the control unit 1410. The control message processing unit 1435 processes the control message transmitted by the mobile station to perform a necessary operation or generates a control message to be transmitted to the mobile station and transmits the generated control message to the lower layer.

The upper layer processing units 1425 and 1430 may be configured for each service according to each terminal and may process data generated in a user service such as FTP and VoIP and transmit the processed data to a multiplexing and demultiplexing unit 1420 or a multiplexing and demultiplexing unit 1420 and transfers the processed data to the service application of the higher layer.

The control unit 1410 determines when the terminal should transmit channel state information and controls the transmission / reception unit.

The scheduler 1415 allocates transmission resources to the mobile station at an appropriate point in consideration of the buffer state of the mobile station, the channel state, and the activity time of the mobile station, processes the signal transmitted from the mobile station to the transmission / do.

In the present invention, the base station generates an ACB parameter for D2D communication proposed by the present invention or an indicator for allowing connection without performing an ACB check for D2D communication in the control message processor 1435 And broadcasts it to the terminals in the cell so as to inform the terminal that the terminal can change the connection mode, determine the connection blocking, or select or reselect the cell.

Using the proposed method, the terminal can perform terminal-to-terminal data communication even when the access to the base station is blocked.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the scope of the appended claims, and equivalents thereof.

Claims (2)

A method of supporting terminal-to-terminal (Device to Device) communication in a wireless communication system,
In a sleep mode, sensing a trigger of random access;
Determining if the random access is triggered by D2D communication if the random access transmission is interrupted by a connection type block; And
And stopping the random access procedure when the random access is triggered by the D2D communication, and performing D2D communication by selecting a resource for the D2D communication.
A terminal supporting device-to-device communication in a wireless communication system,
A transmitting and receiving unit for transmitting and receiving signals to and from a base station or a terminal; And
Detecting a trigger of random access in a sleep mode and determining if the random access is triggered by D2D communication if the random access transmission is interrupted by a connection type block and if the random access is triggered by D2D communication, And a controller for stopping the random access procedure and controlling the D2D communication by selecting a resource for the D2D communication.

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